MagazineEDITOR: BERNARD EJONES TECHNICAL EDITOR: J.H.REYNER,B.sc.(mves)A.m./F.e.

OUTDOOR WIRELESS11111111,1111111111111

FOR ALL

- I Wireless Magazine. May. 1928

000.00_00000000000000000-00.000004900000000000-0000.00

BLUEPRINTS OFFAVOURITE CIRCUITS

Full-size blueprints, each one being a photographic contact print, from the draughtsman'soriginal design, and produced on stout paper, are now available of the following sets :

ONE -VALVE SETS

o.One-valver for Frame Aerial .. W.M. 4tAlpha One .. W.M.26Hartley DX One-valver A.W. 27One -valve All -wave Reinartz . A.W. 2All -in -all One-valver A.W. 13Reinartz Plug-in One-valver A.W. 46Constant -coupled One A.W. 65Long Range Hartley One .. W.M .54The Dynaflex (One-valver) A.W. 69Economy One A.W. 71Loud -speaker Special One A.W. 78 1

Reflexed One for the Loud-speaker .. . . . W .M .66 1

TWO -VALVE SETSWide World Short-wave Two A.W. ttAll -wave Two-valver A.W. 15Reinartz Two A.W. 21One -dial Two . . W.M .23Empire Short-wave Two .. A.W. 28" Next -step " Receiver .. A.W. 34t Girdle Two , W.M.3oCentre -tap Two A.W. 42Mains -fed Two W.M.37Three -option Two .. A.W. 51British Broadcast Two W M .44Rover Two .. A.W. 53All -wave TwoGeneral Purpose Two A.W. 55" Yule " Two .. A.W. 593os. Two-valver A.W. 61Economical Two .. A.W. 66Two-ptogramme Two . . W.M .56Britain's Favourite Two and

copy "A.W." A.W. 74Home and Abroad Two .. A.W.

837Two -wave TwoQ -coil Two - W.M.62tAll-broadcast Two .. W.M. 5 1Two-valver embodying KL1

ValvesOne -control Two .. A.W. 6Safeguard TwotLoftin-White Two .. . W.M. 20Remote -control Two A.W. 23Ultra -selective Hartley Two .. A.W. 90Trapped Reinartz 'two A A% . 92Oceanic Short-wave Two . . 91*Flat -dweller's Two W.M.* Crusader Two .. W.M. 69

. THREE -VALVE SETSOne -knob Three W.M. 3 1

Shielded Searcher .. W.M. 8 1

Regulator Three .. A.W. 12 1

Lighthouse Three .. A.W. 29 1

Continental Three .. W.M. 7 1

Victory Three .. A.W. 9 1+Hi -mu R.C. Three .. 1

M.C. Three Star .. A.W. 16 1

Wave -catcher Three .. 1

Split -primary Three .. A.W. 24 1

Purity Three-valver A.W'. 33 1

Modem Tuned Anode Three A.W. 35 1

'1'etrode-three for ShieldedValves A.W. 36 1

Alternative -programme Three A.W. 38 1

' Mains " T'hree-valver W.M.34 1

Screened -grid Three .. W.M.21 1

" Simpler Wireless " All -from -the -Mains Receiver A.W. 41 1

" Simpler Wireless " SpecialThree-valver 1

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No. 5." Home Station " Three .. A.W. 45 1

Five -guinea Three .. W.M.29 1" Dominions " Short-wave

Three . W.M.39" Economy "T;hree A.W. 48Short-wave Three A.W. 5oEther Searcher Three.. .. A.W. 52Tuned -Anode Three-from the

Mains (D.C.) W.M.43Three Continent Three .. A.W. 54Standard Three A.W. 56Screened -grid Short -waver .. W.M.51Hartley DX Three .. A.W. 63Britain's Favourite Three and

copy " A.W."Straight Line 'Phree .Metropolitan Three ..Everyday Three ..Music CharmerBroadcast Three ..Ridley Short-wave ThreeSelectus Three" Q " Coil Three ..Britannia Three ..Clarion Three ..Broadcast 'PhreeRidley Short-wave ThreeSelectus Three

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A.W. 72A.W. 6oW.M .48W.M.52W.M.6oA.W. 76A.W. 8oA.W. 8tA.W. 84W.M.67A.W. 88A.W. 76A.W. SoA.W. 81

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THREE -FOUR -VALVE SETSTuned -anode Three-four . A.W. 49Concord Three-four .. W.M.45Trapped Three-four .. W.M.61

FOUR -VALVE SETSDistance GetterDX FourM.C. Four .. ..Household Four .. .

Rev-tation Four .."A.', J." Gramo RadioAll-purpose Four ..All -wave Roberts Four, and

copy of " A.W."Simplicity FourC.T. Four .." Simpler " Wireless Four ..Astral Four ..Station -finder Four ..I.H.C. Four .

*Gramo-radio Four ..*"Q" Coil Four ..

A.W.A.W. 18A.W. 8A.W. 17W.M.z4A.W. 40A.W. 43

A.W. 47WM49A.W. 58A.W. 7oW.M.53W.M.68A.W. 8.7W.M. 70W.M.

FIVE -VALVE SETS1927 Five .. W.M. 6Two-volter's Five .. W.M.11Individual Five A.W. 25Exhibition FivePhoenix Five . W.M.4.21928 Five .. W.M.46All -the -world Five .. W.M.63The School Five .. A.W. 8.1

SIX -VALVE SETSNomad Six . . . . W.M.31Shoi .-wave Super -Six A.W. 67

SEVEN -VALVE SETSSimpladyne Seven (Super -het) W.M.22,

AMPLIFIERSAll -broadcast Amplifier ..Range Extender (H.F. amplify-

ing unit) .. W.M.38

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Price,past free

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W.M.16W.M.3zW.MA.W. 68A.W. 5A.W. 79A.W. 8zAAV. 86

PORTABLE SETSSpringtime Portable (two-val-

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valver)Table (,rand (Four-valver)*The Sunshine Portable ..

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CRYSTAL SETSCrystal Set for the R.C. Enthu-

siast ..Hi -lo Crystal Set ..Fonotrol Crystal Set ..Two -programme Crystal Set..Alternative -programme Crystal

Set ..Half-hour Crystal SetCentre -Tap Crystal Set ..Super Crystal Receiver ..'l'apped-coil Crystal Set ..

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MISCELLANEOUStLoud-speaker Tone Control

and Filter Unit .. W.M. t 1 3Heterodyne Wavemeter A.W. 7 1 0Made -to -measure Wave Trap A.W. 19 0 6New Current Supply Idea .. A.W. z6 1 0DX One Valve Unit .. A.W. 37 1 0Battery Eliminator for A.C.

Mains W.M.41 1 0Battery Eliminator for D.C.

Mains W.M.59 1 0Volume Control Unit .. W.M.4o 0 6" Simpler Wireless "Rectifying

Unit -H.T. Supply from A.C. MainsA.C. Mains Adaptor (for any

" Simpler Wireless " Set) .. W.M.57 1 0Cone Loud -speaker .. W.M.55 1 0Moving -coil Loud -speaker .. W.M 58 1 0Emission Tester and Parallel -

valve Unit .. W.M.65 1 0Simple Wavetrap W.M.64 1 0'Prue -tone Filter Unit A.W. 94. 1 0*Portable Cone Loud-

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A.W. 62 1 0A.W. 73 1 0

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Wireless Magazine. May. 192]

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Wireless Magazine, May 1928!

The

Best

Wireless

Weekly

BECAUSE you like the WIRELESS MAGAZINEfor its expert detailed constructional articlesand the many interesting phases of wireless

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Take "Amateur Wireless" D.each week and get the Everybest results from your set Thursday

290

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Wireless Magazine, May /928

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291

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{_Wireless Magazine. may, 1928

Build this two -valveamplifier with

You can build a 2 -valve amplifier-to give perfect loud-speaker results in conjunction with your present crystalor 1 -valve set-at a cost at only about r 8s. 6d. The partsrequired for a conventional 2 -amplifier are as under: LISSIN

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19/-1 Ebonite Panel, size about r x 6- x 1/4" . 4/-1 Eboaile Terminal Strip, about 5' x 2" x 1/4' - . 1/-1 Baseboard (from your local joiner), 8' x 6" x 3,16" - /6Screws, Terminals and Wire - - about 4/ -

Total cost (except valves and batteries) - - 28/6

10,000 radio dealers will sell you all these parts at theprices stated.No matter what may be specified in any circuit orinstructions you are building to, use LISSEN partswherever you can. Your radio dealer will also willinglytell you how to connect everycircuit you are interested inif you tell him you intend touse LISSEN parts and buythem from him.

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Managing Director IThos. N. Cole

Write to advertisers for particulars of their goods and mention the " Wireless Magazine."292

Vol. VII. No. 40. Wireless MagazineCONTENTS

May, 1928

The Sunshine Five. A ReallyPAGE

Half-hours with the Professor-PAGE

You Must Not Starve YourPAGE

Portable Set. Designed by A Chat on Purity .. .. 327 Anodes ! 357J. H. Reyner, B.Sc., A.M.I.E.E . 294 The Artifice that Met with III - Is It Over -charged? 357

Thirty Years Before Marconi? 299 success. By J. Godchaux A Forecast. Verse .. 357Continental " Radioed " English 302 Abrahams .. 330 Broadcast Music of the Month .. 358Under My Aerial. Halyard's How a Modern Valve is Made. Railway Broadcasting ! 360

Chat on the Month's Topics 303 By R. W. Hallows .. .. 331 Wireless for Women 361

The Q -coil Four. Covers Both Pressing the Crystal for Good A Wireless Phantasy 361

Wavelength Bands Without Results .. 334 Counterpoise Fallacies .. 361

Changing Coils .. 306 Preparing a Broadcast. By Frank How We Shall Arrange Contro-Mass (Re) Production ! 310 Rogers .. , . .. 335 versial Broadcasts. By B.B.C.

Your Valve Filam:ntDo We Want to Hear Parlia-

ment? By James P. Gardner,M.P. ..

Electrify Your Gramophone !Some of the Best Pick-ups ..What Readers Think of Our

Sets ..Getting More Power from the

Power Valve. By Capt. H. J.Round. M.I.E.E.

Do We Need Specialised Broad-casts? ..

311

312314315

316

318

321

The Gramo - Radio Four.Wireless or Gramophone Re-production at Will .. ..

Radio Religion Throughout theWorld ..

Is a Moving -coil Loud -speakerWorth While? ..

The Mast that Failed .. ..Can You Get Sharp Tuning? ..Don't Waste Your Obsolete

Apparatus I ..Why Not Build Your Own Loud-

speaker? ..The Flat -dweller's Two. Com-

337

341

342344345

346

347

Officials ..Clapham-and Not Dwyer ..An Idea for the Post Office ..Is There Eternity in the Ether?Some Recent Broadcasters ..New Sets and Apparatus Tested.

By Our Technical Editor ..The World's Broadcasting ..Are You Building the Music

Charmer? .. ..A Portable Cone Loud-

speaker. Weighs only 511b.The Vogt Electrostatic Loud-

speaker.. ..

362363363364364

366370

370

372

381Some Radio " Bugs 321 prises a Neutralised H.F. Test Report of the Crusader .. 381The Crusader. A Two-valver Stage and Detector .. .. 348 Reference Sheets. By J. H.

that Can be Built for £2 15s. 322 An Interesting Short-wave Ex- Reyner, B.Sc., A.M.I.E.E. .. 382Is Your Waverneter Accurate? 326 periment. By 5YM .. 352 Catalogues and Pamphlets Re-Are Mains -operated Receivers Continental Radio. By Jay Coote 354 ceived .. .. 384

Risky? .. 326 How to Polish Your Cabinets .. 356 Index to Advertisers .. .. 384Published by BERNARD JONES PUBLICATIONS LTD.,Pub.'ishers of " Wireless Magazine" and " Amateur Wirele,s."Editor: Bernard E. Yozes. Technical Editor: y. H. Reyner, B.Sc.(Hons.) A .M.I.E.E. Editorial and Advertisement Offices: 58161,Fetter Lane, London, E.C.4. Telephone: City 3733, 3734.

Telegrams: " Bejapee, Fleet, London." Published about the 25thday of the month and bears the date of the month fclicroing.Subscription: Great Britain and Abroad, 15s. 6d. a year, postfree (Canada only, s3s. 6d.). Contributions are invited and willbe promptly considered.

THE EDITOR COMMENTS FOR THE READER

Ti

.:-LE demand for a first-rate portable set has been moreinsistent this spring than ever I have known it before, andn offering in this issue Mr. Reyner's Sunshine Five I know

I am going a long way towards meeting the need. I am rathercritical of portables, and I took home Mr. Reyner's set for theweek -end expecting what I always inwardly label as a " portable "result. But I didn't get it !

In a village over a score of miles out of London, on the south-west side, 5GB filled the room and 5XX filled the house-a smallhouse, of course-the sort an editor can afford. The SunshineFive looks good, is well arranged, its circuit and components areunusual, the tone quality is satisfactory, and I believe that it willcreate great interest.

This month sees the introduction of " New Sets and ApparatusTested" in the place of " Novelties and New Apparatus," andfrom this you may definitely conclude that our future policy is togive attention to manufactured sets as well as those of our owndesigning.

We are illustrating these test reports with informative photo-graphs especially prepared by ourselves, and our notes will relateto both the performance of the sets and the method of use.

With regard to controversial broadcasting, on which in pastmonths we have had much to say, we are now able to explain, onthe authority of the B.B.C., exactly how they will arrange theircontroversial broadcasts, and in addition we present an article bya Labour M.P. giving his views-well-considered and brightlyexpressed-on the very vexed question of the broadcasting ofParliamentary debates.

In "Amateur Wireless" a week or so ago (No. 305) I published

a remarkable article entitled " Television Forty Years Ago," inwhich it was shown how Nipkow, a German inventor, had antici-pated many of the details of Mr. Baird's system of television.Now, in this issue of WIRELESS MAGAZINE, I give what I considerto be a still more extraordinary instance of anticipation.

It appears that Mahlon Loomis, an American, communicatedin 1865 over a distance of about fourteen miles without the use ofinter -connecting wires, the whole of the energy required beingcollected from the atmosphere by means of kites. It is, I suppose,safe to surmise that in both these cases the inventors would havegone far had there been available at that day even a fraction of theadvanced scientific electrical knowledge we now enjoy.

I think everybody will read " Thirty Years Before Marconi ? "with genuine admiration for a pioneer who did so much, but whosename has hitherto occupied so small a place in the history of wire-less science. Loomis died in poverty.

Special attention is being paid in this issue to the electricalgramophone, there being a constructional article on the Grarno-Radio Four, and, in addition, an article entitled " Electrify YourGramophone ! " which is illustrated with photographs of some ofthe best known " pick-ups " available.

" Is a Moving -coil Loud -speaker Worth While ? " is the questionset forth by the title of an article which raises points which willcertainly give the reader much food for thought, while the articlewill in itself act as an introduction to next month's special issue, inwhich the moving -coil loud -speaker will be very specially considered.

Instructions for building a really good instrument of this typewill be given, and the whole subject, in which such great interest icbeing taken at the moment, will be explored. THE EDITOR.

Registered at the General Post Office for transmission Cana.:ian Nl agaz.,ne Po.,

293

Wireless Magazine. May 1928

Nobody who wants a really good portable receiver-portable in every sense of the word-can do better than build that described in this article. It is the product of months of care-ful research work and will do everything that is claimed for it- as constructors can easily

prove for themselves!

A REALLY PORTABLE.FIVE-VALVER: DeGNED.AsBUILT AND TESTID BY

J.ICREYNER,B.scoi.,,sDURING the past six months, I

have been giving a great dealof attention to the problem of

C.

Suitshi

and some of the principal manufac-tured portable receivers were ex-amined during this initial period.

RE ACTiO5

0.7*S. EVALVE, Mr. UNIT

()a5

00015-.0005 ME

RITE..tITIOME,11.11.

r1T+2..

111-1-1

HGBtGB -I

GB -a

1-0- LT4o 0--

. LT-0005The Circuit of the Sunshine Five. That part enclosed by adouble dotted line comprises the special H.F. coupling unit

the portable receiver. In fact, myattention was directed to the subjecteven earlier than that, for, last July,I took the Countryside Four with meon a tour in Scotland in order to seewhat was possible in the way of moreor less portable reception.

What Is RequiredThis naturally gave me useful

information regarding what wasrequired. The matter was droppedduring the autumn, but some sixmonths ago I began to investigatethe design of portable receivers again

The requirements cons dered de-sirable for a portable set were thendrawn up, the chief features being asfollows :

.-The receiver to be completelyself-contained. This means that theframe, loud -speaker and all batteriesmust be included in the cabinet.

2.-Only one tuning control.3.-Long and short waves both

receivable, preferably without anycoil changing.

4.-Real portability, involving lowH.T. current consumption.

The last two factors are the ones

294

which caused the greatest trouble inthe design. Gang -control circuitscan be ruled out as militating againstsimplicity and compactness, whichmeans that some form of aperiodiccoupling must be adopted.

Avoiding Coil ChangingIf there is to be no coil changing

then either two sets of transformersmust be used, one for each wavelength,the connections being changed overby means of a switch, or alterhativelya system must be adopted which

i.A1111111111115 OligarDetails of the frame aerial

covers both broadcast wavebands.Numerous tests were made on the

various forms of apparatus and it was

ultimately decided toutilise the Polar H.F.unit. This is a com-pact unit, giving twostages of aperiodicH.F. amplification,which covers thewhole band from 25oto 2,000 metres.

The unit is madeup in a small box,ready wired and in-corporating a stabilis-ing adjustment whichovercomes one of thechief difficulties withthis method. Ourexperiments indicatethat any really effi-cient form of amplifi-cation, even if of theaperiodic type, wasliable to oscillate un-less some form ofstabilising was adop-ted. This has been done in the casein question, the result being a neatunit capable of giving real amplifica-tion over the full band of wavelengthsrequired.

The amplification is a little lessthan could be obtained by the use ofspecial transformers for the two wave-bands, but the greater convenience

Frame aerial andcone loud -speakerunit ready to place in lid of cabinetof having one unit to do thewhole work was consideredto outweigh this.

This left the fourth ques-tion to be settled, that of

Thecabinet

295

Wireless Magazine. may 1928

Above is a viewof the SunshineFive completed

and ready foruse

The SunshineFive assemble 1

flap at the front of thecan be liftel up

the portability, and here I have givenno little thought to the matter. Por-tability means small size and this atonce limits the area of frame aerialpermissible. A large number of experiments were done with circuitsof various types using a number odifferent frame aerial systems, andone is driven to the conclusion that acertain amount of efficiency mustinevitably be sacrificed for compact-ness.

The present portable receiver asfinally designed measures only

14 in. by 12 in. by 8 y2 in. overall,and as its weight is only 21 lb. it canbe considered really portable. Atthe same time, the frame size is verysmall and particular trouble has tobe taken to design the most efficienttype of frame aerial system for thelimited space.

Six Stations In DaylightThe result has been a receiver

capable of receiving, at Elstree, aboutsix stations in daylight and rathermore than double this number afterdark. The majority of the stationsare naturally received on the longwaves, ',here the effect of darkness

Wireless Magazine. may. 1928

The Sunshine Five (Continued)

ReceiverUnit of

theSunshine

Five

- CUT OUT TOCLEAR COMITROL

05 eUln,

Details of wood top for cabinet

On the extreme left canbe seen the special high -frequency amplifyingunit, on top of which isthe small potentiometer

is not so marked, and I feltthat the probability was thata receiver of this nature wouldenable one or two programmesto be received in all exceptthe most outlying districts ofthe country.

The actual stations re-ceived are listed in the testreport accompanying thisarticle and my experimentsindicate that this is, withoutdoubt, the best performancewhich can be obtained with astraight five-valver of thesmall size of the presentinstrument.

The circuit is shown onpage 294, and, is in the main,straightforward. There aretwo H.F. stages, incorporated

A view of the receiving unit removed from the cabinet

2%

in the unit already referred to, adetector and two transformer -coupledlow -frequency stages.

Shielded L.F. TransformersMullard transformers have been

used, since these are exceedingly com-pact and are enclosed in a metal casewhich can be earthed, thereby avoid-ing any interaction. An H.F. stopper,consistingof a resistanceof 1/4 megohrn ,is included in the grid leak to the firstL.F. valve; this is distinctly benefi-cial in avoiding H.F. in the L.F. stages

COMPONENTS REQUIRED-E bon it e panel, 9 in. by 53/4 in.

(Becol, Ebonart, or WillDay).

I-.0005-microfarad variable con-denser (Formo 1928 Log orPeerless).

1-.0005-microfarad semi -fixed con-denser (Formoclenser or Igran-ic Pre-set).

1-Double-pole change -over switch(Burndept, Dubilier, or Eric-sson).

1-High-frequency coupling unit(Polar).

3-Antimicrophonic valve -holders(Redferns, Lotus, Benjaminor W.B.).

2-Low - frequency transformers(Mullard).

1-Neutralising condenser (Gam-brell).

I-.0003-microfarad fixed conden-ser, upright type (T.C.C. typeS.P., Dubilier, or Lissen).

1-2-megohm grid leak (Dubilier,Mullard, or Lissen).

r-.25-megohm grid leak (Dubilier,Mullard or Lissen).

5-Wander plugs, 2 red and 3 black(Igranic, or Lectro Linx).

4-2 ft. lengths insulated wire(Glazite).

r -Six -way battery cord, 18 in. long,made up with pieces of flex(Lewcos).

4 oz. No. 22 -gauge d.s.c. wire(Lewcos).

3,2 -lb. No. 28 -gauge d.s.c. wire(Lewcos).

1-Cabinet (Camco).1-Loud-speaker unit complete with

cone and frame (Six -sixty).i-ioo-volt high-tension battery

with grid -bias tappings(Ripault) or oo-volt batterywithout grid -bias tappingsand 9 -volt grid -bias battery(Lissen).

1 -2 -volt unspillable accumulator(Oldham SMV4).

LWireless Magazine. may, 1928

Complete With Batteries and Loud -speaker Weighs 21 Lb.

How Reaction Is ObtainedReaction is obtained by the con-

nection of a small capacity, providedby a Gambrell Neutrovemia, fromthe anode of the detector valve backto the first grid. The remainder of thehigh -frequency current is by-passedthrough a condenser running fromthe anode to earth. This condenseris about .0003-microfarad, but ismade adjustable, a .0005-microfaradFormo-densor being used for thepurpose, since its value has someeffect on the reaction control. It isadjusted, when the receiver is com-plete, until the Neutrovemia givesreaction over the full range withoutany trouble.

Another viewof the receiv-er unit of theSunshine Five

14, DIA . EBONITE, RODava" LortG

MINIM

8YARD5 11'45ELM%

TAP AT 2 YARD5

Details of the potentiometers

Another point of interest isthat in order to obtain reallysmooth reaction a fixed poten-tiometer has been connectedacross the filament of thedetector valve and the gridleak is taken to a point on thispotentiometer. Details as tohow to wind this potentio-meter are given later on.

the top of thereceiver unit

Details of cut-out front for loud -speaker in lid

297

This receiverhas only onetuning controland covers bothupper andlower wave-length bandsby means of asingle switch

A particular feature of thecircuit is that the H.T. con-sumption is quite small, owingto the form of H.F. couplingadopted. Actually the measuredconsumption during the testswas a little less than ro-milli-amperes, which is a reasonablevalue even for a small -sizeH.T. battery.

Since such a long period hasbeen spent in the developmentof this receiver, I do not thinkthat any reader will havedifficulty in duplicating theresults obtained. The vitalportion of the whole receiveris the high -frequency endwhich is already taken care ofby the use of the H.F. unit.

Use of Specifiel PartsAt the same time, owing to the

very limited space available, it isclear that in this case the use of thespecified components must be ad-hered to for the simple reason that,in the majority of cases, other com-ponents will occupy too much space !

Leakage of high -frequency energythrough the L.F. stage is a prevalentsource of trouble in portable setsand care has been taken in the pre-sent instance to avoid this. This isagain another reason for the adoptionof the specified layout and com-ponents, for if high - frequency

Wireless Magazine, May 1928

The Sunshine Five (Continued)

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This layout and wiring diagram can be obtained as a full-size blueprintfor half-price, that is 9d post free, if the coupon on page iii of the cover

is used before May 31currents are allowed into the L.F.stages, trouble will arise due towhistling and such -like causes.

With these fewgeneral comments wecan pass to the de-tails of the actualconstruction.

CabinetThe principal fea-

ture, of course, is thecabinet, and completedetails of this aregiven herewith. Thecabinet actually usedfor my model wassupplied by the Car-rington Manufactur-ing Co., and wasfinished in oak. Themain body of thecabinet contains thebatteries and the setitself, while the lidcontains the loud-speaker and the frameaerial.

The batteries al -

use of a Lissen battery, which isslightly larger than the usual smalldry battery, so that almost any make

Test Report onSunshine Five

Station.

NewcastleLondonStuttgartHamburgLangenbergDaventry JuniorHilversum ...

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* Daylight Reception.

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of this sort, but there is ample spacefor an additional grid -bias battery ifthe operator so desires.

The loud -speaker

The receiver unit,low - tension andhigh-tension bat.teries are housedin the body of thecabinet, while theloud -speaker andframe aerial areaccommodates in

the lid ACCUMULATORCOMPARTMENT

W. INSIDEDEPTH

ONWoR

RECESS FORLOUD-5PtAttER

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RE.CENERCOMPARTMENT

HT -BATTORYopies.amot

Details of cabinetfor the Sunshine

Five

lowed for are an Old-ham type SMV4 unspillableaccumulator and a Ripault zoo -voltbattery. The actual size allows of the

2 -Volt can be employed. The use of abattery having grid -bias tappingsincorporated is convenient in a case

298

ally to thereceiver.

(Continued on page 376).

is an important com-ponent, and in thisinstance I have useda cone loud -speakersupplied by the Elec-tron Company(makers of Six -Sixtyvalves). This is madeup as a complete unit,ready for fixing be-hind the grille, sothat no further diffi-culty is experienced.

Home-made UnitAny reader who

wishes to utilise hisown unit and makeup a cone of somesort can, of course,do so if he desires,but this particularunit is most sensitiveand of pleasing repro-duction, a fact whichcontributes materi-

performance of the

Wireless Magazine, May 1928]

What a Little-known Pioneer of Radio Accomplished : Life and Work of Dr. Mahlon Loomi

THIRRYEARS bEFOKE MARCONI?FOREWORD

NO idea is ever completely new and no single effort of man is completelydetached from the work of others. Thus to attempt to appertion the praisefor the " invention " of even elementary radio would probably eventually

bring us face to face with the necessity of including in our roll of honour manyhundreds or even thousands of names whose owners' connection with radio isextremely remote, although vital.

The thoughts of man, wandering amidst the amazing phenomena by whichhe is surrounded, have been focussed upon the particular phenomena connectedwith the transmission and detection of electro-magnetic waves by the genius ofBranly, Hertz, Lodge, Marconi and many others.

But to claim for these great scientists more than they have accomplished or toallow the true perspective of their accomplishments to be lost would tend rather todiminish the historic value of their life -work than otherwise.

This somewhat lengthy preamble has as its raison d'etre the desire on thewriter's part to allay any suspicions as to his object in setting forth the followinghistory of a pioneer of radio science.

I have no reason, nor any desire, to set up claims, or to support the claimsof others who for any purpose might wish to make unfounded claims, nor wouldI wish, even if- .1 could (and it would be sheer egotism to believe that I could),undermine the reputations of those who have given their best for the science ofradio.

Some few weeks ago I mentioned the subfea of the following article to a man of very high standing in the British radio world. His comment was to theeffect that he considered the whole affair "just another instance of Americawishing to claim priority in another field for herself."

Such an accusation is not only unmerited, but it is entirely disproven by therecords 1 have seen of Dr. Loomis's early struggles. T.iese records, in fact,prove that Americans of half a estuary ago were but little more open to theacceptance of brand new ideas than their British cousins are sometimes accusedof being even to -day.

PERSONAL NOTEWhilst living in Washington, D.C., some little time ago, I was fortunate

enough to meet Dr. Harris Rogers, of Hyattsville, Md., who is well knownin radio circles e' the inventor of a system for the subterranean and submarinetransmission an, eception of electro-magnetic waves.

The venerable inventor was kind enough to allow me to inspect his under-ground antennce consisting of cast-iron pipes radiating from a central point andcontaining, though insulated from them, the actual antenna wires.

Dr. Rogers chanced to mention that his attention was first drawn to thepossibilities of radio communication by a Washington dentist, Dr. MahlonLoomis, whom he had met whilst Loomis was engaged on his experimerts.

Dr. Rogers candidly admitted to me that Loomis gave him his first ideasas to underground and underwater wireless communication. In fact, he haswritten as follows :-

" It was my pleasure to know Dr. Loomis in the early days when he wastrying to convince a sceptical world of his new and wonderful discovery. Soimpressed was 1, that I went to Professor Joseph Henry*, then at the SmithsonianInstitution, and unfolded to him Dr. Loomis's plans. Professor Henry wasunconvinced. ' It can't be done,' he is reported to have said."

After having heard from so eminent and so obviously sincere a person as(*Immortalised by the use of his name as the unit of inductance.)

DOCTOR MAHLON LOOMISwas born at Oppenheim, New

York, on July 21, 1826. He came of'a line of stern New Englanders, whoseancestors had left the now quietrural scenes of Braintree. Essex, some30o years ago, when the minds of menwere troubled with religious persecu-tion and political oppression.

Whilst still a young man, Loomismoved to Virginia with his family,and shortly afterwards commencedto study dentistry in Cleveland, Ohio.

School Teacher and DentistHe afterwards became a school

teacher in the same State, and duringthe holidays often made fifty dollarsa month by travelling the neighbour-hood in the capacity of an itinerantdentist. Later he practised dentistryin Philadelphia and at Cambridge,Massachusetts. Even whilst engaged

By FRANCIS J. MOTT

DR. MAHLON LOOMISDr. Rogers I immediately set myself to discover as much as possible about thisneglected genius, his life -work and the measure of his greatness.

The details as set forth hereunder constitute as complete a description of thisremarkable personality and his activities as it is possible for me to compress frommy copious notes into the space at my disposal.

in the prosaic calling of a dentist theinventor in him came uppermost, foron May 2, 1854, he obtained a patentfor false teeth, consisting of a gutta-percha plate with the teeth embedded.Loomis also obtained a British patent.

In 1856 Loomis married and shortlyafterwards went to live in theAmerican Federal capital.

It is not improbable that theLoomis finances were often in a sadway, as his extremely inventive turnof mind continually led him intoexperimental undertakings whichwere by no means cheap to finance.Among his experiments may be men-tioned an attempt to improve horti-culture by burying electric wires inhis garden, thus keeping the soil toan even temperature (an experimnetwhich has been repeated by otherson a large scale in recent years) ; alsothe construction of balloons with

299

heavy coatings of gold paint devisedto collect electricity from the upperatmosphere.

It is thought that the greater partof his earnings from the dental pro-fession were allocated to the financingof these and similar schemes.

Messages Without Wires in 1865!At what juncture Loomis first

bethought him of the possibilities ofradio communication it is not easy todiscover, although it is certain that

in 1865 he sent intelligiblemessages between Mountr,Cochoctin and Beorse Deer inVirginia-a distance of aboutfourteen miles -without the useof interconnecting wires.In these early experiments he

employed no " artificial " power, butcollected the required energy fromthe upper strata of the atmosphere by

[Wireless Magazine. May, 1928

Thirty Years Before Marconi ? (Continued)

UNITED STATES PATENT OFFICE.

MAHLON LOOMIS, OF WASHINGTON, DISTRICT OF COLUMBIA.

IMPROVEMENT IN TELEGRAPHING

Specification forming put of Loftus Patent No. 199,971, dated July 30, 1872.

To all whose it may concern:Be it, known that I, MARLON LOOMIS, den.

tist, of Washington, District of Columbia, haveinvented or discovered a new and Improved7!ode of Telegraphing and of Generating Light,Heat, and Motive -Power; and I do hereby de-clare that the following is a fall descriptionthereo£

The nature of my invention or discovery con-sists, in general terms, of utilizing natural elec-tricity and establishing an electrical current orcircuit for telegraphic and other purposes with.out the aid of wires, artificial batteries, or ca-bles to form such electrical circuit, and yet corn..unicate from one continent of the globe to

another.To enable others skilled in electrical science

to make use of my discovery, I will proceed todescribe the arrangements and mode of oper-ation.

As in dispensing with the double wirq(which was first used in telegraphing,) andmaking use of but one, substituting the earthinstead of a wire to form one-half the circuit,so I now dispense with both wires, using theearth as one-lialf the circuit and the continu-ous electrical element far above the earth'ssurface for the other part of the circuit. I al-so dispense with all artificial batteries, but usethe free electricity of the atmosphere, cooper.atiug with that of the earth, to supply the elec.trical dynamic force or current for telegraph.ing and for other useful purposes, such as light,heat, and motive power.

As atmospheric electricity is found more andmore abundant when moisture, clouds, heatedcurrents of air, and other dissipating influencesare left below and a greater altitude attained,my plan is to seek as high an elevation as prat.tica hie on the lops of high mountains, and thuspenetrate or establish electrical connection

with the atmospheric stratum or ocean overly-ing local disturbances. Upon these mountain.tops I erect suitable towers and apparatus toattract the electricity, or, in other words, todisturb the electrical equilibrium, and thus ob.Min a current of electricity, or shocks or pul-sations, which traverse or disturb the positiveelectrical body of the atmosphere above andbetween two given points by communicatingit to the- negative electrical body in the earthbelow, 'to form the electrical circuit.

I deem It expedient to use an insulated wireor conductor as forming a part of the local ap-paratus and for Gond noting the electricity downto the foot of the mountain, or as far away asmay be convenient for a telegraph -office, or toutilize it for other purposes.

I de not claim uuy new key -board nor anynew alphabet or signals; I do not claim anynew register or recording instrument; but

What I claim as my invention or discovery,and desire to secure by Letters Patent, is-

The utilization of natural electricity fromelevated points by connecting the opposite po-larity of the celestial and terrestrial bodies ofelectricity at different points by suitable con-ductors, and, for telegraphic purposes, relyingupon the disturbance produced in the two elec.tro-opposite bodies (of the earth and atmos-phere) by an interruption of the continuity ofone of the conductors from the electrical bodybeing indicated upon its opposite or corre-sponding terminus, and. thus producing a cir.cuit or communication between the two with-out au artificial battery or the farther nee ofwires or cables to connect the co-operatingstations.

MAHLON LOOMIS.Witnesses:

BOYD ELIOT,0.0. Wn.sox.

Reproduction of Dr. Mahlon Loomis's Patent Specification

means of kites. He used antennaeboth rigid and suspended from kites-and about this time he also sentmessages between two ships inChesapeake Bay by means of anunderwater system in which he em-ployed two wires of varying lengths.

ConfirmationAt this juncture it might be

interesting to note that Doctor J.Harris Rogers, who developed asuccessful subterranean system ofradio, has also found that results werenot forthcoming unless the antennaleads used were of different lengths.

Before passing into a more detaileddiscussion of Loomis's experimentsand the apparatus used therein itmight be of interest to review brieflythe theories which both led him

to experiment and those which hesubsequently deduced therefrom.

In referring to the use of kites as ameans for obtaining energy for theoperation of his transmitter, Loomiswrote as follows :

The upper strata is a great elec-trical sea . . .

and also :Franklin certainly did draw down

electric fluid from the clouds; why notmake another draft? By the perfectionof appliances there is no doubt in mymind that a constant and never failingcurrent may be obtained powerfulenough to telegraph across the ocean. . and to this end I wish to writedown some facts and ideas, hoping toadd more and go further until success-ful experiments are made and thereality of this dream come to pass.One of the sketches reproduced on

page 305 (drawn by the WIRELESSMAGAZINE from copies of Loomis's

300

originals) show clearly the "electricalsea " which Loomis accepted as beingthe condition of the upper atmos-phere, and it is interesting to notethat this theory does in some respectsforeshadow the now generally ac-cepted theory of Oliver Heaviside,and though perhaps we are wont toregard the Heaviside layer- as a screenof ionised atmosphere rather than asa " sea of electricity" the semblanceis none the less striking.

Doubts ExpressedScientific men to whom I have

shown the drawings reproduced herehave expressed some doubt as to thevalidity of Loomis's theories. Thathe achieved something in a ratherblind and empirical fashion they donot doubt-in fact they cannot do so.

But they point out that whereasHertz and Marconi knew what theywere about and had a certain graspof the laws with which they weredealing, thus enabling them toexperiment intelligently, Loomis, incommon with others (Hughes, forexample), was a blind stumbler inthe dark; brilliant no doubt, butunable to offer a tangible basis uponwhich a science could be built.

Mistaken ImpressionTo back up this sweeping asserietn

they point out that some of Loomis'ssketches reveal him as under themistaken impression that what hewas doing was to achieve electricalcontact with a conducting layer inthe upper atmosphere and simplypassing electrical impulses throughthis medium between these twopoints.

Form of magnetic detector used by Loomis

This, they aver, is an entirelymisleading concept of affairs likelyto retard progress rather than to aidit by the fact that it sets a falsescent.

That this is not wholly the caseis clear from the wording of a billwhich was introduced into Congress

Wireless Magazine. nia.y, 1928

An American's " Radio " Experiments in 1865 !in the year 1872. In this bill Loomis'stheory was presented as follows :

This theory assumes that the earthitself, the atmosphere surrounding it,and the infinite depths of space en-compassing this aerial world, containsa succession of concentric circles orplanes of electricity of which thosenearest the earth are perpetually dis-turbed by oceanic currents, atmo-spheric -changes, alterations of day andnight, and the ever -varying effects of

SenatoreMarconi-

-took out hisfirst radio pat-

ent in 1896

solar radiation and lunar influences;but that above those pierced perhapsby the loftiest mountains, are concen-tric circles, or vast surrounding seasof undisturbed electricity, which maybe affected by any interpenetratinggalvanic force from beneath, causingelectrical vibrations, or waves, to passfrom that point within such electricplane around the world, as upon thesurface of some quiet lake one wavecirclet follows another from the point ofdisturbance to the remotest shores, sothat from any other mountain top uponthe globe any conductor which shallpierce this plane and receive theimpressed vibration may be connectedto an indicator, which will mark thelength and duration of such vibration.

Germ of Wave TheoryIt will be seen that Loomis certainly

had the germ of the idea of electro-magnetic wave propagation as lateroutlined by Hertz. For the timebeing, however, he unnecessarily

limited their radi-ation to certainplanes-a limitationwhich was missingfrom the Hertziantheory. Undoubted -1 y this limitationwould have dis-appeared had he re-ceived sufficientsupport to enablehim to continue hisexperiments - butspeculation is not theobject of this article.

But even though Loomis had notbeen able to escape from the conceptof an " electrical sea " in the upperstrata which was necessary for thepropagation of electromagnetic wavesyet he must necessarily have employedradio waves as we know them to -day,for what else could he have used?

The inventor found that he waslacking in sufficient funds to enablehim to do justice to his idea, and hemade efforts to obtain financial back-ing. In 1872 the Loomis Aerial Tele-graph Bill passed through Congressand carried with it an appropriationof 50,000 dollars, but this sum neverreached the inventor, owing to theunfortunate omission from the billof any mention as to the source fromwhich the money was to be obtained.

First U.S. Wireless PatentIn the same year Loomis secured

the first patent ever issued in theUnited States to cover a system ofwireless telegraphy.

A year later the first wirelesstelegraph company was formed inWashington, D.C., but the terriblefinancial collapse which followed theCivil War and whichculminated in thefamous "BlackFriday " broughtthe company's back-ers to grief.

Yet another ven-ture was attemptedinto the realms offinance, but onceagain a cruel fateintervened. Thistime the backerswere Chicago menand the calamitywhich ruined themwas the terrible

301

CochoctinMountain,Virginia

In reference to this sketch, Dr. Loomiswrote : " I intended to represent onestation ; galvanometer on log and incircuit with ground connection andwire from kite ; latter tethered to log.Operator watching time piece and

instrument"

Chicago fire which did much damage.Under these disappointments

Loomis began to weary and to des-pair, but before we pass to his finalrelinquishment of all hope of ful-filling his plans, let us examine for amoment the apparatus used by him.Apparatus Loomis Used

Details of these are not anymeans copious, but his sketchesclearly indicate that Loomis usedaerial, aerial inductance and earthin much the same way as at present.Artificial capacity, however, seemsto be missing from the system.Another sketch indicates that theinventor used a form of magneticdetector during his experiments, butthe exact form of this is not certain.That Loomis possessed some suchinstrument is, however, further de-duced from a scanty note and roughsketch which appear together in hisdiary :

It has been stated that if theextremities of the wire were not inmetallic contact with each other, orwith a continuous system of conductorsthese inductive currents would notbe produced . . . This condition sup-plies the means of producing in the

14 miles apart

BeorseDeer

Mountain

" Sent signals by aerial telegraph' between these twostations by elevating a kite on each mountain, the string ofwhich was a small copper wire, attached to galvanometer,each ground line lying in water. The signals perfect duringthe cloudy part of the day. Elevation about fifteen hundred

feet "

Wireless,Magazine. May. 1928

Thirty Years Before Marconi ? (continued)

polarity in the leg M and of borealin the leg N and the cessation of borealpolarity in the Leg M, and of australin the leg N, respectively, takes place.

All these changes produce momentarycurrents having a common direction.The contact being broken during theother semi -revolution, in which thecommencement of boreal polarity in

M, and of australin N, and the cessa-

-, tion of austral pol-arity in M and ofboreal in N, respec-tively takes place,that contrary cur-rents which would

" It must not be the primary electricity as me find it inthe atmosphere that ',lust be used, but modified, or asecondary current used."-Du. MAHLON Loomis, 1867.

wire an intermitting inductive currentconstantly in the same direction.

To accomplish this, it will be neces-sary to contrive means to break thecontact of either extremity of th:: coilwith the intermediate conductor duringthe same half of each successiverevolution of the magnet.

By this expedient the contact may bemaintained during the half revolutionin which the commencement of austral

otherwise at t endthese changes willbe produced.Unfortunately for

those who wouldmake a more exhaustive survey ofthis pioneer's work, certain of hisnotes and models (what they wereis not exactly known) were destroyedby a fire which occurred at theUnited States Patent Office inWashington.

The end of Mahlon Loomis wassimilar to that suffered by many a

pioneer. He died, literally of abroken heart, in 1886, at the home ofhis brother in West Virginia.

Deserted by his friends, even by hiswife, in his hour of need; abandonedby Congress; mocked and deridedby a certain section of the Press, theinventor had yet the faith to sayas the end approached :

If the present generation lives longenough their opinions will be changed,and their wonder will be that theydid not see it before. I shall neversee it perfected, but it will be, andothers will have the honour of thediscovery . . . the Congressional re-cords will furnish. The indisputableproof that the credit belongs to me.

YOU CAN GET A FULL-SIZE BLUEPRINT OFANY SET DESCRIBEDIN THIS ISSUE FORHALF-PRICE BY USINGCOUPON ON PAGE iii

OF THE COVER

LAST weekI hunted

up all the Con-tinental stations that gave lessonsin the English language and theresult was a real revelation as tothe manner in which these foreignstations treat it.

Some of the stations wereat the beginning of a course,others were trying to un-ravel our intricate syntaxto listeners who must havethought unkind things aboutthe "language of excep-tions." Two stations werereading our classics andgiving comments thereon.

English as she is spokenfrom these stations has anaccent that is foreign to ourown country, although in oneinstance the accent resembledthat of Dorsetshire. How-ever, when compared withother languages, Englishseems to be the favouriteand if the supply is in re-sponse to a demand, manythousands are keen learnersof our tongue.

French is taught from twoContinental stations ; German

Continental "Radioed'from two ; and Italian from one. TheB.B.C. stations give talks on French,German and other languages occa-sionally, but there is no comparison inthe amount of time put in by foreign

Build the Sunshine Five !

Here is a happy party enjoying a programme fromDaventry. Read all about the set en page 294.

302

English this countrylanguages in

to that whichEnglish gets on the Continent.

The new country of Czecho-Slovakia from its station at Bruenn(Komarov, 443 metres) gives a goodelementary lesson in English on

Monday evenings. The teach-er is an exceptionally goodlinguist and gets all hispoints home well, and thor-oughly. The course is con-tinued on Tuesdays andFridays.

From BerlinA very fine English lesson

is given from Berlin (Koenigs-wusterhausen) on Tues-days in the evening and alsoon Fridays. Besides thismany of the other Germanstations give readings fromthe English classics weekly.Frankfurt -on -Main besideshaving a good course onEnglish grammar has also aseries of readings. At pre-sent the text -book is Ivanhoeand it is done thoroughly.

E. B. R,

HALYARD'S Chat on the Month's Topics

ControversyWE seem to have made a little

progress at last in the controv-ersy about controversy, but I, forone, am not wildly excited about it,are you ?

As you are aware, the Governorsof the B.B.C. are now permitted tobroadcast controversial matter attheir discretion, on the understand-ing, I suppose, that a fair balancewill always be maintained betweenthe various interests involved.

It is expected that this lifting ofthe ban on controversy will not mean

Controversy

an encroachment on the time allottedto music and other forms of enter-tainment, but that studio and out-side debates will take the place ofsome of the educational and othertalks to which we have become moreor less accustomed, according to Ourdesire, or lack of desire, for theuplifting influence.

What kind of controversial topicswill be chosen for broadcasting, doyou think? I have only seen onetopic mentioned, or perhaps I oughtto say anticipated, so far, and thatwas a religious topic. Political topicswill, of course, be much to the front.

One suggestion I should like tomake with regard to these broad-cast controversies is that a wirelesssubject should be chosen occasionally.For example, wireless and weather

Wireless Magazine. May, 1928

would make a fine subject for debate,especially if one side of the questionwere debated from Matlock, don't youthink ?

Fool -proof SetsThe Chief Engineer of the B.B.C.

has expressed the opinion that thefuture of listening is in terms of fool-proof sets, and that the problem ofreception should be made as simpleas possible.

Now it is all very well to make awireless receiving set as simple aspossible, but I am rather inclined tothink that this simplification businesscan be carried a little too far. Let megive you an actual example of whatI mean.

One evening last week I acceptedthe invitation of a new friend of mineto go and hear his wireless set. Theset was a three -valve receiver,detector valve followed by two low -frequency amplifying valves, trans-former -coupled. There were the usualtuning and reaction controls on thepanel, but the three valves were con-trolled by fixed resistors and onesimple push-pull switch to switch thethree valves on or off simultaneously.

My new friend had had the set justlong enough for him to feel the desireto reach out and bring in the moredistant British stations and the Con-tinental stations. With his set as itwas, however, he found that he couldnot get more than five or six Britishstations, including the two Daven-tries. I tried my hand, but I could dono better.

The simplicity of the set was allvery well and useful up to a point,

Sketches by GLOSSOP

but as soon as ever the operatorwished to make some progress in wire-less listening he was severely handi-capped by that simplicity. What wasneeded more than anything else onthat particular set was separate andadjustable filament control for eachvalve.

I asked George for his ideas aboutfool -proof receiving sets, and hisreply was typical of him. He said :

"There would be no fire -proof safesif there were no fire. T re would beuo rain -proof coats if tre were no

Fool -proof Sets

rain, and there would be no fool-proof wireless sets if there were-"

Lookers -in?What is the truth about television ?

There seems to be a good many vagueand contradictory statements goingabout just now with regard to thisfascinating science.

One authority asserts that tele-vision will never be practicable untilsome entirely new principle is evolved.A great inventor tells us that tele-vision is remarkable, but hardlyapplicable for general use. Anotherauthority informs us that televisionhas come out of the laboratory atlast and that television is about toenter our homes, just as broadcasting

T211 Your Frienis About the Crusader-on Page 322

303

I Wireless Magazine. May. 1928!

Under My Aerial (Continued)

did a few years ago. Between theseand other conflicting statements thequestion is, where are we?

The most optimistic of the tele-vision prophets tell us that we shallall be building television receiversbefore 1928 is out. Wonderful, isn't

Lookers -in

it; too wonderful to be true, perhaps?Suppose we are all using television

receivers by the end of the year.What shall we call ourselves? Shallwe adopt the term " looker -in," in thesame way that we adopted the term" listener -in " a time back? If so, Iwonder whether the term will ulti-mately be reduced to plain "looker,"just as " listener -in " has become re-duced to "listener."

Here's a 'question for you. Whentelevision becomes an accomplishedfact, will the broadcast looker look atthe broadcast listener and will thebroadcast listener listen to the broad-cast looker?

. . .

A Super Loud -speaker" The Bell Telephone Company, of

America, has put on the market anew loud -speaker so powerful as to beheard a mile away," I said to Georgeduring a recent technical discussionon loud -speakers.

" Fine chance for somebody toinvent a protective ear filter," re-marked George thoughtfully.

"Listen to this, George. It is cal-culated that a million people can bespoken to at the same time by thishuge loud -speaker."

" Suppose some of the million ob-ject to being spoken to? What'sgoing to happen then? Is the BellCompany in the market with a speci-ally constructed, portable, sound-proof cellar? "

" No idea, George. Continuing ourdiscussion on giant loud -speakers, ithas already been hinted that furtherdevelopments may lead to the build-ing of a monster loud -speaker with arange sufficiently great for it to he

heard across the Atlantic Ocean. Justimagine that now. News broadcast inNew York would be heard here inEngland. Wonderful "

" What is the distance from NewYork to England? "

" Oh ! er-a matter of three thou-sand miles or so."

"And the speed of sound waves? "" Eleven hundred feet per second."" In miles per hour? ""Seven hundred and fifty, near

enough.""Three thousand divided by seven

hundred and fifty? "" Four.""The idea is no good, then. They

will never build such a loud -speaker."" Why, George ? "" Because it would take four hours

for the sound waves to travel fromNew York to England. The news

A Super Loud -speaker

would be old by that time. Wirelesswaves travel the same distance prac-tically instantaneously. They'd usewireless, every time, because it'sheaps quicker."

.Sunday Programmes

What do you think of our Sundaybroadcast programmes? Do theymeet with your approval as they arenow constituted, or would you sug-gest alterations in them ?

Sunday Programmes

B.B.C. officials in London havereason to believe that the number oflisteners who listen to the Sundayafternoon wireless concerts is muchsmaller than it used to be. Have youany guilty feeling with regard to theseSunday afternoon concerts? Do youneglect to make use of them? I am

304

afraid I am guilty of such neglect, thereason being, in my case, a liking fora stroll in the country on a Sundayafternoon and not, as in some cases, aliking for forty winks after a Sundaydinner.

What is your feeling in the matterof the religious service broadcast onSunday evening? Would you preferthis service to be broadcast earlier inthe evening than at present, or doyou think that this broadcast serviceshould not be allowed to encroach onthe usual hours of church service?There are advantages in the earlierservice, perhaps, in that there wouldbe a greater choice of services whichcould be actually relayed from a placeof worship.

To invalids, to elderly folk, and toothers who cannot leave their houseon a Sunday evening, one of thegreat charms of listening to a servicebroadcast from a place of worship isthat the listener is taking part in aservice in which others are takingpart.

Perhaps it is because of this thatmany listeners continue to press forthe earlier service.

Village AerialsLast week -end I visited a small

country village situated at least fourmiles from the nearest railwaystation. I did not expect to see muchevidence of wireless in this village,but, on walking the length of thevillage street, I was surprised to seequite a large number of aerials.

Some of these village aerials lookedthoroughly efficient, but there was apreponderance of two types whichseemed to me to warrant strong dis-approval. The first of these two typeswas a single -wire aerial which, at thehouse end, was brought to within afoot or so of a chimney. The down -lead came down parallel to the slopingroof, and just above that roof, to aninsulator placed on a horizontalbracket which projected out horizon-tally at the lower edge of the roof.

From this insulator the down -leadwas taken to the leading -in tube in theusual way. The aerial wire was thusdivided into three parts, the hori-zontal part from mast to chimney, thesloping part from chimney to edgeof roof, and a nearly vertical part

Wireless.Magazine. May 1928

Halyard's Chat on the Month's Topics

from edge of roof to leading -in tube.It was the part of the aerial passing

over the sloping roof which I did notlike. An aerial taking the form of atrue inverted L, with the usual twoparts, horizontal and vertical, wouldhave been much better in my opinion.

Last Week -end

The necessary change could easilyhave been made by letting out thechimney insulator on a wire or ropelong enough for the insulator to clearthe roof.

The second type of aerial I tookobjection to in this remote villagewas a twin -wire aerial placed aboveand parallel to the ridge of a roof.

.A Strange Theory

Perhaps by this time you may haveseen or heard several of the migrantbirds which return to your district

You May Have Seen . . . .

for the summer months-the swallow,the corncrake, and the cuckoo, forexample.

Have you ever heard or read of anytheory that explains the migratoryinstinct and sense of direction pos-sessed by these migrant birds? Thelatest of such theories is a very strangeone, and, like a good many of thefanciful theories of the present day,this strange theory has wireless as itsbasis.

Briefly, this new theory is that abird has a short-wave transmitter andreceiver in its brain, and that, inflying long distances, the bird makesuse of wireless waves without know-ing it.

I am afraid that I cannot quite getthe hang of this theory, can you? Ifa bird sends out wireless signals, it

must send those signals out to someother bird. What other bird does itsignal to? If a bird receives signals,it must receive those signals fromsome other bird. What other birdsignals to it? There seems to be littleuse in birds signalling to each otherwhen in flight and within sight ofeach other.

Another bothering thing about thistheory is that, if it applies to birds, itmay apply to other living creatures,butterflies, for example. You knowthat butterflies fly long distances andfind their destination in some extra-ordinary fashion.

Then again, we might expect thetheory to apply to the dog which findsits way back to its old home overthirty miles of country.

I would like to know what youthink of this theory.

There and Back"George, you remember explaining

to me 'how it was that the loud-speaker was more popular than thephones in America? " I asked mytechnical adviser last Thursday night.

" Nope," replied George." But you ought to remember such

things, George."" If I remembered all I said to you,

Mr. Halyard, I should be able towrite a book on wireless. What wasthe explanation I gave you on thisimportant matter? "

" Well, George, you said the reasonwhy the loud -speaker was preferred tothe headphones in America was thatyou can't wear phones comfortablyand chew gum at the same time."

"A jolly good reason, too. What'swrong with it? "

" Nothing at all, George. Theinteresting thing about your explana-tion is that an American wirelessperiodical copied it."

" Very nice of them, shows theirgood taste, but there's nothingunusual about that, is there ? "

There and Back

305

" No, George, but I've not finished,yet This morning I picked up one ofour weekly wireless papers and Ifound your ingenious explanationrepeated there. The funny thing wasthat this weekly paper had not copiedyour explanation from my originalversion in ' Under My Aerial,' butfrom the American magazine. Soyour little joke travelled to Americaand back, old man."

" Pretty live joke to do that, wasn'tit? It gives you a good idea as to howfar a joke will carry in these days ofrapid transit."

Load -speakersDo you ever read wireless articles

in the non -wireless papers? It is notoften that I do so, but just lately I

" Loud "-speakers

happen to have seen a number of sucharticles dealing with loud -speakers.

In one of these articles I read thatthe horn type of loud -speaker wasrapidly becoming extinct, and thatthere was no wonder about this, sinceany cheap loud -speaker of the conetype was superior to most expensiveloud -speakers of the horn type.

What do you think of that now?Do you agree or not? It all dependson the kind of loud -speaker you hap-pen to be used to, doesn't it?

In another of these articles, I cameacross the very definite statement thatno good loud -speaker could be hadfor five pounds or less. Well, if thatis true, I, for one, have never had agood loud -speaker yet.

The best loud -speaker I ever haddidn't cost five pounds-not quite-but it very nearly did. In fact, itcame within five shillings of thatamount. It is a very good loud-speaker though, and I am still veryfond of it.

The test to apply to a loud-speaker is the amount of enjoymentyou get out of it. What do yousay about it? HALYARD.

Wireless Magazine. May. 1928

In this article we are able to give particulars of a simple four -valuer comprising a stage ofhigh -frequency amplification, a detector, and two stages' of low -frequency amplification.Both upper and lower wavelength bands are covered by a movement of a single switch on the

panel-- a great boon for the operator.

\-erhe 0 -coil Four/

ANUMBER of articles haveappeared recently in the pages

of the WIRELESS MAGAZINE from thepen of our Technical Editor, J. H.Reyner, B.Sc., A.M.I.E.E., explain-ing a new and revolutionary type oftuning coil that is now available foramateur constructors-namely the"Q" coil.

Advantages of the "Q" CoilBriefly, the advantages of this new

coil are that by means of a simpleswitch incorporated in the coil itselfas manufactured it can be made tocover both lowercasting bandswavelengths; itastatic on the low -wavelength band andtherefore does notpick up the localstation as would anordinary coil; andlastly, these advant-ages are obtainedwithout the use ofany form of metalscreening.

Careful researchwork carried out overa period of manyweeks has shown thatthe principle of the"Q" coil can be

and upper broad -ofis

applied equallyas well for the construc-tion of high -frequency transformersas for aerial coils. This means that atonce a great simplification in the de-sign of multi -valve receivers is avail-able for the home constructor andWIRELESS MAGAZINE readers will atonce see how easily they can take ad-vantage of this latest development.

By means of an ingenious form ofconstruction it is possible to placeany number of "Q" coils in a row andarrange their switches on a commonspindle; in this way the moving ofone knob will change the wavelengthrange of all the coils at once-what

CD -2

One Knob Only toChange WavelengthRange of Both Aerialand Anode Tuning

Circuits

Designed, Built andTested by the "Wiry essMagazine" Technical

Staffa welcome boon for the operator !

Because four-valvers are particu-larly popular amongst a large numberof listeners, the WIRELESS MAGAZINEthis month gives particulars of asimple four -valve receiver makinguse of "Q" coils (a two-valver wasdescribed last month-see " The ' Q '-coil Two," WIRELESS MAGAZINE,April, 1928).

Straightforward CircuitThe circuit adopted is a perfectly

straightforward one as can be seenfrom the diagram reproduced on thispage. A stage of neutralised high -

frequency amplifica-tion is followed by aleaky -grid detector,

0L.S.

OOtz Iff+

Here is the circuit of the Q -coil Four. Note that the connections forthe " Q " transformer are the same as those for a six -pin split primary

transformer

306

and two stages of low -frequency amplifica-tion-the first trans-former -coupled andthe last resistance -capacity coupled.

A glance at thehigh -frequency partof the circuit willshow that the con-nections for the "Q"coil are exactly thesame as those for thestandard type of six -pin split -primarytransformer, a form

f

of Reinartz reaction being obtainedin the usual way.

The use of "Q" coils, however, isnot the only new feature about thisreceiver, for a new, and what may beto some constructors, easier, methodof wiring is adopted. This will beexplained at greater length later inthe article, but the resulting neatappearance can be judged from thephotographs of the receiver repro-duced in these pages.

Very Simple ControlsJust as neat is the external appear-

ance of the Q -coil Four, which canbe seen from the photograph repro-duced on this page. The two largedials are respectively those for tuningthe aerial and anode circuits. Thesmall dial in the centre is the reactioncontrol, while below that are thewavelength -range switch arm andthe knob of the push-pull on -offfilament switch.

A complete list of all the partsrequired is given on page 308 and

Front view of Q -coil Four

constructors are recommended tokeep as close to the original specifica-tion as is possible. The names thatappear first in the brackets are thoseof the manufacturers whose partswere used in the original WIRELESSMAGAZINE receiver; the other namesare those of manufacturers who cansupply suitable alternatives.

Full-size BlueprintBefore beginning the construction

of the Q -coil Four readers are re-commended to obtain a full-size blue-print drilling guide, layout and wiringdiagram ; this can be obtained forhalf-price, that is 9d. post free, if thecoupon on page iii of the cover isused before May 31.

Ask for blueprint No. W.M.7i andaddress your enquiry to BlueprintDept., WIRELESS MAGAZINE, 58/61Fetter Lane, E.C.4. It should be

[Wireless Magazine. May. 1928]

mentioned here that although manyconstructors prefer to work to a full-size blueprint its use is not absolutelyessential, for all the essential detailsare reproduced in these pages on asmaller seal'.

It will be observed that the base-board is not fixed right at the bottomof the panel, but a short distance up

it, and thatall the wir-ing of thebaseboardcomponentsis carriedout under-neath thebaseboard.Althoughthis lookscomplicatedthe WIRE-LESS MAGA-ZINE h a s

found that this method of sub -baseboard wiring can, in fact,be carried out quicker than the usualmethod.

After having mounted all the corn -

The Q -coil Four with valves inposition ready for use

307

ponents in position on the panel, thebaseboard components should nextbe mounted before panel and base-board are fixed together. Wiringup will be very much simplified ifexactly the same components as usedin the original set are employed bythe constructor.

When the components have beenmounted on both the panel and base-board (note that the .000i -micro-farad fixed condenser in the aeriallead is screwed underneath the base-board close to the aerial terminal),these can be fixed together by meansof brackets.Positions of the "Q" Coils

It will be seen that the "Q" coils areplaced one behind the other. Under-neath each base is a part of the switchwhich has a square hole cut in it.Through this hole is placed the squarespindle which thus enables bothchange -over switches on the twocoils to be operated at once by meansof a single knob on the panel.

In the case of coils other thanLewcos it will be necessary to join thespindles together by some simple

Wireless Magazine, May. 1928

The Q'coil Four (Continued)

Plan view of the baseboard of the Q -coil Four

coupling device, such as a collai withtwo set -screws.

For the convenience of constructors

-FRONT &EMI%TO TAKE F'AtiEL

ao" )(.8"

Details of Cabinet for the Q -coil Four

two wiring diagrams have been pre-pared. The first shows the sub -base-board wiring as it actually appearsfrom the underneath (see diagram onpage 309) and the second shows itdotted, from above. Only the firstdiagram has been prepared as a full-size blueprint.

Several Methods of WiringThere are really three methods of

wiring up this receiver and these willhe explained in detail :

The first method, which is also thequickest, is to pick out all thoseterminal points marked a on the toppart of the wiring diagram and along-side each drill a hole through thebaseboard with a small twist drill.Attach a wire to each terminal pointand lead it through the hole under-neath the baseboard.

Now turn the set over and connecttogether in any convenient way allthe wires projecting through the

board. The lowerhalf of the wiringdiagram repr o-duced on page 309will be a check onthese connections.

Replace thereceiver in itsordinary position;pick out all theterminal pointsmarked h, drillholes alongsidethem and pushwires through asbefore. Again turnthe set over andconnect togetherall the projecting

leads. Carry on in this way through-out the alphabetical sequenceto u.

The second method necessitates

Components Required1-Ebonite panel, 20 in. by 8 in.

(Becol or Will Day).2-.0005-microfarad variable con-

densers, with vernier dials(Burndept, Cyldon, or Ray-mond).

I-.000t-microfarad variable con-denser (Cyldon and Igranic).

1-Q aerial coil (Lewcos, Wearite,Atlas, or Bowyer -Lowe).

1-Q high -frequency transformer(Lewcos, Wearite, Atlas, orBowyer -Lowe).

-Neutralising condenser (Igranic,Wearite, or Gambrell).

4-Anti-microphonic valve -holders(Benjamin, Lotus, or W. andB.).

1-High-frequency choke (Mag-num, Igranic, or Wearite).

1-Low-frequency transformer,ratio 4 to I (Gecophone,Mullard, or B.T.H.).

2-2-megohm resistances with clips(Loewe, Dubilier, or Mullard).

I-.25-megohm resistance withclips (Loewe, Dubilier, orMullard).

.0001-rnicrofarad fixed con-denser (Edison Bell, Dubilieror Lissen).

I-.005-microfarad fixed condenser(Edison Bell, Dubilier, orLissen).

1-Terminal strip, 12 in. by 2 in.(Bccol or Will Day).

2-.0003-microfarad fixed con-densers (Edison Bell, Dubilieror Lissen).

1-Pair panel brackets (Magnum).12-Terminals, marked.: - Aerial,

Earth, L.T.±, L.T.- ,H.T.+1, H.T.+2, H.T. + 3,G.B.+, G.B.--I, G.B.L.S.+, L.S. - (Belling -Lee).

1-Push-pull on -off switch (Lissen,Lotus, or Benjamin).

6-2 ft. lengths insulated wire(Glazite).

I-Cabinet, with g in. baseboard(Pickett's).

0000 ...... 0 ....... 0000

This view shows the sub -baseboard wiring of he Q -coil Four

308

Wireless Magazine. May. 1928

Covers Both Wavelength Bands Without Changing Coilsrather more soldering, but is notquite so wasteful of wire, althoughthat is a small item in the construc-tion of a four -valve receiver.

Again pick out all the pointsmarked a and drill holes alongsidethem. Now connect a short length ofwire (1/2 in. to r in. will do in mostcases) to each terminal point andpush through each hole. When thebaseboard is turned over, there willbe projecting through it a number ofpoints of wire; these should all beconnected together with one wire oras few wires as possible, which must,of course, be soldered.

Again the lower part of the wiringdiagram reproduced on this pagewill act as a check.

Following Connections SeparatelyThe third method of wiring is on

more usual lines and can only becarried out in conjunction with thediagram reproduced on page 31o.Here, each connection can be followedthrough separately, the dotted linesindicating that part of the wiringwhich is carried out beneath thebaseboard.

Choosing suitable valves for usein the Q -coil Four is not a difficultmatter. For the high -frequencyamplifier any valve with an impedancein the neighbourhood of 20,00o to30,000 ohms is suitable. For thedetector a valve of slightly lowerimpedance, say, 15,000 ohms, will bebest.

First Low -frequency ValveAlthough theoretically an imped-

ance of round about 8o,000 ohmswould give the greatest amplificationfrom the resistance -coupled stage, thethird valve should preferably have alower impedance than this; a valvewith an impedance of 8o,000 ohmswould probably be overloaded duringthe reception of even moderately loud

. transmissions owing to lack of suffi-cient grid swing. A valve with an

t P a m k l a b a d0 0 0 0 0 0 0 0 0 0 0 0LS- \b1 65-a G5.-1 GBt Mitt AT+2. Mitt 1.1: Lit (Min ALMAL

This layout and wiring diagram of the Q -coil Four can be obtained as a full-sizeblueprint for half-price, that is 9d. post free, if the coupon on page 'ill of the coveris used before May 3i. Ask for Blueprint No. W.M. 71.

20".4(343'

ty..7.-----notaffmartsuk111-- TO 'Wan 5UPPULD

Hv-5=-H MAMA

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Panel layout of:he Q- coilFour, n o t re-quired if a full-size blueprint isused (see above)

309

Impedance in the neighbourhood of15,000 to 25,00o ohms is thereforerecommended for this stage.

Super -power Value for Last StageOf course, the last valve Should be

of the super -power type, preferablywith an impedance of Less than 8,000ohms. The quality of reception,although not the volume, is very

Wireless Magazine: maay. 1928

The Q - Coil Four (Continued)

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gAnother wiring diagram of the Q -coil Four (not supplied as a :sprint)The dof.,:ed lines indicate that part of the wiring carried out underneath the base-

board. Each connection can be followed through separately

considerably increased as the imped-ance of the last valve is broughtlower.

To carry out a rough test of thereceiver, place the valves in theirrespective holders and see that theon -off switch is " in," that is, in the" off " position.

Battery VoltagesConnect up the aerial and earth

and apply voltages to the terminalsas follows : To H.T. +I about 6o to8o volts; to H.T. 2 about 6o volts;and to. H.T. + 3 the full voltage ofthe battery, which should be at least120 volts. To G.B. I apply about3 volts negative and to G.B. -2 apply9 to 18 volts negative.

To operate the receiver, pull outthe on -off switch and adjust the

reaction condenser until a slightrustling. or hissing sound is heard;this indicates that the set is on theverge of oscillation and in a sensitivecondition. Now turn both the largetuning knobs simultaneously until atransmission is picked up, when thereaction control should be readjusteduntil the best results are obtained. Itmay also be advisable to readjustboth the high-tension and grid -biasvoltages after a few stations have beentuned in.

Early in the first tests the high -frequency valve should be properlyneutralised. Tune in a reasonablystrong signal and switch off the high -frequency valve only by removingone of the filament connections from!ts holder. Now adjust the neutralisingcondenser until the signals become

inaudible. When this occurs the valvehas been properly neutralised andthe filament connection can bereplaced.

It should be noted that the receiveris adjusted for reception on the longwaveband when the switch arm ismoved to the right, and for the shortwaveband when it is moved to theleft.

Mass(Re) Production!

HOW much does it cost you to runyour receiver? Not much, you

will probably reply, no matterwhether it is a crystal set or a three -or four -valuer. Even if you have a" super " set of five, six or sevenvalves the actual operating costswill be out of all comparison withthe results obtained.

Eighty Loud -speakersBut suppose you were asked to

operate " super -super " set havingnineteen stages of amplification andsupplying 2,000 pairs of phones andabout eighty loud -speakers Whatwould be the running cost?

The Lambeth Hospital, London,where such a giant set as this hasbeen in operation for a considerabletime, finds that the all -in cost is apenny an hour.

The set is quite automatic inworking, and has a pre-set timeswitch, which charges the batteriesand switches the receiver on toLondon or 5GB as required.

Thousands of Listeners At OnceAs several thousands of patients

are enabled to hear the programmesby means of this giant installation,the cost per hour is perhaps not so"exCessive as it may at first appear.

It is only another instance ofmass production, or rather massreproduction, making for cheapness !

QUEUE.

MEMORISETHESESYMBOLS

Valve

--L-

13

attery ',battery Crid Leakpow -tension)-tension) (high-tension) and Condenser

9r 91ILLoud -speaker Transformer

(high -f rtguency)Transformer Fixed Variable

(low -frequency) Renounce Renounce Switch

310

I

Wireless Magazine. itia.y. 1928

YOURVALVE FILAMENTIts Structure and Liability to Faults

SIR OLIVER LODGE, Vice -Presi-dent of the Royal Society of Arts,

was Chairman at a lecture givenin the hall of this leading organisa-tion on February r6, 1927, by Mr.Clifford E. Paterson, O.B.E., on thesubject of wireless valves, and thesenotes are based. thereon.

Fig. 1.-A pinch of ta. igsten powdergreatly magnified. The metal cannot bemelted; it is mechanically compressed andthen drawn on wire. The granules

are semi -crystalline.

The filament is the very "soul"of the valve; there must not be theslightest leakage in its vicinity, elseit will corrode and spoil.

Tungsten is the usual metal em-ployed to make it. This remarkablemetal cannot be melted like mostothers, and after treatment of itsores it is isolated as an extremelyheavy black semi -crystalline powder,as shown in Fig. 1.

Mechanically CompressedThis powder is mixed with a certain

composition, is compressed mechani-cally, and subsequently drawn toWires.

Yet its treatment gives it a strengthand tenacity equal to those yieldedby steel heated to a temperature ofbetween 20o degrees C. and 4.00degrees C.

The resulting tungsten bar is wedgeddown, by stages, till it can be drawnthrough dies into filaments of .002

milliammetre diameter, resemblingfine human hairs.

Even so that wire consists ofmyriads of individual crystallinegranules, forced lengthways betweenone another, as shown in Fig. 2.

Re -crystallisation due to variationsin temperature, oxidisation by leak-age, air and vapour, and other some-what obscure factors, causes itto become distorted, as shown inFig. 3.

The blisters of tungsten oxidecannot transmit the current soequally as does the pure metal; hencedisasters are likely to follow, orenable faults to develop which wouldnot occur from the same sources,were the corrosion absent.

Adding ThoriaSome makers add a trace of thoria

-that is, thorium oxide-to thetungsten to overcome certain spoli-ation 'tendencies. This compoundwill often restrain crystal growth;and so prolong the "active life" ofa valve filament.

On the other hand, other makersadd a trace of silicious soda to hasten

Fig. 2.-Enormously magnified valve -filament (really as fine as a hair to thenaked eye) before being heated by electricalcharge. It is fibrous through coalescence

of its crystals longitudinally.

crystal growth so rapidly (beforethe valves are distributed) that whenthe filament is heated the wirebecomes almost instantly a series of

very long crystals, tenaciously andpermanently held together.

Crystal growth having thus beenaccelerated before the wireless manuses his valve, it cannot happengradually over a period of a fewweeks or months (as is often the case),and so fail in its purpose.

j. -A portion of a valve filament,highly magnified, after becoming " can-cerous" and distorted in the manner

explained in the text.

The " mirror" of a valve is notquick -silver (mercury), but is a filmof sublimed magnesium, and is therenot so much to conceal the brilliantlight of a working valve, but toabsorb gases and vapours whichmay interfere with the characterof the filament, that really has toendure wonderful experiences, all ofthem microscopically important asregards reception. JAMES SCOTT.

Four American women in oneneighbourhood recently tuned -in ona dressmaking lesson from WGBS.The following Sunday, as ever was,the four blossomed forth in identicalgowns, the four having followed inevery detail the teacher's directions,even to material and trimming.American husbands who do not wishto be persuaded into buying theirwives a wireless set for the homenow quote this example of simul-taneous dressmaking.

Read About the Crtbader on Page 322 and Tell Your Friends

311

Wireless Magazine. May, 1928

DOVE WAYr To HEAR

PARLIAMENT ?

"I doubt it

THERE was once a time, when Ihad not been in. Parliament so

long as I have now, when I wouldeagerly have held up both my handsto vote for the general broadcastingof Parliamentary proceedings.

boring Listeners Stiff ?But to -day I think I know better.

1 don't think the public would reallywant to hear us-however muchsome of us might want them to. Ithink we should bore them stiff anddecrease their interest in Parliament-ary affairs instead of stimulating it.I think the difficulty of arranging thetime -table so that all parties had a fairshow might cause disappointmentamong the listeners who failed tohear their favourites, and a certainamount of ill -feeling in the House.

And I think, too, that the technicaldifficulties in the way of broadcastingthe debates in such a way as to renderthem intelligible to the listenerswould be of such magnitude as tobe almost insuperable. Let meindicate a few of them.

Daily Business of the HouseTake the first daily business of the

House-Question Time. To thevisitor who sits in the Public Galleryof the House of Commons there is nota shadow of doubt that the hourbetween 2.45 p.m. and 3.45 p.m.each day, when members bombardand cross-examine Ministers on thework of their Departments, is themost interesting battle of wits thatanyone could wish to witness.

1 1 I I 1 H11111111(1

wireless. In the firstplace, the questionersdo not really recite theirquestions, but merelycall out " QuestionNumber So -and -So," asit appears in print uponthe Order Paper.

And whilst, there-fore, the radio listenerwould be able to hearthe reply of the Minister,that reply would losethree-quarters of itsinterest in consequenceof the listener having noidea of the questionthat the Minister wasattempting to answer.The difficulty is over-come for the benefitof the visitors in thePublic Gallery of theHouse by the provision

. . And 1 sometimes think our tedious debates would make them weary" of copies of the OrderPaper which enable them to followthe proceedings intelligently.

The questioners, as a rule, are outto score a point off the Ministers, tocorner them, to catch them napping,to involve them in a contradictionof some previous pronouncement, or tohumiliate them in one of the hundredways that Parliamentary proceduremakes possible.

They hurl at them questions aboutUnemployment,Super-tax, Warships,the size of the Russian Army, howmuch we owe America, when Germanyis going to pay, how many sailorscaught influenza last autumn,whether the inmates at such -and -such a workhouse have butter ormargarine for breakfast, and theMinisters, in the course of theirreplies, are always careful to try towhitewash themselves and theirDepartments, and to bang the ques-tioner on the head-if he happensto sit on the other side of the House-with a rhetorical hammer big enoughand heavy enough to keep him quietand stop him from asking any furtherawkward questions for the rest of theday.

Sometimes the Minister wins ; some-times the questioner. Sometimes ananswer leads to an angry storm ; abreeze blows up; there are hardwords; threats are thrown from oneside of the House to the other; andthe incident perhaps ends with somerecalcitrant member being orderedto leave the House.

All this is exceedingly interesting-to the actual eye -witness. But itwould be extremely difficult-if notimpossible-to "get it over" on the

312

Adequate Number of Micro-phonesThen, again, the technical question

of providing an adequate number ofmicrophones in the House wouldpresent some difficulty. It would bethe easiest thing in the world for amicrophone to be placed in front ofMr. Speaker, who presides over thedeliberations of the House, and on theDespatch Boxes on the table betweenthe two Front Benches, from whichthe Prime Minister and Mr. RamsayMacDonald and their respectiveCabinet and "Shadow Cabinet"colleagues address the House.

But there are five hundred or moreM.P.s who have not the distinctionof being entitled to speak from theFront Benches, and these BackBenchers are scattered in some hun-dreds of seats all over the House. Howis it going to be possible to providemicrophones which will be availablefor the use of all of them ?

A "Mike " for Each Member?It would be possible to require them

all to speak from a central rostrum,I know, but the House would neveragree to such a change, and, from myexperience, it would not work,especially during the hurly-burly ofsupplementary questions or a par-ticularly animated debate, whendozens of members are jumping ontheir feet at once with interrogationsand interpellations. The only otherway would be to provide each member

with a microphone of his own-andeven that would not entirely solve theproblem.

In a set debate which is fairly freefrom interruptions-such a debate aswe sometimes get on DepartmentalEstimates-where one speaker followsanother in methodical and pre-arranged order, I admit that therewould not be so many difficulties toovercome as in the excitement ofquestion time or the rough-and-tumble of a debate on some first-classpolitical issue, where feelings runhigh.

Not Worth HearingBut those routine debates would

hardly be worth hearing. Theyusually deal with all kinds of detailedand technical points of Departmentaladministration, and there is verylittle about them to fire the imagina-tion or rouse an audience to any pitchof excitement.

It is the big debates on questionslike the Budget, the Zinovieff Letter,the Reform of the House of Lords,and the Prayer Book that make areal appeal --and in broadcastingthem the difficulties that I havementioned have always to be bornein mind.

Then there is the very importantquestion of preserving the wirelessfrom any suggestion of suspicion withregard to party preference or preju-dice, and although the intentions ofthe authorities in control might beof the best, there are difficulties thatwould be put in their way as a resultof the Parliamentary time -table andthe rules of procedure of the House.Let me state the case of a fewspecimen full-dress debates to illus-trate my point.

Declaration of PolicyIn the case of a debate involving an

important declaration of high policyby the Government, for instance, itwould usually happen that Mr.Baldwin, Sir Austen Chamberlain, orwhichever Minister happened to bemaking the statement, would havecompleted his remarks long beforethe majority of listeners arrived homefrom work in the evening and begantheir listening -in.

Similarly, in debates where Mr.Ramsay MacDonald or Mr. LloydGeorge, on behalf of the .Opposition,indicted the Government on amotion of censure with some dere-liction of public duty their, speeches,too, would have been completed by

Wireless Magazine. max 19281

five or six o'clock in the evening atthe latest.

Listeners, therefore, would onlyhear the tail end of the debate, andthe programme, to them, would besomething like seeing a performanceof Hamlet without the ghost.

Then take the case of the BudgetSpeech. Mr. Winston Churchill'sspeeches are always worth hearing.So are Mr. Philip Snowden's. Soth5,t whichever one of these happenedto be Chancellor at the time couldbe relied upon to give what the pro-gramme compilers could describe asa real " star turn."

But the Budget Speech begins atabout a quarter to four in the after-noon, and when the majority oflisteners reach home at six o'clock it isall over. They would not even havethe privilege of listening to the ex -Chancellor attacking the Chancelloron behalf of the Opposition and flayinghis Budget proposals to pieces-sometimes a far more interesting" turn " than the actual BudgetSpeech itself-because this speech is

ames P. Gardner, M.P., -the authorof this interesting article

always saved over until the followingday, when it begins at a quarter tofour again and finishes about half -past five.

All that happens on the evening ofBudget Day, after the Chancellor hassat down, is that the House proceedsto pass some formal and tiresomeresolutions which have no interest foithe general listener at all.

The same thing happens withregard to that other great Parliamen-tary performance-the State Opening

313

by the King. This takes place atnoon, when every few listeners wouldhave a chance of hearing it.

Then there is another disadvantage.Between the hours of about eighto'clock and nine -thirty, just when thelistener would have finished hisevening meal and settled himSelfdown in a comfortable armchair bythe fireside and adjusted his head-phones or his speaker, he would findpractically nothing of importancecoming through at all.

Filing Off for DinnerThe reason is that members begin

to file off for dinner at about eighto'clock, and the only people .whoremain in the Chamber to carry on thedebate are the Back Benchers, whofind that the emptiness of the Housegives them a chance of being calledon to speak-a chance, which, hadthe House been full, would have beenUnlikely to come their way.

There are, moreover, innumerablepoints in Parliamentary procedurewhich would befog the mind of theordinary listener, and our antiquatedformulae would seem like Dutch.

The confusion would not be lessenedby the fact that members never referto one another by name duringdebates, and there are many listenerswho would not identify the RightHonourable member for Aberavonor the Right Honourable member forCarnarvon Boroughs as Mr. RamsayMacDonald and Mr. Lloyd Georgerespectively, with the result thatmuch of the point of the speecheswould be lost upon them.

Very Serious DifficultiesI might go on enumerating the

difficulties of broadcasting Parlia-mentary proceedings ad infinitum.But I have said sufficient, perhaps, toshow that there are very seriousdifficulties, and to show that theWestminster programme might notbe quite such a bright and interestingone as some people are inclined toimagine.

I need hardly say that if the diffi-culties can all be overcome nobodywill be happier than I shall. But itis buoying up false hopes to encouragethe idea in people's tninds that theB.B.C. is keeping from them an extraprogramme that might be theirs bythe waving of some magic wand, andthat they are missing something that,would be in the nature of a "pro-gramme of all the talents." It wouldnot.

I'Wireless Magazine. May. 1928

If Yor, Read This Art'cle You Will At Once See Why You Should

krii#019010,04011dI 1 is my experience that many1 people-far too many people, infact-have gramophones which donot give results as good as thoseobtained from their radio receivers,from the point of view of purity.

This is not the fault of gramophonemanufacturers, but will always be sowhile a good set can be bought formuch less than the cost of a mediocregramophone plus records. Where themoney goes is in acquiring records togive an entertainment comparingfavourably with that obtained for aten -shilling radio licence.

Gramophones & GramophonesThere are gramophones and gramo-

phones, just as there is your wirelessset and the cacophony -creating gad-get belonging to the man next door

If it were ever your lot to makegramophones for selling at " cut 'prices (and thank your lucky stars ir!is not !) you would find that the placeto save most money is the sound -box.From the point of view of music aloneit does not matter very much if thecabinet is solid oak, or deal, or has" Tate " painted at odd places on theinside.

What does matter is that the sound -box should be made with strictregard for certain technical details,the nature of which need not botheryou very much.

A Vast ImprovementNow see how an inferior instru-

ment may be improved almostbeyond recognition by using anelectrical pick-up and reproducingrecords through the loud -speaker.Forget, first of all, much that hasbeen said about pick-ups being suit-able for large sets and for public-address work. This is so, but it is notthe limit tf their capabilities. Remem-ber that a pick-up costs less than theprice of a dozen records.

Two stages of low -frequency ampli-fication should follow the pick-up,but this does not mean that a three-

valver of the popular detector-two-L.F. type is the smallest set that canbe used. A pick-up can be added tothe grid circuit of a detector, and(provided grid bias is altered to suit)the detector functions as an amplifierfor the low -frequency current gener-ated by the pick-up reed.

This brings humble two-valvers,with either transformer or resistance -capacity coupling into the boundsof pick-up possibility.

These are the advantages whichaccrue from " electrifying " a gramo-phone: vastly better reproduction,equal, in fact, to the set working at

TOM ARM OFCRAMOPHOME

PICK-UP (AM.

RECO

PERMAMENTMAGOET

e -UP C011,5

RUBBEROAhl P1114

This sketch clearly shows the principle of operationof an electrical gramophone pick-up

its best at full volume; easy volumecontrol, complete absence of needlescratch, less wear on records, repro-duction of detail which in someinstances of sound -box reproductionis entirely lacking.

Some explanation of this last ratherstartling fact is needed. For sometime past all the big gramophonecompanies have made use of electricalmeans of recording. The artiste whenrecording performs in a drapedstudio before a conventional " mike."He or she might be for all the worldin a B.B.C. studio. The sensitivemicrophone picks out a wealth ofdetail which the old diaphragmfailed to record. The detail is in themaster record, and it is in the com-mercial impressions, if only we canget it out.

Gramophone sound -boxes are notmuch improvement upon the dia-phragm recorders and that is whymany gramophone enthusiasts arestill blind to the full beauty ofthe lastest electrical recordings.Electrical recording means electricalreproduction in order to achievepurity.

Better than a Sound -boxThere are further reasons why a

pick-up, connected to a receiverwhich gives even moderately goodradio reproduction, can put a sound -box to shame.

Many of the electrical pick-ups onthe market are lighter in weight thansound -boxes giving anything likeequal resu lts . Heavy sound-boxesleadto slipping of the record on the turn-table, and cause a most unmusicaldropping of pitch when, say, asoprano reaches a vigorous high note-that is, when the needle reaches adeeply engraved wave form.

A pick-up does not wear a recordso much as a sound -box, because,volume for volume, a pick-up needleis a relay of energy from the H.T.battery, whereas a sound -box gene-rates sound -waves from movementwhich the needle must obtain fromthe record impressions.

Good "Radio" Set EssentialIt will be assumed, naturally, that

if you have a pick-up and are dis-satisfied with the results it gives, youhave tested the set to which it is con-nected. Good radio reproduction is anecessary preliminary.

The following two hints are theresult of experience with pick-upswhich have been believed faultyowing to incorrect methods of usingthem :

Before using a record, brush over itwith a velvet or similar soft pad.

Avoid handling the faces of records,for the composition of which theplates are made readily absorbsgrease. 2 BZL

Why Not Build the Gramo-Radio Four? See page 337

314

Wireless Magazine. May 1928

r.-Igranic Phonovox2.-Brown3.-Amplion Vivavox4.-Marconiphone5.-Lissen6.-Woodr uffe (marketed

by Celestion)

7.-Magnum8.-Gecophone9.-Dubilier

(electrostatic)

315

Wireless Magazine, May. 1928

There Can Be No Better Recommendation for the "W.M." Than

What Rea dersThinivOlifSetsThis is the

Astral Four,described

in theFebruary

issue. It hasenclosedbatteries

r,...._ ...,__ASTRAL FOUR

AS one of the few four-valvers publishedup to that time that would receive on both

wavelength ranges without changing coilsthe Astral Four (WIRELESS MAGAZINE,February, 1928) proved a great success.Here is what a Heckmondwike readersays:

Have just built your Astral Four aslaid out in. your February issue. Atruly wonderful set; can get anywhere.A station at every point on the shortwaves and a multitude of stations onhigh waves, all at loud -speaker strength.

Valves used are 2 -volt and the H.T.is supplied from an eliminator.

I can safely recommend the above asa good searcher of the ether.

Another reader at Hindhead has beenjust as successful :

I think you might be interested tohear my experiences with the above -named set-I haire received 38stations at good loud -speaker strength,namely :

Aberdeen, Barcelona (both stations),Bournemouth, Berne, Breslau, Cardiff,Cologne, Copenhagen, Dublin, Daventry(5XX and 5GB), Frankfort, Hamburg,Hilversum, Kalundborg, Cattowitz,Konigsberg, Konigswusterhausen, Kiel,I.angenburg, Leipzig, London (2L0),Lyons, Malmo, Manchester, Milan,Madrid, Muenster, Munich, Newcastle,Nuremberg, Prague, Paris (Ecole Super-ieure and Radio Paris), Stuttgart,Toulouse and Vienna (Rosenhagel).

I find where I live in Surrey that aneast -west aerial gives the best results,and also that even using 15o volts forthe H.T. 2 I do not get good

results with more than -6 volts totG.B.-2, and -3 volts for G.B.-r.

The set is loudest on tapping No. 4 ofthe coils, but most selective on No. 6.I also find that on the long -wave bandall stations take full reaction and proposeto try a .00005-microfarad condenser inparallel with the reaction condenser.

In conclusion I should like to say thatI am more than satisfied with this veryremarkable circuit.

P.S.-Since writing this this evening,I heard on the loud -speaker the otherstation at Lyons (La Doua-477.7

and Tangier, this bringing the totalnumber of stations up to 4o.

1927-1928 FIVESAlthough the 1927 Five was described

so long ago (WIRELESS MAGAZINE,October, 1927), and has been supersededby more recent designs, we still receiveletters regarding its good performance.Here is one from an Edinburgh reader :

It may be of interest to you to knowthat for the past fifteen months I havebeen using the 1927 Five receiver whichwas described in your magazine. Up tothe present I have logged forty-eightstations, including Schenectady, all ofwhich have been received at full loud-speaker strength, weather conditionspermitting.

I may also mention here that the.stations I have logged do not includeany of the high -wavelength stations as Inever wound coils for same.

This reader might be even better pleasedif he revised his set on the lines of the 1928Five as a West Newport reader has done :

Just a note to let you know the resultsI am getting from the 1928 I have built.I have revised my old 1927 Five andif any owner of the " 1927 " takes myadvice he will change it at once. The"1928" is far superior to the old set,and very easy to control, better tuningand better tone. I have tested it andget stations by the dozen, without anysign of oscillation, all barging in on theloud -speaker.

I won't look for a better when I havethis. It is a "Champion," and I thankyou very much for as good, if not better,a set than any I've heard.

316

" SIMPLER WIRELESS " SETSReaders fortunate enough to have a

200 -volt D.C. supply in their houses havehad many problems solved by using one orother of the " Simpler Wireless " sets des-cribed in these pages (WIRELESS MAGA-ZINE, October, November, December, 1927and February, 1928). A Birminghamreader makes some interesting comments :

I have built every " Simpler Wireless "set which has been published, and nowhave in use the Metropolitan Three, whichI consider the best of them all. Hum isalmost nil and less than in the othersets.

I have dispensed with an earthconnection as it does not make theslightest difference.

Purity of reception is excellent andcould not be improved upon. I am morethan satisfied and hope you will soongive us a five -valve set, but if you do,please arrange a switch to cut out thelast valve as volume would be too greaton the Daventry's (my local's).

A Shrewsbury reader is equally en-thusiastic about "Simpler Wireless"sets :

As a very satisfied reader of theWIRELESS MAGAZINE, I feel I should liketo congratulate you and Mr. Johnstonon the success of the "Simpler Wireless"system so far as I am concerned.

For experiment I built the Mains -fedTwo, and was delighted with the sim-plicity of the arrangement and withresults.

Desiring more power, I converted sameinto the Metropolitan Three, and am farfrom disappointed (particularly whenthe local ' lemon' juice is taken intoconsideration).

We are a goodly distance from theB.B.C. stations and so, of course, I havenot yet hit upon the ideal " SimplerWireless" set for my requirements. Ihope, therefore, that more receivers byMr. Johnston will soon appear, par-ticularly now moving -coil loud -speakersare appearing.

EXHIBITION FIVEThat "star" set of the autumn, the

Exhibition Five (WIRELESS MAGAZINE,October, 1927), has given great pleasure toa large number of listeners. Here is aletter from an Exeter reader who isgetting good results :

I have now finished the ExhibitionFive and incorporated a valve in parallelin last stage; it is very fine indeed. Weare only using B.B.C. wavelength atpresent. The results are equal toexpectation, to say the least; pleaseaccept my thanks for the set and helpyou have given me. I am most grateful.

You will understand it was notexactly simple for me when I tell youthat this is the first set I have builtmyself (I have always paid an electricianto build my others), but I have done itcompletely by myself and incorporatedthe tone -filter control with it.

We are anxious to get the Daventrycoils, as we expect something out of theordinary with them. Morse and sparkspoils the short waves here very much.

I have inserted my milliammeter; itregisters 14 milliamperes with about14 volts grid bias and is steady as a rock.

While I am writing this, 5GB is fillingthe room with the Royal Air Force Bandto perfection through the moving -coilloud -speaker.

Another reader in Manchester has beenable to get American stations direct. Hesays :

When I was endeavouring to getMadrid at 12.10 on Sunday morning(March 4), I was surprised to hear anannouncer speaking in English with anAmerican accent. Hence I tuned in asloud as possible and found the stationwas WBZ. Philadelphia. The details of theprogramme I give on another page . .

My set is in no way altered exceptfor valves. It is, in my opinion, a greatperformance by a great set, andheartily congratulate the WIRELESSMAGAZINE technical staff.

One reader in Bradford, owing to theuse of some wrong components, thoughthe had a " dud"-but he soon changed hismind :

After many thoughts concerning theExhibition Five, I have decided toforward my opinion concerning it. Itwill be about four months since Istarted construction on it. The wiringwas soon completed, but music, etc., wasreluctant to come through. Shortingoccurred, but where I could not discover.Solved at last in the vicinity of the jacks,it was put right. (N.B.-Excuse myignorance, as I had never had a jack inany set of mine previous to this.)

Now, thought I, for results. Neutralisingproved difficult, it being found necessaryto have all five valves going to hearanything. However, thinking I.had donethis, I prepared to receive them-that is,the countless stations. I got abouteight at poor strength.

This time it was wron,, coils, as allstations received had been between14o and 18o degrees on the aerial con- denser. I was just about in the fetch -a -hammer stage.

Well, the coils were exchanged, and I,not expecting anything worth mention-ing, popped them in. The resultsstaggered me, I had never heard a fivevalve set all out before, and it was some-thing of a shock to me the way they leaptin.

I am afraid I shall get blasé with toomuch of it. I can hardly fail to landsomething when I switch on.

I have burnt the midnight oil on twoor three occasions and have receeivedWPG, KDKA, WBZ; KOA, and

Wireless.Magazine. May, 1928

one or two others I could not catch.Europeans are as common as daisies.Success is mine as a copyist, and successbelongs to your paper as the designer.May the WIRELESS MAGAZINE live forever!

*REVELATION FOUR

Although it has since been supersededby more recent designs the Revelation Fouris a most successful receiver (WIRELESSMAGAZINE, August, 1927), and many arethe letters we have had in its praise. Hereis one from Halifax:-

Just a few lines to express my appre-ciation of the Revelation Pour, which Ihave had working now for two months,so as to give the set a fair test beforereporting on it to you.

I can receive the following stationseasily : Leeds, Bradford, London, Daven-try, Manchester, 5GB, Dublin,Newcastle,Langenberg, Berlin, Stuttgart, Hilver-sum, Oslo, Radio Paris, Hamburg, andseveral I cannot identify.

I must also congratulate the WIRELESSMAGAZINE Staff on the design and successof the set. I may say I am a raw noviceand knew nothing about wireless beforebuilding it, so beginners need not be

FULL - SIZE BLUEPRINTSof the sets mentioned in these pages can beobtained post free at the following prices :Astral Four No. W.M. 53 ls. 6d.1927 Five No. W.M. 6 Is. 6d.1928 Five No. W.M. 46 ls. 6d.Metropolian

Three - No. W.M. 48 Is. Od.Mains -fed

Two No. W.M. 37 1s. Od.Exhibition

Five No. W.M. 33 Is. 6d.Revelation

Four - No. W.M. 24 1s. 6dNomad Six - No. W.M. 31 Is. 6d.

Any of these blueprints can be obtainedon application to Blueprint Dept., Wire-less Magazine, 58/61 Fetter Lane, E.C.4.The half-price coupon is not available forany of these blueprints.

afraid to build their own sets from theWIRELESS MAGAZINE as everything isso clearly described and the blueprint isquite easy to follow.

I may say the first time I plugged inthe set worked and the volume scaredme; I was not expecting such a row. Toclose, I must thank you for a really goodfour-valver that does deliver the goods.Wishing the WIRELESS MAGAZINE everysuccess.

One Revelation Four is in use in aSwiss village, Davos Plate, and its ownerwrites :-

I wish to congratulate you on a per-fectly marvellous set, namely theRevelation Four.

I built this set in England and at thefirst test it produced about twentystations on the loud -speaker. Afterwards

when I brought it out, and made afew trifling alterations, imagine myamazement when I logged forty-sevenstations on the loud -speaker, includingLondon. Also I can sometimes getAmerica. Many other stations come ,inwhich are too numerous to mention.Wishing your paper all the luck itdeserves.

NOMAD SIXThe demand for a six-valver is, of

course, limited, but those who built theNomad Six (WIRELESS MAGAZINE, Sep-tember, 1927) have found it to be worththe trouble. A reader living at Leatherheadwrites :

I am by no means an expert in wireless.but to show the facility with which anovice may be able to construct one ofthe sets described in your magazinemay I state briefly my recent effort inregard to the Nomad Six ?

It is the first set of any kind I have everattempted to construct and, warned asI was of the magnitude and complicationsof the task, I have recently completed it,without assistance.

I tried it out on Saturday last, andwith an excellent outdoor aerial I was, Ican assure you, very agreeably surprisedwhen the set functioned with success atonce. I probably shall have some grid -bias adjustment to make and perhaps afew variations in H.T. voltages.

I have a good loud -speaker and thequality from the Nomad Six was excep-tional. Numerous foreign stations I wasable to get; in fact, they came in veryreadily, and in time I hope to identifythem.

As you say, it is a set to be proud of,and I agree.

Beginners do not often start their radioactivities with six valves ,but another reader,at Hornsey this time, made the Nomad Sixas his first receiver :

I constructed my Nomad Six just afterChristmas, and until I can run it fromthe mains I have been running it on twoIoo-volt batteries. They are just aboutfinished now, as the milliammeter shows'5 milliamperes on the last two valves,despite which both London and Daven-try (5GB) can both be brought in atuncomfortable loud -speaker strength onan indoor aerial 6 feet long. Langenbergand Breslau come in easily on an outdooraerial i i feet long.

This is the first set I have ever con-structed and it will be the last, as Iconsider this set is at least five yearsbefore its time. I do not think I shallever hear another set bring in foreignstations with such volume and purity.

The valves have shown great endurance,as when I first worked the set I con-nected the grid bias on the wrong waywith the result that instead of 24 voltsnegative bias, they got 24 volts positiveand burnt out the milliammeter. Thevalves show no sign of any harm, so I amstill using them, Thanking you for thefinest set I have ever heard.

Build A " WM." Set and Get Equally Good Results Yourself !

317

Wireless Magazine, may, 19281

Captain H. J. Round, the Well-known Pioneer, Discusses

.71E11111111111111111111111,

GETTFROM THE%

ivl RE POWERWEB VALVE

IN endeavouring to avoid distortionin the low -frequency circuits,

there has been a tendency to limitthe power that can be obtained.fromthe last valve. I have been working

Fig. 1.-Resistance-coupled Amplifier

out a few cases recently, and theresults will be interesting to manyreaders of the WIRELESS MAGAZINE.

Suppose we have a loud -speakerand in series with it we put a batteryand a make -and -break contact. Then,on making contact, a current willflow through the loud -speaker, thiscurrent being limited by the resistanceof the loud -speaker winding only.

If in series with the circuit we puta resistance, we cannot get as muchcurrent into the loud -speaker, andthe higher the resistance is the smallerthe current obtainable.

Greater Power OutputIt is obvious from this that if the

make -and -break contact and theresistance are replaced by a valve,then the lower the resistance of thevalve, the larger the maximumcurrent we shall get-that is, themore will be the power output.

If we replace the make -and -breakcontact with a valve plate -to -filamentconnection, then when the grid isgiven a high negative potential, wehave the equivalent of the contactbeing open, but if we make the gridpositive, this is equivalent to closingthe contact. The valve, however, hasa resistance which absorbs some of thevolts really wanted across the loud-

speaker, so that to some extent thetrue equivalent is the make -and -break contact with a resistance.

It is usually considered that gridsshall not be carried to a positivepotential because of distortion, but Ishall show presently that this is notan absolute necessity.

A Series of ValuesFor the moment we will consider

a series of valves in which we willstudy the resistance when their gridbias is just brought up to zero. Takethe three old standard valves, theDE5A, DE5, and DE5B. With thesame plate volts the DE5A will passa larger current at zero grid voltsthan the DE5 and the latter will givea larger current than the DE5B.

The valves have a very similarconstruction to one another, but theDE5A has a much more open gridthan the DE5 and the latter is moreopen than the DE5B.

The result is that we can get mostpo-A er output from the DE5A, but atthe expense of more input, for if theDE5A requires r o grid volts to reduceits current to zero, the DE5 will only

1-1 L.F.VALVE VALVE

ATRANSFORMER B

MT.+

Fig. 2.-Transformer-coupled Ampl fier------_______ ................ V- .....require 5 grid volts and the DE5Bonly 2 volts.

The advantages of this conditionof no grid current are obvious-forno load is thrown on the previous

318

7-1TO X 0 XCONTROL

3.-Two Grids Interwoven

valve and we can use a resistance -coupled amplifier or a high -ratiostep-up transformer (see Figs. x and2).

There is, however, another way tosolve the problem, for if we studyFig. r carefully, we shall see that thegrid circuit of valve B, if a positivepotential is applied, becomes of lowresistance and drops the appliedpotential from valve A, rather

TO STATICQ12111,

PLATE

XOX0XOX,S1)OX0X0

seriously causing distortion ofsignals.

If, however, the valve A is of alow -resistance type, then, providingthe plate resistance rod is also oflow resistance, so that the valve A isreally being used at a low -resistancepoint, grid current can be permittedin valve B, the condition for effec-tively guarding against distortionbeing that the grid resistance of Bshall not ever be as low as theresistance of the valve A.

Accurately considered, of course-,the valve resistance, plus the plateresistance and grid leak, must betaken in parallel.

Another Action to ConsiderOf course, in this particular circuit

another action will take place, helpingto distort, and that is the chargingof the condenser from the grid cur-rent; and for this reason the simpleresistance -coupled amplifier is nottoo nice in the circumstances.

If we now examine Fig. 2 with ther to r ratio transformer, then theaction is primarily the same as inFig. r -that is, providing the grid

resistance of the power valve nevercomes as low as the anode resistanceof the previous valve, we are safefrom distortion, only in this case wehave not to worry about condensercharge.

Raising the RatioSuppose, however, we raise the

transformer ratio, say, to 3 to I-amore normal transformer-then theeffect of any grid resistance is greatlyexaggerated, and the valve beforethe power valve, would have to be

th the resistance necessary in theto i transformer case, and running

into grid current is hardly permissible.There are thus two main alterna-

tives for getting larger power out-put:

T. (a) To use an open -grid meshvalve, and a high " mu " resistance -coupled stage before it, or

(b) a 3 to i ratio transformer witha similar valve to the power valve.

In neither case is grid currentpermissible.

2. To use a medium -mesh valveand work from a similar valve througha i to i transformer, driving well upinto grid current.

If the second method is taken to theextreme, we can drive an open -gridmesh valve well up into grid currentand get the absolute maximum ofpower out of a valve of that size.

More Load on Previous ValveWe are doing this by throwing

more load on the previous valve.When using either the open -meshmethod or the second method ofdriving into positive grid currentwe lose magnification, and this willhave to be gained elsewhere in thecircuits.

I have calculated one particularcase the result of which calculationwill be interesting.The particular valveconsidered was theDEP6io, a normalpower valve. With a

to i transformeranother DEP6io willdrive this valve up to Jovolts positive grid swingwithout serious distor-tion, and with 120plate volts this willgive three times theamount of power tothe loud -speaker thancan be obtained if theideal condition of nogrid current is main -

98

if3 6o -E 5_34r 3

Wireless Magazine, may. 1928

15

10

5

Vg=0

7/

vg = -

0 50 100N.T. VOLTS

Fig. 5.-Characteristic of Valve as Tetrode

Vs= -10

Vg= -15

150

tained. Surely this extra poweris worth having, even at the expenseof some loss of overall magnification ?

In considering this problem, Iasked myself if there was any otherway of obtaining this large poweroutput from a valve without thenecessity of running into grid current,and I was able to get a valve madeto try an experiment of a very simplenature.

If the grid of a valve is made oftwo spirals-interwoven but insulated

Vg.

9

0

from one another, each grid being thesame distance from the filament asthe other one (see Fig. 3)-then it isquite easy to see that if one ischarged positively to, say, xo volts,then >co volts negative on the otherone will give the same effect as ifboth grids were at zero potential.

Composite Grid VoltageBut note the point that if one is

charged statically (with a battery)to, say, xo volts, then if the other one

used as the operatinggrid is brought just up.to zero, where its own

Vg=6

0 50 100

VOLT$Fig. 4.-Characteristic of Valve as Triode

319

150

grid current starts, thecomposite grid is reallyat 5 volts. We havesucceeded in drivinginto grid current with-out real grid -currentloss.

In the actual experi-mental valve made,with an expenditureof 12 milliamperes at48 volts on the staticgrid I could get eighttimes the power fromthe valve without

Wireless Magazine. may. 1928

Getting More Power from the Power Valve (Continued)

AMullardPowerValve.

running into grid current on theoperating grid, and there is no loss ofmagnification.

Paying with MilliamperesThus, insteadof paying for the power

output by loss of magnification, aswe have to do in the triode case, inthis simple tetrode we pay for thepower output with D.C. milliamperes.

For those interested in the questionfrom the characteristic point of view,I attach in Figs. 4 and 5 the charac-teristics of the valve as triode and asa tetrode with 48 volts on the onegrid.

' It will at once be seen frOm thesecases that a great deal more undis-torted energy is available in thepositive grid case ; the undistortedenergy in each case I have repre-sented as a triangular- area.

Difficult to MakeValves such as my experimental

one are difficult to make, because tointerleave two spirals and insulatethem from one another is too muchto ask the valve maker to do, butlet us see what will happen if we, putone grid outside the other one, as inFig. 6-which is quite a practicalthing to do.

Then in this case if the outergrid is the statically -charged one theinner grid will shield its action fromthe filament by a certain amount,so that more volts will have to besupplied to it to get the sameeffect as before.

Thus, in the simple interwoven -spirals case, 48 volts would be ampleto permit of large currentless gridcontrol, but if the static grid isremoved to a position outside theoperating grid, then the voltage mayhave to be raised to 120 volts, or evenhigher, to get the same effect; in thiscase some secondary effects willoccur which will have to be takenaccount of.

In general, however, it will bepossible to obtain the same big poweroutputs as in the simple interwovengrid case, if the necessary precautionsare taken.

If the static grid is placed insidethe control grid similar reasoningcan be applied. In this case largercontrol voltages and smaller staticvoltages will be the rule.

It is an interesting problem to tryand reason out what will happenif, starting with the static grid insidethe control grid, this is imagined asgradually passing through the controlgrid and then its mesh slowly closedup, as in the shielded high -frequencyvalves.

We have thus available threemethods of obtaining more undis-torted power from the power valve.

The first method is to open thegrid mesh so wide that large currentspass at zero grid volts, and thismethod is well known and in muchuse.

The second method is to bringinto action the power possibilitiesof the previous valve, give it somework to do, and drive right up intogrid current in the power -valve.(Both the methods gain output atthe expense of magnification).

Third MethodThe third method is to use a

special valve with an auxiliary grid,and with this obtain both big poweroutput and high magnification, pay-ing for it with milliamperes to theauxiliary grid.

Valves in which the static grid is

TOcIRTIDATIC

X XXXXX0 0 0 0 0 0 9.1

TO 0 0 0 0 0 0 0'`i,

COMTROI, X X XPLXATLX X X

FigEt.1136.-Two Grids, one arrangedoutside the other

PLATE

FILAMOIT

placed outside the control grid havesecondary actions which needarresting before the valve can beused to the best effect.

Those who have studied the actionof tetrodes such as the S625 will haverecognised that the curious character-istic, part of which is of negative -resistance character,will prevent thembeing used for power output purposes,but it is well known now that thisdefect can be renewed by the intro-duction of yet a further grid.

I shall have more to say about thisdouble -grid power valve in futurearticles in the WIRELESS MAGAZINE.

WHY YOU SHOULD USE ANTI-MICROPHONIC HOLDERS

Although modern valves are quitemechanically strong in themselves they canbe made absolutely safe in use by mountingthem in good anti-microphonic holders.These Lotus valve holders were screwed to

320

the back of a motor lorry which wasrun many miles over bad roads. Thevalves were in perfect condition after thetest. Here is a moral for portable -setconstructors !

LWireless Magazine. May. 19281

PoWe" NeedSpecialisedBroadcasts?ON the Continent it is claimed

that the Dutch stations broad-cast the most educational and special-ised matter. The language coursesare graded with great care and alistener can start on a new languageevery quarter. There are fourcourses in the English language atpresent.

From Hilversum and HuizenFrom Hilversum and Huizen there

are specialised courses on " Shippingfor Bargees and Their Families,""How to Make Handy Objects,"Stenography, Book-keeping, andEsperanto, in addition to dozens ofother subjects.

As a general criticism it is truethat the B.B.C. have not set out tocater for the specialist. There areplenty of casual and haphazard talkson most subjects, but no definitepolicy seems to be followed as is thecase in many other countries.

Recently, Milan gave a course oftalks on stamp collecting, indeed,one of the cleverest series that could

have been broadcast. The onlydanger of that course would be tomake every Italian a stamp collector.One talk on a subject such as thisleads no one anywhere. It wantsto be followed up by a series.

One of the Mid -American stationshas a series at present on " Careersfor Women." There are plenty ofarticles in our daily newspapers aboutchoosing careers for our daughters,but there have only been one or twocasual talks on the subjects from theB.B.C. studios.

Talks to be of any value will haveto be " specialised " and made sointeresting that the series will gripas the B.B.C. series on "Music andthe Ordinary Listener " has gripped.

A series on Morse Signals would beof great educational interest to theaverage listener, and these could bedemonstrated. There is no subjecton which the average listener is soignorant, and yet there is no subjectso systematicallyignored in the B.B.C.programmes.

A Canadian station has given a

series of talks on Morse although nolistener within a hundred miles of thestation can hope to get within strikingdistance of any sea for a few years,nor be troubled much by Morsesignals.

One French station broadcast aseries of very successful talks onFirst Aid a year or so ago. A Germanstation about the same time broad-cast a series on Aeroplane Construc-tion.

Talks on Building SetsAll round the programmes are

becoming more specialised. Perhapsthe day will come when the editorof the WIRELESS MAGAZINE Will beinvited to broadcast a series of talkson " How to Make a Wireless Set "from 2L0.

In any case it is specialisation thatwill pay and make us masters of a fewthings, instead of being bored withthe casual talk. In this matter atleast, other countries are giving thelead to us. What are we going to doabout specialised broadcasts? E.B.R.

SOME RADIO "BUGS ".f Imported icfarom

This is Low Pantenna,foundonly in the wilds of Labora-toria. His eves can detectanything, and he is holdinga Pendyne, a weapon againstthe tribe of Poo Receptionia

NOTE. - Thisis an actual cir-cuit diagram.

A Dry - batteryManufacturer'sImpression of a" B - Eliminator."(A B -Eliminator isthe American termfor a high-tensionbattery eliminator)

(Right).-The effect of pro-gress-the Radio Car

(Left).-The Ham's Cov-ered Wagon

q1'r.brl9 =01,1' -;

E*-tt, zs;t t tz. s

Parade of the Thoriated Soldiers :The Nine -in -line

The D.X. Hound : Observe the dis-tance -getting nose, the crystalline earsand last, but not least, his tales, which

pass all understanding

-"Radio News," New York

321

Wireless Magazine. May. 1928

A Very Cheap and Simple Two-valver for Short-wave or Broadcast Reception

TheCrusader

Designed, Built and Tested by the" W.M." Technical Staff

IN this article the WIRELESS MAGA-ZINE Technical Staff is able to

offer its readers complete construc-tional details of a very cheap two-valver that is equally efficient onboth the short wavelengths and onthe ordinary broadcastingwavelengths.

Actually its cost isabout 2 15S. (less ifsuitable alternativesare chosen) and itcan be put together and wired upwithin an hour or two, even by aninexperienced amateur.

Most of the components aremounted direct on a baseboard, afew only being fixed vertically onsmall ebonite supports.. Nocabinet is needed and everythingabout the set is easily accessiblefor experimental purposes.

Range and VolumeThe greatest possible range

and volume from a two-valverare ensured by the circuitemployed, which comprises a detectorand one stage of low -frequencyamplification. Leaky -grid rectifica-tion is used as this is more sensitivethan the anode -bend system, andmagnetic reaction is provided, theamount of feedback being controlledby a small variable condenser.

Advantages of Plug-in CoilsFlexibility of wavelength range is

obtained by using plug-in coils;those of the make used in the originalset are almost as efficient on the veryshort waves as they are on thenormal broadcasting wavelengths.

To combine sensitivity with easeof control, a special reaction arrange-ment is employed.

Everything possible is got fromthe two valves used by supplying theiranodes separately, so that each canhave just the right voltage on it. Gridbias is applied to the low -frequencyamplifier.

From these brief remarks it willbe evident to WIRELESS MAGAZINEreaders that everything possible hasbeen done in this receiver to getthe greatest possible efficiency, and

TheCrusaderready foraction

at the same time the cost of con-struction has been kept low.For Loud -speaker or Phones

The Crusader will, under all ordin-ary conditions, receive several broad-cast programmes on the loud -speakerand as for the headphone range, well,that is unlimited. With this set it isan easy matter to pick up the chiefAmerican short-wave stations and,with luck, it may even be possible tohear Australia.

Very few indeed are the sets that

A Cheap Two-valver with Unlimited Wavelength Range

322

can be claimed to be equally efficientover the whole working range ofwavelengths. In wireless simplicitynearly always means efficiency andthe Crusader is not the exception thatproves the rule.

Those who have been interested inthe remarks so farmade will be gladto " dissect " thecircuit diagram re-produced on thispage and see ex-actly how the re-ceiver is arranged.

CircuitNo doubt to

many readers thetuning arrange-ment will seem amysterious affair,but actually it is

Wireless Magazine, May, 1928

tuning coil. In this case the aerial is,of course, connected to the top ofthe left-hand coil.

For reception on the ordinarybroadcast wavelengths, sufficientselectivity can be obtained withoutthis aperiodic arrangement and in

.0005 -00Di

HT+ g

117+1

Here is the simple circuit of the Crusader,a cheap two-valver

11T-LT-

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quite straight -for-ward. Two coils are seen, side by side,with their bottom ends joinedtogether and earthed. Well, the twocoils are used only for reception onthe short-wave band, when that onthe left acts as an aperiodic aerialcoil and that on the right as the main

this case only the right-hand coil isused (actually, of course, this meansthat no coil is inserted in the otherholder). This coil, however, is of thetapped variety and the aerial isconnected not to the top end of thecoil but to a tapping.

1((O.0005

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This layout and wiring diagram of the Crusader can be obtainedfor half-price (that is, 6d. post free) if the coupon on page iii of

the cover is used before May 31

323

Either cen-tre -tapped ordouble -tappedcoils can beused, the latterbeing slightlymore selectivethan theformer. Norm-ally a centre -tapped coilwill give thedesired degreeof selectivity,but where theset is to beused within avery few milesof a broad-casting stationa double -tapped coil isadvised.

Rectifica-tion is carriedout on theleaky -gridprinciple asthis gives thegreatestpossible sensi-tivity. A.0003 -micro -farad gridcondenser isused in con -

r COMPONENTS REQUIRED1-Wood baseboard, 12 in. by 9 in.

(Picketts, Camco, or ReadyRadio).

I-.0005-microfarad variable con-denser (Bowyer -Lowe, Formo,or Raymond).

t-.000i-microfarad reaction con-denser (Peto-Scott, Success,or Igranic).

i-On-off switch (Lotus, Lissen, orBulgin).

3-Ebonite supports, two 21/2 in.by 2 in. and one 4 1/2 in. by 2 in.(Becol, Will Day, or Raymcnd) .

1-Terminal strip, 6 in. by z in.(Becol, Will Day, or Raymond).

3-Single coil -holders (Lissen, Lotusor Magnum).

2-Anti-microphonic valve -holders(W. & B., Lotus, or Benjamin).

I-High-frequency choke (Wearite,Magnum, or Igranic).

I-.0003-microfarad fixed conden-ser, upright type (Lissen,Dubilier, or Marconiphone).

I-2-megohm grid leak with holder(Lissen, Dubilier, or Mullard).

I-Low-frequency transformer,ratio approx. 4 to 1 (Igranic,type F, Marconiphone Junioror B.T.H.).

I-Pair grid -bias battery clips(Deckorem).

8-Terminals,marked:Aerial,Earth,L . T . + , L. T. - , H . T . -I- 2 ,H.T.--1, L.S.-F, L.S. -(Eelex).

3-Short lengths flex (Lewcos).2-Wander plugs, red and black

(Clix) and spade tag.3-2 ft. lengths insulated wire

(Glazite).1-Set of short-wave coils (Atlas or

Igranic).2-Tapped aerial coils, Nos. 6o and

15o (Atlas, Lissen, or Igranic).2-Untapped coils, Nos. 5o and

ioo (Atlas, Lissen, or Igranic).

01111=11.1.01MM

junction with a 2-megohm leak, oneend of which, it should be speciallynoted, is joined to low-tension posi-tive and not to low-tension negative,as is sometimes the case.

From the anode of the valveenergy is fed back to the gridthrough a reaction coil and condenser,the latter controlling the amount offeedback.

Choice of High -frequency ChokeParticular note should be taken of

the fact that reaction will be unobtainable and the set will be veryinefficient if the high -frequency chokeinserted in the detector -valve anodecircuit does not function efficientlyover the entire waveband on whichit is intended to carry out reception.

To a considerable extent the volumeobtained from the Crusader will de-pend on the choice of a suitable trans-former. If purity of reproduction

Wireless Magazine. may, 1.92t11

The Crusader (Continued)

The Crusader fromthe back

is the main con-sideration then atransformer of rationot higher than 3 %Or 4 to I should beused; if purity is notof principal import-ance a considerableincrease in volumecan be obtained byusing a transformerwith a ratio as highas 7 % to I if a low -impedance detectorvalve is employed inconjunction with it.

As far as possible,however-and thisespecially applies tobeginners who havenot yet been reading the WIRELESS MAGAZINElong enough to have learnt most of the ropes ofthe radio game-all constructors of the Crusaderare urged to use identical components to thosebuilt into the original design.

Novices Assured of SuccessThey have undergone test and we know

quite definitely that if the original iscopied exactly even the novice is assuredof success and satisfaction with theCrusader right from the start.

On page 323 appears a list of all thecomponents required. The names thatappear first in the brackets are those ofthe manufacturers whose parts were usedin the original set. The other names are

This planview of theCrusader shows howwell spaced all the parts are

Here is the Crusaderwith valves and short-wave coils all ready

for use

324

those of manufacturers who make suitablealternatives that theWIRELESS MAGAZINEcan safely recommend.

As soon as all the parts have been gottogether --and it is advisable never tobegin work until this stage is reached-theconstructor can lay out the receiver.

Full-size Blueprint AvailableThis part of the job, as well as the

wiring, will be greatly facilitated for somepeople by the use of a full-size drillingguide, layout and wiring diagram, whichcan be obtained as a blueprint for half-

price, that is, 6d. post free, ifthe coupon on page iii of thecover is used before May 31.

Address your inquiry toBlueprint Dept., WIRELESSMAGAZINE, 58/61 Fetter Lane,E.C.4, and ask for blueprintNo. WM69, which will beposted off by return.

No difficulty will be experi-enced in laying out thereceiver; all the parts areclearly indicated on the blue-print and in the reducedreproduction of this whichappears on page 323. It willbe observed that each terminalpoint is marked with a smallletter of the alphabet; theseletters indicate which pointsshould be connected togetherand in what order.

For example, all thosepoints marked a are first

Wireless Magazine May: 1928

A Two -valuer Costing 2. 15.0connected together with one wire or as few wires aspossible; then all those points marked b should beconnected up; and so on through the alphabet.

As soon as suitable coils and valves have been insertedin the appropriate holders the Crusader can be given arough test.

Choice of Suitable Valves and CoilsA list of suitable valves is reproduced on page

326, but it may be further noted that thedetector valve should have an impedance of theorder of 15,000 ohms, while the low -frequencyamplifying valve should have an impedance ofthe order of 5,000 ohms or so. These values arevery approximate and differences of severalthousand ohms are permissible in making achoice.

Suitable coils for use with the average outdooraerial are indicated in the list of components onpage 323, but these sizes may not coverthe desired waveband with theparticular aerial in use.

Remember thatfor reception on theordinary broad-casting band ofwavelengths onlytwo coils are needed;these are a tappedaerial coil and a re-action coil. Either acentre- or double -tapped aerial coil canbe used, depending

Another view of theCrusader, all ready foruse, with short-wave

coils

325

(Above):The

Crusaderready for recep-tion on the broad-casting band of

wavelengths(Left) : Anotherview of the Cru-sader showingthe neat layout

upon the degree of selectivityrequired (a double -tapped coilis more selective than acentre -tapped coil) and

usually the reaction coil can bea size smaller than the aerial coil.The coil -holder nearest the edgeof the baseboard will not be usedfor reception on this band ofwavelengths.

For Short -Wave WorkFor reception of the very short

waves a set of special short-wavecoils should be obtained, but inthis case a very small aperiodiccoupling coil should be inserted inthe holder nearest the edge of thebaseboard. The flexible leadsoldered to the main aerial terminalwill also be connected to one

Wireless Magazine. May 1928

The Crusader (Continued)

VALVES TO USE IN THE CRUSADER

Make.Detector. L.F. Amplifier.

2 -volt. 6 -volt. 2 -volt. 6 -volt.

1321oL - .13215P B4

Burndept ... HL2r3 - L235 L525

Cossor ... ... 2 foLF 6ioHF 22oP 6ioFP

Cosmos ... ... SPi8G DE5o SPI8RR SP5oR

Ediswan ... GP2 ES5LF PV2 PV6ro

Marconi ... HL2ro DEL6ro DEP215 DEP6zo

Mullard ... ... PMLLF PM5X PM2 PM6

Osram ... ... HL2to DEL6ro DEP2t5 DEP6ro

Six -sixty ... SS2 roLF SS6o75HF SS2 r5SP SS6ioP

terminal of this holder and not to atapping on the aerial coil as is thecase for reception on the higher bands.

To test the set, push in the on -offswitch, place valves and coils inposition, and connect up the batteriesand a pair of headphones or loud-speaker. To H.T. I apply about 6oto 8o volts and to H.T.± 2 apply 120volts or more. The grid -bias batteryis mounted direct on the baseboardand should be so arranged that about6 volts negative is applied to thegrid of the amplifying valve.

Before tuning -in pull out thefilament switch to put the set on andmanipulate the reaction condenseruntil a slight rustling or hissing soundis heard which indicates that theset is "live." Now turn the knob ofthe main tuning condenser until atransmission is picked up.

Is yourWavemeterAccurate?

MOST people believe that ahetero-dyne wavemeter must neces-

sarily be more accurate than one ofthe simple buzzer type. It would bemore correct to say that an accurateheterodyne wavemeter gives moredefinite readings than a buzzer meter,but the latter is often more accuratethan the former.

Not Much to Go WrongThere is not much in the buzzer

itself which can possibly go wrong,and provided that the coil and con-denser are mechanically constantthere is no reason why a buzzer metershould be inaccurate, or fail to main-tain its setting. The trouble is thatthe buzzer note is not sharp enoughto give a definite and easily -readtuning setting, for the "buzz" canbe heard over a wide band of wave-lengths.

In a valve -oscillator neterodynemeter, on the other hand, the tuningis sharp enough for all ordinarypurposes, but the meter may lose its

" tune." The principal cause oftrouble is that battery values mayalter, and so upset the readingobtained. If a new valve is substi-tuted for the one with which themeter was first calibrated, re -cali-bration will be necessary.

The most that can be done toprevent battery values altering is toplace very large fixed condensersacross both the H.T. and L.T. inputterminals. The condenser across theL.T. supply will not, of course,make up for a discharged accumula-tor ! But it will compensate fortemporary minute irregularities.

Particular attention should be paid

IIIPAAAAAJAJAAAAAAAAAAAA&A.63

DO NOT OVERLOOKTHE SPECIAL " GRAMO-RADIO " ARTICLE ON

PAGE 314IIVYVVY'VVVYTTVVYVVIrri-VVYYMI

to all contacts, for any dirt or loose-ness will upset current flow. Valvelegs and sockets are particularoffenders in this respect.

No really accurate heterodynemeter is complete without H.T.volt and milliampere meters to showup any variations. F. B.)

AreMains -operated

Receivers Risky?WAR too dangerous for me," says11: many an amateur when you

mention the subject of H.T. fromthe mains. The kind of " danger "to which he refers is, of course, thedanger of blowing mains fuses. Fromthe point of view of the danger ofburning out valves H.T. elimina-tors are safer than dry batteries oraccumulators.

Small Maximum CurrentThis is the reason : The maximum

current that an eliminator designedfor a two- or three-valver can pass isabout 15 to zo milliamperes. This isnot sufficient current to cause adull -emitter to function, so " burning -out" is quite impossible.

H.T. dry batteries and, more par-ticularly, H.T. accumulators candeliver a current of an ampere orso (for a very short period) and thiscurrent might do much damage, ifill -directed, before it dies down

M. B.

All About Moving -coil Loud -speakers Next Month

326

Wireless Magazine. may. 1928

1- .Noteu3 withthe PAtoieemot

A CHAT ON PURITY

It

DO you know, Professor," saidyoung Amp one day in a medi-

tative sort of way, " I believe thistalk about purity is bunkum. I wasat a concert the other day-Mumand Dad took me-and it was thefirst time I had heard any bigorchestra playing."

"Did you enjoy it?" queriedMegohm.

Different by Wireless"Well, yes, I did in parts," was the

reply. " I got fearfully bored withsome of it, but there were other bitswhich I enjoyed quite a lot. But,funnily enough, they played a piecewhich I had heard on the wireless onlythe day before and it was quite diff-erent."

" It probably would be," said theProfessor. " Shall I tell you justwhat differences you noticed? "

Amp eyed the Professor with hismouth open. " What do you mean,Professor? " he exclaimed. "How onearth can you tell me what I noticed ?-unless of course, you were thereyourself-but then I never told youwhere I had been."

Megohm smiled. " No, I was notthere, but nevertheless, I can tellyou the principal points which shouldhave struck your attention. Younoticed, first of all, I expect, that thestrings --I mean the violins andviolas-appeared to have quite adifferent quality. You probablynoticed that there were severaldifferent kinds of instruments in thewood -wind, as it is called; theclarinet, oboe, and flute, for example,all of which had a distinctive qualityof their own."

"New " Brass InstrumentsHe looked inquiringly at the Amp,

who was standing there with anexcited look in his eyes and as soonas the Professor ceased he burstforth : " Well, that's extraordinary.Those are the very things I was going

to tell you-only not so poshly-ands'matter o' fact, there seemed to bean awful lot of big brass instrumentsthat I had never heard of before.

"Exactly," agreed Megohm, "youwould notice just that effect. Indeed,this aspect of the question is veryoften more striking than the other.As soon as the concert hall is enteredone is conscious of an atmosphereentirely lacking in the ordinary set."

" In any set, I should think,"interrupted the Amp, scornfully." I have never heard a set which wasa patch on the actual concert thatI heard the other night."

" The peculiar throbbing of "-the bass is difficult to er-

0 11 voLrAcE5xvELOPev

I HERE

The Professor's Sketch

reproduce with the simpleset and it is only occasion-

ally and with rather special sets thatyou obtain anything like this effect.It can be done, as I will show you pre-sently, but with the,average receiverit is not possible. We can differen-tiate, however, between varioustypes of instruments on quite asimple receiver provided we takethe trouble."

"You mean by the use of somespecial circuit? " queried the boy.

" By the use of forms of couplingwhich will reproduce with reasonablefidelity. Music is made up of funda-mental notes and harmonics. If youplay a note on a flute and the same

327

note on a violin, the two will appearquite different. You can even obtainquite different qualities with thesame instrument, such as a violin,according to how you play it. Thefundamental note is the same ineach case, but the quality is changedby the number and strength of theharmonics."

Harmonics Explained" What's a harmonic, anyhow ? "

interrupted the boy." An harmonic is an oscillation or

vibration occurring some definitenumber of times as fast as the funda-mental. The simple harmonics aredefinite multiples of the fundamental,their vibration rates being 2, 3, 4, ormore times as rapid. We also haveovertones,, which are non -integralmultiples, intermediate between theactual harmonics, but which never-theless bear a definite relation to thefundamentals."

The boy eyed Megohm a littledoubtfully and seeing this, the Pro-fessor raised himself from his chair,and said, " Come over here and I willshow you something."

He walked over to the corner of thelaboratory, where there was a longinstrument mounted in a metalcase. This he switched on and con-nected a cone loud -speaker to the out-put terminals. Adjusting one or twodials, he produced a curious whistlefrom the loud -speaker.

Producing a Pure Note" There," he remarked, " you have

a pure note."The boy looked at the instrument

in surprise and then looked hack atthe Professor. "A pure note didyou say ? " he exclaimed incredu-lously, " Why, it sounds the funniestsort of noise I have ever heard."

"It probably does sound funnybecause there are precious few instru-ments which produce a pure note.Nearly every note has harmonics.

I Wireless Magazine, may, 1928

Half Hours With the Professor (Continued)

Now I can introduce harmonics intothis oscillator without altering thefrequency of the note," and, here heproceeded to make certain alterations.The boy listened in amazement asthe character of the note changedat each adjustment. At one momentit sounded like a violin, at anotherlike a clarinet, yet all the time thenote itself remained the same.

Changing the Quality" I won't bother you," said Megohm,

as he smilingly shut off theoscillator, " by telling you exactlywhat I was doing in each case, you butwill see that by introducing harmon-ics I could change the quality of thenote altogether. That is what youhave to look after in a wireless set.In order to do that you have tr,arrange to amplify all frequenciesto the same extent and this is verydifficult to do."

"What sort of frequencies do wehave to use then ? " asked youngAmp, by now thoroughly interested.

" The full audible range extendsfrom about 25 or 3o cycles per secondup to zo,000 cycles per second,which is an enormous range to coverand very difficult of attainment. Anaverage horn loud -speaker will notreproduce frequencies much below200 cycles per second-that is to say,that it will not radiate them properly,although you can hear them if thatfrequency only is applied to theinstrument."

" How do you mean ? " broke inthe boy.

Lost in the Rush" I mean that if you applied a

frequency of 5o cycles to an ordinaryhorn loud -speaker, you would heara note, but if you played some musicin which some 50 -cycle frequencywas included, the loud -speakerwould not give the 50 -cycle note intrue proportion and it would bepractically entirely lost behind theother music. Is that clear? "

The boy nodded. " How much is5o cycles, anyhow ?" he asked.

" Two octaves below middle C is56 cycles," was the reply. "Toresume, it is clear that with theaverage horn loud -speaker, there islittle point in reproducing frequenciesmuch below 200 cycles, and the ordin-ary transformer -coupled set doesn't.

We can, however, obtain greaterfaithfulness if the upF2,1- frequenciesare corrrectly amplified. A poortransformer will commence to fall offin its amplification at 2,000 or 3,000cycles per second, which means thatthe high harmonics are not correctlyreproduced. It is these which willgive the distinctive quality to thedifferent instruments."

" Well," said the boy, "what aboutresistance -coupling? "

" I was coming to that," answeredMegohm. "We can obtain thequality we want either by increasing

AAAAAAAAAAAA1 AAAAAAAAAAA

DON'T FORGET THAT YOU4 CAN OBTAIN A FULL-SIZE BLUEPRINT OF ANY ONE

SET OF WHICH THE CON -

a STRUCTION IS DESCRIBEDa IN THIS ISSUE FOR HALF -4 PRICE BY USING THE COUPON ON PAGE iii OF41 COVER BEFORE MAY 31.4 MYTT'IVYTV`frirYTTPTYVY

the qualities of the transformer,which usually means making a verymuch more expensive instrument or,alternatively, by using resistance orchoke coupling. With resistance -capacity coupling, we have a resis-tance in the anode circuit of thevalve. Since the value of this resis-tance is constant, irrespective of thefrequency, the amplification from thevalve should be constant also at allfrequencies."

" Why do you say should be ? 'It is constant, isn't it? "

" No, there are two effects whichprevent it from being constant. Thefirst of these is the fact that thevoltages developed across the resis-tance have to be transferred to thenext valve through a couplingcondenser. See," he continued, seiz-ing a piece of paper and drawingthe rough sketch reproduced onpage 327. " We apply a voltageacross the grid and filament of thevalve and this causes varying cur-rents to flow in the anode circuit.These varying currents in turnproduce voltages across the resis-tance which are then transferredto the grid of the next valve.

" We do not wish to transfer thesteady high positive potential fromthe high-tension battery, however,

328

because this would polarise .the gridof the next valve and make it refuseto work. So we isolate the secondvalve as far as steady currents areconcerned by inserting a large con-denser. At the low frequencies, how-ever, the impedance of this condenserbecomes appreciable, and there is acut-off produced due to this effect.In average use, however, this cut-offis not important."

" What sort of values do you wantthen, Professor? " asked the lad.

Values of Resistances"It depends upon the resistances,"

was the reply. " Here," he continuedscribbling some figures on the bot-tom of the paper. "These are somesuitable values for you, so take thispaper and keep it. (See diagrams onopposite page.)

" You notice," he resumed, " thatI have not included any very highvalues of anode resistance. It hasbeen found that using very highvalues the capacity across the resis-tance begins to take effect much tooearly. There is always some capa-city effect and this begins to cutoff the very high frequencies or over-tones which we are anxious to pre-serve. Consequently, we must limitthe value of the resistance in orderthat this cut-off effect does notbecome serious within the audiblerange."

" Then, I suppose, it is also import-ant to avoid capacity in the circuitas far as possible? "

" Yes, you should wire your circuitcarefully in order to avoid anycapacity across the anode resistanceand also you should use a low -capacity resistance. The maxi-mum value satisfactory for reallygood quality is about 250,000 ohms,as I have given."

Ideal Form of Coupling?"Well, then, resistance coupling

seems to be the ideal form of coup-ling."

" It certainly has many advantages,but I do not know that I should quiteagree with that statement. There are,unfortunately, other factors to beconsidered, the principal one beingthe drop in H.T. due to the presenceof the resistance in the anode circuit.There is always a voltage drop pro-duced across the anode resistance by

Wireless Magazine. May 1928.

A Chat on Purity of Reproductionthe steady anode current so that thevoltage actually on the anode isalways less than the applied H.T.voltage.

" It is necessary, in order to obtainreasonable amplification of the valvethat the anode resistance should betwo or three times as great as thevalve resistance, which means that thevalve itself only has about one -quarter of the full voltage appliedactually to the anode."

" Oh, good heavens," exclaimed theboy. " That's rather a blow, isn't it?I mean, what's the good of wastingall the H.T. before you use it ? "

On this pageare shownthree differentcombinationsof valves fora resistance -capacitycoupled am-plifier, which,with the rightvalves, willgive purity

uriN1

" But lots of peopleswear by resistancecoupling, don't they,Professor? " Amp askedafter a pause.

"There is quite a lotto swear by in it,"answered Megohm,"but it is limited whenit comes to handlingfairly large volume andconsequently in thelater stages of a re-ceiver it 'a becomingcustomary to usedifferent formswhich

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of coupling " I thought you would say that '

give a char- smiled Megohm. "Can't you hearacteristic nearly,if not quite as

satisfactory, withoutthe serious disadvant-age of loss of H.T.voltage. Perhaps

some day Iwill tellyou the waythis is done,but youshall judgefor your-self of the

111.1mme

results."So saying, Megohm

walked over to another

" That is the most serious objectionto resistance -coupling and there isno remedy for it. In the early stagesof an amplifier we can afford to cutdown the H.T. and work with anactual value of 20 or 3o volts onlyon the anode, but in the later stageswe cannot afford this and we musteither cut down the anode resistanceconsiderably and lose a large per-centage of the amplification or wemust increase the H.T. so that thevoltage applied to the anode is ofthe order of ioo or 120 volts."

corner of the lab-oratory where the

Amp saw to his delighta bench model receiver.

" There is some ex-cellent music just

about to bebroadcast

now," saidthe Pro-

fessor, "in fact, ithas probably started."

As he said this hepressed a switch and theorchestra was heardclearly and with accur-ate definition of everyinstrument.

Neither spoke forsome time. Finally theboy said " But this iswitchcraft. Why, itwasn't any better thanthis when I heard it atthe concert itself."

329

the boom of the bass? Look," hesaid, " put your hands on the tablehere. You can feel the drummingof those double -basses and yet all thetime we haven't lost those upperharmonics and overtones."

+ MT.

FRMAtIOODE

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MEGOHM

MICA-DIELECTRICFIXED

CONDEASESc

TOGRID BIAS-

Again there was a silence untilfinally the Professor said : " Well,I'll tell you how to do it one of thesedays, but you must run along now,because I have got to go out for afew minutes," and with these wordshe bundled the sadly distracted youthout of the laboratory.

, ,

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FROMAtiODE

TO

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MEGOHM

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COMOLttat:I tka) 1311%f,-'4

1Wireless Magazine. May 1928!

A Revised Fable with a Moral for Experimenters

YjcArtiNciabat\!rEtVifiiii-succssIN the Golden Annals it is written1. that in the Sixth Year of theGlorious Reign of the AlmightyCaliph Rah-dee-oh (Peace be withhim !) there dwelt in the City ofSaa-voy an Aged Merchant, oneHassan-Ben-Azra, who for manyMoons had Honourably dealt inCostly Wares and Merchandise ofGreat Rarity.

It is said that he was Honouredand Respected by all his Customersin the Bezestein* ; by Virtue of hisSimple Honesty he had acquired agreat number of Friends, but hadalso made jealous Enemies.

Now it came to pass that on oneFateful Day there arrived in thisCity a Pedlar who had travelled greatDistances and who, albeit his poorAppearance and ungainly Carriage,did speak in a pleasant Manner andwith all the Attributes of politelearning. Whereupon, in the Bazaars,as it hath already been related else-where, did he sell Magic Crystals inrichly ornamented Caskets of sweet-smelling Wood by which theFaithful were enabled to hear thedistant Voice of the Muezzin from theThreshold of their Abodes.

And the Aged, but Honest, Mer-chant, wilfully misguided by thev.rongful Counsel of TreacherousRivals, did pay the Pedlar manyThousand Pieces of Gold in exchangeof which he was given a Quantity ofthese Devices with the Assurancethat he would by this means amassuntold Riches.

And Hassan-Ben-Azra, mindful ofthese Promises, did travel widelythroughout the Realms of the Caliph,and did visit many Large Cities tosell his Goods. But albeit he was ofVenerable Appearance, and enjoyedHigh Repute, his Wares did not meetwith Favour in the Eyes of the People.

" For," said the Merchants untohim, "of Magic Crystals have we seenCountless Numbers in the Past; thyadvanced Years have bedimmed thyWits. In the Bazaars can we show theeMagic Lamps which, by their Virtue,will encompass greater Wonders."

* Note by the Translator.-The marketsquare on which all merchandise wasexposed for sale.

It is even said that they counselledhim to betake Himself and his Mer-chandise to less congenial Climes, thewhich, in those Days of Peace, wasjudged to be a cruelly maliciousInvitation. Now, Hassan-Ben-Azrawas justly disappointed with the Ill -success of his Enterprise, and afterLong and Weary Journeyings, fraughtwith unpleasant Adventures, he didreturn to his Native City.

It is related that this Aged Mer-chant possessed a Son to whom he hadgiven the Name of Selim, whichmeaneth He who hath Brain Wavesby Night, and who was greatly Dis-tressed at the Grief his Father showedwhen recounting his Misfortunes inthe Bosom of his Family. On oneMorning, Selim addressed him thus :

"O Father, in your Great Wisdom,you have given me many Oppor-tunities to acquire Learning from theWise Men of our Land, and I haveprofited thereby; from my MastersI have gained all the Knowledgewhich befitteth a Successful Mer-chant. I conjure you to take me intoyour Business that I may relieveyour last Years of Grievous andOnerous Troubles."

To which Hassan-Ben-Azra didmake reply :-

" As my Father did unto me, sowill I act towards thee, my Son. Ifthou wilt prove worthy of my Trust,so will I agree to thy Proposal."

Selim, overjoyed at the Prospectof showing his Ability to recoup hisFather's Losses, did explain theStratagem he had devised in theNight Hours, and by which the MagicCrystals could be Sold without Delayfor a good Profit.

"To -morrow," said he, "I will risebetimes, and betake myself with twoSlaves to the Street in which theMerchants dwell. There will I giveto each Thirteen of these CarvedBoxes, saying to them that for theseTwelve Magic Devices I shall demandTwelve Pieces of Gold."

But Hassan-Ben-Azra, at thesewords, did show his anger.

" Thou Dolt," he cried, " whereforespeakest thou of Twelve, when thySlaves leave Thirteen at the Shops ofthe Merchants ? "

330

And Selim (He that hath BrainWaves by Night) did droop his leftEye as he answered : " 0 Father, doyou not see my Cunning ? These Mer-chants, who have ill-advised you inthis Venture, in their Greed, will buythe Thirteen Crystals, for they willbelieve that I have misjudged theNumber of Twelve; they will all payme the Twelve Pieces of Gold."

And it is related that Hassan-Ben-Azra was doubtful of the Stratagem,but that he enjoyed the'T hought thatSelim had Profited by his Teachings.

"If thou dost Succeed," he saidunto him, "then will I take thee into,my Business."

And so it came to pass that, atBreak of Day, Selim, with all theConfidence which Youth doth Possess,set forth from his Father's Abode,accompanied by Two Slaves and hisWares, and did visit the Bazaar, ashe had promised to his Parent. Andhe did leave . with each Merchant,Thirteen Magic Crystals encased inrichly Carved Boxes of Sandalwood.Also, it is said, he did give unto them,in his own Hand, a Tablet on whichwas written that for the TwelveCrystals he did demand Twelve Piecesof Gold.

On his return to his Dwelling,Selim passed the next Day in GreatImpatience; for, as he said to hisFather : " I have put you in the Wayto sell your Merchandise. As youhave promised me, so shall I shareyour Losses and your Profits.

But, on the following Morn, of theWily Merchants in the Bazaars, with-out exception, each returned TwelveCrystals with the Tablet written bySelim, saying unto him :--

"It is in vain we have sent Criersthroughout the Streets of this City ofSaa-voy; the Faithful will not buythese Wares.

And both Selim and Hassan-Ben-Azra did shed Tears of Disappoint-ment as they saw the Crystals re-turned to their Abode ; for it was madeclear unto them that each one of theirjealous Rivals had retained one MagicBox, for which he had not paid.

Moral : It is easiest to learn atanother's cost.

J. GODCHAUX ABRAHAMS.

Wireless Magazine. may, 1928

An Article of Interest to Every Valve -set Owner, by R. W. Hallows

HOEa Modal/live isMade"HE valve as we see it when it

I comes out of its box looks asimple enough affair. There is a glassbulb, usually " silvered " on theinside, a cap and four pins. Insidethe bulb, though the " silvering "often prevents us from seeing themclearly, we know that there arefilament, grid, and plate.

Round an Up-to-date WorksBut to make up a valve worthy of

the name entails the employment ofthe most skilled human hands andof machinery so ingenious that it isalmost uncanny in its action. I hadseen valves being made in the oldbright -emitter days, when the major-ity of the work was done by hand,but until a month ago I had not hadthe opportunity of going round anup-to-date works organised for massproduction.

When a well-known firm of valvemanufacturers were kind enough toinvite me to spend a morning at theirfactOry, the opportunity was clearlyone not to be missed and I haveseldom had a more interestingexperience.

Speaking broadly,thevalve passes throughseven main processesbefore, labelled andboxed, it finds its wayon to the shelves of thestore house, ready forissue to the dealer inwireless supplies. Theseprocesses are : (r) Mak-ing of the "foot," (2)assembly of the electrodes, (3) sealinginto the bulb, (4) pumping, (5)capping, (6) eddy currenting, and (7)final testing. Actually each of thesestages in its construction involves aconsiderable number of steps of whichwe shall see more in a moment.

Breaking Open a ValveIf you break open an old valve, as

you aay easily do by placing it under

water and tapping the glass gently,you will find that the electrodes aremounted upon a kind of pedestalmade of hollow glass. This is knownas the foot, and the top portion ofit, into which the electrodes and theirsupports are sealed, is called the pinch,for the very good reason that itactually is pinched flatin order to grip thevarious wires.

The foot starts lifeas part of a glass tubeseveral feet in length. Amachine whose founda-tion is a turntable isloaded with theselengths of tubing justas a slot machine isloaded with bars ofchocolate. When themachine is started, theprotruding end of thefirst length of tubing isTwo examples of valveswith indirectly heatedcathodes, for working fromelectric light mains. Thaton the right is the typemade by Marconi andOsman, while that below

is a Cossor

brought into a gas flame. Havingremained here for the necessary.number of seconds, it is automaticallymoved on to a second somewhathotter flame.

Meantime, of course, the nextlength of tubing is introduced to thefirst gas flame and so on. Havingbeen further heated, the first tubemoves on again and at this stage aflange is automatically made at its

end. It continues its journey roundthe turntable, being annealed andshaped in the various stages throughwhich it passes.

Finishing Off the FootThe exact length required is

measured off automatically and whenit reaches the last stagetwo revolving knives,one inside it and oneout, come into playand cut off the finishedfoot. As the inside knifedrops down, havingfinished its work, a puffof air comes through atube and blows the nowcompleted foot gentlyinto a basket that iswaiting to receive it.

The modern valvefactory is so arrangedthat during the processof itanufacture the

valve starts at one end,passes in its various stagesthrough the room and finallycomes out at the other endcomplete and ready forservice. All machines, too,are carefully regulated asregards their speed, so thatthe supply of valves in any

particular state is always equal to thedemand by those ready to carry outthe next process.

Electrode -supporting WiresFrom the foot -making machine we

pass to the bench, where the elec-trode supporting wires and the littleglass tube necessary for pumping outthe valve are placed within the glass.Special jigs secure dead -accuratepositioning. The foot with its wiresand tube travels round another turn-table upon which the glass is heatedonce more and finally given by a pairof metal jaws a pinch which sealseverything firmly into place.

Whilst the glass is hot and soft, a

All You Want to Know About Moving -coil Loud -speakers in the Next Issue

331

Wireless Magazine. May 1928

How a Modern Valve is Made (Continued)

PINCH WITHELECTRODESUPPORTS

GRID INP051TIOIY

Parts of a Mallard Valve

blast of air is blown through thesealed -in tube, causing a little holeto appear just below the pinch.Through this hole and the tube, allthe gases within the bulb will beextracted later.

At the Assembly BenchNext we came to the assembly

bench at which sat workers providedwith supplies of the various smallpieces which go to make up theelectrodes. It is surprising really tonotice how many of these little partsthere are-the filament, the griditself with its stout wire former, theplate, the top insulator, and the tinyspring with a hooked end whichstretches the filament into a V shape.All of these parts are made at separatebenches and brought across to thatdevoted to assembly.

One of the most delightful processesis that involved in grid making. Theoperator has in front of her a supplyof wire formers and a machine con-taining a mandril with a reel of finemolybdenum wire. The former isplaced on the mandril and one endof the reel of wire is hooked under alittle catch. The mandril spinsround, winding on the turns of wirewith perfect spacing. This done, theoperator draws a lever with her righthand, causing an electric spot -welderto travel over the windings. Eac aindividual turn is thus welded to tl testout wire of the former.

From One End to the OtherBut to return to the assembly

bench, which is so arranged that thework travels from one end of it tothe other. At the input end is anoperator who welds the ends of thefilament to their supports. From herthe foot passes to a colleague whowelds on the grid. It next travelsdown a sloping slide across the benchto a pair of operators who betweenthem nip off the end of the grid -former, place the seonite insulatorin position, insert the spring and passthe filament over its little book. Atthis stage the electrodes are care-fully examined to see that they occupyexactly their proper positions.

Another slide takes the valvefurther on its zigzag course to theoperator who welds on the anodesupports. Across the bench oncemore it travels for the final process

332

of assembly. The anode is slippedon and spot-welded and a smallpiece of magnesium wire is weldedto it.

So much for the foot and theelectrodes mounted upon it. Mean-time supplies of bulbs will be undertreatment at another bench wherethey are washed and afterwardsdried by warm air blown into themthrough pipes. Bulbs and completefeet meet one another for the firsttime at the sealing machine, again aturntable, upon which several pro-cesses are carried out automatically.

The foot is placed within the bulband a flame plays upon both. Stepby step the glass is annealed andbrought up to the required heat. Inthe final stage a perfect union be-tween the foot and the bulb iseffected and the lower unwantedpart of the latter is cut off by a hotflame.

Ready for PumpingThe valve is now ready for pump-

ing. Once more it is placed on aturntable of a particularly ingeniouskind. As it travels round theelectrical contacts necessary for bom-barding the anode are made auto-matically. Meantime wonderfulpumps are at work extracting everypossible atom of gas from within thebulb. In the final stage upon thisturntable heat is applied to the smalltube in the foot. Air pressure causesthis to collapse as it softens, forminga pip. In old-fashioned valves, thepip was always at the top of the bulb ;in nearly all of those made to -dayit is hidden within the cap.

Use of MagnesiumPossibly the reader has been

wondering why a small piece ofmagnesium should have been weldedto the anode in an earlier process.The reason is this : To all of themetal parts within the bulb clingsa minute quantity of gas whichcannot be extracted by any straight-forward process of pumping. Werethese occluded gases, as they arecalled, allowed to remain, theywould be given off when the internalparts of the valve heated up in use.There would thus be a softening ofthe vacuum and the valve wouldbecome useless, at any ' to foramplifying purposes.

Wireless Magazine. May, 19*

Every Valve -set Owner Should Read This ArticleDuring the first bombardment,

which is accomplished by lightingup the filament and applying a highvoltage to the anode, the latterbecomes red hot and gives out partof its occluded gases which areextracted by the pumps. The heatalso causes part of the magnesiumto volatilise.

Gases Taken UpWhen this happens the atoms of

the metal collect gas atoms whichthey carry with them to the glasswalls. The gases are thus occludednow by the metallic deposit withinthe bulb, and since in a dull -emitterthis never becomes hot, there is nofear of their being subsequentlyreleased. Not all of the magnesiumis, however, used up in this process.It has still a part to play as we shallsee later.

The next journey is to the cappingbench, where I witnessed a marvel-lous display of dexterity on the partof an operator. From the lower endof the foot there protrude the fourwires which form the connectionsto plate, grid, and the two ends ofthe filament. The valve pins arehollow, one of the wires having tobe passed through each. The opera-tor in question worked so rapidlythat movements of her fingeis couldhardly be followed.

In a moment she had straightenedout, scraped and cut to their properlength the four wires. Seizing a cap,she thread( 3 the four simultaneouslythrough their proper pins. Imaginethreading four needles at once andyou will have some idea of theastonishing skill involved.

Trying My HandWondering what sort of show I

should make, I asked to be allowedto try my hand. The operator per-formed the entire process in two orthree seconds; at the end of fivestrenuous minutes I was forced toown myself beaten I

Pressed into its cap the valvetravels round the turntable of abaking machine which hardens upthe cement securing the bulb inposition. The wires passed throughtheir pins are not yet soldered, forif this were done, any defect foundat a later stage would mean that boththe bulb and the cap had to be

scrapped. The wires then are merelylaid round the outsides of the pins.

Now comes a particularly interest-ing process. The valve is placed in aholder upon a very large turntablebeneath which are automatic electri-cal contacts which pass to each thecurrent necessary for ageing the fila-ment. At one point on the turntableis a spiral of stout wire which fallsoverthe valve,and remains embracingit for some seconds and then rises topass on to the next. This coil carrieshigh -frequency current supplied bya huge tube.

Eddy Currents in the MetalAs the valve is encircled by the

coil, eddy currents are set up in themetal parts within, causing them tobecome heated up until they glowbrightly. The last of the occludedgases are thus driven off, and whenthe heat reaches a certain point, theremainder of the magnesium volati-lises and takes charge of them.

Almost completed now, the valve isready to have its characteristicstested. It passes to a most ingeniousinstrument in charge of a skilledoperator. When it has been placedin the holder upon the instrumentone movement of a switch causesmeters to record the filament voltage,the filament current and the platecurrent at a given voltage with thegrid at zero potential. A secondmovement increases the plate poten-tial, leaving the grid still unbiased.

Further Stringent TestsWe thus have points on two

characteristics corresponding to dif-ferent plate potentials. Should thevalve fail to show almost exactlystandard readings it is rejected asfaulty. But the stringent test is byno means complete. A third move-ment of the switch applies a negativegrid bias of a certain definite amount,leaving the plate potential at thehigher value.

If the magnification factor of thevalve is correct, the plate currentshould now be the same as it was withthe lower plate potential and thegrid unbiased. Lastly, the plate andgrid are connected together by afourth turn of the switch and thetotal emission of the valve is readoff. The whole operation was com-pleted in a matter of seconds, but

333

r

STEM WITHELECTRODESIli POSITIONIN BULB

PLATEIN

POSITION

BULBSEALED

OVER

More parts of a Mallard Valve

Wireless Magazine. may. 1928

How a Modern Valve is Made (Continued)

it provides a most searching andreliable test.

With Flying ColoursWhen it comes through this test

with flying colours the valve passesto an operator who nips off the endsof the wires protruding from the pinsand presses the ends of the pins firston to a pad moistened with flux andthen into a shallow dishof solder kept molten byan electric heater.

But it has still twofurther tests to go throughbefore it can be passedinto store. In the first ofthese the hardness of thevacuum is tried, no valvebeing passed which showsany trace of ' softness.Next the insulation mustbe thoroughly tested. Itmay be imagined thatwhen the magnesium get-ter volatilises a little ofthe metal may be deposit-ed upon the pinch, thusforming high resistanceleakage paths betweenthe electrode supports.Were it allowed to re-main the valve would "play up"when in use in all kinds of queerways.

This magnesium is got rid of by aprocess of burning off. The valvehaving been placed in a holder, veryhigh potentials are applied firstbetween plate and grid, then betweenplate and filament and lastly betweenfilament and grid. These cause alltraces of metallic deposit upon thepinch to disappear.

Tested by MeggerHaving been treated in this way

the valve is tested by megger forleakages between any of the threeelectrodes. None is passed for saleunless infinite resistance is shownbetween these points.

All that remains is to gum theidentifying label on to the bulb andto pack the now completed valve inits cardboard box. This last processwas to me one of the most astonishingof all. The cardboard boxes now

used are supplied by their makersfolded flat. To assemble them theymust be pressed with the fingers intosquare shape and three flaps mustbe folded in at the bottom. When thevalve has been placed within the boxthree more flaps have to be foldedover at the top of it.

Only a few days before my visitto the valve works I had tackled the

job of setting up a coupleof these boxes from the flatand placing valves withinthem. I do not know quitehow long it took-certain-ly several minutes for eachand when the job was donethe box did not lookparticularly neat. Noticing,therefore, an operator with

Another type of mains valve-thatmade by Cosmos

a pile of boxes in the fiat besideher, I did not envy her her work.When I first saw her, she wasresting for a few moments whensuddenly she got to work again. Inthree seconds the flat box was squarewith all its three lower flaps foldedin as neatly as they could possiblybe. A valve was inserted, its accom-panying printed slip folded in andplaced above it and the three flapsat the top of the box folded down,before I had time to gasp.

The operator simply seemed towave her hands over it, and the boxerected and folded itself in somemagic way, the entire process fromstart to finish being accomplished inabout ten seconds.

Lastly, the valve passes into thegreat store when, in company withvast numbers of all kinds, it waitsready for the day when it will becalled upon to bring in speech and-music from distant stations in yourreceiving set- or mine.

Pressing theCrystal for

good Results!UNTIL experts succeed in finding

out how and why a crystaldetector works, the reason why somecrystals like a firm catwhisker pres-sure, and others a light contact, willremain a mystery. This catwhiskerpressure business is, nevertheless,important.

Firm Pressure NeededThose who have been converted

to the advantages of carborundum(using a small applied potential) willbe able to affirm that, although the

chief merit of carbor-undum is its constancyof operation, a constant,firm pressure betweenthe crystal and thesteel contact must bemaintained.

UpsettingCharacteristic

Apart from the factthat a constant pres-

sure is needed on all crystals, ifthey are to detect satisfactorily, thereis a further reason why constancy ofpressure is essential with carborun-dum. Any variation of contact willalter the extremely minute currentflowing through the crystal (thiscurrent, is, of course, the result ofthe potential applied) and so upsetits characteristics.

Coarse and Fine GrainsIn the case of galena -type crystals

-and many commercial detectorsare in the galena series-a firmpressure seems to work best with acoarse -grained crystal. Crystals oflighter grain require a somewhatlighter pressure.

Some spots on a crystal do notappear to be sensitive until a fairlyheavy pressure is applied by the cat -whisker point, while other areas donot detect at all if more than thelightest possible contact is made.

B. I. M.

Don't Overlook the Crusader-on Page 322 !

334

IF the B.B.C. were to broadcast arequest that all listeners wrote

out and submitted their own estimateof the amount of work required tobring one evening's programme tofruition, the response, supposingthere was one, would generally admitthat some work was necessary, butwould undoubtedly fail to take intoaccount many of the stages throughwhich every item has to be piloted.

Minimum of Six WeeksIf a programme could be built up,

rehearsed, and put on without a singlehitch, six weeks would be requiredto complete the process. As it is, somany unexpected difficulties arisethat this time limit is often exceeded.

In the first place it is obviouslynecessary to introduce new artistesfrom time to time, every one of whomhas to be given an audition beforehe can be engaged. There are onlyseven studios at Savoy Hill, and theresult of having so many calls uponthem is that they have to be reservedthree weeks in advance for bothauditions and rehearsals.

Furthermore, since there are manyparties doing the same kind of work,It does not always follow that it is

Wireless Magazine. may, 1928

Peeps Behind the Scenes

INCA

Brranko eff

141111114111441&16.,

On the left is seen Miss Norah Blaney at the piano,and above are the masts of the London station.

possible to reserve just that studiowhich is best suited to the nature ofthe turn.

A good story of auditions was oncetold me by Tommy Handley. Itconcerns his own introduction to themicrophone, and is so good that Iwonder he has not broadcast it beforenow. As he braced himself for hisordeal he was quite naturally feelingdecidedly nervous.

" When you have finished yoursong, Mr. Handley, I wonder if youwould be good enough to say some-thing funny. You know what I mean,don't you ? You know,-er, -er,something, -er, well, somethingfunny you know? " smilingly askedthe official in charge.

Unfortunately Mr. Handley farfrom knew, and when the dreadmoment arrived was dumb for severalseconds. At length the poetic musewithin him welled up, and quiteunconsciously he burst forth with :

Thirty days hath September, April,June and November,

All the rest have thirty one, ex-cepting February alone.

In the nervous collapse whichfollowed, he thought he had "tornit," as he said afterwards. In actualfact, however, he had unknowinglymade a singularly brilliant responseto the request to say "somethingfunny," and there was no questionabout his engagement.

A simple instance like this showsthe nature of these auditions. Imagine,

335

then, the official, having booked thestudio for, say, fifteen minutes,anxiously endeavouring in that shorttime to discover the suitability orotherwise of his nervous charge.

After the artiste has been engagedthe nature of his number has to besettled, and, of course, the date ofhis appearance. When a provisionalday has been arranged, a note is madeof it on the skeleton programme,which is never less than six weeksahead, and often three or four months.Care must be taken that popularsongs do not occur too frequently,and that the programme avoids thatdreadful complaint, "sameness."

Rehearsal!The next move is rehearsal, which

progresses in much the same way asmight be expected; those who havehad any experience of amateurtheatricals will need little enlighten-ment on this subject !

Before actual radiation takes place,however, many unforeseen thingsmay happen; items which were con-sidered certainties may have to bescrapped, while others, which wereruled out as impracticable, or possiblynot even thought of, suddenly presentthemselves.

To cope with such emergencies ithas been found necessary to providea special programme "referencelibrary " at 2L0, a room to whichanyone may repair when in doubt as

Wireless Magazine. May. 1928

Preparing a Broadcast (Continued)

to the proposed item for any stationat any hour of the day during theensuing three weeks.

All around the walls of the roomare twenty-one wooden frames,roughly two feet square. Eachrepresents one day's radiation, andas they are always full, the timecovered remains constant at threeweeks. As a day passes, so one frameis emptied and immediately refilled.They are divided into as manyhorizontal rows as there are stations,and the length from left to rightrepresents the whole of the broad-casting day, thus allowing two inchesor so per hour.

A Colour for Each StationThe rows are so constructed that a

piece of fairly stiff card may be fittedin quite easily. Every station hasbeen allotted its own distinct colour,and the origin of each item of theprogramme, whether its own studio,another or an outside hall, is indicatedby the colour of the piece of card. Afew brief informatory words of des-cription are written on, and it is cutto a width proportionate to the linelimit. For an S.B. or a relay anotherspecial colour is employed. One greatadvantage of this card system is thatalterations can be easily made.

Often a station will suddenly finditself unable to give an item, andheadquarters will be invited tosuggest an alternative. By a simplevisit to this reference library, detailscan be obtained of the whole day'sradiation throughout the wholecountry, and perhaps a substitutefound in another programme.

Special Items for S.B.On the other hand, it may happen

that a station director suddenly andsomewhat unexpectedly discoversthat he can provide an itemof outstanding interest, a " red-hot " topical talk for instance.Its nature may render impossiblea repetition, and he may con-sider it of sufficient importanceto merit an S.B. He at once com-municates with Savoy Hill, and again,one glance at the charts shows howmany stations are free to take anS.B., or possibly suggests a timebetter suited to this purpose.

When the day of radiation arrives

there still remains a considerableamount of administrative work to bedone. Perhaps it is not generallyknown that there are always twoannouncers on duty, the senior ofwhom is in complete charge of theentire programme. Any decisionsregarding alterations and so on aremade at his direction, and he is farmore than a mere mouthpieoe, thisbeing, in point of fact, a part of hiswork rather than his whole duty.01AAAAAAAAAAAAAAAAAAAAAAA

When You AreIn Difficulty-

It matters not whether yourknotty problem is a theoreticalor a practical one-in eithercase the Technical Staff ofthe " Wireless Magazine " isever ready to help you out ofthe difficulty.

Just write your query outon one side of a sheet of paper(this small point saves ustime and enables us to sendan answer quicker) and sendit with the coupon on page iiiof the cover, a stamped ad-dressed envelope and a fee of1s. (postal order or stamps) to :Information Bureau, "Wire-less Magazine," 58-61 FetterLane, London, E.C.4.

MITYVTVVVYYVVVYYVVVVVVVYYM

If a telephone message is receivedto the effect that a certain artiste isill, it is the announcer who decideshow his amount of programme timeshall be filled. If a relay is comingthrough from Sydney, he is listeningin the whole time, and should thequality of the transmission deteriorateseriously, the question of cutting itoff rests on him.

Announcer's Log BookNaturally he will consult The Control

Room upstairs, but nominally theresponsibility is his alone. This isnot all; before he leaves the buildingthat night, he must enter up a reportof the day's radiation in his log book,which is taken as his evidence when-ever an enquiry is held.

During the course of the day theperformance moves from studio tostudio according to the nature of thenumber, some needing a large room,and others a more intimate one. On

336

entering afresh studio the announcerat once gives the O.K. signal to theControl Room, which accordinglyswitches the microphone over, auto-matically lighting up a red lamp inthe studio, and another over theoutside of the door.

Recently, too, a third lamp hasbeen placed in the corridor imme-diately overhead. It was noticed thatpeople hurrying to and fro shook theceiling, and so interfered with thetransmission. The new lamp warnsthem to tread softly.

Another InnovationAnother innovation which has

been brought about is the installationof a pianist in the new studio, No. 6.Shi watches her red lamp, and themoment it jumps to life, starts toplay, stopping as soon as it diesaway. She has no other informationas to the length of time she may becalled upon, and has to use her ownjudgment as to what to play.

The reason for her presence is tofill in the gaps which will occur inthe best managed programmes, andto obviate those unpopular announce-ments, "will you stand by for twominutes, please." At 2L0 an O.B.is almost always on one of the pro-grammes. This is timed provisionally,but the B.B.C. often has no controlover it, and if it is late, simply hasto wait.

An ExampleIf, for instance, the O.B. consists

of an excerpt from a performance ina hall in Manchester, the engineersare on the spot, of course, and areconnected to zLO with a direct line.When the time for switching overdraws near, they usually enquirefrom the conductor of the orchestraby improvised signals. If he indicatesthat they are, say four minutes late,then the message is passed to theControl Room, and the waitingpianist forthwith instructed tocommence.

When the engineers are ready, thesignal is flashed along the line, thepianist stops, the announcer giveshis foreword, and the relay comesover. Finally, when the number isover the engineers disconnect fromtheir end, and give the last O.K.signal to London.

Wireless Magazine. May. 1928

Here are full constructional details of a fine set that will give music from the loud -speakerat any time of the day or night. It is capable of giving the choice of a number of radio pro-grammes and can be used for getting the best possible results from a gramophone when

wireless offers nothing to the operator's taste

SW ITCHFOR.

RADIOOR.

GRAMOPHONE

IMO-NtimoF1'otak.

Music At Any Time With ThisReceiver - Designed, Built and

Tested by the "W.M." Staff

BY now, almost every valve -setowner who also possesses a

gramophone knows the advantagesof reproducing electrically -producedrecords through the medium of anamplifier and loud -speaker, but forthe benefit of those who have so far.overlooked the possibilities they maybe repeated here.

Chiefly the advantages of repro-ducing gramophone records electri-cally, by means of a high-class radioset, are improved quality (particularlyin respect of the bass), elimination ofneedle scratch, and increased volumewhich is easily controllable.

These facts coupled with thepossibility of having a continuous

QPIT+a

0117+1

OLT+

OLT-HT-

C,B-I

Here is the circuit of the Gramo-Radio Four. Note the position of the electrical pick-up

337

source of music at any time duringthe day (or night, even, if desired)make " gramo-radio" a welcomedevelopment.

None of these advantages can beobtained, however, unless a reallyhigh -quality receiver is used; thismust be capable of giving really goodvolume to work a cone or moving -coil loud -speaker.

Advantage of TransformerIn the ordinary way it is best to

use a resistance -capacity coupledamplifier in order to ensure properreproduction of the bass notes, but.awell -designed amplifier incorporatinga stage of transformer coupling is anadvantage.

This Gramo-Radio Four comprisesfour valves, arranged in the followingway : (1) Anode -bend detector withreaction, (2) resistance -coupled low -frequency amplifier, (3) and (4) push-pull transformer -coupled low -fre-quency amplifiers.

It will be apparent even to the

Wireless Magazine. may. /928

The

novice that this arrangement willgive the greatest possible undistortedoutput forlocal working, either from abroadcasting station or a gramophonepick-up.

For power combined with purityit is pretty generally agreed that onestage of resistance -capacity couplingand a stage of transformer couplingworking together give the bestresults. Adequate output with theminimum of high-tension voltage isensured by using a push-pull stage.

The Gramo-Radio Four is soarranged that the pick-up is con-nected permanently to the set, beingbrought into use when required bymeans of a simple push-pull switchwhich, when in the other position,allows the receiver to be used forordinary broadcast reception. Ofcourse, as no high -frequency ampli-fication is provided, no great range isclaimed for the receiver, but, never-theless, under ordinary conditions itshould be possible to receive a numberof alternative programmes.

Use of Special TunerDetails of the design will best be

appreCiated after a glance at thecircuit diagram reproduced on page337. A built-up tuner is employed(this covers both wavelength bands)and this is provided with two tappingterminals to get the desired degree ofselectivity. This is tuned by a .0005-microfarad variable condenser andthe voltage fluctuations producedacross the circuit are applied to thegrid and filament of an anode -benddetector to give the maximum purityand, incidentally, good selectivity. Aconstant negative bias of r % voltsis applied to the grid.

Reaction is controlled by movingthe reaction coil, which is part of the

M.,

Gramo-Radio Four (Contirned)

built-up tuner.Essentialparts of the re-action circuitare a .0002-

The Gram°.Radio Four

the next valve consists of a .25-megohm resistance and a .005 -micro -farad condenser. The associated grid -

leak is actually a potentiometer witha resistance of approximately onemegohm; this is wired up as a variableresistance and gives an adequatecontrol of the volume.

" Push -pulling "two stages of ampli-fication means dividing the loadequally between two valves in sucha way that one valve amplifies one

CnLoAn Ar

b..Rcwiw .gun

. 0 a

Dont CMOKt

PAIL 21.X7

BASEBOARD 21)(9.7

AAODE

ANN

A

FBLUVRIIIIWPV/P

vi F °""

PKI4111. 4A11% /4.60µ

This layout and wiring diagram can be obtained as a full-size blueprint for half-price,that is 9d. post free, if the coupon on page iii of the cover is used before May 31

microfarad condenser and a goodquality high -frequency choke.

The resistance -capacity coupling to

338

half -cycle and the other valve amplifiesthe other half -cycle. In this case anordinary transformer is used and the

load is split bymeans of two.5-megohm re-sistanceswired in series

The Gram°.Radio Fourwith valvesin position

across the secondary.In the anode circuits of the two

final valves are placed the two halves

Wireless Magazine. may. 1928

Music At Any Timeof a double -wound choke, the centrepoint of which is connected to high-tension positive through a milliam-meter. This enables the grid biasto be so adjusted that the high-tension current is kept as low aspossible and also gives an infalliblecheck on the quality of reproduction.

A jack is provided for the loud-speaker and this is also arranged sothat low-tension supply is cut offwhen the plug is withdrawn.

(Above).-Plan view ofthe Gramo-Radio Four

(Right).-Panel layout,not requiredif a blueprint

is used

Another view ofthe Gramo-Radio Four

a

Yo y4-1 3

14;11,

When it is desired to convert theGramo-Radio Four from radio to agramophone reproducer, the manipu-lation of a push-pull switch puts theelectrical pick-upin the grid -fila-ment circuit of thefirst valve in placeof the aerial tuner.

The Gramo-RadioFour. Note the special tuneron the right of the panel. Thepick-up is kept permanently connectedto the set which can be used for either" gramo" or "radio" by manipulating a

simple push-pull switch

DRILL TO SUITMILUAMMTER

USED

3/j,

21

D.(

Attention may be drawn to theparticular simplicity of the Gramo-Radio Four as far as control is con-cerned. The use of a commercial

339

built:up tuner means that both upperand lower wavelength bands can becovered without the need of changingany coils and, moreover, the cost isquite low.

There is only one tuning condenserto manipulate and the only other"essential" control is the reactionknob. The volume control is neededonly for gramophone reproductionand does not need constant adjust-ment.

Simple Panel ControlsLooking at the front of the panel

the controls are : (r) Push-pull switchfor " radio " (in) or " gramophone "(out); (2) double tuner dial, centreknob for changing wavelength rangeand outer knob for controllingreaction; (3) milliammeter ; (4)volumecontrol knob (3 and 4 are one abovethe other in the centre of the panel) ;(5), variable tuning condenser ; and(6) jack for loud -speaker plug whichalso acts as on -off filament switch.

Little difficulty should be experi-enced in collecting the componentstogether if full use is made of the listreproduced on page 34o. The namesmentioned first in the brackets arethose of the manufacturers whosecomponents were used in the originalWIRELESS MAGAZINE receiver; theothers are recommended alternatives.

Use of Full-size BlueprintActual construction of the set will

be greatly facilitated by the use of afull-size blueprint; this can be ob-tained for half-price, that is 9d. postfree, up to the end of May, if the couponon page iii of the cover is used. Askfor blueprint No.W.M.7o and addressyour enquiry to Blueprint Dept.,

Wireless Magazine. may. 1928

The Gramo-Radio Four (Continued)

COMPONENTS REQUIRED1-Ebonite panel, 21 in. by 7 in.

(Becol, Redfern's or Ray-mond).

i-Long- and short-wave tuner,with reaction winding (Wear-ite or R.I. and Varley).

-.0005-microfarad variable con-denser (Igranic, Cyldon orG.E.C.).

-Milliammeter, reading o -5o(Sifam).

1-High-resistance potentiometer,approximately i megohm(Igranic).

-Panel -mounting single -polechange -over switch (Deck-orem, Lissen or Lotus).

I -Plug and jack (Igranic P63 orP65).

4-Anti-microphonic valve -holders (Lotus, W. and B. orIgranic).

I-.0002-microfarad fixed conden-ser, upright type (Graham-Farish, Dubilier or Lissen).

r-.005-microfarad fixed conden-ser (Graham-Farish, Dubi-lier or Lissen).

1-.25-megohm grid leak (Graham-Farish, Dubilier or Lissen).

I-High-frequency choke (Cos-mos, Igranic or Wearite).

1-Low-frequency transformer,ratio 6 to I (Marconi Idealor Igranic 7% to x).

2-.5-megohm grid leaks withholders (Mullard, Dubilier orLissen).

1-Double-wound low -frequencychoke (Igranic, R.I. andVarley or Ferranti).

i-1%-volt dry cell (Ever -readytype UWI).

2-Terminal strips, 7 in. by 2 in.and 4 in. by 2 in. (Becol,Redfern's or Raymond).

ix-Terminals, marked : Aerial,Earth, Pick-up, Pick-up,

L.T.-, G.B. - x,G.B. -2, H.T.± H.T.+2,H.T.- (Belling -Lee).

8 -2 -ft. lengths of insulated wire(Glazite).

-Pair panel brackets (Cameo,Magnum or Igranic).

1-Cabinet with baseboard 9 in.deep (Caxton).

I-Length of flex with spade tag.IMIII and

WIRELESS MAGAZINE, 58/61, FetterLane, E.C.4.

Mounting Panel ComponentsFirst, fix the panel components in

position (the positions of the variousparts are clear from the paragraph oncontrols on p. 339) and then fix thepanel itself to the baseboard. Screwthe two terminal strips to the backedge of the baseboard and mount the

remainder of the components inposition on the latter.

Looking from the front of the panelthe baseboard components are, fromleft to right : Detector valve -holder,high -frequency choke, fixed reactioncondenser, coupling condenser andanode resistance, first low -frequencyvalve -holder, low -frequency trans-former, " push -pulling " resistances,two valve -holders for final amplifyingstages, and the double -wound choke.The single dry cell for supplying bias

should be connected together, and soon through the alphabet.

When the wiring is completed arough test of the receiver can becarried out. No question of choosing,suitable coils arises owing to the useof a complete tuner, but two aerialterminals are provided and both ofthese should be tried.

Suitable valves are indicated in thetable reproduced on this page. Thedetector -valve should have an imped-ance in the neighbourhood of 8o,000I 1 IMMO.

VALVES TO USE IN THE GRANO- RADIO FOUR

MakeDetector. 1st L.F. Amplifier.

Lna ana .1ra J....I-.Amplifiers.

2 -volt. Et -volt. 2 -volt. 6 -volt. 2 -volt. 6 -volt.

B.T.H. .. B210H - B210L - B215P B4

Cossor .. 210R.C. 610R.C. 210L.F. 610L.F. 220P 610P

Cosmos .. SP18B SP5OB SP18RR SP5OR SP18RR SP5OR

Ediswan .. - - PV6 ES5L.F. PV2 PV61 0

Marconi .. DEH2 I 0 DEH610 DEL21 0 DEL610 DEP240 DEP61 0

Mullard .. PM I A PM5B PM2 PM6 PM252 PM256

Osram .. DEH210 DEH610 DEL210 DEL610 DEP240 DEP61 0

Six -Sixty . .

i1.12

SS210R.C.

SS6075 .R.C.

IMMO

SS215P

MMINI

SS610P

SS2I5P

SS610P

to the anode -bend detectorplaced on the baseboard.

As soon as all the componentshave been fixed in position, wiring upcan be started and for this operationthe full-size blueprint mill be foundof great use.

It will be noticed that each ter-minal point on the blueprint and onthe wiring diagram reproduced onp. 338, is markedwith a smallletter of the alpha-bet; these lettersindicate whichpoints should beconnected togeth-er and in whatsequence.

For example, allthose points mar-ked a are first con-nected togetherwith one wire or asfew wires as possi-ble ; then all thosepoints marked b

340

is also ohms, the first low -frequency stagean impedance of about 15,000 ohms,and the two final valves should beof about 5,000 ohms impedance orless.

To test the receiver connect up theterminals in the following way : toH.T.+ I apply about 8o or 90 voltsand to H.T. 2 about 120 volts. To

(Continued on page 357)

FRONT OPENINGTO TAKE PANEL

al- X7 -

Details of cabinet for the Gramo-Radio Four

WITH the tendency of religionto lose its hold on the " man in

the street" in most countries wherethe white man holds sway, it issignificant that radio has not onlybrought religion back into favour,but has also proved to be a hand-maid. Radio arrested the downwardtendency in religious enthusiasm andallegiance.

EncouragementThroughout the English-speaking

countries and beyond, instead of pro-hibiting religious items, radio hasencouraged them where they are notpartisan and denominational; it .hasgiven them a hearing in the drawing -rooms and cottages of those peoplewho were unfriendly.

The effect, however, has not beenthe same in every country. For in-stance, in the U.S.A. religion iscreating a nausea. The reason for itis this : So many stations broadcastthe viewpoints of one particulardenomination or sect. Others arebuilt and sustained by a sect for thepropagation of its own tenets. Theresult is chaos in the ether and morechaos in the homes of the listeners.

Chaos in AmericaThe editor of Popular Radio, one

of the leading wireless periodicals inAmerica, says : " Religion has pro-duced chaos on the ether." And nowonder, for the Baptists, Methodists,Wesleyans, Christadelphians, andother sects too numerous to mentionhave one or more stations of their

Wireless Magazine. may. 1928

own where they broadcast their owndoctrines only.

Much the same is the state ofthings in Canada. The manager ofUniversal Radio of Canada writes :" The International Bible Students'Association have the exclusive useof our four stations in Canada forreligious propaganda."

On the Continent of Europe mat-ters are the other extreme. TheRussian stations never allow anyreligious talks; indeed, wheneverreligion is mentioned it is mentionedin derision as something not worthwhile for the listener.

The stations of France, Germany,

This is the Rev. Canon" Pat " McCormick,who succeeded the Rev. H. R. L. Sheppardas Vicar of St. Martin -in -the -Fields, andwho, by means of radio, probably has alarger congregation than any other clergy-

man in the world

341

Holland, Belgium, and Sweden broad-cast an occasional service. We hearthe beautiful church and cathedralbells oftentimes. Occasionally wehear a service; sometimes a relay ofchurch music from a church. Butthere is no system or order in anyEuropean country.

Sweden Provides a ContrastSweden is the country that gives

most time to the broadcasting ofreligious matters among these na-tions. Less than half the Europeanstations broadcast any religiousmatter at all.

The B.B.C., like the nation itrepresents, has found a via mediabetween the extremes of the Con-tinent and America. Much religiousmatter is broadcast, but there is nochaos. No sectarian matter is al-lowed, and there is satisfactionamong the sects. We have a noonorgan recital from a church at leastonce a week, an evensong also like-wise. On Sunday we have Old Testa-ment stories and a children's service,and then that popular service atabout eight o'clock in the evening.

Cardiff's Silent FellowshipBut perhaps the religious items

that have grasped the imaginationand heart of our nation are theepilogue from London and the SilentFellowship from Cardiff. Throughthese services the B.B.C. has madereligion popular in many homes. Theradio of the world can look up to ushere for an ideal of tact and commonsense. E. E. R.

IsAMoving-coil

ouct-speakerlArtaile?

Cleaning Up Obscure PointsA considerable amount of corres-

pondence has ensued with WIRELESS MAGAZINE readersall over the country, from which it is apparent thatquite a number of amateurs are in a state of indecisionabout moving -coil loud -speakers. They are not quitesure whether they are worth while or not, and it is the

object of this ar-ticle to clear upsome of the ob-scure points.

In such a caseit is best to startat the beginningand explain brief-ly just what is theprinciple of amoving -coil loud-

tiovimc OILED SILK

IRON CORE co OR SMLA. speaker. TheMATEFIAL

principle will beat once apparentto most listenerswhen it is ex-plained that the

cone is simply an enlarged diaphragm, of which the" magnetic " part is a small coil of very fine wire.

From the diagrams reproduced on this page it will beapparent that the small coil is fixed to the apex of thecone. This takes the place of the ordinary loud -speakerwinding in the circuit, being connected directly to theoutput terminals of whatever receiver is used. Aroundthis moving coil is placed a very powerful magnetic

Wireless Magazine, May 1928

Many Readers Must Be Asking Themselves:

MOVINGCOIL

PERMANENTMAGNET 1)1Aftlitkqm

Poi

IELEXIBLE LEAD3-TO OUTPUT OF_MT

Arrangement of moving -coil loud -speakerwith permanent magnets. The moving coil

is being inserted into the " pot "

ARTICULARS of the first mov-I ing-coil loud -speaker to be con-structionally described in thepages of the WIRELESS MAGA-ZINE were given in the Marchissue, and we know from thedemand for blueprints that theinstrument met the needs of avery large number of readersindeed.

FIELDCOIL

In this diagram all the parts areshown. The magnetic field is producedby current from the mains or an accum-ulator being applied to the field coil

Thishow

t4 baffi

arrang

field, produced either by large permanent mag-nets or, more usually, by a large magneticwinding placed in a soft -iron "pot" and excitedwith a current taken either from the electric -

light mains or an accumulatorFluctuating currents pass'ngthrough the small coil connectedto the receiver cause this to movein the magnetic field and conse-quently the cone produces sound

waves which are audible as ordinary signals.

Two Special Points to NoteTwo points should be specially noted : The

moving coil must carry a large number of turnsin orc;yr to produce the required magneticeffect to actuate the cone diaphragm, and themagnetic field in which it moves must also bevery powerful. For this reason it is preferableto use a "pot" with a field winding, which canbe excited with current from the mains or anaccumulator rather than permanent magnets.The latter type of loud -speaker, however, is

very often the only one which the amateur can use, forthe consumption of low tension for a field winding(something in the neighbourhood of z ampere at 6 volts)is more than many listeners have at their disposal.

Arrangement of the Moving CoilThe moving coil itself can consist of a large winding

of fine wire having a high resistance, which can beplaced directly in the choke output circuit of thereceiver, or, alternatively, it may consist of a fewernumber of turns of thicker gauge wire coupled to theoutput circuit of the valve through a step-down trans-former. It is essential that only a minute air gap shouldbe left between the moving coil and the surroundingmagnet. In fact, the smaller this gap the more efficient

FRETTED)°PENNTO SUITSIZE OFDI API1RA011

342

showsa

e" toed

Normal push-pullcircuit, whichshould be precededby two stages of -resistance - coupled LTamplification

HT+

TO I-1101RESIST/VICEMOVING IOU.

Each valve shouldhave a very lowimpedance, of theorder of 2,000

ohms

will be the loud -speaker, although care must be takenthat the parts do not actually rub, of course.

Why A Baffle Is Essential

In order that the quality should be good, it is neces-sary to so arrange the cone that air waves produced atthe front of it cannot immediately turn back. over theedge and collide with those air waves actually producedat the back of the diaphragm; to prevent this what iscalled a " baffle " is employed, and in practice the coneis inserted in a hole in aboard, which maymeasure about a yardsquare. The edge of thecone is fastened to thehoard by means of oiledsilk, thin chamois leather,thin rubber, or similarmaterial, so that there isno air gap, and air waves pro-duced at the back and front ofthe cone are kept well separated.

The results obtained with amoving -coil loud -speaker dependvery largely on the type ofreceiver with which it is used,and it is almost essential that thefinal output stage should becapable of passing a current inthe neighbourhood of zo milliam-peres. Either a really low-iMpedance power valve of the order of 1,50o ohms mustbe used, or two super -power valves with impedances of3,000 ohms or so must be wired in parallel.

Moreover, it is necessary to pre-vent the heavy high-tension currentwhich normally flows in these anodecircuits from passing through the

FROM PLATEOF PRECEDINGVALVE

LI

PRIMARYHT+

Simpleparallel -valve

25-1 circuit for useSEC. OUTPUT with a low-

TRAIMFORMEK resistancemoving -coil

loud -speaker

TO LOW RESISTANCEMOVING COIL

moving coil of the loud -speaker, and for this reasonan output choke must be incorporated in the receiver. Inthese pages four suitable output circuits, each of whichmakes use of two parallel or " push -pulled " valves, areshown. One of these circuits is suitable only for a low -resistance moving -coil loud -speaker, while the otherthree can be used for either high- or low -resistance move-ments.

Adapting A High -resistance Output CircuitTo adapt a high -resistance output circuit to a low -

resistance output circuit it is only necessary to connecta step-down output transformer with a ratio of approxi-mately 25 to r in the position indicated for the high -resistance coil.

In order to obtain absolute purity of reproduction, itis desirable that the preceding low -frequency stages ofthe receiver should be resistance -capacity coupled, and

Wireless Magazine. May 19281

*5 MOMEACH

GRIDBIAS

NT+

OUTPUT CHOKE

:.111FP

T -

TO HIGH RESISTANCEMOVING COIL

Another and simpler output circuit, whichshould be preceded- by two stages of

ordinary amplification

HT+

TO RICHI RESISTANCE

MOVING COIL

CENTRE -TAPPEDOUTPUT CHOKE

A useful system of " push -pulling " two valves withoutthe need for special transformer

at least two such stagesshould be incorporated if ade-quate volume is to be ob-tained. Probably the idealreceiver for use with a moving -coil loud -speaker is one con-taining two H.F. stages (orone stage employing ascreened -grid valve), ananode -bend detector, tworesistance - coupled low - fre-

quency stages, and a final parallel -valve output stage.From these remarks it will be apparent that it is not

cheap to build or maintain a moving -coil loud -speakeroutfit, but to those who are prepared to pay the cost, itwill undoubtedly give a quality of reproduction that isunequalled by any other loud -speaker available to thea mateur.

Maintenance Expense of Suitable SetQuite frankly it can be said that it is not worth

while using a moving -coil loud -speaker with anordinary two- or three-valver. For really good resultsthe operator must be prepared to supply a heavy anodecu rent for the final stages of the receiver, and this iscertainly expensive unless the necessary current can beobtained from the mains or a high-tension accumulator.If one's pocket can stand the cost a moving -coil loud-speaker is worth while. BM/PRESS

343

AlftGAP

PERMANENTMACHU'S

IRON z-`CORK:"

IRONBLOCK

IRONRLOCK

Details of

permanent -magnet " pot "

Wireless Magazine. May: 19281

Read This Story Before Starting on Your Spring Overhaul !

THE)*ASTTH T FAILED

WITH the first tender buds ofspring, Charles bursts, not into

poetry, but into a frenzied overhaulof all his receiving apparatus. Hegoes over everything, from theinsulators at the far end of his aerialto his new patent phone cosy to keepthe earcaps warm and comfortableduring the cold weather.

Usually he invites me over to hishouse on these occasions, nominallyto look on, actually to do most of thework. This year, as soon as I hadbeen shown up to his wireless den, Iknew that there was something newin the air. Those romanticallyinclined might have called it a touchof spring. For my part, I was inclinedto attribute it to the gases from anovercharged accumulator in thecorner.

The room was full of the compli-cated tangle of gadgets and wires sodear to the heart of the real, hundredper cent. Post Office licensed experi-menter-(sign along the dotted line,please, enclosing ten bob, yourphotograph, birth certificate andthe testimonial of a solicitor, minister,or Justice of the Peace, etc. etc.).

The master ofthe ceremonieswas temporarilyabsent, and hissmall daughter'skitten was busilyengaged in explor-ing the interior ofhis latest " super "set. As it hap-

- pened, Charles hadforgotten todetach the batteryleads from theset, and presentlyan ear-splittingscreech informedme that thewandering felinehad made theacquaintance of

ninety volts high t nsion. I releasedthe startled animal and lifted up myvoice in a stentorian bellow forCharles' immediate return.

A minute or two later he came upthe stairs two at a time and fell overthe cat on the landing. I gatheredfrom his language that the cat hadretaliated, and I hastened to soothehim down by complimenting himupon the business -like appearanceof his den. Somewhat pacified heled the way into the garden wherethe storm centre of the annual over-haul was now raging.

The potato patch looked like" No Man's Land " after a particularlyheavy bombardment. A deep pithalf full of muddy water gaped at myfeet; by the side of this lay a dozenearth tubes, shining bright and neatlywired together with copper tape.It seemed that Charles was installinga new earth system on a reallyambitious scale.

"Don't go down the mine, Daddy,"I murmured gently, as Charlesslithered in the quagmire at thebottom of the pit. I handed himdown the munitions of war, including

344

a large bag of coke which he stackedprofessionally around the coppertubes.

Leaving the pit for the gardenerto fill in the next morning, heclambered up to the surface with somediffithilty-for Charles has a bigfuture in front of him, or, as they sayin schools and places where theyteach, a most generous equator.Perspiring freely he stood beside mefor a moment gloating over hishandiwork. Then, still yearning fora still more perfect earth, he led meacross what was left of the cabbagesto his new aerial mast.

The pole had only just arrived, andwith it one of those patent gadgetsfor raising and lowering it so thatthe proud owner may be able to havethe thing down to tinker with thepulley whenever he feels inclined. Inow began to see the reason for myinvitation; I was to help him tohoist the mast into position, and asI noticed the length and girth thereof,I experienced a good deal of thatsinking feeling. But it seemed thatCharles was not yet ready for thepiece de resistance, as it were.

He threw off his coat and beganto dig another hole. He had, he toldme, designed an aerial -earth systemwhich would have Daventry licked toa frazzle : an earth plate was to beburied directly beneath the end ofthe aerial.

After a while he informed me thatthe time for the next shift hadarrived, and handed the spade to me.For ten minutes I dug furiously andwell, but after I had gone down to agoodly depth I became aware of astrange, unsavoury odour. I lookedround, expecting to see a heap of rottencabbages in the offing, but I couldfind nothing more suspicious than aderelict wheelbarrow. I returned tomy hole, and put in another tenminutes at the confounded business.The smell got worse. I blew my nose

and tried to think of lavender andwild thyme.

But my most persevering efforts atauto -suggestion collapsed miserablybefore the appalling reek that broodedover the neighbourhood. Then Inoticed something peculiar at thebottom of the hole. Holding my nosetightly, I shovelled it up and flungit as far away as I could; as a matterof fact it went into the next garden.

"Charles!" I said sternly andreproachfully to the culprit as hewrestled with the aerial winch; "it isnothing to me that you should run aprivate cemetery for deceased petson your leasehold domain. But, asman to man, I think you might atleast have warned me before."

Charles mumbled that some peoplewere extraordinarily fussy about aslight whiff or two, and continued tounravel a coil of steel cable. Feelingthat my time had come I preparedfor the worst, and breathed a silentprayer that the end might comemercifully and swiftly.

Wireless Magazine. May 1928

Together we toiled and sweated tohoist the mast into position. Weraised it inch by inch until at last its toed almost upright, toweringproudly above the lesser and meaneraerial poles of the neighbours. Charlesstood back to get a better view of it.And just then the fastening cameundone.

The doctorsaid that itwas Charles'shat which saved his life. As it was hehad got off with a mild case of con-cussion. Charles's neighbour saidthat these little things were sent totry us, and that he didn't mindwaiting for a new greenhouse untilthe convalescent was up and aboutagain. Charles himself said nothingat all for a week, chiefly because ofthe bandage which bound up hisjaw.

But I understand that he thinksseriously of giving up wireless forpoultry farming.

G. J. M.

IIIAAAAAAAAAAAAAAAAAAAAAAAM

The Editor of the" Wire-less

WHAT STATION WASTHAT?

Magazine" has madearrangements to to assist 10 -

readers who are in diffi-culty over the identi- °.fication of broadcasting itstations they receive. G -

Each query should giveas many particulars as 0possible (such as time, PIdate, wavelength,

1 language, and distinctive 0'Pcall or signal) and should P

A be accompanied by the PA P1 coupon on page iii of the 0.

1. -cover and a fee of one IP.

shilling (postal order or IP.Pstamps).

Address each query to 1*

1 "Station Identification,""Wireless Magazine," 58-61 Fetter Lane, London,

A E.C.4. P111VV7V1VVVVVVVVVVVVYVTVVIIII

Can You Get Sharp Tuning ?DESPITE the increasing popu-

larity of Reinartz, Hartley, andsimilar circuits, it is still mostexceptionally difficult for simple two -and three-valvers (without H.F.stages) to give good selectivity.

Accentuated TroubleIn some cases this trouble is

accentuated by the use of too largean aerial, for with a great length ofwire the resulting capacity, dampingand great "impact" voltage from allstations within range preventsanything like sharp tuning beingobtained. Signal strength is seldomseriously reduced if the aerial lengthor height is cut down.

With powerful receivers smallaerials are a sine qua non if sharptuning is required.

Centre -tapped coils, as used insome Hartley modifications, and theprovision of a small aperiodic aerialcoupler, as in Reinartz circuits, domuch to prevent and minimise thedamping effect of large aerials. Thetrouble cannot entirely be cured by"stunt" coils, however. Two- andthree-valvers must generally be assimple and straight -forward as pos-sible, and anything in the nature ofcomplicated tuning coils or controlsmust be barred.

Wavetraps, although useful, arenot the limit of perfection. They area cure for non -selectivity, and not aprevention. Moreover, even thesimplest wavetrap means an addedcoil and condenser knob with whichto " wangle " when tuning.

Ideal selectivity can be obtainedby adding one or more H.F. valves,but not everyone is willing to go tothis expense.

Getting to the SourceWhy not cure the trouble at its

source? The real cause of non -selectivity is that there is a leak forhigh -frequency currents across theaerial and earth input. This leakreduces the efficiency of the tuningarrangements and prevents sharptuning.

The first move is to find out wherethis leak is occuring in your set.Panel insulation leakages or the useof condensers or coils which are notof the low -loss type may be theprimary cause; but even if all thecomponents can be passed as satis-factory there is the possibility thatthe valve itself is causing the leakIf grid -condenser -and -leak rectifica-tion is used, then the matter is acertainty.

Glance at the characteristic curve

345

of the detector valve. Even whenthe grid voltage is zero there will, inmost cases, be a small amount ofgrid current flowing. When the gridis r or 2 volts positive (as it mustbe if grid -leak rectification works,for the leak itself maintains thispotential difference) there is a con-siderable amount of grid currentflowing. The fact that grid currentflows means that the space betweenthe grid and filament of the detectorvalve is not an insulator, but is aleak of not too high resistance.

This leaky space is connecteddirectly across the tuning coil, andhence the lack of selectivity.

A Simple CureThe Cure? Simple 1 Substitute

anode -bend rectification, using apotentiometer, for the grid -leaksystem. With anode -bend the gridis several volts negative, and littleor no grid current can flow ; so therewill be no loss of selectivity.

Do not think this is a wholesalecondemnation of grid -leak rectifica-tion, which is indispensable on someoccasions ! But when you have triedall the tips you know to obtainselectivity, and have failed, giveanode -bend rectification a chance.

QUEUE.

Wireless Magazine. May. 1928

Every Amateur Who Has Been in the Radio Game for More Than a Year ShouldRead This Article

DON'T WASTEYOUR

OBSOLE PPARATUS(N4ANY wireless enthusiasts have

by now built their springreceivers, incorporating all the latestdesigns of components that they canafford.

When the set is completed, theconstructor is often at a loss as towhat to do with the old -type appara-tus that he has discarded in favour ofnew gear.

Here, then, are a few suggestionsfrom personal experience.

A Home MuseumFirstly, let me mention an idea

that, while not exactly a practical usefor old components, may appeal tomany experimenters. In a large cup-board with a glass door I have neatlyarranged components that are nowold-fashioned. Some are extinct, andmay be quite interesting and valuablein twenty years time.

I have a shelf devoted to valves,mostly with burnt -out filaments.They range from one made by theG.E.C. to specifications supplied bythe National Physical Laboratoryand having a disc anode of silver tomodern power valves. Wherever pos-sible, I have obtained two identicalspecimens, and from one I remove theglass envelope to expose the con-struction and arrangement of theelectrodes.

Other "Exhibits "Among the other " exhibits " are

loose -coupled crystal sets, tappedsolenoid loading coils wound to Bor-deaux's wavelength, semi -circularplate variable condensers, an old one -inch spark transmitter, a home-madefiling coherer with tapper, and adozen small glass jars with differentkinds of crystals with which I haveexperimented.

All the exhibits have near them apiece of card with notes as to thehistorical and practical interest typedon it.

Small objects are numbered, and acard is made out bearing the numbersand details of as many things aspossible.

Visitors to my den have alwaysbeen most interested in the littlemuseum, and it is always a pleasureto me to take out some old veteranand discuss his life with them.

More Practical OutletTo those who prefer a more practi-

cal outlet for old apparatus, I suggestthat there are many young enthusiastswho are yearning to put their itchingfingers on their own control knobs.What care they if the condenser isnot "square -law," or the rheostatnot so velvety as now demanded ?Does it matter to them if the valveholder isn't antimicrophonic as longas they can pull in a few signals?And I've heard some results fromthese youngsters' " junk " sets thatwould be a credit to many a so-calledlow -loss modern receiver.

Many lads cannot afford valvereceivers, or have to wait a long timewhile they save up. They know quitea deal from wireless periodicals aboutthe working of a set. Why not helpsome young friend to pull in his firstsignals? Will you ever forget thetime that you first heard signals fromthe ether? Not likely ! Well, then,pass the pleasure on and add anotherrecruit to the ranks of the radiofans.

If you cannot dispose of your oldcomponents, they are handy for roughexperimenting when you have no wish

346

to break down a set to try out a freshcircuit.

Controlling Feed -backThe old -type semi -circular plate

variable condenser, providing it iselectrically perfect and not liable toshort, can be used to control theamount of feed -back when capacity re-action is used. There is no real needfor square -law condensers in thisposition, as we are controlling feed-back which is dependent upon thecapacity existing between the anodeand grid circuits.

Many aerial -tuning condensers ofa season or two ago were of a capacityof .00r-microfarad, which is rathertoo high for fine tuning, even withverniers, over the present congestedbroadcast wavelength band.

They can, however, be used inconjunction with a .00i-microfaradfixed condenser so that the tuningvalue is from minimum to .0005 micro -farad. The two condensers are joinedin series and placed in parallel withthe inductance to be tuned. Thisarrangement may be used with anytype and capacity of variable con-denser.

Series CondensersFor example, a .0005-microfarad

fixed condenser in series with a .0005-microfarad variable condenser willhave a maximum of .00025 -micro -farad and a very low minimum. A.00025-microfarad fixed condenserand a .0005 -micro farad variable con-denser will have a maximum capacityof .00017-microfarad, which is suit-able for tuning very short-wavereceivers.

With some variable condensers ofsimple construction it is an easymatter to take off the bottom endplate and remove half of the fixedplates, thereby reducing the capacityof the condenser to approximatelya half of its former value.

Removing VanesThe moving plates that do not

mesh with the remaining fixed platescan be left on the spindle as they willhave no effect upon the working orefficiency of the condenser. In fact,it is not advisable to remove themas it may upset the correct re -settingof the spindle when the condenser isreassembled. Washers must be addedto the lower end of the supports of thefixed plates to take up the space leftby the removed vanes.

Two- or three-way coil holdersmay be made to serve a turn behindthe panel by cutting off the handles.Many circuits require coil§ to becoupled, the amount of coupling,once determined, remaining fixed,being suitable for the range of thereceiver.

Panel -mounting RheostatsPanel mounting rheostats may be

fixed to the baseboard by making upa small platform. The two sidescan he of 1/2 in. wood, r in. highand as long as the diameter of therheostat. The top is of three-plyor similar thin wood. See that theterminals, or soldering tags, areaccessible, by bringing them rightup to, or beyond, the edge of thethree-ply platform. The device maybe screwed to the baseboard by meansof angle -brackets.

Ordinary old -type valve holdersare quite all right for H.F. trans-formers of the old barrel type and forH.F. valves. Modern valves are notnearly so microphonic as they used tohe and plain valve holders are satisfactory for experimental purposes.

Bright -emitter valves, or old typedull -emitters that have been replacedby more efficient and economicaltypes, can still be of use in savingtheir modern comrade from prematuredemise when a new set is being testedout for the first time.

A Good PracticeIt is the practice, and a very good

one too, of most constructors, whentesting a set for correctness of wiring,to plug in the valves and connect upthe accumulator to the H.T. ter-minals. The valves, of course, shouldnot light. If they do, something isdangerously wrong, and the test hassaved the valves.

But modern valves take such asmall current, and are so silveredinternally by the " getter," that novisible sign of whether the filamentis alight or not is perceivable.

Wireless Magazine. May. 1928

The filaments of the old valves,however, are easily visible and areperfectly satisfactory for the test.Even old four- and six -volt bright -emitters will serve in a set workingoff a two -volt accumulator as theirfilaments will glow sufficiently toindicate the correctness, or otherwise,of the circuit.

ft can be seen from the foregoingthat even the oldest of componentsmay be put to some use, and if fromthe suggestions mentioned, some oldveteran is brought from out the junkbox and given a place of honour, orput to further work, then this articlewill have achieved its purpose.

E. J. G. L.

Why Not Build YourOwn Loud -speaker?

IVO amateur, however inexperi-. 111 enced, will find the constructionof a simple cone loud -speaker beyondhis capabilities, and any doubt thatthe reader may have on this scorewill be removed by a glance at thephotographs reproduced here.

Many of the components requiredwill be found in the amateur'sstock box. Here is a list of them :

Loud -speaker unit (Goodman orLissen).

Special paper for r2 -in. cone (Gorki -man or Six -Sixty).

Oiled silk (or other suitable material)of s-tme size for mounting cone.

Three-ply wood to form baffle ofsuitable size (Hobbies, Camco orArtcraft).

3 strips of Meccano or 3 brassstrips.

Small nuts, bolts and screws.Full constructional details for

making such a loud -speaker weregiven on page 21 of the Februaryissue of the WIRELESS MAGAZINEand a full-size blueprint of a similarcone loud -speaker to that described

This photograph showshow the cone and loud-speaker unit are fixed in

position

347

here, is ava;:able for is., post free(No. W.M. 55).

First, stick the overlapping edgesof the cone and when dry put it,point upwards, on a square of oiled

A bright light has been placed behind the load -speaker so that the extent of the cone can be seen.

The front is covered with coloured silk

silk, so that at least an inch is leftall round. Cut out the centre partand trim off the square cornersround the outer edge of the cone.

Cutting Hole in BaffleNow cut a hole in the three-ply

wood a little larger than the coneand stick the oiled silk to the wood.Next screw the loud -speaker to thethree metal strips and bend theseuntil the unit is held directly in linewith the apex of the cone. Attachthe reed to the cone by means ofthe extension rod and washersprovided.

The appearance of the loud -speakercan be greatly enhanced by placing apiece of coloured silk in front of thecone and fixing it in position withsome fancy wooden beading.

It should be pointed out thatwhilst it is possible to use ordinarystiff paper for forming the cone itis very much better to use specialcone paper as specified above.

Wireless Magazine. may 1928

Especially suitable for long-range work with headphones on an indoor aerial is thereceiver described in this article. It is also useful for placing in front of an existing low -frequency amplifier, the resulting outfit being an efficient loud -speaker receiver. The

construction is quite straightforward, as is the circuit

4,

he FLAT -DWELLERSL04;-,-i .. '.-1:-":7Lt

1-:-2:`;7ti?111ji nrf!tt.11'.`!.,! " ii

7:11%1--1I

Comprises Neutraised H.F. Stage and

DetectorEVEN if we have not yet quite reached the age of

flat -dwellers, we are well on the way towards it, atany rate in our large towns.

Specially Suitable for Indoor AerialsIndeed, so great is the number of persons who are

unable to work with outdoor aerials, that the WIRELESSMAGAZINE Technical Staff has produced a simple setadapted especially to their needs.

Flat -dwelling, be-sides imposing, inmost cases, a restric-tion on the use of anoutdoor aerial, alsoentails some obliga-tion to neighbours inthe matter of loud-speaker work, andmany listeners haveperforce to make useof headphones.

The set to be des-cribed in these pagesis based on a circuitcomprising a high -fre-quency amplifier anda detector, the formerbeing neutralised onthe split -primary

Here

C>

4

' 0 005

TWODesigned, Builtand Tested by the

" W.M." Stafftheir crystal sets. If the crystal set is " scrapped " andthis two-valver put in place in front of the existingamplifier, a powerful and efficient loud -speaker outfitwill be the result.

For the sake of selectivity a centre -tapped aerial coilis used (see circuit diagram on this page), and this istuned by a .0005-microfarad variable condenser, which,for fineness of control, is provided with a vernier dial.Following this is the high -frequency amplifier, which,

as already mentioned,

-0005

OhT+1

LT+

0 LT-is the circuit of the Flat -dweller's Two, comprising a stage ofneutralised high -frequency amplification and a detector

principle.This combination makes the set especially suitable for

long-range headphone work with a comparatively smallaerial-such, in fact, as can usually be arranged inside abuilding. Normally it will be of little value for loud-speaker reproduction, although it may operate a smallloud -speaker when used close to a broadcasting station.

Another use for this set is in conjunction with a low -frequency amplifier such as many listeners are using with

0OUTPUT former.

is coupled to the de-tector valve by asplit -primary trans-

It will be seen thatthe centre tapping on

HT+ the primary is con-nected to positivehigh-tension, while thetop end is connectedback to the gridthrough the usualsmall neutralising con-denser, to balance outthe valve capacity andprevent feed -back.

The secondary ofthe high - frequencytransformer, which is,

of course, of the six -pin type, is tuned by another.0005-microfarad variable condenser, which is also pro-vided with a vernier control. Rectification is carriedout on the leaky -grid principle, with a .0003-microfaradfixed condenser and a 2-megohm grid leak.

Fine Control for Picking Up Distant StationsFine control of the receiver for picking up distant

transmissions is obtained by providing a rheostat for

348

regulating the temperature of the high -frequency valvefilament, while both valves can be switched on and offby means of a push-pull switch.

A glance at the photographs on these pages willshow the neat appearance of the completedreceiver. Of the two large vernier dials, that on theleft tunes the aerial circuit, while that on the righttunes the high -frequency transformer.

It will be seen that there are two knobs and asmaller dial arranged in line down the middle of thepanel. The first knob is the push-pull switch;when the knob is in, the receiver is off, and when theknob is out the receiver is switched on; the secondknob is that of the behind -panel mounted neutra-lising condenser.

Special Enclosed RheostatThe small dial is the filament rheostat for con-

trolling the high -frequency valve. Actually theresistance winding is arranged inside the dialitself, so there is nothing to be seen behind the panelexcept a short spindle with a lock -nut.

No components that cannot be readily obtained fromthe average wireless dealer are required for the construc-tion of this receiver, as can be seen from a glance at thelist reproduced on page 350. It should be noted thatwhatever grid condenser is used, provision must bemade for series connection of the grid leak and notparallel connection.

As far as possible constructors are recommended to

Wireless Magazine. May. 1928

The completedFlat -dweller'sTwo in use witha B.T.H. loud-speaker for re-ception of the

local station

follow the original specification (the names that appearfirst in the brackets are those of the manufacturers whoseparts were used in the original construction; followingare recommended alternatives which will fit the avail-able spaces).

Although all the essential details are reproduced inthese pages, a large number of those who build thisreceiver will be glad of a full-size blueprint drilling guide,layout and wiring diagram. One of these can beobtained for half-price, that is 6d., post free, up till

May 31, if the coupon on page iii of

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This wiring diagram can be obtained as a full-size blueprint for halfprice, that is 6d., post free, if the coupon on page iii of the cover is

used before May 31.

349

the cover is used.Ask for blueprint No. WM64 and

address your inquiry to BlueprintDept., WIRELESS MAGAZINE, 58-61Fetter Lane, E.C.4.

When all the parts have beenobtained begin the construction bydrilling the panel and mountingthereon the panel components. Theseinclude the two .0005-microfaradvariable condensers, on -off switch,neutralising condenser and filamentrheostat.

Mounting the PanelThe next step is to fix the panel to

the baseboard by means of bracketsand screw the terminal strips on theback edge of the baseboard. Thenall the baseboard components can befirmly screwed down.

These are arranged almost in lineand, looking from the front of thepanel, are : Aerial coil holder, high -frequency valve holder, high -fre-quency transformer holder (six -pinbase), grid condenser and leak, anddetector valve holder.

As soon as all the components havebeen fixed in position, wiring -up canbe started ; this operation will befacilitated both for experiencedamateurs and novices alike by the useof a blueprint, although a wiringdiagram is reproduced on this page.

Wireless Magazine. may 1928

The

COMPONENTS REQUIRED1-Ebonite panel, 14 in. by 7 in.

(Paragon, Red Triangle, orRaymond).

2-.0005-microfarad variable con-densers (Ripault, Igranic, orDubilier).

I-On-oft switch (Lissen, Lotus, orBenjamin).

2-Vernier dials (Ripault, Igranic,or For mo).

r-Panel-mounting neutralisingcondenser (Peto-Scott, orIgranic).

1-Single coil -holder (Lotus, Lissen,or Burne-Jones).

2-Anti-microphonic valve -holders(Bretwood, Lotus, or Benja-min).

1 -6 -pin coil base (Lewcos, Wearite,or Peto-Scott).

I-.0003-microfarad fixed condenser(T.C.C. type S.P. or Dubilierwith series clip).

r-2-megohm grid leak (Lissen,Dubilier, or Mullard).

2-Ebonite terminal strips, 2 in. by2 in. and 71/4 in. by 2 in.(Paragon, Red Triangle, orRaymond).

r-Pair panel brackets (Carrington,Bulgin, or Bume- Jones).

-Cabinet and baseboard, 7 in.deep (Artcraft, Carrington, orPickett).

4 -2 -ft. lengths of Glazite for wiring.I-Length of flex with spade tag.9-Terminals, coloured as follows :

green, grey, red, black, blue,yellow, orange, mauve, white(Clix).

2 -6 -pin split -primary coils, onefor each wavelength band(Lewcos, Wearite, or Peto-Scott).

2-Centre-tapped coils, Nos. 6o (or75) and 15o (Atlas, Lissen, orIgranic).

1 -6 -ohm panel mounting rheostat(Benjamin, Lissen, or Igranic).

Flat -dweller's Two (Continued)

It will be seen thateach terminal point ismarked with a smallletter of the alphabet;these letters indicate

which pointsshould be con-nected together

and in what sequence.Thus all these points marked a

should be first connected togetherwith one wire or as few wires aspossible; then the points marked bshould be con-nected; and soon through thealphabet.

The methodof connectingup the grid -leak should beparticularlynoted especi-ally if a grid -condenser ofdifferent pat-tern than that

the high -frequency transformer. Itis best to use the same component asincorporated in the original set.

Coloured TerminalsColoured terminals have been used

in this receiver; these are of con-siderable convenience once the coloursare memorised, as they are all differ-ent. An arrangement that the WIRE-LESS MAGAZINE Technical Staff foundto be convenient was as follows :

Aerial, green; earth, grey; L.T.+,red; L.T.-, black; H.T.- , blue;H.T. t, yellow; H.T. +2, orange;output+, mauve; output-, white.

Normally, of course, when theFlat -dweller's Two is used on its owna pair of headphones or a loud-speaker will be connected across theterminals marked " output."

Suitable coils for use in thisreceiver are in-dicated in the

14 list of com-ponents. It isdifficult torecommendone particularsize of aerialcoil as so much

o-depends uponthe size of theaerial.

It might be

..E317;

tki.J-6--

14"

/21.4/2 L.,k,ezi." 1,1,ve: fk;

+

3/.

Panel lay out of the Flat -dweller's Two,not required if a blueprint is used

used in the original receiver is used.If an insulated clip is not used forone end of the grid -leak, the low-tension supply will be short-circuitedthrough the secondary winding of

thought thatwith a short indoor aerial a largeraerial coil than usual would be re-quired, but this is not always thecase as the capacity of an indooraerial is in many instances greater

Plan view of the Flat -dweller's Two, which dearly indicates thedisposition of the components

350

Wireless Magazine. may, 1928

For An Indoor Aerialthan that of an outdoor aerial.

Results depend as much as any-thing on the use of suitable valves.The first valve, that is, the high -frequency amplifier, should have animpedance of 20,000 to 30,000 ohms.The second valve (the detector) canbe of approximately the same imped-ance if the set is used on its own andnot in conjunction with a low -frequency amplifier; an impedancemore in the neighbourhood of 20,000ohms than 30,000 ohms will, however,be found best in most cases.

With An External AmplifierWhen the set is to be used in

conjunction with a low -frequencyamplifier, the choice of a detectorvalve will, of course, be influencedby the type of coupling employed.

With a 4 -to -r ratio low -frequencytransformer use a valve with animpedance of about 15,000 to 20,000ohms. In the case of a resistance -capacity coupled amplifier thedetector -valve impedance should beabout one half or one third of theanode resistance employed.

Whether this set is used with anamplifier or not it is recommendedthat it should first be tested out onits own. Insert a suitable tapped coiland high -frequency transformer intheir respective holders,not forgettingto connect the flex attached to theaerial terminal to the aerial coil. Alsoplace the two valves in position.

To H.T.-1- I apply a potential of 6oto 8o volts and toH.T.+2 apply 90 to120 volts, dependingupon the particularvalve used. No pro-vision is made forgrid bias as the de-tector valve workson the leaky -gridprinciple.

To tune -in the receiverpull out the on -off switch, turn therheostat nearly full on, and rotate

the right-hand con-denser dial slowly,at the same times weepingthe left-hand dialover awide arc.

The Flat -dweller'sTwo ready for use

This photograph shows how the gridleak is mounted on the grid condenser

351

TheFlat -

dweller'sTwo

Carry on in this way until a stationis picked up. Adjust both tuningdials until the greatest signal strengthis obtained.

Neutralising the H.F. ValveIn order to neutralise the high -

frequency valve, it is necessary toswitch off the filament, but the valvemust not be moved from the holder.The valve can be convenientlyswitched off by removing a lead fromone of the filament terminals.

When this has been done, manipu-late the knob of the neutralisingcondenser until signals become quietor almost inaudible. Proper neu-tralisation is not being carried out,as a matter of fact, unless signalsdo become quite inaudible. When thisoperation has been completed satis-factorily the valve can be switched onagain.

Used in conjunction with a two -or three -valve amplifier the Flat -dweller's Two will constitute apowerful receiving combination. It isessential, however, that in the amp-lifier itself high-tension negative isconnected to low-tension negative,and not to low-tension positive.

Short-circuited AccumulatorIf the two units are used in com-

bination and high-tension negativein the amplifier is connected to low-tension positive (as is sometimes thecase) the accumulator will be short-circuited when the set is switched on.

Once again, the reader is warnedthat this set used by itself is onlysuitable for headphone work.

VIrelessMagazine. May. 1928

57M-the Well-known Experimenter-Writes on

Inter-emit hortwave xperimeatHERE is an interesting experi-

ment for those who can fix uptwo short aerials and have a smoothlyworking short-wave receiver. Arrangeone aerial so that it is, as nearly aspossible, vertical. This can best bedone by using the main aerial as asupport for the free end. Now fix upanother of about the same length sothat it is horizontal and has as littledown -lead as possible.

From One Aerial to the OtherIf time is available one of the two

wires should be adjusted until somestation that is working constantly canbe heard, without changing the tun-ing, when the set is switched fromone aerial to the other. If this jobis too difficult it can be got over bynoting the change of tuning necessarywhen changing aerials.

Having fixed your two aerials youwill find out many interesting things.Some stations will come in better onthe vertical arrangement and some onthe horizontal arrangement. For areally true test, of course, the twoaerials should be so put up that theirmean electrical height is the same,and also their wavelength ; but thiswill probably be beyond most experi-menters.

Just to have the two aerials, how-ever, will prove of great interest, andthey are well worth playing with fora month or two. The curious thingis that they don't seem to behavewith any constancy. Sometimes,for instance, 2XAD will come inbetter on the horizontal wire andsometimes better on the verticalwire. Generally speaking, however,in my experience, the vertical wireis the better collector.

Short-wave Broadcastshave been doing a great deal of

listening to the short-wave broadcaststations recently-still sticking tomy H.F. stage, which I would not bewithout-and I find that the majorityof the better-known stations canalmost always be heard without anytrouble at all.

The Monday morning transmis-sions from 3L0 (Melbourne) which

we hear on Sunday afternoons, aftertea, have been very consistent sincethe beginning of the year ; but at theend of March they seem to be gettinga little difficult to pick up. TheDutch Indies station, ANH, in Java,I have heard on one or two Sundaysbetween 2 and 3 o'clock in the after-noon ; but this I7 -metre transmission

A DRILLING HINT

COT TEA

TWIST

MOLE ['SLIM. COT

Above is illustrated the quickestmethod of cutting holes in ebonitepanels to accommodate milliammetersand other instruments that take up alarge amount of space. Cutters of thetype shown can be bought cheaply atmost tool shops ; they very soon pay forthemselves by saving time and temper

can hardly be called one of the reallydependable ones. It is well worthseeking for, however, and it is quitelikely that it will increase in strengthas the year grows older.

Most Remarkable StationOne of the most remarkable sta-

tions is 2XAD on 21.96 metres. Thisalways seems to be at good strengthand very seldom suffers from reallysevere fading. It can be heard from7.o p.m. on Mondays and Thursdaysand from 11.3o p.m. on Sundays,Wednesdays, and Fridays.

Never have I heard it, though, atnight so loud and steady as it is inthe afternoon, when there is broaddaylight over the Atlantic: Onmany afternoons in February I wasable to tune it in at weak loud-speaker strength on three valves andcould heal: every word said at fouror five feet.

There are many natural difficulties

352

in the way of really "safe and cer-tain" reception of long-distance tele-phony on short waves. Whether weshall, some time or other, be able toget over these difficulties I do notknow ; but as we have no real know-ledge of the causes of some of thedifficulties a complete solution seemsto be far off.

What Is Fading Due ToEven when we have tied down the

frequency of the transmission with acrystal or tuning -fork control we stillhave to contend with fading in allits varying degrees and kinds. Sofar as we know most fading is dueto the fact that the angle at which thewaves are reflected from or refractedthrough the conducting layer in theupper atmosphere may vary fromtime to time.

This would account for irregularfading quite well; but it does notaccount for those types of fadingwhich come at regular intervals, nordoes it account for "high-speed"fading. This may be due to the factthat very short waves will oftentravel two or three times round theworld. The rapid impingement of onemodulated wave on another causesinterference. Sharply tuned con-tinuous -wave morse does not sufferto the same extent.

Four -electrode ExperimentsI have recently been experimenting

with four -electrode valves-not thenow familiar screened -grid type-forshort-wa've reception, and am findingthem very successful. I had hopedto have completed. my experimentsin time for this month's notes, buthave not been able to do all I wantto do, and so I will have to put offmy complete report until next month.

I must say, however, that I findcertain types remarkably efficient inour familiar Hartley and Reinhartzcircuits where they allow the use of ahigh -amplification detector with ex-cellent results. The chief advantageof the four -electrode valve is, ofcourse, that it can be worked with avery small H.T. voltage, which makesit particularly useful in the buildingof small portable receivers.

Rebellion Amongst AmateursThere is every sign that established

amateur transmitters are beginningto rebel against QSL cards, whichare nothing less than a nuisance toa busy experimenter. The familiarpost card was undoubtedly of greatuse in the early days when we did notquite knowwhat we were doing ; butnow that contacts are so sure andone can get all the necessary infor-mation at once from the man withwhom we are working it does seemunnecessary to follow the contactwith a card.

My Own RuleMy own rule, which seems to me

to meet all the needs of the case, isonly to send cards to beginners, tonon -transmitting amateurs who sendme reports, and to stations over 3,000miles away. In the latter case Ialways ask whether a card is wantedand state whether I want one myself.I do not want a card unless it is froma part of the world I have not pre-viously "worked," when the card isuseful as a record of the fact thatanother country has been added tothe list of those received.

.

Up to date we have had no infor-mation as to the line our Post Officeauthorities intend to take on thequestion of the new amateur wave-lengths allocated by the WashingtonConference. I presume that weshall fall into line with the rest of theworld, and that the change will bemade on January r next year, sinceour representatives at the conferenceagreed to the allocations.

Working in Narrow LimitsIt will not make much difference to

us, as we are already used to workingto fairly narrow wavelength limits ;but we shall certainly be rather morecrowded together and new methodswill have to be developed. Onething is certain-we shall have tocompletely eliminate any modulationof the note on morse and all strivefor pure " D.C.C.W." We shall alsohave to limit the wavelengths onwhich telephony stations may workif we are to continue with'our experi-menting.

YOU CAN GET A FULL-SIZEBLUEPRINT OF ANY SETDESCRIBED IN THIS ISSUEFOR HALF-PRICE BY USINGCOUPON ON PAGE iii OF

THE COVER

Wireless.Magazine. May 1928

Do You Believe in theHeaviside Layer?

RECENT experiments withshort-wave beam transmis-

sions seem to have put an end to anydoubt there may still have been withregard to the existence of theHeaviside layer.

At Nauen, in Germany, signalsfrom a short-wave transmitter of15 metres wavelength have actuallybeen sent round the world andrecorded after their journey at apoint very near to their startingpoint.

The time taken for these signals totravel round the world was a littlemore than would be expected, assum-ing that the waves had travelled overthe surface of the earth. In fact, thetime was such as to suggest that thewaves must have travelled at anaverage height of a hundred milesabove the earth's surface.

Since .the waves started from thesurface, travelled through the upperregions of the atmosphere and re-turned to the surface, something musthave turned them back to earth-that something being, of course, whatscientists have called the Heavisidelayer.Composition of the UpperAtmosphere

The theory of the Heaviside layeris an ingenious one, but scientistshave still to tell us definitely whatthe atmosphere is composed of at theheight of the Heaviside layer. It isgenerally supposed that, at heightsabove a hundred miles, the atmos-phere is composed of hydrogen witha little helium, though some investi-gators claim that the upper atmos-phere is made up entirely of helium.

AERIAL.

Get Ready To Go Outdoors

Now is the time for all good amateurs to prepare for countryside excursions, thepleasures of which can be enhanced beyond all expectations with a good radio set

353

Wireless Magazine. ivray 1928

JAY COOTS, the European Broadcasting Authority. Tells You

What you ought to know about

CONTINENTAL RADIO.1

)O you ever listen to the pro-grammes broadcast by Vienna?

Personally, whenever I find anopportunity for doing so I do notmiss it for the Austrian station putson the air almost nightly some of thebest entertainments to be found onthe Continent. It is unfortunate,however, that Rosenhuegel shouldhave been blessed-or should it becursed ?-with a wavelength so nearto the ship band, as at times in themiddle of a relay from its excellentState Opera House the transmissionat intervals is " Morsed " to death.

New Super -power StationHowever, there is a possibility that

this difficulty may be overcome by theadvent of the new super -powerstation with which the Austriancapital is to be endowed. In manyrespects the new transmitter will bea sister to the German Zeesen ; it is topossess the same power-some 35kilowatts-is built by the sameengineers, and possesses the advant-ages of certain improvements whichhave been incorporated since thenew Koenigswusterhausen officiallytook the air.

Although it is doubtful Whetheranother wavelength will be allocatedto it, it is to be hoped that its powerwill overcome ordinary Morse signals;they may still be present in the formof a disturbing background, but theirinterference should not prevent goodreception of the transmitted pro-grammes in the United Kingdom.

Summer BroadcastsWith the prospect of possessing

the second most powerful station inEurope, Radio-Wein is already pre-paring an interesting series of summerbroadcasts; in fact, from what I cansee, new studios are to be built, theservice extended, and the magnitudeof the entertainments are all to be inkeeping with the size of the new toy.

Vienna, as an example, contem-plates a monster fete, to take placeduring the period July 16-26, when

there is to be a convention in Austriaof a large number of German choralsocieties. To stage the concerts a hallof gigantic proportions capable ofaccommodating an audience of30,000 spectators is to be built in theneighbourhood of the Vienna Prater-the Coney Island of the Austriancapital. The stage alone will beplanned to take massed choirs of20,000 singers and an orchestra ofsome four hundred musicians !

It is said that over i 20,000 membersof choral societies from Germanyhave already entered for these com-petitions, a further 28,000 fromneighbouring countries, and that over4,000 German-speaking Americanshave notified their intention to crossthe Herring Pond with a view toassisting at the festival. By meansof the new 35-kilowatter Viennahopes to broadcast this monsterfête for the benefit of Europe atlarge.

Special CelebrationsMoreover, in Austria, 1928 is

Schubert year, the celebrations ofwhich reach their climax in Novembernext; special entertainments arebeing arranged for perfdrmance duringthat month, and will be relayed tothe giant transmitter.

Although to most radio fans inthis country the Buda-Pesth pro-grammes are out of reach, the linkingup of the Hungarian capital by land -line to Vienna, and the consequentexchange of radio entertainmentsbetween the two countries, in future,will add a further series of distantbroadcasts to our daily fare. ThroughVienna and Buda-Pesth, we shallalso be connected to Prague andWarsaw.

The installation, in most EuropeanStates, of high -power transmittersmust assist considerably in bringingto our ears the best talent of theindividual Continental capitals.

Of the numerous private transmit-ters now operating in France, Radio

354

Toulouse is, 1 think, the one whichshows the most enterprise and initia-tive. Almost from the day on whichit broadcast its first transmission, ithas been beset with difficulties andnumerous are the obstacles whichhave been placed in its way by theFrench PTT officials.

South Badly ServedThe South of France is badly

served by broadcasting stations, andRadio Toulouse is the one trans-mitter to which the fans resident inLyons, Marseilles, or other less im-portant cities may turn daily for afairly comprehensive programme ofwireless entertainments.

Radio Toulouse, in thejace of localofficial competition, has managed tohold its own for some three years, andappears to have been given the whole-hearted support of the neighbouringmunicipalities, and the surroundingcountry -side. Even telephone land -lines have been refused to the studio,and for its regular tri-weekly relaysof performances from the Thedtre dela Capitole-the principal house ofamusement in that city-it has beencompelled to resort to the systemwhich the B.B.C. in the early daysof broadcasting adopted for pickingup entertainments from the Old Vic,in the Waterloo Bridge Road.

Theatre RelaysAt the Thetitre de la Capitole, a

small 2oo-watt transmitter has beeninstalled; microphones have beenplaced near the footlights, and in theauditorium, and on wavelengthsvarying between 130 and 205 metresthe performance is relayed by wirelesslink to the main 3 -kilowatt trans-mitter erected at the Villa Schmidt,some two and a half miles distantfrom the city.

It was found necessary to adoptthree wavelengths, namely, 13o,165, and 205 metres, and to use themat random on different evenings forthe sole reason that in the early daysof the experiment, interference was

caused by amateurs desirous ofpicking up the transmission from thetheatre aerial direct.

Purity of TransmissionI have listened to these broadcasts

-they are given on Tuesdays,Thursdays, and Sundays-on manyoccasions, and lave wondered at thepurity of their quality. Now andagain they are subject to some slightfading, but at no time has defectgreatlyinterfered with good reception.

Lille, too, or Radio PTT Nord, asit *called locally, shows more enter-priie than any of the other officialtransmitters. The studio possessesan energetic director, who in his turnpossesses vim, push, go and the othernecessary attributes of a successfulshowman-a big asset to a youngbroadcasting station.

Within a year he appears to havedistributed microphones all over thesurrounding landscape, and has linkedup his transmitter to some twentydifferent localities. Apart from theseexcursions abroad, in order to givehis local audience samples of the pro-grammes broadcastby foreign studiosat regular intervals he taps the ether,and serves up hot to his subscribers,at very short notice, choice morselsof the entertainments provided byBritish, Belgian, German, and Spanishstudios.

A Radio Statue ?According to local reports the

inhabitants of Lille contemplate theerection of a statue to their radioorganiser; the rumour, however,lacks confirmation, but the factremains that most of the other officialprovincial studios are content totake the bulk of their entertainmentsfrom the mother station (EcoleSuperieure) at Paris.

.How many of the Polish trans-

missions can you pick up nightlyPersonally, both Warsaw and Catto-witz are always at my beck and call;I can listen to their transmissions ona loud -speaker at any time of theevening. The programmes fromCracow, Posen, and Wilno, on theother hand, are only within my reachwhen the B.B.C. stations are resting.

Increased PowerThat we shall hear most of these

transmitters in the near future can-not be doubted, for in most instances

Wireless Magazine. May, 1928

their power is to be increased. Wilno,for instance, for the present has itsbroadcasting plant on loan pendingthe erection of a 5-kilowatter; War-saw is to spread itself in the etherat an early date, and work on theLemberg (Lvov) station is rapidlynearing completion. But, even withthis programme, Polskie Radio isnot content, for the authorities nowcontemplate the opening of a "radiobranch" at Graudenz, formerly WestPrussia, a town on the right bank ofthe Vistula, situated some sixtymiles south of Danzig.

Background of Polish News-The advent of Cattowitz consider-

ably perturbed the inhabitants ofBreslau and Gleiwitz, who heardtheir local programmes with a back-ground of Polish political news;the news that a 5 -kilowatt trans-mitter is to be opened within "onevalve " range of Danzig will not tendto cheer up the licensed listeners ofthat free city.

Although but little is heard of the

also bridges the gap, and during thewinter evenings, it was possible. topick up its relays of performancesfrom the local opera house. Thequestion of installing in some favour-able district in Russia a giant 300 -kilowatt station has again croppedup; during 1927, rumours regardingthis proposal were persistent althoughcontradicted in more than onequarter.

A Practical SchemeI understand that Russian engineers

consider the scheme a practical one,and that the authorities have decidedto back it. Plans have also been putforward for the extension of radioin the land of the Soviets dUring1928-1929; on January r of thisyear, some sixty-five stations werealready in operation in that country;in /920 there were only three. Someprogress, indeed.

But the country is a huge one;licences are cheap, and in most dis-tricts wireless entertainments are theonly source of recreation during thelong winter nights. The Russian

A QUINTET OF POPULAR BROADCASTERS

These are the members of Geoffrey Gelder's Kettner's Five

development of the Russian broad-casting system, it appears that theSoviet authorities are by no meansresting on their laurels. Many arethe radio fans in this country whoare able to pick up the MoscowKomintem transmissions from thesuper -power station in that city, andon the East coast of England,Leningrad is regularly received.

But little was said at the time of theopening of the new Kharkov-Narkom-potschtel 15 -kilowatt station, but it

355

official factories, dealing with radiocomponents, are to -day producing150,000 crystal and valve receiversin the course of twelve months.

So great has been the demand forcomponents to be used for the homeconstruction of sets that furtherworks have been adapted to copewith requirements. In an officialreport it is stated that the authoritieswill allot to the radio industryduring the present year a sum whichmay exceed half a million sterling.

Wireless Magazine. May I92A

Of Special Interest to Constructors of The Music Charmer

How to PolishYourGbinetsTN dealing with a subject that mayI include every branch of cabinet-making it is well to state what istaken for granted. In this article itis assumed that a plain box -likecabinet, either of white wood or somechoice wood, has already been con-structed to the required dimensions.

It is also assumed that the cabinethas been screwed together, and eachscrew countersunk so that its headlies about 11- in. below the surfaceof the wood. This article explainshow from that foundation a handsom epolished cabinet may be built up.

OrncanentationFirst, as to its ornamentation.

Lengths of moulding may be glueddown the two edges of the cabinetformed by the two sides. Thismoulding should be of a widthcorresponding to the thickness of thewood formed by the sides.

If the cabinet includes a batterycompartment a small drop handlewill be wanted ; this may be purchasedin brass, nickel, or bronze. The holesfor this handle should be drilled, butit should not be screwed downuntil the polishing is completed. Anydoor hinges must be put into placeand the door tried to see if it hangscorrectly, but it must not be per-manently hung until all the polishingis done.

Suitable StainsBefore describing the processes of

staining and polishing we will dealwith stains in themselves so that youmay know what to buy. The follow-ing list will serve most purposes :

STAINS FOR WHITE WOODMAHOGANY

1 oz. Red Sanders to % pintmethylated spirit.

WALNUTHandfulof washing soda in

quart water, add brown umberuntil desired colour obtained.

OAK1/2 oz. permanganate of potash

in pint of rain water. 2 or 3 coats.

FOR CHOICE WOODSMAHOGANY

1 oz. alkanet wood to '/ pintlinseed oil. Wipe over with rag.

WALNUTLight : Wipe with linseed oil.Dark : Treat as if white wood.

OAKTreat as if white wood, but with

fewer applications.TEAK

% oz. Bismarck brown, in 1 pintof hot 'water and vinegar (equalparts).

Always test a stain on a piece ofspare wood before using. To obtainthe right colour several applicationsmay be needed. After straining,glasspaper and then rub a little lin-seed oil into the grain.

Two Polishing MethodsThere are two methods of polishing

the stained wood. The first is veryslow, taking several weeks to com-plete. The wood has to be dailytreated with linseed oil, the oil beingapplied with a rag every day for atleast a month. The cabinet shouldthen be left to harden, when it willbe found that an extremely hard andbeautifully polished surface hasformed.

The second method is the well-known one of french polishing. Butbefore the cabinet can be frenchpolished it is essential that the grainbe filled. A grain filler is formed bymixing fine whiting and turpentineinto a paste. This paste should thenbe coloured to match the stain whichhas already been applied to the wood.The resulting grain filler must berubbed into the wood across the grain.All countersunk screw holes shouldbe stopped with this filler.

For use upon mahogany tint with

356

venetian red, forfor

tint withbrown umber, and for all light woodlike elm tint with yellow ochre. Whendry glasspaper quite flat.

The actual work of polishing maynow be started. The french polishmay be obtained at any oil -shop, andis used with the following rubber:Take a piece of clean rag and lay itflat upon a piece of wood, then takinga fairly small piece of wadding andsqueeze it in the hand until it assumesa convenient pear -like shape. Laythis wadding upon the rag, pull therag up and over the wadding andyou have the rubber.

Charging the RubberIn folding the rag be careful that

no creases form on the working face.For use the rubber must be chargedwith polish, and in doing this care mustbe taken. The covering of rag isopened so that a little polish may bedropped upon the wadding. A littlepressure upon the rubber will nowcause the polish to ooze out slowlyand evenly.

The polishing is done by quicklywiping over the entire surface of theportion of wood to be polished,squeezing steadily the whole time.First work against and then with thegrain. The motion of the rubbershould take the form of circles, andso its path will be something likethis :

Quite Simple ReallyNever let the rubber rest upon the

work, always keep rubbing lightlyuntil the polish is quite dry. A finehard polish will be left. All thissounds very complicated, but if youfirst try your hand on an odd pieceof wood you will soon find it quiteeasy. The beauty of french polish isthat it never marks, and will retainits polish for a great length of time.

R. W. T.

High-tensionaccumulators are excellent forsupplying power to valve anodes

QUITE a number of people seemto think that it is a sign of skill

as .a wireless "expert" if they canoperate their sets on phenomenallylow H.T. values. In the days ofbright emitters the game was alwaysto use as little low-tension as possible,and the man who could receive eventhe local station on the loud -speaker,with the valves a dull red glow, wasconsidered a " super " radio operator.

No Merit in the Popular CrazeNowadays, though, valve gettering

hides the filament glow (if it glows atall, that is, and many do not), and sono credit is attached to cutting downthe L.T. The craze for cutting downthe H.T. is still popular, althoughthere is no merit in it.

After all, nobody really mindswhat a set is like inside, how it isadjusted or made, provided that it

Wireless Magazine. May. 1928

You. Must NotveYourAtiodesl

does what it was designed to do-that is, work.

With modern resistance -coupledamplifiers and low -impedance powervalves neither good strength norquality can be had without ampleanode " j uice."

It should be remembered that themakers' maximum H.T. rating for avalve (12o volts, say) is the maximumvoltage which should be actuallyapplied to the plate. If high resistanceand high -impedance chokes and resis-tances are included in the anodecircuit, the effective H.T. at the valveplate may be less than half that atthe battery terminals.

Not only is ample voltage verynecessary, but consistently goodquality with most sets demands anH.T. supply of large capacity. Hencethe popularity with the cognoscenti ofH.T. accumulators and super -capacitydry cells.

Mains eliminators score in this

respect, in that their voltage andamperage is, to all intents and pur-poses, constant. Make sure, though,that the eliminator you have is largeenough for the set it supplies. It isasking for trouble to use a " juicebox" recommended by the makersfor a two-valver on a multi -valveoutfit.

Heavy Currents Needed

Large power valves demand afairly heavy anode current and if theH.T. eliminator cannot supply thisthen the position will be worse thanif a miniature and run-down drybattery were used.

Summed up, the foregoing factsmean that ample anode voltage andcurrent is a sin qua non for goodreception. There is nothing particu-larly " clever " in working a set onless than its rated amount of H.T.

QUEUE.

IS ITOVER -CHARGED ?

OVER-CHARGING of an accumu-

lator does not have such amarked detrimental effect upon it asdoes constant total discharging. Aftera while, though, excessive chargingwill as assuredly damage the platesof a battery as if it were frequentlyallowed to drop below the minimumof 1.8 volts per cell.

This will not cause those who sendout their batteries to be charged tosuffer from sleepless nights of worry !If you run a home -charger of anytype, though, it is just as well tomake quite sure that accumulatorsare not consistently given too long acharge.

There are three indications givenwhen a battery is fully charged.

First, the voltage per cell will bein the neighbourhood of 2.6 volts, andthis will quickly drop to 2.2 or 2.1volts when a light load is placed uponthe cells.

Second, the specific gravity, when

tested with an hydrometer, should beabout 1.2.

The specific gravity of the acidrises, of course, in some relation tothe voltage and state of charge of acell.

Third, most batteries "gas" freelywhen fully charged. This is not avery positive indication, but is apoint to note as a time-saver. If abattery is known to gas when fullycharged, it is waste of time to test thevoltage or specific gravity unless theacid is " bubbling " freely.

I. W.

A FORECASTMy dear, I was so thrilled last

week, -I saw a Paris dress parade,

The mannequins were very chic.Did I fly over? No, I stayed

In London, where, as advertised,The dress parade was televised !

LESLIE M. OYLER.

357

THE GRAMO-RADIO FOUR

(Continued from page 340)

G.B. -I apply 3 to 4 y2 volts negativebias and to G.B. about 6 or 9volts.

For tuning -in on the low wave-length band, pull out the "change"knob of the tuner, push the loud-speaker plug into the j ack and manipu-late the variable tuning condenseruntil the local station is picked up.Then adjust the reaction and volumecontrols until the required strengthis obtained from the loud -speaker.

These controls and the grid biasmust be so adjusted that the milliam-meter gives a constant reading anddoesno t flicker. If the needle doesflicker at all distortion is taking place.

To change over to a gramophonejust connect an electrical pick-up tothe appropriate terminals and pullout the left-hand switch knob. Itmay, of course, be necessary toreadjust the volume control.

Wireless Magazine. May. 1928

ONE cannot speak too highly ofthe music heard recently from

Mr. Frank Ashworth's fine CastleBand at the Park Lane Hotel, SignorMoschetto's Orchestra at the Savoy,M. Emilio Colombo's Orchestra, sofinely led by Signor Mantovani atthe Hotel Metropole, and M. ReneTaponniere's Orchestra at the CarltonHotel. All these play both popularand classical music.

Kettner's FiveAnother popular combination is the

quintet of players known as Kettner'sFive, led by a brilliant violinist,Mr. Geoffrey Gelder. Only those for-tunate enough to possess a set thatreally takes in Daventry, however,are able to take advantage of theirperformances.

Organ music, though by no meansthe best broadcasting material, is fastbecoming a vital element in the pro-grammes.

LindaSeymour,Singer

Recently we have heard Mr. Patt-man from the Astoria, while ReginaldFoort, who used to be heard fromthe New Gallery, is now beingrelayed from the Palladium on Satur-days for a half-hour recital startingat 6 o'clock.

"Feature Concerts"Amongst what may be termed the

really big "feature concerts" of themonth mention must be made of thetwo final National Symphony Con-certs at Queen's Hall, a series whichit is hoped may be possibly renewed,classical in character though theyhave been. That on Good Friday wasappropriately devoted to Wagner'sreligious music -drama, "Parsifal."The final one, on April 20, whenSir Henry Wood again conducted,included a noteworthy item, thepromised first performance in Eng-land of the " Israel " symphony byErnest Bloch.

358

Opera has been comparatively con-spicuous by reason of its absence, theonly outstanding events being theperformance of Gluck's seldom heardArmida and Mozart's opera, Cosi fanTutle (The School for Lovers).

The vocal element is, as usual, thestrongest side of the programmes, andmany well-known names and earlybroadcasters have been heard fre-quently during the month. Specialmention should be made of MmeRaymonde Amy and also Mr. AlanJohnstone, both original members ofThe Celtic Singers; both are finesoloists, as well as being good in con-certed numbers.

Other Fine SingersMuriel Brunskill, Eda Bennie,

Gertrude Johnson, Walter Widdop,Hubert. Eisdell, and Horace Stevenshave been heard ; all are great singersand have redeemed many a pro-gramme for us.

Harold Kimberley,Vocalist

" john Overton,"Author El Composer

(right)

Olive Sturgess, singer

But apart from these, who aremainly recruits from the operaticstage, there have been many otherexcellent voices broadcast. Miss HelenHenschel, daughter of Sir GeorgeHenschel, has given many solo re-citals. John Booth, Harold Kimber-ley, A. E. Cruickshank, Elsie Black,Linda Seymour, Norman Archer, andOlive Sturgess are all familiar namesto listeners, and their choice of songsfairly popular.

Some Famous SoloistsOne turns to the list of soloists with

relief, for here we have certainlyheard some of the most famousplayers in the world's music. Thepianists have included Solomon, LeifPouisnoff, LeopoldGodwosky, JohanneStockmarr, and CecilBamer, while in vio-linists we have hadsplendid work fromMelsa, WilliamPrimrose, AlbertSammons, and FrankCantell, leader ofthe Birminghamstation orchestra.

RichardWassell,

conductor ofCity of

BirminghamPolice Band

Wireless,Magazine. may 1928

Other solo artistes are Miss BeatriceEveline, 'cellist; Mr. Samuel Clifford,of the Bournemouth Municipal Or-chestra and Broadcasting station;and Beatrice Harrison, the famous'cellist.

The latter joined issue with GeorgeParker (baritone) on April i8, for aspecial programme of John Ireland'smusic, the composer himself being atthe piano.

Another concert of interest wasthat arranged by Mr. Percy Pitt forApril so, whenClaire Croiza, aFrench pianist,came over speci-ally for the pro-gramme devotedto Ravel's work.

Many com-plaints areheard about thepreponderanceof plays in the

ElsieBlack,singer

MaryWilletts,

B.A., reader

programmes, and dullones at that. As anexample of the lattermay be quoted theGerman play, DerRampa, by Max Molnar,though possibly in itsscreen form as The WildMan it may attractmore attention.

Two new radio play-wrights are Holt Mar -well and Cyril Lister,

and their play, The Grossing, will nodoubt be heard, and possibly seen,again.

Appeals have been made by severaltheatrical stars, including SybilThorndyke and Margaret Halstan.The former was heard in Euripedes'play, Medea.

On the lighter side one was glad tonote the re -appearances of JohnHenry, the B.B.C.'s own humorist,

359

HelenHenschel,

singer

and George Robey,who brought some ofhis Bits and Pieces

A. E. from the Prince'sCruickshank, Theatre, and included

baritone in his cast one of ourcleverest comedi-ennes, Marie Blanche.

The talkers havebeen far too numer-ous, but chief in meritmust be mentionedCaptain Eckersley,

whose fifteen minutes should cer-tainly have been thirty. Up in thenorth was heard Miss Mary Willetts,B.A., and Estelle Steele Harper, anauthority on art subjects.

A Shavian PlaySpeeches of Mr. Bernard Shaw

have been broadcast before, but atriumph was scored with the per-formance of his play, .4 Man ofDestiny, broadcast by the. MacDonaPlayers in the London studio.

Mr. Jeffery Farnol, the novelist,best known, perhaps, for his book,Amatear Gentleman, wrote a new playspecially for broadcasting, entitled,.4 Woman's Reascn, which should be .heard again.

EstelleSteele

Harper,talker on

artmatters

Wireless Magazine. May. 1928]

A View of Waterloo Station

THERE are indications that theWireless. Age has not left the

railway companies unmoved and thatcertain interesting developments inthe adoption of broadcasting tomodern transport methods will beseen in the near future.

Southern Railway Shows the WayCuriously enough, the much ma-

ligned Southern Railway has shownthe way. The loud -speakers installedat London Bridge station for announc-ing the departure of trains have beena great success, although there havebeen a few complaints from passen-gers who waited for some hours for atrain to Herne Hill owing to theannouncer, who had been borrowedfrom the B.B.C. for the occasion,committing the unfortunate solecismof sounding the initial aitches.

This idea could easily be adaptedto the task of speeding the departingfriend, the announcer interpolatinghis directions about trains with theconventional remarks and soundsnormally uttered by the seer -off.

The person being seen off might,perhaps, consider that the remarksof the loud -speaker occasionallylacked continuity of bearing, butnobody could claim that the normalconversation in such circumstances isa model of connected thought.Something on these lines would doquite well :

"Number 4 Platform, stopping trainto Aywudseath."

" Well, dear, let's know how youget on. You'll be sure to drop a line

as soon as you get there, dear, won'tyou ? "

Passengers to Brighton and Worth-ing. Your next train is the 5.15 fromNumber 2o."

" Well, good-bye, dear, good-bye . . .

Oh 1 I don't think you're going afterall. Give my love to them all, won'tyou?"

"Plenty of room in the front of theDover train I"

"Are you sure you've got yourticket safely? I do hope you won'thave any trouble with the luggage,but I think you'll be all right. Heseemed such a nice young man,didn't he, dear?"

"Number 7, all stations to CrystalPalace."

"Well, good-bye, dear, don't forgetto let me know how you get on . . .

I thought you were really going thattime-----"It will be possible to effect con-

siderable staff economies by substitu-ting loud -speakers for the clerksemployed in inquiry offices during theholiday season. The personal touchwill be sacrificed, but, on the otherhand, even if an inquirer does notobtain the time of the particular trainin which he is interested, he willsecure a mine of information aboutthe whole system which may proveinvaluable on some future occasion.

Unruffled RecitalAnd, however large the crowd,

however absurd the points on whichthey seek enlightenment, the announ-cer, detached and remote in the calmand peace of the studio, will be ableto proceed with his recital unruffled.The following gives some idea of theform the announcement will take,

360

Courtesy of the Southern Railway Co., Ltd.

and shows the wide range covered :"The 10.15 excursion to Margate

is being run in three sections. Dogs,Birds, Reptiles, or other animalsmay not be taken into the carriagewithout permission of the guard.Owing to coastal fog at Hastings, the9.25 from Blackheath, due in at 20.5,will be zo minutes late. For NetherWollop, proceed via Maidstone, Crow -borough, Hawyards Heath, and WallopMagna. The capital 'A' against the22.30 to Roberts Bridge in the time-table means that it stops to pick uppassengers at Little Woneyed on thefirst and third Tuesdays in Februaryand June. Children under 3 years ofage are carried free; in case of doubtthe Company is entitled to demand theproduction of a birth -certificate. Ilest defendu de se Isencher au dehorsde la Aielre. The 22.25 for Herne Baywill, as far as we know at present,start from Platform 12 at 22.40. Thereis no by-law against eating orangesin the compartment, but the practiceis not encouraged."

Special Programmes!Already a number of trains are

fitted with receiving sets, and it isonly a matter of time before all long-distance trains have loud -speakersas a matter of course. The ordinaryprogrammes will not, however, bequite suitable to the conditions ofmind which a railway journeyengenders, and to overcome thisdifficulty arrangements are beingmade for special railway programmesto be broadcast on a separate wave-length. A typical railway programmewould be as follows :

1.3o. Dance music from ClaphamJunction by the Animated MilkChums.

N.B.-Cotton-wool can be obtainedfrom the dining car attendant forpassengers with sensitive ear -drums.

2.0. Topical chat by ProfessorHumdrum of the Royal StatisticalSociety on " Facts and Figures aboutFatal Railway Accidents."

2.15. Address by the General Mana-ger of the Southern and NorthernInsurance Company on : "Will youleave your widow well-off? "

N.B.-Special accident insurancepolicies can be obtained from thedining -car attendant at sale prices.

2.45. Musical Monologue by DriverW. Adams. " How I saved the 12.69."

3.0. Scientific talk by ProfessorRocke on "The Geological Charac-teristics of the Buffet Bun."

3.30. Song cycle by Mr. F. Flagge :"A -Shunting We Will Go," "I LetDown Your Window," " Wayfarer'sNight Song."

3.45. Tone Picture from the Strat-ford Engine Shops.

4.0. Closing prices of Season Ticketsand Cheap Day Tickets broadcastfrom the Railway Clearing House.

4.io. Art Talks-Mr. A. Canvas,A.R.A., on "The Aesthetic Appeal ofthe Station Waiting Room."

4.30. Practical Psychology. Talkby Professor Froude : "The MentalReaction of a London Porter to aTwopenny Tip." IRVINE FOSTER.

Wireless forWomen

THE former Artistic Director ofthe B.B.C., Mr. A. Corbett -Smith,

recently confessed that in the courseof his duties at Savoy Hill "wirelessfor women" was something that wasrather taken for granted.

Some listeners may remember thatin the early days of broadcastingspecial " Women's hours " were in-cluded in the programmes of Londonand one or two of the other largerstations. These " hours " did verylittle more than become the subjectfor much fun -pointing by mere males(who also laughed at the Children'shour and the " Uncles " and " Aunts ")and in consequence were soon dis-continued. ,

Little of Feminine InterestAlmost every woman who has the

time to listen to her husband's setduring the day will vouch for the!act that not very much with afeminine interest is "put on the air."The B.B.0 in fact, have given upcatering for the ladies as a hopelessjob.

And why? I was discussing thesubject recently with an influentialFleet Street man. Most of the" dailies " contain a woman's page,or at least, a daily feature of feminine

Wireless Magazine. May. 1928

interest, and I thought there mightbe some example set by the news-papers which the B.B.C. could follow.

My Fleet Street friend merelypointed out what anyone who readshis paper could doubtless observefor himself, namely, that present-day" women's " pages are interesting

A WirelessPhantasy

I WENT downstairs the othernight

Because I thought I heard asound ;

Yes, from my study gleamed alight,

No doubt a burglar wasaround !

I entered quickly, though Itrembled -

And found my wireless setassembled.

Two Valves were singing a duet,An Amplifier joining in.

Some Dull Emitters seemedupset,

But all the Coils enjoyed thedin.

" I think," said an Accumu-lator,

" I'll have some oxygen hi !waiter ! "

At this a young Electrode 'ventTo bring supplies as he was

bid,The while an outsize Filament

Made conversation with aGrid :

An Anode seemed inclined tohector

A shy, though capable Detector.

An Earphone and Transmitterheld

A very spirited debate:" Withdraw ! " an angry Wave-

length yelled,And then began to oscillate,

And through it all a Beam keptbeaming --

Then I awoke, I had been dream-ing !

LESLIE; M. OYLER.

equally to men and women. Thewoman is not quite the peculiarcreature that some men believe herto be!

If newspaper women's pages wereconfined solely to cookery hints, aswere the broadcast women's hours,

361

both male and female readers wouldlong ago have clamoured for thefeature to be discontinued.

The interests of a modern womanare identical to those of her menfolk,and she wants her broadcast informa-tion given in a masculine, directmanner. She does not want to hear"namby-pamby" tit -bits, or, solely,a broadcast version of Mrs. Beeton !

Women's Wide InterestsFashion, sport of all kinds, motor-

ing, politics, business and domesticefficiency all come within a modernhousewife's sphere of understanding.She is quite willing to accept herwireless set as an educator as wellas a music maker.

And when the B.B.C. more exactlycomprehends and supplies her require-ments, she will take more interest invalves, transformers, and the wholegamut of radio technicalities.

QUEUE.

CounterpoiseFallacies

WI-IEN, owing to the position ofa set, it is quite impossible to

obtain an earth which is short anddiredt, and therefore efficient, acounterpoise earth can generally belooked upon as a way out of thedifficulty.

For the benefit of those who donot know what a counterpoise is, itmay be explained that an earth of thisdescription consists of a number ofwires forming a subsidiary "aerial."The wires are as carefully insulatedfrom earth as is the aerial itself, andthe lead from the counterpoise to theset must be as short as the aeriallead-in.

Popular MisconceptionsThere are one or two popular

misconceptions in regard to counter-poise earths. First, it is sometimesthought that the wires should be asclose to the ground as possible.Second, that the counterpoise shouldbe an exact replica of the aerial inregard to wire length and spacing.

Both these conditions are in-advisable. There is no need to makethe counterpoise a duplicate of theaerial. All that is necessary is thatit should be an effective screenbetween the earth and the aerial.The distance from the counterpoisewires to the ground is relativelyunimportant. B. I. M.

I

Wireless Magazine. may. 192._9j

Specially Written for the "W.M." by B.B.C. Officials

N the archives of the B.B.C. areI enshrined a vast mass of extractsfrom the national newspapers andperiodicals. So detailed is the systemof filing that it is possible to trace atshort notice any reference, howevertrivial, to anything that has beenwritten about wireless and, in par-ticular, broadcasting. Among thismultitude of press cuttings arethousands-most of them consistingof speculation-devoted to the ques-tion of the transmission of con-troversial mitten It is noexaggeration to state that thissubject has, in fact, occupiedmore space in the Press thanany other single aspect ofbroadcasting. This is easilyproved by mere bulk alone.

Interesting AspectsA study of these cuttings

reveals, however, some inter-esting and amusing aspects ofthe controversy about con-troversy. The outstandingfact is that the Post Officeand the B.B.C. have each inturn been blamed for the factthat any restrictive measuresat all existed, and critics whoat one moment were severe intheir condemnation of the

place in the Press as to the desira-bility of treating controversial topicsvia the microphone, the B.B.C. hadexpresF ed its official view on thesubject, and had suggested that theprogress of broadcasting would beimpeded or nullified so long as free-dom of action was withheld. In pointof fact, nearly three years ago theB.B.C. defined a policy which standsin small need of revision with theeffiuxion of time. It said that if

casting company was fully alive tothe possibility that, with completefreedom in the choice of subjects forthe microphone, a danger to beguarded against was that which theapostles of strife might create. Thiswould be quite a different matterfrom a reasonable effort to assistthe spread of knowledge withreasoned arguments.

Policy StrengthenedThe Corporation strengthenedthe old Company's expressionof broadcasting policy bystating publicly, some timeago, that the admission ofcontroversial matter into theordinary programmes wasbeing tried out by smallgradual steps. Everyone con-

that thecomplete exclusion of debat-able subjects could not con-tinue and that the presenta-tion of sober and broad-minded views on all sides of acontroversy would do good.There were some differencesof opinion, however, as to whatconstituted controversy and,in fact, one distinguishedpublic man declared that ifand when he broadcast, he

RADIO IS GOOD OUT OF DOORS!

See how these enthusiasts are enjoying them-selves. You can do the same if you build the

Sunshine Five. (See page 294.)

B.B.C. eventually decidedthat they were barking up the wrongtree and turned their attention to theether alleged culprit.

Personal GrudgesMuch of the criticism has emanated

from people who at one time or otherthought that they had a personalgrudge against the authorities in thismatter, and gave vent to expressionsof opinion which, while they mighthave been witty, were not wise, andwere no recommendation as regardsthe treatment of a controversial topicwith which they might have beenentrusted to deal if the ban had notexisted.

Long before any discussion took

debates could be arranged regularlyon controversial topics and if leadersof opinion were given the opportunityof placing their case before the public,a great service would be rendered ;but there was this reservation,namely, safeguards for impartialitywould be necessary as well as dis-crimination in the choice of subjects.

The B.B.C. realised that in develop-ing the broadcast service it wasforging an instrument which wouldenable the public to take a keenerinterest in affairs and would enablethem after a time to make up theirminds on vital matters withoutregard for the dictated and partialopinions of others. The old broad -

362

would give no pledge to avoidtouching on controversial topicsunless the Postmaster -General wouldfirst define what was meant by"controversy." Some listeners ex-pressed the opinion that unlessany controversial matter broadcastwas solely for their amusement anddefinitely not for their instructionthey would be opposed to the liftingof the ban.Other Demands

Other listeners said that, aswireless enthusiasts pure and simple,they did not, for example, desirethe broadcasting of speeches in theHouse of Commons. The Postmaster -General voiced the view held by mostserious-minded people when he said

that if politics were once let intobroadcasting, it would be impossibleto keep broadcasting out of politics.

A question which was asked manytimes prior to the Prime Minister'sstatement in the House of Commonson March 5, when he announced thefreedom to be conferred on theB.B.C., was "Who is really respon-sible for the existence of the restric-tive measures? " The situation wasexplained as long ago as November,1926, by the Postmaster -General,who stated that the Governmentmaintained the restriction upon thebroadcast, by speech or lecture,of matter dealing with political,religious, or industrial controversy.

The Government's ObjectThe object which the Government

were anxious to achieve was theprovoking of discussion and criticismof their decision, because their viewwas that the matter had receivedquite imperfect consideration at thehands of the public in general andhad not recei-.-ed a very great deal ofconsideration in the House of Com-mons. By ventilation of the subjectthe Government would be in aposition to take note of the trendof public opinion.

The responsibility for the ban thenappears to have rested with the publicthemselves, through their apathy;and it was only when some indicationwas given that the introduction ofcontroversy would be welcomed bythe public that the Governmentdecided to allow greater latitude tothe B.B.C.

Now, having been let into theinner history of the steps which ledup to Mr. 'Baldwin's announcementof March 5, let us see how theB.B.C. proposes to avail itself of thisnew-found freedom. The latitudeapplies to " religious, industrialand political topics."

In the Religious FieldCertain sections of the religious

community would like to see anoccasional incursion into the relig-ious field, when master minds mightbe pitted against each other on somevery vital topic, such as PrayerBook revision, or on some aspect ofreligious feeling where a real testcould be applied to the country'sinterest in religion. It may, however,be stated at once that there will be

Wireless Magazine. may 1928

TO SPEAK FROM 5WA

The Rev. E. Ebrard Rees, a contributorto the " Wireless Magazine," who is anauthority on John Bunyan, will speak on

Bunyan from Cardiff on May

no change in the established policyand procedure of the Corporation.Subjects that are likely to offendreligious or moral susceptibilities willnot be discussed for broadcasting.The careful consideration which hasbeen given of the many issues invol-ved has decided the B.B.C. to proceedby means of cautious experimentwith the development of the newprogramme material made availableby the removal of restrictions. Thefirst and most important point thatwill he borne in mind is the wide andvaried character of the broadcastingconstituency and also the fact thatbroadcasting is under unified control.Having come to an early and definitedecision on the question of religiouscontroversy, the Corporation willnext consider the manner in whichpolitical and economic controversialmatter should be handled and it will,no doubt, be decided that only ondefinitely prescribed occasions andsubject to adequate safeguards as toimpartiality and equality of oppor-tunity shall controversial matter beincluded in the programmes.

" Controversial occasions " will belabelled as such, and will in themeantime take the form of debatesand discussions. It is difficult todefine precisely the occasions onwhich controversy might be regardedas permissible; but one might specu-

late that the subjects which would beconsidered suitable for the microphoneare the following :-

" Should wages be paid accordingto the needs of the wage-earner, oraccording to the value of hiswork ? "

" The return to the gold standardand its effects onperity. "

" Is a minimumor practicable ? "

"Is the Surtaxable ? "

national pros -

wage desirable

fair or work -

Outside BroadcastsThere are controversial elements

in outside broadcasts, adult educa-tion, talks in general and so forth ;but the existing policy in relation tothese matters, namely, of gradualand experimental extension, will becontinued and developed. Finally, apoint which the B.B.C. must emphas-ise is that freedom to deal withcontroversial subjects does not affectthe responsibility of the Corpora-tion of continuing in the bulk of itswork to adhere to a non-partisanattitude in presentation.

CLAPHAM-AND NOTDWYER

HOW many listeners know thatthe B.B.C. carry out much

laboratory test work in Clapham ?Yet for many months a house in thatlocality has been the scene ofexperiments conducted by Capt.West and his staff.

The laboratory is not, primarily, areceiving station, and the work

.carried on there is chiefly of a" studio " nature. Various acousticproblems have been solved in thisdepartment, and new microphonesand similar equipment have beenput through their paces by the Clap-ham experimenters. B. B.

AN IDEA FOR THEPOST OFFICE

OURown postal authorities might

take a hint from their colleaguesin Ceylon and use as a stamp -cancel-lation mark some slogan that en-courages broadcast listening. A slo-gan now in use in Ceylon is : " Areyou a broadcast listener? ", followedby the cost of a licence.

All You Want to Know 'About Moving -coil Loud -speakers Next Month

363

Wireless Magazine. May, 1928

Even the Non -technical Listener Will Be Interested in the Question :1 1 lllllll ( IF lllll ru,,nirrirrIrt111111111111/1 II llllllll 11 /

IsThere Eternityin the Ether?

111111 k11.111111/i11F llllll 11111/1111 lllll 1/11.11,111/111 lllllll lllll 11111 llllll lllllll 1 llllll I llllll 111111 lllll

ARE out wireless concerts immor-tal? Much interest has been

aroused by statements in the dailyPress to the effect that wirelesswaves never die out. And that if ourgrand -children have ultra -sensitivewireless receivers they will be able tohear all over again the present-daybroadcast concerts, talks and Oxfordaccents.

Ether Waves EverlastingThe question depends upon the

now fairly general assumption thatether waves of the light and wirelessvariety are everlasting. Or, at least,will persist for hundreds, thousands,and even millions of years. As amatter of fact, we have actually seenand caught, as it were, light waveswhich have been travelling throughspace for over a million years. Andwireless waves belong to the same

lllllllllll lllll

ethereal family as light waves, andin many respects are identical. Thustheir immortality is also likely.

It follows then, that not only areour wireless concerts probably ever-lasting, but pictures of all thingsupon which light has shone from thebeginning of time are immortal too.

Somewhere in the ether of spacereal definite pictures of the world aretravelling on and on like the unwind-ing of an endless cinema film. Thereis a picture of the beginning of theearth-a nebula. The hardening ofthe outer crust-the vegetationappearing, with lower forms of life.

Time passes-man appears, and atlength, on the unwinding film comes

SOMERECENTBROAD-CASTERS

(Left).Alan Johnstone,

Scotch tenor(Below).Margaret

Halstan, actress

FFIF111111111111 1 I

F

civilisation. Egypt, Babylon, riseand fall, likewise Greece and Rome,right down the ages to our own. Andwith the pictures of our own civilisa-tion comes something new, accom-panying the light waves from theearth. Man has discovered wireless-and is pouring wireless vibrationsinto the ether for the first time.Probably Nature smiles, like a fondparent at the precocity of its child.

Position of First BroadcastConcert

What is more, it is fairly simple towork out whereabouts in spacethe first broadcast concert is at themoment, the whereabouts of Cleo-patra's first meeting with Anthony,or the King opening Wembley Exhi-bition, or the burial of Mr. Smith'sgrandfather, who lived at Peckham.So blue bloods beware of any bogusancestors, for somewhere out in

11111.11:11

(Left). FrankCantell

(Right).John Booth,

singer

(Below).NormanArcher

364

frontiers of the Milky Waywhich we see in the sky soclearly on some nights.(What will have happenedto our earthly broadcastingwhen our first concertreaches that distant clime ?)

Twenty-five thousandyears ago Cro-Magnons in-habited this country to-gether with tigers andmammoths. If there arebeings on the planets of theMilky Way looking at oursolar system through a superpowerful telescope, they willnot see the world as it isto -day, but as it was twen-ty-five thousand years ago.Possibly they will be sayingto each other about us :

" Well-there isn't muchsign of intelligence onthat world yet . . . wonderwhen it's coming, conditions

A PORTABLE SET SUGGESTION

FRAMEAERIAL CONTROL

PANEL)

BATTERY

LOUDSPENSER

---L.T. BATTERYOR ACCUMULATOR

Here is a suggestion that home constructors can workup individually to suit their own special requirements

pretty favourable. No sound ofwireless music up to the present."

Travelling for a Million YeatsIt has been mentioned that' we

have seen light -waves which havebeen travelling through space for overa million years-constantly main-taining their terrific speed of i86,000miles per second. This is in the great

. at the_,Mmint.Observatory. In this, telescope it ispossible to see a tiny star which is

ray will take to return to its sourcehas been worked out by some of ourgreat mathematicians, and it is notin the time of our grandchildren, butsome untold millions of years hence,in fact.

There are a few other snags, too.The whole solar system is movingrapidly through the Universe. Poss-ibly every day we occupy some en-

tIrely, new position in space-andthis also complicates matters for anyof our grandchildren with eaves -

365

space are the ghostly pictures ofyour ancestors, much more faithfullyreproduced than in the ancestralgallery !

Near Alpha CentauriIf we assume that the first broad-

cast concert took place four yearsago, that concert is at the moment inthe vicinity of our nearest fixedstar, Alpha Centauri. The calcula-tion is simple. Alpha Centauri isfour light-years distance from theearth. A light-year is the distancea given ray of light will travel inone year, and wireless waves travel atthe same speed as light, namely186,000 miles per second. So thatin four years the wireless wavesof our first concert will have travelledfour light-years in distance. Ofcourse, this is presuming that wirelesswaves go outward and onwards inall directions.

To go a little further-twenty-five thousand years will havepassed before that concert willhave reached even the near

Wireless Magazine. May 1928

over a million light-years distantfrom us. A million years ago thatlight image of the star which theastronomer sees to-night-left theactual star and is still very muchalive and kicking. Truly light -wavesare eternal, so why not wirelesswaves ?

When it comes to our grand-children hearing our broadcast con-certs over again, however, we areon less sure ground. For, althoughwireless waves certainly cling to theearth, up to a point, these wavestend to become absorbed and it isonly those waves which gain thefreedom of outer space which canpersist.

Thus the wireless concert which ishere to -day is gone to -morrow,flying on its way through space. Butit may-and here is the point-itmay return to the earth from spacebecause we now know that it willdescribe a great circle with a possi-bility of returning to its source, like abad penny.

The time which a light or wireless

dropping tendencies. Thus an instru-ment to detect these early broadcastconcerts of ours will be of little usefor some millions of years to come.(But, after all, we are merely on thefringe, and how little is a millionyears to the earth and its develop-ment.)

Light Images or PicturesWith regard to light images or

pictures-it is a different matter.Even at the moment pictures of ayounger earth may be floating pastyour back door. The solar systemmay be floating through a pictureof the earth in the throes of the IceAge or some other ethereal image ofanother world-had we but themeans to see it all.

There is also a school of scientificthought which believes, with a certainamount of justification, that everythought we think creates ethervibrations. They base their assump-tion on the mechanistic theory of themind, which says that a thought ismerely the rearrangement of the

molecules of the brain.And we know that if thesemolecules are disturbedthey create an eleetro-magnetic strain in the ethersimilar to the electromag-netic strain we set up with abroadcasting transmitter.

So we are to believe-and it is quite likely-thatin addition to eternal wire-less concerts, and lightpictures of the past, all ourthoughts which we deem soprivate are also immortal-the common property ofthe ether, may be for futureuse. Telepathy is accountedfor in this way.

Preposterous as it maysound, it is neverthelessquite possible that thethoughts of our famousdead (and the others) mayyet be known to posterity.

Startled by a New Invention?Probably in some future time, the

then ultra -civilised world will bestartled by a great new invention-just as we were startled by wireless. . . thus : "Take notice. A newinstrument for revealing the etherealimages and .voices of the past, andlaying bare the thoughts of theAncients of the zoth Century andother remote times. Price com-plete . "

Wireless Magazine. may, 1928

All Tests Are Conducted Personally by Our Technical Editor at the

Furzehill Laboratories

ew ets an

ANODETUNER

4

3 11E11E1'5 FOR 2()), 2:U AND 241; MANS

Front View of Gambrell Mains Receiver

GAMBRELL MAINS RECEIVERGAMBRELL'S have specialised for

some time in the production ofreceivers intended tobe run entirely fromelectric -light mains.This is a propositionwhich, in general, isfairly simple, but isapt to be troublesomein particular. It is no uncommon thing tofind a receiver whichworks perfectly on fiveor six different supplycircuits, but which willrefuse to give satisfac-tion on the seventh.

In the case of a firmwhich has specialisedin receivers for this

. particular purpose, onemay reasonably expect Inside Arranlittle difficulty, and inthe case in question the results obtainedwere excellent. The model was an A.C.model, the current being converted toD.C. at 200 volts. A metal rectifier isused capable of passing oo milliamperesat this voltage and the output from thisrectifier is smoothed with a double -choke and condenser filter.

Inside the ReceiverAll these features can be seen in the

photograph of the eliminator portion ofthe receiver. This portion, incidentally,is normally completely boxed in and-isnot accessible to the ordinary user sinceno difficulty is likely to arise with thisportion of the equipment, owing to theabsence of valves or similar devices.

The receiver proper employs one11.F. stage, a detector and one L.F.._.1

age. The filaments of the valves are

paratus estedrun in series and as Mullard .r -amperevalves are used, this current can besupplied from the 200 -volt systemalready referred to by inserting a suit-able resistance in series. The voltagedrop on this resistance serves to supplythe high tension for the various valves.

A centre -tapped tuned -anode circuitis employed for the high -frequencystage, a centre -tapped coil being usedin the first circuit. Such an arrange-ment gives quite a selective system andthe results were very pleasing. Theneutralising condenser, which is aGambrell Neutrovernia, is utilised forreaction purposes.

Geared slow-motion dials serve tomake the tuning easy and not too criticaland this, coupled with the entire absenceof hum, makes the receiver an attractiveproposition. A similar receiver is avail-able for use on D.C., the mechanismbeing similar with the exception thatthe rectifying apparatus is omitted.

gement of the Gambrell Mains Receiver

BRANDESET NO. 3Ap HIS popular three -valve receiver isran excellent example of the cheapset. It is essentially afactory -built job, theassembly being laidout on mass -produc-tion lines as opposedto a mere collection ofordinary components.

A single tuning con-denser is utilised, thisbeing provided with athumb control havingtwo drums, one givinga quick motion andthe other a fine adjust-ment. This is placedcentrally on the panel,the left-hand sidebeing occupied with a

366

reaction control and a simple rangeswitch, while on the right-hand side wehave the on -off switch which has threepositions. The first of these is the offposition; the second gives an arrange-ment with two valves only, acting as adetector and one L.F.; while the thirdposition brings all three valves intooperation.

Elliptical Cone Loud -speakerAll these controls can be seen from the

photograph accompanying this report,as also is the Ellipticon, which, as thename implies, is an elliptical cone loud-speaker, which gives very pleasingresults.

The interior view of the receiver is ofinterest owing to the method of con-struction adopted. The three valveholders are carried on an insulated stripwhich is floated at each end on rubberbands. This obviates the necessity ofproviding vibratory valve sockets. Thetwo tuning coils can be seen on the left-hand side of the panel, the short-wavecoil being a simple solenoid and thelong -wave coil being a duolateralcoil.

The reaction coil swings in betweenthe two, coupling to either one of theother as required. As will be seen,transformer -coupled L.F. stages arcemployed, the circuit being a straight-forward detector with two L.F. stages.

Good Performance on TestThe performance of the set was good,

ample signal strength being obtainablewith reasonable selectivity. Nc diffi-culty was experienced in tuning in anumber of distant stations while Londonwas transmitting. Three aerial ter-minals are provided so that the requiredorder of selectivity can be adjusted tolocal conditions.

A particular feature is that the woodenfront panel of the receiver is metal linedat the back so that hand -effects arenoticeable by their absence and the

THUMB GONiNU.. LOODENJI4tStilw-MOTION LEO- 450 ,ROINARY TuN1NG R11,0!

RANG SWITCH

*AY $WITCHAWF:2ANII3MALVtU

REACTION LONNA: TO THE LEFT FON SNORT WAVESAND TO RIGHT FOR LONG 04000

Front View of the Brandeset No. 3A

FLOATING VALVE LONG -WAVE REACTIONSTRIP COIL COIL

411011111111111NOMPAINORMIVAD

SNORT -I4AVCSCR

Internal Arrangement of the Brandeset No. 3A

receiver is generally simple and easy tocontrol. A fully illustrated instructionbook obviates any trouble in the handsof the novice and serves to completea well -thought out production.

COSMOS ELIMINATORSTHE design of a mains unit capable

of being used with any set is stilla matter of extreme difficulty owing tothe varying conditions which are en-countered in practice. The difficulty of"motor boating" is perhaps the mostserious factor to be contended with.This is overcome in the Cosmos elimina-tor by the provision of a separate tapfor the last valve.

The loud -speaker return is not takenback to the L.S.-1- terminal on the set,but is connected direct to a specialterminal on the eliminator. The H.T.to the remaining valves in the receiveris taken from a separate tapping which

OUTPUT

0101516

80450

FUSE

Front of the Cosmos H.T. Eliminator

's fed through a separate choke andsmoothing circuit.

Up to 20 volts grid bias is providedin 5 -volt steps, but since this is run off aseparate filter system, this grid bias canonly be used for the last valve. Anordinary grid -bias battery must beused for the earlier stages of the receiver,but such stages do not require more thana 9 -volt battery, so that this is quitean easy matter to provide.

The input to the eliminator is intro-duced at the back where there is a

Wireless Magazine. May 1928

distributor board con-taining a plug and anumber of sockets,numbered from zoo to25o in steps of ten.The plug is inserted inthe socket correspond-ing to the supply volt-age.

On the front of theeliminator, there aretwo further distributorboards one of whichhas 200 and 24o voltsavailable for the highvoltage (last stage)tapping, while theother gives 4o, 8o, 120,or 16o for the normal

H.T. tap to the receiver. A switch anda flash -lamp fuse complete the assemblyon this panel.

At the top are two terminals which arenormally kept short-circuited, but which

This latter unit is a simple step-downtransformer for supplying the voltageson Cosmos A.C. valves. By this means,all voltages can be supplied from themains. Plugging the L.T. eliminatorinto the back of the H.T. unit in thismanner brings all the voltages under thecontrol of the single switch on the frontof the main eliminator.

Exceedingly Well ConstructedThe instruments are exceedingly

well -constructed and are housed inmetal cases completed in a blackcrystalline finish.

A particular feature which we werevery pleased to see was the provis.onof definite air gaps in the smoothingchokes. This is deliberately done toavoid saturation effects and is an indica-tion of the thoroughly up-to-date designof the instruments.

Both units gave excellent results ontest and should prove of considerable

value. Complete and detailedinstructions are supplied witheach instrument in the form ofa small booklet.

/27Npf.ISE0.

SMOIT*HINSCONOENSEP.-

CANSTRAM5P3RME

AtY,TANZr.F. UNM3RMEP.5

C:,:j'ES S!11.9Y rUTT CONUF:lf,Ek

Internal View of the Cosmos H.T. Eliminator

nay be used for choke feed on the laststage. If this connection is desired,the L.S.-1- terminal on the eliminator istaken direct to the anode of the lastvalve and the loud -speaker is insertedin between these two terminals at thetop of the unit, these terminals beingnormally strapped together.

At the back of the instrument is asocket into which the adaptor from theL.T. eliminator, if any, may be plugged.

367

FORMO COLLAPSIBLESCREEN

MHERE are many rasps inI which the use of a com-

pletely screened circuit is desir-able. In such cases the buildingup of the screening box is amatter of some little difficulty,since trimming and preparingsheet metal, although compar-atively simple, is apt to produceclumsy and unsightly resultsunless very great care istaken. A machine -made pro-duct is clearly capable ofproducing neater resultsthan the average hand -madebox.

To meet this need, the Formo Com-pany have produced a collapsible screen-ing box. This is made with the sides,

.7. H. Reyner, , B.Sc.,A.M.I.E.E., Tech-nical Editor, check-ing over test reports

in the Furzehilllaboratories

MIL

Wireless Magazine. May 1928

New Sets and Apparatus Tested (Continued)

top and bottom in the form of flanges.The ends of the sheet are curled roundand by the use of corner pieces a com-plete box can be assembled in a veryshort time. The pieces are fixed to-gether by sliding one into the other,no bolting being necessary, while inaddition holes are cut in the sides atsuitable places for mounting condensers

FUMED 1.0

EFIECTO1C STRIPWRY PRESSED

MOOD BASEFORPOSITIORFOR COMP011EMT5-'

Formo Collapsible Screening Box

or leading wire through into the boxitself.

The whole instrument forms a veryneat job when completed, and can berecommended for use. It is made bythe Formo Company, of CricklewoodI.ane, N.W.2.

LOTUS SWITCHAN on -off switch connected in the

battery circuit is an essential partof any valve receiver. This switch may,with advantage, be of the push-pullvariety, since this type is inexpensiveand simple to operate, and if correctlydesigned is not liable to give trouble afterlong usage.

A neat form of push-pull switch hasbeen submitted for test by makers of thewell-known Lotus components. Thiscomponent comprises a metal plungerwith an insulated knob at one end. Twometal springs mounted at each end of an

Lotus On -offSwitch

OME,--110LEming NUT

insulated support bear on the plunger,which is protected by an insulated sleevein the " off " position.

Owing to the powerful nature of thecontact springs, a good electrical con-tact is always ensured in the " on "p4ition : whilst due to the smoothsurface on the insulated bush and

suitable contour on the metal end, theaction of the switch is smooth, and the" on " and " off " positions are definite.A terminal is mounted on the insulatedsupport connected to each spring. Theswitch may be fixed to the panel bydrilling a single hole.

Lotus components are made byGarnett, Whiteley & Co., Ltd., ofBroadgreen Road, Liverpool.

ATHOL CONNECTORT is often desirable to connect twoI pairs of leads together and at the same

time keep the two connections so formedapart. For example, it may be desiredto lengthen a lead from the electric -light mains, in which case it is oftennecessary to bind the exposed surfaceswith insulated tape or some suchmedium.

Connections of this type may be madewith ease and without risk of short-circuiting if a suitable connector isemployed. The Athol Company, ofManchester, make an attractive con-nector, which consists of two brasssleeves housed in a neat but substantialporcelain holder. The leads to beconnected are inserted in either side of

AtholConnector

the sleeve and locked by small butaccessible screws.

In this manner, excellent connectionscan be made and, since the metal sleevesare sunk below the porcelain surface,there is little risk of accidental short-circuit. Two holes are provided in theporcelain holder for fixing to the base-board if desired.

The address of the manufacturers isthe Athol Electrical Co., of Tyson Street,Cheetham Hill, Manchester.

IGRANIC RHEOSTATTHE use of rheostats is coming into

favour once again, the tendencybeing to employ a master rheostat onthe receiver instead of a switch:: For apurpose such as this an expensive itemis not required, but at the same timeone experiences pleasure in handling asmooth control which is neither mechani-cally or electrically harsh'.

The new Igranic rheostat which' wehave received for test has both thesedesirable characteristics. It - i n c o r-porates the principle adopt6d on theolder form of Igranic resistance in whicha contact rubs on the outer surface of a

drum carrying the resistance element,and not on the edge as has become verycommon. An excellent contact witha smooth action is thus obtained.

The instrument in question is smallin size and can easily be mounted, whileit is provided with an attractive knoband pointer. It should prove of inter-est to readers. The sample submitted

IgranicFilamentRheostat

for test was rated at 55 ohms. and wasactually found to have a maximumresistance of 16 ohms, giving an amplefactor of safety.

The manufacturers are the IgranicElectric Co., Ltd., of 149 Queen VictoriaStreet, E.C.4.

PIRTOID FORMERTHE fact that losses are set up in

ebonite tubes has been recognisedby constructors for a considerable periodand various other dielectrics have beenemployed from time to time.

One of the best-known of these isPirtoid, this being a form of varnishedpaper compound which has excellentinsulation and low dielectric loss. Ithas hitherto been produced in the naturalfinish which is a light yellow, butH. Clarke & Co. have recently produceda black finished model which is similarin its electrical properties to the originalform.

The material is light and formersconstructed of it are rigid and easilyworked. They can be highly recom-mended for use in winding coils of anytype.

Pirtoid is made by H. Clarke & Co.(M/c.), Ltd., of :%;Eastnor Street, OldTrafford, ManchestEr.

Nett/ti 1

Black finish II

Pirtoid Tube

COSMOS A.N.P. COILSONE of the most efficient high -

frequency circuits is the tunedanode provided with a centre- or quarter -

(Continued on page 370)

For Further Particulars Write to the Manufacturers !

368

Wireless Magazine. may, 1928

tvett TUNING

Osesfor greafselectivity.

12 I.Complete withKnob and Dial

and Vernier

How delightful to be always certainof your. station-to be able to tunein whatever station you desirewith no time wasted in undecidedsearching.

In design and workman-ship, the Dubilier K.C.Condenser maintains therecognised standard ofDubilier efficiency and,like all Dubilier pro-ducts, is unsurpassedin performance. Usedin conjunction withthe DubilierToroidsit will give uniformkilocycle tuning.

WHAT YOU GET FOR YOUR MONEYt. VANES of stout brass sheet. 2. SPACERS, between which vanesare firmly clamped, ensuring rigidity and eliminating possible resistancethrough loose connections. Consistent spacing assured by the extreme accuracyto which spacers are turned. 3. TERMINALS-one giving direct connectionwith the frame and rotary vanes and the other with the fixed vanes.4. INSULATORS of high quality moulding material under compression,forming an effective insulation of the stator plates, and eliminating die,ectriclosses. 5. END PLATES of the skeleton type, ensuring rigidity and lightness.6. KNOB AND DIAL of finest finish and engraved in too single degrees.Diameter 4. in. Main knob rotates moving vanes direct. 7. SMALL KNOB.This moves inthmendently of the main knob and works a slow-motion drive.8. SLOW-MCTION BALL DRIVE. Approximate reduction ratio of 2001enabling precise tuning adjustments to be easily secured. 9. BALL RACE,giving a ve,vet-smooth movement whether the direct or slow-motion drive isused, and with entire absence of backlash in either case. One hole fixing-

in. clearance. A large nut is provided for mounting on panel. Maximw.Capacity '000s.

DUBILIER©139

Advt. of the Dubilier Condenser Co. (1925), Ltd., Ducon Works, Victoria Road, North Acton, W.3.

Mention of the " Wireless Magazine " will ensure prompt attention.

369

Wireless,Magazine. may. 1928

New Sets andApparatus Tested (Contd.)

tap. The tapping serves not only tominimise the valve damping, but toenable bridge neutralisation arrange-ments to be adopted. Unfortunately,difficulties arise with this method owingto parasitic oscillations, which are pro-duced by one half of the coil resonatingat its natural frequency, and rather

Cosmos A.N.P. Coilinvolved methods have to be adopted tocombat this trouble.

An ingenious system has been em-ployed by the Cosmos people in theirA.N.P. coils. At the parasitic frequency,the currents in the two halves of the coilare in opposition to each other, whereas

at the true frequency the currents are inthe same direction at any instant. Twosmall anti -parasitic windings are coupledto the coil, one to each half, and are soarranged that the parasitic oscillationsinduce voltages in these anti -parasiticwindings in the same direction and thesystem acts as a short-circuited secondary.

At the normal frequency, however,since the currents in the two halves ofthe coil are in the same direction, thevoltages induced in the two sections ofthe anti -parasitic winding are in opposi-tion and no absorption takes place. Theidea is extremely ingenious and testsmade in our laboratories indicate thatthe remedy was effective.

"Astatic Non - pa ra sitic"The name A.N.P. stands for "astatic,

non -parasitic," which implies that thecoil is astatically wound. This is obtainedby winding the two main sections cf thecoil in opposite hand, and these astaticproperties are valuable in avoidingcoupling between neighbouring circuits.The inductance is only made in one type,having tappings quarter, half, and three-quarters of the distance along.

The coils fit a special holder providedwith six -spring contact strips, three ateach end.

Cosmos coils are made by Metro -VickSupplies, Ltd., of 155 Charing CrossRoad, W.C.2.

Are You BuildingThe Music Charmer ?

UNDOUBTEDLY one of the mostpopular three -valve designs published

by any radio periodical, the Music Charmer(WIRELESS MAGAZINE, March,. 1928)is giving pleasure to thousands of listenersall over the country. Anybody who ishesitating about building this fineset, should note this letter from a readerat Chalfont St. Giles :

I have made, I suppose, some dozensof super sets with varying degrees n.success, but was recently requested tomake the " cheapest possible " threevalve set and the Music Charmerstruck me as being eminently suitable.

Wherefore, I hied me to my box ofspare parts and with the addition ofsome of the cheapest material on themarket I made the set, exactly as speci-fied, except that 1 soldered all joints.

But, on testing the set, I found thatthe cheap loud -speaker I had bought forit was wholly inadequate for the terrificvolume it had to deal with -even German stations sounded like half -a -dozen jazz bands in the same room.

As a result my five -valve portable isdestined to be rent in small pieces tomake the Music CharMer-the bestthree -valve set I have made.(Blueprint No. W.M. 6o post free for is.)

WORLDS BROADCASTINGWave-length

inMetres

StationCallSign

eng thin

MetresStation

CallSign

II e -length

in

Al etresStation

CallSign

Wave-length

MetresStatiall

CallSign

24 Chelmsford 5SW Innsbruck 379.7 Stuttgart . 545.6 Sundsvall30 Bergen . Stoke-on-Trent 5S T 384.6 Manchester . 2ZY 555.8 Budapest.30.2 Hilversum Swansea . 5SX 391 Toulouse. . 566 Augsburg37 Vitus (Paris) : 297 Liverpool EL. V 394.7 Hamburg . Cracow .

37.65 Doebetitz Radio Agen 400 Bilbao . . Hamar . .

61 Paris . Ra.lio L.I. Hanover . Cork . . 6CK 575.8 Freiburg .158 Beziers . 300 Algiers . Cadiz . . EAJ3 576 Vienna (Wien)192 Akureyri . Bratislava Mont de Marsan Zurich . .

200 Biarritz . 302 Radio Vitus Plymouth . SPY 68o Lausanne .

204.1 Kaisersleutem 303 Nuremberg 401 Aachen . . 7zo Ostersund .

217 Radio Luzern -

b ur3C4300. I

Casablanca -

Belfast . 2BE405405.4

Salamanca .

Glasgow .EA j22

5SC76o766

GenevaLaibach

230236.2

Ste. EtienneStettin . .

30).2310

Zagreb . .

Oviedo . .408411

Reval . .

Berne775995.5

KievenLngraci

3.1 Bordeaux . 310.2 Marseilles . 412 Radio Maroc . 1,000 Leningrad241.9 Muenster . 312.5 Newcastle . 5 NO 416.7 Goteborg . Basle250 Gleiwitz . 319.1 Dublin . . 2RN 422 Cattowitz . 1,069 Hilversum HDO252.1 Bradford . 2LS 322.6 Breslau . . 423 Notodden . 1,080 Strasbourg

Cassel . . 326.1 Bournemouth 6B IVI 428.6 Frankfort 1,1 11 Warsaw .

Montpellier . 323.9 Almeria . . 434.8 Freidriksstad . 1,153 Kalundborg .

256 Kiel . . 330 Konigsberg . Seville . 1,180 Stamboul .

257 Juan-les-Pin, . 333.3 Naples . . 435 Wilno . I,190 Roden . .

259 Toulouse. . Reikjavik. . 441 Brunn . 1,250 KO nigswuster-260.9 Malmo . . 335 San Sebastian. EAJ3 448 Rjuiken . hausen-Zeesen LP272.7 Sheffield . . 6FL Cartagena . 448.4 Rome . 1,380 Motala

Bremen . 337 Copenhagen . 450 Moscow . 1,450 Moscow . . RDWDanzig . . 453 8 Stockholm 1,604 Daventry. . 5XXKlagenfurt . 340.9 Paris . Petit 458 Paris Ecole Sup. 1,700 Kharkov .

273 Limoges Parisien 460 Belgrade . . 1,750 Paris .

275.2 Dresden . . Huizen . 462 Barcelona . 1,800 AngoraNottingham . 5NG 344 Posen . 470 Langenberg . Bucharest

277.8 Leeds . 2LS 344.8 Barcelona EA 11 477.7 Lyons . . Norddeich278 Grenoble. . 348.9 Prague . 484.6 Berlin . . 1,850 Carthage283 Cologne . . 353 Cardiff . 5WA 491.8 Daventry Ex- Huizen .

Bordeaux . 357.1 Graz . perimental 5GB 1,870 Kosice .

280 Rennes . . 361.4 London . 2L0 500 Aberdeen 2BD 1,950 Huizen286 Lille. . . 365.8 Leipzig . 504 Porsgrund Scheveningen.288.5 Edinburgh . 2EH 370 Paris . Radio LL 508.5 Brussels . 2,000 Kovno289.3 Radio Lyon . 370.4 Bergen 517.2 Vienna (Kaunas)294.1 Dundee . . 2DE 375 Helsingfors 526 Milan . 2,650 Paris FL

Hull. . . 6KH Madrid . EAJ 535.7 Munich . 2,800 Temesvar

370

LEWCOS, COILS

lead again !

(Regd.)

`Q' COILS(Transformer and Aerial Coil

specified in the

"Q COIL FOUR "in

"Wireless Magazine" for May

Obtainable throughall radio dealers

15/ eachThe LONDON ELECTRIC WIRE CO. & SMITH'S LTD,Playhouse Yard, Golden Lane, LONDON, P.C.i

Ethovernier Dial,with Etholog and cardscales for recordingstation settings, 9/-

Burndept VariableCondensers

PRICES, without dialor knob :

SQUARE LAW.00007 mfds. - 13/6.000i mfds. - 13/6LOG LAW (as shown).0003 mfds. - 15/..coos mfds. - 15/6

Wireless Magazine. may, 1928

130c04eptamp:menu

f'lig5.t

orioshine

Five"ana

ct.ail Four

Five' and the ' Four"-see

Ra4,eLePticitgineo,./omponents

forthis i

the

:Seunsothithn:

0NCE again the judgment of experts onthe merits of the latest Burndept Vari-able Condensers and the EthovernierDial is confirmed by their inclusion intwo " Wireless Magazine " sets. In the" Sunshine Five " an Ethovernier Dialis fitted to ensure ease of control, and inthe " Q -coil Four," two Burndept" Log -law " Condensers (.0005 mfds.)with Ethovernier Dials are used.The Burndept Condenser has aninsulated spindle and metal earth shieldwhich definitely eliminates hand -capacity, while the design is such thatthe whole of the adjustment is carriedout on the bottom end cheek by meansof a cone seating on one side and asteel bearing on the other. No tensionbetween end cheeks-top cheek forsteady only. A wonderful improve-ment in condenser design. Fully dealtwith in Publication No. 32o, sent onrequest.With a ratio of 18-1, the EthovernierDial makes fine tuning easy. No gears-noiseless-and no backlash.Fit Burndept Components and makesure of good results. Your local radiodealer can supply.

ADJUSrASI, AVM MATERAI

For the " Log -law 'Condensers, printedwave -length scales,range 150-3000metres, can be ob-tained for use withclosed circuits.PRICE 1/6 per set.

BURNDEPTOffices - - Blackheath, London, S.E.3London Showrooms - 15 Bedford St., Strand, W.C.2

Advertisers like to know whence the business comes-please mention the " Wireless Magazine."371

Wireless Magazine. May. 1928

This Summer You Are Certain to Need

WEIGHSONLY5i lb.

NO elaborate introduction isneeded to explain the inclusion

in the pages of the WIRELESS MAGA-ZINE of a constructional articledealing with a portable cone loud-speaker. Many readers must haveuse for such an instrument, which isequally convenient both indoors andout-of-doors. "Portable" is literallycorrect in this case as the completeinstrument weighs only 514 lb. or soand is not at all bulky.

Better ReproductionIt is well known that a properly -

made cone loud -speaker will in most

Back view of the loud -speaker showing hois cut away

cases give better reproduction thanone of the horn type, particularly asregards the bass notes when used inconjunction with an amplifier incor-porating one or more stages ofresistance -coupled low -frequencyamplification.

Easily Made-At Low CostA further, and to the constructor,

the greatest advantage of this typeof loud -speaker is the fact that it can

APortable ConeLoud -speaker

Designed and Built by the " W.M." Technical Staff

be so easily made at home at a lowcost. Indeed, a home-made cone loud-speaker is within the range of almostevery listener's purse.

To get the best results it is foundadvisable to leave bothsides of the cone in " free "air andtherefore it is notthe best practice to putthe cone in a box, at anyrate, while it is in use.

In the particular modelillustrated on this page,provision has been madeso that both front andback of the containingcabinet can be easilyopened when the loud-speaker is in use. As amatter of fact, the dis-tance the doors are open effects thetone of reproduction considerably.

By providing two hinged sides inthis way the loud -speaker is adequate-

ly protected during tran-sit and when they areopened it can stand up-right on even the roughestsurface-a point of someconvenience when used inthe country or by the sea-side.

It will be seen that theinside of the cabinet isexactly 13 in. square, asize that will just accom-modate a cone made from

w rubber a piece of paper of 12 in.diameter.

A short distance from the front ofthe cabinet is placed a % in. woodfillet, as can be seen from the diagramon page 374. On to this is screwedthe front board which forms a bafflefor the cone.

The loud -speaker unit itself ismounted in position by means ofthree metal strips screwed to smallbrackets fixed inside the cabinet andthe position of the unit can beadjusted by altering the positions of

372

the fixing nuts holding the strips.Actually, all the essential details

are reproduced in these pages, but afull-size blueprint is available forthose who desire one. This, includes

Back and front of the loud -speaker open readyfor use

a template for cutting the cone paperexactly to the right size.

Half-price BlueprintsCopies of the blueprint (No. W.M.

73) are obtainable for half-price, thatis 6d. post free, up to the end of Mayif the coupon on page iii of the coveris used. Address your enquiry toBlueprint Department, WIRELESSMAGAZINE, 58/61 Fetter Lane, E.C.4.

All the necessary parts are detailed(Continued on page 374)

13

" 411 '

HOLE_ _

Jibki...thod13"

13,4.THICK

Details of front board or baffle

The Battery for the"Sunshine Five"

Portable Receiver describedin this issue.

VOLTS

99

Price

16/6

A Ripaults battery was used and is recommended forthis receiver for many reasons. Viz.: Reliability-Power-Compactness-Light Weight-Long Life.RIPAULTS SELF -REGENERATIVE H.T.

DRY BATTERIEShave been tested and proved to possess at least

50% Longer Lifethan any other battery. This, combined with their reliabilityunder all conditions of use, is why they are ideal for

portable receivers.WRITE FOR FREE "LIFE CHART "AND "RIGHT CHOICE TABLE."

THERE IS A RIPAULTS BATTERY FOREVERY RECEIVER. SEND US DETAILS OFYOUR SET AND WE WILL GLADLY ADVISEYOU WHICH IS THE RIGHT BATTERY TO USE.

The " Flat Dweller's Two "also described in

.0005 10/6

this issueTHE designer of this

receiver knew thatfor a set that was to

be used under adverseconditions the utmostcare had to be exercisedin choosing the rightcomponents to securethe desired results.

That is why twoRipaults Lateral ActionCondensers werespecified.

The r unique designgives them many definiteadvantages over all othertypes. It ensures Hair-line tuning which isessential for selectivity.It reduces capacity to aminimum. It results notonly in closer tuning,but in increased volume.It occupies less spacebut gives greaterefficiency.

Slow Motion Dials 4/3 Standard 4 in. Dials 2/3

From all Dealers. Many difficulty locally, order direct

KINGS RD., ST. PANCRAS, LONDON, N.W.1

Wireless Magazine, may, 1928

THEHEIGHT OF PERFECTION

LOBVECOPADIO

LOEwE

HIGH VACUUMRESISTANCES

AND

HIGH VACUUM BLOCK CONDENSERSARE

BETTERAdk for latufresad !cater

teinnummumetwomiuMMININIMIIIIIIIIMU111111111111111111111111111111111111111111111111111111}11111111101111g

TIE LOEWE RADIO COMPANY LIMITED,--1 4, FOUNTAYNE ROAD, TOTTENHAM,g LONDON, N.15 o

Triaphona: Tottenham 2076

.71111111111111111M411111111111111111111 LOEWE DI0iiiiiffilliiiiiiimiummininP

A New Igranic ChokeThe Igranic L.F. Choke, Type "G," is recognised as the finestchoke yet made for radio work. It caters for the man who wantsthe best at any price. Now Igranic have produced a choke-theType " F "-which offers really remarkable value. It caters forthe man who wants the best at a popular price.

The Igranic L.F. Choke, Type "F "

Price15/ -

Send for List No.J530 for particularsof the full range ofIgranic components

Works : BEDFORD

has a maximum inductance of 73henries but is so arranged that thesections can be connected in parallel soan inductance of 21 henries is obtained-an ideal value for use in an outputfilter.The iron circuit is ample to preventsaturation under normal working con-ditions and the whole construction iswell up to the usual Igranic standard,ensuring long life free from trouble.

etECTRIc

PUNIC)\,c9LTv

149, Queen Victoria Street,LONDON, E.C.4

Branches : Manchester, Birmingham, Cardiff, Glasgow,Newcastle, Leeds, Bristol

Advertisers take more interest when you mention the " Wireless Magazine."373

Wireless Magazine. M 1928

A Portable Cone Loud -speaker (Continued)

,..----.

/ con es, n x,x.

text 11,m

-1,11,./.1.

I

iX IX I

1 /X I /

X /I

MO X= \ I/

WIIILMC I 7 ,r,, t.t-,1- ,,

Lso-neum

7(

)

-Er- T

t -T-_,_ ,,:.,.... ft'..,

.

4.."4

...___,-----

,e -e Ner 7 WI( i vi arm BEIIIIII.X. Mel .... SRN' /MtW.*: ...-- I MI 6 1.1./0, - ).--4

in the list of components on this pageand as soon as they have been obtainedwork can be started. The dimensionsof the fixing strips given are goodboth for a Goodman's double-actingand ordinary reed unit, but if anyother make of unit is used will haveto be modified.

Front Board or BaffleAs soon as the cabinet has been

bought or built take out the frontor baq'e (the dimensions of this areindicated on page 372) and glue tothe back of it a sheet of thin rubberso that the hole is covered.

To be quite frank, in the originalWIRELESS MAGAZINE instrument arubber apron obtained from a famoussixpenny stores was used with greatsuccess !

As soon as this has stuck and theedges have been trimmed off round11.

COMPONENTS REQUIREDi-Cone loud -speaker unit (Goodman'.

double-acting or ordinary reed,Lissen or Bullphone).

i-Piece of cone paper, 12 in. square(Goodman or Six -Sixty).

2-71 in. lengths brass strip, I in. by/ in. (Goodman).

i-Cif in. length similar brass strip(Goodman).

3-i1 in. lengths brass strip, in. byyr in. (Goodman).

i-Rubber apron (price 6d.).3-I in. 4B.A. brass screws, each with

two nuts.3-1 in. wood screws.4-} in. wood screws.1-Cabinet with front board (Edwards).

This layoutcan be ob-

tained as afull-size blue-print for half-price, that is, Slight Tension on Rubber6d., post free,if coupon onpage iii of thecover is usedbefore May31.Ask for blue -

No WM73

the wood it can be screwed to thefillets in the cabinet. In this way therubber is clamped between the frontand the fillet.

Next mount the loud -speaker unitin position by means of the smallbrackets and strips indicated in thelayout diagram or blueprint.

Cut out the paper cone, stick alongthe edges to be joined and leave itto dry. We actually used special gold -finished paper supplied by Goodman'swhich looks very attractive in thefinished model.

As soon as this is dry cut a hole inthe rubber sheet about 8 in. or 9 in.diameter and push the apex of thecone through from the front. Theextent to which the rubber is cutaway is clear from the photograph of

the back of the loud -speaker repro-duced on page 372.

When the cone has been pushedthrough, fix it to the reed rod on theloud -speaker unit by means of theconical washers and nuts provided.

It will be observed that when thecone is properly fixed there is a slighttension on the rubber and an airtightcontact is provided without thenecessity of actually sticking the conepaper to the rubber. Anybody whowants to try out different kinds ofpaper for cones will find this is a very

FILLET

convenient method of mounting withwhich to experiment.

It will be observed that an adjust-ing nut is provided on the loud -speakerunit and this, in conjunction with theflexible type of bracket mount pro-vided, makes it possible to adjust theunit without difficulty to its mostsensitive position.

Details ofcabinet

Readers' Hints WelcomedBy the way, although it is true

that too many cooks often spoil thebroth, thousands of heads are some-times better than a few dozen (evenif the latter are specialised !) and theWIRELESS MAGAZINE Will always beglad to hear from any of its readerswho have new constructional ideasfOr . such instruments as this.

All About Moving -coil Loud -speakers in the Next Issue !

374

MOVING -COIL LOUD SPEAKERas ,',critted in

"WIRELESS MAGAZINE"(March issue)

Years of experience have resulted in the highestdegree of perfection in the design and constructionof GOODMAN:8 MOVING -COIL LOUD SPEAKER COMPONENTS. Ourproducts have stood the test of time-insist on Goodman's and be sureor the beat. We supply all parts for the Moving -roil Loud Speakerdescribed in the March Issue of the "Tee wireless Magazine."Fully illustrated and descriptive lints-free. Reprint of Wireless Magazine "article lel.)-/Mtep. int if required .1- Prim. pool free.

Trade Enquiries Incited.

OODMAN27 FARRINGDON ST. LONDON. E.C.4

GIVE A

r GOOD SETITS BEST CHANCE!

- 6

ATLASLOW LOSS COILS

re recommended for use in the"CRUSADER" and the"FLAT DWELLERS TWO"

Sets described in this issue-and no wonder. Thepatent twin -wire winding affords easiest possiblepath to H.F. Currents. Minimum Self Capacitycombined with Maximum Signal Strength makeClarke's "Atlas" the King of Low Loss Coils.

Prices : General Purpose Coils : Nos. 25/50, 2/6. No.65, 3/.. Nos. 75/150, 3/6. Centre Tapped Coils:No.40 for 201 to 400 metres and No. 60 for 350 to 600metres, 4/3 each. Special Coil for Daventry, etc., 6/6each. '`X- Coils: No. 60 Tapped at 7th and 12thturns, 5/6 each. No. 250 Tapped at 28th and 50thturns, 7/6 each. Short -Wave Coils: Size 2, 2/6, Size4, 2/7. Size 6, 2/8. Size 9, 2/9. The Set of 4, 10/-.

No Special Bases required.

Manufacturers:

R. CLARKE & CO. (M/cr). LTD.Atlas Works, Old Trafford, Manchester

Mention of the "Wireless

Wireless Magazine. May. 1928

SAVEMUCH

SPENDING

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it simplifies solderingFLUXITE

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H.T. Eliminator of ex-ceptional value, free fromhum, 5 tappings, givingfrom go to 15o volts, 5om/amp. Guaranteed forone year.

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HIGH-CLASS CABINETSWhy not get a really good cabinet ? It costs nomore if you get it from EDWARDS, whospecialise in high-grade cabinets for all popularsets. Cabinets for all " Wireless Magazine" setssupplied quickly at competitive prices.

MAHOGANY CABINETFOR THE " PORTABLECONE SPEAKER " des-cribed in this issue - 22/6

Write for illustrated catalogue, goat free from

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Magazine "

373

will ensure prompt attention.

Wireless Magazine. May 1928

Fit theLOTUS REMOTE CONTROL

to yourCossor Melody Maker

-and increase the enjoymentand comfort of good reception.Don't have a good set andrestrict it to one room. Recep-tion from your Cossor MelodyMaker can take place in everyroom in the house-indepen-dently - simultaneously - andwithout interference if you fita- LotusRemote Control.You can wire two rooms your-self in half an hour at a cost of afew shillings. Ask your retailerfor a free blueprint or send apostcard to the makers.For your Melody Maker youneed :-

1 Lotus L.T. & H.T. Relay,z Filament Control WallJacks, 2 Jack Plugs, 21 yds.4 -strand wire .. 30/ -Similar outfit, but for setusing H.T. Eliminator 45/ -This wires two rooms. Eachadditional room 7/6 extra.

11111U[S4/Ion taxi-mots

Recommended by the Makers of the Cossor"Melody Maker."

Made by the Makers of the famous LotusBuoyancy Valve Holder and Lotus

Vernier Coil Ho der.GARNETT, WHITELEY & CO., Ltd.,Broadgreen Road - LIVERPOOL

The Sunshine Five (Continued from page 298)

Having made or acquired thecabinet, the first operation is themounting of the receiver and thewinding of the frame. The loud-speaker framework is provided withthree radial arms, having holes 2 in.or 3 in. from the centre. Mark outthe holes in the grille to correspondwith the holes in the framework.

The loud-speaker.may then be heldin position by three 4B.A. screws,placed through from the outside andheld in position by a nut at the back.

The SunshineFive. in use

The loud -speaker should be arrangedso that the two leads come at thebottom right-hand corner of thegrille, where two holes are readydrilled for them.

Winding the Frame AerialThe next operation is the winding

of the frame, and this must be doneexactly as shown in the diagram. Theshort-wave frame is a simple single -layer winding, a close winding of14 turns of No. 22 -gauge d.s.c. wirebeing adopted. For the long -waveframe a three -section winding isadopted, the former being slightlyslotted. Each section contains 23turns of No. 28 -gauge d.s.c. wire,making 69 turns in all for the com-plete long -wave portion.

It should be noted that the short-wave frame is placed at the back ofthe former as far away as possiblefrom the earthed metal of the loud-speaker. The end of the long -waveframe is connected to the end of theshort-wave frame and three con-nections are brought out from thetwo sections.

376

This arrangement enables the twoframes to be put in parallel on theshort waves, which has been foundto give greater efficiency thanshort-circuiting the long -wave por-tion. For the long waves the short-wave frame is left "in the air," thisproducing no serious effects.

Earthing the Loud -speakerThe three points of the frame should

be connected to flexible leads whichare anchored in some suitable fashion

Take it on highground if you can!

and passed through the holes providedfor them in the front. Before leavingthis portion of the construction, themetal of the loud -speaker must beearthed, and since one side of theframe is always connected to L.T.-,this may conveniently be done bytaking a wire from the frameworkto the black flexible lead from theframe.

Incidentally, this connection of allmetal parts to earth, or in this caseto L.T.-, is an essential feature ofthe receiver, for unless this is donegreat trouble is liable to arise. Themetal work of the switch in thereceiver itself, and the metal casesof the two transformers, are alldefinitely connected to L.T.- toavoid difficulty.

Assembling the Receiver UnitThe construction of the receiver

proper may then be accomplished.The components have been arrangedin a three -bay formation. The H.F.components are at one end, thedetector components along the middle

(Continued on page 378)

WEA ITCOMPONENTSAre Absolutely Guaranteed.

Q COILS as specified byMr. J. H. Reyner -

Neutralising CondenserH.F. Choke

S.W.Anti-Microphonic Valve

Holder - 2/6Anti -Capacity Switch for

" Sunshine FiverW. G. 2 Tuner as incorporated in

" Gramo-Radio Four "

allll

dllll

JII

illhot

null

Hot

nd

ia

III

WRIGHT &WEAI RE, Ltd.740, HIGH ROAD,

TOTTENHAM, N.17

Phone :TOTTENHAM 3132

Telegrams" WRITEWEA,

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The Clix-Lox Plug solves all problems of faulty contactarising from the varying sizes of high tension and othersockets and eliminates all consequent reception troubles.Any degree of " fit" may be obtained by a turn of theinsulator, and by a final turn, the Clix-Lox Plug may

be permanently locked.With the advantage of instant connection and dis-connection is combined the security and permanency of

of an ordinary screw terminal.

ADJUSTABLE CONSULTRESILIENT Price 2.1d. each YOURLOCKING 2 DEALER

LECTRO LINX LIMITED254 VAUXHALL BRIDGE ROAD, S.W.1

Wireless Magazine. May. 1928

THE NEW

"AUTOGRAM"DOUBLE ELECTRIC GRAMOPHONEFitted with 2 Tone Arms, 2 Celestion Pick-ups, 2 12 -inchTurntables, Automatic Stopping Device for Motors, 2Universal Motors suitable for any voltage from 110 to240 volts A.C. or D.C., Speed Regulators, Pilot Lamps,etc., fitted in Substantial Leatherette Covered Mahogany

Cabinet. Price Complete £36.Quotations given for every type of design and outfit.

ONLY A FEW LEFT. AMPLIFEX LOOP AERIAL,the finest loop aerial yet devised, and the best for thereception of European Broadcasting. To clear 30/-.

OUR INTERNATIONAL RADIO CATALOGUE(3rd edition) will be sent to all enthusiasts sending td,

to cover ost of postage and packing

WILL DAY, LTD.(The Best in the West)

19 Lisle Street, Leicester Square, London, W.C.2Telephones: Regent 0921, on. Telegrams: Titles, Westrand, London

11

Componentsi nen t sARESPECIFIEDfor

SUNSHINE FIVE "" 1928 "LOG

CONDENSER.00035 and .0005

5/-Absolutely the Small-est, Lightest and mostEfficient obtainable.

Order for

FORMO DENSOR

"Sunshine Five" Ref. "C"Panel Type at 2/6

THE FORMO CO.Crown Works, Cricklewood Lane, N.W.2

Telephone : Hampstead 1787.

A high grade VariableCondenser costing nomore than a fixedcondenser. For use as :Neutralising Condenser.Aerial CondenserGrid CondenserReaction CondenserPhasing CondenserTone Control Condenser

Catalogue freeon request.

377

Wireless Magazine, May 19*J

NO VIBRATIONTOO LARGE

NO VIBRATIONTOO SMALL

IIIit 1

The one-piece springs in the Benjamin Valve-hol der absorb the heavy vibration from passinglorries or the light vibration of passing loot -steps with equal efficiency. They protect thedelicate valve electroies from all harmful Jolts,jai s and snocks. They prolong the life of thevalve indefinitely, banish microphonic noisesand bring a new purity to radio reception.Fit Benjamin Valveholders in every stage-buthe stile they are Be ijamin because no other,alveholde s embody all the essential featuresfound in Benjamin.

FOR THEAtAN

VAINEHOLDERFrom all radio dealers 2/- eachAlso fit the Benjamin Battery Switch-the most efficient L.T. Switch.It's OFF when it's IN. Price V-.

The Benjamin Electric Ltd.Brantwood Works

TARIFF ROAD, TOTTENHAM, N.17

The Sunshine Five (Continued)

and the L.F. along the other end.The front of the baseboard is there-fore cut away slightly in the middleand the panel is set back a shortdistance.

The H.F. unit is mounted at theleft-hand side of the panel on thebaseboard, the two Mullard trans-formers are mounted just to the rightof the centre and the two L.F. valveholders are mounted on the right-hand bay. The panel merely containsthe tuning condenser, the reactioncondenser-a Gambrell Neutovernia-and the range switch.

Aerial and Filament SwitchThis switch controls the frame and

filament circuits. In the middleposition, the filaments are switchedoff. In the one position the filamentsare switched on and the frame isconnected in the short-wave position,while in the opposite position thelong -wave connection is adopted, thefilaments again being switched on.The one switch therefore controls thewhole circuit.

The actual position which thesecomponents will occupy is clearlyindicated in the diagrams accompany-ing this article.

Mark out the panel and mount thecomponents in their proper positionsfirst of all. Then lay out the com-ponents on the baseboard as indicatedby the wiring diagram and place thepanel temporarily in position in orderto ensure that there is adequateclearance. There is naturally verylittle latitude in the spacing of thesecomponents, and the layout mustbe followed rigorously.

Before wiring up is commenced thedetector potentiometer must be made.This consists of 8 yards of No. 43-guage enamelled Eureka wire woundon a 1/4 in. ebonite rod, a tappingbeing taken at 2 yards. This gives aresistance of 500 ohms with a tappingone quarter of the way along fromthe negative end.

Wiring Up the ReceiverThe receiver portion may then be

wired up, and the early stages of thismay be conducted without the panel,in position. The connections betweenthe B.F. unit and detector and themajority of the L.F. connections maybe completed at this stage. The panelmay then be mounted in positionand the remaining wires connectedup.

The actual battery connectionsare made by a battery cord taken tothe appropriate points on the circuit.It should be noted that the high-tension connection to the H.F. unitis brought by means of a stiff wire toa binding post at the right-hand endof the panel looking from the back.The H.T. connection is then taken tothis point.

Making the Binding PostThe binding post is formed by a

simple screw passing through theebonite, and on the front side of thepanel a nut and washer is providedwhich enables the loud -speaker to beconnected up when the receiverportion is placed in position. Similarlytwo of the frame connections arebrought to screws passing through

(Continued on page 380)

VALVES TO USE IN THE SUNSHINE FIVE

Alal,e.1st tt..P. and

Detector. 2nd H.F. 1st L.F. and L.F.

B.T.H. ... ... B21oH - B2 ioL B215P

Cossor ... 2 zoRC 2 'OLP 2 IOLF 220P

Cosmos ... ... SPI8B - SPi8R SPrfiRR

Ediswan ... - DR2 GP2 PV2

Marconi ... ... DEH2ro HL2i ) DEL2ro DEP215

Mullard ... ... PMIA PMiHF PMILF PM252

Osram ... ... DEH2io HL2io DEL2ro DEP225

Six -Sixty ... ... SS2zoRC SSzioHF SS2roI,F SS23oSP

378

Wireless Magazine. May 1928

WIRELESS CABINETS in SOUND QUALITY of WOODHighly Polished First-class Cabinet WorkMAKERS OF ALL DESIGNS FOR OLD AND NEW WIFELESSSETS AS PERIODICALLY ANNOUNCED IN THIS JOURNALSpecial line of closed cabinets totally enclosing Batteries and Accessories

Thousands of satisfied users. Send for Illu:-,trated Price ListMoney returned if quality and workmanship not equal to our guarantee

CAXTON WOOD TURNERY CO., MARKET HARBOROUGH

THE °LIMA MUnspillable Celluloid Accumu-lator 2 -volt, co -amp. actual,

19/6THE OLDHAM

UnspillableCelluloid Accumula-tor 2 -volt, 12 -amp.actual 14/- isspecified for the"SUNSHINE FIVE"described in this issue

Here is theIdeal

Accumulatorfor PortablesTHE Oldham "Faithful

Service" Unspillable Ac-cumulator has been designedwith the sole idea of givingthe most efficient results inportable sets. It will standrough usage, and is guar-anteed not to leak. Theplates are particularly robustand long lasting, being madeunder the Oldham SpecialActivation Process.Summer days will soon behere. See that you give yourportable set the accumulatorit deserves-the long-lasting," Faithful Service " Oldham.Obtainable from all Dealers.

Oldham & Son, Ltd., Denton, Manchester Telephone : Denton12 tLondon Office : 6, Eccleston Place. Telephone: Sloane 7227/8Glasgow: 75, Robertson Street, C.2. Telephone: Cent? al 105

M 2513

OUR BLUEPRINTSERVICE

Constructors of receivers described

in this journal should make fulluse of our Blueprint Service and

avoid all risk of failure.

WHITELEYBONEHAMCABINET CONE

SPEAKERSThe Whiteley BonehamCabinet Cone gives utmostvolume with perfect fidelityof tone: driving unit, coneand cabinet are all designedwith this one end in view.

All Bakelite Cab- e A 4met Model ..Oak or Mahogany 53

Write for Lists.

# When building a set, re-' - member ntt.phoni,

Valve

WHITELEY BONEHAM & CO., LTD., Nottingham Road, Mansfield, Notts.

VOGT ELECTRO-STATIC LOUD -SPEAKERNO CONE NO MAGNET

12 in. DIAPHRAGMAbsolutely natural renderingof speech and Chamber Music.No deformation over wholerange of acoustic frequen-cies.Every instrument distin-guishable.M akes any good R.C. coupledset a radio musical instrument.Hitherto unattained at theprice in such compact andpleasing form.WITH BAFFLE. WALNUT,MAHOGANY - - - 27 7WITH METAL STAND (as inns-trated - - - - - 55 5UNIT ONLY - 24 12 6

Trade Enquiries InvitedA. M. E SHERWOOD,

68, HATTON GARDEN, LONDON, E.C.1

Advertisers like to know

BUILDING A PORTABLE ?

Send a p.c.to -day!

whence the business comes

379

You will find a Cameo Portable Cabinetanswers every requirement satisfactorily.Specified by the leading set designers,Write for full particulars of all Cameo

Cabinets.

" IDEAL" MODELBuilt to accommodate any cane unit,complete with inner frame, baseboard,lock, nickel -plated fittings, etc.Oak - 52/6 Mahogany . 58/-

CARRINCTON MANUFACTURING CO.' LTD.

Cameo Works, Sanderstead Road,SOUTH CROYDON.

please mention the " Wireless Magazine."

Wireless Magazine, May, 1928

PROTECTIONat LI vital pointsin the circuit

VALVE -SET OWNERS are rapidly realisingthe enormous importance of incorpora-

ting an accurate measuring instrument inseries with the valve circuit itself.Without this protection there is no definitemethod of obtaining that vitally importantadjustment of plate and filament current.Newly charged accumulators for instanceregister .25 volts above normal. Without aSifam Radio Meter you cannot adjust thisexcess. Reception appears the same, but thelife of your valves is reduced by hundreds ofhours !Haphazard control is out of date. Modernset design demands Sham accuracy andSifam protection !Follow the lead of over 250,000 listeners whohave learned the wisdom and saving byusing Sifam Radio Meters.Your dealer will gladly show you the popularpriced range, or write direct for leaflet" Detecting Distortion," free from

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RADIOslFAI'METERS

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The Sunshine Five (Continued)

the panel at the opposite end of thereceiver, the third connection goingdirect to the H.F. unit.

The receiver is now ready formounting. It should be placed in therecess provided for it with the base-board towards the back and the paneluppermost. It may their be held inposition by means of wood screwspassing through the baseboard intothe wooden partition behind.

Connecting Up AccessoriesIt now remains to connect up the

batteries, the loud -speaker and theframe aerial. The battery cord ispassed through the slot cut for it inthe partition. The two loud -speakerleads are connected direct to theappropriate points. The back leadis connected to the anode terminalon the last valve holder, while thered lead is connected to the H.T.binding post previously referred to.

The frame leads are brought straightacross the battery compartment,through the three holes provided forthem and are connected up as follows:The red lead goes to the grid terminalon the H.F. unit. The second lead,coloured maroon in my model, passesto the first binding post, while theblack lead passes through the secondbinding post, which is connected toL.T. - . It is now only necessary toconnect the leads to the batteriesin order to complete the assembly.

The valves may then be insertedby opening the flap at the end of theset. Recommended valves are shownin the table on page 378. A pecu-liarity of the set is that the secondH.F. valve is somewhat microphonic,and owing to the fact that this ismounted in a rigid holder troublemay arise from this source. It isadvisable, therefore, to choose a goodvalve for this position. The detectorvalve is also microphonic to a some-what lesser extent. It is a good planto pack the two H.F. valves withcotton -wool, as this avoids shock.

Sound Waves from Loud -speakerThis is particularly important in

between the top cover and the valves,for it is here that sound waves fromthe loud -speaker impinge. Troubleof this sort is always serious withportable receivers, and it is worth alittle time finding the best valve forthe particular position.

The detector H.F. voltage should

380

be between 5o and 6o volts, the bestposition being found by trail. Theother H.T. tap is plugged into thefull amount. Then on switching onthe receiver no trouble will be foundin finding the various stations.

The test report accompanying thisarticle gives some idea of the stations

METAL FRAME17OF LOUD -1 ) SPEAKERtlII ,

IL.CONTACT ON RANGESWITCH CLOSED IN `,SNORT WAVF, POSITION

Diagram showing frame aerial andloud -speaker connections

which have been received at Elstreeafter dark. (See page 298).

Those marked * can lie. receivedat comfortable loud -speaker strengthduring daylight; and this, of course,is the 'most important feature, sincethe set will normally be used duringthe daylight hours. Pressing theswitch away from one sets the receiverin the short-wave position, whilepulling towards one changes theconnections for long -wave reception.

Handling the Reaction ControlThe reaction control will be found

to increase as the wavelength isreduced, this being a peculiar featureof the receiver and one which makesit rather different from the usual.

In 'searching for stations, there-fore, it is best to run up from thebottom of the scale, gradually re-ducing the reaction as required, andin this way no trouble will be foundin plotting a number of stationswhich may be duly recorded on thestation log mounted on the coverplate.

The Formodensor across the firsttransformer must be adjusted to givethe required reaction effect on thewhole range. It should be about themiddle of its travel. Swinging theknob in decreases the reaction effect.and vice versa.

The VogtElectrostatic Loud-

speakerANUMBER of WIRELESS MAGA-

ZINE readers were particularlyinterested in the description of theVogt electrostatic loud -speaker whichwas fully described in our previousissue (" Some New German Loud-speakers," page 212).

We are lad to beable to inform themthat these loud-speakers can be ob-tained in Englandfrom A. M. Sherwood,of 68 Hatton Garden,London, EL.'.

This firm weregood enough to letus have one of theloud -speakers fortestand we found thatwith a well -designedamplifier .the qualityof reproduction wasvery good indeed.

The loud -speakerwill appeal particu-

larly to experimenters for the prin-ciple on which it works is quite newto most British amateurs

Wireless Magazine. may, 1928

TEST REPORT OF THECRUSADER

(see page 322)

Aerial ReactionWave- Con- Con -

Station length denser denserVienna ... 517 47° 139°Brussels ... 508 139°Daventry

(5GB)* ...Berlin ..Langenberg*Rome ...Frankfurt*KattowitzHamburg*Stuttgart. .

London(2L0)* ... 365

Bourne-mouth ... 326 6o° 100°

Nuremberg 303 49° 92°Cologne ... 278 42° 83°

492483470452428422396379

134°

133° 132°127° 130°123° 128°

123° I

io8° 122°Ira°

102° 120°90° 116°83° It75° 109°

* Received at loud -speaker strength.Coils used were : Aperiodic, No. 35 ;Grid, No. 6o; Reaction, No. 5o

Station.2NM*EindhavenPCMM2XAD

Aerial ReactionWave- Con- Con -length denser denser32.530.2

21.9

12° 130°49° 52°44° 47°28° 42°

Coils used were : Aperiodic, No. 2;Grid, No. 4; Reaction, No. 6.* Coils used were Nos 2, 6, and 4

in above order.

WHAT IS WRONG WITHBROADCAST DRAMA ?

To the Editor, WIRELESS MAGAZINE.C IR,-In your April issue there

appeared an article by me on broad-cast drama.

In view of recent events it seems thatthe article in question must now showup in rather a poor light. We have hadThe Master Builder, which was magnifi-cently done. We have had an extra-ordinarily fine piece of work from thepen of Mr Cecil Lewis in the shape ofThe Night Fighters. And we have beengiven a very rare treat in The Man ofDestiny.

If such material is going to be thefoundation of broadcast drama in thefuture, then it is very possible that theradio play will develop into a genuinemeans of artistic expression In fact,after having heard The Night Fightersand the splendid message it put over,one is almost inclined to think that sucha condition has already come about;and the special drama station wouldconsequently not be quite such a"loathsome " thought.

No doubt if the B.B.C. gave the publicany large number of plays which couldby any. conceivable means be- regardedin the light of pamphleteering, righteouspeople in Golders Green and Tootingwould stand on their hind legs and yap.But that does not matter in the least.They are the very same people who thinkNoel Coward ought to be in prison.

Mr Shaw was hailed as a pamphleteerat first and some peculiar people lookupon him in the same light to -day, butthe majority prefer to call him a verygreat artist.

If the B.B.C. are going to put outplays which are truly artistic in that theyare didactic, then the public should givethree cheers for the dramatist who adaptshimself to the new method of expressionand another three cheers for Mr. CecilLewis, who has practically created thatmethod.-DALLAS BOWER (Brighton).

RECEPTION FROM POLANDTo the Editor, WIRELESS MAGAZINE

SIR,-While looking through a recentissue of the WIRELESS MAGAZINE, Inoticed that Jay Coote, in his "Con-tinental Notes," said he doubted verymuch whether the Wilno station wouldbe heard on this side of the Channel.

In this connection it may interestyour readers to hear that I picked upthis station quite easily on a simpletwo-valver (detector and L.F.).

This may have been in the nature offreak reception; but on several eveningsrecently I have heard the Posen stationat quite good strength. A few nightsago, when Posen was relaying a pro-gramme from Warsaw, the intervalsignal consisting of the morse letter W,could be heard quite distinctly on asmall loud -speaker at a distance of afoot or so from the horn.-W. OLIVER(Wandsworth Common).

381

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Wireless Magazine. slit.. 19281

NirelessMagazineREFERENCE SHEETS

MNOI T

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Clips ..I Loewe .25-megolun Resistance and

ClipsI E.B .005 microfarad Fixed Condenser2 B.B. .0003 Fixed Condenser ...1 Terminal Strip, 12 in. by 2 in., ready

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This set can be supplied ready wired and tested orany components separately.Lists dealing with Sunshine Five, Gramo RadioFour, Crusader Two, Master Three, MelodyMaker, 1928 Solodyne will be sent on receipt ofT. stamp.Carnage and packing free in British Isles on cashorders value £2 and over.

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WIRELESS MAGAZINE Reference Sheet

Three -stage Power AmplifierTHE construction of a three -stage (four -

valve) L.F. amplifier is not an easy matterowing to the great tendency for feed -back, dueto the common impedance of the battery orbattery eliminator used to supply the high-tension voltage.

With an odd number of stages the effect ispositive and definite reaction effects are pro-duced, which, even if they do not cause oscilla-tion or "motor -boating," will give rise to seriousdistortion. With even numbers of stages theeffect is negative and causes a reduction in theamplification, which again introduces distortion,for the regeneration varies with differentfrequencies.

Any really distortionless amplifier, therefore,must take account of this feed -back, due to thecommon impedance, even when batteries arebeing used, while if the battery eliminator isemployed, the relatively larger impedance of thefiltering circuit inevitably introduces troubleunless special precautions are taken in theamplifier itself to combat the effect.

The amplifier shown on Sheet No. 6z wasparticularly designed to overcome this trouble.It was used in the WIRELESS MAGAZINE Labor-atories with an eliminator delivering 30o volts,but the system shown could be used satisfac-

No. 61

torily on smaller voltages, in which case theresistances in the anode circuits would have to besuitably reduced. In the first place twoentirely separate filter circuits were employedin the eliminator, these being connected toH.T,+ t and I -1.T. +2 on the amplifier. Thevoltage on these two points was equal, but theywere supplied through separate circuits.Secondly, the detector and first L.F. valveswere fed through resistance -capacity filters.This is a well-known method for stopping'motor -boating," and was referred to in SheetNo. 43 -

On the second L.F. valve, the actual voltageon the anode was required to be higher thanbefore, and in consequence a resistance of theorder of 30,000 ohms could not follow it,and a value of something nearer to,000 ohmswas used. This is insufficient to act as aresistance -capacity filter, and it was necessaryto insert a choke in this lead. The list valvehas the full high-tension supply to the anode, achoke output circuit being used for the loud-speaker.

Dual -impedance couplers were used for thelast two stages, a simple resistance -couplingstage being employed in the first. The valvesemployed are specified on Sheet No. 6z

WIRELESS MAGAZINE Reference Sheet No. 62

Three -stage Power Amplifier (Continued)

STOPPERCMOKL011T+1I MOO \

0.5 MR

GB -1

I1/4c>

0111+2

0C.

7L5.

0L5.

q13 -r5 OHT-

OLT+

OLT-The design of this amplifier has been discussed on Sheet No. 61. Thevalues of the components are marked .on the diagram above. The followingvalves were used:-Vs, Cossor 610 H.F. ; V2, Cossor 6i o L.F. ; V3,Cossor 610 P (Stentor Six); V4, L.S. 5 A. Valves of other makeshaving similar characteristics may, of course, be substituted for those

shown if desired

382

WIRELESS MAGAZINE Reference Sheet No. 63

Vreeland CircuitONE of the principal difficulties which arises

in a high -frequency amplifier is that ofobtaining the necessary fidelity of reproductionconsistent with sharp tuning. For satisfactoryquality, it is necessary th it the circuit shallreceive all frequencies within at least 5 kilo-cycles on each side of the resonant point, and itshould theoretically give all such frequenciesequal preference.

VreelandCircuit

Outside this Unlit, however, it should cut offvery rapidly in order that any interference maybe tuned out as completely as possible. Theordinary resonance curve is incapable of pro-ducing an effect of this nature, for it gives asharp response at the resonance point, but fallsaway rapidly on either side, so that the higher

frequencies are notproportion.

To overcome this difficulty, a series of cascadecircuits is usually employed, these circuits beingincorporated in a high -frequency amplifier.Even this method is not always satisfactorywhere extreme selectivity is required, and thecircuit illustrated in the diagram has beenevolved by Doctor Vreeland, in America, to givea definitely fiat -topped resonance curve.

It will be seen that there are two tuned cir-cuits coupled to each other through a commoninductance, and both tune together with a gangcondenser. Any two circuits so coupled will pro-duce a double -hump resonance curve havingtwo peaks, which may be close together or farapart, according to the extent of the couplingbetween the circuits. By suitable adjustmentof the coupling, these two humps can be madeto occur close together, so giving a flat-toppedresonance curve with steep sides.

This is just what is required for extremeselectivity with good quality, and is the objectin view in utilising this special arrangement.

received in their proper

WIRELESS MAGAZINE Reference Sheet

Metal RectifiersA FORM of rectifier which is likely to prove

popular in the future is the Westinghousemetal rectifier. This consists of discs of copperand cuprous -oxide in contact. Such a combina-tion has the property of passing current muchmore easily in one direction than in the other.

A rectifier unit is built up as follows : Thereis first a thick disc of copper. Then a disc oflead, followed by a second thin disc of copper.Next is a thin copper disc oxidised on the topside, followed by a second disc of lead, and asecond thick disc of copper completes theassembly.

The active elements are the thin copper andoxidised copper discs in the centre. The leaddiscs are placed to ensure good contact and thethick discs on the outside are to give the wholeunit rigidity. The unit is clamped togetherwith a strong pressure, and is thus permanent inits characteristic.

The actual forward resistance of a rectifierunit (that is, the resistance in the direction forwhich the unit is a conductor) varies with theactual size, but is usually a small fraction of anohm only, so that the voltage drop on the recti-fier is comparatively small. The reverse resis-

No. 64

tance is well over r,000 times as high, and thusvery little reverse current flows. The arrange-ment forms a simple and efficient rectifier,which can be built up into various formations foruse with the circuit required.

The principal disadvantage of such units istheir inability to stand prolonged overload. if

cuativitic DISCCOPPER

DISCS_.....,=r0t1cl.L4TAD/-*DISCS

tr5CPERWITtlTOP bORFOCL kCLAMPIII4 DISC

OXIDISED

Arrangement of Metal -oxide Rectifier

the current exceeds the rated value for a con-siderable period, excessive heat is generated andthe oxide coating on the rectifier disc is destroyed.Provided reasonable care is taken, however, nodifficulty of this nature arises in practical useand the unit is no less serviceable on thisaccount, for a valve rectifier will not stand anoverload for any prolonged period.

WIRELESS MAGAZINE Reference Sheet

Short-wave AdapterTHOSE readers who have receivers includ-

ing two stages of high -frequency amplifica-tion can tum their sets into efficient short-wavereceivers by adding superheterodyne adapterson the front. This consists of a suitable oscillat-ing detector, which converts the received short -

SHORT -WAVE. CHOKE

:T+

HE CHOKE

00015

.0001.5TO GRID OF 151CF VALVE.

Short-wave AdapterCircuit

wave oscillations into a much lower frequencywithin the normal broadcast band.

To operate the arrangement, the broadcast

No. 65

receiver is tuned in to some definite wavelength.The aerial is then removed and connected to theshort-wave adapter. The short-wave signals arethen tuned in on the adapter, using this assuperheterodyne receiver in the normal mannerwhile the broadcast receiver acts solely as anintermediate and low -frequency amplifier andis not touched.

Owing to the removal of the aerial from thefirst circuit, it may be necessary to retune thecircuit again in order to obtain the best results.After this has been done, the exact settings onthe various condensers should be noted forfuture reference, so that the broadcast receivercan always be set in a suitable position forreceiving the short waves.

A diagram of connections, with values, isappended. A short aerial system only shouldbe used to minimise the radiation from the con-tinuously oscillating detector, but as thisoscillation is different from that being received,it will not cause interference to others receivingthe same programme.

383

Wireless Magazine, May, 1928

PRICE 1/6 EACH. Send for Catalogues

PERFECT TERMINALS

The unique advantages of theBelling Lee patented terminal :-

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are indispensable for every set.Write for List V.36.

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Wireless Magazine. May. 1928

READY RADIO SUPPLY C°:41 Newcomen Street, London Bridge, S.E.1

PRICE LIST OF COMPONENTS FOR"Q -COIL FOUR"

1-Becol Ebonite Panel2-Burndept .0005 Variable Condensers with

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12-Bellies::-Lee Terminals, as specified1-Cyldon .0002 Reaction Condenser1-Linen Push-pull Switch ..

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1111111

Test Report ofAll -the -World Five

StationStettinMuensterCologne ...NurembergBreslau ...Petit ParisienLondonMadrid (EA J7)KattowitzFrankfurt ...Rome ...Paris (Ecole Sup.)LangenbergDaventry (5GB)

A nodeCondenserReadings

10182634556572788295

Ioozio155

LONG -WAVE STATIONS

5XX ... ... 145Hilversum ... 90

The above test report refers to thereceiver described on page 107 of theMarch WIRELESS MAGAZINE.

Sifam H.T. VoltmeterIN our previous issue (page 282) we

reviewed a Sifam H.T. Voltmeter.This instrument has been specially de-signed for testing mains units where avery low current consumption is required.The consumption on a full-scale deflec-tion, however, was stated in our testreport to be 8 milliamperes, whereas itshould be 1.8, this figure corresponding toa resistance of nearly 1,25o ohms per volt.Such a meter would consume only afraction of the total current flowing inordinary practice since receivers demand-ing as much H.T. as zoo volts wouldnormally consume at least io milliam-peres, and probably considerably more,while receivers of smaller current con-sumption would only require ioo or 120volts, in which case the current takenby the meter would be less than .1milliampere.

Catalogues and.Pamphlets

ALITTLE booklet from GambrellBros., Ltd., of 76. Victoria Street,

S. W gives some interesting informa-tion on the subject of Gambrell com-ponents.

An attractive and fully illustratedcatalogue of Deckorem products hasbeen sent in by A. F. Bulgin & Co., of9-11 Cursitor Street, Chancery Lane,E .C.4 .

The "lateral action" condenser isdealt with in a leaflet from Ripaults,Ltd., of King's Road, N.W.I.

The Dubilier Condenser Co. (1925),Ltd., of Ducon Works, Victoria Road,North Acton, W.3, have sent in a recentissue of their catalogue and price list.

From J. J. Eastick and Sons, of EelexHouse, 118 Bunhill Row, E.C.r, we havereceived a catalogue of apparatus.

384

Bulgin & Co. ...BurndeptCarrington Mfg. Co., Ltd....Caxton Wood Turnery Co.Clarke, H., & Co., Ltd.Day, Will, Ltd.Dubilier Condenser Co., Ltd.Eastick, J. J., & Sons, Ltd.Edwards, F. W. ...Electron Co., Ltd.....Fluxite, Ltd.Formo Co., TheGambrell Bros.Garnett, Whiteley, & Co., Ltd. ...GoodmansGraham Farish Mfg. Co. ...Igranic Electric Co., Ltd.Lectro Linx, Ltd. ...Lissen, Ltd.Loewe Radio Co., Ltd., The ...London Electric Wire & Smith's,

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IllYTYVVYYTTYVVV7Y7TVVV7TVE

BALANCEEVERYTHING depends upon getting the

Valves in your wireless set to pull together.

You would not suddenly put Jack Hobbs,excellent cricketer though he be, into theCambridge boat and expect him to pull stroke.

Why then buy an assortment of valves ofdifferent makes for your set and expect themto give balanced reproduction ?

It is balance first and balance every timethat you require amongst your valves, that iswhy you should fit a set of SIX -SIXTY Valvesto your receiver without delay.

Ask your Dealer for SIX -SIXTY Valves byname and accept no other.

Wireless Magazine. May, 192.E1.1

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111

Ha"-BLUEPRINTCoupon Valid until

Price May 31, 1928FOR ANY ONE BET CONSTRUCTIONALLY DESCRIBED IN THIS ISSUE.

Fe1:7f INFORMATION Coupon Valid untilMay 31, 1928

NOT MORE THAN TWO QUESTIONS TO BE ASKED if A net.

Wireless Magazine. may, 1928

4NEW WONDERTRANSFORMERWITH THE SILVER.WINDING AND THE

IN1ULLARDPERMACORE-

THE new Mullard " Permacore ' Transformer is absolutely revolutionary in designand construction. No transformer so

compact and at the same time so efficient hasever been produced. It is a master productgiving better results than the best of the bigones. The reasons are these :(1) The iron in the Mullard " Permacore " is a speciallytreated and scientifically prepared material, carefullyhandled in manufacture to preserve its high permeability.(2) This high permeability allows a high flux density to beused without any possibility of saturation in an ironcircuit of exceedingly small dimensions.

As pure inreproduction asthe silver of its

winding

PRICE251-

(3) The windings ot the Mutlard Transformer havebeen so selected that no resonant peak occurs atabout 8,000-10,000 cycles as is usually the case. Thiseliminates all shrillness.

(4) The primary is wound with silver, the secondarywith nickel. Silver for the primary has the advantageof good conductivity and no deterioration. Nickel forthe secondary has the advantage of high resistance andmagnetic properties.

(5) The amplification ot the Mullard Transformer ishigh and uniform at all frequencies from 250 cyclesupwards, below this limit, even at 50 cycles, giving alarge percentage of its full amplification.

The only Transformer that can be used in the Sunshine FiveullarMASTER RADIO

No shrillness.Resonant peakseliminated.

Printed in England: Published by BERNARD JONES PUBLICATIONS,' LTD., 58/61 Fetter Lane, London, E.C.4.Sole Agents for Africa: CENTRAL NEWS AGENCY LIMITED. Sole Agents for Australasia GORDON & GOTCH LIMITED. May, 1926