Post Office Hypocrisy - worldradiohistory.com · Vol. 4, No. 23 OCTOBER 8, 1924. Price 6d. net. Post Office Hypocrisy GENERAL indignation has been aroused by the growing ten-dency

Wireless Weekly, 6d. Net Wednesday October 8th, 1924

and the Wireless Constructor.

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%,How Valves are Made. -id;Jottings By The Way, Watch Your

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g ,H.T. Battery, Valve Notes, Random 7, -

Technicalities, Apparatus We Have r'-'

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CONTENTS100 Metres and Below.

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Post Office Hypocrisy

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2 WIRELESS WEEKLY ADVERTISEMENTS OCTOBER 8TH, 1924

New Burndept Wireless Apparatuswith special features.

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THEVAL

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ETHOPHONEA

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for Five Guineas.F you desire loud speaker reception

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=; At five guineas this fully -guaranteed,rigidly to a panel, or base, and a valve t1 -2 simply -controlled instrument of realholder which " floats " on springs inside. Burndept efficiency represents the finestthe shell. There is no capacity between I a value in wireless apparatus that hasthe sockets as there are no nuts on them. ever been put on the market. TheThe risk of short circuits is eliminated Ethophone-Duplex will receive broad -owing to special construction. A special

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20 miles of a normal power broadcaststation, and about 100 miles of the

i I 111

withdrawn. The advantages of fitting The illustration shows howin the Anti -PhonicAnti -Phonic Valve Holders to sets, valve11_4rr

vibrates when

high -power station. The range onhead telephones is four or five times

especially portables, are very obvious. tapped. Normally, the as great. Bright -or dull -emitter valvesNo. 401. Anti -Phonic Valve Holder. Diameter springs in the base protect may be used without alteration to the2i ins. height just over I in. For panel or base the filament from shocks.mounting, 6s.

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. r ing on any paneE from 136 to 1 inch in thickness : coils, batteries etc., with instructions. Price,No. 916. Capacity .00)5 mfds. ... £12s. 6d. £5 5s. Od., to which must be added il 5s. Od.No. 417. Capacity 001 mfds. .. £1 7s. 6d. Marconi Licence.

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Assistant Editor:PERCY W. HARRIS.

Scientific Adviser :Prof. G. W. 0. HOWE,

D.Sc.,

Advisory Editors:Prof.R.WMDD/NOTON,

M.A., D.Sc.Prof. C. L. PQRTESCUE,

M.A., M.I.E.E.

ilabio presis, Ltb.BUSH HOUSE, STRAND, W.C.2.

Tel.-Central 4048.

BY JOHN SCOTT-TAGGART, F.Inst.P.,A.M.I.E.E.

S.'aff Editors:E. H. CHAPMAN,

M.A., D.Sc.A. D. COWPER,

M.Sc.R. W. HALLOWS,

M.A.G. P. KENDALL,

B.Sc.S. G. RATTER,

Member I.R.E.

Vol. 4, No. 23 OCTOBER 8, 1924. Price 6d. net.

Post Office HypocrisyGENERAL indignation has been

aroused by the growing ten-dency of the Post Office toimpose restrictions on wireless

transmission, and, although wirelesstransmitters are only a small sectionOf the experimental movement, yet,nevertheless, they represent an ex-tremely iniportant section, and theywill be backed to the full by all whohave any interest in experimentalpt. -ogress.

-It is with great satisfaction that wenotice that the Radio Society is nowtackling the problem of Post Officeinterference. The mutual admirationsociety, which has hitherto existedbetween the official amateur associa-tion and the Post Office has brokendown, and although a prominent offi-cial of this Government departmentadmitted to a Press representativethat he " greatly admired Dr.Eccles," we are glad our President isgetting down to solid facts.

Put bluntly, the British Post Officehas consistently placed obstacles in theway of experimental progress, and theRadio Society's protests have been aswater on a duck's back.

After the war, the Post Office main-tained for an unnecessarily long periodonerous restrictions as regards wirelessreception. In August, 1922, theystrongly opposed any broadcast trans-mission at all in this country, but aftermuch trouble the Radio Society obtainedfrom them a half -an -hour transmissionfrom Chelmsford each week, by meansof continuous waves. " It is regrettedthat it has not been found possibleto agree to the inclusion of wirelesstelephony in the arrangement," readsa letter dated August 19, 1922. Herewas an important radio society humblyrequesting some co-operation from theBritish Post Office, -who, however-,, re-gret -that they cannot even permit a

few minutes telephony to be broad-cast.

This is a typical example of a con-sistent Post Office attitude, and itseems positively ludicrous when oneconsiders the extent of broadcastingto -day.

Then, of course, we had the deplor-able situation about experimentallicences. The writer of this editorialwas a member of a small deputation to

- CONTENTS .

- PageEditorial .. - :. - .. .. 743Our Impression of the Exhibition 744Jottings by the Way .. .. .. 747Those Touching Plates .. .. 749Combined Series - Parallel Tuning 750Random Technicalities .. .. 752How a Modern Valve is Made .. 754High -Tension Surp'y fr . ne A.C.

Mains for Small -Power Tr ns.mitters and Radio. Rec ivingSe _s 757

Watch your H.T. Battery .. .. 759Valve Notes .. .. .. .. 761A Simple Panel Switch .. .. 763Making the Most of Power Valves 764One Hundred Metres and Below .. 766The Progosed Wireless Telegraphy.

o nal Signalling BillA Handy H.T. and L.T. Battery

Connectcr 7701 A Dull Emitter Warning .. .. 771

Appiratus We Have Tested .. 772Correspondence .. .. .. 774

tInfornaatien Department .. .. 779

the Post Office to obtain an alleviationof. the harshness with which the PostOffice were refusing 'experimentallicences, the only licences at thattime..which enabled experimental

_ wireless work to be done. To -day, threequarMrs of, a million people are makingor using, home-made apparatus., There -is no logical reason why licences should_no! have been issued at that date.

743

The only result of this very importantconference with the Post Office wasthat a memorandum was issued after-wards remarking upon the great cour-tesy of the Post Office officials andtheir sympathetic attitude. Be itnoted, however, that this sympatheticattitude did not result in any- exten-tion 'of licences.

We then had .the summer of -5923,which nearly wrecked the wireless in-dustry, and which created more an-tipathy towards the Post Office thanthat department has ever experienced.Long delays and the appointment ofa committee (whose work was futile,and whose final recommendations weretotally ignored) were regarded withgrinning complacency by permanentofficials of the Post Office, whose cal-lousness in this matter will live longin the memory of every experimenterwho wanted a licence and every ex-perimenter whp had a licence, but hadeven the smallest amount of publicspirit.

Fortunately for experimenters,powerful manufacturing interests, anda Post Office visit to the U.S.A.,obtained far them what the RadioSociety had vainly pleaded for.

This recent history shows what atti-tude the Post Office has taken in thepast, and also it shows how absolutelyunnecessary the restrictions at the timewere. The same niggardly spirit ofthe Post Office is as manifest to -dayRS it was in 1922 and /923.

Let us look at some -of the statementsof Post Office officials in the past, andwe will see how charmingly reason-able they are before meetings of theRadio Society. 'At the second AnnualConference of Wireless Societies, 'in142z, a Post Office official regarded

. with horror the idea of membership ofa Radio Society ,being necessary before

(Continued on page 762.1


Wireless Weekly

A contrast in valves which may be seen at the Exhibition, the large one'being a ten kw. water-cooled transmitting valve.

THE first impression onentering this year's Wire-less Exhibition at the

Albert Hall is one of the sanityand commonsense of the wholeaffair. In previous shows thestands have often alternated be-tween the sublime and the ridicu-lous-on the one hand we havehad monuments of cabinet workof the one or two hundredguinea varieties, watched overby immaculately dressed youngmen who stand out gracefullyagainst a background of velvetand luxury, while on the nextstand one could see mountains ofcondensers, dials, knobs, andwhat not. This year there isnone of this annoying dispropor-tion. All the stands are of thesame size, and the scheme ofdecoration chaste and effective ;the whole industry seems to have" come down to earth," and nowcaters for the man who is reallyinterested and who does notmind spending a few pounds solong as he gets good value.

The organisers of the Exhibi-tion are certainly to be con-gratulated upon the artistic lay-

out, although the disposition ofthe stands in circles makes itdifficult to tour the Exhibition asa whole and not miss sectionsof it.

The Exhibits

The exhibits themselves can,of course, be divided into twon -lain headings of complete setsand components. In the generaldesign of sets there seems to beconsiderable improvement in thelast- twelve months, and it isgratifying to see how some ofthe larger firms have realisedthat it is not beneath their dig-nity to make a good set at areasonable price. Armstrongsupersonic heterodyne receiversare beginning to make theirappearance, and we particularlynoticed those of the WesternElectric Co. and General Elec-tric Co. respectively. TheWestern Electric instrument isvery compact, and containsseven valves (all " peanuts "),used successively as first detec-tor, oscillator valve, three stagesof intermediate frequency,second detector valve, and one

744

October 8, 1924

Our Impression

of the

Exhibition*0,0%0' PG^,O,Gi.0...0<7,0--a-g.

stage of transformer -couplednote -magnification. The set isexceedingly compact, and to ob-tain this compactness it hasbeen necessary to shield everystage with a metallic casing.

The General Electric Co.'ssupersonic heterodyne is rathermore conventional in appearance, -being made up in a large cabinetwith all the valves projecting in_front. The British Thomson -Houston Co. also have an instru-ment which we believe works onthe super -heterodyne principle.

Among the " straight cir-cuit " sets an interesting in-strument is exhibited by Burn -dept. In this the aim of thedesigner is to give a set whichis exceedingly simple to workfor the manup the art, but is so adjustablethat later, when he learns moreabout it, the necessary flexi-bility is made available. There

A compact 5 -valve receiver byMetropolitan -Vickers, Ltd.


October 8, 194

* * *A few notes on thisyear's Wireless Show

are two stages of tuned high -frequency, stability being ob-tained by stabilisers working ona novel principle. Rangeblocks with fixed loose couplingbetween the aerial and the closedcircuit are provided, and a switchenables both high -frequencystages to be cut out, so that alltuning can be conducted on onedial, when the set is nearenough to a broadcasting stationfor good reception to be obtainedwithout high -frequency stages.The more experienced listenercan substitute for the rangeblocks a three -coil holder, thusgetting the benefit of variablecoupling and reaction as desired.Stages of low -frequency amplifi-cation are, of course, provided.

The Sterling people have agood range of receivers, includ-ing reflex sets using small frameaerials. Among other reflexesshown are the Marconiphones,the Ediswan TwoVee, certainsets by Metropolitan -Vickers.

Loud Speakers

Loud speakers of all kinds arean outstanding feature of theshow. The large Marconi loudspeakers, the invention of Capt.

The Pri max Loud -Speaker.

Wireless Weekly

A handsome frame aerial receiver, ornamented with Japanese lacquering,on the Sterling stand.

Round (used to broadcast to thepublic in the Hall) are remark-ably faithful in their reproduc-tion, and should do much goodin removing from the minds ofthe general public the impressionthat loud -speaker reproduction isa metallic -sounding and " trum-pety " affair. So far as loudspeakers for the home are con-cerned, these exist in greatvariety, but as they all have tobe taken " on trust " (therebeing no demonstration of anyone of them), the public is quiteunable to make comparisons ofanything but external appear-ances. So far as the hornvarieties are concerned, prac-tically all the manufacturers areadopting about the same shape,the horns being decorated in allkinds of colours, and some withthe most bizarre patterns.Because it does not comply withthe general uniformity of design,the Sterling Primax loud speakerstands out from the others in

745

great contrast. This loudspeaker has a pleated diaphragmover a foot in diameter whichdistributes the sound without anyhorn. One of the most beautifulexhibits this year, and certainlythe one which has attracted themost attention, is a gracefulbronze figure holding aloft aPrimax loud speaker, the dia-phragm of which has beenfinished in a bronze colour tomatch the statue. It is illus-trated in one of our pictures.

Great interest is being shownin the various unit systems,although there are no specialnovelties this year. The PolarBlock method, the CosmosRadiobrix, and one or twoothers attract most appreciativeaudiences whenever demonstra-tions are given. The leadingvalve manufacturers are, ofcourse, showing their products.In the smaller components Dubi-lier have several interesting newlines, with new mouldings for


Wireless Weeklytheir fixed condensers, of muchbetter finish than formerly. Theclips, too, have improved; aremade removable so that a gridleak can be placed across thefixed condenser, or in series withit, for tuned anode work. Thisfirm are also making a square -law condenser and other specialvariable condenser, in which inchanging from the series to theparallel adjustment a good over-lap is possible.

The Radio CommunicationCompany have a number of use-ful devices for the home con-structor, including their specialresistance -capacity coupling unit,which has been very carefullythought out, and a new dualfilament resistance. Burndeptare showing their new anti-microphonic valve sockets, whichquite effectively remove themicrophonic troubles inseparablefrom most dull emitter valves.Peto-Scott are showing a goodline of parts and complete sets.Their Pilot panels are alsoattracting attention, these beingcut, finished, and engraved for avery moderate figure. TheBowyer -Lowe Company areshowing their well-known squarelaw condensers, both single anddouble, and their guaranteedpanels, which are also obtain-able cut, polished and engravedfor any Radio Press Set. Ready -cut and polished panels are alsobeing exhibited by the BritishEbonite Company.

Radio Instruments are, of

course, making a big show oftheir new intervalve trans-former, a large model being ex-hibited to show the method ofwinding, for which a very lowself capacity is claimed. On theMarconi Stand the new Marconi -phone Transformer is well inevidence.

The high -power transmittingvalve exhibited by the WesternElectric Company attracted aconsiderable amount of attentionfrom the mare advanced ama-teur. This is a water-cooledvalve and considering the powerit can handle (up to io kilo-watts) is remarkably compact.Another high -power water-cooledvalve is shown by the Marconi-Osram people, while Mullardsare also showing high-poweredvalves of their well-known de-signs. The Cossor firm aremaking a big feature of the" Wuncell." Although thereare few outstanding novelties inaccumulators, the well-knownmakers of storage batteries areshowing their regular lines, andjudging by the crowds roundtheir stalls, the public are anxiousto learn as much as possibleabout these devices. Now that thepower valve is coming into moregeneral use, the problem of high-tension supply is becoming acute,and with multi -stage amplifiersthe drain on an ordinary high-tension battery of the dry -celltype is very serious. High-ten-sion accumulators are now ob-tainable at the quite reasonable

October 8, 1924

price_ of one shilling per volt,and whilst this, of course, seemsa high first cost (much higherthan dry cells), the maintenancecost is extremely low. The manwho is now in a habit of pur-chasing a sixty -volt dry batteryevery few months should cer-tainly consider whether it isworth his while to pay three orfour pounds for one of the equi-valent voltage accumulators. Ifyou consider it on a two -years'basis, it will be found in manycases that the high-tension accu-mulator is cheaper.

Accumulators of low ampere -hour capacity are also beingshown for dull emitters. Weare glad to see this, as manypeople have been grossly over-loading dry cells fore filamentlighting, and expectinc, to getfrom them far more than theycan possibly give. A large num-ber of very useful components,well made, are exhibited byMessrs. McMichael, while themultitudinous uses of " Clix "are being publicly demonstrated.

It is certainly gratifying tonote that the industry has settleddown on sound lines. Extrava-gant claims, freak sets, and use-less components have dis-appeared. The public is nolonger deluded into buyingshoddy sets and components, andgood material is now obtainableat quite reasonable prices. Cer-tainly this year's show augurswell for the future of the greatnew industry. -

A general view of the Exhibition. The Radio Press stand may be seen to the left of the centre, at the back.746


October 8, 1924

Snaggsby This TimeIT was Snaggsby, I think, who

was the first to suggest thatthe Little Puddleton wireless

club really ought to obtain atransmitting licence, so that itsactivities might be broadcast toan eagerly -waiting world, notonly in cold print, but alsothrough the more romanticmedium, the ether. He came tosee me about it a day or twobefore he raised the question inthe club -house. As he sat andsmoked, he suddenly said, " Ihave been thinking? " " Thatis not an original remark,Snaggsby !" I replied, "Poddlebyreported recently that exactlythe same phenomenon hadoccurred to him, and certainlythe results were little short ofdisastrous. If I remember arightit resulted in his spoiling twosuits of clothes, a carpet, and hiswife's temper. I therefore urgeyou to bear this terrible examplein mind and, if necessary, tostifle at birth the results of yourmental activity." Snaggsbywaved his hand, blew a cloud ofsmoke, got up, sat down again,made some more smoke, clearedhis throat, opened his mouth andshut it again. " Come on," Isaid, " it is quite obvious thatyou, are oscillating under the im-pact of brain waves. Is therenot an old song which tells of alady upon whom some terribledisaster had fallen? Did not herold nurse say, she must weepor she will die? ' I do not wantyou to weep if you can help it,for this is a new hearth rug ;and I would rather that you didnot die here, since the maids havestrong objections to removingcorpses in the morning. Speech,however, is obviously necessaryor something untoward willhappen. Out with it, my friend,and let me know the worst."

The Great IdeaThus encouraged, Snaggsby

became more communicative." We must have a transmittinglicence," he said. " We," Iroared, " we? You speak foryourself, my friend. You oughtto have one, I know, for thehowls that you produce fre-quently make my hair stand onend and are heard as far away asBilgewater Magna. But I havea perfectly clean sheet. I canstand up before the world andsay with my hand upon my heart'that I oscillate not, neither do Ihowl." " I am not talking aboutyou or me, you ass," saidSnaggsby, with some heat, " Imean the club. Here we are,quite the most up-to-date andgo-ahead club in the country, andall we do is to receive otherpeople's transmissions instead ofsending out things ourselves.Now I don't believe there is amember of the club who knowsthe first thing about transmitting.

A Terrible State" You must admit that this is a

terrible state of affairs amongstreally keen wireless people likeourselves." He went on to saythat of course none of us wishedto brag, but there was no doubtabout it that the Little PuddletonClub was by now the best knownin the world, and that on everyhand people were asking, " Whydon't those fellows do somethingto show us what they are madeof? " Only the other day he hadoverheard a conversation be-tween two residents in BilgewaterMagna, one of whom was tellingthe other (who cordially agreed)that he did not believe that thoseLittle Puddleton fellows reallyknew anything about wireless.They just sat at home listeningto broadcast programmes onready-made sets, or went to theclub and aired their ignorance for

747

Wireless Weekly

each other's benefit. This kindof thing, Snaggsby insisted, wasnot to be borne, and I was ratherinclined to agree with him, forthere is no more patriotic a LittlePuddletonian than myself.

The Club Hears the WorstAt the next meeting Snaggsby

stammered out his proposal to anelectrified meeting, whilst I, whowas seconder, made an eloquentlittle speech which put the wholecase in a nutshell. Members wereinclined to be a little doubtful atfirst, and there was a good dealof discussion, but in the end theresolution was carried that atransmitting licence should beapplied for instanter. Theauthorities, I am sorry to say,showed a lamentable lack ofappreciation of the services tothe great science of wirelessrendered in the past by the club.

Red TapeInstead of sending us by return

of post, as we had expected, fullpermission to transmit as freelyas we liked and their officialblessing, they merely wrote acold-, formal letter, enclosing ahorrible document in which allkinds of questions had to beanswered. This was duly com-pleted and despatched. Then wesat down waiting with as muchpatience as we could summon forour permit. The first one thatcame was far from satisfactory,for it merely gave us leave touse an artificial aerial. This, asGeneral Blood Thunderby re-marked, was nothing more orless than an insult. He volun-teered to go at once to Londonas the club representative andget matters put right withoutdelay. We despatched theGeneral upon his mission withhearts full of hope. By threeo'clock that afternoon we re-ceived an official telegram: " We


Wireless WeeKlysurrender unconditionally -;for heaven's sake remove yourwarrior ." The General wasrecalled by wire and congratu-lated heartily, and the licenceturned up by the following morn-ing's post. I won't tell you thefull story of his onslaught, as re-counted by himself, but when Isay that he appeared to haveopened his mouth and let himselfgo, you will understand that theofficials must have had a prettyhectic time.

We BeginEverything being now in order

it remained only to erect ourtransmitter. It was decided tobegin in quite a small way, foras Bumpleby Brown said, " Itnever does to rush things, andwe don't want to be accused ofswanking." Everybody contri-buted his mite to the club trans-mitting set. As I possess no gearof any kind suitable for the im-portant parts of the apparatus,I could do no better than someterminals and a couple of rheo-stats, all of which were claimedin the most barefaced way byvarious members of the club astheir own property. I did, how-ever, offer, and the offer wasaccepted with alacrity, to proceedto Bush House to consult Mr.G. P. Bendall, of the InquiryDepartment. I presented myselfin his sanctum armed with anample supply of half-crowns.These I placed upon the table infront of me, and he, with one eyeupon a stop watch, removed oneof them from my side of the tableto his with a kind of croupier'srake at frequent intervals. Heis really a very charming fellow,but as I had lots of questions toask, the interview was an expen-sive one for the club, particularlyas he suddenly went off into adiscussion on tuning coils, plyinghis rake with great skill at theend of each ten minutes. At theend of our interesting conversa-tion I was full of informationabout methods of winding, butremembered when I was outsidethe door that I had hardly beenable to ask a single question ontransmission, and that there wasnot a half-crown left. On myreturn to the club I was receivedrather coldly, even though Ioffered to give the finest lecturethat they had ever heard on coilwinding. It was seriously pro-posed by Poddleby that the half-

crowns expended should bedebited to my account. I amafraid that Mr. Bendall is in forrather a rough time, for nextweek we are sending up GeneralBlood Thunderby to consult himprovided with only two half-crowns. If ht does not tell Mr.Bendall a few things about tun-ing coils I shall be surprised.

Renewed EffortsFeeling that my reputation had

somewhat suffered amongst themembers of the club by my visitto Town, I then proposed ascheme, which was agreed to atonce. " Mr. Hercy Parris," Isaid, airily, " is a friend ofmine." This is quite true; infact, I frequently call him Hercywhen I think that he is farenough away not to be able tohear. I will write to my friend,Mr. Hercy Parris, who has juststarted a transmitting station ofhis own at Wimbledon. I willpropose myself for a week -endwith him, and I am quite surethat he will be delighted to haveme. During my stay with him

October 8, 1924

I shall pick up lots and lots oftips, and if I am lucky I shall beable to borrow some very usefulgadgets." I wrote, therefore,debiting the club the three -half-pence for the stamp, a n danxiously awaited the reply.When it came I must say I wasrather disappointed, for he saidsimply, on a postcard, mark you," Afraid that during next tenweek -ends shall be engaged indesigning circuits for the follow-ing months. May be able to putyou up next summer if I can finda vacant week -end. Am insuringall my wireless stock againstloss." This was a rebuff, as youwill admit, but I am not yetdefeated. There are othcrmembers of the Staff who knowsomething of transmission andhave suitable gadgets. PerhapsI shall have better luck withthem. Meantime, the club is stillgetting ready to transmit, andyou may expect something ratherout of the ordinary when itspreparations are completed.

WIRELESS WAYFARER.

A close up of the interior of a Marconiphone four valve receiverembodying the new Marconi transformer.

748


October 8, 1924

Those Touching Plates

FVERYONE, I suppose, hashad some experience of thetroubles caused when- the

moving plates of a variable con-denser touch the fixed at somepoint when they are rotated.This can be the most annoyingof all faults when, as has justhappened to me, it occurs in acondenser mounted in a verycomplicated set which cannot beremoved for repairs without un-soldering a good many wires.

Self OscillationTouching plates may give rise

to a good deal of bother withoutthe cause being suspected. I hadan example of this the other daywith a set containing two tuned -anode -coupled H.F. stages. Itwas'not working well, and therewas a tendency to fall into self -oscillation. Both the anode tun-ing condensers appeared to beup to the mark, for no clicks orother noises were heard wheneither was rotated. After a longand fruitless search for thetrouble I happened to remove thesecond anode coil and to rotateits condenser whilst it was notthere. Terrific noises indicatedthat at one point the plates weretouching.

How a condenser of goodquality, which works perfectly

IHAVE just had a rather curi-ous occurrence in a set fittedwith a resistance -coupled note

magnifier. This system ofcoup-ling is becoming more and morepopular for note -magnifiers,owing to its freedom from theusual distortion due to inter-action between circuits. As agood many readers probably usesets fitted with it, this type ofcoupling the occurrence in thisparticular set may be interestingto. them. When first made up itfunctioned very- well indeed,giving good signal strength withan entire absence of distortion.

Reduction in Signal Strength

At the end of about a month thestrength had fallen off consider-ably, the low frequency valves

before being mounted in the set,can suddenly develop this fault Ido not know, but even the best ofthem are liable to do so at times.The job of setting matters rightmay be a perfectly easy one, orit may prove to be a long and ex-asperating business. The waynot to set about it is to find thepoint at which touching is takingplace and then to give one ormore of the moving plates a bendupwards or downwards with theintention of correcting it. To doso merely means that if you curethem of touching at one pointyou will make them do so atanother.

The Moving Plates

See first of all whether themoving plates are firmly lockedtogether on the spindle. One ofthe commonest causes of misbe-haviour on their part is that thenuts securing them have workedloose, allowing them to wobble alittle. These nuts can usually betightened with a spanner withoutit being necessary to remove thespindle from the body of the con-denser. If the moving plates arenot loose, turn your attention tothe fixed ones. These areusually secured by three longbolts, which also form the frame

E

Wireless Weeklyof the condenser by supportingthe top and bottom pieces.

Should it happen that thesebolts have been tightened up un-evenly, it will be found that theframe has been pulled askew.Owing to the strain the bushes attop and bottom are no longer.properly aligned, and the spindlewill not be quite at right anglesto the fixed plates. Hence themoving plates which it carrieswill be cocked up a little at oneend and will droop slightly at theother. The remedy in this caseis to work the nuts upon the sup-porting bolts one against theother until the moving plitesmesh truly with the fixed.

The Fixed PlatesShould the moving plates be

quite level, but either too highor too low, the fixed platesshould be raised or dropped alittle by means of the nuts onthe long bolts. This hint ap-plies to most standard con-densers ; some, however, have anadjustment for regulating theheight of the moving plates,which makes matters mucheasier.

When it is found that " touch-.ing " is caused by some of theplates having become bent, it isnot, as a rule, worth while toattempt to straighten them.Plates can be bought so cheaplythat by far the best way is topurchase a new set.

N. O. P.

Anode Resistances

showed occasional signs of oscil-lation and the original purity ofreception was spoilt. At firstsight the case was rather abaffling one, for everythingappeared to be in order, bothwith the wiring and with the com-ponents. Tests with a milliam-meter showed that of the tworesistances, each of which wasmarked 6o,000 ohms, one had avalue of rather under io,000,whilst the other was about15,000. They were not of par-ticularly good quality, and whathad happened Was that they werenot able to stand up for long tothe load of the plate circuits.

749

Warning

Both of them had given way,with the result that the wholeequilibrium of the circuits wasupset. When you buy anode re-sistances, either fixed or variable,it pays always to get those thatare of well-known and reliablemake. Poor ones may fall offconsiderably when they are inuse, and in some cases theirvalue may vary from day to daywith changing atmospheric con-ditions. With these things theset can never be relied upon, forsignal strength will not be con-stant.

M. A. Y.


Wireless WeeKlyE 111 El EISEN 111 IN II le II

a

Fig.1.-A simple aerial tuning circuitusing constant aerial tuning.

FURTHER developmentcan be made of Mr. J.Scott-Taggart's "Constant

Aerial Tuning " device, in which(Fig. i) by the use of a smallfixed series aerial condenser agreat deal of that uncertainty iseliminated which usually attendsthe introduction of a new receiveron to an aerial of undeterminedcharacter. The effect of thissmall series condenser is tominimise the active aerial -to -earth capacity, which wouldotherwise load up the grid -tun-

a ing-circuit to an undeterminedextent, and may play havoc withthe tuning range as. determinedby the designer or constructor ofthe particular set on his ownaerial.

Series -Parallel TuningThis development, which has

a useful application in certaincases, consists in making variableBOTH the small series condenserin the aerial and also a smallparallel tuning condenserarranged as usual across thetuning inductance. With only asmall portion of a low -minimumvariable series condenser in use,the effective capacity of the aerialis reduced to such a low figurethat quite a small parallel tuningcondenser will cover a consider-able wavelength range, if thetuning inductance has small dis-

Butributed capacity ; at the sametime the total tuning capacitycan be kept low. In crystalreception, as is shown by actualmeasurement of resulting signal -strength, the use of a small seriescondenser with a proportionatelylarger inductance (an arrange-ment which is historically derivedfrom a compromise necessitatedby the excessive size of ships'

EIE11 INNEN

a 1811E111111ENIIINOctober 8, 1924

1110021111111111111

Combined Series -ParallelAerial Tuning

By A. D. COWPER, M.Sc., Staff Editor.Ea"

aerials when short-wave receptionis in question). produces a lossof signal -strength which corre-sponds closely in magnitude tothat produced by a series resist-ance deliberately introduced intothe aerial, of a value equal to the" reactance " (effective H.F. re-sistance) of that same smallcondenser to an oscillatingcurrent of the same frequency,when inserted in an untunedcircuit. But in valve reception itis an entirely different story : thesmall condenser acts as anefficient capacity coupling, and atthe same time minimises both theeffects of excessive capacity andof resistance -damping in theaerial. A bigger voltage build-up in the local oscillating circuit(with its comparatively less im-portant damped aerial -branch) is

E

Fig. 2.-A circuit which will tune allinductance. The variometer may

condenser forthus possible ; and reaction canbe applied in a much more refinedmanner. A marked increase inselectivity necessarily follows,though, of course, it does notbecome in this respect comparablewith the semi-aperiodic types ofcoupling, or to proper loose -coupling in a two -circuit tuner.

Tuning InductanceIf a low -resistance tuning in-

ductance is used in the form of,e.g., a basket -coil on a I in.former of No. 20 S.W.G. d.c.c.wire, say, 4o to 75 turns (accord-

ing to the aerial and range ofwavelengths in question), andtuning -condensers of really lowminimum capacity, as indicatedin Fig. 3, even a three -plate con-denser" will give enough range tobring in two adjacent B.B.C.stations at a signal -strength andwith a delicacy of tuning whichwill be a revelation to thoseaccustomed to the usual high -resistance tuning inductanceswith large parallel tuning con-denser, and with the whole of theaerial -load in addition. Themodest reaction -demands willalso surprise many experi-menters; a No. 5o coil willgenerally suffice over the usualbroadcast range, and often theordinary two -coil holder will notallow sufficiently loose couplingof the two coils to avoid oscilla-

short-wave B.B.C. stations on onebe loaded with a 0.0003 ALF fixedhigher ranges.tion with a valve of good filamentemission and high amplification -factor. The loose coupling herealso reduces that most annoyingfeature of the two -coil tuningdevice, the continual change ofthe aerial tuning with varyingreaction -coupling.

Range CoveredIn order to cover a very large

range efficiently with a singlehome-made coil of low H.F. re-sistance, such as indicated here,one can adopt the highly -developed tuning arrangement111111 EEEMIII IN L

750


October 8, 19240Those readers who are familiar with the advantagesof constant aerial tuning will find in the following

article much to interest and instruct them.

shown in Fig. 2. By using arather larger (but low minimum)variable series condenser in theaerial, and a rather largerparallel tuning condenser acrossthe inductance, with a three -plate(or so-called " vernier ") con-denser in parallel with this, wehave the possibility of reducingthe total effective tuning capaci-ties to a low figure for theshortest waves (e.g., far Brusselsand Sheffield), whilst using afairly large inductance and there-by obtaining good signal -strength ; and for the higherstations, such as Aberdeen andone or two of the Germanstations, we can use a largerproportion of our aerial capacity(by putting the series condenserat its maximum), together with areasonable parallel capacity,under conditions where these areless harmful to effective signal -strength. At the same time, withthe small three -plate condenser,equipped with a long handle, wehave fine tuning available at alltimes. Exceedingly smooth re-action is obtained over a widerange of wavelengths by meansof the electrostatic reaction -coupling produced by a plate-variometer, not deliberately mag-netically coupled with the A.T.I.in most cases, of about 5o turnseach on stator and rotor, andpreferably of the internally -wound spherical type.

Actual ResultsActual trial with a similar tun-

ing device on a country aerial ofan unassuming type showed that,after dark on a fairly favourablenight, it was an easy matter togo the rounds of most, if notevery, main B.B.C. stations onthe single valve, followed up byBrussels, Petit Parisien, Ecole,Berlin, Breslau, Frankfort, Ham-burg (with a ghost of Madrid atthe edge of his wave), etc., witha few of the British relay stationsthrown in for good measure.

The improvement of signal -1 II 11Maiimaii

strength with these tuningarrangements over that attain-able with the customary types oflow efficiency is considerablymore than that given by existingmethods of high -frequency ampli-fication.

a a

The P. 0. andAmateur

TransmittersWe reproduce below correspon-dence which has passed betweenMr. Percy W. Harris and the PostOffice. Our comments upon theattitude of the Post Office aregiven in our Editorial.

a aExperimental Transmitting

Licence 2MQ.SIR,-With reference to the

above, I should esteem it afavour if you would kindly grantme a permit to communicatewith experimental wireless sta-tions outside this country and onwavelengths shorter than 15ometres, together with an increaseof power when required to notmore than 25 watts.

The reason for this applicationis that I am at present engagedon some highly important workfor greatly improving the rangeof transmission with very lowpowers, and which will, inciden-tally, have a considerable bearingon the secrecy of communication.

As the experiments will prob-ably form the subject of LettersPatent in the near future, I donot care to indicate in detailwhat these are, but trust that mystanding as an experimenter willprove my bona fides.-I remain,your obedient servant,

PERCY W. HARRIS.

Wireless Telegraphy.SIR,-With reference to your

letter of September 12, I am11111&751

Wireless Weetilya M 1/11

Fig. 3.-A combined series -parallelaerial tuning -condenser circuit.

directed by the Postmaster -General to say that the use ofpower over io watts and ofwavelengths below 15o metrescan only be allowed in caseswhere special justification isshown, and with the consent ofthe Government Departmentsother than the Post Office whichare interested in wireless com-munication.

If, therefore, you will furnishfull details of your proposedexperiments, stating what wave-lengths below 15o metres yourequire, and indicating clearlywhy you consider the use of suchwaves and higher power essen-tial, the matter shall receiveattention. Any informationwhich you may furnish on thesubject will be treated as confi-dential.

As regards your application forauthority to communicate withforeign stations, I am to saythat permits granted for the useof wireless sending apparatus arefor experiments in wireless tele-graphy between stations in GreatBritain and/or Northern Ireland,although this was not expresslystated in the earlier permitsissued. Communication withanother country is not consideredto be necessary under normalconditions, but the Postmaster -General is willing to considerany application for further facili-ties on receipt of detailed parti-culars of any experiments withstations abroad and evidence ofan arrangement for co-operationby a foreign or colonial experi-mental station or stations.-Iam, sir, your obedient servant,

J. W. WISSENDEW,for the Secretary.

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Wireless Weekly

me.

Random Technicalities.By PERCY W. HARRIS, Assistant Editor.

Some Notes of interest to the Home Constructor and Experimenter.

NW7 HEN listening to amateurtransmitters after broad-casting hours, one fre-

quently hears the statement madethat the speaker is getting i or ior whatever the fraction may be,of an ampere in the aerial, as ifthis was an indication of power.Furthermore, it is quite evidentthat many transmitters are underthe impression that amperes inthe aerial are all that matters,and that any increase in aerialcurrent is bound to mean an in-crease in radiation. This fallacyis fostered to a certain extent bythe often incorrect reference to ahot-wire ammeter in the aerialcircuit, as a " radiation meter."

* * *

In a transmitting aerial ourgreat object is to " get the juiceaway," not merely to obtain ahigh current in the aerial wire.It is quite possible to have twoaerials, in both of which anampere of high -frequency currentis registered, one radiating excel-lently to long distances and theother barely getting a mile ortwo. We should therefore alwaysaim at maximum radiation ratherthan maximum aerial amperes.

* * *

In a transmitting aerial wehave two important factors to beconsidered-ohmic resistance andwhat is termed the radiationresistance. Radiation resistanceis the convenient, if somewhatloose, term to indicate, in figuresto which we are accustomed, thepower we can get away. If westate the radiation resistance inso many ohms, this means thatthe same amount of power isradiated as will be absorbed by aplain resistance of that numberof ohms.

* *

Now; we want ohmic resist-ance, which is of no value to us,to be as low as possible and ourradiation resistance to be as highas possible. If the total high -frequency resistance is, say, io

ohms, we want the largestpossible percentage of this to betaken up by the radiation resist-ance. It is thus easy to see thattwo aerials both, say, having ahigh -frequency resistance of thesame figure, one may radiatemuch better than the other.

* *

It will now be seen how mis-leading it is to rive the aerialamperes only. Let us supposethat by some alteration of shapeor general arrangement we areable to increase our radiationconsiderably. We will assumefor the moment that our previoustotal high -frequency resistancewas zo ohms, and that thechange we have made has in-creased the radiation resistanceby io ohms. Our total resistancewill now be 3o ohms and aerialcurrent will actually drop ; thiswill be seen from a few simplefigures. If we have, say, towatts of power dissipating someway or other in the aerial system,and the total resistance is 20

October 8, 1924

ohms, then, according to thefortnulw 12R, the current will beapproximately .7 ampere. Let usnow add to ohms to the radiationresistance, making a total resist-ance of 3o ohms, the currentnecessary to dissipate io wattswill be approximately .57 ampere.

*

And then there is a matter ofcounterpoising; I am not con-cerned at the moment withwhether a counterpoise is a betterarrangement than a direct earth.I merely take this opportunity topoint out that erecting a counter-poise, say, io feet above the earthreduces the effective height of theaerial by that much, and froman increase in capacity can easilyincrease the aerial amperes with-out any improvement in radiation.Alternately, a man may be dis-appointed after erecting a coun-terpoise to find that his aerialamperes do not go up, whereashe actually may be radiating farmore than previously.

A Western Electric Super Heterodyne Receiver employing sevenWeco valves.

752


October 8, 1924

Many examples of what can be done withat the Exhibition.

Turning to receiving affairs, Irecently came across a casewhich is well worth mentioningin these columns, as there maybe others suffering in the sameway. A friend of mine movedfrom one locality to another, andwas greatly disappointed at thevery poor signals he then ob-tained on his crystal set, com-pared with those he had pre-viously received in the otherdistrict. Incidentally, the distance'from the broadcasting stationwas not appreciably greater, andthe new aerial was somewhathigher and generally lookedbetter than the old one. I wentdown to the house to find out

Can a growing tree be used asAerial ?

Some experiments have beencarried out in which a tree wasused as an aerial. The methodconsisted in driving a nail intothe tree some 8 or to feet abovethe ground and connecting thenail to the aerial terminal of thereceiving set in the usual way.An earth connection was ob-tained either by driving a steelpeg into the moist soil or by theuse of earth mats. Valve receiv-ing sets were used, and the re-sults obtained varied consider-ably, it being suggested that theconnecting wire between theaerial terminal and the nail inthe tree probably acted as afairly effective aerial. There isno doubt scope for some interest-ing summer -time experiments inthis connection.

Clix plugs may be seen

what was the matter, and couldfind nothing wrong with theaerial, the earth, or the receivingset. By the process of elimina-tion I came down to the head -'phones, which, on being takenback to my own house to berepaired, proved to be very in-sensitive, although when pur-chased a year or more ago, theywere practically as good as anyon the market. Of course, sub-stitution of new 'phones puteverything right.

* *

Now, when using a crystal set,'telephones do not lose theirsensitivity in the way which is

Wireless Weeklypossible with a valve set, for inthe case of the latter, if the tele-phones are connected in thecircuit the wrong way round, thesteady anode current may tend tode -magnetise the 'phones and toreduce their sensitivity that way.In a crystal set, of course, thereis no steady current flowing, andit does not matter which wayround they are connected. Whathad actually happened in thiscase was that the telephones hadbeen dropped on the floor anumber of times, and each of thejars had knocked a little of themagnetism out of the magnet.A sharp bang or jar is very badindeed for telephones, and it isalways wise to have a hookhandy on which the 'phones canbe hung immediately after use.If they are left lying on the tableit is as like as not that a memberof the family will occasionallycatch his or her foot in the cords,and drag thetn'to the ground.

Congratulations to the DubilierCompany for at last bringing outa condenser with clips so thatthe grid leak can be placed acrossthe condenser or in a positionnecessary for a tuned anodecircuit. This little arrangementis long overdue, and I hope willbe adopted by all other manu-facturers as soon as possible.

Some Simple Questions Answered

What methods of winding areadopted to reduce the internalcapacity of multi -layer Coils ?

When winding a multi -layercoil the points to be borne inmind are these :-Firstly, theturns must be separated fromone another electrically by only asmall difference of potential.The first object is achieved byadopting that method of windingwhich produces a cellular forma-tion such as the honeycomb coil,or by spacing the layers from oneanother by either artificial sepa-rators, or a special spacing turnof wire. An example of thislatter type of coil is the lattice.Electrical differences of potential

753

between adjacent turns will bereduced by so winding the coilthat turns which lie fairly closeto each other are onlyseparated in the electrical sense,by a small number of convolu-tions. Thus, turn i may lieclose to turn 3, but turn randturn 20 must be well separated.Can accumulators be used to

supply the H.T. current forvalves ?Yes, batteries containing a

large number of small accumu-lator cells are used to a limitedextent. They are somewhat ex-pensive, however, and require agood deal of attention to keepthem in good order.


Wireless WeeklyIIM11111111111111011111111

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October 8; 1924

in ta ni n

Pump tables with eddy current heating equipment for fine filament valves.

-

1T is an unusual thing in thisspecialised century to find afactory turning out so highly -

developed a product as themodern valve, which yet beginsits series of processes with theextraction of one of its rawmaterials from the crude ore.That, however, is what is doneat the M.O. Valve Company'sworks at Brook Green, Hammer-smith, and the first thing whichthe visitor is shown is the plantfor the preparation of puretungsten. The ore employed isan Australian one, which consistsin the main of a compound oftungsten and calcium, and asimple process of extraction withhydrochloric acid and ammonia,and finally re -precipitation withacid yields pure tungstic oxide.The requisite percentage of thoriais then added, after drying andgrinding to a fine powder, andthe mixed oxides are reduced tothe metallic state by heating inan atmosphere of hydrogen.

PowderThe result is

which presents

Filamentsa grey powdersomething of a

RI

problem since it must be reducedto a coherent metallic mass beforewire -drawing can begin, and the

zaao

How a . .

Modern Valve

is made . . .

obvious process of fusion is un-desirable.

The procedure adopted at theBrook Green works is thereforeof necessity somewhat elaborate,although to the spectator it seemswonderful how soon the appar-ently uncontrollable grey powderbecomes a stiff rod capable ofundergoing quite severe mechani-cal treatment. The first step iscompression in a hydraulic press,which produces a square barsomething like a foot in lengthand a quarter of an inch square,possessing a fair degree ofcohesion. This bar is nextgripped by its ends, and a veryheavy current is passed through

Ageing rack for receiving valves.n nioEs 754


October 8, 1924

a EMU E 111 le 0 E 0 E EEBEE 11 IS rs II El El GI 11 01 El 3

A brief sketch basedupon a visit to theM.O. Valve Co.'s

Works.

* * **,0,047,0047-0-0No%00%0*

it, thereby welding its particlestogether.

Drawing the FilamentThe solidified bar is then trans-

ferred to a series of smallfurnaces in which it is stronglyheated, and at the same timesubjected to the action of high-speed automatic hammers. Itssuccessive passages through thesefurnaces produce a gradualelongation, until finally the rodis sufficiently reduced to bepassed to the ordinary wire-drawing machinery, where re-peated journeys through diamonddies bring it down at last to thethinness of a hair.

The OreOf the more important

materials used in a valve thetungsten wire for the filamentalone is prepared from the ore

CI G M

Test table at

11111111MMIIIIIMthe Marconi Osram works.

A "sealing -in " machine forsmall valves.

at the M.O. works, and in thefactories carrying on the massproduction of the various broad-casting valves the complete life -history of a valve can be followedfrom the punching out of theelectrodes from sheet metal tothe exit of the finished valve tothe packing department.

Speciality WorkersEvery stage is carried out by

a worker who specialises in thatone operation, and the result is,naturally, very high speed andgreat uniformity in the finalproduct. Thus, one operatormay work the machine whichstamps out the anode from sheetmetal. The anode is then passeddown a little shute to the next

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Wireless Weekly

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Wireless Weeklyworker, who shapes it and elec-trically welds its edges together,-afterwards placing it in the shutewhich carries it to the nextoperation, namely, the weldingon of the support.

The GridSimilarly, the grid passes

through several hands, the shap-ing of the support, winding onof the wire, and spot-weldingtogether of the whole being doneby semi -automatic machinery,ensuring a high standard ofuniformity. The three elementsbeing complete, they are assem-bled upon a form of template andthe next operation is the insertionof the filament (again welded intoplace) and sealing of the wholeinto the " pinch " of the glassstem.

Revolving TablesAlmost all the operations in-

volving the treatment of the glassparts are done upon revolvingtables, where the necessary heat-ing is done by a series of gasflames of graduated temperature,the actual working of the glassbeing performed automatically inmost cases. This is true, inparticular, of the formation ofthe " pinch " in the stem of thevalve (the inner glass structure-which carries the electrodes) andthe sealing on of the bulb whenit has been drawn on over thecompleted assembly.

PumpingWhen the bulb has been sealed

on it is pierced at the top and theglass tube by which it is to bepumped is attached. The actualconstruction of the valve is thenfinished but for the attachmentof the cap, and it is next passedto the pumping table. In thecase of mass -production valvesthis is another revolving tableupon which the valve is placed,the lead- from the pump isattached, and the valve passesround slowly, the operation ofpumping being accompanied byheating by means of gas flamesto ensure the removal of" occluded " gases in the metalparts of the valve itself.

Sealing OffWhen the valve has completed

a revolution of the machine it isautomatically sealed off and isthen removed from the table andpassed to the next workers, whocement the cap in place andsolder the wires from the elec-trodes on to the appropriate pins.

The valve is then finished sofar as construction is concerned,

October 8, 1924

and it is placed upon the ageingtable, which is again of therevolving type. Here the filamentis lighted and a high -platevoltage is applied, and the valve

_gradually heats up. When acertain temperature is reached alittle piece of magnesium whichhad been attached to the anodeduring an earlier process isvolatilised and the bulb suddenlyfills with a brilliant blue glow,which persists for perhaps twentyor thirty seconds. Almost assuddenly as it appeared itvanishes again, leaving thefamiliar mirror on the glass, andhaving finally " cleaned up " thevacuum.

TestingUpon leaving the ageing table

the valve passes to the testbench, where it must conform todefinite standards of hardness,emission, etc., and then, assum-ing that it has passed the tests,it goes off to be labelled andboxed and finally is placed intostock.

A New Landmark

EVERY hour of the dayhundreds of people passingalong the Strand may be

seen gazing upward at the greatnew wireless aerial erected onthe roof of Bush House by Radio

Press, Ltd., for their head officeexperimental work. The aerialis of the cage type, high above

, ,/, every other buildingin London, completely free fromscreening effects.

Water-cooled valves in use at the high -power broadcasting station at Chelmsford (5XX).756


October 8, 1924

m

Wireless Weekly

62AS.5 CONTAINER

LEAP ELECTRODECONNECTED ro AZON/N/UNELECTRODE BY MEANS OFSMALL BOLT AND NUT

AZINNNYNNWCa-CT/WOE

Figs. 1 and 2.-Illustrating the jarand method of connecting theelectrodes.

High -Tension Supply

from A.C. Mains forSmall -Power Trans-

mitters and Radio

Receiving Sets

By E. A. POLLARD (5HQ).

ALORIUM

LEAP

ALUMINIUM

eonLAILNINNM ALUMINIUM

LEAD LEAD

ALUMINIUM ALUMNLUm ALUMINIUM

Fig. 3.-The complete rectifier withelectrodes in position.

HAVING been troubled withthe constant unreliability ofthe ordinary dry cell H.T.

battery, the writer decided to tryand obtain suitable current fromthe 220 -volt 50 -cycle A.C. mains.

Many methods of chemicalrectification were tried with vari-ous salts in solution as the elec-trolyte, but it was not until afterconsiderable experimenting thatsuccess was obtainable by usingchemical rectifiers. The rectifierabout to be described has been inuse some considerable time as ameans of supplying the anode cur-rent to a small power transmitter,but it was not until several weeksago that experiments were com-menced with a view to supplyingthe receiving set from the samesource. First attempts were un-successful, as the hum arisingfrom the A.C. 5o period supplyspoilt all chances of good recep-tion. Several modifications werethen introduced, and now recep-tion is as good, if not better, thanusing the ordinary dry cell H.T.battery. The experiments werecarried out on a three -valve re-ceiver, comprising one high fre-quency, one detector, and onelow -frequency valve.

Constructional DetailsThe construction of the recti-

fier is as follows, and it can bemade by any amateur withoutworkshop facilities. The totalcost of the apparatus need not ex-ceed fifteen to twenty shillings.

The parts required are :-One 4µF condenser, two 2,uF

condensers, and four Soo -ohmchokes.

These parts may be obtainedat a trifling cost from themany firms who specialise in ex -Government wireless apparatus.The remaining parts may be got

from any reliable chemist, andwill be dealt with in detail asrequired.

If the amateur has access to220 -volt mains, eight rectifiercells will be necessary, and in thecase of too to 15o volts A.C. fourcells will be required. The con-tainers for the cells may be smallboiling tubes, obtainable from anychemist, or the small glass jarsin which a well-known food com-modity is sold. These jars aresome 31 in. high by r/ in.diameter, and serve the purposeadmirably. The type of jar isshown in Fig. I. Next procuresome No. i6 -gauge aluminiumwire or sheet, care being taken to

77)A.C.

AIN

ALUM/PI/um.LEAD. --y

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as shown. The strips are nextplaced in the glass containers inthe order shown in Fig. 3. Thesestrips should not reach to thebottom of the jar, but should ter-minate some / in. from thebottom. This is to allow anysediment which may form to dropclear of the electrodes, so as notto interfere with the rectification.

The glass jars are then filled towithin ii of the top with the elec-trolyte. This electrolyte is com-posed of a saturated solution ofammonium molybdate (pure)chemical formula (NI -14)2M04.The writer, as mentioned be-fore, has tried various saltsin solution, such as borax,

ALI/MIN/UM. 4./11:

° r 111

CHOKES.

y2flP 2/IF sroH.T.

CHOKES.

Fig. 4.-The complete arrangement of rectifier and smoothing circuitis shown here.

have only the best quality (pure),and either some 6 -gauge leadwire or lead sheet, as the casemay be.

Chemical PurityCare should be exercised in the

purchase of the articles to seethat both the lead and aluminiumare of the chemically pure variety.

In the case of wire not beingobtainable, the aluminium sheetand lead sheet is cut into strips

in. wide by 4 in. long. Theseare bent to the shape shown inFig. 2, and one strip of lead isjoined to one strip of aluminium,

757

ammonium phosphate, both pureand commercial, but in no casewere the results as good as whenammonium molybdate was used.The saturated solution is got bydissolving 3 oz. of ammoniummolybdate in t 4 pints of water.Care should be exercised in usingonly distilled water in the pre-paration of this, as ordinary tapwater contains impurities whichmay possibly affect the efficiencyof the rectifier. The saturatedsolution is then poured into theglass containers to within / in.of the top. A good plan is tofill the remainder of the glass con-


Wireless WeeKlytainer with some high-grade in-sulating oil, or ordinary paraffinis a good substitute. After therectifier has been completed, asshown in Fig. 3, a lamp of some5o watts of a suitable voltage isconnected across the positive andnegative leads, the current

. switched on and the lamp allowedto burn for half -an -hour or so.This is necessary in order to formthe electrodes, much the same asaccumulator plates are formed.When the rectifier has beenformed the lamp is taken out ofcircuit and the rectifier is readyfor use. The direct current,which can now be drawn fromthe rectifier, is of a pulsatingnature, and is as yet unsuitablefor use with the receiver circuit.

The' Filter Circuit

The pulsations, which are of thefrequency of the A.C. supply, arenow passed through a filter orsmoothing circuit, whence leadsare taken to the receiving set.This filter or smoothing circuit isshown in Fig. 4. The positiveand negative leads from the recti-fier are led to a condenser of 4µF,thence from the condenserthrough two chokes of 500 ohmseach to another condenser of2p.F, then from this condenserthrough two more chokes of sooohms to a final condenser of2,1.4F capacity, from whence leadsare taken direct to the receiver.A variation of voltage to meet in-dividual needs may be got by theinsertion of a resistance or chokein the A.C. side of the rectifier.

Precautions Necessary

In all cases it will be seen thatit will be necessary to include alarge condenser of 0.002 µF inthe earth lead of the set, other-wise a direct short will take place.

In conclusion, the author placesthe ultimate success of this methodof obtaining H.T. from A.C.mains on the using of nothingbut pure raw materials, and toomuch stress cannot be given tothis point. The diagrams areself-explanatory, and the amateurshould have no difficulty what-ever in constructing a high -effici-ency rectifier.

Further, this rectifier will dealwith a current of some 3o milli -amps without excessive heating;thus making it quite suitable forlow power transmission.

October 8, 1924

1

Readers' Results withRadio Press Sets

SIR,-I have much pleasure in in-forming you of the success I haveobtained with the " Simplicity " set.Signal strength is most astounding,and am compelled to say it is allyou .(or rather more) claim it to be.When Cardiff is broadcasting, whichis zo miles distant, signals are heardat great strength through the wholeof the house when half -a -dozenpairs of headphones are attached tothe set. When Cardiff closes downall other stations are easily got atenormous strength on an outsidedouble aerial 38 ft. high. Itsconstruction is very easy, havinghad no difficulty whatever.-Yoursfaithfully,

Glamorganshire.EMLYN JAMES.

SIR,-As a regular reader of yourexcellent publications, I feel obligedto inform you that I have obtainedfirst-class results with Mr. Harris's" All -Concert " receiver. I hearChelmsford, Paris (Clichy), Konigs-.wusterhausen, Zurich, etc., clearand without distortion on two or;three headphones.

I followed entirely the instructionsin Mr. Harris's book, " TwelveTested Wireless Sets," and usedWeco valves, all other parts arefrom the Vereinigte Telefon andTelegrafenfabriks A.G., Czeija-Visel& Co. My aerial is 30 metreslong.-Yours faithfully,

FRITZ MENNY.

Vienna.

The Institute of Electrical Engineers, Victoria Embankment, S.W., wherethe meetings of the Radio Society of Great Britain are usually held.

758


October 8, 1924

.

Watch Your H.T. Battery

MUCH of the noisiness intheir sets of which somany amateurs complain

is caused by overloading thehigh-tension battery. The averagehigh-tension battery is made upof very small cells similar tothose used in pocket flash -lamprefills. It is doubtful whether anybattery whose cells are this sizeis capable of an output for anylength of time of more than threeor four milliamperes without be-coming partially polarised andtherefore uneven in its output.Five milliamperes should cer-tainly be the outside limit of thecurrent taken from it. Thosewho do not possess milliammetersdo not always realise what agreat strain they may be puttingupon their high-tension batteries.With ordinary bright emittervalves the plate current, if thefilament voltage is not excessive,will average about 1.5 milliam-peres per valve. This means thata three -valve set is the biggestthat can be worked satisfactorilyfrom a high-tension battery ofordinary size. A five -valve setusing ordinary valves may makea steady drain of as much as 7.5milliamperes, and if a powervalve is substituted for anordinary one, as a note magnifier,the current may rise to 12 or 1.5milliamperes, which is quitesufficient to make a small batterynoisy in a very short time.

V

reason. Its long, straight curve,low grid current, and small platefilament impedance enable it togive much purer amplificationthan the ordinary valve, andgreater volume of sound in the

Vdc

Wireless Weeklyother day an American UV 199,which was the first of the " .o6 "valves to be designed. With thefilament working at 3 volts thesteady plate current with the gridat zero was one milliampere.Raising the filament voltage to3.5 increased the plate current tonearly 2 milliamperes, and therewas a much bigger jump whenthe filament was put up to 4 volts.

L3

Fig. 2.- Showing position in which milliammeter should be usedwhen employing three separate H.T. tappings.

loud -speaker. But these valvesare specially designed to pass alarge plate current, and if oneis fitted to a set which is workedfrom a small H.T. battery, thegain in purity will be more thanoffset by the very great increasein parasitic noises.

Another cause of overloadingthe high-tension battery is to befound in using dull emitter valveswith their filaments working toobrightly. Some of these valvesare a little on the soft side, andif the filament voltage is at all

E

Fig. 1.-Indicating position of milliammeter whenH.T. voltage for all valves.

The power valve is becomingincreasingly popular for notemagnification, and with good

using a common

excessive their plate current mayrise to quite an amazing magni-tude. The writer was trying the

759

During these tests the platevoltage used was 40. Any in-crease in this voltage resulted inan increase of plate current.With 4 volts on the filament and8o on the plate the current in theanode circuit approached 7 milli-amperes. With British -made dullemitters of the same type theanode current was not quite soheavy as this, but at the sametime it increased to high valueswhen either the plate or filamentvoltage were made excessive.The very greatest care shouldtherefore be taken not to over-load the filaments of dullemitters, for quite apart from itseffect upon the life of the valve,to do so, may easily ruin thehigh-tension battery in a com-paratively short time.

The milliammeter is by far themost useful instrument that anywireless man may possess. It isunfortunately rather expensive,for it is a delicate instrumentand must be very accuratelymade. Still, they can be obtainedsometimes second-hand or fromshops which deal in Army surplusgoods. Fig. 1 shows the bestway of using the milliammeterwhen the same high-tensionvoltage is employed for all valves.It is wired permanently into thehigh-tension plus lead. It maybe mounted in the cabinet of the


Wireless Weeklyset or fixed to the table, the -leadattached to the high-tensionpositive wander plug being con-nected to its plus terminal. InFig. 2 is seen the position of themilliammeter in a set whose high-tension battery has three separatetappings in order to allow thecorrect anode potential to begiven to valves working on thehigh -frequency side, as rectifieror as note magnifier. Here theinstrument is placed at the nega-tive end of the high-tensionbattery, since the negative leadis common to all valves, nomatter what their plate potentialmay be. A simple way of doing

this, whether the milliammeter ismounted in the cabinet or fixedto the table, is to connect thenegative high-tension batterylead to its negative pole, and thewander -plug lead to its positive.

The milliammeter, mounted asshown in either diagram, recordsthe total current that is beingtaken from the high-tensionbattery, and one is thus able tokeep a careful watch to see thatoverloading does not take place.If it is desired to see what anyparticular valve is taking, all thatone has to do is to leave it glow-ing and to switch off the others.

R. W. H.

Ready -Made Sets

OST of the ready-madesets now available giveexcellent results, and are

easily operated even by be-ginners. There is, however, onething that I would like to see onthem, and that is the provision ofa means for supplying a highervoltage to the plates of notemagnifying valves than to therectifier. There are two ways in

which this can be done veryeasily. The first is to fit a secondhigh-tension plus terminalmarked " Extra H.T.+." Ifthe user likes he can then placethe wander plug corresponding tothe first H.T.+ terminal in the40- or 50 -volt socket of his bat-tery and the other in the socketwhich gives, the greatest possiblevoltage. If he does not want touse two H.T. leads, he cansimply short-circuit the terminals-a swinging hook connectionmight be provided for the pur-pose. The other method whichhas the advantage of extremesimplicity is this. Between

October 8, 1924

H.T.+ and the OP terminal ofthe transformer whose primary isconnected to the plate of therectifier is placed a resistance ofsuitable value. The plate of thenote magnifier is connected via -the telephones direct to the H.T.busbar with no intervening resis-tance. The effect of this is that,supposing that the single H.T.terminal is connected to the So -volt socket of the high-tensionbattery, the note magnifyingvalve will receive 8o volts on itsplate, whilst the rectifier will getonly 5o or 6o. If plate voltagesare properly adjusted in either ofthe ways described, results arevery much better, for no ordinaryvalve rectifies well with a highplate potential, and in the sameway amplification is not goodunless the plate voltage is high.If you give both rectifier and notemagnifier the same H.T. voltage,best results will not be obtained.If the rectifier is functioning wellthe note magnifier will probablydistort a little owing to thepresence of grid current. Thosewho possess ready-made setswith only one H.T. terminal canalter them very simply on thelines indicated, and they will findthat it is very well worth whileto do so, for reception is verymuch improved, especially uponstrong signals where the effectsof distortion are very much morenoticeable.

R. W. H.

Our photograph shows a huge " Brown" loud -speaker being placed in position at the WirelessExhibition. On another page may be seen an " Amplion" loud -speaker, also of large dimensions.

760


October 8, 1924

By

JOHN SCOTT -TA G GA RT,

THOSE who have visited.the N.A. R. M. Exhibitionat the Albert Hall will have

noted the remarkably goodreproduction of the 2L0 pro-grammes, and consequentlygreat interest will be taken inthe general circuital arrangementfor producing this result.

Those extremists who believethat the intervalve transformer

V /E

A.M.I.E.E.

essential portions. The part tothe left of the line A.B. includesthe aerial and earth- (no actualearth was employed), and a stan-dard commercial receiver, whichhad been modified so as to give astage of high -frequency amplifi-cation followed by a valve detec-tor. I cannot actually guaranteethat the circuit was identicalwith that shown to the left, but

,4

L3

C3

vi

EARTH MAT

Wireless Weekly

former. The coupling condensersC4, C5 and C6 have a capacityof .5 µF, while the grid leaksR2, R3 and R4 have a value ofI50,000 ohms.

It us to be noticed that thegrid of the valve V3 is connectedto a tapping on the grid leakR2, and by varying this tappingup or down R2 it is possible to

Ci 401210V

132

6Ye

GR/0 BATTER/ES

-110y1110111111111111111;110

pi -/67P

Br

Fig. 1.-Showing the general principle of the circuit used by the B.B.C. for demonstration purposesat the exhibition.

is doomed will receive no smallshock when they hear that threeiron -core choke coils and ""r% transformers are used in theapparatus.

This rather confirms my ex-pression of opinion in thesecolumns recently.

The CircuitThe general kind of circuit is

illustrated in the accompanyingfigure, and, thanks to the cour-tesy of the B.B.C. engineeringstaff, I was able to examine theactual apparatus employed.

It will be noticed that in thisfigure I have drawn two verticaldotted lines, A.B. and C.D., andthese are for the purpose ofdividing the circuit into the three

exactly the same effect wasobtained.

*The portion between the linesA.B. and C.D. is the low -fre-quency amplifier, while the por-tion to the right of the line C.D.includes the power amplifyingvalves V6, of which there wereeight in parallel, and an outputstep-down transformer T3 T4,and a loud -speaker L.S.

The Low -frequency Amplifier

It will be seen that the low -frequency amplifier comprisesseveral stages of choke coup-lings, the choke coils Zx, Z2, Z3being used. These chokes wereof substantial dimension of theorder of a large intervalve trans -

.761

vary the strength of the outputin the loud -speaker, this being avery convenient method of ob-taining a regulation of signalstrength.

Grid Bias and Anode VoltagesThe anode voltages of the first

two valves, i.e., the normalreceiver, is 40 volts, while 220volts are applied to the anodes ofthe valves V3, V4 and V5. Atapping is taken on the batteryB3 so as to give the grids ofV3, V4 and V5 a negative poten-tial of 16 volts. The valves V3,V4 and V5 are of the L. S.5 type.

The Power AmplifierThe power amplifier consists of

eight L.S.5A type, which has a


Wireless WeeKlymore open grid than the L.S.5,and has an amplification factorof from 2 to 3. These valvesare all connected in parallel, andthe output of the valve V5 isfed into the grid circuits of thepower valves V6 by mean,s ofthe transformer Ti Tz, which isa step-up transformer of i to 6ratio. The grids of the eightvalves, two of which are shownas V6 in the accompanyingfigure, are given a negativepotential by means of a grid bat-tery of about i to volts, while theanode voltage applied to thesevalves is 36o volts.

The very large output obtain-.able will be appreciated when it,

is mentioned that the normalanode current is 30o milliamps.through the primary T3 of thestep-down iron -core transformer,T3 T4. The low - resistancewinding T4 is connected to theloud -speaker L.S., which is ofa most modern type.

Lessons to be Learnt

This circuit diagram will be ofgreat interest to those who desireto give experimental demonstra-tions of loud -speaker results, andthe values given will indicatehow the valves may be operated.There is certainly no shortage ofiron in the circuit, and this alone

Post Office HypocrisyContinued from page 743-

a transmitting licence could begranted. The ironical part is that theofficial cannot accept the suggestion,because " it is like taking away theliberty of the subject to some extent."No doubt the Post Office would repu-diate the suggestion that to -day therestrictions on transmission are takingaway the liberty of the subject alto-gether.

Then, again, we have the followingpronouncement from a Post Office offi-cial : " We are most anxious toassist the amateurs and not standin their way," also, " We will. playthe game with you if you will play thegame with us.

Yet, again, we have the followingin an official letter : " The Post Officewould be loathe to impose addi-tional restrictions on bona -fide ex-periments."

The position of the Post Office offi-cials is truly a remarkable one. Wehave some officials as Vice -Presidentsof the Radio Society of Great Britain.No doubt these appointments weremade for the maintenance of friendlyrelations with the Post Office, althoughwhat these relations have brought wehave yet to discover. The Post Officehas flouted the Radio Society in nounmistakable manner. Whether offi-cials of the Post Office admire Dr.Eccles or not, the President of theRadio Society, the other day, made itquite plain that the Post Office didnot care two straws for the judgmenteither of Dr. Eccles or of any othermember of the Council. We happen toknow that applications for transmit-ting licences made through the RadioSociety of Great Britain are given 'themost careful and thorough investiga-tion, because the reputation of theSociety is at stake in these matters.A specially compiled list of applicantsforwarded by the Council were re-jected en bloc by the Post Office,which continually expresses its con-sidered policy of working in the closest

harmony with the representative asso-ciation of experimental interests.

When newspaper correspondents in-terview Post Office officials, they adopta bland air of innocence, and say theywill be happy to receive any sug-gestions, and nothing is further fromtheir intentions than to hinder experi-mental work. " Restrictions are neces-sary, but are always waived in suitablecases."

It is high time that this sort ofthing were cut out, and that a reallegal fight were staged, as a result ofwhich the position of experimentalwireless will be firmly established. Itis quite hopeless to obtain any reason-able satisfaction from the Post Office,and the Radio Society must now rely ontheir legal rights, and, we believe, thatnot only will no further restrictions beimposed, but many existing ones willbe wiped out as the result of a testcase. The Radio Society now havefunds for such a case, and we hopethat the matter will be brought to avery early issue.

We are able to disclose the fact thatthe recent restrictions inserted into newlicences were made without the know-ledge and against the wishes of Mr.F. J. Brown, the head of the depart-ment at the Post Office, who was awayat the time. Mr. Brown, however,apparently disagrees with the insertionof these regulations merely becausethey are of a provocative character,but he maintains that the regulationsare in force and that the Post Officehave the power to make them. He hasvery graciously consented to change aprohibition into a permission with arestriction, a Concession which leavesthe position identically the same, andwhich is an insult to the intelligenceof the Council of the Radio Society.

We publish in this week's issue anexample of Post Office methods in thecase of our Assistant Editor, Mr.Harris, one of the most competent ex-perimentalists in the country, who has

762

October 8, 1924

is rather enlightening as indicat-ing that the B.B.C. themselvesare not committed to resistance -coupling amplification.

I believe that the L.S.5Avalves are not actually on themarket, but are only provided tospecial order for certain commer-cial interests. I believe there isno particular reason why L.S.5valves or valves of this typecould not be used in the laststages, but since there is appa-rently a commercial demand forL.S.5A type, it seems strangethat the valve is not standard-ised. Perhaps the makers canexplain this.

0

just applied for a small modification ofhis transmitting licence. If this is themethod of dealing with an applicationof this character, we must sympathisewith the ordinary applicant.

Anyone who doubts the attitude toexperimental wireless in this countryneed only look at extracts from the pro-posed Wireless Telegraphy and Signal-ling Bill, which the Post Office havetried to pass through Parliament. Anexamination of its scandalous pro-visions will show the strangleholdwhich the Post Office could exercise, ifthe Act were passed.

Pressure of parliamentary business,only, has prevented the passing ofthis Bill, which would filch the experi-menter of his legal rights.

Meanwhile the Post Office areactually now exercising the rightsand powers which they hope to getunder this new Wireless Telegraphyand Signalling Bill, which rightt theyobviously realised they did notpossess under the Wireless TelegraphyAct, 1904.

Fortunately, this new Bill has notbeen passed, and we will exert everypossible effort to prevent its passage.

Meanwhile, it is, interesting to reflectthat the British Post Office officials,while quietly preparing this insidiousproposed Bill,' openly boasted of theirdesire to further experimental workand assist the amateur.

There is only one attitude to takeup towards such a Government depart-ment, and the Radio Society will befailing in its duty if it does not takeup that attitude at once.

THE

Wireless ConstructorTHE NEW SIXPENNY MONTHLY.

No. 1.OUT NEXT WEDNESDAY,

October 15th.No reader of "Wireless Weekly"must fail to buy this new

publication.ORDER YOUR COPY TODAY AND

AVOID DISAPPOINTMENT.


October 8, 1q24

A Simple Panel Switch

ASIMPLE panel switchmay be constructed fromspare parts, as shown in

the diagram, all that is necessarybeing two valve pins, one tele-phone terminal, some strip brass,and a small piece of ebonite. Theparts may be spaced upon thepanel to such dimensions as best

VALVE P/NS

TELEPHONETERMINAL

PANEL

R/YOTTAVGRLNRLYETTED OYER

JAWCUT BRAGS 457R/PBLADE

6U/DE FOR BLADE CUT /KmVALVE Pm. RECTANGULAR RILE

Constructional details of the switch.

suit the requirements of the con-structor, or the space availableupon the receiver. The blade,which is made of brass strip, ispivoted to a telephone terminal,as shown. To do this, first cut aslot in the terminal, insert theblade, and drive a pin throughthe existing hole in the terminal.

The pin, which should be a littlemore in length than the diameterof the terminal, is then rivetedover by flattening the projectingends down with a hammer. Thegauge of brass used for the con-struction of the blade should be atight fit in the existing slot inthe valve pin. The length of the

Flexible ConnectingLinks

.N4UCH trouble is often ex-perienced in making multi-ple link connections, where

it is necessary to place three or!more spade terminals under oneterminal. The diagram shows asimple method of overcoming thislittle difficulty. The links maybe made up to form two-way,three-way, or four-way connec-tions. It will be seen at a glance

Wireless Weeklyblade should, of course, clear the.distance between the telephoneterminal pivot and -the valve pin.The blade is equipped with anebonite handle, as shown. Aguide for the blade should be filedon the valve pins, as shown inthe enlarged diagram. To makea double - pole, double - throwswitch all that is necessary is touse four valve pins, two telephoneterminals, and two similar blades,the ebonite handle in this casepassing from blade to blade.

H. B.

0 0

that instead of having to placethree spade terminals under thedesired panel terminal, the threeleads shown in the diagram arebound together and attached toone spade terminal. If severalof these are made and kept in

Illustrating the multi connectinglink.

stock they will be found to bequite a useful acquisition forlinking -up units or loose compo-nents.

H. B.

One of the exhibits at the " All -British" Wireless Exhibition is a giant Amplion loud -speaker. Someconception of its size can be gathered from comparison with the neighbouring people.

763


Wireless Weekly

Making the Most of Power Valves

NOT so very long ago itwas almost out of thequestion for the amateur

to use a power valve for noteamplification purposes, partlyowing to its enormous currentconsumption for filament heating-one ampere was nothing out ofthe way-and partly because towork properly it needed two orthree hundred volts on the plate.The ordinary high-tension batterycould not be used because its out-put was insufficient for thesevalves, which frequently passedup to 15 milliamperes in the anodecircuit. To -day we have quite avariety of small power valves,such as B.T.H. B4, the MarconiOsram L.S.5, and the MullardDFAo, DFAI and DFA2, whoserequirements both for filamentand plate are quite reasonable.We may tabulate the figures forthese valves as follows :-

Fil. AnodeValve. Volts Amps Volts.

B.T.H. B4 ... 6 .25L.S.5 ... 4.5 .65DFAO ... 3.5 .35DFAI 5.5 .2DFA2 3.5 .25

8o -looxoo-z5o50-10050-10050-100

With too volts on the anodeand suitable grid bias the platecurrent consumption can be cutdown to the following figureswithout any loss in signalstrength :-

B.T.H. B4 ... 4 milliamperes.L.S.5 5 milliamperes.-DFAo 3 milliamperes.DFAI 4 milliamperes.DFA2 3 milliamperes.To get the very best out of a

power valve, however, one shouldr, , use a telephone

tranSformer and low -resistancereceivers. The reason is this.The last note magnifier haspretty large voltage variations todeal with. It is desirable, there-fore, that the working pointshould be as near as possible tothe middle of the straight portionof the grid volts -anode currentcurve, or at any rate that it shouldhe such that neither the tops northe bottoms of oscillations raiseit to` the saturation point or lowerit to the bend at the bottom of thecurve. Now the higher the volt-

age we apply to the anode themore we throw the whole of thecharacteristic curve over towardsthe, left.

Grid CellsThere is no doubt that every

set having even one stage of low -frequency amplification should beprovided with a grid battery.Unfortunately many boxed -insets are not so furnished, andthere are hundreds of amateurswho have made up sets withoutthis important fitting. Probablythe best way to deal with the

C2- II

LCI

C3

TERMINALS. 11.7 TERMINALS.

October 8, 1924

battery to the plus terminal, andtry the effect of using variousgrid voltages. As soon as themost satisfactory one has beenfound, the other tappings can becut off. The battery can then beplaced in a small box, and theleads taken to a couple of ter-minals placed on its lid. It willnot, as a rule, be necessary totap the first three cells, for thereare few, if any, power valvesneeding less than 4.5 volts onthe grid. If the task of break-ing away the pitch of flashlampcells does not attract, a simpleway is to purchase two Ever.Ready No. 15 refills which con-sist of large cells with only acardboard covering, which is

17?

IIWCRID BATTERY. . 100 le,..1

00 C0

0

V2

C6 -.IT-* Cs''''

5e

Fig. 1.-An ordinary detector and note -magnifier circuit adapted forapplying negative grid bias and separate anode voltage to the last valve.

matter is to disconnect the leadwhich runs to the low - fre-quency intervalve transformerfrom L.T. negative, and to inserta pair of terminals in a conve-nient place upon the panel. Con-nect one of these to L.T.- andthe other to the vacant trans-former terminal. Mark the firstplus and the other minus. Ob-tain a couple of flashlamp bat-teries and join them in series bysoldering the short (positive)strip of one to the long (nega-tive) strip of the other. Taketappings at each cell. This canbe done quite easily by breakingaway the pitch covering at thetop and soldering flexible leads tothe connecting wires. Takecare, by the way, not to let thebared ends of your flexible leadstouch, otherwise you will short-circuit some of the cells. Nowconnect the positive end of the

764

easily removed. As the cells arec"nnected by brass strips, it is asimple matter to solder leads on.

H.T. VoltageThe next problem to tackle is

that of supplying a higher volt-age to the anode of the powervalve than to that of others inthe set. It is first necessary toget a telephone transformer,which may be purchased cheaplyfrom advertisers. There willgenerally be plenty of room forthis beneath the panel. Keep itwell away from the other trans-formers so that interaction willnot take place. To wire thistransformer disconnect the plateand H.T. plus leads from thetelephone terminals, and connectthe plate lead to one of the trans-former primary terminals, con-necting its secondary to the tele-phone terminals. Now mount an


October 8, 1924

additional H.T. plus terminal onthe panel. Connect this to theunoccupied terminal of the tele-phone transformer's primary.The existing high-tension batterycondenser should be left in placeand a second should be fitted inshunt with the too -volt high-tension lead. These small altera-tions can, as a, rule, be carriedout without much difficulty inany set, and it will be found thatthey will make an immense differ-ence to its performances even ifan ordinary valve and not apower valve is used as note -magnifier.

Power AmplifiersThe power amplifier excels for

low - frequency amplification,largely on account of its design.Fig. 2 shows the parts of atypical small -power valve. Asinter -electrode capacity will notbe of much moment in a valvewhich has to deal only with low -frequencies, both the plate and

A Neat Wiring Tip

OOO ASIMPLE device for neatwiring which entirelyeliminates the using of

solder may be achieved asshown in the diagram. Althougha little time and trouble will

NUT SCREWED UPWARDS

TO GRIP WIRE -

SAWCUT

DRILL if: DIAN

ENLARGED PLAN Of END Of SCREW

The wire fitted to the terminal.

be expended in preparing thepanel fitting screws, it hasits compensations by reasonof the fact that the con-nections may be altered fromtime to time with a minimum oftrouble, without having to getout one's soldering outfit. Allthat is necessary is to first drilla 1 /16 in. diameter hole down the

grid spiral can be made of largediameter. In most types theyare oval in form, the grid beingvery open. The filament ismuch longer than is the case invalves of the ordinary type, andthe volume of electron emissionis therefore very great. Further,as the internal resistance of the

P/NCH

Fig. 2. -The electrodes of a powervalue.

centre of the screw, as shown,and then make a cut across itwith a fine hacksaw. When1/16 in. square tinned copperwire is forced into the 1/16 in.

Wireless Weekly_

valve is generally not muchhigher than to or 12,000 ohmsas compared with an average of40,000 in ordinary valves, thepower amplifier is capable ofpassing a greater amount of cur- 'rent in the anode circuit. Themodern small -power valve is adull -emitter, and it makes there-fore a Very small drain upon theaccumulator. This low con-sumption is an enormous advan-tage, but the fact that they are'dull -emitters brings one smalldrawback in its train. Allvalves fitted with filaments of thiskind are inclined to be moremicrophonic than bright emitters,and small -power valves are noexception to the rule. However,if the set is placed upon a padof baize or other material themicrophonic qualities of thepower yalv.e will not be noticedunless it is actually tapped withthe finger. I"

R.W. H.

'

diameter hole drilled, the nut(which should be already on thescrew) when screwed upwardswill tightly grip the wire.

H. B.

FRENCH EXPERIMENTERS

An enthusiastic group of members of the Sociki. Francaise d'Etudesde T.S.F. photographed during an experimental trip down the Seine.

Note the loud speaker on the top of the cabin.765


Wireless WeeKly

Si

91

to

to

rs

el T is only a year or two sinceall wavelengths below 600metres were looked upon as

" short," but nowadays theexperimenter who cannot gobelow zoo metres on his tuner islooked upon as out of date. Ourold friend KDKA, which lastwinter amused and intrigued usby working on the fascinatingwavelength of zoo metres, hasnow abandoned this commonplayground and slid down tosixty metres or so, on which ad-justment his strength of signal isabout double what it was before.In the United States theamateurs are preparing to go aslow as four or five metres, butthere are some really big pro-

m blems to solve before satisfactoryreception is likely on such waves.

75-100 Metres.Meanwhile, it will be interest-

ing to consider a few points intuner design for -wavelengths inthe neighbourhood of 75 to zoometres - a most interestingband for the listeners who havebecome interested in somethingmore than broadcast pro-grammes.

stNow, excluding super -hetero-

dynes, specially designed neu-trodyne receivers, and others of

is considerable complication, it isnext to impossible to get satisfac-tory high -frequency amplificationon such short waves as these.

Itl

E ISMIINEISINNO 111 II IS IP I

IS IS PI IS DI Si PI In

A detector and note magnifier panel which has been used for fifty -metrereception. Note external grid leak clips.

IS

The efficiency of radiation js ex-ceedingly high on the shortwaves, and it will be found thatin practically all' cases a detec-tor and one note -magnifier willgive all that is required. Inci-dentally this is the combinationused by most of those British

Fig. 1.-Diagrammatic representa-tion of a simple short-wave tuner.

amateurs who are working two-way schedules with the UnitedStates, and now that the darkerevenings and better atmosphericconditions are coming, it shouldbe possible to receive 100 -metresignals from the United Statesalmost any night with thisarrangement.

Short Wave CircuitsI have tried a number of

different circuits on short-wavereception, and have come to theconclusion that there is nothingto beat a loose -coupled combina-tion with reaction on to thesecondary coil and an aperiodicaerial coil consisting of a fewturns of wire wound in a hankas shown in Fig. z. A good

NE PIN7.66

as

October 8; 4024

II EN N 111

One Hundi. . . . and

By PERCY W. HARI

Some Points on Sh

tuner for zoo metres can bemade up with five or six turns ofwire as the aperiodic aerial coilwith a .000i fixed condenser inseries with it, and about 2C

turns of No. 16 or 18 d.c.c v ireon a three-inch tube not shel-lacedt or treated in any way, asthe secondary. If you shellac ozwax the coil you add to the self -capacity and reduce the efficiencyconsiderably, so I recommendyou to wind it on a tube of eitherpure ebonite or of well -dried cardboard, the latter not waxed,but very lightly shellaced, afterbaking, to make it impervious tomoisture. The reaction coil canbe 15 to 20 turns of No. 18 or20 -gauge wire. The secondaryshould be tuned with a variablecondenser not bigger than .0002mfd., or the tuning will be sosharp that you can easily missthe station you want. All leadsfrom the coil to the condenserand to the grid and filamentshould be as short and direct aspossible.

It is now generally consideredan advantage to make the coup-

.

A back of panel photograph sh

la II II 111 II II II CI CP 11

0


October 8, -1924 Wireless WeeklyIIII EN IIII111111-M

ied Metres;elow .

IS, Assistant Editor.

rt Wave Reception.

ling between the aperiodicaerial coil and the secondarycoil variable, while, of course,the reaction coil must have aoupling which is variable inelation to the secondary coil.

very good make-up is to tiethe aerial and reaction coils onwooden rods provided at eachend with bearings, so that theycan be easily rotated. Whetheror not you find a series con-denser in the aerial necessarywill depend upon your aerial, andyou will be surprised to see howloose the coupling between youraperiodic aerial coil and yoursecondary can be on short waves,

Low Capacity Valves -You need not make any spe-

cial endeavour to get very lowcapacity valves, unless you areworking below 75 metres. Low -capacity valves of the tubulartype have particular virtues whenwe use them in high -frequencycircuits for short waves, wherethe capacity between electrodesis the unwanted source of feed-back.

tying the simplicity of the wiring.

11 II II

A photograph of the underside of the panel showing disposition ofcomponents.

As we have no radio -frequency tuned circuit connected in theplate there are no two tuned cir-cuits to interact. The value ofthe grid leak should be watchedcarefully on these short waves.

In making up your tuner keepthe tuning coils well away from

Fig. 2. -Method of securing thehank coil.

the panel and from the base-board. A good plan is to keepthem about at least two inchesfrom both of these, by means ofwood brackets or supports. Theconstruction of the aerial coil isa very simple matter. It is onlynecessary to take some cylindri-cal object about three inchesdiameter (a jug or bottle willdo), and to wind the turns roundit, slip them off, and tie them inthree or four places with stoutthread ; the coil can then be tiedto a rod (see Fig. 2), andmounted so as to be able torotate it as closely as possibleto the secondary coil. An alter-native variable arrangement ismade by sliding the coil to andfrom the secondary coil or byhinging it so that it can openaway from the end of the coilwhen necessary.

Whatever form_ of tuner youuse you will need a detector andnote -magnifier panel, and thiscan be made up in permanentform for use on any wayeleng-th.I am illustrating in this articlemy own detector and note -mag-nifier panel, which I have usedsuccessfully with various kindsof tuner down to about 5ometres. There are no particularnovelties in its make-up exceptthat the clips for the grid leakare placed outside the panel sothat various values can be triedat will. You may wonder whyI have not fitted a variable gridleak instead of clips and fixedleaks, thus saving myselftrouble. The answer is that Ihave yet to find a really reliableand permanent variable grid leakwhich can be calibrated. Thereare several variable grid leakswhich are capable of adjustmentthrough a wide range of values,but not one of them is sufficientlyconstant in its setting to be cali-brated. I hear rumours that awell-known firm is shortly toplace a really reliable and cali-brated variable grid leak on themarket, and I hope the rumouris true. Meanwhile, I keep onthe bench a box of calibratedgrid leaks from to 5 megohms,and I substitute these as- andwhen necessary with full confi-dence that I am getting thevalues indicated.

Notice particularly that theleads inside this amplifier are ex-ceedingly short.

M M M El b M CI 13 111 MMM CM al 31 El RI a t3 ;13 El IS 3 Ea El fig 33 It 211

67

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Wireless WeeKly October 8, 1924

The component parts neces-sary to make this panel are asfollows. I have mentioned afterthe components the particularmakes used, but these can beexchanged for others without

Fig. 3.-The Harris lowloss coil.

detriment, provided the substi-tutes are of good quality.

One panel, 14 x 51 x 3/16(Radion panel).

10 terminals.2 filament resistances (Edis-

wan).

CAROWARD STRIPS -

Fig. 4.-A simple way of making alow loss coil, due to M. B. Sleeper.The wire is wound over gummedstrips which hold the coil when thebottle is withdrawn.

2 sets valve sockets.pair of clips for grid leak.

i fixed condenser .0003 mfd.(Dubilier).

io terminals.Set of grid leaks, or, if only

3/4

one is decided upon, the usualvalue of 2 megohms.

I fixed condenser .00i mfd.(Dubilier).

intervalve transformer(Wood h all).

box about 5 in. deep.Square wire for wiring.There are no particular diffi-

culties in the constructionalwork. If you use a 'Radionpanel you can make up your seton this right away, as it has apolished black surface which isguaranteed free from leakage." Paragon " panels of PeterCurtis, Ltd., Peto-Scott " Pilot "panels, and Bowyer -Lowe guar-anteed ebonite can all be used asreceived from these PeOpIe, -butall unguaranteed ebonite requiresthe surface to be removed. It ishigh time manufacturers stoppedselling panels from which it isnecessary to remove the surfacebefore commencing work. Theaverage experimenter has quiteenough to do without the labori-ous process of rubbing downebonite with emery. Now that-thanks to consistent advocacy inthis journal-there is plenty ofguaranteed ebonite obtainable,I strongly recommend readers toinsist on having it. It is worthpaying a little more for suchebonite, if you consider yourtime of any value at all.

Filament ResistancesSo far as the filament resist-

ances are concerned, these, ofcourse, should be bought for°ither bright -or dull emitters asrequired, or you can, if you wish,use the type of resistance such asBurndept's, which can be used

214;

14"

OR

R

for either bright or dull emitters,according to the position of theslider.

Short -Wave Plug-in CoilsBurndept's and Gambrell's,

-c0.001

JJP

1.1

0

0L.r

O

Fig. 5.-Circuit of the detector andnote magnifier panel.

and just recently one or twoother firms, are selling specialshort-wave coils, which are verygood for too metres work. These

Ro

L3

0 0005 ji F

R0

L 2

AQ99.99)

60

0 00025H F+ vernier

E

Fig. 6.-Three coil tuner for theFig. 5 circuit.

0

can be used in a three -coil holderwith a series condenser of .0005mfd. in the aerial and one of

4Y4"

Fig. 7.-The layout of the panel and drilling dimensions.768


October 8, 1924 Wireless Weekly

+ LT -

E

Fig. 8.-Practical back of panel wiring diagram.

.0002 or .00025 mfd. in the closedcircuit. A vernier is preferableon the closed circuit condenser.For Too metres reception it ispractically useless to endeavourto receive with a direct -coupledcircuit, so do not waste yourtime in this way if you wantresults. At first, though it mightappear that handling a loose -coupled tuner on too metreswould be a very critical matter,actually the tuning of the aerial

is not at all critical ; it is thesecondary tuning which requirescare.

Use a Heterodyne Wavemeter

To do any really successfulwork it is imperative to have aseparate heterodyne properly cali-brated as a wavemeter. I de-scribed one of these in WirelessWeekly last winter, and it hassince proved very useful. It isalso recommended in considera-

The Proposed Wireless Telegraphyand Signalling Bill.

AN extract from a bill whichthe British G.P.O. havebeen trying to get passed

by Parliament. This bill hasbeen previously published, but itis very relevant at the presentcrisis as showing how the PostOffice have vainly attempted bythis proposed Act to gain powerswhich they are, in fact, nowillegally exercising. The passageof this Act, unnoticed, wouldgive the Post Office unlimitedpowers, and deprive every privatecitizen of the right to possess orwork a wireless set. Our owncomments on the consistent re-pressive attitude of the PostOffice appear in the Editorial.

Copies of this proposed Actmay be obtained from Membersof Parliament.

BE it enacted by the King's mostExcellent Majesty, by and with theadvice and consent of the LordsSpiritual and Temporal, and Commons,in this present Parliament assembled,and by the authority of the same, asfollows :-

i.-The Wireless. Telegraphy .Act,

1904 (hereinafter referred to as theprincipal Act), shall become a per-manent Act, and any provision in anyAct in force at the time of the passingof this Act which limits the period forwhich the principal Act is to remain inforce shall cease to have effect. '

2.-(x) The Postmaster -General may,notwithstanding anything in the prin-cipal Act, make regulations-

(a) as to the terms, conditions, andrestrictions on or subject towhich licences of any class oflicence under the principal Actare to be granted, renewed,suspended, or withdrawn; and

(b) requiring any operators or otherpersons engaged in the workingof wireless telegraphy to be pro-vided with certificates, and mak-ing provision as to the mannerand conditions of the issue andrenewal of any such certificate,including the examinations andtests to be undergone, and theform; custody, production, can-cellation, suspension, endorse-ment and surrender of any suchcertificate, whether issued beforeor after the passing of this Act;and

(c) for preventing interference withthe working of wireless tele-graphy by the generation or useof etheric waves for any purpose

769

tion of other listeners who will beannoyed by any autodyne recep-tion on your part. Of course,when you react on to a secondarycircuit which is loosely coupledwith the aerial, you mightimagine that practically nothingwill be radiated, but, owing tothe efficiency of radiation onthese wavelengths, you mayactually cause a good deal ofinterference in this way.

other than the transmission orreception of wireless messages;and

(d) for giving effect to, andcompliance with, the provisionsof any international conventionsigned on behalf of His Majesty,and any regulations made there-under, so far as the same relateto wireless telegraphy; and

(e) prescribing, subject to the con-sent of the Treasury, the feesto be paid in respect of thegrant or renewal of any licenceor certificate.

(2) Regulations under this sectionmay provide that any person actingin contravention of or failing to com-ply with the regulations or any ofthem, or the terms, conditions and re-strictions or any of them, on or sub-ject to which any such licence or certi-ficate as aforesaid has been granted,shall be liable, on summary conviction,to imprisonment for a term not exceed-ing three months, or to a fine not ex-ceeding fifty pounds, and, in the caseof a continuing offence, a further finenot exceeding five pounds for each dayduring which the offence continues.

(3) Subsection (6) of section one ofthe principal Act is hereby repealed.

3.-Subsection (1) of section twoof the principal Act, which makesspecial provisions as to licences forexperimental purposes, shall ceaseto have effect, and licences for thosepurposes shall be subject to thegeneral provisions as to licences forwireless telegraphy contained insection one of the principal Act.


Wireless WeeKly October 8, 1924

A Handy H.T. and L.T. BatteryConnector

AHANDY combined high-tension and low-tensionbattery connector may be

made as shown in the accom-panying diagram. The chiefobject of its design is that itcannot cause a short circuit byaccidentally bringing the leadsinto contact with each other, eachtag being shorter than the pre-ceding .:one.. A piece of twininsulated flex 3 ft. long will berequired for the high-tensionbattery connections, and a further

. piece of twin flex, 2 ft. 6 in. long,for the low-tension battery con-nections. The H.T. flex shouldbe blue silk covered, and the L.T.flex red silk covered, or any twodistinct colours may be used.The two lengths of flex arebound together, as shown in the

diagram, and each of the eightends provided with spade termi-

oH.T.-0

(:.

+0

-0`1;14L7:

61_22_1.1

H.T. -, and so on, or alterna-tively, the distinguishing marksmay be engraved upon the spadeterminals or wander plugs them-selves. Where a common termi-nal is used on the receiver forL.T. and H.T. - connections,these corresponding ends may be

/2"

7-44

H.7: -'-

1.41

Constructional details and dimensions of the battery connector.

nals or wander plugs, as desired,To ensure the elimination of anypossible mistakes in linking -upthe connector between thebatteries and the receiver, papertags may be secured to each ofthe eight ends and labelled H.T. +

THE EXHIBITION

bound together on the connectorand secured by one spade termi-nal, as shown in dotted lines,resulting in this case in three endsonly on one side and four on theother.

H.B.

Our photograph shows Lord Riddell on the left, inspecting a very handsome loud -speaker made by Sterling's.Mr. W. W. Burnham, chairman of the N.A.R.M., may be seen on the right.

770



A Dull Emitter Warning

Isuppose that most of thosewho live in the country likemyself make use of dull

emitter valves of one kind oranother chiefly because it is sodifficult to get accumulatorscharged. There is always thebother of lugging them round tothe charging station, and unlessyou keep a watch,ful_ eye on thosewho do the job you may easilyfind the battery is quickly ruinedby their attentions or lack of,attention. With the dull emitterthe charging problem is greatlysimplified, for a visit to the sta-tion every two or three monthswill usually suffice. There isone point which dull -emitterusers do not appreciate. Whenyou are using bright emittervalves consuming from i ampereto .1 ampere apiece, the accumu-lator very soon lets you knowwhen it needs to be charged by

0 0

Note on Headphones

THE writer would like tobring a little suggestionbefore the notice of manu-

facturers, who may be interestedin a small improvement to head-phones, resulting in greatercomfort to the wearer. In mostof the patterns at present on themarket the ear pieces areattached to the headbands bymeans of a spring clip which ispivoted on to the metal portionof the ear piece. This results ina certain amount of discomfort,as the headbands are stretchedover, and do not fit on to the head,the earpieces themselves alsohaving an angular position whenworn. This could be simplyremedied by pivotting the earpiece, not on the metal container,but on the ebonite cap. Thepoint of pressure is then directon to the ear, the headbands fitround the head and are notunduly stretched, and greatercomfort is obtained. The writerhas tried and found this devicesatisfactory.

H. B.:

simply refusing to light up thefilaments at their proper brilli-ance. But with dull -emittervalves this warning is not so ob-vious. Nor will a voltmeteralways give a proper indicationof the condition of the batteryowing to the smallness of theload., It may thus happen that abattery is run down without theowner's realising it. Many anaccumulator is ruined in thisway, for to run it down too lowmeans nearly always that sul-phating will occur, and thatspells disaster to the plates. Thebest tip I find is to keep on thewireless table a small piece ofcardboard on which are made anumber of strokes or " ones "equal to rather less than thehours of service that the batteryshould give. Suppose that yourbattery is rated at 5o amperehours actual, and that you are

using two dull -emitters whosefilaments each consume .25 am-pere. Your consumption perhour is ampere and ,the batteryshould give a too hours of ser-vice when it is newly charged:Make ninety strokes on yourcard and cross off one for eachhour that_ the set is used. Thecard then gives a good indication,of the state of the battery, and.there is no danger of running itdown too low.

R. W. H.

BLUE PRINTSFull-size blue prints of the wiring ofall the principal Wireless Weeklyand Modem Wireless Receivers canbe obtained from the Sales Dept. ofRadio Press, Ltd. In some cases blueprints of the panel drilling Can also beobtained, the price in each case being1/6 post free.

A "pinch " making machine at the Marconi Osram valve works.771


Wireless Weekly

_

/440%60#' "*a---

Terminals

October 8, 1924

Apparatuswe have tesled

Conducted by A. D. COWPER, M.Sc., Staff Editor.

Messrs. Gent & Co. have sub-mitted for our inspection samples oftheir " Tangent " ' terminals forelectrical connections. In these, thetendency generallydisplayed by ter-minals to squeeze out the wire aideways when an attempt is made totighten them up for secure connec-tions (particularly when more thanone wire is placed on one terminal)is effectively combatted by makingthe surface of the fixed portion of theterminals in the form of a curvedgroove, whilst the nut has its lowerportion shaped to a rounded cone(roughly hemispherical in thesmaller size) of a nearly equalradius. The result is that a wire,once inserted in the groove, is forceddown to the bottom of the latter,rather than squeezed out sideways,when the nut is screwed down, giv-ing a most secure hold and greatlyfacilitating rapid connections am.disconnections.

On trial, it was found that secureconnections could be made withwires of different sizes with thegreatest ease, even when only onehand was available. Quite thickwires were readily secured, withoutbending the end into a loop. Theterminals did not appear to beadapted for spade ends, which, how-ever, become unnecessary with thistype of binding -screw. The samplessubmitted were highly finished andnickel -plated; they were of substan-tial build, the bases in particular ofthe larger sizes being quite massive.For thick aerial and earth connec-tions, and especially for telephoneleads, these can be heartily recom-mended.

Plug -In Coils : "Pentawave "

A set of four plug-in coils of aparticularly compact form has beensubmitted for test by Messrs.Thomas & Co. These are all 21inches outside diameter, by inchthick ; are enclosed in a smooth,black cover of neat appeararice, andare provided with the usual plug -and -socket mounting. The smallsize, and unusually high D.C. re-sistance of these tuning coils ap-peared to suggest the probability ofa fairly large H.F. resistance; this

was confirmed in actual test, con-siderable difficUlty being eXperiencedin obtaining oscillation with theNo. t in the aerial -tuning position,when using a liberal bright -emittervalve and ample H.T., and whetherwith series or parallel tuning -con-denser. The tuning was also noticedto be markedly flat.

The makers giVe particulars oftuning range with these coils, whichappear on close examination -to havebeen based on a minimum tuning

wavelength, or to just under t,800metres with the No. 4 and .00i uFtuning condenser. An appreciablegap was left between the No. t andthe No. 2; under these circum-stances No. 3 had to be used forreaction with both Nos. t and 2.When effective reaction was onceobtained a test in actual receptionOf local broadcasting came up toabout the usual level of plug-incoils.

An interesting panel support.

capacity for a P.M.G. aerial plusstray capacities of the set, etc., ofabout .0006 /IF, with a maximumtuning capacity (.00i /IF tuning con-denser) of about .0016µF, whichdoes not correspond with the bestpractice on the shorter waves. Witha low -minimum :000s /IF tuning con-denser and the more usual figure fora P.M.G. standard aerial of .0003µF plus casual capacities of, say,.000t, the ranges recorded were actu-ally, with the samples submitted,from about 350 to 1,420 metres

772

Drilling jig for Valve -LegsMessrs. Baker & Finnemore, Ltd.,

have sent us a sample of their drill-ing -jig for valve -legs. This is ahardened rectangular steel plate21 inches by 13 inches, with a centrehole for a No. 4 B.A. bolt, and thefour holes for the valve -leg spac-ing.' This is- to be bolted down onthe panel by a No. 4 B.A. bolt (oneof which is provided with the fit-ting), a No. 26 drill making thenecessary hole; and the other fourholes are then drilled through the


October 8, 1924

jig guiding -holes. The rectangularplate facilitates_ the setting true tothe edge of the panel.

On trial, this jig proved conveni-ent in use, and gave the correctsetting of the legs for the averagevalve. It is evidently carefullymade, and is highly finished.

Wander -PlugFrom Messrs. A. H. Hunt, Ltd.,

comes a Sample of a new type ofwander -plug. -In this plug the wirecomes out at the top of the insulat-ing handle, a bared portion being

- -nipped between an internal cone inthe latter and the conical,erid of thebrass plug, which screws into tl- eformer. The usual split tail is. pro-vided to obtain secure contact in thebattery terminal holes; This -makesan extremely neat and effective fit-ting; and on trial the wire wasfound to be nipped tightly, a goodelectrical connection being readilymade.

Fixed CondensersMessrs. Peter. Curtis, Ltd:, have

sent us a sample of the new `.` Pera-gon-Curtis-" . one-piece condenserwhich is moulded in " Paralite "- insulating material forming a closedcase, so that the makers claim thatit can actually be boiled' for 24hours without showing any change.

In the sample submitted small:screws were provided for terminals,

projecting from the side of acase of the usual size, viz.,2 inches by inch. As the nominalcapacity was not marked on thecondenser, the accuracy and per-manence of capacity could not profit-ably be tested.

A Two-way Vernier AttachmentCoil Holder

Messrs. Burnley Components,Ltd., have sent for test a sampleof their fwo-coil holder, for panel orcabinet -mounting, with a fine -adjust-.ment feature. In this instrumentone coil -plug is mounted on aspindle controlled by the usualebonite knob, turning stiffly in anebonite base. The other is alsopivoted, at a distance of aboutfi inch centres from the first,but is moved through an angle of

.approximately 15 degrees by amicrometer screw operative in eitherdirection, working in a swingingbridle. The first holder having arange of over go degrees of arc,considerable latitude of adjustmentof coupling is thus provided, with afine or " vernier " adjustment avail-able at any point of adjustment.

The instrument is quite compact,being mounted on a base but 2tinches square. The two controllingspindles are necessarily at rightangles to one another; the fine -ad-justment spindle being of good

Wireless Weeklylength (about 4 inches) and insu-lated from the coil -connections thehand -capacity effects are reduced toa minimum. On trial, the mech-anism operated smoothly, and gavethe desired fine control over couplingof the coils. By tightening suffi-ciently a set -screw at the end of themain spindle the holder could bemade stiff enough to carry thelargest and heaviest sizes of plug-incoils.

Panel SupportsWe have received from -Messrs.

Prince Bros., of Cleckheaton, a setof " Constructor's Panel Supports,"for use by constructors when build-ing up a new set.

The ebonite panel .is secured. inthe milled slot at the top by theknurled set screws. The panel. canbe marked off and drilled, the com-ponents fitted and wires soldered,thus obviating the old method ofpacking with boxes.

This operation completed, thepanel can be reversed, and the legsadjusted till components clear thework bench, when a test can beperformed.

We can unhesitatingly recom-mend these supports, which are agreat help to the home constructor.Our only criticism is that theymight with advantage be longer.

REDUCTION IN PRICESOF B.T.H. RADIO APPARATUS

Announcement!THE demand for B.T.H. Radio Apparatus is constantly increasing, and so also

is the output of our factories. Because of this, we are now able to announcethe following substantial reductions in the prices of " Bijou" Crystal Receivers,Loud Speakers and Amplifiers.Radiola "Bijou" Crystal Receiver Type Cl Loud Speaker.(Without Headphones). A highly efficient easily tuned The ideal loud speaker for a small room.receiver. Old Price £2 5 0 NEW PRICE £2 0 0 Old Price £3 0 0 NEW PRICE 22 10 0

Type C2 Loud Speaker. Type C3 Loud Speaker.A beautifully finished instrument for general use in and A gramophone attachment having the sane element asout of doors. Old Price £5 5 0 NEW PRICE £5 0 0 the Cl loud speaker. Old Price £2 7 6 NEW PRICE 82 2 0

Tpye D Loud Speaker. Single Valve Unit Amplifier.A super -sensitive electrodynamic pattern suitable for Fitted with plugs and sockets for the inter -connectionlarge halls or outdoor use. of two or more units.

Old Price £12 10 0 NEW PRICE 29 10 0 Old Price £3 5 0 NEW PRICE 22 15 0Two Valve Power Amplifier.

An amplifier designed for use with loud speakers when a large volumeof sound is required. Old Price £16 0 0 NEW PRICE £12 10 0

Obtainable from all Electricians and Radio Dealers.

The British Thomson -Houston Co., Ltd.Works : Coventry.

Branches in all

11111111111111111111111111111111111111111111111111111111111111111111111I2239A

773

Offices : Crown House, Aldwych, W.C.2.Large Towns.

111111111111111111111111111111111111111111111111111111111111111111111111


Wireless Weekly

Corre

TYPE WI RECEIVERSIR,-Herewith brief report on

stations received on the aboveset. Birmingham, Manchester,Radio Belgique, Chelmsford,Eiffel Tower, Radiola, London,Bournemouth, Cardiff, Notting-ham, Newcastle, Glasgow, Aber-deen, P.T.T. and Petit Parisien allaudible on loud -speaker.

,Madrid, Hilversum, Frankfort,Konigwusterhausen, etc., Voxhauson 'phones, also four German andthree other foreign stations whosecall signs I cannot understand. Allthe above using constant aerialtuning, amateurs 43, including 2VGand 2KV and 2LF. The followingMorse stations were logged onAugust 6: OAA, 8BV, 8BN, 2TF,IRA, 8NK, INA and 5JX.

The only variation from specifica-

tion is the use of a Sterling squarelaw condenser.-Yours faithfully,

TALBOT.Coventry.

CONSTRUCTING COILSSIR,-With reference to your

article on p. 555 August 27, on " ALow Capacity Coil," we have forsome time been experimenting withthis type of coil, British PatentNumber 196986, and think per-haps the following labour-savingdevice may be of interest to yourreaders. If headless nails are usedand a piece of card is pressed overthem before winding on the wire,the completed coil may be removed,by lifting the card, without thetrouble of displacing, and afterwardsreplacing, any of the nails, as sug-

October 8, 1924

Bested in your article.-Yours faith-fully,

W.6.

FIDDIAN, BAWTREE & CO.D. W. BAWTREE.

SINGLE -VALVE REFLEXSIR, --I have just constructed the

single -valve Reflex receiver shown inWireless Weekly of September 3 andio in the article entitled " HowEvery Crystal User May Become aValve Expert," by E. Redpath. Ifeel I must write and thank Mr.Redpath for this excellent article;the results with the set are splendid.It is only a rough job, but the fol-lowing stations prove it to beefficient, viz., London, Manchester,Newcastle, Glasgow, Belfast, Bir-mingham, Aberdeen and L'EcoleSuperieure, Paris, and these on the

rT71"TTAS.,. q. _i, ,e, 1,...ft.t._..vr-0 ,,. ow...10 v. c.,...W., ,..fq!,5VG--

1

by

C.

The Components illustrated are :-1. E F ES CA HIGH FREQUENCY

TRANSFORMER.-Specially recommendedwhere more than one stage of high frequencyamplification is required. Can be employedimmediately preceeding a reactance coupling toform two high -frequency stages or any numberof separate transformers may be used in com-bination. Can also be used as a Tuned AnodeTransformer by shunting the primary will a.0003 mfd. variable Condenser in any numberof stages. Wavelength range, 150-2,600 metres,complete as illustration, wound on eboniteformer, 21/-. Ditto, embodying Grid Leakand (.0003) Condenser, for use as Transformerconnected to Detee or Valve, 25/-.

2. EFESCA SPEECH AMPLIFYINGTRANSFORMER TYPE "C." This Trans-former is designed to give the amplification of apower Transformer without 'the loss in purityof reproduction generally experienced withpower amplification. The coil is wound in aspecial manner to neutralise resonant effect,while the laminations of the core are extra care-fully insulated from each other to localise eddycurrents and thus prevent distortion. Ratio

21 one hole fixing 25/-.

3. EFESCA ANTI -CAPACITY SWITCH(Patent applied for).-A double pole, doublethrow switch, specially designed to minimisethe capacity which exists in most change -overswitches. The contact brushes are of phosphorronze and present only their edges to each

other with a comparatively wide air gap-thuspractically eliminating all capacity effects. Theorerating lever is at no time in electricalcontact with the carrying block which makescontact with the brushes. Price 8/- each.

sirrea"M"W19'sgesrM'rraWei'res.0.Wriroviras sm

You can build abetter set with

en

ONE -HOLE FIXING WIRELESS COMPONENTS.There is hardly a wireless enthusiast who is entirelysatisfied with his set. He wants still better results-and they can be had by building with Efesca parts.Each is designed to give the maximum efficiency. Acombination of Efesca components, therefore, leavesnothing to be desired. Each part is the outcome ofmuch careful study-a real scientific instrument ofunique design and first class workmanship. Theyare stocked by wireless dealers, ironmongers, ande ectricians.

Learn more of Efesca parts by sendingfor Catalogue 522 which contains thefull range. It's FREE.

For those not interested in the constructional side there is a widerange of complete Efescaphone Sets from the simple crystal set tothe malti-valve receiver for loud speaker and long range work.

Wholesale only :-FALK, STADELMANN & CO., LTD.,Efesca Electric Works, 83-85-87,Farringdon Road, LONDON, E.C.1.

And at Glasgow, Manchester. and Birmingham.

ei

a

ay

4

1

774


October 8, 1924

first " try -out " night after the con-struction was finished, with onlyIgranic coils Nos. 35, 5o and 75 inuse. I have constructed one or twoprevious sets from the articles inyour excellent tapers; notably theTwo -Valve Universal Receiver inWireless. Weekly of December 5,1923. This was a fine set, but mysingle -valve Reflex gives much betterresults. -

I am using 0.0003 ,LLF variablecondensers, as I happened to havethese by me.

With the best of wishes for thefuture of your excellent papers,Wireless Weekly and Modern Wire-less.-Yours faithfully,

Northwich. T. N. G.

AN EASILY MADE COILHOLDER

SIR,-I enclose herewith a roughsketch of an easily -made variabletwo -coil holder. It was inspired bythe article on " Cross -Coupling " inWireless Weekly of June ix, 1921,p. 185. Everything can be boughtfrom stock except the shaped pieceof ebonite D. This is easily de-signed and made with the help of apair of compasses and a drill. It iseasy to see that by making a secondmovable holder with the shapedarm D reversed and the spindleplaced at right angles to the firstspindle, the position in Fig. 5 in the when fully open.

L

PL A

Wireless Weekly

PAVMZffMein

7 A7fin

SECT/ON

above -quoted article is

sueA

obtained

c dCONSTRUCTION.

Determine positions ofa, b. c. d. Join a to asd,c io b. Bisect these lines.

Intersections at eform required centre.

An attachment can easily be addedfor fine coupling if desired.

THE NEWDEXTRAUDION "

DULLEMITTER

ECONOMICELECTRIC

MAXIMUMCONSUMPTION

1 AMP. AT 1 VOLT.

THE QUALITY OF THERECEPTION -ENTIRELY SUR-

PASSES ANYTHING HITHERTOOBTAINED WITH ANY OTHER VALVE.

Full particulars, with characteristic curves, togetherwith 40 PACE RADIO LIST, sent post free on receipt

of 4d. in stamps and mention of this advertisement.

Head Office : 10, FITZROY I Showrooms:LTD. SQUARE, LONDON, W.I. 303,EUSTON RD. N.W.1

VALVE RENEWALSWe repair by our patent process ( for which we haveNATIONAL PHYSICAL LABORATORY'S Reportof efficiency)

ALL STANDARD TYPES OF VALVES AT 6/6AND CARRIAGE PAID

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newvalves.

To RETURN IN THREE DAYSOR REFUND YOUR MONEY WITHOUT QUIBBLE.

THE ECLAT MANUFACTURING CO., LTD.Spencer Works, Wimbledon, London, S.W.

775

Standard, Vernier, Doubleand Triple types in allcapacities, each one testedand guaranteed. 1

Prices from 1 /..,

The Only Oneof its kind-The patented features of the Bowyer -Lowe Square Law Condenser make itunique among instruments of the kind.The moving plates are semi -circular, sothat no sagging can take place as a resultof unequally disposed weight.

Its construction reduces minimumcapacity to so minute an amount that thecapacity ratio is the highest in wireless -150 -1 in the .0005.

In addition to simplicity of tuning andcalibration, Bowyer -Lowe Square LawCondensers make your set selective,increase its wavelength range and yieldsignals of astonishing purity and volume,

Order Bowyer -Lowe Condensers by nameand insist on having them in all your sets.

Bowyer -Lowe Tested

Square Law CondensersGood dealers stock them. In case of difficulty orderdirect. Descriptive brochure free for postcard.

BOWYER-LOWE Co., Ltd. LETCHWORTH,


Wireless WeeKlyArticles required :-(a) Revolving switch spindle A

with bush, sprii.g washer, nuts andknob B.

(b) Two coil holders (or three, ifrequired).

(c) Graduated dial with nut incentre.

(d) Some inch ebonite.The coils used should be of even

depth and not more than 4 inchesdiameter; preferably the Gambrell,as these are all one size.

Wishing your valuable paper everysuccess for the future.-Yours faith-fully,

B. SEYMOUR BAILY (Capt.).Plymouth.

APPRECIATION

SIR,-Allow me to express mykeen appreciation of your leadingarticle in Vol. 4, No. 20 issue ofWireless Weekly.

You have indeed given publicityto the thoughts of hundreds of merepractical constructors. Personally,in my own small sphere, I haveseen and handled sets built byamateurs with no theoretical andvery little practical experience, andnaturally the results obtained areanything but encouraging.

About two years ago I began tosearch for really modern technicalmatter, something that could be

successfully applied to and com-bined with practical experience, andI must confess after about sixmonths' wading through compli-cated formula, etc., I gave it up.Then I purchased my first copy ofWireless Weekly.

It is surprising how many sets arebuilt and operated unsuccessfully,with the consequent blame thrownon to the manufacturer of the com-ponents or to the author of the cir-cuits, when it is just that little bitof theory combined with the prac-tical that is needed to turn partialfailure into success.

My friends tell me I am " hotstuff " with wireless, but I tell themit costs me 6d. per week plus asmall addition to the lighting bill.

Your suggestions with reference totechnical instruction are admirable,and carried out in the proper man-ner would no doubt prove highlysuccessful, but I venture to suggestit would need men of the provedability of your own staff to conductlectures, and I would even gofarther than this and suggest thatRadio Press, Ltd., be adopted as anational institution. At all events,I can but add my humble apprecia-tion of the' services rendered to meby Radio Press, Ltd., through thevarious publications emanating fromDevereux Court, and I sincerelyhope success will attend the newhome and ventures of the company,

October 8, 1924:

as I feel sure it will. --Yours faith-fully,

Luton.C. H. WHITE.

THE RADIO CRITIC

SIR,-Your excellent journal is,for the experimenter and home con-structor, a most valuable produc-tion. I feel, however, that it doesnot devote sufficient space to thelistener who is a listener pure andsimple, i.e., to the person who isabsorbingly interested in wireless asa means of entertainment, but hasneither the inclination nor the .timeto dip into its technical intricacies.The .prime concern of this hugebody of enthusiasts is to obtaingood programmes from the B.B.C.,and plenty of them. Now, youpublish many letters from construc-tors of sets, but few from listener -critics? Why is this? Do 'theynot write to you, or do you thinktheir utterances out of place in yourjournal? Until the day comeswhen an enterprising publisherbrings out what we are all eagerlywaiting for, a critical paper de-voted to the interests of listeners,the wireless press would be welladvised, I think, to give more spaceto criticism of programmes, and ofthe general activities of the B.B.C.

-BEWARE of IMITATIONSIMPORTANT NOTICE

to thePUBLIC & TRADE

TYPE C (below panel).Type A (above panel), Template Supplied ... 1/9Type C (below panel), Template Supplied ... 1/6

We, The H.T.C. Electrical Co. Ltd., hereby notify users ofvalve -holders that they should insist upon getting the H.T.C.Valve -Holder, which is not sold without drilling templatebearing the name H.T.C.

BRITISH and FOREIGN Patents are applied for and allsteps necessary for the protection of the public, the trade andthe patentees will be taken as occasion arises.

The design of the H.T.C. Valve holder is both unique andoriginal and are the valve -holders extensively used byMODERN WIRELESS (The Radio Press, Ltd.) in theirpublished circuits.

INSIST upon the ORIGINAL. BEWARE of IMITATIONS.

If your local dealer cannot supply write direct to:

H.T.C. ELECTRICAL CO. LTD.2 & 2a, BOUNDARIES ROAD, BALHAM, S.W.12.

Trade Enquiries trailed. Telephone: Battersea 374

Mr. John Scott - Taggart,F.Inst .P , A .M .1 .E .E , writesin the September issue ofMODERN WIRELESS on" Multi -Stage High -FrequencyAmplification."

" Much can be done with theordinary type of valve, provided asuitable valve holder is used. Quiteapart from other merits, thewidely -spaced contacts on certaintypes of. spec:al valve holders areparticularly suitable for high -frequency work. The ordinaryarrangement where the socket pinsare very close together, the nutsand washers being frequently onlya matter of r/ 16th inch apart, isentirely unsuitable for high -fre-quency, OR, IN FACT, FORANY 'OTHER WORK."

TYPE A (above panel).This model especially appeals tothose who prefer above -panelmounting.

776


October 8, 1924 Wireless WeeklyTo set the ball rolling, I venture todraw attention to the following :-

(r) The listener is the keystone ofthe wireless arch. He pays thepiper and has the right to call thetune.

(2) Every legitimate taste, if heldby a sufficient number of people,should be catered for. It is thebusiness of the B.B.C. to ascertainthose tastes; ours to enlighten them.

(3) A necessary corollary of (2) isthat we will not have what we don'twant for any reason, least of all be-cause some faddist or fanatic in theB.B.C. thinks it good for us. (Thebearings of this observation lie inthe application of it !)

'(4) There is widespread dissatis-faction with recent B.B.C. pro-grammes, times of transmission,etc. We want an outlet for venti-lating this dissatisfaction. Will yougive us space until The RadioCritic arrives to promote and pro-tect our interests?

(5) The alternative programme islong overdue.

I hope you will consider the sug-gestion here made worthy of yourconsideration. I am sure you wouldreceive many interesting letters fromyour readers which would tend tomake your Journal more attractivethan it already is.-Yours faithfully,

P. C. MAYWOOD.

Teddington.

SIMULTANEOUS BROAD-CASTING

SIR,-I should be glad if your in-dependent columns could contain aprotest against the present " S.B."policy, of the B.B.C. In complain-ing to the company one is replied toin round terms (so round that itlooks " circular ") to the effect thatS.B. is generally liked - and is con-fined to artists of world-wide fame.Now the latter statement is capableof proof, and I 'think' the artists inquestion, say, on a play night,"would be the first to deprecate anyidea that their personal fame extendsto the AntipOdes.

Apart from the question of thenature of S.B. programmes (towhich many strongly object), distor-tion and :land -line noise coming ontop of the poisonous brand of Morsewe have in thisdistrict, is enough tocompletely spoil enjoyment.-Yoursfaithfully, .

IvoR P. JONES.Taunton.

ENVELOPE No. 3SIR,-I have recently constructed

the " Simplicity three -valve re-ceiver," and am more than delightedwith it.

Using two valves only (CossorH.F. and Mullard Detector) the fol-lowing stations can be picked upnightly : - Sheffield, Nottingham,

Hull, Leeds and Bradford, and allthe main B.B.C. stations exceptCardiff and London (although I canpick up London when Sheffield Re-lay is not working), Stuttgart,Frankfort, Hamburg, Breslau,School of Posts, Petit Parisien andMadrid, and a German stationworking on about 4ro metres, whichI have not yet managed to identify.

Recently I also picked up Romeon 425 Metres, after io p.m.

Belfast comes in at fair strength,but is badly jammed by Morse.

In daylight, in addition to theabove mentioned relay stations, Bin;rningham and Manchester come inat very good strength, whilst New.castle is comfortably audible. Ontwo occasions I have picked upFrankfort before 7.3o p.m.

All these stations have been heardon three coils (Igranic), viz.: -35and 5o, and 5o and 75, and I haveno doubt that larger coils wouldbring in the higher wavelengthContinental stations.

I have only found it necessary touse three studs of the tuning switch,viz. :-4, and 9, and find thatthe A.T.C. in parallel gives the bestresults.

The total cost of the set, lessvalves, accumulator and H.T. wasless than 4.5, which sum includesR.I. transformer and Igranicrheostats.

My aerial is a standard outdoor

\\,.......,___4oR.p.iS

0

Ask your Local Retailerfor the

MORRIS"(ALL STEEL )

VALVETEMPLATE

No Centre Punch required,no instruments.

Post Free

101/2d.NOTE THE ADDRESS:

J. 0. NICHOL & CO., 46, Lancaster Av., Fennel St., Manchester

YOURS FOR 201-,Send 201- to -day, together withyour order for the "Tonyphone,"and this wonderful set, whichreceives all B.B.C. stations, will bedelivered complete, including allaccessories. You pay a further £1each month afterwards. The totalcost is only £15 gs., or if youprefer, £14 5s. cash."Tonyphone" Super Two -ValvesComplete with Accumulator, H.T.Battery, Aerial, x pair 4,000 ohmsHeadphones, and two Valves-oneHigh Frequency and one Detector.All Royalties paid. Send to -dayand enjoy broadcasting NOW.

BRITISH ENGINEERING PRODUCTS CO ,Wireless Dept.), WINDSOR HOUSE, VICTORIA ST., LONDON, S.W.1

8.8.A.

GENE0 1 NES400P10.--"°

Sensitive to '00000000011of an anmazie. Matchedtone earpieces. Specialsound chambers. Weight7 ozs.

Ask your dealer about them.

GENERAL RADIO COMPANY]

Radio House, 235, Regent St., London, W.I.Telephone: Mayfair 7152. Telegrams : Algenrad, London."

ISWAITING

FOR

YOU

Write for FREE LISTS of (a) Compete Sets, Home ConstructionSets and Unit Sets; (6) H.F. Valve Couplings and. Reaction; orsend 3d. stamps to include also Complete Catalogue of Accessories -

and Components for every Wireless purpose.VISIT STAND No. 81, ROYAL ALBERT HALL.

RADIAX, LTD., 50, Radio House, Percy Street,Tottenham Court Road, London, W.1.

777


Wireless Weeklyone, barely 3o feet high at itshighest point, and running verynearly due north and south.

Please allow me to offer you mycongratulations. May I also con-gratulate you on the Envelope Sys-tem as a whole.-Yours faithfully,

G. M. EADON.Dore, near Sheffield.

MORSE TRANSMISSIONSSia,-Reference your article in the

double number of Modern Wireless,by Mr. A. R. Burrows.

I am of the opinion that thesetransmissions would be of invaluableaid to many experimenters shouldthey be of a slow and progressivenature-remembering always theArmy rule : to march at a pacesuitable for your slowest men.

The transmissions would be bestafter the broadcasting programme,say for 20 minutes, with the excep-tion of the late nights devoted tothe Savoy dance bands.

Experimenters surely have at leastone valve, and I think this wouldbring in almost any B.B.C. stationon Morse, so that the one broad-casting station need not have thewhole of these transmissions. 1 amthinking of the engineers and thelate hours that this would entail,and I think the work could bedivided up, say, between several sta-tions, without fear that the Morse

practice would not be heard by any.One thing is clear, that the

transmission must be dogmaticallyslow to start with, and should beprogressively slow enough so thatnone loose interest, Those that canread eighteen words a minute canfind numerous stations at all hoursof the day and night, so it is not forthem that I presume your schemewill be intended.

Others join with me in askingyour valuable publications to pushthis scheme, and express our in-debtedness to Mr. Burrows on suchan enterprise.-Yours faithfully,

R. L. THOMPSON.Whittlesford.

ENVELOPE No. 4

SIR,-About three weeks ago I

purchased the envelope containingparticulars regarding the " All Con-cert Receiver," and wish to giveyou my results.

I am situated about 21 miles fromthe Newcastle station and in a directline south. My aerial is a singlestrand, and just on a level withthe tops of some very high trees.

I was rather disappointed withthe results at first, but am now get-ting excellent ones.

I am now using B.T.H. B4valves in all the stages, and have hadso per cent. better results than when

2BD 13

5SC ... Good

Le Petit ParisienVox Haus ?

(woman an-nouncer).

HamburgBreslau

October 8, 1924

using a Cossor for the H.F. and aMullard or Marconi for the detector.

Without any wave -trap, I am ableto tune in 2BD. at excellent loud-speaker strength and with veryslight interference from 5N0. Theonly other set which I can do thison is the four -circuit Cockaday.

When using bright emitter valvesI could not get sNO up to strongL.S. strength. but now I have tode -tune, as it is much too, Ibud 'evenwith the 'filament just glowing.

I have included a switch for re-versing the reaction coil, and I findit very useful.

Radio -Paris .. Loud Speaker.5XX ... Good These are all5NO ... Excellent l the B.B.C. sta-

tions which Ihave botheredwith so far.

Loud in phones.Fair L S.

GoodFair

I have had many more foreignstations than these, but have notheard their call signs.

Trusting these particulars may beof interest to you, I remain,-Yoursfaithfully,

Durham.HENRY R. MYERS.

NoRenewals

Necessary.

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FINSTON FEATURES CAPACITIESReliability of Capacity. Finestgrade Mica Dialectric. Highestpossible quality Copper Foil.Adapted for Terminal or solderedconnections.

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.0001 to .001 Price 1/3 each.

.002 to .006 Price 2/- each.

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Wall

2475.

TradeTerms

onpplication

B=7777;

778

Handsome nickel dial.One hole fixing.Phosphor Bronze contact arm.

Winding cannot be damaged byordinary use.Size. ins. diameter, bin. high.From all Wireless Stores or direct from

The Bedford E!ectrlcal & Radio Co., Ltd.,kikElectrical Engineers & Manniccturers.

22, Campbell Road, Bedford.

2/66 ohms

15 ohms30 ohms

Established26 Years.

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The "Bretwood" Grid Leaktunes a carrier wave from thesilent point up. The "Bretwooris recognised by highest experts

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Barclays 12



Information Depaftment

SUPPLIED BY RADIO PRESS

F.W.B. (LIVERPOOL) asks what is meantby hand capacity effects and how can they beavoided ?If the hand of the operator is brought near to acondenser, inductance coil, or any other metallicpart of the receiving set connected to a point ofmore or less high potential, the capacity to earthor merely the self capacity of the operator's bodywill alter the tuning of the apparatus. This effectis particularly noticeable in high -frequency am-plifiers, and in the reception of short-wavesignals, particularly those from continuous wavestations. The effect may be minimised, if notentirely prevented, by screening the variablecondenser by means of a thin metal plate securedto the under side of the panel and connected bymeans of a wire to the earth terminal. Theinsulating extension handles now on the market

SERVICE DEPT., LTD.

also minimise this hand -capacity effect by makingit possible to operate the condensers from areasonable distance. It is mostly in the adjust-ment of condensers that the trouble is experi-enced, as they are usually used for the final finetuning.

J.V.H. (CROUCH END) asks what is thedifference between primary and secondarybatteries ?A primary battery is one in which the chemicalchange which produces the electric current is noteasily " reversible," that is, the substances whichresult from the change cannot be re -convertedinto their original form by passing a chargingcurrent through the cell in reverse direction.Hence, when all the active substance has reactedwith the exciting agent, the cell is " run down "

Reversible c/E-5)47-

VALVEHOLDER (NI? P

The Universal Valve Holder.One Hole fixing and will fit front or

back of vertical or horizontal panels.Lowest Capacity andHIGHEST INSULATION OBTAINABLE

II roar dealer Cannot .b)lo we will seal

post /re= if goo mention his nnne end address.

1/3PATENT

ARM FOR,

ATHOL ENGINEERING COMPANY,CORNET ST., HIGHER BROUGHTON, MANCHESTER. ! SEND P.C.

I FOR LIST. ILIBERAL TRADE TERMS. 7horte : 469 H.B. I

RADIO INQUIRIESWe wait to send you whatever information oradvice you may require. Write us fully andyour letter will receive immediate and indivi-dual attention. You may depend on gettinga helpful and fully detailed reply.With your query please enclose P.O. for 2/6to cover cost of work involved, but if yourequire complicated diagrams or calculations,4/6 is necessary.

RADIO INQUIRIES,Imperial Buildings, Oxford Road, Manchester.

We're Here to Hdp.

779

Fa" LICHTNINCNo matter how fierce the storm, there is nobetter protection for house, home and wirelessset than an aerial, provided it is fitted with a

PRESSLAND SAFETY LEAD-INTo Aerial

To Earth

This littleaccessorystands forimmunityfrom Ventilationdanger.Fit it.

To Set

-the only scientific method of dealingwith tie lightning problem-externallyfrom the house. There is no leakagewith the Presskuld Lead-in, it gives astraight path from aerial to earth and isa premiumless policy against damage.

Made in usual lead-in sizes.Length 6" - - 3/.Length 9" - - 3/3Length 12" - 3/6

Send for free pamphlet or ask yoardealer.

PRESSLAND ELECTRICSUPPLIES LIMITED

HAMPTON . ON - THAMES'Phone : Maesey 22

TRADE ENQUIRIES INVITED

Co.


Wireless WeeKlyand must be discarded. A secondary battery,on the contrary, operates by virtue of a chemicalchange which can be reversed by passing a cur-rent through it in the opposite direction to thatgiven out by the battery. The materials com-posing the cell are thereby restored to theiroriginal form, and will once more react and giveout a current from the terminals of the battery.The battery can therefore be re -charged when ithas run down, and the cycle of changes can berepeated almost indefinitely. Secondary batteries,of course, are commonly known as accumulators,though the name is something of a misnomer.

N.A.G. (LEEDS) desires to know the besttype of outdoor aerial where space is strictlylimited ?A single -wire aerial of restricted length andheight will have a short natural wavelength, andwill not intercept and collect much energy frompassing electro-magnetic waves. If the dimen-sions are particuarly small, a large amount ofinductance (in the tuning coil or coils of' thereceiving set) will have to be added in order totune it to the desired wavelength, and the resist-ance of these turns will cause considerable damp-ing. Under the circumstances, the best thingto do is to increase the number of wires in theaerial, thus increasing the capacity and conse-quently its natural wavelength. The disadvan-tages of a large -capacity aerial have already been

October 8, 1924

mentioned k answer to an earlier question. Agood effect can be obtained by the use of spreaders,say 7 ft. 6 ins. long, carrying four wires spaced2 ft. 6 ins, apart. The down -lead should also beof four wires joined together at the point wherethey enter the receiving room.

W.E.M. (WOODFORD) wishes to knowwhether the natural wavelength of an aerialaffects reception and transmission ?Certainly. If the natural wavelength of an aerialis 400 metres, ,and it is desired to receive waves3oo metres in length, the natural wavelength hasto be artificially reduced by the use of a smallseries condenser, which appreciably lessens theefficiency. On the other hand, if the naturalwavelength of an aerial is about 200 metres, andit is desired to receive waves 3,000 metres inlength, a very large amount of inductance has tobe added in series with the aerial. The resis-tance of the turns of wire forming the inductanceintroduces what is 'known as damping and theefficiency is again low. It will be understood, ofcourse, that in order to operate the receivingapparatus, there must be a certain number ofturns of the tuning inductance in circuit. Inpractice the best possible results are obtainedwhen the natural wavelength of the aerial is fromtwo=thirds to three-quarters the wavelength whichit is desired to transmit or receive. '

"Perfect Reception "GUARANTEED

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HUNDREDS OF TESTIMONIALS.One User writes:-"I have replaced a 7/22 wire

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The Amplifytone Aerial is made from the highestgrade Electrolytic Silicon Bronze (Pao feet) (21 timesstronger than copper) in tapeform-it won't corrode. BEWARE OFPacked in boxes, including I MIT AT IONS,patent lead-in clips and insu- which only corrodelators. Ask your Dealers, or and break. Look fcr6/6 post free from AMPLIFYTONE

on tho box.

UNITED MANUFACTURERS & AGENCY, LTD.,45, Horseferry Rd., London, S.W.l.


WIRELESS WEEKLY ADVERTISEMENTS OCTOBER 8TH,

Every Experimenter needs this Book !

THE most absorbing Book on the Valve yet large circle of Radio enthusiasts who are verypublished. The author, John Scott -Taggart, keen but who are not too technically minded.

F.Inst.P.,A.M I.E.E., Editor of From1I Taking the form of questions

1----Fm all BooksellersPublished by Radio Press, Ltd., iM odern Wireless, has purposely I Bush House, Strand, W.C.2. and answers, it provides an

iI

set out to produce a book 1 2/6 I ideal source of information

which will appeal to the very I or 2/8 post free. I for every valve user.I-- - el.. .m... air 1. IN If

FtuflPY


4 WIRELESS WEEKLY ADVERTISEMENTS OCTOBER 8TH, 1924.

3 -VALVE 19PRTALEWavelength rangeO 200-

B4,000 SETmetres d

C

2 -VALVE PORTABLE SET

:15 : 0

: 18 : 6Wavelength range 200-4,000 metres £14

4 -VALVE LYRIANSET

Complete with L.S.D.E. Valves and

Batteries.

£44 : 3 : 6Without accessories

£37 : 18 : 0

LYRIANETTE2 -Valve complete

£22 : 5 : 03 -Valve Complete

£28 : 5 : 0

4 -VALVE PRTABLE SETWavelength range

O200- 4,000 metres. £26

Striding Aheadin 1924

The keenness that has been shown for the achieve-ment of perfect radio apparatus is for thoroughtechnical engineering rather than for commercialgain with those firms who have advanced to theforefront of the public popularity.

R.I. stands to-day for the very best wireless pro-ductions on the market. Prices may appear higher,but all R.I. purchasers know that these prices covera skilled workmanship superior to multitudes ofcheaper competitors.

Thousands of the New R.I. Transformers havealready been purchased and their owners areenthusiastic over the wonderful difference they make.You can see a giant Sectional Model of theNEW R.I. at our showrooms.You will also see the other wonderful R.I.1924 creations. The New R.I. Lyrian and Lyrian-ette are the only complete loudspeaker broadcastingreceivers available at a popular price.

R.I. Multi Valve Sets for all wavelengths are thehighest standard wireless receivers that are made.Each component gives maximum efficiency in theseneat, strong, portable valve sets, producing as aresult unique radio reception.

Ask for the New R.I. Catalogue.Throphone agent 6214-5-6 1-&1grarns."Instradio LondoR"

Radio IRstrumeRts Ltd12 Hvde .51raat, OxFord Street.- W I.

Printed for the Proprietors, RADIO PRESS, LTD., Bush House. Aldwych, W.C.2, by THE AVENUE PRESS (L. Upcott Gill & Son. Ltd.), 55-57, DruryLane, London, W.C.2. Published on Wednesday of each week at 3, Bolt Court, Fleet Street, London, E.C.4. Address for Subscriptions and EditorialCommunications :-Brsh House, Aldwych, London, W.C.2 Advertisement Managers :-BARCLA1S ADVERTISING. LTD., Sentinel House, SouthamptonRow, W.C.1. Registered as a newspaper and for transmission by Canadian Magazine Post. Subscription rates :-32/6 per annum, 16/3 for sixglont118, post free. Sole Agents for Australasia :--GORDON & GOTCH, (Australasia), LTD. For Canada :-IMPthIAL NEWS. LTD For South Africa : -

(AMMO. NEWS AGENCY. LTD. For Japan :-SALE & FRAZAR, I )D


Documents

Post Office Hypocrisy - worldradiohistory.com · Vol. 4, No. 23 OCTOBER 8, 1924. Price 6d. net. Post Office Hypocrisy GENERAL indignation has been aroused by the growing ten-dency