INTERNATIONAL JULY 1980

Area!robotYou canBuild!

lectronics in the StudioCMOS 555 PhototimerNovel AF Meter

WHAT?YOUR PRESENT TESTINGCAPABILITY...

CAN'TTEST DIGITAL AND ANALOG CIRCUITRYWITH EQUAL EASE?

CAN'TTEST DELICATE IC'S LIKE MOS, CMOS,PROMS, RAMS, EROMS...IN CIRCUIT?

CAN'TTEST ELECTROLYTICS... ISOLATEPROBLEMS TO A GATE OR JUNCTION?

...IN CIRCUIT.... WITH NO CIRCUIT POWER REQUIRED!

HUINIL-Ln1j'IM[f%.0[1(< NCANI1

IN CIRCUIT TESTING OF DIODES, TRANSISTORS, FET'SJ-FET'S, OP AMPS, ELECTROLYTICS, BIPOLARS,UNIJUNCTIONS, DARLINGTONS, IC'S OF ALL TYPES

EXCLUSIVE CANADIAN DISTRIBUTOR

CYPRUS PRODUCTS INC.7117 Tisdall St., Vancouver, B.C. V6P 3N2 Tel.: (604) 327.8814

Circle No. 14 on Reader Service Card.

ARKON Electronics...your place for sizzling summer buys!

PI011An S-100 system card, wired and tested that willoutperform the mass market systems in versatil-ity, price and speed. It has all the CPU (80801disc control 117711 and 10 (8255) needed for adisc based CPM system. Interfacing to all com-mon 8" and 51/4" drives. (Shugart, Memorex,BASF, Siemens, Wang). Also features EIA RS-232 port 1110 to 9600 baud), fully vecored inter-rupts (TMS5501), on board digital data separ-ator, 2K bytes eprom, 24 fully handshaked 10lines, dual mapped 10, cassette interface onboard, fully buffered $495.00

ASCII KEYBOARD KIT60 key complete ASCII character set. Fully buf-ferred output for TTL/ DTL/ MOS logic. Capslock for upper case alpha characters. Uses a KR2376 ST encoder IC. Uses 100 ma at +5 to 30volts. Parity invertable. Data Invertable. Repeatkey.Complete kit of all parts 599.95Power supply kit 7.95

D SYSTEMSA fully compatible line of S-100 system cards.Full data and specs on all kits sent free onrequest.EXPANDORAM 1 48K $775

OK $299 64K $90016K $399 S-100 BOARD KITS32K 5499 SBC-10048K $599 SBC-20064K $650 1-80 Starter Kit

MPB-100EXPANDORAM II ExpandoProm

OK $399 VDB 802416K $525 Versafloppy I32K $650 Versafloppy 11

$375$435$4505325$225$475$325$450

Efficient test equipment...4 outstanding "Hitachi" scopes.

Also ammeters,volt meters, multi -meters.

RE6416VIDEO TERMINAL

Display: 16 lines of 64 charactersFormat: 5x7 Dot matrixVert sync: 60 Hz Xtal controlledHor sync: 15,840 Hz Xtal controlledVideo o/p: lv Peak to peak10: Parallel, 20 Ma, RS232Data rate: 110 to 9600 baudPower: 5 VDC 1 A, +12 DC.1A

RE6416: Kit of all parts $169.95RE6416: Lower case option $ 16.95RE6416: 5 V pow. sup. option $ 16.95RE6416: ± 12 V pw. supply $ 16.95

S-100 MOTHER BOARDExclusively ARKON's...the A6S100 6 slotmother board, designed for the system builderusing modern boards where few slots are re-quired. Provision for semi -active termination.A6S100 519.95S-100 edge connector $ 5.95

Fun, games, tests, helpers andmore with a galas y of ET! projects!

JANA KITSAuto headlight reminder 3.9512 volt high power flasher $ 7.300-20 volt 1 ampere power supply $25.65Single channel colour organ, 300W $ 6.65Electronic sirenShimmer light kit

4.957.65

Xenon strobe kit $15.803 CH. colour organ, 300W, PCB incl $18.9530watt soldering iron kit $ 8.25PCB's available at extra cost.

Finest quality for you from"Hammond ".,.transformers,power supplies, power bars,

cabinetsA rainbow of electrolytic capacitors

types in endless supply.

ASCII ENCODEDKEYBOARDRCA VP -601 keyboard with 58 key typewriterformat for alphanumeric entry. Modern flexiblemembrane key switches offer a contact life ratedat greeted than 5 million operations. A fingerpositioning overlay combined with light positiveactivation key pressure gives good operator"feel" and an on -board tone generator givesaural key press feedback. The keyboard operatesfrom a single 5 volt DC power supply and thebuffered output is TTL compatible. Completewith case 899,00

Build creatively with "VectorGraphics "perforated breadboard!

MULLEN EXTENDERBOARD TB -4

The best extender board made, complete with adigital probe for in circuit checkout and tracingfor S-100 buss $69.00

SOFTWAREFor 8080 8" disc`CPM 1.4 $130.00.CPM 2.0 $190.00.SID debugger $ 95.00`MAC assembler $115.00r TEX text editor 95.00DES despooler 65.00

`CPM manual set 30.00copyrigh, ogitai RESed101

e FORTH80 I ortran for 8080, 280, 8085 99,00

FORT//80 manuals $ 20.00awynght 4,411E180,mo

C -BASIC II $175.00For OSI, CI, on cassetteStar fighter 8.95Alien invaders $ 8.95Seawolfe $ 8.95Tank for two S 7.95Bomber 8.95Barrierball 7.95Breakthru S 7.95Fighter pilot S 5.95Killerbot 5.95Lunar Lander $ 4.95Concentration $ 5.95Chess for OSI $24.95Time Trek $12.95Backgammon $12.95

Data SheetsGraphic instructions $ 4.00RS 232 for the CI P and superboard $ 3.95Joystick instruction and plans $ 3.95Reverse video for the ClP $ 3.95G.T. conversion 1.00Saving dita on tape $ 4.00

UtilitiesClP cursor control $12.95Renumberer S 7 95Autoloader S 7.95

Ask for our giant list of software available forApplemjPeto,TRS-80,mby Programma Int'l,Instant Software, Creative Compuulg, Haydenand Sottape.

ARKON GRAB BAGAssorted good parts at an unbeatable bulk price...perfect for the work bench or service area.GB -100 100 disc ceramics $2.00GB -101 60 Mylars $4.00GB -10260 Electrolytics $4.00GB -10340 Tantalums $5.00GB -10420 Ceramic trimmers $7.00GB -11350 Miniature trimpots $5.00GB -117 200 Asstd 1/2 w res. $3.00GB -118 100 Asstd 1-2w res. $3.00GB -120 25 Asstd switches $5.00GB 139 5 Lbs hardware $4.95GB -1605 Lbs circuit boards $4.95GB -146 100 Grommets $3.95GB -147 100 Inductors, coils $3.95GB -1502 Lbs potentiometers $1.00

ARKON KITAll ARKON kits are complete with PCB.Decision Maker Kit 8 4.95Transistor IW Amp Kit 8.95555 IC Timer Kit 8 3.95555 Code Oscillator Kit 3.95RS 232 to TTL Converter Kit 9.95BN-9 (LM 380) Audio Amp Kit S 5.95TRS 80, Apple 11 16K Upgrade Kit $69.95VD -1 Video Modulator Kit $ 8.95TD 1567 Tone Decoder Kit $ 6.95FM Wireless Mike Kit $ 3.95FM -2 Wireless Mike w. Preamp Kit $ 5.95Music Light Kr $12.95LED Blinky Kit 2.95Mad Blaster Noise Generator 4.95UT -1 Universal Timer Board 3.95MA 1003 Car Clock Module $19.95MA 1023 Car Clock Module $19.95MA -1008 (State 12 or 24 Hr.l $12.9512V Clock Transformer $ 4.95LCD Alarm Clock Module $29.95ETI Sound Generator Kit $44.95

A parade of speakers andenclosures, telephones, clock

modules, L.C.D. quartz watches.

OHIO SCIENTIFICSUPERBOARD11-4K Computer -

on a -board $415.00CHALLENGER IP Superbaard 8K

in a box & P.S. $575.00SUPERBOARD 8K Memory expansion

181 chips S60.0CSUPERBOARD memory expansion

PCB 124K1. data ';50.00CHALLENGER 4P - 8K with sound.

colour, 10 $1,045.00CHALLENGER 4PMF 4P with

minIfloppy 10 .$2,559.00

TX -80 DOT MATRIXPRINTER

tractor feed printer featuring 100 million char-acter head life and printing speed of 150 charac-ters per second using 96 ASCII characters. Theplug fits any centronics type interface makingthis printer compatible with all types of mini andmicro computers thus giving a wide range ofoperations. Standard paper is available at Arkonand elsewhere. Various interfaces provided asoptions including EIA RS -232C. This providesoutstanding equipment design! It provides thebusiness and home computer markets with anexceptionally inexpensive, sturdily built andhighly reliable dot printer.TX80 with parallel interface $995.00

Replacement ribbons 4.008210 PET cable $ 40.008220 TRS-80 cable expansion 57.008221 TRS-80 cable bus 40.008230 APPLE II cable $ 40.008110 PET 2001 interface board 83.008120 TRS-80 interface board $ 70.008130 APPLE II interface board $105.008140 RS232 interface board $ 95.008160 IEEE interface board $150.00

Our purchasing powerproduces brand -namequality at no -name prices...

/Th

electronics ltd

IC SOCKET SPECIALS

20% offfor ordersof 20 piecesor moreMix or match.

WirePins Standard Amp Wrap

8 $ .15 $ .2514 S .25 S .3516 5 .25 9 .4518 $ 35 5 .6020 $ .35 5 .7524 S .40 S .8028 8 .45 S .8540 5 .65 .95

$ .65$ .95$1.00$1.25$1.50$1.6051.80$3.00

ISKETTE8" Control Data or Wabash $7.958' ' Dysan $8.9553/4" Control Data or Dysan $7.5010% off for orders of 10 or more. Attractivelyboxed.

A collection of trim pots ranging invalue from 100 ohms to 1 meg.

35' each, And an array of multiturnprecision pots.

Roll out the woe...electrical, speaker,telephone and hook up wire, extension

cords, ribbon and coaxial cable.

NTEGRATED CIRCUITLINEAR 4582 82.15

4584 8.204585 91.5074008 .7574015 $ 60740565 $1.50740922 99.95

307 75308 3;51.00311 65224 51.50324 Si 10339 51.00358 5 85377 $400380 s2.10

4011401240134015401640174018401940204021402200234024

382 5180 4025555 60 40267555 82 00 4027556 5 95 4028565 51.60 4029566 $1 75 4030567 51 80 4033709 5 45 4034723 5 70 4040733 51 75 4042.739 SI 40741 $ 65747 851312 82 501314 $2 501315 52 501436 $2 501458 $ 751488 SI 951489 S1.501496 51.501889 52 502206 57.502567 53.003046

$ .709 .609 .7561.65

.6062.0081.6081.6051.5041.5081.805 50

1 _42.00 .51.5050

51 90$ 9551 7551 60

5052 1554 2552 1551 7052 50

4046 51.754049 504050 51 .304052 51 804053 61.500060 52.504063 52.004066 $I 504068 5 600069 S 504070 S 504071 5 504072 509073 504075 504076 $ 804077 5 504078 604081 5 504082 5 504085 SI 254086 SI 954089 53 504093 51 004094 52 504501 53 254502 $2 104508 83 504510 62 004511 52 004512 $1 604515 65 504516 51 454578 52 004519 SI 004520 52 004522 6215

CMOS 4526 52 504000 5 60 4528 51 654001 5 50 4531 SI 904002 5 50 4532 53.504006 SI 50 4543 52 254007 5 20 4555 51254009 SI 20 4572 5 65

3140 52 503302 $ 953401 s 953900 51 253914 55 953915 55 954136 91.6013741 5 65TL071 S 8011072 SI 75T1074 62 75T1080 S 7571081 5 8011082 Si 5511084 52 50TL489 52 9570490 53 9550C16 50:526 51 204N30 SI 504533 $1 454N37 51 65

TTL74007402740374047405740674087410741674207427743074327433743774407441744274477448745174547473747474757476748374847485749074917492749374957410774121741227412374125741417414574151741537415474157741617416274163741647416570175 .

7017674190701917419274193741947436574367

.5060Al

200605083308o48

1 10

so90

Ea75

1 101 151401 75I 65

656575

1 40

6075

1 801 501 40

5070

885

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I 008560

1 10105I 15

1 00I 75

9575

1 65I 10I 60I 751 251%I 75I 45

951 401601 20.95

1 70I 401 10

REGULATOR SPECIALS7805 + 5v lA .....51.65 7905 -5v 1A $1.957808 +8v lA $1.40 7915 -15v lA $2.007815 4- 15v lA ....$1.50 79L05 -5v .1A.. 51.507824 + 24v lA ... $1.50 79L12 -12v .1A _51.5078L05 + 5v .1A...5 .65 79MG -adj .54 82.0078L12 + 12v IA .$ .65 78GU -adj 1A $2.0078MG + adj SA..52.00 78H05 + 5v 5A 56.00

A supermarket of books andmagazines features fabulous

electronic knowledge.

MEMORY SPECIAL4116 - 16K 300NS TI dynamic memory 9.25

8 for 572.00- 200NS $12.95

21L14 - 4K 450NS low power static ram 5 7.952114 - 4K 200NS static memory $10.952102 - 1K 450NS static memory 1.25

- 35ONS 1,35

COMPUTER POWER SUPPLYAn astounding value. Fully regulated and crow -barred with heat sink and fan. Gives 5V at 10Aplus -5V at 2A plus 12V at 5A plus -12V at 2A.Each voltage separate and floating. Very com-pact cubic design, standard parts 16"x10"x7"110/220 VAC 60/50 Hz. $45.00 plus $10.00freight.

"Elektor"Magazines,Canadian premier issues 30, 31, 32.Unbeatable price...A113 for $2.00.

COMPUTER FANFOLDPAPER CD

Single Double Triple Quad12850 (1200 (950 1700

sheets) sheets) sheets) sheets)

8 1/2 " x11" $30.00 $33.00 $35.00 $38.009 1/2"x11"peer $40.00 - -15"x11" $45.00 $49.00 $56.00 $60.00

Labels - one up (price per 100013 'O"x15/16"...97.00 4"x2-7/16"...$20.00

Send certned cheque, mcney order, Chargex, Master Charge . include expirydate, carc number and signature. We process C.O.D.'s for Canpar or PostOffice. Minimum order $10.00. Add 5% (minimum $2.00) for shipping andhandling. Any excess refunded. Ontario residents add 7% sales tax. All pricessubject to change.

409 Queen Street West,Toronto, Ontario, M5V 2A5. 868-1315

Editorial and Advertising OfficesUnit 6, 25 Overlea Boulevard,

Toronto, Ontario, M4H 1 B1Telephone (416) 423-3262

Publisher and EditorHALVOR W.MOORSHEAD

Assistant EditorJOHN VAN LIERDE

Advertising ManagerMARK CZERWINSKI

Advertising ServicesNANCY ALLEN

Advertising RepresentativesJIM O'BRIEN

Eastern Canada JEAN SEGUIN &ASSOCIATES INC. 601 Cote Vertu,

St. Laurent, Quebec H4L 1X8.Telephone (514) 748-6561.

Subscription DepartmentBEBE LALL

Accounts DepartmentSENGA HARRISON

ProductionSARAH-JANE NEWMAN

CHERYL MAYContributing Editors

WALLACE PARSONS (Audio)BILL JOHNSON (Amateur Radio)

JOHN GARNER (Shortwave Listening)STEVE RIMMER (Video)

DICK CARTWRIGHT (Servicing)DAVID VAN IHINGER (Servicing)

INTERNATIONAL EDITIONSElectronics Today International,

145 Charing Cross Road,London WC2H OEE, UK

Electronics Today International,Ryrie House, 15 Boundary St.,

Rushcutters Bay, Sydney, Australia.Elrad

Kommanditgesellschaft, BissendorferStrasse 8, 3000 Hannover 61 Germany.

Electronica Top InternationalPost Bus 93 Bilthoven, Holland.

Published by:Electronics Today International (Canada) Ltd

Printed by:RBW Inc., Owen Sound, Ontario

Newsstand Distribution:Master Media, Oakville, Ontario

SUBSCRIPTIONS$14 (one year), $26 (two years). For US add

$3/yr., other countries $5/yr. Pleasespecify if subscription is new or renewal.

BACK ISSUES AND PHOTOCOPIESPrevious issues of ETI-Canada are availabledirect from our offices for $3 each; please

specify Issue by month, not by featureyou require. 1977 issues available:Feb,

May, July, Nov. 1978 issues notavailable: Jan, Feb and April

We can supply photocopies of any articlepublished In ETI-Canada for which the charge

is $2 per article, regardless of length. Pleasespecify both Issue and article.

Postal Information:Second Class Mall Registration No. 3955.

Mailing address for subscription orders, unde-liverable copies, and change of address notices

is: Electronics Today, Unit 6, 25 OverleaBlvd., Toronto, Ontario, Canada M4H 1B1.

YINTERNATIONAL JULY 1980

FEATURESCMOS 555 11

Our circuit feature this month dealswith the CMOS version of the popular555 Timing IC. Sixteen applicationcircuits are described by Tim Orr.

Capacitors 24There's more to a capacitor than itsvalue in Farads. Rick Maybury looksat the extraordinary variety availableand explains the virtues and short-comings of the different types.

Electronics In The Studio 31The increasing demands of recordbuyers has led today's recordingstudios to become highly complexelectronic centres. Tim Orr takesreaders on a tour of a highly complexmodern studio.

The Tesla Controversy 42Nikola Tesla was a genius and some-thing of a showman. There remain,however, people who claim that Teslamade a discovery of such significancethat it was suppressed.

Win an $895. 'scope 41To celebrate the 10th birthday ofOmnitronix we have cooperated withthem to produce a contest which willresult in one lucky (and skilful) readerwinning a magnificent Leader Oscilli-scope.

PROJECTSHEBOT 16

Despite its simple appearance and cir-cuitry, our robot is considerably moresophisticated than most other designspublished to date and incorporatesan ingenious and unusually priorityencoding system.

Vol. 4 No. 7

CMOS 555 Application Circuits, p.11

-All about Capacitors, p.24

Recording Studio Techniques, p.31

Win this 'Scope, p.41

Cover Photo: Taking thisMonth's cover was quite a

Procedure. The 'smoke' effectwas produced by pouring

boiling water over dry ice and'pouring' the condensation

down a slope. Thanks are dueto Martin Craig of the Toy

Shop, 62 Cumberland Street,Toronto, for the loan of

Robots.

ISSN 0703-8984

Build your own Robot, p.16

Automate your Enlarger, p.46

Analogue Frequency Meter, p.50

Keep in Rhythm, p.58

Photographic Timer 46A timer with two fully variable rangescovering 0.9 seconds to 100 secondswith a relay to control an enlarger onand off.

Analogue Frequency Meter 50An inexpensive item of test gear usinga neat and unusual circuit. Only twoICs are used to give an easily calibratedlinear scale.

Accentuated Beat Metronome . . . .58Not just a 'tick -tick' version but onewhich can give 2-4, 3-4, 4-4 and 6-8time at any reasonable speed; the toneof the non -accentuated beats can alsobe selected.

COLUMNSService News 23David Van IhingerAudio Today 39Wally ParsonsFun of Electronics 45Paul GeigerQRM 49Bill JohnsonWhat's On 53Steve RimmerTeachers' Topics 56Ian SinclairShort Wave World 66John GarnerTech -Tips 64

NEWS /INFONews

Specials

7

9

ETI Book Service 10, 15

Babani Books 28, 66Next Month's ETI 30

Subscriptions 44Reader Service Cards 44Binders 57

ADVERTISERS' INDEX

Active Component Sales Corp

Alberta Audio

A P Products

Arkon Electronics

Atlas Electronics

Audiovision

Batteries Included

. . .72

41

36, 37

3

66, 69

69

41

B.C.S. Electronics 22,41

Bryan Electronics 57

Classif ed 70

Cyprus Products 2

D.C.B. Electronics 69

Edukit Limited 6

Len Finkler Limited 35, 38, 65

Metermaster 8

McGraw-Hill 29

Orion Electronics 67

Portlab 69

Royal View Electronics 69

H. Rogers Electronic Instruments . .66

COPY R IC HTAll material is subject to worldwide copyright protection. AllPCB patterns are copyright and no company can sell boards toour desigr without our permission.

LIABILITYWhilst every effort has been made to ensure that allconstructional projects referred to In this magazine will operateas indicated effsciently and properly and that all necessarycomponents to manufacture the same are available, noresponsibility wnatsoever Is accepted in respect of the failurefor any reason at all of the protect to operate efficiently or atall whether due to any fault In design or otherwise and noresponsibility Is accepted for the failure to obtain componentParts in respect at any such protect. Further no responsibilitYIs accepted in respect of any injury or damage caused by anyfault In trse design 01 any such project as aforesaid.

EDITORIAL QUERIESWritten queries can only be answered when accompanied Cy aselfraddressed, stamped envelope. These must relate to recentarticles and not Involve the staff in any research. Mark suchletters ETI-Query. We cannot answer telephone queries.

BINDERS.,For ETI are ava,lable for 56.75 including postage and handling.Ontario residents acid 7% PST.

SELL ET!ETI Is available for resale by component stores. We can offer agood discount and quite a big bonus, the chances arecustomers buying the magazine will come back to you tobuy their components. Readers having trouble In buying ETIcould ask their component store manager to stock themagazine.

COMPONENT NOTATION AND UNITSWe normally specify components using an internationalstandard. Many readers will be unfamiliar with this but it'ssimple, lees likely to lead to error and will be widely usedeverywhere sooner or later. ETI has opted for sooner!Firstly decimal, points are dropped and substituted with the

multiplier, thus 4.7uF Is written 4u7. Capacitors also use themultiplier nano (ore nanofarad is 1000pF). Thus 0.luF Is160n, 5630pF Is 5n6. Other examples are 5.6pF.5p6,0.5pResistor; are treated similarly: 1.8M onms is 1M8, 5614 ohms

is the same, 4.7k ohms Is 467, 100 ohms is 100R and 5.6 ohmsis 5R6.

PCB SUPPLIERSThe magazine does not supply PCBs but these are availablefrom the following companies. Not all companies supply allboards. Contact these companies direct for orderinginformation.B&R Electronics, P.O. Box 6326P, Hamilton, Ontario, L9C6L9Spectrum Electronics. Box 4166. Stn .0., Hamilton, Ontario,L8V 4L5Wentworth Electronics, A.R. No.1. VVaterdown, Ontario LOR2H0Danocintns Inc. P.O. Box 261, Westland, MI 48185, USA.Exceltrorlx Inc., 319 College St., Toronto, Ontario, MST 152Arkon Electronics Ltd., 409 Queen St. W., Toronto, Ontario,M5V 2A1.

AnnoPPci rig At14-I.

STROBE LITE KIT

Fantastic for special effects. Variable speed Xenon flashgives you a "STILL MOTION" effect. A real attention getter.

Model if EK8OSLO01 PRICE: $21.95

16 CHANNEL LED CHASER KIT

A very familiar sight seen at discos, department stores, andon neon signs. 16 LED's flash in sequence up -down or alter-nate. Adaptable to 120 vac. (Extra)

Model N EK8OLC016 PRICE: 422.95

16 CHANNEL MULTI -MODE LED CHASER KIT

We're proud to add this to our line. It's similar to our 15channel led chaser but with many extra features. There areover 60 selectable modes. A few are: Up, Down, Skip, Pulse,Scramble, Single Pulse, Multi Pulse and many more. Anoptional 120 vac board is available. (Extra)

Model N EK8OLCM16

POWER SUPPORT 120

PRICE. $32.95

To LEDChaser

A 120 volt power board which allows you to connect regularlamps to our LED Chaser Kits. 8 channels are supplied perboard with 150 watts per channel. They can be easily inter-faced for 16 channels.

Model N EK8OPLC120 PRICE: $24.95

MODEL EK80AM001

CRYSTAL RADIO KIT

A self powered radio which uses a resonant circuit and detector for AM radio reception. An ideal project for the beginner.

Model N EK8OCR001

STEREO AUDIO

MIXER Kit$49.95

0-28 VOLT POWER SUPPLY KIT

PRICE: $8.95

2-PHONO

1 -MASTER

EXPANDABLE

RESP.20Hr -20Kliz

5V OUTPUT

.01%015T.

A true 0 to 28 volts capable of delivering 1 amp continuous.Full wave rectification, filtering and capacitance multiplica-tion provides a clean dc source for sensitive audio and digitalwork An ideal supply for the experimenter.

Model N EK8OPS028 PRICE: $39.95

ALL KITS COMPLETE WITH DETAILED INSTRUCTIONS & PCB.

*DEALER it EDUCATIONAL INQUIRIES INVITED.

535 Yonge St., Tor.. Ont. M4Y 1Y5

1.5 to 24v POWER SUPPLY KIT

A variable Power Supply suitable for manydigital and linear applications. Delivers anoutput current of 100ma. from 1.5v to. 15v and500ma. from I6v to 24v.

MODEL EKHOPS024 PRICE $24.95

LTD.

STEREO PHONO PREAMP KIT

Anyone with a ceramic input receiver can enjoy the qualityof a magnetic cartridge with this simple but very effectiveStereo Phono Preamp.

Specifications: Standard RIAAFrequency Response: 20Hz to 2KHz 1.5dBInput Sensitivity: 5mv input for 500my outputMaximum Output: 700mv rmsInput Overload: 100mv rmsS/N Ratio: Greater than 60dB

Model N EK80SP001 PRICE: S11.25

5 WATT IC AUDIO AMPLIFIER KIT

A general purpose 5 watt amplifier with Thermal Overloadand Short Circuit Protection. Because of its low operatingvoltage and high power output, it allows the user to use it asan add-on amplifier for car stereo.

Specifications:Frequency Response:Power Output:

Distortion:Load Impedence:V Supply:

Model N EK80A005

40Hz to 15KHz BI-3dBl5 watts at 4 ohms7 watts at 2 ohms5% at 7 watts at 2ohms2 to 16 ohms12 to 15vdc

BBD AUDIO DELAY LINE KIT

PRICE: $19.95

A unique Special Effects Unit which gives avariable or fixed delay of Analog Signals,Reverb, Echo and Flanging.

Specifications

Maximum Input 2.0v rmsDelay Time 6 to 30ms. (int .osc.)Distortion at Iv at 1KHz 0.3%S/N at 2v input 67dBV supply 5vdc and -15vdc

MODEL WEK80B8D01 PRICE: 469.95

6 Circle No. 5 on Reader Service Card. ETI - JULY 1980

NEWSSuper ColourIn a Desktop ComputerInvitations to press conferences come in ona regular basis to our offices and we usuallygo as an opportunity to get a firsthand look atnew products and to meet the people whosend us news releases.

One such event took place at HewlettPackard's headquarters in Mississauga to intro-duce the System 45C Desktop Computer.

The system, featuring graphics computa-tion is capable of displaying results in up to4,913 colours on a cathode ray tube (CRT)display.

The HP Series 9800 System 45C is de-signed for engineers and scientists who havecomplex design and analytical problems. Itconstitutes a complete workstation - withbuilt-in colour graphics CRT display, lightpen, operating system, read/write memory,enhanced -BASIC language, keyboard, massstorage system, and thermal line printer -all integrated into a single desktop unit.

The System 45C can solve complexgraphics -computation problems and, at thesame time, provide three-dimensional re-

presentations in solid or wire -frame form.Results can be displayed in vivid colourscoded to enhance interpretation of results.The system provides 70 graphics statements,which relieve the user of many programmingtasks such as generating geometric figures.

The colour commands allow displayingalphanumerics and lines (vectors) in eightcolours; a choice of 4,913 shades of colourare available.

More MOS From RCAThe CA080-series BiMOS operational ampli-fiers, RCA equivalents of the industry typeTL080 BiFET series, have been introduced byRCA Solid State Division. These BiMOSamplifiers offer improved characteristics overthe TL080 BiFET devices. The CA080 isan externally phase compensated single amp-lifier, and the CA082 and CA083 are inter-nally phase compensated dual amplifiers.The CA080, CA081 and CA083 have pro-visions for external offset nulling.

The CA080-series types feature gate -pro-tected MOS/FET (PMOS) input transistors forhigh input impedance (1012R typ.) and awide common -mode input voltage range, andbipolar and MOS output transistors for a wideoutput voltage swing and high output currentcapability. Other features include very low in-put bias and offset currents, low input offsetvoltage, fast slew rate, a typical unity -gainbandwidth of 5 MHz, and low distortion. Alltypes are direct replacements for the TL080BiFET series in most applications.

The CA080 types are supplied in a varietyof package options, including the 8 -lead plas-tic DIP (Mini -DIP), the 14 -lead DIP, the 8 -lead TO -5 style, the 8 -lead TO -5 style with

Geometric figures - such as circles, rec-tangles, regular polygons, and objects repre-sented in matrices - are drawn on the CRTthrough simple commands. An additional"FILL" parameter quickly adds colour fillto any of the drawn figures. Assigning suchcomputational tasks to the System 45C'sfirmware relieves the user of writing appli-cation routines to accomplish these graphics.

The light pen, supplied as part of thestandard System 45C, provides a convenientway for the user to pick, move, and con-struct objects on the CRT display. Usingthe light pen, selection of an individualpixel (dot) is possible. A second -order,predictive algorythm (located in firmware)

dual -in -line formed leads (DIL-CAN), and inchip form.

Typical prices are less than $1.00 US inquantities of 100-999.

Further information and copies of thedata bulletin may be obtained from RCASolid State Division, Box 3200, Somerville,NJ 08876.

moves the cursor in the direction and speed ofthe light -pen motion.

The colour of the high resolution CRTmakes most colour TVs look sick by compari-son. Under darkened conditions the colourscame across with intensity that was quitesimply staggering. The demo program wewatched ran through the various applicationswith emphasis on the value of colour on datainterpretation.

The standard system comes with 187K fora mere $56,801 Cdn. If you're keen onknowing more write to: Inquiries Manager,Hewlett-Packard (Canada) Ltd., 6877 Gore -way Drive, Mississauga, Ontario L4V 1M8.

It.

Cheaper Fiber OpticsAll of Morotola's Fiber Optic componentshave been reduced in price by approximatelyone third. The price reductions mark the ini-tial transition into the volume productionphase of manufacturing, and are expected toaccelerate the implementation of fiber opticsin equipment designs.

Included in the price reduction are Moto-rola's latest ferrule emitters and detectorsas well as its earlier TO -18 fiber optic compo-nents.

You can of course win an evaluationkit of these components absolutely free.Details are in the June 1980 issue on page43, but hurry, contest closes on the eigh-teenth of this month.

ETI-JULY 1980 7

THE BEST BUYS AVAILABLE!

15MHz OscilloscopesCHARGEX $695. each

F.S.T. INCLUDED

Model 653103" DUAL TRACE Portable Scope

IMM11111111111111111.

The Model 65310 is a truly portable, dual trace,15MHz scope offering battery operation as a standardfeature. This is an ideal oscilloscope for the service -

man who needs a combination bench and portableinstrument. This scope is packed with features:

* Operates from 3 power sources:1) Rechargeable NiCad batteries2) 12'OVAC line (also charges batteries)3) 11 - 30VDC

*

** 3" High Brilliance CRT ** Fully Automatic Triggering ** Built-in Calibration Source ** Trace Rotator ** 2mV Vertical Sensitivity ** Operating Modes CH -A, CH -B, Dual, Add/Sub *

Chop, and X -YWEIGHT: 13.5 lbs.OPTIONAL ACCESSORIES: Combination 1:1 and10:1 switchable probes(compensated). Priced at$39.00 F.S.T. included.

Vinyl carrying case for Model 65310 only, pricedat $62.00 F.S.T. included.

Matermester

Model 656105" DUAL TRACE Bench Scope

The New METERMASTER Model 65610 scopeemploys an extremely bright 5" rectangular CRTwith internal graticule. External DC operationpermits floating measurements. Take a look at thefeatures this scope has to offer:

Operates from 2 power sources:1) 120VAC line2) 11.5 - 30 VDC

Frequency Response 15MHz(-3d B)Fully Automatic TriggeringBuilt-in Calibration SourceTrace RotatorHF Rejection'5mV Vertical SensitivityOperating Modes CH -A, CH -B, Dual, Add/SubChop, X -Y, and Z modulation.

WEIGHT: 16 lbs.OPTIONAL ACCESSORIES: Combination 1:1 and10:1 switchable probes(compensated) Priced at$39.00 F.S.T. included.

Call one of our offices (below) for a no obligation, free of charge evaluation.

MetermasterR.H. NICHOLS

Toronto (416) 661-3190 Montreal (514) 337-0425 Edmonton (403) 432-7746* Ottawa (613) 238-7007

Circle No.2 on Reader Service Card.

NEWS

MPU Jet EnginesAn aviation fuel savings of 136% doesn'tsound like very much, but when translatedinto actual figures,1 it amounts to more than7,500,000 gallons a year for Pan AmericanWorld Airways' fleet of 747 Jumbo Jets.That's what Pan Am will be saving when itfinishes the installation of Delco Electronics'new Flight Management Systems. The heartof the system is the Flight ManagementComputer which utilized Motorola's NMOSLSI circuits. In today's dollars, this savingsamounts to approximately $5.55 million peryear.

Pan Am began installation of the FlightManagement Systems in early 1980 on itsfleet of 10 Boeing 747 SP's (long range jum-bo jet) and on 29 standard size Boeing747-121 models.

Pan Am's selection of the system con-taining Motorola LSI circuitry was awardedfollowing a year of flight test and evaluationon a 747 in regular scheduled service. Theresult showed a fuel efficiency improvementof some 1.5 percent when the FMS was used.

Each Pan Am FMS System is composedof four 'black boxes' -a computer, an alpha-numeric control display, a switching unit forelectrical hookup, and a unit to monitorengine data.

Fuseful CatalogueBussmann Manufacturing, St. Louis, havejust introduced their new 40 page SmallDimensional Fuse/Holder Catalogue SFB-8 O.

This new Buss catalogue covers theircomplete line of fuses/holders for the elec-tronic industry.

Included in this full colour Buss catalogueare complete specifications and blowingcurves on fuses and detailed information onfuse blocks and holders.

Bussmann Manufacturing is represented inCanada by Atlas Electronics Limited, 50Wingold Avenue, Toronto, Ontario M6B 1P7.

Britain To Get CBPlus Garbage ChannelsAlthough in North America and most ofEurope we take CB for granted, it has re-mained illegal in Britain. This has notprevented its use and an estimated 100,000CB'ers are active using smuggled rigs - eventhe import and sale of these is prohibited. Thelevel of activity is such that if the skip is rea-sonable you'll hear the much higher noiselevel on Channel 14 which is used for calling.

The pressure for legislation has led toalmost weekly demonstrations and finally theBritish Government have said they'll considerit, not on 27 MHz, but 900 MHz. There willbe 40 channels but what is interesting is thatanother 40 channels are to be introduced forother uses such as digital transmission be-tween computers: these are entitled 'Gar-bage Channels'.

900 MHz may seem a high frequency with-out much hope of getting out far - but thinkhow small the antennas will be!

High Fidelity With JanaThose wonderful folks who brought you CBs,Jana Kits and components are now plunginginto the audio field with a line of no lessthan eleven record and tape care products.

Additionally look for consumer pro-ducts such as portable radios, car stereos andspeakers, headphones and intercoms bearingthe Jana name.

Special Publicationsfrom ETI

25 of the most popular projects fromour earlier issues Including:Audlo Limit-er, 5W Stereo, Bass Enhancer, ModularDisco. 50W/100W Amp modules, IBMetal locator, Heart Rate Monitor,Phaser, Touch Organ, ElectronicMastermind, Double Dice, ReactionTester, Sound Operated Flash, BurglarAlarm, Injector -Tracer, DigitalVoltmeter. 100 pages.

$3.45 (inc postage)

Useful design ideas

I r off t Eleoinonics Today.

Over 150 circuits plus articles on CircuitConstruction, Test Gear, a project on aDigital Panel Meter, Design notes onSpeaker Crossovers, TT L pin -outs,Design notes on Crystal Oscillators.108 Pages.

$4.95 (inc postage)To order, use the card facing page44 or send money to: ETI Magazine25 Overlea Blvd., Unit 6, Toronto,Ontario M4H 1B1

ETI-JULY 19809

NEWS

Wireless SecurityA two-part, ultrasonic security system thatuses the existing electrical wiring to sound analarm has been developed by a company loca-ted in Markham, Ontario. The Tellus TSSsimply plugs into any electrical outlet. Whenthe Intruder Sensor detects motion, it sends asignal through the existing household wiring.The Receiver/Alarm is activated only whenit receives that signal and sounds a loud 105decibel horn. This principle allows the alarmto be plugged in anywhere, even in yourneighbours home if you are going to be away.The Tellus TSS can be used to protect yourhome, apartment or cottage and any numberof sensors or alarms can be used to provide atotally integrated security system.

The product has been designed, engineeredand is manufactured totally in Canada, byTellus Instruments Limited, 91 Esna ParkDrive, Unit no. 9, Markham, Ontario L3R2S2 and is covered with a five year warrantyon parts and workmanship.

Novel R Box(es)A flexible resistor substitution system hasbeen introduced by Electronic Industrials.

The system consists of a series of sevensingle decade resistance boxes that can be'daisy chained', to produce values of up to1,111,111 ohms. The modular concept al-lows the user to break up the set to be used inseveral applications simultaneously.

Additional accessories include a seriesammeter and also a zener substitution box.

Write to Electronic Industrials Company,P.O. Box 458, Downsview, Ontario M3M3A8.

Looking BackAlready inquiries are flooding in on our ClickEliminator project. Here are a few answers.

The parts list only makes mention of re-sistors for right hand channel. You will alsoneed C101-106 (identical to Cl to C6),RV 101 (identical to RV1) and ICs 101-103(you get the idea).

The TL083 is a Texas Instruments chipavailable from Active Components for $1.30US. You can also get the LF 356 from them,but shop around, it's fairly widely available.

The TDA1022 BBD is the real problem inthis project. At this writing there are 29 unitsin Canada and delivery times are approxima-tely 8 weeks. We have been assured thatPhilips Electronics can obtain more stockshould the need arise. This IC can be orderedthrough any Philips distributor.

os'k09%0 Aw

tii 74.c* .0""?

fr...0:01.0°A t.e

Expose YourselfNews Digest is a regular feature of ETI Maga-zine. Manufacturers, dealers and clubs areinvited to submit news releases to NewsDigest, c/o ETI Magazine. Sorry, submissionscannot be returned.

P.M.I. DistributorZentronics announces the aquisition of a newproduct line, Precision Monolithics.

P.M.I. is a manufacturer of high qualityprecision linear bipolar intergrated circuits.The two principal areas of their product lineare operating amplifiers and data conversionproducts.

Product will be stocked in all eight Zen-tronics locations.

Write to Zentronics, 1355 Meyerside Dr.,Mississauga, Ontario L5T 1C9.

The Last Word'What will they think of next?', is a well usedexpression quite unsuitable in the news sec-tion of any magazine, but sometimes youhave to wonder.

A California (where else?) engineer hasdeveloped a solar powered tape recorder thatcan be imbedded in a tombstone. The idea isto activate the appropriate button and youcan hear the last words of whoever is restingsix feet below you. (Oh, I'm sorry, we're youeating breakfast?)

According to the inventor, Stanley Ze-lazny, the 'Memorial Audio ReproductionSystem' has been well received. The devicecan also be used in historical monuments togive visitors a short history lesson. Alterna-tively it can be used as a warning device inpotentially dangerous unattended instal-lations.

If you're really interested you can writeto Miracles In Motion, 106301/2 Valley SpringLane, Toluca Lake, CA 91602.

ETI Book ServiceSingle ICProjects

There are now a vast range of IC'savailable on the amateur market, themajority of which are not necessarilydesigned for use in a single applicationand can offer unlimited possibilities.All the projects contained In this

book are simple to construct and arebased on a single IC. A few projectsemploy one or two transistors inaddition to an IC but In most cases theIC Is the only active device used.BP65 $6.25

ElectronicCircuitsforModel RailwaysM. H BABANI, B (Eng.)

In this book a number of construct-ional projects and ideas are discussedDetails are given on how to build threetypes of model train controller andIdeas on signalling are considered indetail.BP213 $4.50

Use the card facing page 44 or send to:ETI Magazine, Unit 6, 25 Overlea Blvd.,Toronto. Ontario. M4H 1B1

10 ETI-JULY 1980

FEATURE

CMOS 555APPLICATIONSTim Orr brings you the result of bipolar versus CMOS in the 555 league.

THE BIPOLAR 555 timer has been around for many years,but there is now a CMOS version that has some very sig-nificant design improvements. The two devices arefunctionally very similar, being interchangeable inmost applications. The operation of the 555 is very simple,(Fig.1). It consists of a pair of comparators that operate at 1/3and 2/3 of the supply voltage, this being set up by a resistorchain. These comparators set and reset a flip flop which inturn drives the output stage. A second output is availablewhich is an electronic switch, (Discharge) to ground. Otherfeatures include access to the resistor chain via the controlvoltage pin and an extra reset input to the flip flop Thissimple network readily lends itself to all sorts of oscillatorsand timer circuits.

GND 1

TRIGGER

OUTPUT

RESET 4

2

3

CONTROLVOLTAGE

8 .Vcc DISCHARGE lC 14 *V..7 DISCHARGE THRESHOLD 2C 13 DISCHARGE

6 THRESHOLD CONTROL VOLTAGE 12 THRESHOLD5 CONTROL VOLTAGE RESET 4 7556 11 CONTROL VOLTAGE

OUTPUT 10 RESET

TRIGGER 6C A ',I 9 OUTPUTGND 7C 8 TRIGGER

3

Fig. 1. The pin -out and internal configuration of the CMOS 555.

The bipolar 555 has a few parameters that can make itdifficult to use, but which have been improved in the CMOSversion, (Fig.2.). The bipolar quiescent supply current isgenerally about 10 mA which negates their use in smallbattery units. The CMOS version consumes a mere 120 ua.

PARAMETER CM 7555 BIPOLAR 555C

QUIESCENT CURRENTVcc +15V

INPUT CURRENT TRIGGERTHRESHOLD

RESET

MAX. OPERATINGFREQUENCY

POWER SUPPLY RANGE

PEAK SUPPLY CURRENTTRANSIENT

RISE AND FALL TIMEAT OUTPUT

TYPICAL120uA

50pA50pA

100pA

500kHz

2 AP- 18V

10mA

40nS

TYPICAL10mA

Ou5AOu1A0m1A

500kHz

4VS-.-16V

370mA

100nS

Fig. 2. A comparison between the Bipolar and CMOS version of the555.

Also the CMOS inputs are very high impedance havinginput currents down in the pico amp region. Another majorimprovement is the reduction in the power supply currenttransient during an output transmission. The bipolar is verynoisy in this respect and can often be the cause of lots of'funnies' in nearby circuits.

The CMOS 555 is a low power high input impedancedevice that should be used where low current consumptionis at a premium. The following circuits illustrate somepossible uses of the device.

400

300

SUPPLYCURRENT BIPOLAR 555

7555100

ZOO 400

TIME

600 000,,S

Fig. 3. The CMOS 555 displays an impressive reduction in supplycurrent transient during an output transmission.

ETI-JULY 1980 11

FEATURE

2/3 Vec

B1/3 Vec

I.Vce

A

OV

TIME CONSTANTSCIRa*RblCIlia)1Rbl

CRb I CRb

7555

OUT

THRESH

Fo x 1.46

Ille+2RbIC

A FREQUENCY RANGE OFA FEW CYCLES AN HOURTO 500k111 ARE POSSIBLEUSING THIS CIRCUIT

Fig. 4 (above) A simple oscillator can be constructed using tworesistors and a capacitor. Due to the high input impedance of theCMOS device, resistor values up to 100M may be used. Theoperation is as follows. Capacitor C is charged up via Ra and Rb andso rises with a time constant of C(Ra + Rb). When the voltage Breaches 2/3 Vcc, the threshold hold comparator goes high causingthe output (pin 3) to be set low. Also the discharge FET (pin 7) isturned on. This discharges the capacitor via Rb with a time constantof CRb, until the voltage B reaches 1/3 Vcc.

This causes the trigger comparator to go low which sets theoutput high and turns off the discharge FET. Thus, the voltage Boscillates between 9/3 and 2/3 Vcc. The waveform is asymmetric butdue to the nature of its generation its frequency is virtually invarientwith regards to supply voltage changes. It is possible to generate asawtooth waveform by reducing Rb to a short circuit. This causesthe reset time to be very fast, of the order of a few microseconds.However, there is a propagation delay through the device from thetrigger comparator to the output which causes the dischargingwaveform to overshoot the 1/3Vcc limit, thus making the waveformat B larger. This will cause the oscillation frequency to be lower thancalculated. To maintain the calculated frequency, the dischargeperiod should be 5 uS seconds or longer.

A

Fig. 5 (above) This oscillator has a symmetrical output because thecharge and discharge paths are the same and the portion of theexponential cruve that is used is symmetrical. Note that in thiscircuit, the discharge pin (7) is available to do other jobs, such asdrive a LED or some other device. The timing resistor R should bekept relatively high (above 10k) to prevent loading of the output.

R2

154148 4k7

Vcc I4V TO 18V)

R3470R

D2RED LED

CI242

1 OrnSEC

1SECOND

OFF

ON ON

Fig. 6 (above) This circuit is an oscillator that has a wide mark tospace ratio. It is OFF for approximately 1 second and then turns ONfor about 10 mS. During this latter period the LED is turned on bythe discharge FET. The long OFF period is generated by the RI, Cl

time constant, whereas the short ON period is produced by D1(which is forward biased) and R2, C1. The average currentconsumption is relatively low. If the unit were powered from a 9 Vbattery, then the current would be 120 uA for the ICM 7555 and anaverage of 140 uA for the LED, making 260 uA total. This wouldgive a lifetime of a few months for a 9V which would be extendedby lengthening the OFF period (increase RI) and reducing the LEDcurrent (increase R3).

2/3 Vcc

A4V

Vcc 199 TO +18VI

R347k

25390412 C2

100n

FC"TRIGGER INPUT

-51/ R410k

NOTE NO RETRIGGER

SWEEP TIME T = Vcc n 2/3 CI

ANO = 12.7 - (771

R2

Fig. 7 (above) The 7555 is used to initiate and terminate a triggeredsweep. Normally the discharge FET (pin 7) is ON and so Cl isshorted to ground. When a trigger is applied to the input, thecollector of Q2 momentarily goes low which sets pin 7 of the 7555in its OFF condition. (11, R1, R2 and 131 form a current generatorthat drives C1. Once the discharge FET has been turned OFF, thevoltage on Cl rises linearly. When this voltage reaches +2/3 Vcc,the threshold comparator sets the discharge FET into its ON stateand so C1 is shorted to ground. ICI is used to buffer the voltage onC1. The sweep generator is not retriggerable and is only initiated onfast positive going inputs. To vary the sweep rate, alter C1 and orR2.

C21004

CIC3

R339k

min+ loou

1N4148D2

DC TO DC CONVERTER

.9V

A

0

8V NO LOAD

C -8V NO LOAD

-7V AT 0.5mA

Fig. 8 (above) A DC to DC converter can be constructed from anoscillator and a diode charge pump. The 7555 forms a highfrequency square wave oscillator. The squarewave from pin 3 is ACcoupled via C2 to the charge pump. The voltage on the negative sideof C2 is prevented from going more than OV7 positive by D1 and sothe square wave on this side of the capacitor biases itself so that itmoves from +0V7 to -8V3. D2 charges up C3 on the negativeexcursion of this waveform and so a negative rail of about -8 V isgenerated. The current that can be taken from this rail is rather low.being determined by the oscillation frequency and C2. Generally DCto DC converters have a poor transfer efficiency.

12 ETI-JULY 1980

IN4148

2k7

1

100o

TUNE FOR MAXRECEPTION

F o 40k Hz

471/

40IcHzRECEIVER

TX CURRENT 11.1.1t,

1k0

III

OUTPUT

390p

10n 330k 56k

390k

/II100n

ULTRASONIC40kH,AIR TRANSDUCER

1D3VWORKING

AUTOTRANSFORMER

27SWG WIRE10 TURNS AND 100 TURNSWOUND ON A SUITABLEFERRITE POT CORE

40kHz BADPASS FILTER

MAA 40kiN SIGNAL,TO DETECTOR

kVcc

Fig. 9 (above) The 7555 can be used as the driving oscillator in anultrasonic remote control system. The oscillator generates a thinpulse about 2.5 uS long at the natural resonant frequency of thetransducer. This short pulse is used to turn on a transistor (Q1)which drives an auto transformer with a 10 to 1 step up ratio. Theoutput of the transformer is connected to the transducer and whenthe oscillation frequency is correct a 100 V peak to peak sine wavewill be produced at this point. The transducer is usually a crystalwith a high impedance and so a high operating voltage is required toproduce any power output. The receiver is a 40 kHz bandpass filter.This will amplify any audio signals at this frequency, which can thenbe sent to a detector circuit.

Vcc 1.5 TO 18V1

RV147k

20 TO 1CONTROL RANGE

Cl470e

1

Fig. 10 (above) This oscillator allows the mark space ratio at pin 3 tobe varied from 1 to 20, to 20 to 1, by using two feedback routes.When pin 3 is high, Cl is charged via D1, part of RV1 and R1. Whenit is low, C1 is charged via D2, the other part of RV1 and R1. Thusthe position of the RV1 wiper determines the ratio of the charge anddischarge periods. The oscillation frequency is slightly dependenton this ratio.

3Act 1.8V TO 18V1 VetYcc

TO INDEPENDANT OF VCC

FREQUENCY 487CONTROL

Fig. 11 (above) By making a loop out of a 7555, an inverter and anintegrator, a triangle t square wave oscillator is produced. Tooperate well at high frequencies (up to 40 kHz) a CMOS invertershould be used to replace the transistor inverter. The op ampprovides a low impedance triangle output, the frequency of whichmay be controlled with the 1M log pot.

PIN 4 CAN ME USEDTO GATE THE TONEON AND OFF

A

CONTINUOUS 1.3kHz TONE

2N3906

BOR

Fig. 12 (above) The 7555 can be used to generate an acoustic tone.The osciNator is set to vn at 1k3Hz which has a low period of about15 nS and a high period of about 755 nS. During the low period thetransistor is turned ON and so the loudspeaker is connected acrossthe power supply and sinks at about 100 mA (for a 9 V supply). Thisgives it a 'kick' on every cycle of the oscillation. As the transistor isonly on for 15 out of every 770 nS the average current through thespeaker is quite smal,, being about 1.95 mA. Therefore, the totalcurrent consumed by the whole system is only about 2.5 mA (at 9V), and yet the 20 mW output signal is quite audible.

ETI-JULY 1980 13

FEATURE

Fig. 13. A warbling tone can be generated by using two oscillators.The warble is produced by IC1 which generates a 13 Hz wave formthat is used to frequency modulate the tone generator as describedin the previous example. Pin 5 of a 7555 is connected to the + 2/3Vcc tap on the resistor ladder. By tying it to a 'warble' waveform,frequency modulation of the final output tone is produced. A 7556could be used instead of two 7555's.

'BEEP'PERIOD

3 SECONDS

470k

)k 1 54148

1+5 TO +18V/i-Vcc

262

/7777

10+

7555'Cl

10k

T47n

75551C2

4708

154 14 8

5

10k

154148

'BEEP'

/7777

253906

LS808

S

Fig. 14 (above) The police and other emergency services use arepeating high frequency 'beep' on their radio networks. Thisdoesn't interfere with the normal radio traffic and allows thelistener to be certain that he is still tuned in correctly to that channel.The circuit generates a similar 'beep' and yet consumes only acouple of milliamps. IC1 is a slow oscillator (3 second period) with alarge mark/space ratio. The discharge FET is on for most of the timeand only goes OFF for about 15 milliseconds in every 3 seconds.This FET is connected to the tone generator in such a manner thatwhen the FET is ON the tone generator is inhibited. When the FETgoes OFF the generator produces a burst of 3 kHz oscillations whichare heard as a 'beep'.

1 54148

68k

4

1 SEC 4.-

1.5 TO +18VI `Vcc

n 4708 154148

INCREASE TO 2k7 FOR A LOUDER OUTPUT

253906

A

B

OV

cc

OV

+Z/3 Vac

Tmono . 1.1 x R3 x C2

Fig. 16 (above) The 7555 can be made into a monostable, althoughsome problems may occur in its use. A negative going pulse on thetrigger input (pin 2) can be used to start the monostable period. It isimportant that this pulse goes high again before the end of themonostable period, or else it may prolong the period. To this end anAC coupled trarsistor inverter has been used so that a risingpositive signal will initiate the event. Initially C2 is discharged toground. When pin 2 is taken low, the discharge FET is set to be OFFand so the voltage at E rises with a time constant of C2, R3. Whenthis voltage reaches + 2/3 Vcc, the discharge FET is turned ON, C2 isdischarged to groiund and the monostable period is finished. Duringthis period the 7555 produces a high output at pin 3.

V

23.V2O:

OV

27%

lkO

27k

imam C2 2/3 VacIA8C

Fig. 17 (above) The previous circuit has been modified. The timingresistor has been replaced with a programmed current source, IC2.Whatever current is put into pin 5 of the CA 3080 (the Imm current)will appear at its output. This will linearly charge up C2 when theFET switch is turned OFF. The monostable action will be the sameas in the previous example. The monostable period is linearly

OR proportional to the IA., current so by programming this current theperiod is controlled.

Fig. 15 (above) The last type of sound generator to be described is asimple siren. IC1 generates a sawtooth waveform which is used tofrequency modulate, via pin 5, the tone generator (IC2). As thesawtooth voltage rises (with a period of 1 S) so does the tonegenerator frequency.

rLJINPUT FREQUENCY

FIN

Tmono

PULSE AT SAMEFREQUENCY AS

INPUT

v out

/7777

SMOOTHED OUTDC VOLTAGE

Vout = (Fin x Tmono x Vccl

14 ETI-JULY 1980

MONOSTABLE PERIODEQUALS PERIODOF FIN

hildr

APPROX .1VABr

470p

020n

Smarm- 11fluSEC

Fig. 18 (above) The monostable can be used to linearly convert afrequency into a voltage. The pulses at the output pin of the 7555 inthis circuit are fixed in length but occur at the fundamentalfrequency of the input signal. Thus the average equivalent DCvoltage of these pulses will be linearly proportional to theirfrequency. This averaging can be performed very simply with a CRlow pass filter. This filter determines the response time of thecircuit and the ripple. A long time constant will have little ripple andrespond slowly and vice versa. Care must be taken to not exceed therange of the monostable. When the period of monostable exceedsthat of the input signal, the circuit will miss every other period andwill drop its apparent output by an octave.

Fig. 19 (right) IC1 and 2 form a triangle/ squarewave oscillator. IC2is a non -inverting, programmable rate integrator and its outputramps up and down between the 1/3 and 2/3 Vcc limits set by IC1.The rate at which the integrator ramps up and down and hence theoscillation frequency, is determined by the 'ABC current. Because theinput impedance of ICI is so high, it is possible to directly connectthe timing capacitor to it, without any unwanted loading effects.This circuit has excellent high frequency performance producinggood quality triangle wave forms at 40 kHz. The circuit can alsoproduce very low frequency signals by making C a 100n tantalumand IAB,. a current of say, 1 nA. This oscillator would then have a

period of 800 seconds. IC3 is used to buffer the triangle to theoutside world. If a 741 is used, then the waveform will becomeasymmetrical at low 1", currents (below 1 uA) due to the input biascurrent needed to run a 741. A TL081 has very little input currentand so could be used for both low I, currents and high frequencyperformance. If low power is needed, then a TL061 (200 uAquiescent) could be used.

By dosing switch Si. the oscillator will produce a sawtoothwaveform and a pulse.

OPE NSi

StCLO

SE 0[

Q -Vcc s8V -0 .18V1

SQUARE/PULSE

71_A_2/3 V.

B1/3 V.

A

Vee

VC

0 TO sGV

SIMPLE VOLTAGE TOCURRENT CONVERTERTO DRIVE THE CA3080

TRIANGLE /SAWTOOTH

741 ORTL081 ORTLO61

.Vet

Ok

253904

104

!ARC

TABS Er ETII!!Prices shown include postage and packing. Order using the card facing page 44 or send to Book Service, ETI Magazine, Unit 6,25 Overlea Blvd, Toronto, Ontario. M4H 161

1071 $10.901076 $11.55

I im) YOUROW? WORKING

f 4

BY DAM L MEINERNAN

The CompleteHandbook Of

RObOtICS

1010 $9.85

1015 $5.7)

a5 er as er A BEGIfiNER S UDEHandbook of Handbook a TO COMPUTE Mt

1 0 0 1 0 0 1Practical Electronic Circuits

Edited by Kendall Webster Sessions

A Comprehensive collect!. 31 1001 integrated111011 and transistor 1,11011 unte all the dataneeded to pul them 10 wall Alarrns-nod.0---emplillers-Aulomolive Filrers LogicCounters P. Clocks-Power Supplies-VoltageMullophers-Recelvers RE Preamplifiers A

Converlers-Regulalors- OF Generale's A

Waveshapers-OF Power Amplifiers-TestEquipmenl-Control A Tone entuds-CarrierOperated Relays and Other Repealer C$retnle-Inners-Transmitters Transceivers EmilersVFO Circuils-Gallery Chargers-DiodeCocuils-Miscellaneous Simons

ractical Elettronic Circuits

Edited by Michael L. Fair

ES It. ADAMS

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PROJ EC T

HEBOT'A chicken in every pot and a Hebot in every garage', that's the motto atETI these days. Combining economy and efficiency, form and function,we present a realistic, revolutionary and robust robot to terrify your cat!

Since earliest times man has had a fas-cination for robots in some form oranother. Along with their pursuits forthe Philosopher's Stone and mattertransmutation, some medieval alchemiststried their hand at creating life.

These early attempts were more prac-tices in wizardry (or fraud) than any-thing else. It wasn't until much laterthat writers and dreamers thought ofmechanical men in the service of hu-manity. Of course everyone knows theterm robot originally came fromCapek's play 'Rossum's UniversalRobot', a story of the 'perfect' servant.

Since that time, the idea of robotshas taken firm hold in people's minds.Robots are the ultimate servant, unsel-fish, totally obedient and reliable. Onthe other hand, robots may well lead tothe ultimate destruction of mankind aswe know it.

Numerous theories have beenadvanced to explain man's fascinationwith his mechinaical counterpart. It hasbeen suggested that the human race issimply one step in some evolutionaryprocess (aren't robots a superior form ofperson?). Another theory is that bymaking robots, man is trying to playGod; proving his own power of creation.Then of course, the economic value ofa successful general purpose robot isbeyond measure.

Enough rambling.

The basic mechanics (apart from the cover)are shown here including the drive motors andwheels

Enter ETIWhatever our motivation might havebeen, we at ETI feel that the homerobot is long overdue. Hebot is probablythe most versatile robot project offeredto date.

ETI has co-operated with RemconLimited, one of Britain's foremost man-ufactures of remote control equipment,to produce a classy chassis we feel willbecome a standard for many years tocome.

The cornerstone of the design is a

hexagonal aluminum chassis pan whichcarries the micro -drive units, batteries,sensors and PCBs on which are mountedthe electronic components. We tried anumber of different collision sensorsand discovered, as Edison used to put it,an awful lot of ways NOT to do it. Ourprototype features microswitches whoselever arms have been extended withpre -formed lenghts of piano wire. How-ever, the production kits from Remconfeature sensors mounted integrally withthe chassis pan. Another point worthyof note is our use of a plexiglass coverfor the prototype. The production kitfeatures a pre -formed three piece alu-minum cover as the plexiglass versioncosts more than all the othercomponents put together.

The microdrive units feature a fullyenclosed gearbox and five pole motorwith the drive wheel mounted on a steelshaft integral with the gearbox. Typicalmotor drive current is around 150mAgiving between one and two hour's lifefrom 450mAH capacity nicad cells(AA size). The chassis can turn on itsown axis and will carry a payload of upto five pounds of weight. Previouslypublished robot designs in other maga-zines have been let down by poor mech-anical design or the use of difficult toobtain or reproduce electronic compo-nents. The precision engineered designfrom Remcon which has resulted fromour consultation with them removes one

liCh 99\V ".1.&

told you not to leave it out overnight!'

of the main pitfalls of any project ofthis type.

SuperlativeIf Hebot's chassis is good (which it cer-tainly is), then words cannot do justiceto the electronic design. Though com-posed of largely conventional circuitelements, the circuit represents a

breakthrough in systematic design facili-tating development and operation.

The novel feature of this system isthe separation of executive and controlsignals. In a maximal system, up to eightpairs of motor control signals may bepresent simultaneously with Hebot'choosing' between them accourding tothe state of 'priority' input sense lines.a possible arrangement might be

76 external control5

43 'avoid' manoeuvres2 tracking1 searching'0 random walk

Level seven has highest priority andzero lowest priority. Assuming Hebotwas not under external control and wasneither tracking nor searching then arandom walk would be executed. Fol-lowing any colision, priority sense inputthree would become active and Hebotwould manoeuvre himself out of troublebefore returning control to level zero;random walk. Of course, there isnothing special about the control signalschosen and any -group of signals couldbe assigned priorities and connected tothe appropriate inputs. Control levelsmay vary between +5 V (full forwardand -5 V(full reverse) with intermediatevoltages giving variable speed and zerovolts halting the machine.

16 ETI-JULY 1980

We are presenting Hebot in twoparts. The first part (this one) concernsforward motion, manoeuvres and otherforms of control, the second part willdetail the implementation of the Hebotsystem as well as a battery charger andloop drive circuit.

Hebot is a flexible, open-ended pro-ject whose scope is limited only by yourresources of imagination, skill, time and(inevitably) money. Accordingly, theschedule may be changed to accommo-date design developments and should inany case be used only as a springboardfor your own ideas.

ConstructionThe chassis, aluminum cover and mecha-nical components are available fromRemcon. The electronic components aremounted on one PCB which is sup-ported from the chassis pan by plastic'click -fit' pillars.

The use of Remcon chassis is recom-mended though not absolutely neces-sary. The motor drive circuitry wouldprobably work well with a track drivevehicle or anything else that uses twomotors for locomotion and steering.

There are a large number of wirelinks on the PCB which MUST besoldered into place first as many ofthem pass beneath components, we sug-gest you use no. 22 swg. wire for this.

Integrated circuit sockets are recom-mended for the IC's and normal CMOSprecautions should be observed to avoiddestruction of the chips by staticcharges. Flying leads are used to inter-connect someof the IC's and should besoldered into place after the other com-ponents have been mounted but beforeinserting the chips. It is impossible togive precise constructional details forthis project which ideally will be de-veloped by the constructor. However,you should find out photos helpful.

If, initially, only four inputs are re-quired then IC5 may be omitted. Un-commited inputs of IC3 should be tiedlow (to the -5 V rail) and not leftfloating.

How we installed our batteries.

ETI-JULY 1980

A bit of photographic trickery shows Hebot in its random walk mode. A light has beenfitted and the unit photographed with a time exposure followed by a flash to show its finalposition.

The chassis comes with holes formounting the batteries between thedrive motors We used 8 AA nicad cellsheld down with rubber bands, alterna-tively you may wish to use cable ties.Hardwired IntelligenceHebot's major virtue is its flexibility,which can only be fully realized with acomplete understanding of the circuitryinvolved. To this end, we stronglyrecommend you read the 'How ItWorks' section thoroughly.

Essentially there are two major sec-tions to Hebot's electronics: the variousmotor control circuits and actualpriority encoding circuitry. Theavoidance circuitry is on the first board.This requires four inputs, one 'rom eachcollision sensor. A 'collision' is detectedby grounding the appropriate input. Thecircuitry on the second board describedhere is mostly concerned with searchingand driving towards a light (photo-tropism) and tracking a cable by de-tecting an AC energising signal. The de-tails of operation of these circuits willbe dealt with fully next month.

Each motor control circuit has threeoutputs, two for motor control and one'executive' signal. With the circuits des-cribed in this article, Hebot has thecapability to follow a light beam, mag-netic loop, avoid obstacles, and performsearch manoeuvres.

To program Hebot, decide whichlevels you want to assign to which con-trol circuit. Then, simply connect thetwo control leads to the appropriate in-puts on IC5 or IC4 and executive signal)to the appropriate input of IC3. Thenground all unused inputs on IC3.

The manner in which you make theconnections is up to you. Sockets maybe employed, or alternatively connec-tions can be made in Veropins or Vectorflea clips. The latter method isn't asklugy as it sounds, connections can bequickly changed with a soldering iron.

More CapabilitiesThe rest of the circuitry enables Hebotto perform a random walk, generate ashort tone and respond to loud noises.'Rardom walk is something of a mis-nomer as Hebot actually executes aseries of spirals, enabling him to 'lookaround' his environment. The circuitwhich generates this motion is very sim-ple and quite elegant consisting of a sin-gle op -amp connected as a conventionalastable oscillator. To operate, all youneed to do is connect pin 10, IC3 toplus 5 V and connect pins A, B to pins1, 12, IC4 (X 0 Y, 0). It does notmatter whether A or B goes to pin 1 or12. This only affects the direction ofthe spiral motion.

We have also given Hebot a voice.The circuitry around IC5 accomplishesthis. IC5 is a 555 timer connected as anastable oscillator whose output is gatedon and off by driving the reset input viatransistors Q6, 7. Whenever input pin Yis driven to plus 5 V, a short tone isproduced. If you connect pin Y to the'avoid' output on the other board,Hebot will emit a surprised squeak fol-lowing each collision.

The other 555 is used with Q5 todetect sounds. Hebot can be made sen-sitive to loud noises by adjustment ofRV3. Any sufficiently loud noise will

17

PROJECT

cause the 555 output (pin X) to risefrom minus to plus five volts for aboutone second. Pin X may be connectedto any of the inputs of IC3 (only oneconnection to each input though!) tomake Hebot select control from any X,Y set of inputs. If pin X were connected

Circuit operation may be most easily under-stood by considering the operation of threeunits separately; the motor servo amp, signalmultiplexer and manoeuvre logic. Power forall three is derived from two five volt bat-teries. If the voltage seems strange, it is be-cause each battery is made from four nickel -cadmium (nicad) cells each having a nominalvoltage of 1.25 volts. You do not have to usenicads, ordinary AA dry cells will power thecircuit quite happily though battery life willbe restricted to a couple of hours' operationor less.

The integrated circuits are powered fromplus and minus five volts giving an effectivevoltage of ten volts. The junction of the bat-teries (OV) is used only as a bias point for thenon -inverting inputs of IC1 and IC2 and as areturn for the motors.

Servo AmplifiersThe servo amplifiers formed around IC1 andIC2 could hardly be simpler. Each op -ampfunctions in a standard inverting amplifierconfiguration with a gain of one (ie the out-put voltage equals the input voltage but is ofopposite polarity). Transistors Q4, 5 and Q6,7 function as complementary emitter fol-lowers and supply the motor drive current;about 150mA. IC1 and IC2 deserve a specialmention. These chips are BIMOS op -amps andfeature CMOS output stages enabling the out-put to swing very close to the supply rails,very important in this application. Ordinary741 op -amps could be used but would have avery limited and unequal output voltage swinggiving low motor drive and loss of torque. The3130 is a high speed uncompensated deviceand capacitors Cl, 2 are essential to preventhigh frequency oscillation which would causeexcessive dissipation in the semiconductorsand could result in overheating in the motors.Using the circuit shown and our PCB no pro-blems should be experienced.

Motor ControlControl voltages are applied to the servo ampsvia input resistors RI and R2. If you followthe connections from these resistors, you willsee that they disappear mysteriously into IC4and IC5. In fact these chips do not alter thecontrol voltages passing through them at all.They are simply multiplexers; an electronicrotary switch used to select control signals.Each chip functions like a four-way two poleswitch whose 'position' is determined by thestate of three control lines at pins 6, 9, 10.The binary 'address' on pins 9 and 10 selectsone pair of four pairs of inputs. The mostsignificant address line from IC3 is used toselect either IC4 or IC5 by driving the 'enable'inputs of those chips.

As this signal is inverted by Q1 beforebeing passed on to IC5, only one chip is en-abled at any time. The disabled chip behavesas though it were a disconnected switch andexhibits a very high resistance between allinputs and outputs. This arrangement enablesany pair of eight possible pairs of controlsignals to be selected according to the controlsignals from IC3 and used to drive the servoamps.

to input '7' (pin 4, IC3 board one) andX7 (pin 4, IC5) were connected to plus5 V with Y7 (pin 11, IC5) connected tominus 5 V then Hebot would execute a

spin following each loud noise. Note thatin this case, the avoid manoeuvre cir-cuitry would be inoperative as level

HOW IT WORKS

V5

iC4

Next MonthWhat we've presented so far should keepyou thinking for awhile. Next monthwe'll present loop drive circuitry and a

suitable charger.

10

,, CO

V.10 8

14

1 i

NOTES01 IS 26390404,6 ARE TIP2006, 1 ARE TIP29IC1,2 ARE; A2130ICS IS 632ICA 6 ARE 4062

MO

ov 0

+0

0RIGHTMOTOR

LEFTMOTOR

IC3.n 8.6v

Fig.1. The signal multiplexers and servo amps.

IC3 is an eight -input priority encoder. Theoperation of the chip is quite straightforward.There are eight individual inputs and a single'enable' input (pin 5) which is tied high toenable the chip. The eight input lines shouldbe held normally low. When any input isasserted high (ie connected to +5V), thegroup select (GS) output goes high, enable (E)output goes low and the binary address of theselected input appears on pins 9 (lsb), 7, 6(msb). For example if input '3' (pin 13) isasserted high then 110 will appear on pins

- Ve ICI (pin 11

V. CI 1,6n 11

5V

9, 7, 6. However, if - while '3' is still high -'5' is also asserted high then the address out-put will change to 101 as five has a higherpriority than three and the inputs corres-ponding to that number will be connected tothe servo amp by multiplexer IC5. In thisway, the motors are controlled by signalsfrom one set of inputs until a higher priorityline becomes active at IC3 when the addresswill change and another set of inputs will beselected.

For example, let input '2' (pin 12, IC3) be

NOTESIC2 IS LM324 (pin 415 Ve; pin 11 IS -Ve SUPPLY)02,3 ARE TIL7804 IS 203904D7 IS 104148LED 1 IS ANY LED ITIL220)

9

027100k

028100k R29

470k

032100k A R36

R30100k

03182010

IC1 Ipin

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Fig. 3. Light seekingcircuitry.

LED 1

oVe

18ETI-JULY 1980

SINPI,H1

connected to +5V. Motdr control inputs 2Xand 2Y (pins 2, 15, IC4) are connected to+5V via 560k resistors to give a slow forwardspeed. Following any collision, a signal fromthe manoeuvre circuitry asserts input '3'(pin 13, IC3) high and motor control inputs3X and 3Y are selected. The X and Y outputs(pins 2, 3 and 9, 10, IC8) from the man-oeuvre circuitry are connected to inputs 3Xand 3Y and these signals are used to steerHebot out of trouble. Following the man-oeuvre, control is returned to the next lowestpriority level which is currently high; in thiscase level 2 - slow forward.

Manoeuvre LogicThe manoeuvre logic has four inputs, one foreach sensor, and three outputs; two motorcontrol signals and 'avoid' (pin 12, IC11)which goes active (high) for a certain perioddetermined by adjustment of RV1 followingany collision. It is this signal which applied toIC3 causes Hebot to select control by themanoeuvre circuitry.

The sensor inputs use 40106 hex Schmittto add an extra degree of noise immunity tothe system.

Following any collision, pin 11, IC9 goeshigh causing capacitors C5, 6 to be dischargedvia transistors Q3, 2 and monostable timingperiods to be initiated.

The overall manoeuvre time is adjusted byRV1 while RV2 sets the duration of straightmotion before a turn is executed. If RV1 isfirst set then adjustment of RV2 will alter thedegree of turn. Hebot chooses forward orreverse and the direction of turn by exa-mining internal registers which 'remember'which sensor signalled a collision.

There are two registers to control manoeu-ver information, 'straight ahead' and 'turn'.These are made from parts of IC9 ('straightahead') and IC6 ('turn') which form bistableset/reset flip flops. For straight ahead control,the output is applied to motors via two 4016CMOS switches (IC8).

In the case of the 'turn' register, oneswitch is fed directly from the register whilethe other receives an inverted signal. In thisfashion signals of opposite voltage are appliedto the motors and Hebot turns.

,44

The 'turn' and 'straight ahead' signals areenabled by control pulses from monostabletiming circuit. These are kept out of phasefrom each other to prevent the outputs fromconflicting.

If there are 'too many' collisions withina certain period then pin 10, IC11 will go low.This output may be optionally connected topin 1, IC6 where it will cause Hebot toexecute a turn immediately following a colli-sion without any straight motion. The useful-ness of this strategy will depend on thesettings of RV1, 2 which may be optimisedfor different obstacles. The circuitry hasbeen designed to enable a flexible and versa-tile system to be developed and there may bemany changes which can be made to adaptHebot's behaviour to this environment.

The Second BoardAll the circuitry on this board is poweredfrom the plus and minus five volt supply.Although the junction of the batteries (0 V)is available, an artificial 0 V Is generated on-board by R2, 3, C2 and appears at pin 1,IC1. The op -amp is connected as a voltagefollower and merely provides a low im-pedance output to drive other circuitry.This feature enables the board to be operatedfrom a single supply ensuring a more flexiblesystem and also allows the remaining op -amps to operate normally even if the one sideof the supply is abnormally low.

The 'random walk' is produced by drivingthe servo -amps with signals from an astableoscillator formed by components R4, 5, 6,Cl and one of IC1's amplifiers. The out-puts are taken from Cl and the junction ofR5, 6 and appear at A and B. Resistors RI, 7protect the diode networks inside the CMOSmultiplexer chips IC4, 5 to which these out-puts will be connected. Note that the bottomof R6 goes to pin 1, ICI; effectively 0 V.Wire TrackingThe remaining two amps in IC1 and all of IC3together form the wire tracking circuitry en-abling the Hebot to follow a cable back to itsnest by detecting an AC signal. There are twoidentical input stages whose outputs are pins7, 8, ICI. An AC signal from the sensor coilsis coupled to the inputs (pins 6, 9, IC1) by

/NINO

ma

MPl.

Fig. 2. The manoeuvre logic.

capacitor Cx or directly. Each amplifieroperates as a current -to -voltage converter andproduces an alternating voltage output. Thedetection stages are identical. The signal atpin 8, IC1 is coupled via C3 to rectifiersDI, 3 and charges C5 producing a DC vol-tage which is proportional to the strength ofthe input signal from the sensor coils. Thisvoltage varies between -5V and approximately+1V and appears at pins E, F where it shouldbe coupled to pins G, H. Two of the amps inIC3 are used with resistors R16, 17, 18, 19to convert the output voltages from C5, 6 tosignals swinging between 0 V and +3.5 V suit-able for driving the motors forward via themultiplexers and servo amps. The signals ap-pear at pins I (X) and J (Y).

Hebot needs to know whether there is anyuseful signal at these outputs and this isaccomplished by measuring the averagevoltage across capacitors C5, 6. This signal ap-pears at pin 14, IC3. When it rises aboveabout 0.7 V (measured with respect to Q1emitter) transistor Q1 is biased 'on ' and thevoltage at its collector will fall towards -5V.This signal is input to the Schmitt trigger (pin9, IC3) and appears inverted at pin M. Anidentical signal appears at pin L. However,this output may be disabled by pulling pin Kto -5 volts. Resistors R25, 26 and capacitorC7 provide a bias voltage for the Schmitt trig-ger.

PhototropismThe circuitry around 1C2 enables Hebot todetect and steer towards a source of light. Thetwo input stages are identical. A current flowsthrough Q2 which is proportional to the inci-dent light. This is converted to a voltagewhich varies between 0 V and +3.5 V and isoutput at pin 1, IC2 (pin P). The output fromQ3 appears at pin Q.

The output levels at P (X) and Q (Y) aresuitable for driving the motors forward via themultiplexers and servo -amps. Resistors R27,28, 29 form a potential divider which drivesthe Schmitt trigger (input pin 9, IC2) whoseoutput is normally 'high' (at about +3.5 V).When the average voltage at P, Q rises aboveabout 0.5 volts, ie when Hebot sees light, theoutput of the Schmitt trigger goes 'low' (to

ETI-JULY 1980 19

PROJECT

9

6

5

R810M10M

R910k

8

R1010M

61110k

Fig. 5. Sound seeking and speaking.

about -5 volts) biasing off Q4 and causing thevoltage at its collector (pin T) to rise from-5 V to +5 V. This signal is repeated at pin Ubut may be disabled by pulling K to -5 volts.On Board Test FacilityThe remaining section of IC2 may be used togive a visual indication of operation of otherparts of the circuit. It is connected as a con-ventional inverting amplifier with an inputresistance of ten million ohms.

With the input (pin S) disconnected, theLED will glow at medium brilliance.Connecting pin S to pin V will cause it toglow brightly indicating a positive input,while connecting a negative input (pin R) willextinguish the LED (this input should be tiedto the negative rail when not in use).

Sound Generation & DectectionIntegrated circuits IC4, 5 enable Hebot todetect and generate sound. Both devices are

The pc overlay for the Manoeuvre and ControlBoard.

C3150n

DI

HOW IT WORKS

D3

C52u2

-Ve

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R12100k

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555 timers. IC4 will produce a positive out-put at pin X of monostaole period determinedby R44, C13 (about one second with thevalues shown) when triggered by a sound althe microphone, MIC1. The sensitivity of thecircuit is set by adjustment of RV3. The trig-ger input of the chip (pin 2, IC4) is normallyheld above the trigger voltage of one-third ofthe supply voltage by bias resistors R41, 42,RV3. Any sound picked up by the micro-phone produces an alternating voltage at Q5collector which is coupled to the trigger byC12. A loud noise will produce a signal ofsufficient amplitude to trigger IC4. Theoutput signal (pin X) could be used to throw

NOTES:IC1,3 IS LM324 (pin 4 IS +Ve, on 11 IS -Ve SUPPLY)01 IS 2N3904ALL DIODES ARE 194148

07110k

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Fig. 4. The magnetic loop followingcircuit.

Hebot into reverse, a spin, or just stop him inhis tracks.

IC5 produces a short burst of sound eachtime input Y is taken from -5 volts to +5volts. Each positive transition of this inputcauses Q6 collector to go low to -5 volts. Thissignal, coupled to Q7 by C14, R47 causes thereset input (pin 4, IC5) to be pulled to +5volts enabling the oscillator to produce ashort tone burst. Any digital signal may beinput to pin Y. If 'avoid' (pin 12, IC11 boardone) is connected, a tone will be producedeach time Hebot encounters an obstacle.The loudspeaker is AC coupled to IC5 toavoid excessive current flow. The frequencycan be changed by adjustment of R49 or C16.

20 ETI-JULY 1980

LISTOptions Board

RESISTORS (all 'kW 5%)

PARTSMISCELLANEOUSMIC1

R1, 7, 9. 11, 21, 35, 46 10kR2, 3, 4, 12, 13, 20, 22, 25, 26 LS1

27, 28, 30, 32. 36, 4585,31 82011 PCB, IC sockets, terminal pinsR6 4k7 LED1R8, 10, 33, 34 10NIR14, 15, 16, 17, 18, 19 2M2R23, 24, 44, 47R29R37R38R39R40R41. 42. 43

IMO470k560R3M31k515k150k

Manoeuvre and Confer)] BoardRESISTORS (alt '4W 5%)RI, 2, 3, 4, 18R5, 7, 8, 9, 1015,16, 17, 19R6, 11, 12R13, 14

R48 3k3R49 471. POTENTIOMETERSR50 2k7 RV1, 2

POTENTIOMETERS CAPACITORSRV1, 2RV3

220k100k

C1, 2C3, 4

CAPACITORSCl 68u tantalum

C5, 6C7

C2, 7C3, 4C5, 6

10u tantalum150n polyester2u2 tantalum

SEMICONDUCTORS01, 2, 304, 6

C8, 9, 12, 14C10

1013n polyester100u tantalum

05,7D1

C11C13

1u0 electrolytic1 u0 tantalum

C1,2C3

C15 1Cu electrolytic C4,5C8,9

SEMICONDUCTORS C701, 4. 5, 6 2113904

CB02, 3 NPN Phototransistor)TIL 781 CIO, 1107DI thru D7

2N3906all 1N4148 All CMOS must be '8' series.

ICI. 2, 3 LM324IC4, 5 555

The Options Board PC layout

any microphone (crystal orbalanced armature insertswork well)any loudspeaker (we used anBohm 1%inch loudspeaker)

any LED (we used TIL 2201

IMO

10k100k47k

IMO preset

10n polyester1,000u electrolytic4u7 tantalum10u tantalum

2N3904TIP 30TIP 291N4148CA31304532640521340116400164016B14584 (40106. 74014)

'I think the collision sensors aren'tsensitive enough.'

At the time this issue went topress, the details of Hebotchassis manufacture have notbeen finalized. Look for fullinformation in next month'sissue.

ETI-JULY 1980 21

Above, The overlay for the options board,full size artwork to follow next

month. Below left, Hebotworks just as well on

cats!

980 Alness Street, Unit 35,Downsview, Ontario, M3J 2S2(416) 661-5585

How we constructed our Hebot maze. Anything will work such as2 x 4 wood or 1" square steel tubing (expensive! We know).

The connections to IC3 and IC4. Mote the shorting link at the sideof IC3.

Our pickup coils and photosenscrs mounted conveniently on onePcb.

Brand New -Top Quality Performance & Value

HM 307 HM 312Single Trace DC -10MHz 5mV/cmIncludes TimesOne Probe

Dual Trace DC -20 MHz5mV/cm. Sweep Speeds40ns-0.2s/cm 8x10cm display.

Prices include FST and Shipping. Other modelsup to 50 MHz Bandwidth available. Prices andfull specs on request.

Available at your Local Dealer

22Circle No.25 on Reader Service Card.

ETI-JU _Y 1980

COLUMN

Service NewsDavid Van Ihinger returns from Koreaindustry that is virtually non-existent.

YOUR NEWS reporter has taken to theOrient to see how the other half of theworld lives. Here we are in Seoul, thecapital city of South Korea, where agood many of the electronic productswe use in Canada originate.

I visited Seoul, the capital, andPusan, a seacoast city: population ofthese citites just about equals that ofthe whole of Canada! Both cities areveritable beehives of activity, with shopscrowded together, row on row, streeton street. No space is wasted. Asidefrom arteries, streets are narrow, withpedestrians sharing with push -carts,bicycles, cabs and trucks, the very pre-cious space left for them betweenthe endless faces of storefronts. Eventhe back lanes become shopping malls,jammed both sides with temporary andpermanent shops, vying with the mer-chants out front for passing trade,offering fast foods, fruit, fountain pens,fish, French perfume, fresh water, fancyclothes, fiery flavoured delicacies, furni-ture, films, frilly lace, footwear, exoticfemales and other fabulous paraphena-lia. The quality of merchant and merc-handising is exceptionally high, particu-larly towards the central areas - thecompetition being so fierce. Althoughthere are a few department -type stores,upwards of ten stories high, the bulk ofbusinesses appear to reside in shopsaveraging about ten feet wide and notmuch deeper. This leads to smallerinventories, less variety and tighterspecialization down to a very few namebrands, extremely efficient layout anddisplay - total area usage as there is

absolutely no room for waste. It seemsthat every nook and cranny fronting toany form of pedestrian traffic is pluggedwith an enterprise, shoe shine stand,candy stall, sandal sales, cigarettelighters, sweet things, sour things, softdrinks, much resembling the CNEmidway on its busiest day. Most shopsin Seoul are open from early morning tolate at night, 365 days a year!

Getting It All FixedNow, what about service? Getting in-formation on TV and electronic servicewas most difficult. Sales people werenot ready to admit that their productwould ever require service, and no one

with some impressions of a service

could actually point your reporter toa genuine (by Canadian standards)service shop. Original factory replace-ment parts are very scarce, even im-possible to obtain, particularly im-ports. Substitutions are possible, buttime-consuming and often requiringcircuit alterations. Circuit manuals, dataparts lists, service tips, and factory -recommended modifications are vir-tually non-existent. What service is pro-vided by the local merchant is either ona carry -in basis or home service on foot,in central areas. I saw a new refrigeratorbeing loaded on a push -cart, the favoritedelivery vehicle.

Average house call $6.00 (equivalentCanadian cost of living to money value),plus parts. I did not see any colour testequipment, not even a oscilloscope. Itappears as though the service industryin this country has not kept pace withsales and that replacement of the pro-duct is their answer. I could not locateany service association.

TV broadcasts are only in black andwhite - channels 7, 9 & 11. Antennarequirements are quite simple, the mostcommon antenna appearing to be a

small 5 element yagi, broadly tunedacross the three channels. Altnough theAmerican forces also broadcast onchannel 2, very few antennas include itin their design. This channel of courseuses English.

Anyone owning a colour set has torely on video recorders or receptionfrom Japan. There are quite a few verti-cally -polarized UHF heads, equippedwith mast amplifiers, pointing towards

Sports programmes are a favourite of theKorean audience.

The sort of Korean electronics assembly lineon which your TV may have been made.

Japan. The high cost of this receptionequipment is written off by dividing itscost among neighbour -subscribers, a

practice not particularly approved bythe authorities, but somewhat resem-bling a form of bootleg cable system. Iflegitimate cable systems do exist, noone could tell me. Some hotels in Seoulare equipped with excellent master an-tenna systems, covering not only regu-lar broadcasts, but some print-outs aswell. This may have been CATV,however no one could confirm it oneway or the other.

Stations broadcast a lot of reruns ofAmerican movies and old programs,sound dubbed in Korean very cleverly -so cleverly it is hard to believe thatKojak ever spoke English! I must admit,it is oddly humorous to view and listen.

My overall impression of TV inKorea was of disappointment, parti-cularly from the point of view of a ser-vice technician. It surely demonstratedto me what can happen to an industrythat is not organized.

AnnouncementsElectronics Technicians Association,International Inc. Annual Meeting:July 11th & 12th at Iowa State Uni-versity, Ames, Iowa. Contact: RonCrow, D.E.T. (515) 294-5060, orDick Glass, C.E.T. (317) 241-7783.

International Society of Certified Elec-tronics Technicians (ISCET) announcerelease of a free booklet "Careers in theElectronics Industry" available from2708 West Berry, Fort Worth, Texas76109, self addressed envelope.

N ESDA/ISCET Electronics ServiceConvention and trade show August18-23 at the Galt House, Louisville,Kentucky.

Technicians wishing to take C.E.T.exams may obtain a booklet by writingto ISCET at 2708 West Berry, ForthWorth, Texas 76109.

Thanks to VEA Reporter for the plug.We'll try to warm up those arctic massesbefore we send them on down to you,next year.

ETI-JULY 1980 23

FEATURE

CAPACITORSAre you in a dilemma over dielectrics? or just confused by capacitors? then read on. Richard Mayburytakes a look at the often ignored subject of the dielectric material in fixed capacitors.

FIRSTLY WE SHOULD EXPLAIN that this article is notintended to be an in-depth study of the workings of thecapacitor, that has been done so many times before,usually punctuated by complicated formulae. This articleis designed to give an insight into the construction ofcapacitors, with particular reference to their dielectricmaterial (more of which later).

From our point of view (the capacitor users) the idealcapacitor will be physically small with as great a range ofcapacitance as possible. Any leakage (current pathsacross the plates) should be minimal. This capacitorshould ideally be stable with regard to both capacitanceand leakage, under as many adverse conditions aspossible. It should be able to operate with a largevariation of applied AC and DC potentials, current andfrequency, enjoy a long and healthy life and cost next tonothing.

Faced with all these constraints the poor old capacitormanufacturer may well be seen burying his head in hishands in despair, but compromise to the rescue, theideal capacitor does not exist as such - but you can betyour boots there's one available for the application youhave in mind.

Let's take a look at the (almost limitless) choice on themarket, and to what use they can be best put.

The first capacitors were possibly just two plates ofmetal placed close to each other, the insulating materialbeing air. (On a historical note if you've read Erich VonDannikens "Chariots of the Gods" you may be con-vinced otherwise. Apparently in the old testament thereare instructions for building an Ark (a kind of altar) youwere required to construct a wooden box, lined on theinside and outside with gold leaf, anyone touching thissacred shrine would be struck down by lightning: we'llleave you to draw you own conclusions about thesuitability of wood as a dielectric!).

A couple of miniature ceramic capacitors the value is stampedon the side, often a major source of confusion.

Air spacing is the oldest and simplest type of capaci-tor, it can still of course be found today, namely thevariable capacitors. We won't dwell too long on this justlong enough in fact to point out that the measurement ofdielectric quality uses air as the standard, air has adielectric value of 1 (a polystyrene capacitor has adielectric value of 2.5 at 50 Hz, so you can see that apartfrom its use Es the standard it's not too clever as adielectric material).

DISC CERAMICS

Sil.er TerminatedMor °bloc ChipCapacitor

SolderedTermination

PLATE ORSQUARE CERAMIC

Glass Flied- Epoxide Resin

Transfer %flooding

Resiliant Epoxide Resin'Protective Undercoat

Solder Coated Oxygen Free- Copper Wire Leads

Dia. 0 64mrn 0 05

Fig. 1. Cut -away diagram showing construction of CeramicCapacitors.

Far and away the most common type of capacitor inuse today is the Ceramic capacitor

The Ceramic CapacitorThe ceramic capacitor is available in several physicalshapes, and two distinct grades: low Permittivity (low -K)and high Permittivity (high -K). Both types are physicallysmall (small compared to other types of capacitor), bothare relatively fragile physically but there the similarityends.

High -K ceramics suffer large non-linear changes ofvalue with temperature and strength of applied AC/ DCfields (the capacitance will decrease as the voltage rises)the value will also change with frequency (up to 20% inthe 1 kHz -10 MHz range).

As High -K types are none too stable they find appli-cations only in non -critical positions ie. DC blocking,by-passing and de -coupling but these account for avery high proportion of all uses.

24 ETI-JULY 1980

Just a small selection of the multitude of capacitors available tothe amateur market.

Low -k CeramicsThese are the opposite of High -K types in many respects,low -loss, good temperature stability and wide frequencyand voltage ranges. In some cases they are deliberatelymanufactured to be temperature conscious for thermalcompensation in temperature sensitive equipment.

Ceramic capacitors are made in a variety of styles (seeFig 1), their shape often affects the frequency range, e.g.tubular ceramic operate up to about 50 MHz, disc orplate to 100 MHz, feed through to 500 MHz, and buttonceramic to 1000 MHz.

Because of the simplicity of their construction thecapacitance range of ceramics is usually towards the lowend (one or two picofarads (pF) upwards). The

Four 'low k' ceramic capacitors.

construction is often nothing more than a round disc ofceramic material, the two faces coated with a metallicfilm to which the connecting wires are attached. Thecapacitance will depend upon the thickness of the discand cross-sectional area of the metal coating. Theresulting device is then dipped into a variety of coatingmaterials to offer a degree of protection.

Plastic Film CapacitorsThere are three main types of plastic -film capacitors:Polystyrene, Polyester and Polycarbonate.

Polystyrene is probably the most common at themoment.

PLASTIC FILMDIELECTRIC

LEAD

METAL FOIL

ENTIRE EDGE OFFOIL SOLDERED TOGETHERALSO TO LEAD

Fig. 2. Method of forming Polystyrene capacitors, note thatentire edge of rolled foil is connected to the lead -outs.

PolvstreneThis type of plastic -film capacitor is constructed usinginterleaved sheets of polystrene film and metal (usuallyaluminium) foil, the beginning of the roll is staggered toenable the leads to be attached (see Fig. 2). In certainapplications, instead of a separate foil layer a thincoating of metal is deposited onto the plastic film directly(this technique applies equally to polyester and poly -carbonate types). The resulting sandwich of plastic andmetal foil is rolled tightly into a tubular shape (this tubemay then be flattened to suit a rectangular encapsulationwhich gives greater edge -on component packing de-nsity).

Polystyrene capacitors, easilydestroyed by excess heat.

Electrically the polystyrene capacitor has average -to -good characteristics, the voltage range can extend to650 V, they find many applications in tuned circuits,coupling frequencies of up to 100 MHz. The highervalues (1 On F and above) can be used for by-pass etc.

The polystyrene capacitor does have one or twodrawbacks; it's extremely sensitive to heat, not in thesense of capacitance changes but physically, they meltvery easily! They are also sensitive to attack from a widevariety of solvents and greases, so a great deal of careshould be taken with polystyrene capacitors, firstly whensoldering and secondly in their application to ensurethey do not come in contact with harmful chemicals.

ETI-JULY 1980 25

FEATURE

Polyester and PolycarbonatePolyester capacitors can be examined along withMylar, Melinex and polypropelene materials, they allhave basically the same dielectric properties, they all,however have superior electrical characteristics topolystyrene, particularly in the case of Polycarbonatecapacitors. All of the plastic -film capacitors (apart frompolystyrene) have excellent resistance to attack fromcorrosive or solvent chemicals.

Polycarbonate in particular seems to have become adefinite favourite among digital equipment manufac-turers, possibly due to their very high tolerance rating.They are usually a lot smaller physically, for a givenvoltage rating, than other plastic -film capacitors.

One last property of plastic -film capacitors is theability of some types to 'self -repair'; these aremetallized -film capacitor. In the event of an arc jumpingthrough the dielectric film (it will never be completelyimpervious) the area around the arc will vapourise thusclearing the fault, and reducing the possibility of anotherarc. This does not happen on any other type of capacitor,a dead short will usually result after such an arc.

C:=I MICAt I FOIL

GENERAL CONSTRUCTIONOF MICA CAPACITOR

Fig. 3. Construction of Mica capacitors, the entire assembly isthen dipped into a bath of fluid coating to ensure a hermetic seal,and prevent ingress of harmful chemicals.

Mica and PaperBoth these types of capacitor were once popular but nowhave largely disappeared from the amateur electronicsscene; they do however have specialised properties thatensures their continued manufacture.

MicaMica is a natural mineral which can be cut into very thinslices; a variety of methods are used in their manufacture(Fig. 3). Moulded Mica types are made from layers ofMica, interleaved with metal film, the range of capacit-ance of this type is about 10pF-100nF.

Silver Mica capacitors are noted for their very highstability and are often used in oscillators and filters. Theyare usually quoted as 5% tolerance or better and have avalue range of 5-3300pF.

Metal -clad Mica types are used in high power RFcircuits.

Resin dipped polyester capacitors.

Button Mica capacitors exhibit low inductance andare mostly constructed in stand-off or feedthrough style,the main applications being in UHF circuits. Finally thereare Dipped Mica types; these are dipped in a resincoating at below atmospheric pressure, and used wherereliability is the prime concern; values range from 10pFto 100nF.

PaperPaper capacitors are rarely seen these days except wherehigh voltage AC and DC currents are to be found; inthese situations paper is just about the best dielectric.

The method of construction is similar to the plastic -film type of capacitor, but instead of plastic the dielectricconsists of a layer of impregnated paper, the substanceused for the impregnation can be one of several naturaloils, waxes or synthetic resins.

As in the plastic -film types, the construction can be byone of two methods: metal foil or metallized film. Unlikeother types zinc is often used instead of aluminium. Theuse of zinc usually results in a device considerablysmaller than an aluminium type. The voltage range ofpaper capacitors is considerably larger than that of mostother types, often extending up to 4 kV.

Encapsulation of paper types usually consists of a thincoating of synthetic resin or metal cannister.

Electrolytic Capacitors

The difficulty of producing large value capacitors ishighlighted by the electrolytic, it is at best a compro-mise, for example the tolerance is often quoted as-20+100% or -50+100%!

Electrolytics fall into three distinct groups, the con-ventional type, most often encased in a metal cannister,the non -polarised electrolytic, usually a little larger thana capacitor of the same value, and finally the Tantalum, afairly recent newcomer to the capacitor field.

(At this point it must be said that there are severalother types of capacitor we have not dealt with. It is veryunlikely that they will be encountered by the averageamateur, however it might be an idea to take a look atthem in a future article.)

Getting back to the electrolytic capacitor, we'll dealwith the most common type first, the metal foil type.

26 ETI-JULY 1980

aUolisioara nialsimarsr miclhioemn

25 v 25 v 25 v

MO NNW>

<6>1ELECTROLYTICS

> NeiNir`I; U -4U-'d:

A selection of tubular metal -foil electrolytics, voltage is usuallyproportional to physical size.

Metal Foil ElectrolyticsElectrolytic capacitors consist basically of twoaluminium foils interleaved with an absorbant paper,and wound tightly into a cylinder. Contacts are providedby tabs of aluminium attached to the foils. The windingis impregnated with an electrolyte and housed in asuitable container, usually an aluminium can, which ishermetically sealed (see Fig. 4).

WOUND FOIL (PAPER IMPREGNATED)SECTION WITH ELECTROLYTE.)

CATHODELEAD

ALUMINIUMFOIL AND WIRES

WOUNDSECTION

HERMETIC SEAL(RUBBER OR RESIN)

ANODELEAD

ALUMINIUMCAN

Fig. 4. Electrolytic capacitors, use a similar method of construc-tion to Polystyrene capacitors, note that the start if the roll isstaggered to enable the lead -outs to be attached.

A dielectric layer is 'formed' electrolytically on thesurface of one aluminium foil which acts as the positiveplate or anode, of the capacitor. The electrolyte serves asthe second plate of the capacitor and also to repair anyflaw's in the oxide film when the electrolyte is polarised.The second foil, usually called the cathode, providescontact with the electrolyte. Since this film will have athin oxide layer, due to natural oxidation, it will alsopossess very high capacitance. The thinness of the ox defilm, and their high breakdown potential, is responsiblefor the very high capacitance per unit volume and highworking voltages of electrolytic capacitors.

Similar to the plain foil type of electrolytic is theEtched foil electrolytic, the aluminium foil on the anodeand cathode are chemically etched to increase thesurface area and hence the capacity, this results in a

ISome 'power' electrolytics in the background, tags are usuallyused instead of leads.

physically smaller device but has the disadvantage of notbeing able to withstand high AC currents, comparedwith plain foil types.

The capacitance value and leakage both increase withtemperature on foil electrolytics, leakage also increaseswith applied DC voltage, this increase becomes morerapid at voltages above its rated working voltage. Thiscan lead to excessive heat dissipation, and ultimately toits destruction. Most electrolytics are designed to with-stand short surges of up to 20% over the rated workingvoltage.

Some new miniature PCB -mounting electrolytics, for greater com-ponent density.

Non -Polarised ElectrolyticsThese capacitors are constructed using several foils inone winding and connected back-to-back. They areusually larger than polarised capacitors of equivalentvalue since double the foil area is normally required, the

ETI-JULY 1980 27

Just some of the multitude of capacitors currently available tothe amateur.

leakage current will often increase as a result. Thesecapacitors are most often used in speaker crossovernetworks or speaker coupling circuits. Values areobtainable from 1 u to 100u.Tantalum CapacitorsTantalum oxide is used as the dielectric. This has a muchgreater permittivity than aluminium oxide resulting inhigh value capacitance in a relatively small space, theywill normally be polarised.

There are three different types of Tantalum capacitor.These are the tantalum foil, similar in construction toordinary electrolytics. Solid tantalum, this uses

Miniature tantalum capacitors, small size, large capacity, but usuallylow working voltage.

manganese dioxide (a semiconductor) as the electrolyte,and a tantalum anode. These are often coated in epoxyresin or a polyester sleeve with epoxy seals. The thirdtype is the wet sintered tantalum, this type is rarely seenother than in specialised applications and can bemanufactured to a very high tolerance.

Tantalum capacitors have a much lower voltagerating than electrolytic capacitors, typically 3-100 V forthe solid type, up to 125 V for the wet sintered type andup to 450 V for foil tantalums. Tolerance is typically-20% to + 50%. Their small size makes them ideal fortransistorised applications.*

Latest Babani Books from Eli-.40111

Choosing andUsingYour

To order use the cardfacing page 44 or send to:

ETI Magazine,Unit 6, 25 Overlea Blvd.,Toronto, Ont., M4H 1B1

BP66 Beginners Guide to Microprocessors andComputing. $7.25 plus 30c post.

Aimed as an introduction to the basic theory andconcepts of binary arithmetic, microprocessor operat-ion and machine language programming.

BP67 Counter Driver and Numeral Display Projects.$7.25 plus 30c postage.

Numeral indicating devices have come very much tothe forefront and find increasing applications in allsorts of equipment. The book features manyapplications and projects using various types ofnumeral displays, popular counter and driver IC's etc.

BP68 Choosing and Using your Hi-Fi. $7.25 plus 30cpost.Gives an understanding of the technical specificat-

ions of equipment and the author's opinion of theminimum standards to look for. Also describes howto use your equipment properly.

BP69 Electronic Games. $7.25 plus 30c post.Contains a number of projects using modern IC's.

Contains two sections, the first with basic and simplecircuits, the second with projects for the moreadvanced reader.

BP70 Transistor Radio Fault -Finding Chart. $2.10plus 30c post.

Drawn up by the author from several years ofexperience, it will enable the most common faultsto be quickly identified.

Every_bodt's making moneyselling microcomputers.

Somebodies going to make moneyservicing them.

New NRI Home Study Course Shows You How to Make Money Servicing, Repairing,and Programming Personal and Small Business Computers

Seems like every time you turnaround, somebody comes along with a newcomputer for home or business use. Andthey're being gobbled up to handle thingslike payrolls, billing, inventory, and otherjobs for businesses of every size... to performhousehold functions like budgeting, envi-ronmental systems control, indexingrecipes, even playing games.

Growing Demand for ComputerTechnicians ...Learn in Your

Spare TimeEven before the microprocessor burst

upon the scene, the computer industry fore-cast over a 100% increase in job openings forthe decade through 1985. Most of them newjobs created by the expanding world of thecomputer. NRI can train you at home toservice both microcomputers and their bigbrothers. 'Wain you at your convenience,with clearly written "bite -size" lessons thatyou do evenings or weekends without quit-ting your present job.

No Experience NeededYou don't need prior training in elec-

tronics or computers to take this excitingnew course. NRI starts you with the basics,gives you a firm foundation to build on. Andyour personal counselor is always available,ready to help whenever you have questions.

Assemble Your OwnMicrocomputer

NRI training also includes plentyof practical experience. You perform

meaningful experiments building andstu ng circuits on the NRI DiscoveryLab. Then you build your own test in-struments like a transistorized volt -ohmmeter, CMOS digital frequency counter...equipment you learn on, use later inyour work.

And you build your own microcom-puter, the only one designed for learning. Itlooks and operates like the finest of its kind,actually does more than many commercialunits. But NRI engineers have designedcomponents and planned assembly so it

demonstrates important principles, givesyou working experience in detectingand correcting problems. It's the kind

of "hands-on" training you need torepair and serviceunits now on themarket.

Rush Card for Free CatalogSend the postage -paid card today

for our 100 -page, full -color catalog. It de-scribes NRI's new Microcomputer lechnologyCourse in detail, shows all equipment, kits,and lesson plans. And it also tells aboutother NRI courses...Complete Communica-tions with 2 -meter transceiver...TV/Audio/Video Systems Servicing with training onthe only designed -for -learning 25" diagonalcolor TV with state-of-the-art computerprogramming. With more than a millionstudents since 1914, NRI knows how to giveyou the most in home training for newopportunity. If card has been removed,write to:

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Education Center330 Progress AvenueScarborough, Ontario M1P 2Z5or telephone 416-293-1911

300W AmpIf you absolutely abhor clipping dist-ortion, like loud music, or simplywant to impress your friend, havewe got an amp for YOU. Our beastwill push 300W through a 4ohm loadwith only .3% thd.

Passion MeterA project for people in human relations(parties, etc.). The Passion Meterprovides a quantitative measure foryour level of excitement. Calibration ?Sorry, we couldn't find any metricunits for arousal.

Test GearPlanning to build up your lab? NextMonth we look at some basic test gearand how to choose it.

PASSIONMETERFINGER TESTING GOOD

Transistor TesterFor most transistor applications, theexperimenter is realy only concernedwith current gain and leakage. NextMonth we present a project whichenables you to measure those char-acterisitics.

FET SpecialThe Field Effect Transistor is a highimpedance device which finds appli-cations in RF circuits and sensitiveamplifiers. Next Month we presentselected circuits from the babani bookBP 39, 50 FET Projects.

Life Out There?For some time there has been a con-viction that life exists in other solarsystems. Next Month we look at what'sbeing done in this field.

S100 Bus SystemThe S100 bus system has been aninformal standard since it first appearedthe Altair 8800 (yes, it's been around).Next Month, we describe the basicsystem.

30 ETI-JULY 1980

FEATURE

ELECTRONICSIN THESTUDIOTim Orr - the man of a thousand circuits - takes us on a touraround the cables of a recording studio.

THE LAST DECADE has seen an enormous growth in thequantity of electronic hardware that is used in recordingstudios. The list of equipment now available includes 24 tracktape recorders, 48 channel mixers, computer assistedmixing, spectrum analysers and a whole host of elect-ronics effects gadgetry. These high technologysolutions have made the job of producing recordings mucheasier but the tasks now demanded of the studio engineerhave increased.

It is sobering to remember that the early Beatles'albums were produced in one day on a four track recorder.No matter how hard we try, technology cannot producemusic; it can only provide the 'tools for the job'. In facttechnology has in some ways, had a detrimental effect onmusic production with the idea that if you have sufficientrecording tracks to spare you can get it right on the final mixdown.

A Typical StudioA typical recording studio is split up into two working areas:the performance area and the control room - containing allthe electronics and associated hardware. The performancearea is soundproofed to provide about 80dB's of acousticisolation from the outside world. The walls, floor and ceilingare all made from very dense materials to absorb sound.The room itself is usually acoustically flat, having little orno reverberance or resonances. Often there are mobileacoustic baffles, (vertical sheets of board), that can bepositioned in between musicians to provide some amountof acoustic isolation between them. These are often usedfor drums. There is a studio talk back system so that thecontrol room can talk to the musicians or play themrecordings. The microphones plug into floor or wall socketsand are connected directly to microphone amplifiers in thecontrol room. A large double glass window separates thetwo halves of the studio.

The control room houses all the electronic equipmentneeded to produce the recording. All signals pass through amulti -channel mixer which is used to provide control overthe volume, tone and any special treatments that need to beperformed on a particular sound. The usual approach forproducing a recording is to build it up track by track so thatthe music is broken down into its basic ingredients, (i.e.bass line, melody, vocals, strings, drums), which are stored

. . . and now its time for a burn fromthe urn with a roundup of todays topfunerals around town!

A modern mixing console.

on a multi -track tape. This can then be mixed down by theproducer to get the required overall balance. The mixer canbe used to fade in and out various tracks and to provideequalisation.

Graphic EqualiserA Graphic equaliser is a very flexible tone control operatingover the audio spectrum. This spectrum is broken up intosegments, each being controlled by a slide, which canprovide up to 1 2dB of cut or lift. Thus it is possible to drawout, using the sliders, an overall frequency response which

ETI-JULY 1980 31

FEATURE

will be imposed upon the audio signal. The position of thesliders graphically display the frequency response curve.

sTUDIaTALK BACK

DOUBLE GLASSSOUNDPROOF

INDOW

FACKELD

ELECTRONICEFFECTS

NITS

MOBILE ACOUSTIC BAFFLES

VARIOUS MICROPHONES °RUM KIT

(5-o ob O

MIRES

TAPE DECKS RECORD12 INCH TAPEI DECK

Fig 1. A typical studio layout.

SOUND- PROOFEDPERFORMANCE

AREA

SOUNDPROOF

STUDIOMONITORS

ECDROING LAMP

Compressor/ExpanderTwo problems that are ever present are noise and over-loading. To prevent overloading of equipment you cansimply operate at a low signal level but this results in a poorsignal to noise ratio. To obtain a good signal to noise ratioyou should operate at a higher signal level but this willprobably result in overloading and distortion!

An enormous amount of programme material is listenedto on radio sets which typically have a reception signal tonoise ratio of between 40 to 55dB and which are used innoisy environments. Thus the programme sound level mustbe very tightly controlled. If the signal level is too large thenthe radio transmitter will be over modulated causing grossdistortion; if it is too small the signal will be lost in noise.Generally broadcasting companies try to limit their pro-gramme material to a range of about 16dB. Also whenrecords are cut the dynamic range must be tightly control-led as a disc can only provide 60dB (usually less) signal tonoise ratio.

LIFT

SLIDER FLATKNOBS

20HZ 0HZ cu

Fig 2. A graphic equaliser and response.

.12dB

-12dB20HZ 20K HZ

FREQUENCY RESPONSE

If the signal level is too large the cutting will breakthrough into its neighbouring grooves. Even if it doesn'tactually break through it can cause a material deformationof the master disc that produces a noticeable pre and postecho. When a disc is cut the general brief for the disc cutteris to get as large a cut as is possible without producing anycross talk and to do this the recorded material should nothave any nasty signal peaks.

OUTPUT

dBm+10

10

20

30

-40

50

-60

-60 -50 \-4 30 -20 -10

2 TO 1 EXPANSION NOISEGATE

-50dB THRESHOLD

+ 0dBm

2-1 COMPRESSION

LIMITING-10dB THRESHOLD

INPUT

COMPRESSOR/EXPANDER

Fig 3. Compander limits and response

Level ControlThere is a large selection of equipment available to controlthe signal level of programme material and these are knownas compressors, limiters and expanders.

A typical device will have controls that set the thresholdpoints, the compression and expansion ratios and theresponse times.

A limiter is a device that prevents the output signal fromrising above a set threshold. As the input signal attempts todo this, a voltage controlled attenuator turns the signallevel down. The effects of limiting are rather harsh and areusually only used to prevent overloading in some otherpieceof equipment. Compression is also used to reduce over-loading but it is more subtle.

If say, a two to one ratio has been selected then as thesignal level exceeds the threshold the output will increaseby only 3dB for every 6dB increase of the input. By usingboth a compressor and a limiter at once it is possible to runat 6dB below the maximum operating signal level for asystem and still handle signal excursions of a further 18dBwithout noticeable distortion.

When the input signal is very noisy as for example, atelephone news report, or an old film sound track, anexpander can be used to clean up the sound quality. Anexpander is a device that attenuates the signal when it fallsbelow a pre-set threshold. A two to one expansion ratioreduces the output signal by 1 2dB when the input signalfalls by 6dB. A more dramatic effect is a noise gate whichhas an expansion ratio of about 20:1 or even more.

The speed with which compression or expansion occursis controlled with switchable attack and decay times. Thisallows the user to select the best time constants for the jobin hand.

Another but more specialised type of signal level con-troller is the voice over or ducking unit. This enables a DJ toautomatically fade the music down to a preset level everytime he speaks. When he stops the music rises back to its

32 ETI-JULY 1980

original level. The attack and decay times for the duckingare adjustable.

Above: an Audio Design compander.

Above: an Audio Design voice over unit.

Noise ReductionThe signal to noise ratio of a professional tape recorder isabout 60dB, which is mainly due to the limitations of thetape. This is not good enough for professional recordings,particularly when many sound tracks have to be mixedtogether. What is needed is a system for improving theperceived signal to noise ratio. An expander does this but itdistorts the natural dynamics of the signal in that the signaldies away abruptly after it falls below the threshold. Asystem that overcomes this problem and which is widelyused in studios is the Dolby A system. The signal to berecorded is pre-processed with a low level compression.That is, low level signals are selectively made larger whilstthe high level signals are unaffected. The signal is thenrecorded on tape and in doing so tape noise is added.

When the tape is replayed a low level of expansionexactly complimentary to the compression previouslymentioned is performed. This reduces the effect of the tapenoise in the periods of silence but does not corrupt thesignal dynamics because of the complimentary compres-sion and expansion.

Also, the process is performed in four independentfrequency bands so that "breathing" effects are reduced.The advantage of using low level compansion is that thedistortion caused by it appears only on low level signals andis thus not very noticeable. Also low level compressionmakes very little difference to the maximum signal level. Animprovement of 10dB is obtainable using the Dolby Asystem.

Echo and ADTElectronic delay lines are often used to produce a widerange of effects such as flanging, chorus, automatic double

tracking and echoes. There are two methods of implemen-ting time delays, one is with bucket brigade delay lineswhich are useful for short delay (1 to 40 mS.) low costunits, and the second is with digital delay lines. These arebest used for 10 mS to 1 S. delay times in high qualityunits, (Usually costing $1500 upwards).

Fig 4. (Above) Block diagram of an echo unit.

(Below) The resuhing outputs.

nt LAVINjt:

Automatic double tracking (ADT) simulates the sound ofa second instrument playing along with the original. A timedelay of 10 to 40 mS is generally used and the delayedvoice is mixed in with the original so you effectively get twomusicians or singers for the price of one. To improve thenaturalness of ADT the time delay is slowly modulated,thus generating very slight timing errors. Another effectsimilar to ADT is 'chorus' where one or more delays linesare used with a slightly shorter delay time, (5 to 10 mS) thuscreating a richer, more complex sound structure.

Echo is often obtained using a digital delay line. Theinput sound is converted into a binary word with an ADC,stored in a large RAM and then converted back sometimelater into an analogue voltage using a DAC. The memorysize is often very large. Take, for example, an echo unitwhich has to have a 60 dB dynamic range, a 10 kHzbandwidth and an echo length of 1 second. The systemmust be 10 bits wide and have a clock speed of 25 kHz,thus the number of bits of memory needed is 25K x 10 =250,000 bits, which would be 250 1K RAMs costingabout $3.00 each!

FlangingFlanging is a popular effect that is implemented using acomb filter. The comb filter response is produced with ashort delay line, (1 to 10 mS) where the original anddelayed signal are mixed together. This generates afrequency response which has a series of linearly spacednotches, the spacing of these being inversely proportional

ETI-JULY 1980 33

FEATURESPEED

IAUPpuTN

DEPTH

TIME DELAY MODULATION

INPUT OUTPUT

Fig 5. (Above): Flanging and how it is obtained. Below is shown thefrequency response of a comb filter.

OUTPUTINPUT

EFFECT OFREGENERATION

LINEARFREQUENCY

to the delay time. By applying feedback around the delayline, the comb becomes more peaky and so provides morecolouration of the sound. The delay time is slowlymodulated and this produces an interesting mobile colou-ration of the sound. Flanging and phasing are oftenconfused as they are both produced by comb filtering.Flanging uses a time delay and generally has lots ofnotches, sometimes as many as 50, whereas phasing usesphase delay and usually has only 2 or 3 notches.

ANALOGUETO DIGITALCONVERTER

ADCDATA

RANDOMACCESSMEMORY

RAM

I XED WRITING SPEED

DATA

DIGITAL TOANALOGUECONVERTER

DAC

Fig 6. Digital pitch shifting techniques.

CEDE

AUDIOOUTPUT

INPUT WAVEFORM

OUTPUT SHIFTED DOWNONE OCTAVE. READINGSPEED IS ONE HALF OFWRITING SPEED. NOTETHAT C AND D HAVEBEEN DISCARDED

OUTPUT IS SHIFTED UPONE OCTAVE. READINGSPEED IS TWICE OFWRITING SPEED. NOTETHAT ABCD HAVE TOBE REPEATED TO FILL INTHE TIME GAP

VARIABLE READING SPEED

Pitch ShiftingIt is now possible to transport the pitch of an instrumentusing a pitch shifting device. The shifting is not perfect, butit is good enough to produce useable harmonies. Theoperation is as follows. The input signal is converted into abinary code and written into memory. At the same time thememory is read, but at a different speed and this data isconverted into the audio output using a DAC. If, say, thereading speed is twice that of the writing speed then theoutput will be transposed up an octave in pitch. There aremany problems to be overcome. First, the output must notbe significantly delayed. Second, the time varying infor-mation of the output must rapidly track the input, that is,

A B C

/

E

DISCONTIN

DISCONTINUITY

Aoh.B._C+D A B C _ D_

11 ii aV f V V t

DISCONTINUITY DISCONTINUITY

Fig 7. Pitch shifting in practise.

the melody should be the same, but the pitch transposed.To satisfy these conditions the memory size should berelatively small (20 to 40 mS). Take the case of the uptransposition of one octave. If the reading speed is twice asfast as the writing speed then each segment of sound willhave to be played twice, otherwise gaps would appear.However, when the transposition is down by one octave,then half of the information cannot be read in time and sohas to be discarded. Pitch shifting units are usuallycontinuously variable over the range of plus or minus oneoctave.

SPEECHINPUT

ANALYSING 2 QUADRANTFILTER BANK MULTIPLIERS

SYNTHESIZINGFILTER BANK

BROADSPECTRUMOBTAINEDBY ANALYSINGSPEECH

TYPICALLINESPECTRUMOFEXCITATION

VOCODEROUTPUTSPECTRUM

OUTPUT

UITY

- EXCITATION INPUT

EFFECTIVELY THE VOCAL TRACTFREQUENCY RESPONSE

FREQUENCY

jl

11111111111111HI FREQUENCY

FREQUENCY

Fig 8. A representation of the Vocoder principle and waveformsexpected.

34 ETI-JULY 1980

VocodersA vocoder is a device for producing a cross product of twosounds. If the two sounds are speech and an electric organ,then the resultant sound output is a talking organ. Whenwe speak we produce a buzz in our vocal chords that isacoustically filtered by our vocal tract. The buzz becomesarticulate, it speaks. The vocoder uses a filter bank toanalyse the speech so it can determine the time varyingfrequency response of the vocal tract. It then synthesises amodel of this frequency response using a second filter bankplus some multipliers. The excitation signal (the electricorgan), is then filtered by this model and so becomesarticulate. The vocoder output has the melody and har-nonics of the excitation signal, but the time varying broadspectrum (the articulation) of the speech.

Above: a typical portable mixing unit. This one is produced byStudiomaster and will mix sixteen channels into eight.

MixersThere is a wide variety of mixers on the market today,ranging in price from $40 to $60,000. Basically, the moreyou pay, the better the product. A mixer is composed ofinput and output channels; for example a 16 into 8 devicehas 16 inputs and 8 outputs. A typical input channel hasthe following controls. An input gain switch so that lowlevel signals from microphone sources up to high level

Fig 9. The frequency response of a chorus unti which employs threeflanging units without regeneration. The scope picture wasobtained using a swept sine wave oscillator set to run the audioband.

Above: the EMS Vocoder 2000, a very popular unit and one whichthe author helped to design in his days at EMS.

studio signals can be accomodated. An overload lamp or aVU or PPM is usually provided so that the signal level maybe monitored. Next is a tone control section, perhapsconsisting of Bass, Middle, Treble and sometimes a fewparametric control functions. Many mixers also have anecho send control so that reverb may be added to thatchannel. A foldback control is often included. This is aninternal mixing system so that a few tracks can be groupedtogether and fed back via head phones to the musicians.

A pan control enables that channel to be sent to either ofthe left and right output groups. Routing switches are usedto connect a particular channel to any output group. A levelslider, always at the bottom of the channel allows theoperator to fade in and out the sound from that channel?You might get a nasty surprise! You won't if you have got aprefade listen switch. This connects the signal at the top ofthe slider to some monitoring device, so that the operatorcan have a sneak listen to a channel before fading it up andperhaps ruining the output.

To produce a controlled mix down the operator will needto be very skilled and possibly he will need ten pairs ofhands!

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That's the JensenA-124 Car Stereo PowerAmplifier, all right. Dis-tributing an F.T.C. Con-tinuous Average PowerOutput of 100 watts into4 ohms.

Not only does ithave plenty of power todispense, but it alsoknows just how to deal itout. To get the very mostout of your system. Anddo the very most for yourmusic.

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When switched tobi-amp, this amp dis-plays its keen sense fora balance of power. Two10 watt output-trans-formerless amplifiersdrive the tweeters andmidrange drivers forclear high frequencies.At the same time, twohefty 40 watt OTL ampsin this unit distribute theforceful power needed toget full, low -distortionbass from the woofers.

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It's instantly outputshort-circuit proof...justone of the many built-inprotection features. Andthe unit comes completewith 15 meters of lowcapacitance shieldedhook-up cable to eliminateRF interference.

So get the most outof your music...by gettingthe most out of your carstereo system. With theJensen A-124 Amplifier.

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New dbx Recording Technology Series"dbx Model 224 Type II Tape Noise Re-duction System, a simulataneous en-code/decode system that provides upto a 40 dB increase in useable dynamicrange. It is suitable for use with 2 -headrecorders and provides full monitoringability with 3 -head recorders. Thesystem also features a decoding functionfor specially encoded dbx Discs, of-fering full dynamic range and noise -free playback."

dbx Model 21 Disc Decoder"The dbx Model 21 Disc Decoder canbe added to any good home stereosystem for decoding the newly intro-duced dbx Digitally Mastered FullDynamic Range Recordings, as well asdbx Encoded Discs mastered using ana-logue master tapes or direct -to -disc re-cording techniques.

"For the first time, phonograph re-cords can reproduce the full dynamicsof a live performance without recordsurface noise. Use of dbx encode/de-code technology allows music to be re-produced with exceptional clarity andrealism, against a background of silence- sound that is virtually indistin-guishable from that of the master tapefrom which the dbx recording is made.

"The dbx Model 21 Disc Decodercan be used with any preamp, integratedamplifier or receiver which has a tapemonitor function, or it can be con-nected between the outputs of a pre-amplifier and the inputs of a poweramplifier. Suggested retail price is

$189.95."

AUDIO TODAY doesn't usuallyopen with a product news item; suchitems usually appear under a separatesub -head, as do letters. It's also unusualto reprint a manufacturer's press releaseverbatim. However, when something

Our Audio Editor Wally Parsons is enthusiastic about dbx andexpllains dynamic range.

exceptional comes along, an exception The two are not the same. And that"phonograph records can reproduce thefull dynamics of a live perfromance".

Audio News No promise of magic, no little black boxA word about press releases. Dozens that will deliver the ultimate in fide -of these come across the various desks lity from the $295.95 super-fi pur-at ETI every month. Only a few of these chased at the discount mail-orderprove newsworthy enough to print, and house. However, the promise is held outit's interesting to note that many of the that if your equipment is capable ofleast newsworthy are put out by people delovering a full dynamic range, dbx canwho think it's cheaper than buying ad- supply the goods to be delivered.

must be made, and this is it.

vertising. But even those which are usedare usually rewritten, either to tonedown the goshwowgeewhizboyoboyo-boy tone which is so popular, or tomake them literate.

However, in the case of those releasesissued by BSR Canada, distributor ofdbx products, this hasn't been neces-sary. Usually, the only reason I rewritethem is either to conserve space, orbecause I prefer this column to havemy own personal stamp.

Notice that dbx does not claim thatreproduced sound is indistinguishablefrom the original performance; it is in-distinguishable from the master tape.

The Why and How of it allCharter members of Professor Parsons'Audio Today Show and Tell Club willrecall that in February and March oflast year I dealt with the subject ofnoise and dynamic range.

It should be understood that thereare only two real requirements for widedynamics, from the standpoint of thereproducing chain, that is, from the pro-gramme source, e.g. records, to theloudspeaker/listening environment. Thesystem must be capable of developingsufficient acoustic power to match thehighest level to be reproduced and at

The dbx Model 21 Disc Encoder may well allow records keep up with modern equipment.

ETI-JULY 1980 39

COLUMN

the same time the noise introduced inthe chain must be below audibility at allfrequencies.

Until about 1970, the limiting factorwas in the reproducing chain. Bookshelfspeakers were quite popular, but wereincapable of producing truly high soundlevels, and even at their limit requiredenormous amounts of electrical power.I recall calculating the power requiredto drive one popular speaker to a soundlevel of 110 dB, and came up with afigure of 10 kilowatts. But even if suchpower levels were available, it wouldhave been futile, since continuousoperation above 50 watts would haveburned it up.

At the same time, a signal to noiseration of 50 dB from a phono preampwas quite remarkable, and seldomachieved, especially with the very lowoutput levels delivered by the betterpickups.

In fact, it was standard conventionalwisdom up until that time that thephonograph record was superior to anyequipment available to reproduce it.

The March of ProgressIn the meantime, the availability of highspeed high power transistors at a rea-sonable price and improved circuitryresulted in the introduction of morehigh performance high power amplifiers.Today it is possible to purchase even aconsumer class receiver with 250 wattsper channel output, and an 800 wattunit is now available as a basic singlechannel amplifier. Couple this with agreater understanding of rationalspeaker design, which has producedmore sensitive speakers, and we have thecapability of producing truly awesomesound levels.

Similarly, improvements in pickupshave produced higher performancelevels with, in some cases, greateroutput levels, coupled with preampswith even lower noise levels than adecade ago.

As a result, the record itself is nowthe limiting element in the system.

There is a limit to the maximumlevel which can be cut on a disc. Thereis also a lower limit to the noise of thegroove itself. Even if this were to benegated by some wondrous new ma-terial, and cutters of unlimited powerhandling capability, pickup tracing capa-bility and preamp noise would againbecome the limiting factors. The lawsof diminishing returns are setting in,and it makes sense to try a differentapproach.

The dbx Model 224.

The SolutionIn theory, there is a simple answer to allthis. Just as frequency response is

shaped to utilize better the charac-teristics of the medium, so can thedynamic characteristics. This is the dbxapproach.

Essentially, dbx has compressed thedynamic range during the record pro-cess, so that dynamic peaks are belowthe maximum permissible level, and thelowest levels are above the noisefloor. By itself, this might be all rightfor television and movies, but it's justthe opposite of increasing the dynamicrange, right? But if we expand the dyna-mic range in an exactly complementarymanner on playback, we restore the ori-ginal dynamics.

To be precise, dbx compresses every-thing by a factor of two to one and ex-pands it by the same amount. Thus,a 10 dB difference is recorded as 5 dB,then played back at 10 dB again. Andan 80 dB difference is recorded as only40 dB, then expanded to 80 dB agaun.A 40 dB range can be handled easilyby any record manufacturer you canname, while 80 dB is impossible nomatter what pains are taken. (see Fig. 1)

Newness?Of course, compressors/expanders(Companders) are not new. What is new is themanner in which it is used. Earlier

MASTER TAPE SIGNAL

+15

-20

10048 INPUTDYNAMIC

RANGE

-40

devices had problems in controllingattack and release time, resulting inpeculiarities of reproduction, such as"pumping" effects. What was neededwas a precision companding system.

The other difference lies in the useof a totally linear companding curve.Common practice in the past has beento use manual compression only on thelower level material, along with automa-tic limiting on the peaks. Some attemptsto compensate for this have met withvariable success, depending on how thethresholds and the expansion rates usedon playback corresponded to the re-cording characteristic. Sort of a dyna-mic counterpart to attempting to equa-lize manually to an unknown curve, likewe did in the early fifties.

This system works. And it workswell. Unfortunately, the decoder cannotbe used on standard discs, and dbx discswill not reproduce satisfactorily withoutthe decoder.

Whetherclosely related to the compatibility pro-blem, and how this is handled by themarketing people, as well as dealers andvarious scribblers. I would like to see ithappen.

This is why the next few columnswill deal with this subject, and a de-tailed feature article is in the works.

Stick around, kiddies; this promisesto be fun.

Continued on page 63ENCODED DISC SIGNAL

TRACING10 DISTORTION

+7 5

0

42

10

DISC-45 SURFACE NOISE -45

DECODED DISC SIGNAL

100 05 OUTPUTDYNAMIC

RANGE

Fig.1. Diagram depicting the combination co signal compression during encoding and expansionduring decoding that results in surface noise reduction and dynamic range retention on dbxencoded discs.

40 ETI-JULY 1980

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ETI-JULY 1980 Circle No. 11 on Reader Service Card. Circle No.13 on Reader Service Card. 41

FEATURE

THETESLACONTROVERSYIt is not doubted today that Tesla's name ranks with the major early researchers into the nature of electricitybut some people claim that much of his work has never been made public. We look at his life and career.

BY THE BEGINNING of the 1880s, electrical machineswere finding their way into both the commercial anddomestic fields. Although the nature of AC was under-stood, practically all motors and generators were DC.Electricity was becoming accepted and arc -lamps, eIec7tric lifts, photo -flood lamps and a wide variety of otherdevices were appearing.

In 1882 however, a young man Nikola Tesla who hadbeen born in Smijan in what is now Yugoslavia, startedto devote his undoubted talents to investigating AC.Tesla had the unusual flair for mental visualisation ofhighly complex ideas, a virtue shared by Faraday whowas also working at that time.

At the end of 1883, Tesla exhibited a working model

Fig. 1. Diagram used by Tesla in "The Electrician" to explainhow a rotating field may be produced by a poly -phase system.of an AC machine in Paris. (Figure 1 is one of Tesla's ownpictures.) He then began a campaign hopefully topersuade the emerging electrical giants, such as theContinental Edison Company, that AC transmission wasmore efficient than DC and this resulted in a job offer towork with Edison in America. A chance soon came, therepair of DC generators in the ocean-going steamer"Oregon," for him to show his skills.

His work must have been good as he soon becameEdison's chief assistant.

A few years later Tesla set up his own laboratory fromwhich he finally reported (in 1888) the electromagneticrotary field which enabled three-phase power transmis-sion to be implemented. Shortly after this, GeorgeWestinghouse, of Westinghouse Electric Co., boughtinto Tesla's interests and built a hydro -electric system(see Fig. 2) of enormous proportion at Niagara Falls.

Tesla was a man of great generosity. It is said he toreup a contract binding Westinghouse to pay him $1 2million - saying that it was more important for theNiagara plant to keep the home -lights burning than for

Fig. 2. Sketch of turbine anddynamo installed at Niagara Falls:5000 horsepower at 2000 V.Ten units were installed. Theyconsumed 26,000 lbs of, waterper second. Turbine (TS) shaftwas 140 feet long of 38 in dia-meter. Penstock (P) delivers waterto the turbine (T).

Westinghouse to become bankrupt because of a debt tohim.Tesla and RadioNotwithstanding his already significant work in powerelectrical engineering Tesla turned to thoughts of higherfrequency (RF) currents - higher by far than the typical100 Hz limit of power generators of that time.

The pioneers of radio had shown how a spark dis-charge, produced with an inductor and capacitor(Leyden jars to begin with) was finally proven to be anoscillatory process lying typically in the radio frequencyband. Rigs that produced such discharges continued tobe developed. The addition of a vibrating bell -likecontact or spark -gap discharge arrangements produceda continuous train of discharges. When step-up trans-former action was also incorporated, the Tesla coil wasformed. (Another name is the Ruhmkorff coil.) Figure 3is a 1910 Tesla apparatus

,,,,,,,,iirinVIIMM,MArr rldf.

iiiiiii$111011)11* /11110-.r [n '11111]

4111111ln II

Fig. 3. Modern (at least in 1910) Tesla coil apparatus.

42 ETI-JULY 1980

It was the spectacular things Tesla did with his radiofrequency extremely high voltage generators that gainedhim so much fame. At a lecture to the American Institu-tion of Electrical Engineers, given around 1891, hemade a memorable impression being reported at thetime as

"his work places Tesla among the greatest of ourpresent-day scientists and inventors, such as Edison,Graham Bell and Thomson."

Made His Mark With SparksInvitations poured in for his spectacular displays withman-made lightning and RF discharges. His equipmentused two kinds of generator.

The first was a 384 pole AC dynamo running at 50revolutions per minute to give 19.2 kHz. The other was aRuhmkorff-type induction coil used with a condenser(capacitor) and a spark gap. This produced the thenamazing half a million volts at "scores of thousands ofcycles per second". It was the latter that impressed hisaudiences, for Tesla "brandished flaming swords like anarchangel" - see Fig. 4 (or should it be arc -angel! -Ed).

Fortunately for everybody these RF discharges were

Fig. 4. Tesla amazed the scientific world in 1893 by holding glowingtubes aloft without any electrical connections being made to thetubes.

not lethal but Tesla said when about to try them out forthe first time (experimenters were naive to say the least),"it was as if / were poised to jump from BrooklynBridge".

Demonstrations included drawing arcs between astring of people, as recorded, Fig. 5, in a contemporarymagazine. Another was to make Geissler tubes (glasstubes filled with rarified air but having no electricalcontact with external circuits) glow whilst suspendedbetween, but well free of, the poles of high high -voltagetransformer.

In his 1899 he built a huge experimental barn atColorado Springs in Colorado - 30 metres long and 71/2metres wide on top of which was a 25 metre towersupporting a 60 metre mast. At the top was a 1 metrediameter copper ball.

He subsequently proved the earth is electricallycharged at a high potential. The Los Angeles Free Pressreported visionary ideas not yet exploited - use of theearth's resonance energy and the launching of waves ofelectrical energy to transmit power to places remote

Fig. 5. A contemporary print of Tesla's experiments conductedin Berlin in 1894.

from generators. There was talk of charging the earth toproduce tremendous voltages and of terminals to extractit. Tesla is said to have 'lit 200 incandescent lamps at adistance of 26 miles'. It is said his ideas failed to beexploited by commerce because the transmitted elec-tricity could not be charged for.

Powerful Secret?Tesla died in 1943, his last work being on the use ofcosmic rays as energy sources. The Free Press reportclaimed that the FBI seized his papers and confiscated allof his reports.

Did Tesla have a unique and powerful secret? Hecertainly was a visionary, perhaps he did discoversomething great that is being withheld.

It has been suggested that the Russians have recentlyfound out how his way-out experiments were done andin doing so have tapped some new form of energy.Frankly we doubt if there is any truth in the suppression- or rediscovery - of his work but a lot of people do notagree.

Today he is truly acknowledged. His name is used asthe now adopted unit of magnetic field insensity andmost laboratories possess Tesla-coils for ionising gas inevacuated tubes..

r ekr;;iiNtli.rNl `LInvot

Fig. 6. This print of 1894 shows the laboratory equipment usedin Tesla's experiments.

ETI-JULY 1980 43

The 'wired -city' concept has a great futurein Canada. One day you'll be able to haveyour own copy of ETI transmitted to you inyour home via facsimile reproduction.

We're still waiting.In the meantime, you're left with the

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44 ETI-JULY 1980

The Fun of Electronics Geiser

It's supposed to be an erasable memory chip - but I'vebeen at this for over half an hour ...

ELECT1ZON I C. GAMES.

,ro® 1...."/

46.,= t... ..... ... .... ...S.

This is our most realistic model;as soon as its complex circuitrysenses that it is losing a game, itswitches to the 'cheat' mode ofoperation.

Ei

What do you mean, 'QWerzmatronicisoram' is too long aname for an electronic component - that's just theAcronym.

My regular remote control is being repaired, so they gaveme this loaner.

poreI bought this calculator because it was supposed to be ableto execute loops, and so far, I haven't even been able toget it to roll over.

Like I was saying Harry, thereare alot of good reasons forgrounding your antenna mast.

\

ETI-JULY 1980 45

PROJECT

PHOTOGRAPHICTIMERThis project should appeal to the photo enthusiast. Use it to do your enlarger timing

OUR PHOTOGRAPHIC TIMER is a useful project withsome unusual features. !t has two fully variable ranges,covering 0.9 seconds to 10 seconds and 9 seconds to100 seconds. The unit has a relay output for turning theenlarger on and off, and is battery powered. Timingperiods are initiated by pressing a start switch, andeither end automatically at the end of the pre-set timingperiod, or they can be aborted part way through thetiming period by pressing a RESET switch.

Power SavingThe most unusual feature of the timer is that itconsumes power only during the actual timing period.This feature makes it legitimate to use a battery powersupply, which in turn increases the unit's versatility bymaking it fully portable and suitable for use as ageneral-purpose short - period timer. The unit has a

RV1TIME

How to wire the 'TIME' pot the'TIME SET' switch.

F ROMPIN10

F ROMPIN13

F ROMPIN12 FROM

PIN11

TIME SET

FROMPIN17

FROMPIN18

built-in LED (light -emitting diode) that illuminates duringthe timing periods.ConstructionMost of the circuit is built on a PCB, and constructionshould present no problems if you follow the overlaywith care. Be sure to fit the two diodes, the two elec-trolytic capacitors, the LED and the IC the right wayround. Take extra care when doing the interwiring,especially to SW1.

When the construction is complete, double-check allwiring and then give the unit a functional check.Connect the battery supply, press the START switch,and check that the relay and LED operate and turn offagain automatically at the end of a pre-set period. Themaximum timing period can be pre-set to precisely 10seconds on range 1 via RV2, and to 100 seconds onrange 2 via RV3.*

TIME

TIME SET 1 CRESET

LOW10sec.

HIGH

100seciIn.

NE PHOTOGRAPHIC TIMER

46 ETI-JULY 1980

Co-v RLAOUT 1

NOTE:IC1 IS NE555D1&2 ARE 1N4001LED1 IS TIL220

SY/1 RANGES:1 = 0.9 - 10 SECONDS2 = 9 - 100 SECONDS

R122k

R21k0

R322k

A D1RLA12V

>12OR

D2

C1100n

PB1RESET

The circuit diagram for the timer.

2 7

3

ICI6

R4100k

RV1IMOTIME

SA lb.

SW14

1

IC2 +C3

TT10u

HOW IT WORKSThe photographic timer is designed around asimple and inexpensive IC known as the 555timer. Fig. 1 shows the circuit and waveforms ofa simple manually -triggered timer built aroundthis IC. Here, trigger pins 2 and 4 are normallyheld high by Ra and Rb, and output pin 3 is low.When a brief negative -going trigger pulse isapplied to pin 2 of the IC, via the push-buttonPBa, a timing period is initiated and the pin 3output terminal immediately goes high and Castarts to charge towards the positive supply railvoltage via Rc.

After a delay determined by the values of Caand Rc, the Ca voltage reaches 2/3 of the supplyvoltage value, and at this point a switchingaction is initiated within the IC in which outputpin 3 switches rapidly to zero volts and Ca isdischarged, thus completing the timing cycle.Note that the timing cycle can be aborted partway through, if required, by applying anegative -going pulse (by briefly closing PBb) topin 4 of the IC.

Our photographic timer is a modified versionof the basic Fig. 1 circuit. Look now at the fullcircuit diagram of our timer. Here, the output ofthe IC is used to drive relay RLA, which has twosets of N.O. (normally -open) contacts: one set ofcontacts is in series with the circuit's supplyleads, and the other set is used to give outputcontrol. The circuit's START pulse is derived

PIN 2(PBa)

PINS(OUT)

PIN 7(Ca)

OV

OV

OV

RV210kSET10 secMAX

RV3

NkT

100 secMAX

R556OR

tiL ED1

0PR2START

RLA_

6V

6V

from the positive supply line via R1 and C1, andthe timing periods are determined by the valuesof C2-C3-RV1-R4, which can be switch -selected via SW1.

The timer operation is initiated by momen-tarily closing PB2 and thereby briefly connec-ting the positive supply to the circuit. At theinstant that the supply is connected, C 1 isdischarged: Consequently, trigger pin 2 is heldnegative relative to the supply line at thisinstant, and a timing cycle is immediately in-itiated. As the timing cycle is initiated relay RLAoperates and contacts RLA /2 close and bypassswitch PB2, thus maintaining the supply con-nection to the circuit once PB2 is released. Atthe end of the timing cycle RLA turns off andcontacts RLA /2 open, thus breaking the supplyconnections to the circuit. The circuit thusconsumes no current when it is in theSTANDBY mode.

Pre-set pots RV2 and RV3 are switch -selectedto connect to modulation pin 5 of the IC, andenable timing periods to be varied over a limitedrange to compensate for variations in the actualvalues of electrolytic capacitors C2 and C3 andto enable precise maximum timing periods tobe obtained.

Fig. 1. The waveforms on the left arethose produced by the simple circuit onthe right.

OUT

PBaSTART

ETI--JULY 1980 47

PROJECT

+12V

PB2

RLA OUTPUTi

PB2

LED Anode

RV1

PB1

RV1 (WIPER)

SW1a (COMMON)

SW1b (COMMON)

SW1b (1)SW1a (1)

LED CathodePB1

OV

SW1a (2)SW1b (2)

Above left: The overlay for the PCBAbove Right: Inside the box.Below Left: The PCB with com-ponents in place.Below Right: The PCB foilpattern shown full size.

PARTS LISTRESISTORS (All 5%,

R1 22kR2 1kR3 22kR4 100kR5 560R

CAPACITORS ,

Cl 100n (0.1 uF) polyester, mylar etc.C2 10u 1 6V electrolytic, PCB mountingC3 100u 16V electrolytic, PCB mounting

POTENTIOMETERRV1 IMO linear, rotaryRV2, 3 10k preset

SEMICONDUCTORSIC1 555 (NE555)D1, D2 1 N4001 silicon diodeLED1 TIL 220

MISCELLANEOUSSW1 Miniature toggle, two pole, two wayPB1, PB2 Push button switches, push -to -makeRelay 12V coil with minimum resistance

of 120R. sub miniature typewith at least two 'normallyopen' contacts (change -overcontacts will contain a normallyopen pair)

PCB Pattern as shownBulgin mains plug and socket, 2 -off HP7 4section battery holders, 8 -off HP7 battery. Caseto suit.

48 ETI-JULY 1980

Bill Johnson advocates HAPPY FLIEIT SEEMS to me that amateurs in Canadahave a distinct advantage over other amateursaround the world - we have not one, but twonational organisations to represent our in-terests to government and the public. Despitethe constant bickering and attempts at one-upmanship between the two, amateurs inCanada are taking giant strides ahead at a pacegreater than our confreres in other countries.So much so, in fact, that it would seem thatsomeone, somewhere in authority, has our in-terests at heart, and is doing his utmost topromote them. I wonder who that could be!

For many years, amateur radio led a darkexistence. It was a hobby unknown to thosewho were not in its ranks. Almost a secretsociety. Over the last few years, however, wehave not only gained valuable extra privilegesfrom the government in the form of modesof emission, such as packet radio, but it seemsthat all government departments recognise theimportance of amateur radio as a communi-cations resource. With the new DigitalLicense, we find that amateur radio is notonly the resource of hobbyists, but of Univer-sity researchers also. Our services as communi-cators are actively sought out by departmentswho need the extra manpower but can't hirethe numbers of skilled people required. Suchagencies as the Canadian Coast Guard and En-vironment Canada have shown interest in re-cruiting amateurs as assistants to their objec-tives. We appear to be at the threshold of anew world full of opportunities to serve.

On the subject of public service, there isan organisation in the United States called"H.A.P.P.Y. Flyers", which consists of peoplewho are both amateur radio operators andpilots of small aircraft. Their objects, in co-operation with the Civil Air Patrol, are to usetheir technical expertise, coupled with theirown personal aircraft, to search for and locatedowned aircraft. Not only do they do a ser-vice to the general public, but their membershave developed several high-technologygadgets to aid in the detection and trackingdown of radio signals emanating from downedaircraft. As the flyers amongst you will know,an ELT (emergency locator transmitter) is

nothing but a battery -operated transmitterthat emits a wailing tone when activated bythe impact of an aircraft crash. There is noposition information transmitted, nor doesthe transmitter give any directivity infor-mation such as a VOR (VHF Omni Range)transmitter gives to guide aircraft on our air-ways. Location of the transmitter signallingdistress is solely by radio direction -findingtechniques used by VHF amateurs in the bigcities to locate repeater -jammers. TheH.A.P.P.Y. Flyers have developed units whichthey will sell in kit form to anybody whowishes to do direction -finding for either avia-tion emergency or any other use. The name"H.A.P.P.Y. Flyers", by the way, stands for"Hams And Pilots, Piloting, Yakking." Howoriginal!

Since they already have it in the U.S.,why don't we have it here? We don't have acivilian air search and rescue organisation here

RS, agrees with a letter from Vancouveras they do in the U.S., but we don't need it -when an aircraft is lost and ELT is heard, theauthorities would be happy to hear from any-body as to its whereabouts. This could beanother way to demonstrate amateur radio'ssuperior technology to the public, and havinga lot of fun in the meantime. With the Cana-dian Coast Guard forming an auxiliary whichwill use amateur communications, it seems anatural little 'extra' to use our direction -finding capabilities to full advantage in thisarea too. (I would be happy to receive lettersfrom anybody interested in forming an or-ganisation for Canada's HAPPY flyers - justwrite to me at the ETI office).

Out WestThe premier of British Columbia, talking onthe Quebec independence issue, once said thatB.C. is the only province in Canada that hasall the resources, industry, and manpower to'go it alone' should Confederation fall apart.His words were still ringing in my ears when Ireceived a very interesting letter from an ama-teur in Vancouver. For several years, newCanadian amateurs have had a hard timeextracting the information they need fromthe various technical manuals available tothem. The old standard handbook written byMorton Biback in the early sixties was sadlyout-of-date, and no matter how many timesit was reprinted, updated, and re -written, itnever seemed to keep up with the presentstate of technology. CAR F, with their manualfor students, made a valiant attempt, butthere was still something missing. With allthis as a background, I was delighted toreceive a copy of a new study guide nowbeing sold i,i B.C. The content is easy -to -read,well detailed, and the pace of the lessons aresteady and consistent. Drawing are well-doneand clear, interspersed generously with thewritten material.

In his letter Ralph Zbarsky, VE7BTGwrites,

.. we agreed with your statement (Sept.79 QRM) that something was definitelywrong in the training techniques being used.As a result of this initial meeting, the B.C.Amateur Radio Instructors Group wasformed. The group now comprises 31 instruc-tors on a province -wide basis and provides aforum for exchanging instruction techniques,sample lessons, and new ideas relating to bothgroup and individual instruction.

"In addition to meetings, at which wehave discussed examination content and for-mat with D.O.C. officials, regular on -the -airsessions have been held to discuss problemsand solutions which are monitored by hund-reds of hams and S.W.L.s across Canada (jud-ging by the resultant check -ins and letters).The latest examinations have been discussedquestion by question to assist those instruc-tors who cannot personally attend themeetings.

"As a result of this activity, we believethat a more unified approach to instruction inB.C. has resulted. For the first time, instruc-tors (and students) have a group to which

and reports on a court case.they can turn to for assistance, a group thatexists expressly for that purpose, that is notaffiliated with either of the two major warringCanadian factions (neither of which appearready or able to serve this function). Throughthe support of individuals and clubs, we areable to maintain a post office box mailingadcress and provide services ranging from acomprehensive list of typical questions thatstudents must be capable of understanding tocertificates for successful course completion.As a representative group, we also believe thatour representations will have a greater impacton the D.O.C. than will individual approaches(which, of course, we also encourage and sup-port). Anyone wishing further informationcan contact me or the B.C.A.R.I. at PO Box35404, Vancouver, B.C. V6M 4G5."

All I can say to that is well done, Ralph!,why can't we do something like that in therest of Canada?

Amateurs In The CourtsIn a Toronto court room, this spring, MurrayCrimless, VE3GAD, of Lindsay, Ontario, ap-peared before the Judge charged with posses-sion of a device capable of detecting radarspeed measuring equipment, transmissionscontrary to the provincial highway traffic act.Armed with jurisprudence stating radio toa purely Federal matter, and two radio inspec-tors for expert testimony, Murray was all setto plead NOT GUILTY with determination towin the case, even if it meant spending morethan the thousands of dollars that he alreadyhad tied up in the case.

You will all be glad to hear that Murraygot off, but the outcome was more the workof a policeman not showing up than the legalarguments of Murray's lawyer, Lorne Jackson,VE3CXT. The judge dismissed the case forlack of evidence, and ordered the radar de-tector, (which had been seized at the time ofthe alleged offence) returned to Murray. Thispresented a problem, however, when thepolice refused to allow Murray to transportthe device home in his car, since the transpor-tation of these devices except in a factory -sealed carton is also illegal in a motor vehicle.All was resolved when somebody phoned'downtown' and got special permission. The'radar detector', incidentally, was a unit thatMurray had built from a kit in true amateurspirit many years ago, and was being used, inco-ijuction with a microwave transmitter inthe car, in some collision -avoidance experi-ments that he was legitimately performingunder his amateur license from the Feds. It'senough to make you fed up, isn't it?

QRM letters are welcome from any readerwho has an opinion to render, whetherlicensed amateur or not.Write to: -QRM LettersETI Canada,Unit 6,25 Overlea BoulevardToronto, Ontario M4H 161.

73 de Bill VE3APZ

ANALOGUEAUDIOFREQUENCYMETERGet in tune with the modern age. . . economical testgear made to measure.

THIS LINEAR SCALE AFM will enable you to resolvefrequencies from 10Hz to 100kHz in four decaderanges. .It is low in cost yet high in performance.Accuracy is unaffected by the wayeshape of the inputsignal and the unit is sensitive to input levels down toabout 200 mV. The input circuit features a protectiondiode network and the maximum safe input voltage iseffectively limited by the rating of the coupling capacitorCl. The unit operates from a single 9 volt battery and

current drain is low giving a useful life from a 9V batteryor equivalent source.

Cheap ChipsOnly two relatively cheap chips are used; a 3140bi-MOS op -amp which performs signal pre -amplificationand conditioning, driving an ordinary 555 timer confi-gured in the monostable mode. Timing components areselected by a five position range control which also

RANGE OUTPUTx i00

Snza ,X1016

Calibrating the Audio Analogue Frequency Meter against the workshop signal generator. For those without any test equipment an alternative methodis outlined in the text.50 ETI-JULY 1980

functions as the power switch. Only a handful of othercomponents are required and accuracy, after calibration,is determined by four fixed resistors.

ConstructionConstruction may take many forms. However, use of aPCB aids assembly and reduces any chance of error. Ourdesign is highly recommended. In any event, all leadsshould be kept as short as possible to void straycoupling; keeping signal input leads away from the 555for example.

Construction should proceed in the usual order. Insertthe IC holders first, followed by the passive components;resistors and capacitors, paying close attention to the

C1HI 470n

INPUT

LOW0

HOW ITThe input signal is applied to C1. RI, DI and 2provide protection against high input levels. ICI isa high input impedance op -amp configured as aSchmitt trigger with R5, 6 setting the hysterisis.C2, R2, 3 provide a mid -voltage bias source.

The output of ICI consists of a train of squarewaves at the same frequency as the input signal.This triggers the 555 timer which produces amonostable pulse of period determined by selec-tion of range resistor, R9 through R12 at the outputpin 3 from each negative excursion. The triggerpulse must be shorter than the output pulse anddifferentiating network C3, R7, 8 is used toaccomplish this.

To avoid inaccuracies owing to falling batteryvoltage, the output of 1C2 is clamped at 5 V6 byZD1 and the meter is driven via current limitingnetwork RV1, R14. A 5 V6 zener is chosen as it has

orientation of the polarised components. Finally insertthe diodes and plug the IC's into their sockets. Pin oneis indicated by an indent at the top of the package ora dot by the pin itself. Note that the signal 'low' input isseparate from the OV line.

Calibration and UseCalibration of the instrument is very straightforwardowing to the high nput impedance. With the unitswitched to the 100Hz range, touch the input with yourfinger. There will generally be enough stray power fieldto provide an adequate signal. This should cause adeflection on the meter and RV1 can be adjusted until areading of 60 Hz is obtained.

WORKSa low temperature coefficient. This means that itsvoltage exhibits little change per degree change intemperature. The reason for this is that thenegative and positive temperature coefficients ofthe zener and avalanche effects almost cancel outin `zeneediodes of this voltage.

The only possible source of trouble worth men-tion may be failure of the 555 to trigger at all. Thiscould be caused by the value of C3 being too small.Trouble from this source is unlikely. However, C3should be as small in value as possible consistentwith reliable triggering.

Current pulses from 1C2 are averaged in themeter whose deflection indicates the inputfrequency. To allow for variations in componenttolerances, full scale deflection corresponds toabout a 75% duty cycle. C5 is a supply decouplingcomponent.

R210k

RI R410k

DI D23

C210u

R510k

IC1

R733k

C3

"Pll

R10100k

R6IMO R8

R3 22k10k

NOTES.IC 1 IS 3140IC2 IS 555D1,D2 ARE 1N4148

0

.?

a

R1110k

SW1a

R121k0

C46,,8

6 IC23

GANGED

R133908

ZD15V6

RV122k R14

33k

SW1bO

°OFF

100KHZ

/ 100HZH

M1100uA

C5470u

-r9V

Fig. 1. Circuit diagram of the Analogue Frequency Meter.

ETI-JULY 1980 51

PROJECT

Of course if a signal generator of known accuracy isavailable, you can set up the unit on any desired range.However, the technique described above will enableuseful results to be obtained. A feature of the instrumentis that only one range need be calibrated; the othersfalling into line automatically.

In use, select the highest range (100 kHz), thisautomatically applies power to the unit, then connect theunknown input signal. The reading can be noted and alower range selected if required. This is to avoid spuriousreadings which can be obtained on the lower rangesowing to retriggering of the 555 by high frequency inputsignals. There are no other adjustments to make so allyou need now is something whose frequency you canmeasure.

Inside view of our prototype.

Fig. 3. The componentoverlay on the PCB.

TO METER(-ye)

PARTS LISTRESISTORS (all 1/4W, 5%)

R1,2,3,5,11 10kR4,6,9 1MR7, 14 33kR8 22kR10 100kR12 1kR13 390R

POTENTIOMETERRV1 22k preset

CAPACITORSC1 470n polyesterC2 10µ tantalumC3 56p polystyreneC4 6n8 polyesterC5 470p. electrolytic

SEMICONDUCTORSIC1 3140IC2 555D1,2 1N4148ZD1 5 V6

MISCELLANEOUSMeter 100 NA FSDSW1 2 pole 5 wayPCB case to suit

Fig. 2. PCB foil pattern for the AFM

1::1100 ww6E /404, \c

Nci.14 QOA 114SCOViR1 OF CLIORK-11.Y

WM. Ica,%11%tor4

\A 'Nit WIRK tV

52 ETI-JULY 1980

Fig.1. A view ofNORSAT's dishantenna.

Steve Rimmer reviews a Canadian Satellite System.

Elementary, My Dear HolmesI WOKE UP this morning to the soundof the Fugs being played through myguitar amp with the reverb turned upand the tremolo going full blast. It wasnot pleasant. You probably don't knowwhat exactly a Fug is, even in the singu-lar and cannot thus imagine what sort ofmanifest horror is racked upon thehuman brain by finding a bunch, threein fact, crawling around the inner ear,trolling for consciousness, at seven AM.Suffice it to say that if you met one inthe subway, he would be attonal,obscene, about fifteen years out of dateand, I suspect, probably out of work.Mid sixties East cost protest drug rock?Yes indeed. The song I arose to wascalled CCD. You may, if you wish, pon-der the meaning of those initials, orresearch them, if you're really intonostalgia, in the delete bin.

"I thought I hid that album," I recallthinking to myself. I discovered the dogsleeping in my drawer again.

I may have mentioned my acquain-tance, Max. He comes over, now andthen, to groove. I hadn't heard thatword used since I hid the Fugs album.Grooving is the process of eating food(mine), occupying space (mine), ex-periencing technology (mine) and tryingout possibly illegal substances on thedog (his and mind: his stone, my dog ..which probably explains why it wassleeping among my socks). When I gotdown to the studio, Max was sitting in abean bag chair, which he must havebrought with him, stroking a kitten.Every piece of equipment in the roomwas on. The stereo was playing throughthe synthesizer (which was, in fact pro-ducing the tremolo sound) into theamp, all the video monitors were on,displaying different tapes, and there wasa Devil's Dungeon game in progress onthe computer. Max smiled. He proferredme the cat. "I brought ya this."

I was speechless with gratitude. Orsomething.

"You gonna buy a satellite soon?"Max inquired.

"Will you take the cat back if I sayno?"

"Course not.""What about if I say yes?" It's all a

foolish discourse. You can't buy sate-llite systems in second hand shops orflea markets, the haunts of the finan-cially inopportune.

"I had an idea how you could shootone down, if ya want." Max said ser-iously. You can't really tell if he's grin-ning through his beard.

"Listen, hit me next week. I gotta dothe column." Max understood this. Healways reads the column. Fortunately,I get two copies of the magazine, so I

usually get a chance to see it too."Elementary, my dear Holmes" he

said, and left.It only struck me much later that

this had been a pun, and a rather vileone. I turned everything off and startedtrying to figure out which of several vis-cously bubbling topics to throw the eyeof a newt into and transform into acouple of thousand words.

What eventually decided me was thelast stack of mail I got (see; you dohave a say in things). The most frequentquestion I've encountered to date dealtwith satellites: notably, where to pur-chase downlink hardware from. It seemslike it's about time for another satellitebit, and this would be a useful area tocover in some depth. This month, we'regoing to look at NORSAT SYSTEMS.If you've been considering buying asatellite system, this may be just whatyou need.

And I can send Max over to yourplace next time.

NorsatReaders who spend their n ghts tun-

nelling through ETI's back pages mayhave noticed an ad for NORSATSYSTEMS (P.O. Box 232, Surrey B.C.V3T 4W8). As far as I can tell, to date,these folks are the only Canadian basedsupplier of home satellite groundstation equipment. To be sure, con-sidering the duty and shipping chargesinvolved in importing equipment fromthe States, this is the cheapest way togo. Furthermore, as the equipment sup-plied by NORSAT is of a Canadiandesign, it appears to be better able towithstand our novel climatic variations.The dish antenna, (Fig.1) for example,is claimed to be able to emerge un-scathed from 100 mile an hour breezes.Those are real miles. Smaller dishes areavailable if you wish to convert tometric.

NORSAT has available both plansand complete kits.

The dish antennas are sold in threebits, these being the reflector proper,the feed (which sits on the dish) and themount, which takes up the space be-tween the dish and the ground. The dishis supplied in pieces . . . fourteen bigones, the segments, or "ribs" of thereflectors, and a somewhat largernumber of smaller ones, which will getlost, unless you're careful. Small piecesusually do. When it's all put together,it is twelve feet (or 3.7 meters, if youwant to be difficult) in diameter. Theactual reflector surface is aluminum,supported by a fairly simple plywoodstructure. The plywood doesn't comewith the kit, as the cost of shipping itwould exceed the actual worth of thematerial.

The plans alone go for about a hun-dred dollars, and the kit of pre-cutpieces 'or about a thousand. This is abit like a twenty thousand dollar Rolls;a great price, but it's still a lot of bread.If you elect to buy just the plans, NOR -SAT estimates that you can buy the

ETI-JULY 1980 53

materials (and do the cutting yourself)for about three hundred.

Judging by some photographs thatNORSAT enclosed. (Fig. 2) dealing withthe bringing to life of one of thesemarvelous metal frisbees, any mad foolwith a hammer and a three car garagecould get the dish together. But docheck out that garage. It's not just anydoor that will pass a twelve foot dish ..and no matter how you turn the thing,it's still twelve feet across. If you reallyget stuck, you can make it 3.7 meters.

The feed system for the dish is avail-able only in an assembled form, mostlybecause it could not be built to thenecessary tolerances as a kit. It is, infact, not even built by NORSAT, al-though it uses NORSAT's design, butrather, by a firm which specializes inthese things. All this precision goes fora mere $168.00.

The final component of the antennaproper is the mounting structure. This isa bit of a grey area for a number of rea-sons. The exact nature of what oneuses as a mount will be determined bya number of factors, such as, what kindof meteorology is likely to impose it-self up the dish, whether or not theantenna is to be steerable, and so forth.Furthermore, the mount is physicallyhuge, and made of relatively inexpensivematerials. As such, NORSAT does notsell a kit of parts, but only plans for thiscomponent, for twenty- eight dollars.

The specifications of the dish willprobably be qite meaningless to anyonewho does not chance to be a microwaveengineer, but, then, probably no moreso than the specs of a stereo. If nothingelse, they are good for party banter andcomparison. The minimum gain at3.7 GHz is 40.8, rising to 41.9 at 4.2GHz. The noise temperature at 40° isless than 25° K. Judging by what I'vebeen told (relatively little), I think thisis pretty good.

The ouput of the feed is type CPR229G. If you've taken apart a DEW linestation recently, you probably have oneof these in a drawer somewhere.

The important part of a satellite sys-tem is actually the receiver, to some de-gree. The antenna has to be properly de-signed, stable and of sufficient gain tobe sure, and, from a theoretical point ofview, the receiver could be quite klugy.With respect to some of the articles thathave been running in a few of the U.S.technical magazines of late, one could,it seems, get together a simple receiver(sort of) that would get useable pic-tures. However, producing a system thatone could actually watch without goingmad retuning and adjusting, and onethat can make full use of a goodantenna by being able to check outeverything that's "up there", requires

somewhat more expertise. To a greaterdegree than the dish antenna, which isacually just a relatively simple bit ofmechanical work, receivers for personalsystems are a somewhat new frontier.Until a few years ago, no one was tryingto design low cost instruments to dothis job, because the only people whoneeded groundlink sets were quite pre-pared to pay top dollar for them. Thusit is that, while several fairly goodantennas are available, the choice of re-ceivers is considerably more limited.NORSAT's CTC-2001 (Fig. 3) is, appa-rently, among the more highly regardeddesigns in this area. The price . . . a

mind searing, wallet shattering $29.45. . . no no, pardon me, that's $2945.00. . . is actually a few hundred dollarsbelow the landed cost of the Americancompetition. Once again, the splendorof the savings is overshadowed by thesheer magnitude of that which remainsto be spent.

The receiver is housed in a 19" (notavailable in metric rack mounted case,which looks to be about 5'/4" high. Itis capable of being tuned to any of theup to twenty-four satellite downlink fre-quencies. The front panel contains avery complete system to monitor whatthe internal wizzbangs are up to, con-sisting of a switchable meter to dealwith signal levels or tuning lock, plusfourteen status LEDs. There is also aheadphone jack to monitor receivedsound before it heads out to the stereofor amplification. The system also con-tains a regulated power supply to sendout to the dish and fire up the feedmounted low noise amplifier.

The aforementioned internal wizz-bangs of the set live on modular, plug incards, to facilitate servicing.

For some of us, twenty-five hun-dred dollars would certainly mean nobeer this weekend, and, possibly, sellingthe front lawn to a sod farm. However,there are those who have large limits ontheir Visa cards, and will want to guildthe silicon lilly. For these depraved,and obviously grossly overpayed oilcompany executives, there are optionsavailable for the receiver.

Option number one is the installationof an improved discriminator. See whyall the circuitry is modular? This im-provement will reduce the noise, or"sparklies" seen in a picture when theantenna and low noise amp are justabout out at their limit. In fact, it willbe of some benefit even in a larger sys-tem, as it reduces the noise generatedby the receiver itself, thus "quieting"down the picture a bit. At seventy- twodollars, it's well worth it.

If you are a bit confused as to whata discriminator has to do with videoquality, remember that satellite down-

Fig.2. NORSAT antenna under constr-uction.

links have the picture component modu-lated FM, to get a useable signal-to-noise ratio over the extremely high losstransmission path.

The second option is a VHF modula-tor, which bounces both the demodula-ted video and audio down to a standardbroadcast TV channel, so you can seeuncut Carson shows on your very own1958 round screen Zenith, instead ofpopping for a proper monitor.

As with all modulators used in thisway, there is some degradation ofpicture quality when a broadcast TV isused, as opposed to a direct feed moni-tor.

The audio on the WESTAR satellitesis somewhat different from that onSATCOM, and the other "birds", and assuch, cannot be demodulated by the de-modulator that comes with the receiver.This is very sad, especially if there hap-pens to be something on WESTAR youwant to hear as well as watch. To cheeryou up, I should tell you that behindoption number three there is a brandnew second audio subcarrier demodula-tor. It plug into the receiver along withthe existing circuit, and can be switchedin from the front panel when needed.Isn't that amazing? It costs $104.00.Still amazing, but not quite as much.

Option four is a walnut cabinet, at$98.00. This may be the point to digout the saw and take apart the bookshelves.

Option five is a gas. It's a key lockpower switch. For why? "It is parti-cularly useful to censor childrensviewing of pay TV R and X ratedmovies." Now, I can understand thethinking behind this, and it's probably agood thought. It will either keep thekids away from the tube when there areblue flicks about . . . or teach them auseful trade ... like locksmithing.

The final option makes use of thedesign of the receiver's front end, whichemploys a voltage controlled oscillator,as opposed to just a direct drive tuningcapacitor. Because the tuning is accom-plished via a DC voltage, a remotetuning control can be plugged into

54 ETI-JULY 1980

the back of the set. Stations can there-upon be selected from ohes chairside.If you could arrange to be fed intraven-ously, you'd never have to get up again.At $137.00, this is most expensive ofthe options, and, I feel, is the leastuseful. If you are too stoned to get upand change the channel, you are toostoned to care what is on the screen.

As before, I'm not sure that thespecifications for the receiver willbe of much practical use, as few of usare really capable of fully understandingthem in light of the application towhich the system will be put. On top ofthis, there are few other sets to compareit to. However, recognizing that withoutnumbers, pocket calculators wouldnever have been invented (and thenwhere would we be?), I'll lay a few ofthe more interesting digits upon you. Inall cases, the receiver conforms to thevarious standards for frequencies andsubcarriers used by the satellites,including the WESTAR sound channel,with the appropriate option.

The RF Noise figure is 13 dB maxi-mum. The FM threshold is 9.5 dB withthe standard discriminator, and 8.5 withoption one. The video bandwidth ex-tends to 6 MHz with a 52 dB signal tonoise ratio. For comparison, a homeVCR at normal speed has 43 dB signalto noise. The audio bandwidth is 45 Hzto 15 KHz, at up to plus 10 dBm into600 ohms. The headphone jack acceptsnormal 8 ohm cans.

In addition to all this hardware,NORSAT also supplies a "Site Co-or-dination/Performance Study", to keepyou from locating your antenna at thebottom of a well, or other equally un-suitable place. The cost of this serviceis $25.00.

The LawAn lastly, the law. I was talking withCharlie Pitts, of Spacecoast research, aFlorida based distributor of TV ROdownlink hardware, several weeks ago.Spacecoast feels that it could offer moreof its products to we poor frostbittengnomes North of the invisible line, butfor the duty and postage. To this end,the company is seriously considering aCanadian manufacturing facility. Charliewas up here on a "fact finding" safari,investigating, among other things, thepossible existence of any legal hasslesdealing with private satellite systemowners. I think he garnered more ques-tions than answers. The only really offi-cial word on broadcasting in Canada isthe Department of Communications,who were fuzzy at best. They haveonly one related document, which,upon labourious unpacking (andspreading out all over the floor), re-vealed to us both that it misses the

mark altogether. Subsequent forays intothis never-never land of paper marsh gasmonsters have given me no further in-sights into the question.

To date, the powers that be seem tobe ignoring the private owners ofsatellite equipment. This may be, inpart, because there are very few ofthem. Then, too, they are not actuallyhurting any of the program owners, asnone of the American services, HBO,STAR CHANNEL, and so fort, couldbe had and paid for in the usual way inCanada. Then, too, there are indivi-duals like David Brough who use satel-lite transmissions to provide ersatznetwork programming to remote areasof the country where the CBC fears totread . . . even though it has a mandateto do so.

The fact is, though, that things arevery loose in the legal aspects of satel-lites. I recall an international statutethat states that anybody can receive anymaterial trarsmitted over the (public)airwaves, provided he does not com-municate what he has received to anythird party. This seems to relate more orless to short wave transmissions, but,technically, it also seems to cover satel-lite downlinks. Presumably, then, onecould use the material provided onedidn't set up a cable system with it,sell tapes of it, or, to be sticky, dis-cuss what was on the tube last night onthe way into work.

I think that this is becoming an in-creasingly important question, as moreand more Canadians start sinking thefamily jewels into downlinks. While it isprobably beyond all humans and mostlesser dieties to get the laws changed, it

coversthen,Stay Tuned.

would be nice to know where we allstand,especially if some fellow in a redsuit with bowed legs appears at the doorbearing a tool box and an evil grin.

I hope that someone out there, pos-sibly in some branch of the legal profes-sion, or a neighbour thereof, knowssomething concrete about this impor-tant question. Or, perhaps you have anopinion, or some blinding insight intofurther ramifications of the problem.If you checked yes beside any of theabove, feel free to grasp any one of yoursixty-four Crayola crayons firmly in thetermination of any suitable extremityand write in. If it's in English, or rela-tively legible sanskrit, we'll print it.Maybe.Switching OffThat moment has come again, when wemust all grasp our volume controls be-tween our fingers and turn ourselvesoff, shrinking rapidly down into a

single, rapidly fading white dot, andvanish, ultimately, from the screen. Oneday we shall no doubt weary of this,and shrug off this slug tuned, high Qcoil, putting our collective foot throughour respective screens . . if we do it inunison, who knows ... the shock mightkill Mork and Mindy once and for all.Listen, the risk is great, but considerthe prize if we succeed!

Next month's column will containmany words, some beginning with capi-tal letters, and will undoubtedly dealwith something related, howeverdistantly, to video ... unless, of course,it does not. I think that pretty well

most of the possibilities. Until

What's On? Table IIf you are still trying to talk yourself into filling in the pool and putting upan antenna, you may be interested in the current "TV Guide" for RCA'sSATCOM Fl "bird", at present, the most interesting resident of the outerreaches.

ChannelNumber

ProgramSource

1 K TV U Inc ependent Slat an °room., in San Pranosco. 12 SHOWTIME (East Cost Version).2 P91 ReltBous programming, 13 TRINITY Religtons prograrommq.3 VVGN Independent Station origmattng in Chicago 14 RCA Owned used for venous PutFiene,

45

A V ict tin of Murphy's Law (Broken & Not in Serwee).Warner Brothers -Star ChannerUntnterruptec Movies,

1516

Not yet occupied.F ANFARE Another Sports Channel

6 WTBS Independent ("S.W.) Station oreamettng In Atlanta.ESPN All Sports Network (Incessant Howard Cossellrokst.

1118

INCIFi.SIN Spanish International Network.

89

CBN Rehm°. programmtng.Al,,,,?,t. between Madison Square Gardens transmostons and a

1920

ocontiethHOME BOX OFFICE AI present. a spare channel

new service called CSPAN. 21 SOUTHERN SATELI iTE SYSTEMS -Pay TV.10 SHOVVTIME,A Pay TV Network (West Coast Version/ 22 HOME BOX OFF CE Urenterrupted TOW, (West Coast Version).11 NICKELODEON A -second bower" of Warner Brothers STAR 23 HOME BOX OFFICE 141re 2 171610 Second servIce/.

CHANNEL 24 HOME BOX OF FICF IF Fool Coast Version)

ETI-JULY 1980 55

FEATURE

EACHER STOPICS

Have you ever wondered why the word 'Decibels' seems to crop up everywhere in the electronics field?Ian Sinclair explains both the origins and the usage.LOOK UP THE REFERENCE BOOKS, and they'll tell youthat Alexander Graham Bell invented the telephone. Hedid, true enough, but what he was trying to invent was adeaf -aid, and it just happened that the microphone andearpiece he came up with were a lot more suitable for atelephone than for the deaf. The point is that Bell wasvery interested in ears and hearing, which is how a unitcalled the bel came about. One tenth of a bel is called adecibel, and it's this unit whose name seems to crop upeverywhere in electronics.

Why? Well, it happens that the end result of a lot ofelectronic gadgets is something you hear or see, andBell's work on the telephone led to a very importantdiscovery about the way we hear sounds. A telephonemicrophone converts sound waves into electricalsignals. Now electrical signals are waves that we canmeasure, and even a hundred years ago we couldmeasure the power of electrical signals, so that conver-ting sound waves into electrical signals is a very con-venient way of measuring the power of sound waves.Bell carried out some measurements, and made therather surprising discovery that two sounds of the samepitch, one with twice as much power as the other, did notsound so very different to the ear. Quite certainly, onedidn't sound twice as loud as the other.Ring of ConfidenceIt's not so surprising when we use modern equipment tomake measurements on the sounds around us. Thesoftest sound we can just hear (those of us of thegeneration before discos, that is); has a power of aboutone millionth of a millionth (10-12) of a watt on eachsquare metre of surface. The loudest sound our ears canstand (Concorde at three yards, or a disco at 20 feet)sends out something like 10 watts per square metre.Now there's a huge ratio between these two quantities,some ten million millions, a darn sight more than theratio of sizes of an elephant to a flea, and no instrumentcan be devised which can handle the full range. Howdoes the ear cope, then? The answer is that the output ofsignals which the ear sends to the brain isn'tproportional to the power of the signals arriving at theear, but to the logarithm of the sound power.

Remember your logs? The logarithm of ten is 1, thelogarithm of 100 is 2, and the log of 1 000 is just 3. Forthese numbers which are powers of ten (ten multipliedby itself several times), the log is equal to the number ofzeros which follow the 1.

The other feature of logs which made them so usefulin the days before pocket calculators (that's given myage away!) is that multiplying and dividing numbers canbe done simply by adding or subtracting the logs of thenumbers. For example, the ratio 1 000 /10= 100 canbe worked out by taking the logarithms 3 (log of 1 000)and 1 (log of 10), and subtracting, to give 2 (log of 100.

You wouldn't use logs for such a simple one as that, butit did make more complicated multiplications and divi-sions a lot easier.Logs and WattsTo measure how the ear reacts to sound, then, we takethe log of a ratio of powers. We need two measurementsof powers to form a ratio, though, so that we have tochoose some standard to compare all other powermeasurement to. In electronics we take 1 mW (onemilliwatt, which is one thousandth of a watt) as thestandard power, though acoustical engineers sometimesuse the threshold of hearing, 10-12 W / square metre astheir starting point. When someone says that a sound is95 decibels, then, you need to know from which powerlevel this is being measured.

When we measure some quantity of power, we findthe ratio of that power to one milliwatt, then find thelogarithm of the ratio, and the result is the number ofbels. A lot of measurements in electronics are powerratios to start with, such as the ratio of power out of anamplifier to the power in (power gain) and we canchange these ratios into bels by taking the log. Forexample, a power ratio of 50 000 works out at 4.699bels.

The bel is rather a large unit, so for convenience weuse its smaller brother, the decibel. A decibel is onetenth of a bel (is a decimal a tenth of a mal, and whatdoes that make a decision?), so that 4.699 bels are46.99, 50 as near as maybe, decibels. As it happens,the ratio of power corresponding to one decibel is justabout the smallest difference the ear can detect. As aformula, then, the decibel ratio is:

db = 10 log (power ratio)

Now, strictly speaking, decibels should be used justfor this job of power ratio measurement, and nothingelse, but the idea is so useful that decibel ratios are usedeven when what we are measuring is not a power ratio.One very common use (or misuse) is to compare signalvoltages rather than powers, and when this is done, theformula is changed to:

db = 20 log (voltage ratio)

Why 20? Well, the reason is that when we have avoltage V across a resistance R, the power is given byV2/ R, voltage squared divided by resistance. Squaringany quantity can be carried out by multiplying the log ofthe quantity by two, so that the voltage ratio is convertedinto 'decibels' and then multiplied by two, giving the 20in the formula. Strictly speaking, this use of decibels isjustified only when the voltages are measured across thesame value of resistance, such as when we compare theoutput of an amplifier at two different frequencies.

56 ETI-JULY 1980

DECIBELS TO VOLTAGE GAINTo use the table, split up the decibel figures into tens andunits (100 is ten tens) look up the tens figure in theleft-hand column, and the units figure in the top row.The intersection gives the voltage ratio which corres-ponds to the db figure. For example, 26 decibels is 1 9 9times.

Units 1 2 3 4 5 6 7 8 9 10Tens0 1.12 1.26 1.41 1.48 1.78 1.99 2.24 2.51 2.81 3.161 3.55 3.98 4.47 5.01 5.62 6.31 7.08 7.94 8.91 10.02 Numbers in this row are 10 times the numbers in the first row3 Numbers in this row are 10 times the numbers in the second row4 Numbers in this row are 100 times the numbers in the first row5 Numbers in this row are 100 times the numbers in the second row6 Numbers in this row are 1,000 times the numbers in the first row7 Numbers in this row are 1,000 times the numbers in the second

row8 Numbers in this row are 10,000 times the numbers in the first row9 Numbers in this row are 10,000 times the numbers in the second

row10 Numbers in this row are 100,000 times the numbers in the first

row

Voltage is so much easier to measure directly, using anoscilloscope, than power that we're stuck with 'voltage'decibels for good now.

Pocket DecibelsIf you carry a pocket calculator which has a log key, thenworking out decibels is easy - you work out the ratio ofpowers or voltages, press the log key, then multiply byten for power ratios and twenty for voltage ratios. A fewcalculators even have a db key, so that a ratio of voltagescan be converted directly. If you haven't a calculator, or ithasn't a log key, try the tables shown in Fig. 1, whichgive voltage/decibel conversions as quickly and accu-rately as you're likely to need. Remember that a decibelout either way is hardly noticeable

VOLTAGE GAIN TO DECIBELSTo use the table, convert the gain to a number (less thanten) and power of ten. For example, a gain of 52,000 is5.2 x 10,000, and a gain of 652 is 6.52 x 100. Look upeach part of this number in the table, and add. Forexample, 5.2 is, from the table, 14.3, and 10,000 is80db. Adding these gives 94.3 db. One place ofdecimals of voltage gain is enough, because the dif-ference in decibels is very small.

Gain 0 .1 .2 .3 .4 .5 .6 .7 .8 .91 0 .82 1.48 2.28 2.92 3.52 4.08 4.60 5.125.56db2 6.02 6.44 6.84 7.22 7.60 7.96 8.30 8.42 8.949.24db3 9.54 9.82 10.1 10.4 10.6 10.9 11.1 11.4 11.611.8db4 12.0 12.2 12.5 12.7 12.9 13.1 13.2 13.4 13.613.8db5 13.9 14.0 14.3 14.5 14.6 14.8 14.9 15.1 15.315.4db6 15.6 15.7 15.8 15.9 16.1 16.3 16.4 16.5 16.616.8db7 16.9 17.0 17.1 17.3 17.4 17.5 17.6 17.7 17.817.9db8 18.1 18.2 18.3 18.4 18.5 18.6 18.7 18.8 18.919.0db9 19.1 19.2 19.3 19.4 19.5 19.5 19.6 19.7 19.819.9db

Powers of ten:10 20 db 10,000 BO db100 40 db 100,000 100 db1,000 60 db 1000,000 120 db

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ETI-JULY 1980 57

PROJECT

METRONOME

For any up and coming musiciana sense of timing is of great importance(something not easily acquired by most of us). The ETIMetronome will at least keep you in strict tempo and save thephysical efforts of tapping your feet to keep in time.THE TEMPO RANGE of theinstrument is variable over the 10:1range of approximately 300 to 30beats per minute via RV1, and thusfully spans the musical tempo rangeof Largo (40 beats per minute) toPresto (208 beats per minute). Thetempo range can be adjusted, ifrequired, by changing the value ofC1. Increasing the C1 value lowersthe whole range, and decreasing C1raises the range.

Music To Your EarsRV1 can be calibrated in terms ofconventional musical tempo namesby using a watch with a second handto compare the number ofmetronome beats per minute againstthe information in the followingtable:

TempoName

Tempo SpanBeats/ Min

Mid rangeTempoBeats /Min

Largo 40-60 50Larghetto 60-66 63Adagio 66-76 71Andante 76-108 92Moderato 108-120 114Allegro 120-168 144Presto 168-208 188

The instrument can be used aseither a normal metronome, or as anaccentuated beat metronome. Ourdesign allows for four basic rhythmicpatterns in the time signatures of2-4, 3-4, 4-4, and 6-8.

The tone of the non -accentuatedbeats is variable via RV4, that of theaccentuated beat via RV3, and thebeat length via RV2.

ACCENT

ACCENT ACCENT> >J J J

ACCENT

ACCENT

Fig. 1. The accented beat of the bar.

ConstructionConstruction of the metronomeshould not pose any special problemsproviding the overlay is followedcarefully and correct orientation of allelectrolytic capacitors and diodes isobserved.

The type of switch used is a matterof personal choice; either a bank ofinterlocking push button switches, asused on our prototype, or a rotaryswitch may be employed, this beingthe cheaper.

The switch assembly is mounteddirectly onto the front panel withstand off pillars to give the correctrecessed depth, all interwiring toeach switch is taken via a six -waysocket.

After checking that all is well thesetting up procedure may now becarried out.

CalibrationSetting up the metronome is quitestraightforward. Rotate RV2 (locatedon the rear panel) fullyanti -clockwise, then select the normalmode of operation. Switch on the

58 ETI-JULY 1980

POWER SUPPLY CONNECTIONS+9V TO1C2 PIN14

ICP1C4

PIN14N14

OV TOIC2 PINTIC3 PIN7IC4 PIN)

NOTE:IC1 IS 40171C263 ARE 4001IC4 IS 4011IC5 IS 556C11-7 ARE 1N4148

1113

CI., L2011

L.RV1 C21M0 1u0linTEMPO

13 6

Fig.2. Circuit diagram of the metronome.

PARTS LISTRESISTORSR1, R7R2R3, R4R5R6

POTSRV1RV2RV3, RV4

CAPACITORSC1, C3C2C4, C6C5C7, C8

10k1k100k4k722k

1 MO LinIMO preset (knob operation)100k Lin

SEMICONDUCTORSIC1IC2, IC3IC4IC5LED 1, 0.2in dia

220n polyester1 uo polyester100n polyester10n polyester220u elect

401740014011NE555D1-07, 1N 4148

MISCELLANEOUS

PB1-5 posit change overpush button,(interlocking action). Rotary switch may

4OR Loudspeaker 21/2in dia.SPST miniature toggle.

unit - the down beat LED should bepermanently on and a steady toneheard from the loudspeaker.

For the accentuated beat to fall onthe correct note of each bar, anapproximate setting for the accentand tone controls should be adjustedas follows:(set tempo according to timesignature used)

ETI-JULY 1980

6

P41 POSITIONSr NORMAL1,2-4 BEAT

d "

R4100k

RV2

linPULSELENGTH

RV4100kIlnTONE

C72200

CM

R8605 to100R

LSI8R to405

Internal view of metronome showing PCB layout and connections of the front panel.

Beat Accent2/4 Fully

clockwise3/4 Fully

anti -clockwise4/4 Fully

clockwise6/8 Midway

ToneFullyanti -clockwiseFullyclockwilseFullyanti -clockwiseFullyanti -clockwise

SW 1

9V

CS

t220o

1005TOTAL

That just about completes theconstruction and calibration for theunit.

Hopefully our metronome willserve it's purpose as you acquire -your sense of rhythm, even to themore complex arrangements that willfollow.*

59

The full size PCB layout

TiT is cik4g-T PRoms6 s ToVssrnogft(ALt1 kosocA. yooR)soiEsfic CLIctRiaN

0 V

'V.TO SVI1

RV1

Fig.3. Component overlay.

NE ACCENTUATEDrrn .1 BEAT IJJ

METRONOMEi

PORM11* 4111BE AT

PV3.RV4

HOW IT WORKSIC3a and IC3b form the Tempo generator,and are wired as a free -running astablemultivibrator with it's operating frequencyvariable over the approximate range 30 to3000 cycles per minute via RV I: the range ofthe generator can be adjusted to cover thisprecise range, if required, by adjusting thevalue of Cl.

The output of the Tempo generator is usedto clock counter IC1 via buffer gates IC3cand IC3d, and simultaneously to trigger amonostable multivibrator or pulse generatorthat is formed from IC4a and IC4b. Theoutput of this monostable is used to gate onthe circuit's tone generator, which is builtaround IC5, via inverting buffer stage IC4cand via R5 and D7.

The frequency of the IC5 tone generator iscontrolled by either RV3 or RV4, which areselected via gate diodes DI to D6 from theoutput of the IC1 counter. When the unit isused as a normal metronome the tone iscontrolled by RV3 only, and the circuitgenerates a brief 'tick' or 'tock' tone (depen-ding on the setting of RV3) each time thetempo generator completes an operatingcycle. The duration of this tone is'variable viaRV2.

IC1 is a 4017 decade counter with tendecoded outputs. Output '0' is used to control

-f-

R V3

the ACCENT of the IC5 tone generator viaDI and RV3, and also to activate beat -

indicating LED via IC4d, and outputs 'I' to '5'used to control the TONE via D2 -D6 and

RV4. Outputs 'I', '2', '3', '4', or '6', are used tocontrol the counting model of IC1 via SW1and a logic network designed around IC2.This network causes the counter to resetafter each clock cycle which the unit is usedin the normal metronome mode, or after eachalternate cycle in the 2-4 beat mode, or afterevery third cycle in the 3-4 mode, or afterevery fourth cycle in the 4-4 mode, or afterevery sixth cycle in the 6-8 mode.Readers should note that, when the instru-ment is used in the accentuated beat mode,the apparent or illusory position of theaccented note can be shifted to the start orend of a beat sequence by merely altering therelationships of the Tone and Accentfrequencies. The sound 'dee-dah-dah' (accentat the start of the beat) is clinically identicalwith `dah-dah-dee' :accent at the end of thebat) in a continuously repeating timesequence, although the change of accentposition is not necessarily noticeable to thehuman ear: when frequencies are transposed,however, the latter sound becomes 'dee-dee-dah', and the accent clearly appears to be atthe end of the beat.

60 ETI-JULY 1980

COLUMN

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MOW_ ift4kiliri=mai -rut m41' 111140/ ilf

NIV/I mtir

SHORTWAVEWORLD

John Garner, our Short Wave Editor, takes a look at some receivers.FOR MANY YEARS Radio Shackstores sold the very popular DX -150Communications Receiver, followed bythe modified versions - the DX -150A,DX -150B and the DX -160. Since thesesets were selling for under $200. theywere about the only ones affordable forbeginner listeners until about five yearsago when the Barlow -Wadley loop wasinvented and used in a number of re-ceivers at a reasonable price. Except forthe difficulty of tuning the slide -ruletype scale of the DX150 and 160, thesets operated very well. Most of us whoat one time owned a DX -150 for a whilegraduated to a receiver with bettertuning controls, such as the YaesuFRG -7. Sales of the DX -160 soon beganto declinetook it off the market. However youmay still be able to find one in someRadio Shack stores.

The DX200In April the replacement for the DX -160 appeared in the local Radio Shackstore selling for $299. Thanks to thestore owners we were able to borrow anew DX -200 for a weekend to do somecomparative listening.

The general appearance of the DX -200 is quite attractive. The cabinet issimilar to the DX -300 except instead ofthe digital readout there are two largetuning drums - one for the main tuningand one for the bandspread - reminis-cent of the Kenwood R-300.

Main features of the DX -200, as out-lined in the Radio Shack Owner's Man-ual shown in Table I.Front panel controls on the DX -200 arewell placed and these include: BFOPitch, S -Meter, Antenna Trimmer, AGCSwitch, Band Selector (0.15-0.4, 0.52-1.6, 1.6-4.5, 4.5-13, 13-30), BandSpread Tuning Dial, Main tuning Dial,Headphone jack, Calibrator switch,Mode Selector, Volume/Off control,and RF Gain Control.

On the rear panel we have an exter-nal speaker jack, the power cord,Ground Screw terminal, Antenna Screwterminal and the Mute screw terminal.

After an afternoon of listening to the

DX -200 I have the following observa-tions on its operation. Tuning thereceiver is, at best, very awkward.Tuning is accomplished by setting themain tuning dial, calibrating with the500 kHz marker, setting the main dialon a red indicator mark and then settingthe band spread. You should then beable to read the correct frequency.However in practice this is not quite so.After finding Radio Moscow on 12010kHz on the other sets we had operating- Yaesu FRG -7 and FRG -7000, Pana-sonic RF-2800 and a Radio ShackDX302 - in a matter of seconds, I

then proceeded to try this same fre-quency on the DX -200. I finally foundit after a number of minutes ofsearching and the dial read 11880. Thisis just not good enough for any seriousshortwave listener. The audio qualitywas very good. Selectivity and Sensiti-vity of the set were quite acceptable.

I believe that for a receiver selling for$300. the tuning method should bemore accurate and simplified. Since thisset would be for the newcomer to theshortwave listening hobby I think hewould deserve something better.

In conclusion I must say I cannotrecommend this receiver for any seriouslistening.

Radio Shack's DX 302In the early 1970s Radio Shack intro-duced the SX-190, a direct frequencyreadout receiver that was very popularfor a while. The set required a numberof crystals and also suffered a few pro-blems. When Yaesu introduced the dir-ect readout FRG -7 the market for theSX-190 virtually disappeared and RadioShack began to look for a replacementfor it. This resulted in the DX -300which came on the market in 1979,after very much advance publicitywhich sounded very good. We were allwaiting anxiously for the first appear-ance of the DX -300. Unfortunately thefirst sets to appear on the market suf-fered many problems and changes werehurriedly made by Radio Shack. Thosewho bought the original sets were re-turning them to stores for refunds ormodifications to make them operable.Finally by the end of 1979, RadioShack stopped producing the DX -300.

Table I, DX200

F eaturesFREQUENCY COVERAGE 150 to 000 kilohertz and520 kilohertz tc 30 Megahertz.

Large, easy to -ead frequency display dials for both maintuning and bancl spreadFast and slow AGC selector.Variable BFO Pitch for reception of CW and SSB signals.Antenna trimmer matches your antenna to the trequencyband you're listening to.Five element CeraMIC filter for outstanding selectivity/freedom from adjacent channel interference/.-Dual MOS FETs m the critical RF and mixing stages eliminate cross modulation and RF distortion.All solid state circuitry provides maximum efficient withminimum oise.Integrated elms it audio amplifier for high intelligibility500 kilohertz marker for calibration of main tuning andband spreadStandby switch and rear panel MUTE contact 'or use inHAM installationsExternal speak, jack.Band Spread dial electronically expands frequency on 10shortwave banes, 15 HAM bands and the CB band.

SpecificationsSemiconductorComplement

Receiving System Frequency coverage

Reception Mode

4 IC's, 13 transistors, 16 diodesand 6 LEDs.Single Conversion.0.15 - 0.40 MHz (150 400 kHz)0.52 - 1 6 MHz 1520 1600 kHz)1.6 - 4.5 MHz4.5 13 MHz13 30 MHzAM, SSB, CW

Antenna Impedance

Sensitivity (AM)

Image Ratio

Selectivity

I.F -

Signal to -Noise RatioAGC fat 7 MHz)

RF Gain ControlRange810 Fitch Range Fidelc y RestonseIAM)

Audio outputTHD(at 7 MHz. 1 mV)Hum & Noise

Calibrator ac.suracyPower RequnementDimer sions

Weight Price

Lo.Z for 50 ohms antenna and Hi -Zfor long wire antenna250 kHz 1 uV

1 MHz 1 uV2.5 MHz 1 uV

7 MHz 1 uV21 MHz 1 uV

250 kHz 55 dBI MH: 40 dB

2.5 MHz 40 dB7 MHz 30 dB

21 MHz 15 d8-6 dB 4 kHz

40 dB 6 kHz455 kHz45 dB at 7 MHz, 1 mV10 dB change in output for 80 dBchange in input.

80 dB at 7 MHz3 kHz.

300 FR .4 dB2 kHz 8 dB

(1 kHz= 04B 50 mWl1.5 watts, 10% T HD3 % at 30% modulation5% at 80% modulationSpeaker output at minimumvolurnn - 3 myHeadphone output at minimumvolume - 0.3 mV500 kHz 20 ppmAC 120 V, 60 Hz145 mom high 360 mm wide,220 mm deep4.1 kilograms5299.95 Canadian.

ETI-JULY 1980 61

COLUMN

In April our local Radio Shack storereceived their first DX -302, the re-placement model for the DX -300 andwe were given this set for an afternoonof tuning in the bands.

The overall appearance of theDX -302 is identical to the DX -300 witha couple of slight changes in wording ofcontrols. Performance has been im-proved considerably. Selectivity is muchbetter and the problem with the Mega-hertz tuning knob whereby a stationcould be heard one thousand kilohertzabove its proper location seems to havebeen eliminated in the shortwave range.I did notice this problem still exists onthe medium wave band, that is our threelocal AM stations on 580, 800 and 1230also appeared on 1580, 1800 and 2230kilohertz (exactly 1 MHz higher).

The BFO pitch control was able tobring in good crisp SSB and CW signals.Stability of the digital display is verygood. I only noticed a drift of 1 kilo-hertz on a very few occasions during ourlistening experiment. Audio quality is

also quite good.The Owner's Manual for this set as

well as for the DX -200 include severalpages of information for the newcomerincluding some shortwave stations' fre-quencies (although much of this infor-mation is outdated). The manual pointsout the main features of the DX -302,shown in Table 2

Table II, DX -302

FeaturesQuartz.controlled frequency synthesizer.Continuous frequency coverage from 10 kilohertz to 30Megahertz.Large digital frequency display.Triple conversion circuitry.6 element and 9 element ceramic filters provide out-standing selectivity (freedom from adiacent channel interfaience).Dual MOS F ET in the critical mixer stage (freedom fromcrossmodulation and undesired RF distort ion).All silicon solid state circuitry for maximum circuit efficiency with minimum noise.Audio power IC provides high intelligibility soundAC or DC negative ground operation. If the AC powershould fail an automatic circuit switches over to the bat-tery power with no interruption of sound.

SpecificationsSemi -conductor Complement - 1 LSI CMOS FrequencyCounter IC, 3 Integrated Circuits, 39 transistors, 32 diodes,5 7 -segment LED displays, 6 LEDs and 1 thermistor.Receiving System Quartz controlled synthesizer,

triple conversion.Frequency coverage 10 kHz to 30 MHz continuous.Preselect°, bands 0.01 - 0.15 MHz (10 . 150 kHz)

0.15 0.5 MHz (150 500 kHz)0.5 - 1.6 MHz (500 1600 kHz)1.6 4.5 MHz4.5 12 MHz12 - 30 MHz

Frequency Display Digital read-out in fire 7 -segmentLEDs, 3/V high.

Sensitivity - AM 50 kHz 30 uV(for 10 dB Signal - 300 kHz 2 uV

to -Noise Ratio) 900 kHz 1 uV3.1 MHz 0.5 uV7.1 MHz 0.5 uV151 MHz 0 5 uV

Image Ratio -

SelectivityWideNarrow

Reception Modes IF - let

2nd3rd

Beat Frequency BFO PitchFrequency Stability

Audio Output Antenna Impedance

Power Requirements

Dimensions

Weight Price

Front panel controls consist of signalstrength and battery meter, preselectortune and dial, preselector band switch,attenuator switch (used to attenuatestrong local signals), a light switch(when using batteries this will save on62

The DX 302 from Radio Shack. John Garner rates

batteries it is also used to checkbattery condition), Selectivity switchfor narrow or wide, BFO Pitch for bestreception of SSB and CW, Digital Fre-quency Readout, Speaker, a jack forheadphones, Mode switch, Volume/Offcontrol, RF Gain control to adjust sen-sitivity of the receiver, and the maintuning - the outer knob for the desiredMHz range and the inner knob for pre-cise kHz tuning.

On the rear panel are two cord wrap-ping posts for portable or batteryoperation, battery compartment, the ex-ternal speaker jack, key jack, tape out-put jack, coax antenna connector, an-tenna screw terminal, ground screwterminal and a mute screw terminal. Thepower cord comes out of the back andis equipped with a three prong plug. A12 volt jack and fuse are also on the rearpanel.

Two antennas are included with theDX -302 - one is a back -of -the -set tele-

18 1 MHzSSB 50 kHz

300 kHz900 kHz3.1 MHz7.1 MHz15.1 MHz28.1 MHz100 kHz300 kHz900 kHz3.1 MHz7.1 MHz15.1 MHz28.1 MHz.6 dB

0.5 uV15 uV1 uV

0.5 uV0.3 uV0.3 uV0.3 uV0.3 uV70 dB70 dB70 de60 dB60 dB60 dB60 dB60 dB

3.5 kHz 6.0 kHz2.5 kHz 4.0 kHzAM, USB, LS13, CW55.5 54.5 MHz

3 2 MHz455 kHz455 kHz 1.5 kHzt 1 kHzWithin 1 kHz per hour after 60minutes warm-up.Within 2 kHz during 10 minutesafter initial turn on.(8 ohms) 1.5 watts maximum.50 ohms for coax connector.Hi -Z for long wire.AC. 120 volts, 60 Hz (2201240volts, 50 Hz for European/Australian models), 15 watts .DC: 8 'C' cells or external 12 voltsnegative ground only, 8 watts max146 min high, 362 mm wide,252 mm deep.6 kilograms.$499.95 Canadian.

taking the trouble to design this new re-ceiver to replace the problem -riddledDX -300.

Thanks to Radio Shack for the use ofthe DX -200 and DX -302 and thanksalso to Roy Stokes, Nandor Petrov,

this one very highly.

copic antenna which is handy for por-table use - the other is a 10 meter longwire which can be used as a temporaryantenna away from your normallistening post.

After an afternoon of listening to theDX -302 I can say that this receiver isa great improvement over the DX -300and for $500. it is well worth themoney. It's nice to see Radio ShackMarc and Bill Butuk for joining with mein this comparative listening test.

Kenwood R-1000This is another receiver that has comeon the market since the October Short-wave Receiver Survey. I haven't had achance to listen to an R-1000 yet butfrom all indications, after a few minorgrowing pains were corrected by Ken -wood, this appears to be another goodreceiver at a reasonable price.

Grant Manning of Radio West hadthis to say about the R-1000 ...

"Introducing a great new all -brandcommunications receiver from a provenleader in amateur radio manufacturing!The R-1000 tunes from 200 kHz to30 MHz continuous, with both analogand digital frequency readout. An easilyprogrammed digital clock is built-in andwill turn your receiver and recorder onand off by simply "punching in" thetimes you desire. The blue-green digitalreadout frequency display doubles asthe clock display by the use of a frontpanel switch.

"This set has one of the best "frontends" seen here in recent years, immuneto cross -modulation and overloading.Additionally, it has very clean audio!"

The R-1000 specifications are shownin Table 3.

Radio West, 3417 Purer Road,Escondido, CA 92025, USA offer amodified R-1000 with improved Selec-tivity for $445. US. This of course, doesnot include the exchange rate on theCanadian dollar and any import duties.

A 20 page catalog is available fromRadio West at the above address. Thiscatalog lists a number of receivers, bothstock and modified by Radio West, andaccessories for the shortwave listener.When writing them, mention ETI.

Next month I will return with somemore tropical band information. Untilthen, 73 and good listening.

ETI-JULY 1980

The Radio Shack DX 290.

Table Ill, R1000

Fraquancy Range Modes of Operation

y

Soleetigity

Sansitriry

Output Impedance -

Power Requt,einents

Dimensions

WeightPrice

200 kHz to 30 MHz.AM, SSB, CWwithin 300 Hz during any 30 mineta period attar warm-up.AM Wick 12 kHz 0 .6 dB,25 KHz 0 .50 dB;AM Narrow 6 kHz 0 .6 dB.18 kHz 0 -50 dB,SSB/CW 2.7 kHz 61 .6 dB,5 kHz .50 dB200 kHz to 2 MHz SSB 5 uy,AM 50 uV2 MU: to 30 MU: SSB 0.5 eV,AM 5 uVIS N N 10 dB or more)4 to 16 ohms, external speaker orheadphone.100/120/220/240/ V AC, 50/60 Heat 1.5 Watts.300 met wide, 115 mm high,218 mm deep5.5 kolograins.Approximately $650. Canadian

The Kenwood R-1000, shown here with the optional SP -1000 speaker.

Continued from page 40

AudioToday LettersCase Of The Missing Speaker,And Other TalesI have two 65 Watt speakers but I haveonly got a Simpson Sears 12 Watt amp-lifier. The problem is that the cheapamplifier cannot bring out the sound. Iam interested in getting information onILP modules to finish my stereo system.I do not know the proper size amplifierfor two 65 Watt speakers or the pre -ampor whatever else is needed. Informationon the equipment would be appreciated.

I also have a Peavy amplifier, 200Watts RMS. The speaker is gone. It's aSession 400. The amplifier output re-quirement is for 4 ohms, and has out-put for two speakers. Hope you wouldhave information on maybe, SRO Altecspeakers with the required wattage.

This amplifier has high range and agood speaker is required.

I don't know Oaktron speakers butthat 300 Watt speaker interests me.

B. H., Liverpool, N.S.

The question is, where did the speakergo? Does it have any friends it mighthave confided in? Did it run off to Van-couver? Or even Toronto! Quick, chief,signal the Dynamic Duo. Speakermanhas struck again.

I've never heard of Session speakers.If you mean a Celestion Ditton 400,I've no references to that model. Ifthat's it, contact Rocelco Inc., at 1669Flint Road, Downsview Ont., M3J 2H7.

For information on ALTEC, contactAltec Lansing of Canada, Ltd., 151Carlingview Drive, Rexdale, OntarioM9W 5E7.

I can't lay my hands on the relevantliterature at the moment, but, unlessI'm mistaken, the SRO Line is a pro-fessional line by Shure. If that's whatyou want, contact A.C. Simmonds &Sons, 975 Dillingham Road, Pickering,Ontario L1W 3B2.

Oaktron is available from Omni-tronix Ltd., 2056 Trans Canada High-way, Dorval, Quebec H9P 2N4.

ILP Modules are distributed byAudiex Electronics, 1736 Avenue Road,Suite B, Toronto, Ontario M5M 2N4.

Several of the above are also onbingo cards in some issues of ETI, but ifyou want specifics on particular pro-ducts it might be best to write.

I really wish manufacturers wouldstop describing their speakers in termsof wattage rating. It's a meaninglessterm by itself and says absolutelynothing about the product, althoughperhaps a great deal about the manu-facturer or the pointy -headed types inthe advertising agency.

Generally speaking, you don't need65 Watts for a so-called 65 Wattspeaker, but this might be the maximumcontinuous power it can handle, or itmight be a recommended amplifier, oranything. If you want to use them com-mercially, I wouldn't use more than 65

to 100 Watts, but for home use, as-suming normal levels, rather thantrying to run a radio station without atransmitter, even 200 Watts might bequite safe. More important in deter-mining what you need is the sensitivityof the speaker. Generally speaking, I

prefer some degree of overpower, to re-duce the chances of tweeter burnout(tell you why in a later column) and, forrecords, an infrasonic filter to protectagainst overload due to record warp.This is especially important with ventedspeakers.

I've never heard of a Peavy, but ifit's a 200 Watts mono, or 200 Wattsper channel stereo, the 4 ohm figure isprobably a minimum load. That mightalso be the impedance at which itspower is rated. You can go to a higherimpedance such as 8 ohms, or even twoin parallel, as long as the total is not lessthan 4 ohms, but the higher impedancewill give lower maximum power. Itshould not affect the sound level, if wedisregard speaker sensitivity. Of course,if it's 100 Watts total (both channels)4 ohms, that means 100 Watts per chan-nel, and maybe 50 Watts per channelinto 8 ohms. If that figure is with bothchannels driven, fine, but if not, youmay have to derate to 35 Watts perchannel. This assumes we mean RMS. Ifpeak power is used for rating, make thatcloser to 20 Watts.

Numbers can be fun..

ETI-JULY 1980 63

Simple Cassette InterfaceElmer BulmanWhen your programs develop to the,length that it becomes a chore to re-en-ter on a key board, these circuits willtide you over until you can afford some-thing more elaborate in software stor-age.

The record circuit provides a burstfor a one and silence for a zero. The in-put gating provides software control,the 555 provides the burst and the out-put circuit shapes the square wave to atriangle wave at a level suitable for therecorder input.

The playback circuit consists of rec-tification and precise filtering for theinput to the Schmitt Trigger. The out-put of the 3900 is then gated for soft-ware control.

The burst frequency (555) will de-pend on the quality of the recorderavailable to the user. The higher the fre-quency you can retrieve the better. Todetermine a suitable baud rate simplyallow a minimum of ten cycles in theburst. Needless to say your start bitsmust be high and the remainder is soft-ware.

EARPHONEOUTPUT

1N914

5n0

SERIAL OUT()

FLAG/00

2M2

3

7402

24

D

RECORD

+5

14

820k100k > R4

PLAYBACK

3

%7402

7.13

11

10

11-)D-. 6iICA

FLAG

4k3

FOR 100 BAUD OPERATION(NOTE FLAG 0 IS USED FOR

82k START BIT, PARITY ETC.)

5n05 1n0 I

I

FLAG 1Ck-IC4

OUTPUT=SERIAL OUT+FLAG 0

100k

50n

10k

10k

14740014

10

3

MIKEOR AUXINPUT

SENSE A

IC4 13 SERIAL INd

12 T-7

SENSE A DETECTS START, PARITY ETC.SENSE A=IFLAG1HDATA)SERIAL IN=IFLAG2IIDATA)

Function GeneratorJ. S. Paterson

IC1 is an integrator which, along withIC2, etc, forms a voltage controlledramp oscillator, the frequency ofwhich is set by RV1. S1 and diodesD1, 2 control the direction of theramp. The output of IC2 is taken toIC3, which is a comparator providinga square output at pin 6. RV2vides control of symmetry. Lastly, thissquare wave is fed to an integrator,which gives a triangular waveform. Ifthe control voltage is applied via thecircuit in Fig. 2 the frequency will varylogarithmically with voltage - usefulfor synthesizers.

With RV1 slider grounded, a rampcan be fed into the circuit at point A,so the oscillator will sweep through itsrange - useful for testing filters, etc.

TRIANGLEOUT

0

2k2

64 ETI-JULY 1980

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111

I-ETI-JULY 1980 Circle No. 18 on Reader Service Card. 65

Elementsof Electronics

Book 1 (BP 62) introduces the reader to thenature of electricity, it's sources and simpleelectronic circuitry. Additionally thereare chapters on components, electricalsafety and electronic math.

Book 2 (BP63) delves into the secrets ofAC current theory. Attention is paid toresonance and Q -factors, impedance, phasordiagrams and transformers. Includesample mathematical appendices.

Book 3 (BP64) centres on semiconuctortheory. Chapter 1 starts at the physics andapplications theory of semiconductors.Other subjects include diodes, transistorsand FETs. Applications studied includerectifiers, amplifiers, oscillators, switchingand IC techniques.

To order please use the card facing page 44or send to:

ETI Magazine,Unit 6,25 Overlea Boulevard,Toronto, Ontario, M4H I B1

Your Toolbox Test Bench

Model 216 Transistor Testerwith fast, automatic switchingfor instant good -bad analysis ofNPN's, PNP's, FET's, diodes andSCR's in or out of circuit.$150.00

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Armed with only two portablements, you can now trace logic levelsthrough the most popular types oflogic circuitry... TTL, MOS, CMOS,even HTL and HiNIL.

The new B&K-PRECISION DP -100is a digital pulser probe that's a greataid to fast analysis and debugging ofintegrated circuit logic systems.Simple to operate, the DP -100 can beused alone or with a logic probe oroscilloscope. It generates a "oneshot" pulse train at a 5 Hz rate andsenses circuit conditions to pull anexisting high state to a low or a lowstate to a high.

The B&K-PRECISION DP -50 is thedigital probe that offers more thanlogic. In addition to logic status, it ac-tually displays pulse presence to 50MHz. The intensity of its PULSE LEDreveals the duty cycle of the signalobserved.

Both the DP -50 and DP -100 arewell protected against overload andaccidental polarity reversal. You cansee the logic of it all today! Contactyour B&K-PRECISION distributor forimmediate delivery.

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TECH TIPS

GSR Meter

D.Chivers

The galvanic skin response meter is

probably the easiest both to constructand to use. Fig.1 uses a single 2N3704 -incidentally, the meter used was simplythe 1mA range of a multimeter. Whilethe circuit shown had the requiredsensitivity, it was not selective enoughand under all sorts of stresses and strainsthe needle refused to budge from a setposition. The darlington pair configur-ation of Fig.2 greatly increases sensi-tivity and the 100k pot will bring thereading down to a usable level - with-out this, the current passing through themeter would be about 30mA. Thismodified circuit proved to be amplyselective.

Fo,r use as probes, silver foil tapedonto the tips of the first and secondfingers proved to work well, though formore permanent use steel gauze is

recommended. Naturally the hand mustbe kept as steady as possible duringexperiments.

First experiments proved highlysuccessful; the meter needle drifted atfirst and frequent use of the sensitivitycontrol was required, but after a fewminutes the

Since the needle responds to stresswithin the body or mind, it is easy tomake it move; talking, thinking hard orbiting a finger all cause the needle tomove up, making it go back down by

External Input For MicrosP. F. Tilsley

EXTERNALINPUT

100k

+5V

1/6 4050

TO STANDARDGENERAL PURPOSEINPUT PORT

OV

This simple circuit provides a microwith an 8 bit switch /external signalinput port. The state of the switchescontrols the byte read by the micro,but any totem pole TTL signal appliedto the external input socket over -ridesthe signal from the correspondingswitch. The value of the resistor is notas critical. The circuit is shown foronly one bit.

NOTE:Q1-2: 2N3704 OR SIMILAR

removing the factor causing the stress.Moving the needle below its mean valuewas far more difficult especially whilewatching the meter and actually tryingto relax - in fact to start with this

actually caused tension. The easiest wayto do this is to simply close the eyes andrelax, while an observer takes note ofthe results. On opening the eyes thereading would jump up to what it hadbeen before relaxation commenced.

This circuit will of course functionas a [lie detector but since stress is

caused by any question the results arenot too reliable and certainly of nosignificance.

An unexpected use for the circuitof Fig.1 is that of a transistor tester. Ifa fixed value resistor of about 2M2 isused in place of the pot the gain of thetransistor may quickly be tested; FSD=approx. hfe 250. For NPN transistors,polarity of the meter and battery mustbe reversed.

Tech -Tips its an ideas forum and is notaimed at the beginner; we regret that wecannot answer queries on these items.We do not build up these circuits priorto publication.

ETI is happy to consider circuits orideas submitted by readers; all itemsused will be paid for. Drawings shouldbe as clear as possible and the textshould be preferrably typed. Anythingsubmitted should not be subject to copy-right. Items for consideration should besent to the Editor.

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ETI-JULY 1980Circle No. 15 on Reader Service Card.

67

WIN! an $8950o 'SCOPEWhen a magazine like ETI and a company like Omnitronix get together, you never

know what might happen!To celebrate their tenth anniversary Omnitronix is putting a Leader 'scope up for

grabs. Flushed with the excitement of our last two contests, we at ETI couldn't pass upthe chance to throw another.

This scope is no lightweight either. The LBO 514 is a 10 MHz, dual trace oscillo-scope. Minimum vertical sensitivity is 1 mV/DIV. Maximum sweep speed is .5 us/DIVand the instrument is capable of all modes of triggering, including chopped and alternatemodes. The LBO 514 retails for $895.00, some lucky ETI reader will get one free!

Now to the contest. In order to ensure that the most deserving person wins, we haveput together an exercise in waveform analysis. The scope traces shown below at left arethe result of 1 kHz square wave being put through one of the simple circuits at right.That's all! Additionally, you might want to know that the square wave had an amplitudeof 10 Vpp and came from a 600 R source. Those values however are not really necessary.When you've got the right picture with the right schematic, fill in the form and send it into us.

a

C

e

b

d

f

1750m H

0

IN 360p OUT IN10n

12k OUT

0- 0

0 -

IN

0

0

IN

o- -

3 4C'---- \AAA/NAr

68IN;Ar-r° 12k10n T OUT IN 10n

0 0

5 6H

360p150n OUT IN 750m H

1N4001

0-

T0

OUT

0

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All entries become the property of Omnitronix Limited.Contest closes August 15th, 1980.Editor's decision is final.

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68 ETI-JULY 1980

PanasonicJust sightly ahead of our time

LIGHT SCOPEFF 393E

30 POWER

Illuminatessubject. Uses 2"AA" batteries(included).

FOR

'ScienceHobby ExperimentereFun!!

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Chargex (Visa) accepted. Include expirydate, card number, bank name andsignature on all card orders. Ontarioresidents add 7% PST. Or mail moneyorder to:

ROUE VIEW EliECCROIIICS2327 Bloor St. W.

Toronto, Ontario M6S 4W1Phone: (416)762-8655

MOREIAlt

New versatile, flexible, single 10resistors 1/2w 1%. Modular DecadeResistance Boxes in a convenientsize: 70x50x25 mm. Boxes plug intoeach other for compact designtest set up. The use of short testleads results in less noise pick up,less coupling and less lead induc-tance. Order 2 boxes and graduallyexpand your set to 7 (1 ohm to10 M ohms). Patented.Assembled box $20.50and kit $14.95Compatible modular plug-in meter:5, 50, 500 mA D.C.assembled only $21.50

Ontario Res. add: 7% PST plus$1.00 postage and handling. Dealerenquiries welcome.

POMIARP.O. Box 458, Downsview,Ontario, Canada. M3M 3A8

BUILD YOUR OWNAND SAVE!

140W DC Class AB Stereo Amp $129.0030W + 30W Stereo Amp . . . $69.001,00W Class A Power Amp . . $39.00DC Stereo Pre -Amp $79.0060W DC Class A Power Amp $58.007.0W Class AB Power Amp . . $41.0060W Low T.I.D. Power Amp $32.00I.C. Stereo Pre -Amp $43.0010 Band Graphic Equalizer . . $42.0015 Steps Power Level Indicator $56.001.2 Steps Power Level Indicator $34.00S.E.A. Level Display $69.00Stereo Speaker Protector $19.00Rack Mount Cabinets:16m(W)x4"(H)x8"(D) . $39.001.9"1W)x4"(1-1)x12"(D) $54.001.9",W)x7"(H)x12"(0) $74.00

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AUDIOVISION SERVICEP.O. Box 955, Station B,

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Circle No.10 on Reader Service Card.Retailers: Write for wholesale price list.

SUPERBOA RD II

$ 415* x.:nunult1.10" NOII SU

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$1,340C8P DF 32K RAM, DUAL 8" FLOPPIES

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* Ontario residents add 7% Sales Tax.Prices subject to change without notice.Master Charge or Visa accepted. Shippedcollect by any method you specify.

D.C.B.ELECTRONICS333 Denison St. Unit 3, Markham,Ontario L3R 2Z4 (416) 495-1599

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The B&K-PRECISION Model 3020sweep/function generator is the mostversatile signal source in its price range.This instrument alone can replace afunction generator, sweep generator,pulse generator and toneburstgenerator. Frequency coverage spans0.02Hz to 2MHz in seven ranges, eachwith linear 1000:1 frequency control.

A low -distortion, high -accuracy signalsource, the 3020 can generate almostany waveform, including sine waves,square waves, TTL square waves, tone -burst, pulses and ramps. All can be in-verted. Internal linear and log sweepcapability is also featured. Both modula-tion and carrier levels can be varied soeven a double sideband suppressed car-rier test signal can be generated.

For applications requiring standardsignals, the Model 3010 low distortionfunction generator is offered. The 3010generates sine, square, TTL square andtriangle waveforms from 0.1Hz to 1MHz insix ranges. An external VCO input is pro-vided for sweep frequency tests. VariableDC offset is included.

The 3020 and 3010 are available forimmediate delivery at your local dis-tributor. A ten day free trial is available atmany locations.

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ETI-JULY 1980 Circle No.7 on Reader Service Card.

CLASSIFIED

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for Ell

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The giftfor allseasons...

the gift of lifeBe a RED CROSSBlood Donor

PRINTED CIRCUIT BOARDS - 2 sided1 oz glass epoxy 6"x12" - 5 for $13.75Postage paid, send certified cheque ormoney order, B.C. residents add 4% salestax. CYCLOPS ELECTRONICS LTD., P.O.Box 4089, Vancouver B.C. V6B 3Z6

CAR STEREOS, Tape decks & RadiosRepaired sold & installed. Send your repairsto us and we will return ship anywhere.TAPE CAROUSEL LTD., 627 King St. E.,Kitchener, Ontario N2G 3M2. (519) 745-3671.

PRINTED CIRCUIT boards from yoursketch or artwork. Affordable prices. Alsofun kit projects. Free details. DANOCINTHSINC. Dept. ETI, Box 261, Westland MI.48185. U.S.A.

WSJ RADIO - SWL Radios - Ham radios18 Sheldon Avenue North, Kitchener,Ontario N2H 3M2. Tel. (519) 579-0536.Write for giant catalogue, free of course!!(VE3EHC).

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QUALITY printed circuit boards for allETI projects. Overspeed Alarm $4.19,Tape Noise Reducer $7.99, FunctionGenerator $17.99, Ontario residents pleaseadd 7% sales tax. Large selection of partstoo. Transistors, resistors, TTL, CMOS,Linear IC's capacitors and more. Writefor complete information to WENTWORTHELECTRONICS, R.R. 1, Waterdown,Ontario LOR 2H0.

CASSETTE ADAPTOR allows you to playcassette tapes in any 8 -track player. Sendpayment of $59.95 + $4.20 tax (total$64.15) and we will ship prepaid to you.TAPE CAROUSEL LTD., 627 King St. E.,Kitchener, Ontario N2G 2M2.

COMPLETE Electronic Hobby Services.Custom Kits, circuits, technical writing,special parts, original designs. Free informa-tion. TEKNIKIT ASSOCIATES, 301 FloraSt., Carleton Place, Ontario, K7C 3M8.

J&J ELECTRONICS LTD., P.O. Box1437E, Winnipeg, Manitoba R3C 2Z4.Surplus Semiconductor Specialists. Do youget our bargain flyer? Send $1.00 to receivethe current literature and specials and to beplaced on the mailing list for future pub-lications.

WE SELL SERVICE! Professional repairsto all types of equipment: amateur, comm-ercial, avionics, marine, CB, broadcasting.We stock Japanese transistors! ServiceDivision, HAMTRADERS INC., 18-45 Bris-bane Road, Downsview, Ontario. M3J2K1. 416-661-8800: Telex 065-22234.

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Whatare wedoing about it?Contact your local Multiple Sclerosis Societyof Canada Chapter.

70 ETI-JULY 1980

Babani Books From ETIPlease order by number using the handy order card in this issue.

IC 555 Projects BP44 Every so often a device appears that is so useful than one wonders flown.went on before without it. The 555 timer is such a device. It was first manufactured by Signetics, but is now manufactured by almostevery semiconductor manufacturer and is inexpensive and very easilyobtainable. Included in this book are Basic and General Circuits. Motor Car and ModelRailway Circuits. Alarms and Noise Makers as well as a section on the556.558 and 559 timers.II An invaluable addition to the library of all those interested in Electronics.

$7.25 plus 30c postage and handling.

52 Projects Using IC741 BP24 IC741 is one of the most popular. inexpensive and easily obtainabledevices available to the home constructor. It is also extremely versatile andcan be used in a great number of various applications. This unique book, originally published in Germany, shows fifty-twodifferent projects that can be simply constructed using only the IC741 and afew discrete components. An invaluable addition to the library of all those interested in electronics.

$3.95 plus 30c postage and handling.

Mobile Discotheque Handbook BP47 The vast majority of people who Stan up "Mobile Discos" know very littleabout their equipment or even what to buy. Many people have wasted a"small ortune" on poor, unnecessary or badly matched apparatus. The aim of this book is to give you enough information to enable you tohave a better understanding of many aspects of "disco" gear The approach adopted is to assume the reader has no knowledge andstarts with the fundamentals, hopefully theexplanationsgivenare simplifiedenough for almost anyone to understand but please not that this is by nomeans the full story. The book is divided into six parts - Basic Electricity, Audio, AncillaryEquipment. Cables and Plugs, Loudspeakers. Lighting Equipment and theinformation has been considerably sub -divided for quick and easyreference.

$5.60 plus 30c postage and handling.28 Tested Transistor Projects No.221 Mr. Richard Torrins is a well experienced electronics developmentengineer and has designed, developed. built and tested the many useful andinteresting circuits included in this book. Some of the circuits are completely new and, to the best knowledge of theauthor, unlike anything previously published while others many bearsimilarity to more familiar designs. The projects themselves can be split down into simpler building blocks,which are shown separated by boxes in the circuits for ease of description,and also to enable any reader who wishes to combine boxes from differentprojects to realise ideas of his own. Most of the circuits are very economical on the use of components and inmany cases the semiconductors employed are non -critical, commonlyavailable and inexpensive types.

$5.20 plus 30c postage and handling.

First Book of Transistor Equivalents BP1and Substitutes ShOws alternatives and equivalents to many popular transistors made inGreat Britain. U.S.A., Europe, Japan and Hong Kong etc. Companion Volume to BP14 - SECOND BOOK OF TRANSISTOREQUIVALENTS AND SUBSTITUTES An invaivable addition tothe library of all those interested in Electronics bethey amateur or professional.

$2.50 plus 30c postage and handling.Second Book of Transistor Equivalentsand Substitutes BP14 Shows alternatives and equivalents to many popular transistors made inGt. Britain, U.S.A., Europe, Japan and Hong Kong etc. Companion Volume to BPI - FIRST BOOK OF TRANSISTOREQUIVALENTS AND SUBSTITUTES All invaluable addition to the library of all those interested in glectronics bethey amateur or professional.

$4.50 plus 30c postage and handling.

Radio Circuits Using IC's BP46. This book describes integrated circuits and now they can be employed inreceivers for the reception of either amplitude or frequency modulatedsignals. The chapter on amplitude modulated (a.m.) receiverswill beef mostinterest to those who wish to receive distant stations at only moderate audioquality, whilst the chapter on frequency modulation (f.m.) receivers willappeal to those who desire high fidelity reception of local 0.6.1. stationspossibly with stereo (and even quadrophony at some future date). Stereodecoder circuits and the devices available at present for quadrophoniccircuits are discussed. Voltage regulator devices are also covered becausethey are so convenient in all varicap tuned receivers and because they haveso many applications in all types of circuit. Brian Dance is a highly experienced author who regularly contributes tomany of the popularelectronic magazines that are available both in the U.K.and overseas. An extremely valuable addition to the library of all Electronicsenthusiasts.

$5.60 plus 30c postage and handling.

These books are specially imported from Englandby us. If someone has already used the card. writeto ETI Magazine, Unit 6, 25 Overlea Blvd. Toronto.Ontario M4H 1B1.

50 (FET) Field Effect Transistor Projects BP39 Field effect transistors (FETA) find application in a wide variety ofcircuits. The projects described here include radio frequencyamplif leis andconverters, test equipment and receiver aids, tuners, receivers, misers andtone controls, as well as various miscellaneous devices which are useful inthe home. It will be found that ingeneralthe actual F.E.T. used is notcritical and manysuitable types will perform satisfactorily. The F.E.T. is a low -noise. highgaindevice with many user.. and the dual gate F.E.T.is of particular use for mixerand other applications This book contains something of particular interest for every class ofenthusiast - shortwave listener.. radio amateur, experimenter or audiodevotee. A valuable addition lo the library of all electronic enthusiasts.

$5.20 plus 30c postage and handling.

Popular Electronic Projects BP49 Included in this book area collection of the most popular types of projectswhich. we feel sure, will provide many designs to interest all electronicsenthusiasts. All the circuits utilise modern, inexpensive --in freely availablecomponents The 27 projects selected cover a very wide range and are divided into fourbasic areas. Radio Projects, Audio Projects. Household Projects and TestInstruments. An interesting addition to the library of both the beginner and moreadvanced constructo.

$5.95 plus 30c postage and handling.

Electronic Music and Creative Tape RecordingMusic a the new music of the 20th Century II plays a large pan

in "Pop" and "Rock" music and. in fact, there is scarcely a group withoutsome sort of electronic synthesiser or other effects generator.

It is possible with relatively simple apparatus to create completecompositions using electronic and sometimes non -electronic musicalsources. This book sets out toshowhow Electronic Music can be made at hornevviththe simplest and most inexpensive equipment It describes how the soundsare generated and how these may be recorded to build up the finalcomposition With the constructor in mind, several ideas are given to enable a smallstudio to be built including a mixer and various sound effect units

Circuits are included for VCO5, VCAs, Envelope Shapers. VCFs. Activeand Passive Mixers, Fun. Noise Generators. Metronomes and a 10 -NoteProgrammable Sequencer etc.

All the units shown have been successfully built and used by the authorand most of the projects can be built by the beginner. An unusual. fascinating and highly rewarding application of electronics.

$5.20 plus 30c postage and handling. BP51

IC LM3900 Projects BP50 The purpose of this book is to introduce the LM3900 to the Technician,Experimenter and Hobbyist. It provides the groundworkfor both simple andmore advanced uses and is considerable more thanjust &collection of simplecircuits or projects. The LM3900 is different from conventional 'Op -Amps' it can be used formany of the usual applications as well as many newones. It ;sone of the mostversatile, inexpensive and freely available devices on the market today. The book is divided into six basic sections: -

IntroductionAudio Applications

Simple Linear ApplicationsSimple Digital ApplicationsSignal Generator Circuits

Special Applications The LM3900 can do much more than is shown here - this is just artintroduction. Imagination is the only limitation with this useful device, butfirst the reader must know the basics and that is what this book is all about.

$5.60 plus 30c postage and handling.

1st Book of HI -Fl Loudspeaker EnclosuresII Contains 26 practical designs and over 40 drawings to enable theenthusiast to construct his own Hi-Fi Loudspeaker enclosures.II Includes the following types Of enclosures -Corner Reflex. Bass Reflex, Exponential Horn, Folded Horn, Tuned Port.Klipschorn Labyrinth. Tuned Column. Loaded Pon, MultispeakerPanoramic etc. Also covers general construction hints and embellishing Of cabinets aswell as a considerable amount of other useful information. A must for the library of all audio enthusiasts.

N0.205$3.25 plus 30c postage and handling.

50 Simple L.E.D. Circuits BP42 The author of thin. book, Mr. R.N.Soar, has compiled 50 interesting anduseful circuits and applications, covering many different branches ofelectronics, using one of the most inexpensive and freely availablecomponents - the Light Emitting Diode (L. ED.) Also includes circuits for the 707 Common Anode Display. A useful book for the library of both beginner and more advancedenthusiast alike. Companion volume to book No. BP36 - 50 CIRCUITS USINGGERMANIUM, SILICON 8 ZENER DIODES by the same author.

$3.25 plus 30c postage and handling.

Handbook of IC Audio Preamplifier &Power Amplifier Construction BP35 Shows what audio IC's are, as well as how to use them. Includes practical constructional details of various IC and HybridIC/Transistor designs of about 250mW to 100W output This book is written by the very experienced and popular author Mr. F.G.Rayer who deals with the subject in four pans:Part I Linderstanding Audio IC'sPart II Preamplifiers. Mixers and Tone ControlsPart Ili Power Amplifiers and SuppliesPart IS Hybrid Circuits An real book for both Deal niter and advanced enthusiast aiike.

$5.20 plus 30c postage and handling.

50 Projects Using Relays SCR's & Triacs BP37 Relays, silicon controlled rectifiers (SCR's) and hi -directional triodes(TR laCs) hawse wide range of applications in electronics today. These mayextend over the whole held of motor control; dimming and heat control;delayed, timing and light sensitive circuits andinclude warning devices.various novelties. light modulators, priority indicators. excess voltagebreakers etc. In this book, the very experienced and popularauthor - Mr. FG. Rayer -has !given hied and practical working circuits which should present theminimum of difficulty for the enthusiast to construct. In most circuits there is a wide latitude in component values and types,allowing easy modification of circuitsor ready adaption of titer.° individualneeds. Arr ideal book for both beginner and advanced enthusiast alike.

$5.20 plus 30c postage and handling.50 Projects Using IC CA3130 No.223 The CA 3130 is currently one of the more advanced operational amplifiersthat is availabletothe home constructor. This means that it isoftencapableofa higher level of performancethan many otherdevicesand that itoften needsfewer ancillary components.III In this bock Mr. R.A. Penfold has designed and developed a number ofinteresting and useful projectswhich are divided intof eve generalcategories.I Audio ProjectsII R.F. ProjectsIII Test EquipmentIV Household ProjectsV Miscellaneous Protects An ideal book for both the beginner and more advanced enthusiast alike

$5.20 plis 30c postage and handling.Electronic Projects for Beginners BP48 In nes book the newcomer to electronics will find a wide range of easilymade projects, many complete with actual component end wiring layouts.Furthermore, a number of projects have been arranged so that they can beCOrtattuCted without any need for soldering and, thus, avoid the need for asoldering iron.IN This book which is written by the veryexperienced author Mr. F.G. Rayerisdivided into four sections:

"No Soldering" Projects2. Miscellaneous Devices3. Radio and Audio Frequency4. Power Supplies

An absolute 'must' for all beginners in electronics.

$5.60 plus 30c postage and handling.50 CMOS IC Projects No.224 CMOS IC's are probably themostversatilerangeoldignaldevicesfor useby the amateur enthusiast. They are suitable for an extraordinarily widerango of applications and are now also some of the most inexpensive andeasily available types of I .0 In this book Mr. R.A.Penfold haS designed and developed a number ofinteresting and useful projects which are divided into four generalcatagones:I MohnnbratOrSII Amplifiers and OscillatorsIll Trigger DevicesIV Special Devices An ideal book for both the beginner and more advanced enthusiasts alike.

$3.95 plus 30c postage and handling.Electronic Calculator Users Handbook BP33III An invaluable book for all calculator users whatever their age oroccupation. or whether they have the simplest or most sophisticated ofcalculators Presents formulae, data methods of calculation, conversion factors etcwith the calculator user especially in mind, often illustrated with simpleexamples.Includes: The way to calculate, using only a simple four function calculator:Trigonometric functions (sin, cos. tan)Hyperbolic functions (sinh, cosh. tenth)Logurithrns, square roots and powers. A comprehensive section of conversion factors covering such commonconversions as length. area, volume and weight etc. through to morespecialised conversions such as viscosity. illumination. and cargo shippingmeasures etc. Formulae and data for VAT, discounts and mark up. currency conversion.II-items:it, solutions of equations, binary and octal numbers, areas andvolumes, statistics and mathematics etc.

$3.95 plus 30c postage and handling.

ETI-JULY 1980 71

0---tActivenent,,,c.orp.

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Bi-Fet OP AMPSTL064CN 2.75 Quad low power TL081CP .49 J-FET inputTL071CP .59 Low noise TL082CP .99 Dual J-FET inputTL072CP 1.19 Dual low noise TL084CN 1.95 Quad J-FE1 inputTL074CN 2.35 Quad low noise

1980 IC MASTERover 2700 PAGES

Complete integrated circuit data selector. Mastergarde to the latest including microprocessorsand consumer circuits. 45.000 device types listed5.000 new device types added. Complete new sec -non on MPU boards 8 Systems.

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LINEAR I.C.'sLM301AN-8 34LM304CH .89LM307N-8 .29LM308N-8 .89LM308CH .95LM309K 1.29LM310HC 1.49LM3I1N-8 .59LM317T 1.49TO -220)

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LM723CHLM723CN-14LM725CN-8LM733CN-14LM739CN-14LM741CHLM741CN-8LM747CN-14LM748CN-8TBA810DASLM1458N-8LM1488N-14LM1489N-14LM3046N-14LM3302N-14LM3403N-14LM3900NLM4136N-14ULN2003AN

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1.29 CD4024BE .79 CD4050BE .69 CD40868E .95 CD4528BE .99.29 CD4025BE .39 CD4051BE .99 CD4093BE .79 CD4531BE .99.84 CD4026BE 1.79 CD40528E 1.25 CD4099BE 1.75 CD4532BE 1.50.69 CD4027BE .49 CD4053BE 1.25 CD4104BE 2.95 CD4539BE 1.15.69 CD4028BE .89 CD4060BE 1.99 CD4502BE 1.45 CD4543BE 1.65.49 CD4029BE 1.29 CD4066BE .89 C04508BE 1.99 C04553BE 3.95.39 CD4030BE .79 CD4068BE .34 CD451OBE 1.25 CD4555BE .89.59 CD4033BE 1.79 CD4069BE .34 CD451tBE .99 CD4556BE .89.89 CD4034BE 2.99 CD4070BE .49 CD4512BE .99 CD4581BE 2.25.89 CD4035BE 1.39 CD4071BE .39 CD4514BE 2.45 CD4582BE .99.59 CD4040BE 1.89 CD4072BE .29 CD4515BE 2.45 CD4584BE .89.89 CD4041BE 1.75 CD4073BE .54 CD4516BE 1.75 CD4585BE 1.50.89 CD4042BE .89 CD4075BE .59 CD4518BE 1.25 CD4702BE 9.9589 CD4043BE 99 CD4076BE 1.29 CD45I9BE 89 CD4724BE 1 95

1 39 cc.ic 1 :BF 99 CD1076RF 45 CD46,00F 1 25

PLASTIC POWERTRANSISTORS

TIP29 .39 NPN 1 AMP 100VTI P30 .39 PNP 1 AMP 1005TIP31 .42 NPN 3 AMP 100VTIP32 .43 PNP 3AMP100VTIP41 .59 NPN 6 AMP 100VTIP42 .64 PNP 6AMP 100VTIP115 .59 PNP 2 AMP 60VTIP120 .64 NPN 5AMP 60VTIP122 .74 NPN SAMP 100VTIP125 .74 PNP 5AMP 60VTIP127 .85 PNP 5AMP 1005np2956 .83 PNP 15AMP 605TIP3055 .70 NPN 15 AMP 60VF73055 .59 NPN 10 AMP .

LED209LED211LED212

LED220LED222LED224

FNC1357FND367

FND500FND507END560

FND567

0L704DL707DL747

ILD74IL074MCT6TIL1114N264N324N334N364N37

OPTO SALEL.E.D. LAMPS

T-1 3 mm RedT-1 3 mm GreenT-1 3 mm Yellow

T-1% 5 mm RedT-1% 5 mm GreenT-1% 5 mm Yellow

.09

.19

.14

.11

.24

.16

DISPLAYS375" Common Cathode .99360' Common Cathode

(high brightness)1.24

500' Common Cathode .99500" Common Anode .99500" Common Cathode

(high brightness)1.24

500" Common Anode(high brightness)

1.24

300" Common Cathode 1.29300" Common Anode 1.29630" Common Anode 2.29

ISOLATORSDual Opto Isolator 1500V 1.29Quad Opto isolator 1500V 3.95Dual Opto Isolator 1500V 1.29Opto Coupler 1500V .54Opto Isolator 2500V .54Opto Isolator 2500V .69Opto Isolator 1500V .65Opto Isolator 2500V .79Opto Isolator 1500V .85

74LS447N .59BCD to 7 segment decoder/driver oic

Wcunnionsaiesl,

MINIMUM MAIL ORDER S10.00Add 52.00 to cover postage and,handlIng.

PRICES ARE IN U.S. FUNDS. F.O.B. CANADAFederal Sales Tax (91..) and ApplicableProvincial Sales Tea Extra.

11 payment to be made In Canadian Funds anapproximate 20. conversion rate will be added attime of purchase.

5651 FERRIER ST. 4800 DUFFERIN ST.MONTREAL. QUEBEC DOWNSVIEW. ONTARIOH4P 2K5 M3H 5S9Tel.: (514) 731-7441 Tel (416)661-1115

LARGE INVENTORY AT ALL LOCATIONS

STORE HOURS:Monday to Wednesday 8:30 am - 800 pmThursday and Friday 8:30 am - 9:00 pmSaturday 9:00 am - 800 pm

BAXTER CENTREt 050 BAXTER ROADOTTAWA. ONTARIOK2C 3P2Tel.. (6131 820-9471

3070 KINGSWAYVANCOUVER. B.0V5R 5J7Tel (6041 438-3321

OrldSte., Cha:::11

Circle No.20 on Reader Service Card.