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T1RADIOriLECTRONICS

WORLD

AUSTRALIACANADA $2.95c

EIRE E1 26 5NEW ZEALAND $2 20c

HOLLAND F7.15

85p

INSIDE COLOURTV CAMERAS

UK FIRSTbm Transverter

PROJECTSPP METER

NI -CAD CHARGER

1MIIMMEMIIM11111111111 IMM =11 , miali ...1111111111111111111111111111111111111111111111M1111111 :;w Ji II 11 1 =11 n 111111111111111M11111111111111M11111111111111M1111111 r as 'I VIIMMMIMMIMMIMMMInoMMIMMIMMIMMIMIMIMMEMMEMMNINIMMIIMMINIMMEMIMMINIMMMIN

TV & FM Test

Colour Bar Pattern Generators Sweep and Marker Generator CRT Tester Field Level Checker Signal Level Meter High Voltage Metered Probe Signal Generators

Audio Test

When you select an instrumentfrom the Leader range, you getmore than just sound engineering.That's guaranteed - by rigorousquality assurance at manufacture,and a one year warranty.A broad range that covers mostareas of test, measurement andcalibration, with advanced featuresand high specification asstandard. Prices that are lowerthan you'd expect are the bonus.Probes, covers, hoods andpouches are all available to en-hance the application potential andensure that Leader instruments setthe pace for others to follow.

Generators Attenuators System Analyser Audio Tester Distortion Meter Equaliser Amp Wow and Flutter Meter Frequency Response Recorders Millivoltmeters Log Amplifier Speaker Analyser 171

th ndarELECT I( L) 1ITED

Oscilloscopes

4 to 50mHz Single, Dual and Quad trace Delayed sweep Wide bandwidth High sensitivity High accuracy Battery operated

General Test LCR Bridge Semiconductor

Curve Tracer Transistor

Testers Logic Probe

Power Supplies Laboratory bench type 5 models

500mA to 5A Overload Protected

Thandar Electronics Ltd,London Road, St. Ives,

Huntingdon,Cambridgeshire

PE17 4HJ England.Tel: (0480) 64646.

Telex: 32250.

221 for further details

ISIDE COLO/ ,'"1 CAMERA

Contents DECEMBER1982

Volume 2 No. 3

Projects6M TransverterTX10 Direct VideoR&EW TransceiverNI -CAD ChargerHigh Duality PPM

-A UK first 10- High quality Video 25- The CW Generator 41

- Sophisticated Design 53-A good mover 73

FeaturesCommentPiezo BuzzersData Brief: MSL9362RSCircuit BlocksRewtelInside TV CamerasAmateur Radio WorldZ8 AssemblerData Brief: MSL9363RSNotes from the PastData FileThe Last Word

- Leading questions- Sounds interesting

- RC Encoder- Ouadrature Oscillator

Software for the BBC micro- Vidicons to Videos

- Arthur Gee reports- More power to our TBDS

- RC Decoder- Electronic greenfingers

- Cmos logic explained- Buzby Burgers?

51621384448616479819096

ReviewsKyokuto FM - 2030Sony PCM FlHitachi 9500

- With our unique circuit analysis 32- Digital audio 56

- Second generation machine 70

NewsNew ProductsAudio BriefVideo NewsComputing NewsDX TVShort Wave NewsNews Background

- In time for Christmas- IBC report

- Auto focus camera-A few over the eight

- Who needs Channel 4?- Frank's log- Poel's page

6303678828688

InformationNext month's R&EWProject Packs and PCB ServiceR&EW Book ServiceAdvertisers' Index

- All is revealed 24- Makes life easy 63

- An expanding service 84- Finders keepers 96

Our appologies to Tim Radford, the author of last month's 'What's wrong with the Spectrum' articlewhose name was omitted from the credits.

CEMBER 1982 See page 35 for the latest R&EW reader offers.

Sinclair ZX Spectr16K or 48K RAM..full-size moving-key keyboard...colour and sound...high -resolutiongraphics...

From only

025!First, there was the world-beating

Sinclair ZX80. The first personal computerfor under £100.

Then, the ZX81. With up to 16K RAMavailable, and the ZX Printer. Giving morepower and more flexibility. Together,they've sold over 500,000 so far, to makeSinclair world leaders in personalcomputing. And the ZX81 remains theideal low-cost introduction to computing.

Now there's the ZX Spectrum! Withup to 48K of RAM. A full-size moving -keykeyboard. Vivid colour and sound. High -resolution graphics. And a low price that'sunrivalled.

Professional power -personal computer price!

The ZX Spectrum incorporates allthe proven features of the ZX81. But itsnew 16K BASIC ROM dramaticallyincreases your computing power.

You have access to a range of 8colours for foreground. background andborder, together with a sound generatorand high -resolution graphics.

You have the facility to supportseparate data files.

You have a choice of storage capa-cities (governed by the amount of RAM).16K of RAM (which you can uprate laterto 48K of RAM) or a massive 48K of RAM.

Yet the price of the Spectrum 16Kis an amazing £125! Even the popular48K version costs only £175!

You may decide to begin with the16K version. If so, you can still return it laterfor an upgrade. The cost? Around £60.

DEF FN FN

SIN

Ready to use today,easy to expand tomorrow

Your ZX Spectrum comes with a mainsadaptor and all the necessary leads toconnect to most cassette recordersand TVs (colour or black and white).

Employing Sinclair BASIC (now usedin over 500,000 computers worldwide)the ZX Spectrum comes complete withtwo manuals which together represent adetailed course in BASIC programming.Whether you're a beginner or a competentprogrammer, you'll find them both of im-mense help. Depending on your computerexperience, you'll quickly be movinginto the colourful world of ZX Spectrumprofessional -level computing.

There's no need to stop there. TheZX Printer -available now - is fullycompatible with the ZX Spectrum. Andlater this year there will be Microdrives formassive amounts of extra on-line storage,plus an RS232 /network interface board.

Key features of theSinclair ZX Spectrum Full colour- 8 colours each for

foreground, background and border,plus flashing and brightness -intensitycontrol.

Sound -BEEP command with variablepitch and duration

Massive RAM -16K or 48K.

Full-size moving -key keyboard - allkeys at normal typewriter pitch, withrepeat facility on each key.

High -resolution -256 dotshorizontally x 192 vertically, eachindividually addressable for true high -resolution graphics.

ASCII character set -with upper- andlower-case characters.

Teletext -compatible- user softwarecan generate 40 characters per lineor other settings

High speed LOAD & SAVE -16K in 100seconds via cassette, with VERIFY &MERGE for programs and separatedata files.

Sinclair 16K extended BASIC -incorporating unique 'one -touch'keyword entry, syntax check, andreport codes

'um

FORMAT

TAB

OUT

USR,

SCREEN I,

INVERSE

RS232 /networkinterface board

This interface, available later thisyear, will enable you to connect yourZX Spectrum to a whole host of printers,terminals and other computers.

The potential is enormous. And theastonishingly low price of only £20 ispossible only because the operatingsystems are already designed into theROM.

ZX Spectrum

Available onlyby mail orderand only from

Sinclair Research Ltd,Stanhope Road. Camberley.Surrey. GUIS 3PSTel: Camberley (0276) 685311

The ZX Printer-available now

Designed exclusively for use with theSinclair ZX range of computers, theprinter offers ZX Spectrum owners the fullASCII character set -including lower-casecharacters and high -resolution graphics.

A special feature is COPY whichprints out exactly what is on the whole TVscreen without the need for furtherinstructions. Printing speed is 50 charac-ters per second, with 32 charactersper line and 9 lines per vertical inch.

The ZX Printer connects to the rear ofyour ZX Spectrum. A roll of paper (65ftlong and 4in wide) is supplied, along withfull instructions. Further supplies of paperare available in packs of five rolls.

The ZX Microdrive-coming soon

The new Microdrives, designedespecially for the ZX Spectrum, are set tochange the face of personal computing.

Each Microdrive is capable of holdingup to 100K bytes using a single inter-changeable microfloppy.

The transfer rate is 16K bytes persecond, with average access time of 3.5seconds. And you'll be able to connect upto 8 ZX Microdrives to your ZX Spectrum.

All the BASIC commands required forthe Microdrives are included on theSpectrum.

A remarkable breakthrough at aremarkable price. The Microdrives areavailable later this year, for around £50.

How to order your ZX SpectrumBY PHONE -Access, Barclaycard or

Trustcard holders can call 01-200 0200 forpersonal attention 24 hours a day, everyday. BY FREEPOST -use the no -stampneeded coupon below. You can pay bycheque, postal order, Access,

Barclaycard or Trustcard.EITHER WAY- please allow up to 28

days for delivery. And there's a 14 -daymoney -back option, of course. We wantyou to be satisfied beyond doubt -and wehave no doubt that you will be.

Fro: Sinclair Research, FREEPOST, Camberley, Surrey, GUI5 3BR. OrdeT1Oty Item Code Item Price Total

Sinclair ZX Spectrum -16K RAM versionSinclair ZX Spectrum -48K RAM versionSinclair ZX PrinterPrinter paper (pack of 5 rolls)Postage and packing: orders under £100

orders over £100

£ £

100 125.00101 175.0027 59.9516 11.9528 2.9529 4.95

Total £Please tick if you require a VAT receipt *I enclose a cheque/postal order payable to Sinclair Research Ltd for £*Please charge to my Access/Barclaycard/Trustcard account no.*Please delete/completeas applicable

'SignaturePLEASE PRINTName: Mr/Mrs/Miss

'Address

I 1 I I

I I I 1

I I I I

1 I I I I 1 1

I I I I 1 1 I

1 1 !III!!1 1

1 1

1 I I

. 1 1 I 1

I I I I I I

REW812

iFREEPOST- no stamp needed. Prices apply to UK only. Export prices on application.

EAST LONDON HAM STORE

H. LEXTO N LIMITED 11 RANCIS AD LEYTON E.10TEL 0F1 558 0854

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These are high power 240V hnears using 4C x 150 or 4C x 250 or 4C x 350 EimacTubes NOT using the grounded Grid system .Fully protected, no thermal damage to PA finals possible.

£22.00

GASFET MASTHEAD PREAMPS

DRESSLER AMPLIFIERSD70 70cm 200wfm 400 PEPD200c 2mtr 125wfm 200w PEP0200 2mtr 300wfm 600w PEPD2005 2mtr 400wfrn 1KW PEP

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IC740 HF 100W1C720RHE 100W GiCIC730 HF 100WIC2KL LinearIC2KLPS P.S.0PS15 P.S.U.PS20 P.S.0AT500 A.T.0RX70 ReceiverPS15 P.S.0

FT -one gen. coverage TX/ FIXFT102 150W 10mtr.160mtrFT707 100W 5.10mtrFP707 20A P.S.U.FC707 A.T.V.FT107M 9 band 100WFP107 P.S.U.FT1017D 160.10mtrFT9020M 160.10mtr AM/FMSP901 SpeakerFC902 A.T.0FL2100Z 1.2KW PEP linearFC102 SpeakerFC102 A.T.0FV102 V.F.O.

11.211=11MBA electronic morse/RTTV readerMicrodot/morse/RTTV printer/VDU/Key Board all one peice

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ICOMC2E 2mtr fm portableC4E 70cm fm portableC25G 2mtr 25w fmC290 2mtr lOw fm/ssbC251 2mtr 10w fmkw/ssb/baseC451 70cm lOw fmkw/ssb/baseC490 70cm fm/ssb mobileCSP3 SpeakerCSM5 MicC24G 10w FM Mobile

£159.0099.00

£235.00£366.00£495.00£630.00f445.00E 29.00E 29.00£169.00

TRIOIKENWOOD£995.00TS930 General Coverage RX'TX

Accessories TS830 100W HF £650.00CLC/ 1/2/3 case f 4.25 TS530 100W HF £475.00CWM9 SP/Mic E 12.00 TS130 100W HF £495.00CBP2 6V pack E 29.50 TS130 25W 2mtr FM/SSB E390.00CBP3 9V pack £ 20.00 TS7850 40W 2mtr FM £300 00C8P4 empty pack £ 6.95 TS7800 25W 2mtr FM £245.60CBP5 12V pack E 39.50 TR2500 2mtr Portable £200.00CCP1 charging lead £ 3.75 TR7730 2mtr FM £245.00CDC1 12V car pack AT230 £110.00LC8 leather case E 18.98 SP230 E 34.00BC30 Base Charger E 45.00 DM801 GDO E 60.00

P500 Rore,,,, AM1SSB £190.00

YAESUFRV7700A 11&150FRV7700B 5060/11&150

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FT29OR with mods FM/SSB £245.00 FRV7700C 140.170 £ 65.00FT480R 2mtr mobile FM/SSB £365.00 FRV7700D 70-80/118.150 £ 72.00FT78OR 70cm 7.6swift Shift £400.00 FRT7700 Aerial Tuner E 37.00FT78OR 70cm 1.6 swift Shift E440.00 F RA7700 Active Anterna E 36.00FT208 2mtr portable FM £195.00 FF5 Filter E 9.95FT708 70cm portable FM £205.00 MM811 FT290 Car Mouni £ 22.00FT230 2mtr FM mobile £220.00 NC11C Charger £ 8.00F RG7700 receiver AM/FM/SSB £295.00 NC8 Base ChargerF RG7700 memory E 80.00 FT208/208 108 £ 44.00

DATONGD70 Morse TutorPC1 Gen. coy converter

£170.00 FL1 Agile filterFL2 Active filter

£650.00 ASP Auto clipper

WELTZSP200 1 8 160MMZ 20200 1KWSP300 1 8 500MMZ 20.200.1 KWSP400 130 500MMZ 5.20-150SP250 1 6 60MMZ 20-200.2KSP15 1.08.160MMZ 5.20.200CT150 150/400W Dummy LoadAC38 3.5.30MMZ A.T USP1OX 108 150MMZ 20-20n

59.00E 79.00£ 59.00E 43.00E 29.95£ 31.00£ 59.00£ 19.95

£ 56.35£137.00E 79.35£ 89.70£ 8280

D75 Manual clipperRFC Speach clipperAD270 Indoor active antAD370 Outdoor active antREA Wide band AMP

DURING DECEMBER OUR PREMISES WILL BEOPEN SUNDAY FOR DEMONSTRATIONS ONLY

MORSE KEYSMCIN, Keys Swedish crass key f 44.00Himound HK706 £ 11.00Himound MK706 £ 20.00Hrmound HK7022 £ 22.50Kenpro squeeze key 100electronic key £ 57.00

Power Supplies

f 56.35E 29.90£ 47.15£ 6440f 33.92

The Lextorrlamp Max 12amp £ 49.9520ampMax 22amp £ 79.95Fully protected against overvolts &over current S/C protected.

Trade enquiries invitedand own name can be provided

CEIZZEIECZEIMaaSCsinn,r, Receiver S X200N £249.00

MURSL HLADERS

Taico TelereaderOVVRTTY £250

DIAWARM940 Mic InfraredCN620A 1KW SWRCN1001 Auto A T.V.CN2002 2KW Auto A.T.VCN518 2.5KW A.T.V.AF406 Active FilterAF606 P.L.L. Active FilterDK210 Electronic Keyer

SONYICF2001 receiverMur moral, rn041111.,MML 144 30 1 3w driveMML 144;100 L.S. 1.3w driveMML 144/100 SlOWdriveMMC 435/600 ATV converterMM2001 RTTY receiverMM4000 RTTY trancerverNiM1000K8 key board v transceiverMMT28;144MMD050 frequency counterA

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Kenpro KR 250Hirshmann HR 250Kenpro KR400RCKenpro elevationrotatorCDE Ham IV

E 44.95f 50.00

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TONNA144 4ELE £12.00 432/440 21 ELE E19.00144 9ELE E16.00 432/435 21 ELE A.T.V £27.00144 9ELE crossed 30.0 144/435 9 19ELE £31.00144 9ELE portable 30.0144 19ELEX E30.00144 16ELE £33.00 1296 23ELE £27.00144 13ELE portable £29.00 Phasing Harnes430440 19ELE crossed telescopic masts435 19ELE £19.00

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T8 NF£181.70VR3 band vertical E 46.00C52M colinear E 47.725Y2M 5ELEYAGI E 12.008Y2M 8ELEYAGI E 15.5010Y2M10ELEYAGI f 33.00PBM1010EPARABEAM £39.50PBM1414EPARABEAM £48.00

5XY2M £24.70BXY2M £31.00

E10XY2M 40.8004/2M £25.8006/2M

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ALL ACCESSORIES AVAILABLE - PLUGS SKTS CO -AX 2MTR COLINEAR £31.50, 70CM COLINEAR £31.50

PRICES INCLUDE VAT AT THE PRESENT RATE OF 15%OPEN MON FRIDAY 9 00- 5 30 SATURDAY 10 00 3 00. INSTANT HP FACILITY AVAILABLE

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4 RADIO & ELECTRONICS WORLD

Editorial Offices117a High Street, Brentwood,Essex CM14 4SG

Editorial (0277) 213819Managing EditorWilliam Poel

EditorGary Evans

Assistant EditorPaul Coster

Computing EditorJonathan C Burchell

Technical Consultants:ProjectsKeith CollinsJake Oliver

CommunicationsGraham LeightonRoger Ray

Editorial SecretariesKim MitchellJanet Capon

Production (0277) 213819Production EditorJack Burrows

Art/Production ManagerPatrick Haylock

Art EditorSally Bennett

LayoutHelen WhiteMartin Sheehan

Advertising (0277) 213819Advertisement ManagerJohn White

Subscription 01-868 4854Subscription ManagerOwen Rundle45 Yeading Avenue, Rayners Lane,Harrow, Middx HA2 9RL

Subscription RateUK £13.00 p.a.0/Seas £13.50 p.a.PrintersLSG Printers, LincolnPhotosetting byDelafield Reprographic Service

Distributors 01-274 8611SM Distribution Ltd

Overseas AgentsHolland Electronics 071-144988Postbus 377. 2300 A J LEIDEN

U.S. PROJECT PACK AGENTSBox 411, Greenville, NewHampshire,NH030408, U.S.A.

Back Issues: E1 each inclusive of postage fromSubscription Dept, or send reply paid card withcheque or PO.

Broadercasting Limited 1982. All reasonableprecautions are taken by R&EW to ensure thatthe information given to our readers is reliable.However we cannot guarantee it and we cannotaccept legal responsibility for it . Information andprices are correct at time of press.

Reproduction of contents is possible withpermission from the Editor, however shortabstracts or references are allowable providingthe source is given.

Publishers Broadercasting Limited

CommentNot a moment too soonThe interim report of the Independent Review of the Radio Spectrum(30-900MHz) was issued on September 23rd 1982. This must be one ofspeediest and most efficient pieces of work by any such body, and weare full of admiration for the way in which it was conducted soexpeditiously.

The conclusions are not too surprising, being a recognition of the in-creasing pressure on the space available by both broadcast and com-mercial mobile radio, and the need to terminate 405 line VHF televisionASAP. The word 'revised' occurs with alarming frequency, and it mustbe anticipated that makers of crystals and crystal filters will be rubbingtheir hands with glee before too long, if some of the more far reachingrecommendations are followed through.

There was no mention of our request for NBFM broadcasting facilities,and we shall be taking this point up with the Chairman, Dr Merriman(whose letters of qualification include the rather apt 'CB, OBE, FEng.'),since the concern of PW and the RSGB regarding the question of 6 metresis given quite an airing.

Surprise, surpriseWell, section 9.13 says the most intriguing bit: 'There is one bid we wouldcommend to the attention of the Home Office: the radio amateurs' re-quest for an allocation in the 50-54MHz range, a frequency which in useby amateurs in the Americas (we're surprised they resisted calling themthe "Colonies"....). We believe that radio amateurs play a part in increas-ing the understanding of radio and are worthy of encouragement. Wetherefore recommend that, if the detailed planning of Band 1 can be soarranged, radio amateurs be given an appropriate allocation in the50-54MHz band."

The rest of the report contains the usual stuff about being basicallyin favour of Good Things, and generally not in favour of Bad Things -

and you'll have to pay £3.80 to HMSO if that bothers you.The report pointedly fails to contain any reference to CB or cordless

telephones, which begs the question just where did these gentlemencast for their 'inputs'? It is well known that the mobile radio manufac-turers' and users' groups have a substantial lobby facility, along with thebroadcasters. Let's hope that the further deliberations of the committeewill not miss this rather important aspect at the second pass.

PS:Ahem, guess who brings you the first 6m transverter?

Feel the QualityIn common with other magazines in our field, increasing costs incurredin the production of R&EW have meant that we have been forced to in-crease our cover price to 85p with this issue. On a purely cost pereditorial page, and taking into account this increase in price, R&EWdoes, however, offer the best value for money amongst the electronicmagazines ranked along your newsagents shelves every month.

Our generous allowance of editorial pages means that we are able tocover all aspects of electronic endeavour from communications(represented in this issue by Graham Leighton's 6m Transverter) throughgeneral electronics, audio, video test gear to computing. Thus onemagazine, R&EW of course, gives you in one package, the samecoverage given by perhaps five or six more, vertically structured,magazines. These would set you back about a fiver - R&EW at 85p doesmake exceedingly good sense.

DECEMBER 1982 5

6 inputs...6 colours...words tooYou'll never need overprinted orspecial chartpaper again. Disposable six pen dottinghead records in six differentcolours on 4" (100 mm) chart... prints time, day number,chart speed, scales and otherdata in plain language.

Up to three different lin

earising signal conditioners(each assignable to any of thesix inputs) for all known T/C'sRTD's, d/p cells and othernon-linear signals.

Printing of two alarm set points appears as regularly -spaced pairs of colour -keyed dots.

Southdownview Road Tel: WorthingWorthing, Sussex. (0903) 205 2 2 2

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NEW PRODUCTSI.

Space Savers From HitachiTo herald the launch of a newlystyled colour TV range, Hitachi arereleasing the first model of the newseries, the 20" CPT 2071.

Instead of the conventional layoutof controls and speakers alongsidethe picture tube, the speakers on thisnew model, and others in the range,are positioned on the sides of thecabinet. All the operating controlsare grouped neatly under the TVscreen, for ease of operation, whichresults in the cabinet being squarein shape and taking up far lessspace.

The CPT 2071 has been designedto offer a wide range of facilities.It is equipped with a multi -functioninfra red remote keypad; controllingchannel selection, brightness,colour, volume, on/off and speakermuting. In addition, there is a

button which will cancel the remotecontrol adjustment of volume,brightness and colour and restorethe settings to those originally set onthe receiver.

In order to facilitate daytimeviewing in bright light, the newreceiver has a tinted glass filter -panel, across the face of the screen,which gives improved pictureclarity.

An extensive range of input andoutput sockets are provided with theCPT 2071, including headphonesocket, VTR connection socket,external speaker terminal, audioline-out terminal (enablingconnection to be made to hi fiequipment), and a DIN audio

recording socket for recordingtelevision sound.

The CPT 2071 will sell for around£380.

Low Power DC FanA new 3" DC axial fan, withextremely low power consumption,has just been introduced by PapstMotors. Known as the 81I2G, itconsumes only 2.6 watts - about fivetimes less than an AC fan of similarperformance. The 8112G is one ofa complete range of DC fans,:urrently being introduced by Papst.They employ sleeve bearings, ratherthan the more traditional ballbearings, which are of a sintered selflubricating design and combine longlife and low manufacturing cost.

A significant feature of the 8112Gis that spurious electromagnetic

Combined A & D PlottersFor the very first time, you canobtain digital and analoguefunctions combined in a singlerecorder. Known as the RY Series,these unique recorders are marketedby Rikadenki Mitsui Electronics(UK) Limited and weredemonstrated for the first time inthe UK at Lab 82. They can be seenagain at Testmex, WembleyConference Centre, October 26 - 28;where, to highlight their advantages,units will be linked to a NECPersonal Computer speciallyprogrammed for demonstration.

Made in A3 and A4 sizes, the RYSeries units are high speed plotters,with rates of up to 1,200mm/s inanalogue mode and 400mm/s indigital mode. Both sizes areavailable as single or multi -rangerecorders. There are 19 simplealpha -character commands to inputa wide selection of functions. Theseinclude 'T' to select plotting speedand 'C' to draw a circle and arc ofa circle. Other features include:80 -byte buffer memory, ASCIIcharacter format and a standardCentronics printer interface.

Rikadenki Mitsui Electronics (U.K.)Ltd.,Oakcroft Road, Chessington,SURREY, KT9 ISA.


I/ 401" 40101" 41/1" 40101" 401" I/ 4d1P 4OPP 4111P 401,'

'1 GAREX (G3zv1)

radiation is extremely low, which isparticularly important when the fanis employed in medical equipment,disc drives, display units andinstrumentation systems.

The 8112G will move up to 60cubic metres of free air per hour,when supplied by 12V DC. Thesupply voltage can be variedbetween 8 and 16V with resultantproportional variations in airflow.The maximum noise generated bythe fan varies from 26dB(A), withan 8V supply, to only 50dB(A)operating at its maximum speedfrom 16V.

The drive is provided by a

compact brushless DC motormanufactured by Papst. The steel

41 11 41 41 41 41 41 ID 11 IP

fan blades are directly welded to theexternal rotor and dynamicallybalanced to minimisevibration/noise and ensuremaximum life. The 8112G is ratedfor use at temperatures up to 65°without fear of compromisingperformance, with a life expectancyin excess of 20,000 hours (at thistemperature). Accessories availablefor use with the fan include metalor plastic finger guards complyingwith BS3456.

Papst Motors Ltd.,Parnell Court,East Port way,Andover,HANTS, SPIO 3LX.

11 41 11 11 41 41 11 41 41 41

i I /

Cabled For DataAlpha Wire Limited has announceda new, comprehensive range of datatransmission cables designed to meetthe needs of the computer industry.The large selection is intended toassist design engineers; with suchdiverse applications ascommunications interface, dataentry and display, local networkcabling, computer peripheralconnections and original equipmentdesign.

Alpha offers six basic cables: co-axial, twin -axial, Alpha -Byte low -loss, individually screened multi -pair, overall screened multi -pair andIEEE 488 interface bus cables andassemblies. Large stocks of thecomplete range are kept, assuringprompt delivery whenever needed.

Alpha -Byte is a newly developedset of cables with cellularpolypropylene insulation. Theunique cellular construction enablescable pairs to exhibit a lowerdielectric constant, resulting inreduced signal loss, lower distortionand increased transmission speeds;plus substantially reduced cableweight.

The new Lo-Tox (FEP Teflon)co -axial cables are ideally suited forlow -loss signal transmission in harsh

1

environments.A broad selection of individually

screened and overall screened multi -pair data cables are also offered aspart of the complete Alpha range.Individually screened multi -paircables are designed for computerand computer peripheral equipmentconnections, where high levels ofnoise interference are anticipated.Overall screened multi -pair cablesare designed for heavy duty controlas well as for data transmissionpurposes. Insulated withpolyethylene, polypropylene orPVC, both types of cable are idealfor outdoor installation as well asfor in-house networks. In addition,many optional armouring materialsare available for abrasion andmechanical protection, whererequired.

More information regardingAplha's data transmission cables,can be found in the new DC -1 datacatalogue. This is available from:Alpha Wire Limited,Alpha House,Central Way,North Feltham Trading Estate,Feltham,MIDDLESEX.

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SX200-N s

THE SUPREME kSCANNER

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CRYSTALS FOR NR -56, SR -9, SR -11, HF-12, TM -56B All 2mchannels from0(145.00) to 331145.8251. Also 144.80, 144.825,144.85 Ray net at £2.46 (+20p post per order). Over 40 popular marinechannels at £2.85 1+20p post).RESISTOR KITS a top -selling line for many years. E12 series, 5% carbonfilm, 10$2 to 1 M, 61 values, general purpose rating %W or 1/2W (statewhich)Starter pack 5 each value (305 pieces) £ 3.10Standard pack 10 each value (610 pieces) 5.55Mixed pack, 5 each %W + %W (610 pieces) 5.55Giant pack, 25 each value (1525 pieces) £13.60

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HT TRANSFORMER multi -tap mains Ori . 5 secs: 35V 200mA, 115V150mA, 50y 500mA, 150V 300mA, 220V 300mA £5.50PYE RADIOTELEPHONE SPARES Is.a.e full list) Ex. equip., fullyguaranteed. Cambridge AM1010.7MHz I.F. £3.65 2nd mixer E3 455KHz block filter 12kKHz03.40 ditto 25KHz £3 455KHz AM IF £4.95 Audio bd. £1.95WESTMINSTER W15/W30 AM Rx RF 68-8EIMHz or 148.174MHzE6.95 10.7MHz IF (ioc. 121/2KHz Mal. filter) £8.25 2nd Osc E2.10455KHz IF £5.65 455KHz block filter 112AKHz) E7.35 Squelch£1.45 00206-40a lqu)ck-heat) RF tested £11.95 Aerial relays E1.50PYE SPARES ARE OUR SPECIALITYCOMPLETE UNITS ALSO AVAILABLEGAREX FM DETECTOR and squelch conversion for Pye R/T equipmentReady assembled, full instructions. Tailor-made, easy -fit design, replacesexisting squelch board, with minimum of modifications. For AMCambridge £6.30: for Vanguard AM2513 (Valve R X: £5.10: for Transis-tor Vanguard AM25T £6.95MAIN DISTRIBUTOR OF REVCO AERIALS & SPECIAL PRODUCTS

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DECEMBER 1982 7

-... T,I.M/1111111111=, wank 1 I 1NNak / Am. WAN/ Pt°, =I

I 8= I NOS 11 Mia ...-,,,,1INNIIM II IMMI ,,Z.Zio,"IIIIP.=AolmIll I W SW ILAI 7' cMk IAM AEI Ia. AMINMIIIIP'.711111NW' -4 Jr ....11... J V NV V' ...111 1Mm a -am, ----mill111 me r- V lI r Am=EN 1 MIEMIIMF1 4111111811111111Mba..M11Ma MN 111 11.1 M- 11. la A `MIW Inn I I 11. NINM. -1 -1. -IL 7 - Mk 111.. ..A MN

FTESTEQUIPMENT CENTRES0,,E,N.s.,xpED,Asy0s NA DwIESEPIcLAY

RETAIL MAIL ORDER EXPORT INDUSTRIAL EDUCATIONAL

TRIO 20 MHZ DUAL TRACE SCOPES 2 YEAR GUARANTEE140mm Tube DC to 20MHZ 5mV sensitivity C112 Invert

CS1820 Delayed sweep 0 2 usec to 05 secSweep Modes CHI. CH2. DUAL and 600 SAYE EllList Price £53900 Inc VAT

Our Price £420.00 inc. VAT (UK c/p £4.00)CSI 566A NOR. AUTO VIDEO 0 Susec SweepModes CHI CH2. ALT. CHOP and ADDList Price C368 00 Inc VAT

Our Price £299.00 inc. VAT (UK c/p £4.00) Optional

,I 4, ot. . ...MT::: ne .11......::: -

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probes - see below

100 KHZ TO6 Band Trio RE Generatorvariable a,'D to IDOmV

Special Price

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01:8 /

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AM int 400 HZ modtooa../..r 95 Silt Eyainc. 'VAT(UK c/p £21

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LOW COST DIGITALMULTIMETERS3 digit LCD Hand Held 0MM sISW - Slide switch PEI - Push Button 1RS Rotzryl 'Models' with carry case'UK c p 65p all modelsKI/25C 13 Range 02A DC 1 megohm ISWI £26.50 K030C 26 Range IA AC DC 216 megohm IRSI £37.50II 055C 28 Range ICA AC,OC 200 medohmIRSI £41.50601 26 Range 2A AC/OC 20 megohm IPBI £36.50

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TP600 600 MHZ £43.13TP1000 with P'S 1 GHZ £73.00OPTIONSTE series carry case £6.84AC adaptors ITE Series1 £5.69 "litgliatiB series AC adaptors £5.69 - driii,.

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ANALOGUE MULTIMETERSGENERAL RANGELow cost reliable meters lAll supplied withballs. leads) IUK C, P 55p1BANANA 15 range pocket 2011/ Voltplus cant buzzer £20.64ET102 14 range 20 Volt Pocket E5.95ST5 11 range pocket 4K /Volt £6.50NH5611 22 range pocket 700. Volt £10.95TN3641TR 19 range plus Hle lest 200, Volt £2.95KRT5001 16 range 10 amp OC rangedouble 50K/Volt £ 1 6.50ST303TR 21 range plus He Test 2011/Volt £16.95AT1020 18 range Deluxe UV and Hle Tezler £17.50TMK500 23 range plus 120 DCPlus cont buzzer 3011/Volt £23.95168M 36 range large scale 10AACS DC 50K/ Volt £28.50360TR 23 range large scale 10AAC, DC Hie lest 50 meg ohm I NV

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, TE200 100KHZ 100NRI 6 bandAudio IUK c/p Ell 1 iMi. 1300MHZ harm] £49.95All models 220/2400 AC 15617 1001011 150MHZ 1450MHZ-hermlAUDIO 4 band Sine , so output LEADER £71.30TE22D Max distortion I' i 20HZ/200KH1 £59.95 FUNCTION tall sine/SOiTriangle/TTL etc ILA627 Max distortion 0 5.1`, 5020/11HZ 200KHZISABTRONICSI E90.00IL EADERI 101121101Z £136.25 TG100 IHZ-100KHZ ITHANDARI £90.85LAG120A 5 band 10HZ 1 MHZ TO102 0 2111-2MHZ ITHANDARI £166.75Sine so 0 05-0.8' °dist £146.00 PULSE11161 25 As LAGIMA but 002- TG105 5112-5MHZ Various outputsdist 'LEADER' £273'C0 'CHARM' £97.75A6203 10HZ t MHZ 5 band 0 I°, Sine SO 4001 Ultra -variable 0511Z 15MHZ 16SCI £1 1 3.85'TRIO' £129.95

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X ID £9.45XI X10 E10.500100 £16.95

DIRECT READ HV PROBE(UK C/P 65p) i.i 00 K Y 200 volt £18.40

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tube Trig to 20MHZ ICROTECHI £172.50 SCI I0* New model IOMHZ battery porta ieHM203/3 Dual 20MH2 Trig to 30MHZ 10mV 0 1 usec 2 trace5mV D5 micro secs 8 x 10cm display An facilities ITHANDARI £171.00IHAMEGI £253.00 'Options Carry case £6.84HM203/4. As above but 2mV Algebraic AC adaptor £5.69add IHAMEGI £276.00 Nicads £8.6313131 Dual trace 15MHZ trig to 35MHZ SAFGAN - UK made dual trace5mV 0 5 micro sec 130mm tube plus Satgan all models 5mV sens 0.5 micro seccomponent tester £276.00 6 4 x 8cm displayHM204 New model with component tester 0T410 Dual 10MHZ £205.85Dual 20MHZ delayed sweep trig to 40MHZ DT415 Dual 15MHZ £ 17.355mV 01 micro sec 8 x 10cm display IHAMEGI £419.75 0T420 Dual 20MHZ £228.85

'Optional cue £21.851PF/44

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NEW PRODUCTS

Samples From The RangeThe new TM451 is a 4 1/2 digitLCD multimeter and the latestedition to the range of test gear fromThandar Electronics.

It is a bench/portable instrumentwith basic accuracy of 0.0307o andfull autoranging or manualoperation as standard. There are 21ranges, in five modes, plus diodecheck and measurement storage onthe display.

The meter incorporates a

continuity tester and over -rangewarning beeper, with differentaudible tones for ohm measurementand input over -range. Full input

overload protection is also provided.The TM451 is powered by a

standard PP3 battery giving goodoperational life (due to the CMOSLSI -based design), but can bedriven from the mains supplythrough an adaptor.

Supplied complete with probesand battery, the instrument is pricedat £171.35 including VAT.

For further details contact:Thandar Electronics Ltd.,London Road,St. Ives,Huntingdon,CAMBS PEI7 4HJ.

205.f

Int

Pont

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Hand -Held CapacitanceMeterThe Metertech Model MT 301 is alow-cost hand-held digitalcapacitance meter. Batteryoperated, with a bold 0.5" 3 1/2

digit liquid crystal display, it permitsa wide measurement range from 0.1pF to 2000 uF across 8 ranges. Push-button controls allow fast and easyoperation, whilst small size, robustcontruction and long battery lifemake the MT 301 truly portable. Itis supplied complete with battery,alligator test clips, spare fuse and

instruction manual for £69. Adeluxe protective case is available asan optional extra at £6.

For further details contact:Centemp Instrument Co.,62, Curtis Road,Hounslow,MIDDLESEX. Portable HI -FlFor the first time ever, Technics hasmade hi-fi portable with theintroduction of its new system, theSA-CO5L . Retailing at under£245.00, the SA-CO5L combinesTechnics renowned sound qualitywith true light -weight portability.Finished in silver, the system weighsless than 9kg and comprises acentral unit, with built-in graphicequaliser, an FM/AM tuner and acassette deck with Dolby B noisereduction. Soft touch controls, aswell as one -button recording anddirect mode switching, indicate astrong emphasis on simple designand ease of operation.

Compact dimensions make theSA-CO5L easily portable withmatched speakers adjoining eachside of the console unit. For homelistening, they can be detached andused with wired connections for awider stereo image. There is a

power -pack for AC mains operationand an additional DC battery packfor music on the move.


Specifications AMPLIFIER:continuous power (both channels,1kHz into 4R at 5% THD) -2x15W(AC) and 2x2OW(15VDC);input sensitivity and impedance -phono 2.5mV/47k, aux150mV/22k, mic 1.5mV/10k;frequency response - phono RIAAstandard curve ± 1dB, aux/mic-3dB(20Hz-20kHz). TUNER(FM):sensitivity - 1.8uV/75R;THD(mono) - 0.2%; S/Nratio(mono) - 75dB(IHF); frequencyresponse - 20Hz-15kHz, +0.5 and-1.5dB; selectivity - 60dB; stereoseparation(IkHz) -40dB. TUNER(AM): sensitivity - 30uV; selectivity- 27dB. CASSETTE DECK: wow

and flutter - 0.05% (WRMS)±0.14% (DIN); frequency response- metal tape 20-17000Hz, Cr02 tape20-16000Hz, normal tape20-15000Hz; S/N ratio - Dolby NRin, 65dB (above 5kHz),Dolby NR out, 55dB (signal in =max record level). SPEAKERS:input power - 60W (music), 30W(DIN); impedance - 4R; output level- 88dB B/W (lm); frequencyrange-68-50000Hz (-16dB);crossover frequency - 8kHz.

National Panasonic (UK) Ltd.,300-318 Bath Road,Slough,BERKS SLI 6JB.

PCB Layout GridsUniversal Grids is the name of abrand new product that has beenperfected to meet all designersneeds. It is an extremely strong,versatile and stable base material,manufactured from 75 micron(0.003") doublematt polyester film,printed with a grid of Imperial orMetric 'fade-out' blue rulings.

Working to produce PCBpatterns directly on the filmeliminates any angular error andsaves processing time. Accuracy ismaintained even when working ona light box, or under a camera!

Technical pens, markers, rollingwriters, dry transfer, all perform

equally well on Universal Grids,giving great versatility as well asincreased economy and accuracythrough savings in valuable time andmaterials.

Universal Grids are available infour sizes - A1,A2,A3 and A4 - andin Imperial, Metric or plain. Pricesfor Imperial/Metric grids are: Al£3.91 per sheet; A2 £2.04 per sheet;A3 £5.29 per pack of 5 sheets; andA4 £4.42 per pack of 8 sheets.Universal Grids Ltd.,P.O. Box 3,Liskeard,CORNWALL,PLI4 6YZ.

CAMBRIDGE LEARNINGSELF -INSTRUCTION COURSES

*NEW!*DIGITAL

COMPUTERDESIGN

£8.50Our latest, up-to-datecourse on the designof digital computers,both from their indiv-idual logic elementsand from integratedcircuits.

Digital Computer Design is the best way foryou to understand how simple computers are.You are first shown the way in which simplelogic circuits operate and then, through aseries of exercises, arrive at a design for aworking machine.

GSC SUPERKIT £19.90The original Cambridge Learning Superkit, apractical digital electronics kit for begin-ners, now re -written for the popular GSCEXP300 breadboard. The kit comes completewith an instruction manual, components, andbreadboard to teach you all the basics ofdigital electronics.

DIGITAL COMPUTER LOGIC& ELECTRONICS £6.00The theory course to support the practicalSuperkit, this 4 -volume set covers basiccomputer logic; logical circuit elements; thedesign of circuits to carry out logicalfunctions: flipflops and registers. No priormathematical knowledge other than arithmeticis assumed.GUARANTEE No risk to you. If you are not completelysatisfied, your money will be refunded upon return ofthe item in good condition within 28 days of receipt.CAMBRIDGE LEARNING LIMITED, UNIT 150, RIVERMILL SITE.FREEPOST, ST IVES, CAMBS, PE17 LBR, ENGLAND.TELEPHONE: ST IVES (WO) 67446. VAT No 313026022All prices include worldwide postage (airmail is extra -please ask for prepayment invoice). Giro A/c No 2789159.Please allow 28 days for delivery in UK.

SUPERKIT(S) £19.90DIGITAL COMPUTER DESIGN(S) £8.50DIGITAL COMPUTER LOGIC AND ELECTRONICS 0 £6.00

I enclose a cheque/PO payable to Cambridge Learning Ltdfor £ ('delete where applicable)Please charge my:Access / American Express / Barclaycard / Diners ,tubEurocard / Visa / Mastercharge / Trustcard

Expiry Date Credit Card No

Signature

Telephone orders from card holders accepted on 01.80 67446Overseas customers (including Eire) should send a bank draftin sterling drawn on a London bank, or quote credit cardnumber.

Name

Address

Cambridge Learning Limited, Unit 150 Rivermill Site. FREEPOST,St Ives, Huntingdon, Cambs. PEI7 LBR. England. (Registeredin England No 1328762).

1

J

DECEMBER 1982 9

6 METRE BAND TRANSVERTERA transmit/receive converter, designed by Graham Leighton,

for frequencies in the range 50- 54MHz.

The 6 metre band has been used byamateurs in IARU regions 2 and 3 formany years. In most countries thefrequency range is 50 to 54MHz. TheRSGB/Home Office have announced thata limited number of experimental licenceswill be available in the UK. These willpermit the use of 50 to 52MHz outsidetelevision hours. So, we are presenting atransceiver converter, based on modulespreviously published in R&EW, which willform the basis of a 6m station using a144MHz tranceiver as the IF stage. Soonwe hope to bring you a follow-up articledescribing a single board 144MHz to 50 or28MHz transverter.

The heart of the system is a slightlymodified multiband up- converter (Ref. 1).During the design of this unit, the possiblityof using it as part of a transmit converterwas investigated. The hope was that itwould be useable for the 10, 6 and 4 metrebands. The wideband amplifier, describedin this issue, was designed with this inmind. In practice, however, the filteringneeded for the 4m version became toocomplex and was difficult to set up.

THE DESIGNThe block diagram (Fig. 1) shows how thevarious boards have been combined toproduce the transverter. The multiband up -converter uses a double -balanced diodemixer and a low pass filter which, sinceboth are bi- directional, makes it suitable

for use on transmit and receive. The lowpass filter, used in the converter, has a cut-off frequency of about 65MHz (see Fig. 2).This may be reduced to about 58MHz byadjusting the coils. In order to keep thespurious output level as low as possible, thedrive to the mixer (on transmit) must belimited to about -13dBm maximum. At thislevel the output from the mixer board isabout -20dBm. The spurious output is low(-60dB below the wanted signal) but underoverdrive conditions there is a spuriousoutput at approximately ± 6MHz which iscaused by the following mixing products:-

50-± (50 x 2) - 94 MHzso, don't get too enthusiastic with the drivepower.

The mixer board is followed by awideband amplifier which brings the levelup to about + 21dBm. This stage doesgenerate some harmonics. These, togetherwith any other unwanted out -of- bandsignals, are reduced by the bandpass filter.This filter is based on the design used inthe 6 metre preamp (Ref 2).

A power amplifier may be included at

INPUT ATTENUATOR/SWITCHING ASSEMBLY


PROJECT

94MHs

LPF

MULTIBAND UP -CONVERTER

5054MHz

144 148MH,

WIDEBANDAMPLIFIER

INPUT ATTENUATOR

N. A 2m INPUT/OUTPUT

50-54MHzFILTER POWER AMPLIFIER

>D>6m PRE -AMP- - - - -

J

0A Ern IN OUT

Figure 1: Block Diagram of 6M Transverter

this stage. The design we used works well,but is an experimental prototype. The gainof about 36dB, at 40 watts output, makesthe 'system gain' far too high. Thereforea 10dB attenuator, between the filter andthe power amplifier, is needed if the PA isnot to be overdriven.

The input switching is carried out by adouble pole relay which is housed in ascreened enclosure together with the loadresistors. Figure 3 shows the circuit of thisarrangement. The input attenuator relies onthe coupling between the two parts of therelay to provide about 45dB of attenuation.

On receive, the signal is routed to themixer board via a preamplifier (the designfor the preamp was published in SeptemberR&EW, Ref 2). A noise figure of 2.0dBwas measured on the prototype of thisamplifier, so the overall sensitivity shouldbe quite adequate.

RL2, which switches the 50MHz side ofthe mixer board, is also used to switch thesupply between the transmit and receiveamplifiers.

3

-20

-40

60MHz Low Pats FilterFilter Ro. fte

F10.:1P0AF V Loss 10E11IM1.12)

1.S.

S 32 0 ES(1042,

E

Figure 2: 60MHz low pass filter response

CONSTRUCTIONThe pre -amplifier and transmit amplifier

(Ref. 3) can now be built andtested. The mixer board (multiband up -converter) is built according to the article,except that the 60MHz filter is used insteadof the 75MHz version. Figure 4 shows thecircuit of the 50MHz bandpass filter whichis based on the one used in the pre -amp.

This can be conveniently built on a pre -amp PCB if desired.

The input attenuator and switchingnetwork, (Shown in the photograph),requires an input drive level of about 1watt. If a higher drive power is to be usedthen a more elaborate system may berequired.

As can be seen from the photographs,all the boards are mounted on an earthplane. This method is the most convenientfor this type of modular design. Each boardis fitted with tapped pillars which are thensoldered to a piece of copper laminateboard. Connect up all the individualboards, using screened cable for all RF

Figure 4: 50MHz fitter circuit

120R

TIP31

FERRITE BEAD

BC237

NOTETHE BC237 SHOULD SE THERMALLYCONNECTED TO THE ME ATSINS

13 Sv

BIAS

OUTPUT

Figure 3: Input switching circuit

DECEMBER 1982

Figure 5: Power transistor bias circuit

It

6 METRE BAND TRANSVERTER

connections. Once this has been done thelow power transverter should be ready foruse. The only part which may need furtheradjustment is the bandpass filter. In theabsence of other test gear the filter may beadjusted for maximum power output.

Make sure that neither a high RF powerlevel nor a DC voltage is applied to themixer, or irrepairable damage may result!

POWER AMPLIFIERThe three stage 40 watt amplifier has beenincluded in this article to give you a startingpoint. As already mentioned, a refinedversion will appear in a later issue ofR&EW.

In the power amplifier, each stage isoperated in class AB, the bias beingcontrolled by an individual active network.This bias network (Fig. 5) provides a stablelow impedance output which is fed to thebase of the RF power transistor. A BC237,when thermally connected to the heatsinkcompensates for any temperature rise. TheRF matching has been kept as simple aspossible whilst allowing a wide in theprototype, low VHF band transistors wereused. HF SSB parts should also be suitable -some experimentation may be necessary.Make certain that you follow the usualassembly precautions when fitting the RFpower transistors (see Ref. 4). Ensureadequate heatsinking - the photo shows theheatsink that we used - our one had to becooled using a fan.

When setting the bias, do so one stageat a time. In each case, set the variableresistor to the end of its travel (connectedto the TIP31 emitter). Adjust the biascurrent to the following levels: 1st stage25mA; 2nd stage 75mA; 3rd stage 150mA

Low power transverter outputspectrum

or as requried by the devices actually used.When tuning the amplifier, increase the

drive level slowly whilst tuning each stage.Monitoring the current drawn by each stageis helpful during the tuning process, as is

50MHz bandpass filter response

checking for oscillations by listening on anearby receiver.

A low pass filter should follow theamplifier to reduce the level of harmonicoutput.

O

R212R

R3120R

CI L1

INPUT

C2

O

L211

II

BIAS 1

RIZ7R

C3,0.0,

L

C8100n

C9C7 22u1000P

()SUPPLY 1

C5

01

L5

OV

R512R

AS120R

0BIAS 2

C101000ri

L6

C14100n

0 SUPPLY 2

C15C13 22u1000p

L7

119

R427R

R812R

C181001

L11

CI71000p

0 SUPPLY 3

C1922u

OV OV

R9120R

LIO

/C12o

II

BIAS 3

R727R

1 C16.000

L17

L13

C20

OUTPUT

0 OV

Figure 6: Power amplifier circuit


PROJECTINPUT

Supply 3JC18

L1

INS=11

0C20

RS

0C21

SUPPLY 2

C14

1111111.

16

R7

1011111

11

0C11

SUPPLY I

E.1) C12

Component Overlay - Actual Size.

PCB Foil Patterns shown at 70% of actual size.

CS

13

MEE

TT

eCS

R2

L4R3

C6

Cl

C2

COMPONENTS LIST (low powertransverter)Mixer Board - Multiband Up -converter fitted with 60MHz LPFand 94MHz oscillator.6 Metre preamp boardWideband amplifier boardBandpass Filter - as modified pre -amp board shown in circuitdiagram.

MiscellaneousScreening box, 3 off OMI relays,BNC sockets, Load resistors,LM317 regulator etc.

References1) Multiband Up -Converter R&EWAugust 1982.2) 10/6/4M Pre -amp R&EWSeptember 1982.3) Wideband Amplifier R&EWDecember 1982.4) 2M Power Amplifier Ray, R.R&EW June 1982.5) TRW RF Semiconductors DataBook (European Edition).

Your Reactions Circle No.Excellent - will make one 45Interesting - might make one 46

Seen Better 47

Comments 48

DECEMBER 1982 13

WIDEBAND AMP

The wideband amplifier shown with the othermodules that combine to make the 6m Transverter

THE DESIGN described here was intendedto form part of a transmit system for 14to 70MHz based around a double balanceddiode mixer (eg MCL SBL-1). The outputlevel from such mixers of about -20dBm (ifspurious products are to be avoided)necessitates a high gain linear amplifierblock - such as that described here. The 1dBcompression point after the amplifier isabout + 24dBm (250mW). Originally,asingle transistor output stage was used, andthis gave + I2dBm output at the 1dBcompression point.

Both stages are run in class A, this beingthe best mode to achieve good linearity.

Response of wideband amplifier0-100MHz range (vertical 2dIldiv)

over

A wideband amplifier for 14-70MHz

Graham Leighton

Active bias has been used to provide goodd.c. stability. The feedback was tailored forthe most level response over the requiredrange.

CONSTRUCTIONAs usual with circuits of this type, a doublesided pcb has been used, with the top sideof the board as an earth plane. Allcomponents requiring an earth connectionare soldered directly to the top of the pcb.Apart from the winding of the transformersthe construction is straightforward andshould present no problems.

Response of the wideband amplifier over0-200MHz range (vertical 10dB/div)

Transformer Winding:T1: Wind 2 turns through a core to formthe primary, and three turns for thesecondary.T2: Wind two turns on the core. Fold backand twist together about 6mm of wire toform the centre tap, then wind a furthertwo turns. The result is a centre tapped four

PARTS LIST

ResistorsR1,7R2,8R3R4,11,12R5,13,14R6R9R10R15,16

CapacitorsC1,3,5,6,10,11,12,13,14,16C2,7,15C4C8,9

SemiconductorsQ1,2Q3,4,5D1,2

820R10k6k812OR27OR39R6R83k31OR

10n ceramic1u Tent33p Ceramic56p Ceramic

BC307ZTX3271N4148

Miscellaneous3 off fair rite core Z8-430024021 off PCB enammelled copper wire


PROJECT

O

Lo GRL 09

0 I go froogillit C0.1k 1 co

INPUT

.10V SUPPLY

OV

R1820R

DI

R210k

t R639R

C3iOn

OV

01

R36k8

C2to

C1

R7 R9820R 6R8

D2

R80V 5105

OV

C6 I .1 C71a,T Tip

OV

R4 R5 C5

120R 270R 10n

=.= C433p

01 & 02 = BC30703,04 & 05 = ZTX327DI & D2= 1N4148

02

R103k3

2

R11 R13

120R 270Rca56p

OVlOn

O

R15lOR

C1010n

OV

R16 C11IOR 1°" C14

10n

06

R12 R14 4..... i12OR 2111/R C13

iOn

Circuit diagram of the amplifier

C1511u

T3

CIRCUIT DESCRIPTIONI. C16 The input to Q3 is approximately matched to

ion 50R by the transformer T1. R4, R5 and C4form a feedback network which reduces thegain with increasing frequency. T2 provides therequired matching and phase split between thetwo stages. A push-pull output stage was usedto give a reasonable output level with goodlinearity, using relatively inexpensive devices.Once again, an RC feedback network has beenused to set the gain. Additional LF roll -off isachieved by the capacitors across RI5 and R16,

OUTPUT and the reduction in efficiency of thetransformers. T3 re -combines the output fromQ's 4&5, and matches their output to 50R.

Class A bias has been used to minimisedistortion. The power consumption is notsignificant at the low output levels involved.An active bias network such as that used here,gives very good dc stability. The diodes DI,D2are included to give some degree of temperaturecompensation.... RI5 and RI6 reduce the effectof any differences between Q4, Q5 and theirassociated circuitry.

OV

OV

aro 01 010 01 :41 r0

0-0211,417:-.0O

PCB Foil Pattern - Track Side.

O

0.0O .1

L

0°00 0 go o

o r°Ooo o o

oooo

00 0o 000 oo

o go 8 8 a :o o

0 o o00 00GRL 09

PCB Foil Pattern - Top.

C2

DI

C16

.VE -6=110V cis C9

rri irlD2 ".

C13

WIDEBAND AMPLIFIER

Component Overlay.

C14

INPUT

C4

C5 R5T2

9.4F. c11.. 0 C8

C12 P13

73®

OUTPUT

turn secondary. Wind another four turns on the core to providethe primary winding.T3: In a similar manner to the winding of T2, wind T3 with a 6turn centre tapped primary and a two turn secondary.

Once the transformers have been soldered in place, the amplifiermay be tested.

TESTINGSince there is no alignment involved, the testing consists only ofchecking the operation of the amplifier. Connect a 10 volt currentlimited power supply and an RF power meter (which could simplybe a 50 ohm resistor and RF probe for a multimeter or 'scope).Using either a signal generator or a converter, check that the gainis about 40dB, and the output is reasonably constant over thefrequency range. The output power at the 1dB compression pointshould be about 250 mW. R & EW

Your ReactionsC,,c1. No C,rcie No

Excellent - will make one 21Interesting - might make one 22

CommentsSeen Better

2324

DECEMBER 1982 15

PIEZO-BUZZERSChris Parsons explains the operation,construction and application of theseuseful devices.

PIEZO-BUZZERS fall into a category of devices calledtransducers. These come in widely differing types, since the categoryencompasses anything which converts a physical quantity, such asheat or light, into an electrical one - and vice versa. Now usually,this conversion process will generate electrical signals which canbe processed - converted to digital form - and stored for analysisby computer. However, in the case of piezo-buzzers, the conversionis from electrical to mechanical: they operate by producingvibration (ie sonic waves) in response to an electrical input. In fact,AC and DC input voltages will cause the piezo- electric ceramicto distort (ie expand or contract), but only AC gives rise to therepetitive vibrations which characterise a sound wave - albeit ata frequency above that of the audible range for humans (>20kHz).These are the ultrasonic piezo transducers, familiar in burglaralarms, which require certain modifications to function at audiofrequencies. This is one of the topics we will discuss.

SUPPORTING VIBRATIONSThe natural resonant frequency of piezo-ceramics is much higherthan that of the upper limit for human audition. So, to obtain anaudible output, a metal plate has to be attached to the ceramicelement (Fig. 1). This produces a reduction in frequency tosomething around a few kilohertz; the resonant frequency beingproportional to the thickness, over the square- of -the -radius of the

element (assuming a consolidated plate and ceramic). The metalplate vibrates in a vertical direction - since it cannot follow theexpansion/contraction vibration you find with resonating ceramics- and it is this vertical motion which produces the sound waves.As the ceramic is stimulated into oscillation, near the resonantfrequency, it contorts and vibrates against the plate. This, in turn,moves up and down causing alternate bands of compression andrarefaction in the air (sound waves); which is why we can hear thebuzzer.

Piezo-electric buzzers can operate in three modes of vibration,dependent on the position of an integral support to hold the elementinside the case. These three modes, shown in Fig. 2, are: nodesupport, edge support and centre support. The first representsvibration in a free state (the vibration is not affected by the support)and the broken line in the diagram shows a circle of null vibrationcalled a node. Where this node is supported, suppression ofvibration is very small and a stable resonant frequency is obtained.At this frequency the sound pressure level is 40dB higher than atfrequencies which are more than 1 kHz either side (Fig. 3). Thediameter of the node, consistent with this type of vibration, istheoretically 0.55 times the diameter of the sound element.However, practical elements may vary from this ratio by as muchas 120/o.

The second mode of vibration results when the element issupported around its edge. Here, since the whole element is movingup and down, the support also vibrates causing the resonantfrequency to change. Fig. 4 shows the spread of resonances,throughout a range of frequencies, due to the interaction betweenthe support and the element. So, since there is not a single resonantpeak, with high output level, an external drive (source of frequency)is best used.

Figure 1: Position of metal plate on a piezo-ceramic

16

Figure 2: The three vibration modes for plate and ceramic element.

RADIO & ELECTRONICS WORLD

FEATURE

CO 9.'0

13 800-1O 70

t 60

V

rn

Distance ofSine Wave:

Measurement: 3C30 V p- p

CM

2

Frequency (kHz)4

Figure 3: The output rises dramatically at the resonant frequency(mode support, 30Vp-p input at 30cm).

The third mode, centre support, is similar to the second in theway it suppresses a certain amount of vibration and requires anexternal signal source. However, the resonator is not easy to designand the device is mainly used for alarm systems where a customiseddesign is needed.

THE CASE FOR LOUDNESSThe shape of the case, in which the piezo-ceramic and metal plateare supported, plays a significant role in the overall level of soundavailable from the buzzer. If the piezo- electric element is stimulatedin free air (ie without a case) the output will be fairly low. Thisis due to several factors, but lack of directivity and power are twoof the main ones. So, to combat this a resonating case is used tohouse the piezo-ceramic and metal -plate.

The case is designed to resonate at a specific frequency, whichcan be found from fo = 55 s/1W (the letters refer to dimensionsshown in Fig. 5). This frequency is chosen to match the resonantpoint of the ceramic and plate; which amplifies the sound pressurelevel at resonance.

If the case design is constrained by other considerations - forinstance, limited space inside a watch - it is possible to boost theoutput using a coil and switching transistor (Fig. 6). The techniqueis to create a high instantaneous voltage to drive the transducer.When Q1 is switched on or off by a square wave input (with riseor fall time t), a back EMF proportional to L/t is generated incoil LI. This can provide a peak -to -peak voltage several timesgreater than the line voltage and a comparable increase in soundoutput. Also, by inserting a capacitor between + V and the collectorof Q1, any surge currents will be absorbed at the expense of someloss of sharpness in the sound quality.

THE DRIVE TO OSCILLATEThere are two methods for driving these transducers; self -drive andexternal drive. The primary factor which determines the oscillationdriver is the type of support used. As mentioned earlier, there arethree ways of supporting the piezo-ceramic and metal plate - oneproduces a single resonant peak (node support) and is easy to setinto oscillation, and the other two have a range of resonances (edgeand centre support) so must be driven by an external source. Thesuitability of any buzzer for a particular application thereforedepends on the construction of the case and the way the elementis supported. With node support, self -drive oscillation is mostappropriate and the usual circuits (e.g. Colpitt or Hartleyoscillators) may be used. An alternative is shown in Fig. 7, wherea feedback electrode is used to simplify the oscillator circuit.However, this method relies solely on the resonant frequency ofthe sound plate, that is, only one frequency is available (the onlyway to alter the frequency is to change the size and shape of theplate).

PKM11-450

100

CO

V

-41 90

2S'' 80

13

30to

70

Input Voltage: Square Wave 3Vp-pMeasured Distance: 10 cm

2 3 4 5 6 7 8 9

Frequency (kHz)

Figure 4: Range of resonant frequencies with edge support (3Vp-p@ 10cm).

Figure 5: Important dimensions for the design of a resonating case.

Figure 6: Using a transistor and boosting coil to Increase the outputvoltage.

The other support -types (edge and centre) require external drivingcircuits and are commonly found in watches and calculators.However, there are a wide range of application circuits in whichthese piezo-transducers can be used. Some examples are shown inFigs 8, 9 and 10. The first circuit is a simple multivibrator withexternal drive transistor to boost the available peak voltage, asdescribed earlier. The second (Fig. 9) is designed to produce atelephone ringing tone, with centre frequency provided by IClc,d.Finally, Fig. 10 is configured to produce the sound made by acricket. All these circuits can be provided with protection against

DECEMBER 1982 17

PIEZO- BUZZERS

Figure 8: Multiyibrator circuit with boosting stage.Figure 7: A feedback electrode can be used in a simple oscillator.

IC1a

RV12M2

R1 C13k3 2n2

IC1b

RV22M2

IC1c

IC1e

RV32M2

NOTE: IC1 IS 4049IC2 IS 4011

R2 C23k3 22n

AANR3 C33k3 2n2

IC1f

IC2a

IC2b

IC2c

IC2d)3-^

BUZZER

Figure 9: Circuit to produce telephone ringing tone.

voltage overload, by placing two zenerdiodes (cathode to cathode) across theterminals of the buzzer.

Piezo-buzzers best suited for externaldrive do not have a single resonant peak,but two or more within a frequency bandof around 10kHz. The responsecharacteristic is shown in Fig. 11 (for abuzzer designed to produce most sound at2048Hz and 4096Hz) and it is clear thataround the resonant peaks, an increase of20Vp-p input will produce a 20dB increasein sound pressure level. This comparesfavourably with the efficiency of the nodesupport types, but here the external drivecircuits can add further power andfrequency variation. In fact, the number ofaudio circuits in which external drivetransducers can be used is quite large. It isjust a case of making any special mods andthen 'plugging in' and 'switching on'.

R&EW

L

Your ReactionsOrcle No Circle No.

Immediately Inteesting 1 Not Interested in this Topic 3Possible Application 2 Bad Feature/Space Waster 4

-a

100

90

80

70

Input voltage: Square wave 3Vp_pMeasured Distance: 10cm

2 3 4 5 6

Frequency (KHz)7 8

Figure 11: Response characteristics of an externaldrive buzzer(Murata PKM11-4A0).Figure 10: Circuit for sythesising the sound made by a cricket.


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300.000

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We still supply matching Crystal CalibratorsCC -11 and Absorption Wavemeters TC-101as previously advertised.

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further details

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We are pleased to announce that due to thedevaluation of the French Franc, the prices ofall our antennas have been reduced.

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Tel: (0235) 23080 (24 hours) PISA

BESTS LLER

A qualitydigital multimeter

for the priceof an analogue.

The Beckman 3' 2 digit T100 multimeter offers:

' numerous functions and ranges (200mV to 1000Vdc or750V ac: 200pA to 10A ac or dc: 200 (Ito 20M I I)

. good accuracy (0.5% on Vdc)

numerous extras (like dedicated diode test range. high or lowpower ohms, numerous accessories)

easy operation and excellent protection

Also available is the T110 model, with 0.25% accuracy andbuzzer for continuity testing, at £68.50 (inc. VAT, p&p).

BECKMANBeckman Instruments Ltd

Electronic Components UK Sales and Marketing OrganisationMylen House, 11 Wagon Lane, Sheldon, Birmingham 826 3DU

Tel: 021-742 7921 Telex: 336659

Please send me.

I T100 meters at £57 (inc. VAT, p&p)

)T110 meters at £68.50 (inc. VAT. p&p)I enclose a cheque or P.O.

(payable to Beckman Instruments Ltd) for £

Name:

Address

Please allow 14 days for delivery _J


DECEMBER 1982 19

R&EW PANEL SIGNSGiving that professional look tothe front panel of your latestcreation can be a bit of a problem.

Dry rub down lettering can beused for control markings andscales but unless used with skillthe results can be less thanflattering.

The R&EW label system solvesthe problem by providing a setof symbols and scales that areprinted on the reverse side of athin, clear plastic sheet.

Identify the word/symbol yourequire, cut around it, peel thebacking paper off and stick it inplace on your project.

The results are perfect everytime.

Three different sets of panelmarkings are available, blackwording, white wording anda set of scales.

001104 St at% Gain

The wording sets contain over1000 words covering 300 terms- the dial set contains one largehorizontal tuning scale,frequencies and 12 control panels.

Any one will cost you only £1.50,but buy two and we'll give youthe third one free thats just

£3.00for the complete set of R&EWPanel Markings.

All prices include VAT and postand packing.

1 Send your order to:R&EW PANEL SIGNS117A High StreetBrentwoodEssex CM14 4SG

OUTNOWAUTUMN '82 WR&E MORE PAGES

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R&EW Data Brief MSL9362RS

The MSL9362RS is an encoder chip, primarilydesigned for use in radio control systems. It iscontained in a 14 pin DIL package, incorporatingan oscillator. When running at the samefrequency as the oscillator (built into the decoderchip MSL9363RS-Data Brief 2) they produce avery effective method of coding signals.

The oscillator frequency determines the lengthof one frame of signals. In each frame there are4 signals and a sychronous period. These 4signals, defined as the period between the pulses,can be operated in two modes:

1) 4 proportional channels2) 2 proportional channels + 2 logical

channels (ON/OFF)The proportional signals are controlled by a

potentiometers and the logical commands byswitches, selecting high or low resistor values.

The sychronous period has to be long enoughfor separate frames to be identified by thedecoder.

Where many radio control channels are beingused, interference between channels can be easilyavoided by selecting different oscillatorfrequencies. With high oscillator frequencies,fast reaction times are obtainable - with a lossin sensitivity to the controls.

The oscillator frequency is fixed by the valuesof a resistor (Ro) and capacitor (Co), fed by thestable voltage source (Vref) and connected toOSC I and OSC2. Vref (3.8V) is obtained fromthe voltage regulator in the chip. This permitswide variations in power supply (6 to 13V) andis ideal for battery operation. Vref is also usedto supply the control potentiometers so that thechannel inputs remain stable.

Other controlling components include atrimmer, giving a voltage to Vcomp that sets theneutral position of the control potentiometers.Similarly the trimmer in the C,R and R' circuitry,that sets the pulse repeat time, is the sensitivitycontrol for the signals.

PARAMETER CONDITIONS :'IIN TV? MAX L'S II

Input Voltage VIN *1 0 - Vref V

Input Current In VCC=13V, VIN=0*I - -1 -3 IA

Output Voltage Vref*2

Vcc=7.,13V, Iref=SmA - 3.8 - V

Output Current Iref Vec=7'.13V, Vref=3.8V 5 - - mA

oical "0 "LOugtput

Voltage VOL Vcc= TA,13V, Io=l5mA*3

- 0.25 0.4

LogicalCurrent"0" /OL

*3Vcc=7- 13V, Vo=0.4V 15 - - mA

Output LeakageILO Vcc=13V, Vo=5V - - 10 11ACurrent

Supply Current la Vcc=9V. Vref=Open - 6.5 8.5 mA

Electrical Characteristics (Ta -10 +60C, TYP : Ta 25° C).1 : CH1 CH42 : Vref*3 : OUT

PARAMETER CONDITIONS RATINGS L'N I T

Supply Voltage Vcc Ta = 25°C. 15

Input Voltage Vin Ta = 25.C*1 10 V

Output Current/OUT Ta = 25'C*2 30 mA

'ref Ta = 25°C -30 mA

PowerDissipation PD Ta = 25°C 200 mW

StorageTemperature Tstg - -55 '1, +150 C

Absolute Maximum Ratings *1 :CH1 CH4 *2: OUT *3: V

Vref O1

0111_R

Constant

R'Current

Voltage

Regulator

02CH1

CH2 C33 --D-CH3 C)4

CH4 05

Vcomp 06

C 012

CH

oscl

Counter

011

OSC

OSC2 010

VCC GND

771.4 8

DigitalHono-Mulct

FrameGenerator

-to OUT

Block Diagram.

DECEMBER 1982 21

VCC(-1-9V)

O

RV1l IRV2 33u

777

33u

777 777 777

RV3

ref

CH1

CH2MSL9362

CH3

CC

OUT

OSC 2

CH4 OSC1

Vcomp

1

100Cri

APPLICATION EXAMPLE2 Channels Proportional + 2 Channels ON/OFF

C h.-A

R15k1

R' ---

R GND

A/V-12k

D

777

Ro

33k

Co470p

To Modulator

(Film Condenser)

B

OSC Freq.f(KHz)

FrameA (ms)

Pulse WidthB (us)

Pulse RepeatC (ms)

Synchronousperiod

D (ms)

80 16 200 <3 >4

60 20 250 <4 >4

53.3 24 300 <4 >4

OUTPUT WAVE FORM A:8 = 80:1


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After months of negotiation we have finally secured the computer user's dream. We have bought the complete manufacturer's production of thesesuperb British made R.G.B. Colour Monitors and can offer them to you at this unrepeatable price. This offer, available to readers of ' R & EW'

also includes a FREE isolating transforme,. So with a little of your time and our buying power - you can save pounds. For shippingpurposes the C.R.T. and scan coil assembly are separate from the chassis. The lugs of the C.R.T. allow it to be mounted in a standard 22" colour TVcabinet or a unit of your own design. The unit is assembled by plugging the wires from the chassis to the tube, soldering the input connector,power connector and isolating transformer. The monitor has been fully tested and adjusted prior to packing thus simplifying assembly. Acomprehensive instruction sheet will be supplied with each unit.

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4516-10OnsBBC RAM 3 10 295 2804161-200ns 4.80 4.60 1.106116-150ns 4.20 3.95 3.932716-5y-150ns 210 2 15 2.002716 TnpleRad 600 - -273245Ons 315 3.75 3.252532-450ns 395 375 3258080A 1 90 1 70 -8212 1 40 1 30 -25 -WAY 0 SOLDERCONNECTORS25P El 30 inch25S El 50 each

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Carriage should be added to prices at the following rates. Monitor E 0; Discs BSp; Rams 50p, Filing Boxes/ Lectures El. Desks E 10 Pleaseadd carnage as applicable andthen VAT at 15% to total end send Cbedue/P.Order payable to "Opus Supplies- to Dept. W.W., Opus Supplies. 10 Beckenham Grove. Shortlends, Kent BR2 OJU Telephoneorder Hotline: 01-464 5040 124 -hour service) or 01-404 1598. Access and Barclaycard accepted. If you are not completely satisfied return the goods within 14days and yourmoney will be refunded.

IORCLOUADTRADE ACCOUNTS OPERATED - GOVT AND EDUCATIONAL ORDERS WELCOMED


DECEMBER 1982 23

MINIMUM CHIP Z8 SYSTEM

Our full featured Z8 systempublished last February hasproved very popular. Anumber of readers haveasked for 'stripped down'design omitting featuressuch as the EPROMprogrammer and utilityroutines.

Next month JonathanBurchell presents just such adesign featuring the 28 - anEPROM and not a lot else.

NASCOM ANIMATION GRAPHICS BOARD

IF YOU LIKED JAWS YOU'LL

LOVE

NgIan Campbell's articles on PLL Frequency Synthesis andPower Mosfets proved very popular with our readers. Nextmonth he turns his attention to SAW Devices. These SurfaceAcoustic Wave filters feature small size, high stability whencompared to LC tuned circuits, optimum phase design andhigh reliability.

The theory behind SAW Devices, plus plenty of examplesshowing their practical applications will feature in nextmonths R&EW.

hl - T ICY

1.73* -R - PH E:S

The Animation Graphics Board provides colour graphics, stereo sound, CMOS battery backed up ram, real time clock, 8 channelA -D and a vectored interrupt counter timer chip all on a single board approx. 8" x 12" with Nas-bus edge connector. Althoughintended for the Nascom range of computers, there is no reason why the board could not be used with any Z80 system, or indeedwith a little externa logic the board could be mapped as memory for the 6800 family of microprocessors. The whole board ismapped as I/O ports and although containing 16K bites of dynamic screen memory does not encroach on the system memory map.The board is fully buffered and provides a de -coded I/O port signal for feeding back to the Nascom CPU board.

Take me to your NEWHIGHTNewsagents often run out of copies of R&EW simply because it is thebest value for money electronics magazine around.

To make sure you don't miss a single issue, why not fill out thecoupon and your newsagent wil reserve a copy of every month'smagazine ready for you to pick up at your leisure.

Fill out the coupon NOW and drop it in when you pick up yourmorning paper.

NEWSAGENT:Please reserve me a copy of theJANUARY 1983RADIO & ELECTRONICS WORLDand every succeeding issue untilfurther notice.Name:Address:

24RADIO & ELECTRONICS WORLD

DIRECT VIDEOINTERFACE

In this month's conversion, Paul Pittsoutlines the modifications for compositevideo from the Thorn TX10 receiver.

LARGE SCREEN MONITOR

YELLOWFROM BNC

TWO BRO.NS

VIDEOBLACK

W.GREY

W.GREEN 0

AUDIO IN 0BLUE

+11V

R2VIN 3k9

R1P.75R

R4

EARTH 3k9SV41

0.'"*. R22

R510k

R710k

C1 15u

10k0 INN 011N4148

D1

R947k

R810kR610k

14

C2I 15u

ICI

THE FIRST THING to recognise, whendesigning any TV interface, is there are twosignal paths to consider; audio and video.With the TX10 convertor, this is apparentfrom the circuit diagram (Fig. 1). Theupper portion processes the video signalsand the lower is for audio. Switchingbetween monitor and RX is via Q4 andFET1 (video), and Q6 (audio). On thetuner, this is achieved by pressing one ofthe extreme right hand buttons markedAV. In RX mode, the video output carriesoff -air pictures (1V peak -to- peak into 75R)and the audio carries off -air sound(standard level into lk) that adjusts to zero- this permits connection to some VHSmachines which require inputs of 20-30dBdown from the usual level. Depressing theAV switch, mutes the RX IF stage (via theAGC line) and causes FET1 to close the

LW.733CN0

7WWR10

5 1OR

IC4MW

R 3 BC183LB1 C55R6 l7 01 T 100n

video path from IC1 to the video outputstage. Transistor Q1 cuts out any signalpath from the vision detector (rememberthe IF is muted), which prevents Q2 seeingtwo inputs at once - it's either 'video in'or 'detector out'. Depending on theposition of SW1, the 1Vp-p video signalsees an input impedance of either 10k or75R. This is amplified by ICI, which hasa gain of 3, and then output to the drainof FET1 (described earlier). Control of thevideo level is provided by R3 (± 3dB).Switch SW2 is included in the circuit toallow for different sync pulse timing - thisis kept in the AV position.

SW1 is next to the BNC sockets on theprototype. in such a way as toloop through the BNC's (when not terminated)as well as terminating the input with RIwhen required. This is so that when sets are

R17 R1882R 410k W.RED

TX

I0 WHITE TO SWR20 C6 AND VOui BNC75R 1000hs VIDEO

/R19 R21OUT

680R 10k

0

0 W.BLUE

R2647k R27

47k

AUDIOOVEARTH

GREEN

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4k7

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1N41480/

05BC213LB

C810u

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R3115k

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t R3356k

R35

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SW2 TXALTERS VT

TIME CONSTANT

R3610OR

0 W.WHITE G W.YELLOIN

NOTE: A100n CAPACITOR (C10) IS PLACED BETWEEN PADS B AND D OF THE AUDIO AMPLIFIER IC.

MMR371k

0 GREY FROM BLACKPHONO (AUDIO OUT)

TX10EARTH

W.BLACKOV

Figure 1: Circuit diagram for the complete interface.

DFCFMBER 1982 25

LARGE SCREEN MONITOR0

connected in series, should one die, theremaining downstream sets still have apicture.

CONSTRUCTIONYou will have noticed the sockets on thepanel are isolated. Also the PC board earthis wired back to the TXIO chassis at thepoint shown, ie pin 10 of plug 4. Thereason this seemingly roundabout route isused is to prevent a shallow striationappearing on mid -grey scenes on some kits.I traced these two pulse currents from thesets' PSU, causing small voltages to be setup in the metallic chassis. Hence the actualpoint chosen for the earth contact isimportant. I hasten to add that DC- wisethere is negligible resistance betweenexposed metalwork or BNC/phone plugsand the 13 amp plug earth. So, make sureyou change the existing 2 -core mains leadfor a 3 -core. The green/yellow conductormust be taken to the set's metallic chassisat the point shown and in the manneroutlined - a 'self tapper' does not satisfysome ruling bodies.

I chose to remove the on/off switch andbutton assembly and solder the blue andbrown conductors to the points used byThorn (at the switch); remembering tothread the wires through the plastic shieldthey use. The cord grip can be re -used eventhough the cable is thicker. You may, onseeing the cable, feel it's a bit light, butremember these sets only consume about90 watts!

I XI1- ,... 1-

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R3

Figure 2. la) The foil pattern, and 1131 component overlay for the TX10 modifications board.

Photo 2: Internal view of the prototype board fitted unto the TX10 chassis. This clearly showsthe PCB pillars and neat layout - essential to prevent fouling any of the wiring inside the TV.


PROJECT

0701 CHOPPER'Os r --T.70,C704

242'. - 242 R702 27S -JISY BUMS

C3N3 170,7g

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TB 0702 TBKi

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5701

100AT

PARTS LIST

ResistorsR1,20R2,4R3,3585,6,7,8,12,18.21,22R9,11,26,27,28,29,32R10R13R14R15R16R17R19R23R24R25,34R30,31R33R36R37

CapacitorsC1,2,3,7,9C4,5,6,10C8

SemiconductorsQ1,6,7,02,3,4,5FET 1

D1,2

75R3k93k cermet pot10k47k1OR5R639R

820R39R82R

680R22k39k

100k15k56k

100R1k

15u 16V elec.100n poly.10u 16V elec.

BC183LBBC213LB2N3819LM733CN1N4148

INSTALLATIONNow if you are wondering how all this

can be done without an isolating toroid;refer to the circuit diagram in Fig. 3. TheLOPT provides the barrier required and thechopper chassis (shown dotted), which isat about 1/2 mains potential, places theset chassis likewise via the high impedancepath of the combined componentR701/C701. Hence the exposed metalworkof the set may be earthed without detrimentor risk. Don't forget C10, a 100 nf, whichjust fits on the copper side of the TXIOaudio chip between pins B and D. This isfor audio continuity during certain modes.

Cut the copper (for about 1/16") at thepoint shown on the signal board to sever

C 7i2'On)

IL702

Figure 3: Circuitry comprising the powersupply section of the TX10.

the land between PL1 and point H andmake pin 1 of plug one +12V by taking itto pin 3 of plug two. This is because theVTR time constant may be required evenwhen a UHF input is used eg Philips 1500and 1700 machines modulate their pictureson UHF, so the AV button cannot be usedbut the VTR time constant is still required.When the button marked AV is used, ofcourse, the modified TX 10 reverts tomonitor operation so a UHF input has noeffect.

To simplify matters, I have used thesame letters as the circuit where applicable,so F goes to F on wirewrap pins and H goesto wirewrap H, etc. Only the black wiregoes to a pin intended for a socket, i.e. pin10 of PL4.

R & EW

Your ReactionsExcellent - will make oneInteresting . might make oneSeen BetterComments

Circle No.

13141516

DECEMBER 1982

Figure 4: Connection details for wiring the monitor board to the television's signal board.

27

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Technical ApprovalAll products meet the British Telecom Technical Guide foracoustic coupling.

Software Available for:PET Series, Apple, BBC Micro andmany others.

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70FM1 12 06 6.8570F M3 1995 13.2570FM10 30.70 22.1070FM3/ 10 19 75 14.2070PA/FM10 19.70 3486

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144FM1OA 1996 13 95144FM108 33 36 25.95144LIN10A 2'990 19 87144LINIOB 36110 26.96

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At last the message has comethrough, all you old solderers canthrow away the soldering irons andthe perforated circuit boards. NOWyou can use PROTO-BOARDSfrom GSC. Despite daily break-throughs in components andpackaging, designing and testingnew circuit concepts is often a lotmore manual work than creativework. Not surprising, if you areusing old-fashioned perforatedboards and time-consumingsoldering. With PROTO-BOARDSany component can be plugged in,tested, removed, and used again.Circuits can often be designedfrom component pinouts and thecircuit diagram does not need tobe drawn until after the circuit isworking properly. PROTO-BOARDdesigning is very much like carefulsingle -sided printed circuit design interms of the effects of parasiticsand in terms of operation at highfrequency or low levels. Well -planned grounds and judicious useof shielded cable can permitoperation through VHF frequencies.So, you old solderers, stopsoldering on! Send off for ourFREE 40 page catalogue; we havea PROTO-BOARD to fit any sizebudget.

PROTO BOARDSModels P8 203. PB 203A and PB 203AK offer a largebreadboard rig area and a built in regulated power supply1,00.0d ,n a rugged metal cabinet. Models P86 to P8105 offervarious breadboarding areas screw mounted onto sturdy beckplates with non slip, non -scratch vinyl feet. Red and blackbinding posts are included, the red being electrically insulatedfrom the back plate, the black being electrically connectedfor ground.

PB 203Includes 5VDC. 1 amp power supply, available at bindingPosts: two binding posts I V 1, V21 remain uncommitted. Theperfect board for TTY and other 5 volt logic designs.

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5.5 to 18 VDC and 5.5 to 18 VDC power supplies, eachcapable of supplying 500 mA at 15 VDC. Power supplies arefactory preset to .! 15 VDC but can be independentlyadjusted.

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GLOBAL SPECIALTIES CORPORATION


DECEMBER 1982 29

1

David Strangereports on themore interestingof the two recentgatherings atBrighton- the InternationalBroadcasting Convention.'"

The International Broadcasting Convention, IBC, is an annualevent that takes place alternately in Brighton and Montreux. Thisyear it was the turn of Brighton to play host, and the conventionwas held at the Metropole Centre.

The first thing that came across was the emphasis on satellitebroadcasting. Along the sea -front amassed an impressive array ofvarious communication -dishes, all pointing to the sky. The BBC,IBA and outside -broadcast manufacturers, were very keen to showeveryone their latest OB vans - so these were also lined up nose -to -tail along the sea -front.

Inside the exhibition, every conceivable electronic trick relatingto video was on offer. And if you didn't want to make a picturechange shape or colour and spiral off the screen, then you wereat liberty to play with the latest TV camera - that is, if you couldfind the latest from amongst thousands on offer!

NEW LONDON COMMUNICATIONS CENTREOn the serious side (although, to look at the model it is difficultto take it seriously), news emerged of a communications centrebeing built at Hammersmith, London.

Apparently, London is the busiest news centre in the world, withmore than 60 international bureaus using local facilities to relayreports from America, The Far East and The Middle East. Thegiant American networks collect stories from half the world, tobe edited in London before being satellited back to the US. Apartfrom the Americans, who spend £5 million annually maintainingtheir UK operations, other TV news teams must, at the moment,compete with one another for essential technical services. Thisusually works on a first come, first served basis. So during timesof crisis, such as during the recent Falklands campaign, the situationbecomes totally chaotic and the demand for facilities far exceedssupply.

The London Communications Centre is being built at anestimated cost of £40 million. The massive complex, with itsstudios, post production areas and computer-linked offices, hasbeen designed primarily for the international news agencies. Itshould be operational during 1984, working 24 hours a day, 365days a year. The Centre will have its own ground station, usingthe Atlantic satellites and, when launched, the medium distancesatellites which will cover the UK and Europe.

TV companies will be able to rent a number of units within thecomplex. Each of these units will have access to an impressive rangeof links, standards conversion, telecine, studios, editing suites andtheatres - the Centre being manned by 250 personnel.

AUDIO TEST COMPUTERUnsure of whether your Hi-Fi is performing as well as when youfirst installed it? Ortofon have the answer with their TC3001 TestComputer - that is, provided you can afford the £3K price tag!The TC 3001 probably is a bit on the expensive side for home use,so Ortofon - who manufacture 1/2 million cartridges a year -are aiming at the professional user of disc equipment. For instance,a radio station will be able to check the performance of a discsystem, on the day of installation, and later determine any fall offin performance as wear takes place.

The sign along Brighton seafront welcoming

visitors to the conference

f the CommunicationsCentre being built

Model oat Hammersmith.

The Ortofon TC3001audio test computer.

The computer is able to test any record deck and cartridgecombination, and connects to either the cartridge output directly,or the preamplifier output. The user is prompted, by instructionsfrom an alpha -numeric display, through the various tests; whichstart with putting the pick-up onto a weighing balance connectedto the computer. This having been done, various tracks of a testrecord are selected and played according to the displayedinstructions.

Once all the appropriate tracks have been played, the computer,


A new developmentin mixer technology

from Audix.

!!: I lit; tIll-.. .

Inside the BBC's mobile radio station.

Outside broadcastunits with

their transmittingdishes.

having stored the results, can print test parameters onto a sheetfor future reference. A complete check-out of a disc reproductionsystem takes about 2 minutes to complete. The tests are made inaccordance with IEC recommendations, but since only softwarechanges are required, Ortofon can make the instrument measureto any reasonable specification a customer may require (Incidently,when I was given a demonstration of the TC 3001 it did not tellme to clean the test record - you can't leave everything to themachine!) L

The tests carried out by the TC3001 are: output (ref 1 kHz),tracking ability, phase and frequency response for L and R (20Hzto 20kHz), resonance, speed and signal-to-noise ratio.

AUDIX ASSIGNABLE TECHNOLOGY DESKAudix Ltd. the well known audio mixer manufacturers, have beentaking a side -ways look at mixing desks. At the IBC, they weredemonstrating something called an Assignable Technology Desk.

Mixers of recent manufacture have been what is known a 'inline' types - that is, each input channel has been a modulecontaining the main fader, routing switches, prefade listening,equalisation and gain function controls as well as the electronics.All this has meant that desks have become broader and broaderfor engineers to reach across. Consequently, smaller and smallercontrols have to be used to get all the functions in - triple concentricsand worse are becoming commonplace.

The fresh approach taken by Audix results in a smaller and lesscluttered desk. All the controls, for each channel, apart from thefader, prefade listen and post fade listen, have been replaced byone push-button. However, when the button is pressed(electronically speaking) all the controls are reset, since the channelbecomes assigned to a set that is centrally situated. Then, this setare used just like they belonged to that channel alone; but oncepanned, equalised, routed, etc, the channel is de -assigned to makeway for the next. Finally, the settings for each channel are storedaway in a memory... and talking about memory, an additional 10different channel settings and group settings can be memorised forrecall at any time.

The new mixing desk is a significant step forward by Audix andshould be readily accepted by engineers because, unlike somesystems, none of the creative control is taken away. The centralarea is a fair size and control functions are given more graphicalrepresentation, with bargraph and alphanumeric displays, than isusual on standard mixers. Operationally too there has got to bean advantage in always going to the same place to carry out certaintasks.

One last, interesting note about the mixer beforeis that the audio signals never come anywhere near the desk itself,they are all processed by digital elements (in a rack), driven fromthe desk.

MOBILE STUDIO FOR BBC RADIOAs I said at the beginning, outside broadcast vehicles were linedup along the sea -front for inspection, but for the sound engineerthe BBC's Mobile Studio 3 `MS3' has got to be the most interesting.

The MS3 houses a talks area, control room and radio links'stowage area, and first went into service in April of this year forcommentary on the London Marathon - this was done from theroof of the vehicle!

Designed primarily for coverage of sports and current affairsevents, the MS3 had been in use in Brighton during the weekprecedeing the IBC, to cover the TUC conference. Within the van,the 30 channel Glen Sound mixing desk can handle up to 24 outsidesources, each with individual talkback and cleanfeed facilities - itis also fully stereo capable. There is room in the control room for2 record decks and 4 stereo tape recorders, with monitoring doneby BBC designed LS3/7 loudspeakers. (The television monitorsin the photograph are there to aid certain commentaries, not forthe benefit of bored sound engineers!).

Outside, a 10 metre pneumatic support can be erected to carrya range of aerials to receive off -air signals for monitoring and cuepurposes, or for the transmission of locally generated material forinsertion into the network.

Finally, for the transport buffs amongst you, the vehicle is 11metres long and 2.5 metres wide. It has dual steerable front axlesand is based on a Ford R1114 coach chassis.

MR&EW

Your ReactionsCrc[F. No Circle No

Immediately Interesting gg Not Interested in this Topic 71Possible Application 70 Bad Feature/Space Waster 72

_a

DECEMBER 198231

KYOKUTOFM -2030

THE KDK FM2030 got off to a less thanauspicious start when it failed the soak test.After a few hours on the bench, it locked ontotransmit - and stayed there. SMC advised usthis was due to a trapped wire (we sent it backwithout daring to fiddle).

Ah well, the R&EW curse strikes again.Despite this minor hiccup, the rig is

presented quite tidily, being somewhatreminiscent of Trio styling. Quite why LEDreadouts are so popular with transceivermanufacturers is still a mystery. Thefluorescent display system, of the newer Yaesurigs, displays the benefits of that technologyvery plainly - so maybe they have created along awaited trend towards readouts that canstill be read in bright daylight.

EYES FRONTThe handbook is a rather meagre offeringwhen put alongside the lavishly conceivedpreparations of messrs Trio and Icom. It

7 ANT

L.P.F.

APC DET1N60

APC2SC1815

APC2SC1815

25A1015

RF PA

5-1077

25C1815

DIAL

P`

144ffliz

XMT DET1N60

2SC2053

AND GATETC4281TTt-

RF AMP

.ABIP

35K74

TX STOP2501815

NITISV50

RESMATRIX

LUTCHMN1201

"Nassalttlivtt*rt.its ssasitivavtm.

William Poel canters round the circuit of the KDKFM2030, to see what's on offer from this lesser knownsource of Amateur technology from The Far East...

nevertheless puts across a succinct andadequate explanation of the rig functions.

The description of the electronic alarm, thathoots if you attempt to over -range the unit,is described as "Eyes on the Road" formaximum driving safety. It seems nearlyimpossible to pick up any piece of Japanesetechnology without the wretched thing bleepingimperiously at you sooner or later.

The scanning and general functionsrepresent (as they say) a third generationapproach, which seems to make provision foreverything imaginable, yet present an elegant

B.P.F.

'AUTO TUNA15v50z3

UTO TUN15V50:4

14.2922MHz

XTAL OSC2501923

1ST MIX15E74

METER LED.rm8051

BAL. MIX2SK19z 2

BUFF AMP25C1923

UL CON25C1815

TRIP5516

ZEIT DATA15553

10.7MHz

LED DRIP

BUFF AMP25C1815

BUFF AMP2SC1923

BUFF -AMP25C1923

2501923

package that isn't smothered in knobs andgratuitous lights. The use of the LED signalmeter comes fairly close to the gratuitous, butthen everyone uses one. As one amateurobserved, it tells deaf users that they could heara signal if they weren't deaf.

SMC's sales blurb on the transceiver neatlysummarizes its functional quality, so we'll justtake the lid off and peek inside

ANOTHER VHF TRANSCEIVER CIRCUIT?At the not unsubstantial risk of describing andprinting yet another 2m transceiver review, we

2ND LO, 2ND MIX, 2ND IF AMP, LIN, DET,NOISE AMP MC3357

SIC AMP570 DETr 1501815

-7--

XTAL OSC2SC1815

-10-110.714Hz

251(19

BUZZER

MODISV50

ISV50

BUFF AMPTA7302

L.P.F.(3KHz1

ACT FIL2001815z

SCAN COSTTC4011

AMP.LIMTA7061

TONE 050

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REVIEW

must come clean and confess that there isvirtually no innovative aspect of the circuitwhatsoever. It's all good tried and tested stuff,and it works.

Refreshingly, the first IF uses a real10.7MHz stage, not a marginal variant thereof;although the second filter at 12kHz bandwidthis arguably on the wide side. Well-behaved andconservatively deviated UK FMer's might findthe 12.5kHz channelling option just a shadeacademic, unless the filter is swapped for an8kHz version.

The block diagram of Figure 1 gives theoverview, but one or two interesting bitsemerge when you move into the detailed circuitdiagram of Figure 2 . All the RF tunedcircuits are track tuned using varicap diodes.Not just the receiver front end circuits, but thebandpass filter following the final mixer in thetransmitter loop. Since KDK take the relativelydirect route of mixing the receiver LO with thefirst IF offset (10.7MHz) to obtain the outputfrequency for the transmitter, it'sunderstandable that there should be someconcern for the purity of the signal at this point.Maybe not so much for the meagre UK spanof 2MHz, but for the rather more demandingUS range of 4MHz.

It's as well to remind UK readers that thereare actually precious few regulations governingthe outputs of amateur radio transmitters,other than requiring that they should not causeinterference to other users. Uncle Sam's FCCties it down a lot tighter, placing emissionregulations on the equipment that are on a parwith the MPT soma for mobile radio in thiscountry. Even so, receiver and wide-rangingenviromental considerations are not nearly asimportant as simply keeping the harmonics andmixing products out of sight.

Incidently, one little gem you might like todistil from this circuit and file away for futurereference is the modulator circuit.

SHAKE IT AU. ABOUTAs the more discerning readers of thismagazine will know, it's not good form towave the control voltage of synthesised VCOaround in the attempt to FM modulate it. Allsorts of funny things go on that givemathematicians paroxysms of the Fouriervariety - but practically, the modulation levelcan vary rather frantically from one end of theband to the other (very few varicaps boost alinear slope on the bias/capacitance curve).

Once again, the 2MHz of the UK 2m bandcan actually be managed tolerably well in thisfashion, but in order to satisfy world marketrequirements, most Jap rigs use a VCXO andmix-up process - since the VCXO modulationlevel is constant. The KDK rig achieves a+ /-5kHz deviation level by wobbling a10.7MHz crystal with a varicap. Cynics mightsuggest that you really shouldn't be able to geta linear swing of 10kHz from a 10.7MHzquartz crystal, and that L11 (12uH) is just abit on the naughty side, since it somewhatloosens the grip of the crystal on the wholeoscillator. Nevertheless, KDK get away withit, and you might like to bear this techniquein mind as a short cut to turning our

Internal shot of the 2m transceiver.

forthcoming 2m synthesised receiver (derivedfrom Keith Mitchell's Airband Receiver) intoan instant transceiver.

SYNTHESIS MADE EASY!The need to provide fine tuning at VHF hastended to drive designers away from the elegantsimplicity of the dual modulus prescalar anddirect VCO approach (like the Airband RX),and into all sorts of contortions with R2R D/Ato control VCXOs in roundabout loops. OK,the VCO runs at the same frequency at the endof the day (viz 133MHz-odd), but actuallyusing 3 crystals and lots of other bits to boot.You can bend the frequency of the airbandsynthesiser quite a long way by simplytrimming the reference frequency - enough, itwould seem, to provide the degree ofinterpolation required for Rrr.

Refer back to fig. one for the route adoptedin this set, which avoids the use of prescalarby the usual mix -down to the LSI PLL (ICI)frequency range.

ON THE AIRDespite frantic attempts to extract some formof definitive comment from local amateurs onthe signal qualities of the rig, I couldn't. "Itsounds alright", they said.

The receiver is certainly sensitive, and the

8640B tripped the mute in at around 0.15uV(which is the threshold of believable accuracyfor most signal sources anyway), and thetransmitter (as expected) produced nothingsignificant above -70dB.

Would that we might be more enthusiasticabout the whole thing, but to be perfectlyfrank, it's not easy.

The main 'feature' is the £199 price tag.So.... the receiver's not as good on overloadas an ICOM IC25E (sorry, but someonezapped our 150MHz BW scope, or we wouldhave showed you a pic of what a sinewave200mV input at 145MHz looks like, after thevaricap on the output of the RF stage had doneits stuff), but for most mobile users that canbe a rather academic feature anyway.

If you want a rig that does all the usual partytricks and provides 25W in a fairly compactpackage, this looks like reasonable value.

R&EW

Your ReactionsImmediately InterestingPossible applicationNot interested in this topicBad feature/space waster

Circle No.37383940


BATTERYBONANZAHigh quality Every Ready Ni-Cad batteriesat low, low prices

AAA 1.29AA 0.92C 2.71Sub D 2.48D 3.51PP3 4.26

In addition a versatile charger that, with its range ofadaptors will allow most batteries to be safelycharged is also available.

Charger 16.05Adaptors 1xD 2.021xC 2.022xAA 2.02Also shown is a unique series of adaptors that will allowsmall Ni-Cads to be used in place of larger cells.

Sold in pairs these enable an AA size to be used inplace of a C cell, a C instead of a D, or an AA in placeof a D.

Battery Adaptor 1.10Finally a battery tester, which may also be used as acontinuity checker is available for only £ .75.

HOW TO ORDERrite your order on a separate piece of paper and send

together with the coupon below and your Cheque/Access/Barclaycard No. to

R&EW Special Offers,117A High Street, Brentwood, Essex CM14 4SG.

All prices include VAT at 15% but please include postageand packing at 50p per order.

Also please remember the two special offers were featuredlast month, the test probe and glue gun. Both of these arestill being offered at the fully inclusive price of £9.95 each.

r

This rugged 10Aautoranging LCDdigital multimeteris professionallydesigned for thoseof you who like theprofessional approach.

At our low price of£49.95 inclusive its timeyou replaced your old meterwith this R&EW bargain.

This offer is limited to the first100 orders - first come, firstserved so place your order now.

DECEMBER 1982

Name.

Address

Cheque/P.O. No.

Access/Barclaycard No.

Signature

J

35

alf

Peter Luke looks at a newcamera, a new recorder, amidget monitor and muchmore besides.THE IDEAL VIDEO CAMERA wouldseem to be one on which there were no usercontrols with the exception of the powerzoom rocker switch. The camera would beready to point and shoot as soon assomething to point it at materialisedwithout having to fiddle with WhiteBalance, sensitivity controls or focus.Judging by some of the recent offerings bycamera manufacturers, far fromapproaching this ideal, the products arebecoming ever more complex meaning thatvaluable recording time is lost while makingsure that the camera is set up to suitprevailing conditions.

The new camera from Panasonic,designated the WVP - 100E, bucks thetrend however, with the removal of one ofthe most important camera controls -

namely focusing.The WVP - 100E features an ultrasonic

auto -focus system which, according toPanasonic can lock onto both stationaryand moving subjects. Based on anultrasonic system, the focusing is obviouslynot affected by low lighting levels orsubjects with little variation in contrast.

The camera 'looks the business being',what Panasonic choose to term, ENGstyled. The camera incorporates a 6:1 twospeed power zoom, a macro facility and anAGC switch that allows it to be used in lowlight conditions.

The viewfinder is a 1.5" CRT andprovides indication of a camera/recordercombinations's status, ie low battery,record run etc. in addition a stop -watchtimer and date setting ability (forchronological record) are built in.

Fade in/out and negative/positivepicture reversal, a la Sony 400P, also makean appearance on the WVP - 100E.

On the Thorny issue of camera - recordercamera, while

designed for use with Panasonic's NV -100B portable recorder, features acompatibility switch that allows it to beused with other brands of VHS recordersthat have different trigger polarities inaddition, an optional adaptor can be usedto hook the camera up to Sony standardcamera connectors.

When used with the aforementioned NV- 100B recorder, the remote control unit ofthe recorder may be clipped to the camera'shandle and thus offer a selection oftransport control functions (record, play,cue, insert edit etc) from the camera. Thissort of function was found to be very usefulon the Sanyo portable system reviewed lastmonth.

26,

The camera should be available by thetime you read this, pay a visit to yournearest Panasonic dealer and tell themR&EW sent you.

TAPING WITH TELEFUNKENTelefunken have recently introduced a fullfacility VHS machine at the quite keenprice of £600. The front loading machinepacks in just about everything that'sanything in the features stake - Dolby, 14day / 8 event timer, IR remote control, 9times visual search, insert editing, slowplay, pause, frame advance, memoryrewind, tape indexing etc, etc in short - it'sgot the lot.

What's more the machine is designed torecord and playback both PAL andSECAM G formats and has a UHF/VHFtuner.

A very impressive machine that shouldbe worth checking out.

MIDGET MONITORA monitor that may well find applicationsin portable recording set ups is the new 2inch TV2S from Thandar.

By making use of phase locked line andinjection locked oscillators, the TV2Sprovides a very good picture lock. Themonitor provides a 525/625 capability anda 75R bridge option.

It is powered from its own internal ni-cad supply but can be supplied from theusual range of sources, car battery, mains(with adaptor) etc.

Details fromThandar Electronics,London Road,St. Ives,HUNTINGDON,Cambridgeshire,PE17 4HJ.

AMERICAN ADD-ONSTwo quick items from the States now in theshape of a stereo simulator and a roomexpander from MFJ enterprises.

The stereo simulator uses a comb filtertechnique that puts alternate 1 kHz bandsof the audio spectrum into the left and rightspeakers, thus giving an impression of astereo image from a mono source. This

making an appearance, and while reportedto be an 'interesting' effect rather than aconvincing stereo image, is better than thecrude high/low filtering techniques thatsome record manufacturers adopted in thelate 60's and early 70's to simulate stereo.

The room expander is a sophisticatedreverberation unit and by means ofAmbience, Expand, and volume controls,is said to be able to create the impressionof 'big screen sound' in the most moderateof surroundings.

Put the two units together and you havesix sound modifiying controls to twiddlewith, it'll give you something to do if youlose interest in what's happening on the TVscreen.

More information from:MFJ Enterprises,921A Louisville Road,St Arkville,MS 39759.

ET VT'EDIf we are to believe the various spokesper-sons representing the vested interests of thefilm industry, many video recorders spendmost of their time producing illicit copiesof the latest box office hit. It cannot bedisputed that pirate copying of films is athorn in the side of the movie moguls withthe impact of the launch of a film such asET being much diluted by the fact thatmany people will have already seen StevenSpeilberg's latest money spinner. Fiftypounds was the asking price for a firstgeneration copy of the tape at one of theless reputable purveyors of video softwarethat R&EW knows about.

MFJ STEREO SYNTHESIZER

INPUT SEL

SEPARATiON

MODEL MFJ-1501

The industry is so concerned about thisblackmarket dealing in films, that it is ac-tively campaigning for a levy to be charg-ed on all blank cassettes sold - a move thatis likely to be strongly resisted not only bythe various tape and recorder producers,but by the public at large. In the meantime,phone numbers for members of the publicto, in the strictest confidence, provide in-formation on any illicit sources of software;vigourous prosecution of all personssuspected of involvement in illegal copying;and various watermark systems to enableany legal tapes to be positively identified;(and hence by implicaton any niggers in thewoodpile to be spotted); are all part of thebattle against the pirates.

The answer to the problem would, ofcourse, be a copy guard system that would

Video BNC Saba VR6012Audio 3.5mm Jack Saba VR6024Akai VP7100 Saba VR6069FergusonFergusonJVC

3V013V24H R2200

VideoAudio

PL259RCA Phono

JVCNord mend

HR4100V250 Sanyo VTC 5500/5600

VideoAudio

BNC .5 Pin Din

VideoAudio

Phono5 Pin Din

AkaiFergusonFergusonFergusonJVCJVC

VS1OEK3V233V293V30/3V31HR 7200/7300HR 7650

Aka,AkaiSharpVideoAudio

Sanyo

VS9700VS5EKVC 2300BNCRCA Phono

VTC 3000JVC H R7700 Sanyo VTC 5300PTelefunken VR 520 Sony SL C5Sony SL C6Video 6 Pin Din Sony SL C7Audio 6 Pin Din Sony SL FI

GrundigKortingNordmende

2 x 4/2 x 4 PlugVR 8V 350/V 500

VideoAudio

RCA PhonoRCA Phono

Philips VR 2023 Fidelity VTR 1000Philips VR 2025 GEC 4000/4001Saba VR2000 Granada VHS WH1/3Saba VR6000 Granada VHS VH1/2Hitachi VT 5000 E/ER

HitachiHitachiHitachiHitachiHitachiHitachiHitachiToshibaToshiba

VideoAudio

AkaiAkaiAkaiFergusonFergusonFerguson VGranadaJVCJVCJVCJVCNormende

NormendeSanyoSharpSharpSharpSharp

WI ROOM EXPANDING AUDIO ENHANCFR01,311.4CF

4 .0.t11,001

of 1

VT 5500 EVT 6500VT 7000VT 8000/8040VT 8300/8500VT 8700,9700VT 9300/9500V 5470V 86008

PL2595 Pin Din

VS 9300VS 9500VS 980032923V16

Star 3V22VHS TJIHR 3200HR 3320HR 3330HR 3660SpectraVideo VISV200/V400VTC 9300VC 6300VC 7300VC 7700'7750HVC 8300H

VOLUME

POWEN

Oh -

a

somehow allow tapes to be played back viaa TV set but NOT to be copied. Some ideasalong these lines have been tried in theStates and usually involve some distortionof the recorded sync pulses, distortion thata TV receiver circuitry is able to cope with,but which throws any slaved recorders ser-vos into a state of confusion. The problemwith most schemes along these lines is thatthey are very easy to counter and numeroussync stabilisers are freely available in theStates.

If the manufactures of video hardwarewere to show some positive commitment tosupressing the pirate trade, a workableform of copy guarding could be a viableproposition. There seems little prospect ofthis, however, and unless some technicalperson with the interest of the movie in-dustry has some flash of inspiration, thepirating problem will remain.

LEADING ASTRAYThere are a number of occasions when co-pying can be carried out without breakingthe law of the land; assembly editing ofyour holiday tapes for example. To caterfor these situations many firms are nowsupplying leads to connect to the many andvaried audio and video in/out sockets en-countered within the various recorders.

The list below details some of the in-put/output connections of the morepopular makes of machine and may be ofhelp if you're trying to sort out the leadsto copy from your machine to that of anET?-oops.

R & EW

Your Reactions Circle No.0 Immediately Interesting 20

wPossible applicationNot interested in this topic

2122

MODEL MFJ-1500 Bad feature/space waster 23

r4it(c11141VI(9A Design by Chris Parsons.

A Sine- Cosine Oscillator with Variable Switched Frequency Control.

SUPPLY VOLTAGEOV 9V +9V

Rvw5M6

R256k

C247u

RV1a10k

1081k

C1

R6100k 1 13

820n

47u

O/oC3/SW1a 0_1 C5

C4 82n

4

IC1a

R356k

R42k 2

IC1d

12 11

C6820p

8n2 ZD1 ZD24V7 4V7

RV lb10k

R9 R10100k 1k

4

R5220R

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100k

820nC7

428r711--41,,,

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9

10

IC1c

0-11-4C10820P

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1811100k / COSINE OUT

NOTE: IC1 IS LF347

0 SINE OUT

0 COMMON

Figure 1: Circuit diagram of the quadrature sine - cosine oscillator.

MOST SIGNAL GENERATORS haveeither just sine or sine, square and trianglewave outputs, with various amplitude andrange controls. This arrangement is quiteadequate for most purposes, but there doexist certain special applications wheresomething more exotic is required. Onesuch is obtaining two sine waves, 90 ° out -of -phase, whose frequencies are matchedand variable. With a LF output, it'spossible to simulate a radar display - butmore of this later.

The circuit shown in Fig. 1 is aquadrature sine -wave oscillator, withswitched frequency bands (RV1 set for noattenuation) of 2,20,200 and 2000 Hz. Eachband is fully variable over a 10:1 range, byadjusting RV I - a dual ganged linear slideris useful here. The output frequency iscomputed from foul= 1/2rRC,where R istaken as R6 = R7 and C as the capacitorsselected by SWI. For instance, with SW1connected to C4 and C8 (R = 100k) thefrequency will be variable from 1/(2 x 3.14

x 82 x 10-s x 100 x 103) = 20Hz.The oscillator is based around the LF347

quad BiFET operational amplifier. Twointegrators, ICIc and d, are connected toan inverter, ICIa, with unity gain. Theinverter is part of a positive feedback loop,

which is stabilised by the addition of twolevel -clamping zener diodes, from pin 3 (viaR4) ICIa. There is also a high value resistor(R5) to provide the small amount ofnegative feedback necessary to ensureoscillation occurs immediately at power on.With the values shown, you should obtainan 8V peak -to -peak sine -wave from bothoutputs. The rest of the circuity is fairlystraightforward. Supply decoupling isprovided by Cl and C2 - though, it maybe necessary to add two parallel capacitors(of about 47n) to remove any HF spikesfrom the power lines. Current consumptionis quite low (at 4mA) into a high impedanceload, so battery operation is possible.

An application for this sine -cosine signalgenerator is as a simulator By feedingthe outputs into an oscilloscope - sine tothe y input and cosine to the x input - andselecting the lowest frequency band (C3 andC7), a simulated radar trace is obtained.The screen will show a circular Lissajousfigure, with the spot sweeping round at aspeed controlled by RV1. Other usesinclude VCO's in sythesisers, effects unitsand test gear.

INR&EW

Your Reactions Circle No.Excellent - will make one 44Interesting - might make one 45Seen Better 46

Comments 47

1

INT

INVERTERLEVELCLAMP

FREQUENCY 1,ADJUST

INT

0 0SINE

COSINE

OSCILLOSCOPE

1/00151bWASOUllo,M

AI.

10 OOOOOO IA/MOOOMPtd,

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0 0VI IN

0 0X IN Y2 IN

Figure 2: Block diagram of the oscillator showing connections for creating a simulatedradar trace.


The capital's longestrunning HobbyElectronics Show

1 0-1 4 NovemberThe Royal Horticultural New HallLondon SW1

......

f Admission £1.00 (50p under 16's & OAP's) 75p with this coupon:1I IOpen Wednesday 10 November 1000-1800

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0747-840722 01-286 9191II Supported by Electromcs Today International . Hobby Electronics . Personal Computing Today

I Computing Today . Personal Software with a combined circulation of 230,000 copies a month 4/

DECEMBER 1982 39

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PRICES SHOWN EXCLUDE VAT

UK CUSTOMERS PLEASE ADO 19%

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WIRRAL, MERSEYSIDE, Lel fiXT

Tel 051 342 4443 Cables CRYSTAL. BIRKENHEAD

CRYSTALS MANUFACTUREDTO ORDER

Prices shown are for "one off" to our standard amateur specs:closer tolerances are available. Please send us details of yourrequirements.A Low frequency fundamentals in HC13/U or HC6/U

Total tolerance ± 100ppm 0° to 70°C6 to 9.999kHz HC13/U £32.8010 to 19.99kHz HC13/U E31.0020 to 29.99kHz HC13/U E23.0830 to 59 .99kHz HC13/U £21.7360 to 79 99kHz HC13/U E15.6980 to 99.99kHz HC13 /U E13.08100 to 159.9kHz HC13Et6/U E11.32160 to 399.9kHz HC6 /U £7.83400 to 499.9kHz HC6 /U £7.00500 to 799.9kHz HC6 ILI

B High frequencies fundamentals/overtonesAdj. tol. 20ppm, Temp. tol. b 30ppm - 10°C to +60°C

800 to 999.9kHz Ifundl HC6/U £11.011 to 1.499MHz (fund) HC6/U 01.251.5 to 2 -59MHz (fund) HC6 /U f5.362.6 to 20.9MHz (fund) HC6 /U £4.873.4 to 3.99MHz (fund) HC18 & 25/U £6.754 to 5.99MHz (fund) HC18 & 25/U £5.366 to 21 MHz (fund) All Holders E4.8721 to 25MHz (fund) E7.3125 to 30MHz (fund) f9.0018 to 63MHz 13 0/T) E4.8760 to 105MHz 15 0/T) £5.61105 to 125MHz 15 0/T) E8.44125 to 149MHz 17 0/T) £8.62149 to 180MHz 19 0/T) E12.75180 to 250MHz 19 0/T) f13.50

Delivery -Mid range 1MHz to 105MHz normally 4/6 weeks.Other frequencies 6/8 weeks.

Holders -Low Frequencies 6 to 150kHz HC13/U, 150kHz to3.4MHz HC6U, 3.4MHz to 105MHz HC6/U, HC18 /U orHC25/U, over 105MHz- HC18 /U and HC25/U.HC33/U (Wire ended HC6/UI is available on request as perHC6 /U. HC17/U (Replacement for FT2431 available as perHC6 /U at 35p surcharge on the HC6/U price.Unless otherwise specified, fundamentals will be suppliedto 30pf circuit conditions and overtones to seriesresonance.

CRYSTALS FOR MICROPROCESSORSPlease let us know your requirements eg 4MHz HC18 U.1 off E2.00, 100 off E1.10. 1000 off 99p, 2500 off 50p.

ANZAC MD -108 DOUBLE BALANCED MIXER5 to 500MHz supplied with full details for only £6.95.

COMMERCIAL AND PROFESSIONAL CRYSTALSNEW FASTER SERVICE

We are now supplying crystals to most commercial and MILspecifications in the range 1MHz to 60MHz ordered in smallquantities in 2i weeks AT NO EXTRA CHARGE. We also haveeven faster EXPRESS SERVICES available for that VERYURGENT order.We can also supply crystals for commercial applications e.g.1xii,oprocessor, TV etc. at very competitive prices. Let us knowyour needs and we will send you a quote by return, alternativelytelephone or telex our Sales Engineer Mr Norcliffe who is normallyavailable in the office for technical enquiries between 4.30 and6.30p.m.

TWO METRE CRYSTALSCRYSTALFREQUENCYUSE (TX orend HOLDER(

OUTPUTFREQUENCY

D --,is IQ

r'-

4X2kr tO

D

.

4I2

GO

7D --m n

x_2yX,

,,74 XX ,,,,2 ..

ie

n ...._

--6 15XX.4

X,.. ,T,r--

m -,

Xjc

X,..1.-

D ..,

nXX >i. ,..

X,-

7

5'XXXX,a ...-

D .....

X.X

D D....

n nxi. .

XX1 2

si

144-4 1433.21 b b e b e e144.800 e c c e144.825 e e e a

144.850 e e145.000/ROT c c145.025/R1T e e

145.050/R2T e e

145.075/R3T e e

145.100/R4T e e145.125/R5T e e

145.150/R6T e e145.175/R7T e e

145.200/R8R e c

145.300/S12 e e

145.350/S14 e e

145.400/S16 e e

145.425/517 e e

145.450/S18 e e

145.475/S19 e e

145.500/520 c c

145.525/S21 c c

145.550/S22 c c

145.575/523 c c

145600/ROR c c

I45.625/R1R c c

145.650/R2R c c

145.675/R3R c c

145.700/R4R c c

145.725/R5R e c

145.750/R6R c c

145775/R7R e c

145-800/R8R c b b e

145.950/538 c a e e

PRICES: lal 12.15. lblE2.56, Icl £2.80 and (el E4.87

AVAILABILITY: lal, 1b1 and lc) stock items normally available byreturn (we have over 5000 items in stock). le) 4/6 weeks normallybut it is quite possible we could supply from stock. N.B.Frequencies as listed above but in alternative holders and/or nonstock loadings are available as per code lel.

ORDERING: When ordering please quote Il I Channel, 121 Crystalfrequency, (31 Holder, 141 Circuit conditions (load in pf). If youcannot give these, please give make and model of equipment andchannel or output frequency required and we will advise if we havedetails.

EXPRESS SERVICEMany types of made to order crystals are available on our"EXPRESS SERVICE" - with delivery of three days on our class"A" service. Telephone for details.

70cm CRYSTALSDue to the much higher multiplication involved compared with2 metres all our stock 70cm crystals are to a much higher tolerancethan our standard amateur spec. crystals.

We are stocking the following channels: -RBO, RB2, RB4,R86, SUB, 8810, R811, RB13, R814, RB15, SU18 and SU20 TXand RX for use with: PYE UHF Westminster 1W15L11, UHFCambridge (U10B). Pockerfone (PF1 I and UHF PF70 Range andStorno COL /COM 662 all at 12.55.

For other channels and or equipments crystals can be made toorder to the same closer tolerances as our stock range at a cost ofE5.72 for frequencies up to 63MHz and E6.58 for 63-105MHz or toour standard amateur specifications see "CRYSTALS MAN-UFACTURED TO ORDER" Prices opposite.

4m CRYSTALS FOR 7026MHz-HC6UTX8 7825MHz and RX6 -7466MHz or 29.7800MHz E2.56.

10.246MHz "ALTERNATIVE" I.F. CRYSTALS -£2.56For use in Pye and other equipment with 10.7MHz and 455kHzI.F.s to get rid of the "birdy" just above 145.0MHz. In HC6/U,HC18 /U and HC25/U.

CRYSTAL SOCKETS (LOW LOSS)HC/6U and HC13/U 25p each. HC25 U 20p eachplus 20p P&P (P&P free if ordered with crystals).

CONVERTER /TRANSVERTER CRYSTALS- HC18/UAll at E3.00, 38.6666MHz 1144/281, 42MHz (70/281, 58MHz1144/281, 70MHz 1144/41, 71MHz 1144,21, 96MHz11,296/432/1441, 101MHz 1432/281, 101.50MHz 1434/281,105.6666MHz 11,296/281 and 116MHz 1144/281

TEST EQUIPMENT FREQUENCY STANDARD CRYSTALS200kHz and 455MHz in HC6 £3.50100kHz in HC13 /U and MHz in HC6 /U £2.955MHz in HC6/U and 10MHz and 10.7MHz in HC611.1and HC25/U E2.80.

AERIALSMULTI -BAND INVERTED "V" TRAPPED DIPOLE

80 Thru 10m -Rated @ 2kVV Only 26m long.Introductory offer E32.00 VAT 136.80 INC VAT) P&P E2.50

THE ARAKI RANGE OF AERIALS10m whip only 1.3m long with magmount £18.00 P&P E3.0010m whip only 1.3m long with guttermount E15.20 P&P E3.002m 5/8 X whip with magmount £16.00 P&P E3.002m 5/8 X whip with guttermount E13.20 P&P E3.002m 1/4 X whip with magmount E12.50 P&P E2.502m 1/4 X whip with guttermount £9.70 P&P E2.502m/70cm DIBAND whip with magmount E20.90 P&P E3.002m/70cm DIBAND whip with guttermount £18.10 P&P E3.002 Base Station Aerials2m 5/8 X Ground plane 3.5db gain £18.95 P&P E3.502m 5/8 + 5/8 Colinear 6db gain E25.00 P&P E3.5070cm 5/8 + 5/8 Colinear 5db gain 125.00 P&P E3.50The Araki Range are handmade of top quality anti -corrosiontreated aluminium or stainless steel.

TERMS: CASH WITH ORDER -MAIL ORDER ONLY.PRICES INCLUDE P&P (BRITISH ISLES) EXCEPT WHERESTATED OVERSEAS CHARGED AT COST.

PLEASE ENCLOSE S.A.E. WITH ALL ENQUIRIES164 for further details

SUBSCRIPTIONS

With the increase in ourcover price this monthwe have had to adjustour subscriptions ratesaccordingly.

The new rates are asshown below:UK (12 issues) f13:00Overseas (12 issues)£13:50

If you want to be sure of getting YOUR copy of Britain's most informativeRadio/Electronics magazine, PLAY SAFE AND SUBSCRIBE. Fill in the form below.

rSUBSCRIPTION ORDER FORMII would like to subscribe to Radio & Electronics World for one year (12 issues) Please start my subscription'from the issue.

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/Please send this order form, with your remittance, to Radio & Electronics World, Subscriptions Department,145, yawing Avenue, Rayner Lane, Harrow, Middlesex. HA2 9RL


R&EW TRANSCEIVER PROJECT

CW GENERATOR

Design by Simon Ruffle G4EAG

THIS PROJECT is a CW Generator forthe R&EW transceiver. It provides a10.7MHz carrier, keyed by the mixer board(October R&EW) and a sidetone output,which can be fed to the audio amplifiersof the receiver. CW generation is not linkedto the SSB module, because itwould preclude the construction of a CW-only transceiver. The CW generator has,however, been designed for DC mode -switching.

PRINCIPLES OF OPERATIONThe CW generator consists of two distinctparts; the 10.7MHz oscillator and the audiosidetone oscillator. These are linked onlyvia the DC switching arrangement. Modeselection and transmit/receive switching inthe transceiver are simplified to + 12V'enable' lines (one for each mode) and a+ 12V 'transmit' line. All boards in thesystem must obey this protocol. Therefore,the CW board will deliver a continuous10.7MHz carrier wave drive when enabled.This is keyed by the mixer board, and, atthe same time, delivers an audio sidetonewhich must not be present when USB, LSBor FM are transmit- keyed.

All mode generators are now being fittedwith a diode switch, which allows them to

1 C4

I100n

X110.7MHz

be connected together at the mixer's10.7MHz input. This requires an additionalresistor/diode arrangement (identical toR17/DI) to be fitted to the output of theSSB generator (July 1982). Also, a 1mHchoke is connected across the input of themixer board to provide a DC return path.

CIRCUIT DESCRIPTIONThe 10.7MHz carrier -oscillator is similar indesign to that used in the SSB generator -with the addition of tuning adjustment.The output is taken from a tap in theemitter resistor and fed to a 10.7MHzceramic filter. The stopband characteristicsof this filter are used to remove unwantedharmonic energy and the output is fed toa buffer amplifier (Q2). It is then passedto the 10.7MHz drive -input on the mixerboard.

The diode switch, DI, relies on a DCreturn path at the mixer input; when 12Vis available from R17, DI conducts andallows the CW energy to flow. When DIis reverse biased, it will offer a highimpedance to the other mode generatorfeeding the mixer.

The audio sidetone oscillator is of the'twin T' variety and has frequency controlvia RV1. This kind of oscillator needs a

+12V CVVENABLE

Q1BF256

C239p

Cl39p

R2150R

R9100 RSW/

tP5 R73k9 390R

ce D110n IN4148

Q2

z

R17CW10k OUT

ZTX 3866

R6 C52k7 Pe 10n

470R

C 1 010n

high impedance buffer, provided by Q5.This should give adequate output to feedthe receiver's audio amplifier or a separateamplifier if prefered.

The + 12V 'transmit' line, which alsoserves as the keyed line in CW, is availablein all modes. It therefore needs to bedisconnected from the audio oscillatorwhen CW is not selected. This isaccomplished by a DC switch, Q3, whichkeys the + 12V, from the CW enable line(under control from the transmit line), andfeeds it to Q4.

CONSTRUCTION AND SETTING -UPThe CW generator is constructed on a smalldouble- sided printed circuit board. Allearthed leads, passing through the board,should be soldered to the top planewherever possible. There is no need to testthe board in stages, though it may be usefulto try out the audio oscillator beforeconnecting the switching transistor, Q3.RV1 should offer a useful range offrequencies, but do not set it up yet (forthe moment, leave the sidetone oscillatordisconnected).

Wire the CW 10.7MHz output to themixer board and link the 12V 'transmitonly' pin (mixer) to the + 12V 'keyed line'

+12V KEYED LINE

R1018k

Q3ZTX108

3k9

C11 C12220n 220r*HI

RV110k

C7TSEE TEXT

Q4ZTX108

05C14 BF256

0.1-147

nR12 R1318k = 18k R14

47n120k

R161008

C151u

SI DETONE

C16OUT

100n

Figure 1: Circuit Diagram of the CW generator.

DECEMBER 1982 41

PROJECT

0

0000°S0

ogo 00

0080 S0 0 008

000 0

08

00800 0

0YY

00

Figure 2: The PCB foil patterns for the double sided board.

pin (CW). Now connect the 12V oscillatorpin to 12 volts and switch on the CW enableline. As you key the transmit line, you willhear the signal at the receiver; anywhere inthe 0-30MHz range. Tune VC1 until the`beat' notes are identical when the receiveris switched between USB or LSB. Thetransmit signal is now dead co- channelwith the receiver, and the beat note will be1.5KHz (the BFL offset). The implicationhere, is that in order to net accurately ontoa received CW signal, the transmit andreceive beat notes must be identical. It islikely, however, that the 1.5KHz note is toohigh for comfortable CW reception, andthis can be overcome by allocating one ofthe two BFO's for CW. This allows you tochoose your own CW note on, say, the LSBposition, and then use VC1 to match that

with the transmit beat note. Take care onceyou have done this - you can't work CWon the receiver `USB' position because youwill be way off frequency.

Once you have chosen your CW beatfrequency, you can match it with the audiosidetone. The sidetone is necessary becausethe receiver will be muted on transmit; itis possible, but unsatisfactory, to monitorthe transmitted CW itself. The sidetone,therefore, should be of the same audiofrequency as the beat note caused by thetransmitted signal. This is achieved byrotating RV1 until the two notes areidentical. Netting to a received CW signal,then, merely involves matching the receivedbeat note and the sidetone frequency.Beware, however, that the correct receiveBFO is selected to ensure co -channel

COMPONENTS LISTResistors (All W 5% carbon film)R1 33kR2 150RR3,7 390RR4,9,16 100 RR5,11 3k9R6 2k7R8 470RR10,12,13, 18kR14 120kR15,17 10k

p

PotentiometersVR1

CapacitorsC1,2C3,4,8,16C5,6,10C7 - see text.C9,15C11,12C13,14VC1

SemiconductorsQ1,5Q2Q3,4D1

MiscellaneousX1FlPCB

10k preset

39p ceramic100n monolithic10n monolithic

1u electrolytic0.22u F tant47n monolythic35p variable preset

BF256ZTX3866ZTX 1081N4148

10.700 crystalCFSH 10.7M1

ceramic filter

12VCW ENABLE

10.7N1112 -CW OUT

12VKEYED LINE

C15

Figure 3: Component Overlay.

operation.Two capacitors, C7 on the CW generator

and C22 on the mixer board, allow shapingof the CW signal, which eliminates keyclicks. Their values will depend on the typeof amplification (RF and audio) used,which can only be found byexperimentation. I suggest values of 330n,for both capacitors, as a good startingpoint. In fact, C22 is the more importantvariable because it affects the transmittedCW (C7 is only necessary to adjust forpersonal listening preferences).

FINAL THOUGHTSI was excited to hear that the 18 and24MHz bands have been released to UKamateurs - albeit for low -power CWoperation. With the CW generator module,R&EW transceiver owners will have a greatheadstart over the non- synthesised rig -owners. Indeed, it is not difficult to takethe mixer output up to ten watts - so whatare you waiting for?

Next month I hope to bring together thethree modules described so far, and presentthe Mark I Controller Board. Thisperforms all the functions necessary tocombine the modules - into a HF exciter.It will contain all necessary DC supplies,changeover modes, controltransmit/receive (via push -to -talk), offeradjustable semi -break-in for CW andcontrol receiver muting and aerial change-over. I will then describe how to make allthe inter -connections to the receivers, andsummarise any modifications.

Your ReactionsExcellent - will make oneInteresting - might make oneSeen BetterComments

Circle No.

91011

12


S.E.M. Tel: MAROWN (0624) 851277UNION MILLS, ISLE OF MAN

SENTINEL 2M LINEAR POWER/PRE-AMPLIFIERS.Now feature either POWER AMP alone or PRE -AMP alone or both POWER ANDPRE -AMP or STRAIGHT THROU when OFF. Plus a pre -amp GAIN control from 0 to20dB N.F. around 1dB with a neutralised strip line DUAL GATE MOSFET.Ultra I_INEAR for all modes and R.F. or P.T.T. switched. 13 8V nominal supply. S0239sockets.Three Models:

1 SENTINEL 36 Twelve times power gain. 3W IN 35W OUT. 4 amps. Max. drive 5W.21. front panel, deep. 02.50 Ex stock.

2 SENTINEL 50 Five times power gain. lOW IN SOW OUT. Max. drive 16W 6 amps.Same size as the Sentinel 35. E74.50 Ex stock.

3 SENTINEL 100 Ten times power gain. 10vV IN 100W OUT. Max drive 16W. Size:x 4" front panel, 34" deep. 12 amps E100 Ex stock.

All available less pre -amp for E8.00 less

POWER SUPPLIES for our linears 6 amp 04. 12 amp £49.SENTINEL AUTO 2 METRE or 4 METRE PRE -AMPLIFIERAround 1dB N.F. and 20dB gain, (gain control adjusts down to unity). 400W P.E.P.through power rating. Use on any mode. 12V 25mA, Sizes: 14" x 21" x 4". 08.00' Exstock.

PA5 Same specification as the Auto including 240V P S.0

SENTINEL STANDARD PRE-AMPLFIER. £15 Ex stock.PA3. 1 cubic inch p c.b. to fit inside your equipment. £10 Ex stock.70cm versions of these (except PA51 £4.00 extra. All ex stock.

S.E.M. TRANZMATCHThe most VERSATILE Ant. Matching system. Will match from 15-5000 Ohms BAL-ANCED or UNBALANCED at up to lkW. Link coupled balun means no connection tothe equipment which can cure TV1 both ways. 50239 and 4mm connectors forco -ax or wire feed. 160-10 metres TRANSMATCH 09.60 Ex stock. 80-10 metres£62.60. EZITUNE built in for £19.50 extra. (See below for details of EZITUNE). All exstock

3 WAY ANTENNA SWITCH 1Kw S0239s 05 00.

S.E.M. 2 METRE rRANZMATCH. 5;" x 2". 3" deep. S0239s £24.90 Ex stock.

S.E.M. EZITUNEClean up the bands by tuning up without transmitting.Connects in aerial lead, produces S9 (1 - 170MHz) noise in receiver. Adjust A.T.U.or aerial fur minimum noise You have now put an exact 50 Ohms into your trans-ceiver Fully protected, you can transmit through it, save your P.A. and stop ORM125.00' Ex stock.

S.E.M. AUDIO MULTWILTER. To improve ANY receiver on ANY mode. The mostversatile fitter available. Gives "passband" tuning, "variable selectivity" and one ortwo notches. Switched Hi -pass, Lo -pass, peak or notch. Selectivity from 2.5KHz to20Hz. Tunable from 2.5KHz to 250Hz. PLUS another notch available in any of thefour switch positions which covers 10KHz to 100Hz 12V supply. Sizes: 6" 24' frontpanel, 34' deep. all for only E57.00 Ex stock.SENTINEL AUTO H.F. 1NIDEBAND PRE -AMPLIFIER 2-40MHz, 15dB gain. Straightthrough when OFF 9-12V.21' 1t 3'.200W through power. E19.55 Ex stock.SENTINEL STANDARD H.F.PRE-AMPLIFIER. No R.F. switching 02.62' Ex stock.S.E.M. IAMBIC KEYERThe ultimate auto keyer using the CURTIS custom LSICMOS chip. Tune andsidetone Switching 04.50 Ex stock. Twin paddle touch key. £12.50 Ex stock.

AN IMPORTANT NEW RECEIVER BREAKTHROUGHFollowing our development of an rx for commercial watchkeeping. we areproducing this for the amateur.Atthough this is a very small and economically priced unit, it is NOT a "toy", as thespec below shows. It is ideal as a first receiver for the beginner or an additional onefor the shack or pocket.

IF Breakthrough, NONE; IMAGE, NONE; Selectivity 2KHz; 'OUTPUT, 1W.'Sensitivity .1 uV; '9-12V, 20mA quiescent; '24" 6" 3"; 'OVERLOAD. Wantedsig. 30 uV, UNWANTED, 100 MV. 50KHz away. No degredation, 'Case: Ca. platedsteel. Black Al. cover; Freq., 3.5-3.8MHz (80 metres); 'Modes SSB/CW.Since nothing like this has appeared before, you may be a little sceptical, (especiallywhen you get to the price). So if you are not delighted or amazed with itsperformance, we will refund your money in full if it is returned within 14 days.PRICE: 09.00.

12 MONTHS COMPLETE GUARANTEE INCLUDING ALL TRANSISTORS.

Prices include VAT and delivery C W 0 or phone your credit card number for same day serviceMeans Belling Lee sockets. add El 90 for S0239s or BNC sockets Ring or write for moreinformation Place orders or request information on our Ansaphone at cheap rate times


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Prices: CS1 (As 101) £110 pr. inc. VAT, plus carr./ins. 5.50CS1A(simplified LS3/5A1 £103 pr. inc. VAT, plus carr./ins. £ 5.50CS3 (as 103.2) £129 pr. inc. VAT, plus cam/ins. £10.00CS5 (as Carlton II) £192 pr. inc. VAT, plus carr./ins. £15.00CS7 las Cantata) £250 pr. inc. VAT, plus carr./ins. £18.00

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99PS40. Allen HexSocket S/driver

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166 for further detailsDECEMBER 1982 43

REWTEL UPDATE

Rewtel has been in operation for a couple of months. Roland Perry assesses the currentstate of play and looks at some of the features to be added to the service in the nearfuture.

REWTEL has now been up and running for a few months,including a period at the PCW show (see last month's R&EW).Many suggestions have been received from intrepid users of thesystem, most of which have been incorporated into the softwarewhich provides the service. Our energies are now fully occupiedextending the range of information available, rather than tinkeringwith the day-to-day operation of the service. Much of the newinformation being made available is restricted to subscriptionholders -so why not become a subscriber and help us to extend theservice even further.

A major advance in information access has been achieved byusing every word on a page as a keyword. To retrieve a page, byusing keywords, the operator should specify enough words touniquely identify the information required. The more words usedin the search the longer the search will take, but if sufficiently'unusual' words are used, then the search will be of manageableproportions. Should the words supplied indicate more than onepage, then the various page titles available will be displayed. Facedwith a selection of titles a secondary access method becomesapparent. Each page has a symbolic page number (eg *6667) anddirect access to that page can be acheived simply by typing itsnumber; either after the normal REWTEL prompt or at thecontinue search prompt.

Everything typed into the computer is logged (big brother iswatching you !) and we can therefore observe the way in whichusers operate REWTEL. We see that very little use is made of thekeyword editing facilities, maybe through lack of understanding,so here is a brief repetition of the rules. The last line of keywordsused is remembered and can be added to or subtracted from byusing a + or - as the first character of the next line typed at theprompt. The computer will then display the edited keywords. Toinititate a search, using the edited keywords, type a single / as thenext input line (followed by return of course). The addition featureis the most useful, particularly when a set of keywords results inonly a few titles or perhaps a `PAGE1"PAGE2' combination.To avoid having to subtract keyword(s) immediately after addingthem they should be typed on a line with a / as the first character.This initiates a single search using the new keywords added to theexisting ones.

WHAT IS THERE ON REWTELInformation about new products is available to all users and isidentified by the keyword 'UPDATE'. These pages are basicallyan overflow from the new products pages in R&EW. Book reviews

and further coverage of magazine projects are available togetherwith corrections of mistakes and cumulative indexing.

REWTEL BULLETIN BOARDThe 'Chalk' facility allows the REWTEL user to leave bulletinsfor other users and for the system operator. Messages to theoperator requiring a reply will usually result in a bulletin from theoperator. Access to all the messages is gained by the same keywordsearching facilities as are available for UPDATE pages. Thekeyword BULLETIN will concentrate the search to bulletin boardpages only and it is usual to expect the names of both the senderand audience somewhere in the bulletin. All the bulletins are editiedand corrected before being placed on the system so minor slip-upswhen inputting are not disasterous. To send a message use thekeyword 'CHALK'.

WORLD OF RADIO AND ELECTRONICSIn conjunction with Ambit International the contents of the Wordof Radio and Electronics catalogue is available for inspection. Partscan be identified by the use of keywords (suggestions on each pageof WRE), descriptions, Ambit part numbers and even an additionalfacility of cross-references with RS and Farnell part numbers.

The pages containing book abstracts are also keyed by thekeyword

`BOOKTEL' and will be extended beyond the contents of WREas more titles are added.SUBSCRIPTION SERVICESScreen Formatting. The standard REWTEL page is 16 lines of 64characters, although the last line is not completely sent to avoidlosing the first line of the page on a 16 line scrolling VDU.REWTEL waits until a return is typed before continuing to thenext prompt. Subscribers may describe to us a smaller screen format(eg 63 characters a line) to avoid rollover problems. FurtherInformation. Another facility available to subscribers is theopportunity to request further information arrising from UPDATEpages and any other pages that may indicate that there is more(paper) that could be sent. This is in addition to accepting feedbackfrom the R&EW service card via REWTEL. Use the keyword`BINGO'. REWSHOP (Components, kits and books). Subscriberscan benefit from the ability to place orders in the REWSHOPobtaining instant feedback of the stock availablity and any pricechanges. A direct link to the invoicing system will give such anorder high priority. This facility is entered by using the keyword`SHOP'.

REWTEL SUBSCRIPTION FORM

NAME:ADDRESS:

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THE BBC MICRO AS AN RS232 TERMINAL

Based on a program supplied by Andrew Holt.

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Figure 2: The BBC micro's RS232 interface and rear panel connection

CTS DATA OUT

BBC MICRO

DB25 CONNECTOR

Figure 3: Connectionsto the modular

technology modem.

The model B BBC MICRO alreadycontains all of the hardware required toturn it into a very respectable RS232terminal emulator.

This article presents all the informationrequired to enable the conversion to beundertaken and consists of a shortprogram, plus some wiring work.

THE SOFTWAREThe program listing is given in Fig. 1, andwill turn a BBC Micro into a full or halfduplex 300 Baud terminal, with a displayof 25 lines of 80 characters.

The program listing should be typed inas shown and is set up to run withREWTEL or most other telephonedatabases. The software is capable ofgenerating the full range of ACSIIcharacters including shift and controlversions.

If a parallel printer is available thenfunctions keys 1 and 2 will stop and startcopying data to the printer. The break keyis re -programmed to automatically restorethe program if required, and function key9 will re -RUN it.

The program is quite straightforwarddue to the sophistication of the BBCmicro's operating system.

If the flag ECHO% is false then the'terminal' is in full duplex mode. (ieCharacters typed on the keyboard will besent directly to the remote -end withoutbeing displayed on the screen. They willonly be displayed if they are echoed by theremote end. This is the mode in which mostsystems operate, alternatavely if the flagEHCO% is set TRUE then the terminal willbe in half duplex, and characters typed onthe keyboard will be locally echoed on thescreen.

Having typed the program in as shownwith ECHO% set to false type RUN, thescreen format should change to 25 lines ofCYAN, with interspersed black rules.

Typing characters on the keyboardshould have no effect on the display. Nowshort together the data in and data outfrom the BBC micro. (See Fig.2). Thissimulates the remote end echoingcharacters and keyborad strokes shouldcause the corresponding character toappear on the screen.

Once all is well then the BBC micro canbe connected to a suitable MODEM, Fig.3 shows the method of connection toMODULAR TECHNOLODGYacoustically coupled modem. Theconnections required for other types ofmodem should be fairly self evident fromthe above description.

DECEMBER 1982 45

10 REM TERMINAL PROGRAM FOR BBC COMPUTER20 REM (C) 1982 BY ANDREW D. HOLT21 REM AND R&EW28 REM ECHO% indicates whether characters sent are to be echoed30 ECHOS=FALSE40 CHFLAG=FALSE48 REM let print receive line feeds50 *FX 6,054 REM55 REM set up some useful function keys56 REM "0" for 'break'60 *KEY 0 wHIA"70 *KEY 10 "OLDIM*FX 6,0IMLISTIM"75 REM "1" to start printer80 *KEY 1 "1[18"85 REM "2" to stop printer90 *KEY 2 "MC"95 REM "3" to send 'escape'100 *KEY 3 "Ulf"110 *KEY 9 "RUNIM"115 REM compile assembler routines120 PROCCOMPILE125 REM 25 lines of 80 columns130 MODE 3135REM switch off Escape (o/s version 0.1 only)140?&226=&FF@z145 REM set colours (black on cyan) for best readability150 VDU19,1,0,0,0,0,19,0,6,0,0,0,12152 REM mode% is used to set transmission mode -153 REM 2 = 7 bit even parity 2 stop bits154 REM 10 = 7 bit even parity 1 stop bit155 REM 18 = 8 bit no parity 2 stop bits156 REM 22 = 8 bit no parity 1 stop bit160 mode%=10165 REM reset acia170 ?&FE08=3:?&FE08=mode%175 REM set speeds (300 baud)180 *FX 8,3190 *FX 7,3195 REM main loop starts here200 STA%=?&FE08:IF 1 AND STA% THEN 270220 CH=INKEY(0)230 IF CH= -1 THEN 200240 PROCSENDCH(CH)250 GOTO 200260 REM CGET is an assembler routine to get a character262 REM and display it if it is 'safe'270 CALL CGET280 GOTO 200375 REM this is a procedure to send a 'break'380 DEF PROCSENDBK390 LOCAL X400 X=TIME410 7&FE08=mode% OR &60420 REPEAT UNTIL TIME > X+5430 ?&FE08=mode%440 ENDPROC445 REM procedure to decide what to do with keyboard character450 DEF PROCSENDCH(CH)460 IF CHFLAG THEN PROCESCAPED(CH):ENDPROC465 REM 'Escape' is used as a flag470 CHFLAG = CH=&1B:IF CHFLAG THEN ENDPROC480 A%=CH:CALL CPUT%490 IF ECHO% THEN PRINT CHR$(CH);500 ENDPROC505 REM Esc Ctrl A for 'Break'506 REM Esc CTr1 B(C) for printer on(off)510 DEF PROCESCAPED (CH)520 CHFLAG=FALSE530 IF CH=1 THEN PROCSENDBK:ENDPROC540 IF CH=2 OR CH=3 THEN VDU CH:ENDPROC550 ?&FE09=CH560 ENDPROC570 DEFPROCCOMPILE580 DIM CPUT%100:P%=CPUT%:[OPT 2:STA &FE09:RTE:]590 ITC=P%:PTC=P%600 CGET=P%:OSWRCH=&FFEE610 FOR X%=0 TO 1620 P%=CGET630 [OPT 2:LDA &FE09:AND #&7F:BEQ ITC640 CMPIII0F:BEQ ITC:CMP t&1F:BPL PTC650 CMP #14:BPL ITC:CMP 47:BMI ITC660 .PTC JSR OSWRCH:.ITC RTS:]670 NEXT X%680 ENDPROC

Figure 1: Software routine to convert the BBCmicro into a full or half duplex 300 Baudterminal.


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DECEMBER 1982 47

WHILST MANY READERS of R&EW will be familiar with thegeneral principles behind the operation of a colour TV set, thesystems within a colour TV camera are less likely to be understood.It may seem logical to suppose that a camera's circuits will be ratherlike a TV's, but in reverse - this, however, is NOT the case.

An article such as this, is not the place to describe the basiccharacteristics of a TV signal. So, it will be assumed that readersare familiar with the general nature of a TV signal with its lineand frame sycs, luminance and chroma subcarrier signals.

IN THE BEGINNINGFollowing the general principle that it's better to 'begin at thebeginning', rather than any where else, the first requirement ofa camera is that light (from the object to be 'filmed') is broughtto focus on the faceplate of the camera's vidicon tube. We'll notdelve too deeply into the optics of a multi -element lens system,but merely point out that the quality of the final video output (fromthe camera) can obviously be no better than the image formed bythe lens. That is why the lens system, in any camera, is one of themost important elements and often one of the most costly.

When selecting a camera, make sure that the lens features thezoom range that you will require and that the maximum apertureis as large as possible this latter point being of particular importanceif a lot of indoor use (low light levels) is anticipated. The general'quality' of a lens will be more difficult to assess, but many cameras

INSIDE COLOMichael Graham looks at came

use lens systems from companies such as Canon. Such arecognisable name on a lens is a reasonable assurance of quality.

LIGHT TO ELECTRONSThe central part of any camera (and in particular the FergusonVideostar 3V20 which will be examined first ) is the pick-uptube. In the 3V20 this is described as a '2/3" electrostaticfocus/electromagnetic deflection, unipotential focusing typevidicon tube, having a colour separation stripe filter attached infront of the photo conductive film of the vidicon target'. Quitea mouthful, but reference to Fig 1 and an orderly examination ofthe translation of the image formed (on the tube's faceplate)to a


UR TELEVISION CAMERASra circuitry from the vidicon to the final encoded video signal

modulated beam current, should make things clear - we hope!The tube face is scanned from bottom left to top right by an

electron beam, emitted by the vidicon's cathode. This process israther like a reverse CRT tube; scanning being a back-to-frontversion of that encountered in a TV set (to cope with the fact thatthe image formed by the lens is upside down). The electron beam,instead of being modulated by a video signal to cause variationsin a phosphor on the tube face, has its current varied by theinstantaneous level of incident light at any point on the tube'sphotoconductive layer. Figure 2 shows the make-up of the tube'sface plate, being a slice through the various layers (we'll come tothe stripe filter in a moment), while Fig. 3 shows the target areafrom a head-on viewpoint.

The electron beam is deflected and focussed by a combinationof electromagnetic and electrostatic systems. After leaving thecathode, the electrons are accelerated by electrode G2 - analignment magnet between the beam control electrodes, GI andG2, ensures that the electron beam is equidistant from (and parallelto) the sides of the tube.

The beam then passes through an 'electronic lens' formed byelectrodes G3, G4 and G5 - these ensure that the beam, when itstrikes the face plate, is consistently at right angles to the target'ssurface. This is important if an adequate resolution is to bemaintained at both central and peripheral areas of the target. Thebeam is then deflected by an external magnetic field produced bya set of scan coils.

Thus far, the description of the vidicon could apply to amonochrome camera - it is the inclusion of the colour stripe filterat the vidicon's surface that marks the difference between colourand mono systems.

GAINING ONE'S STRIPESHarking back to a colour CRT tube, it will be remembered thatsuch tubes use an additive mixing of three colours, Red, Greenand Blue to produce any hue/saturation of colour that is required.A colour camera must 'analyse' the incident light falling on thevidicon and break it down into these three colours. The stripe filtermay thus be expected to pass only red, green or blue light at variouspoints across the tube s surface.

Figure 4 reveals that this is not the case - the various elementsof the filter passing green, cyan and white. The reason for thischoice of 'stripe characteristics' becomes clearer if the constituentcolours of each stripe are examined. The green stripe obviouslycannot be broken down any further, but the cyan stripe, when

DECEMBER 198249

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broken down passes both Blue and Green but No red (the whitestripe passes all three colours).

Thus a repetitive sequence of Green, Green + Blue, and Green+ Blue + Red colour signals results, as the beam scans acrossthe surface of the vidicon tube.

The mask area at the bottom of the vidicon (Fig 3), is used toadjust to the dark current of the system.Figure 5 shows that a step -

like signal is the result of incident white light upon the face of thepick-up tube. The waveform is the result of B and R signals beingmodulated onto a G carrier.

The 'frequency' of modulation will quite clearly depend uponthe pitch of the stripes in the filter - the output being a combinationof the tri-colour mixed signals (the DC component) and the HFmodulation signal (AC components). Without going into themathematics involved, the HF signal will be a combination of the'fundamental stripe frequency' (fl) and its second harmonic. The3V20 uses a fundamental frequency of ft =4.1 MHz and thusf2= 8.2 MHz.

INTO ELECTRONICSThe block diagram of Fig. 6 shows that the electronics of thecamera can be broken down into a number of discrete blocks. Thevidicon's output signal is fed to a multiple -signal colour processingcircuit (pre -amplifier, dark current compensation, peakcompensation, and AGC circuits), a luminance -signal processor,a colour demodulator, matrix and auto -white circuits.

The details of the colour multiple and luminance signal circuits

are beyond the scope of this article (their tasks being to providean output signal of adequate contrast and stable black- level aswell as providing protection to avoid damage to the vidicon tube).

The colour demodulation circuit works on the phase (notamplitude) of the stripe frequency 2nd harmonic to separate theB and R signals. Use of the 2nd harmonic frequency overcomesproblems with the small physical size of the vidicon target area.

The G signal can be derived from the Y (luminance) signal andthe demodulated B and R signal. The R, G and B signals are takento a matrix circuit that produces PAL type R -Y and Y -B colourdifference signals.

ARE THE WHITES RIGHT?Any colour camera must take account of the fact that the 'colour'of a subject will depend upon the 'colour temperature' of the lightilluminating that subject.

Table one shows there is a wide variation in colour temperature- not only between indoor and outdoor light, but between the'colour' of daylight - whether the day is overcast or bright.

Most colour cameras include an optical correction filter tocompensate for the extremes of colour temerature revealed in thechart. A camera would usually be balanced at around the 3000 °Kmark (indoor light) with a filter 'shifting' the neutral point toaround 7000 °K.The filter is used for outdoor correction as therewill obviously be some light absorbed. Under indoor conditions,light levels are usually lower and a filter may make the difference


Colour firma/figure ofnatural tight 1°K)

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SCAN ANDUT CIRCUITRY

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Table one: All light has a 'colour temperature'.It varies a great deal as this table shows.

Figure 8: A simplifier outline of a Trinicon tubetogether with its equivalent circuit.

between an acceptable or not acceptable level of light.Finer adjustments within the coarse range, defined by the filter,

are made by varying the relative levels of the B and R signals. Inmost cameras this adjustment is made manually, but the 3V20features an interesting 'auto white' facility.

AUTOMATICALLY RIGHTThe auto -white circuit is designed around the fact that while'shooting' a black and white scene (under 'standard' light), thecolour difference signals (R -Y and B -Y) will have zero amplitude.Under anything other than standard light,these signals will havesome non -zero component.

When the auto -white circuit is activated, the R -Y and B -Y signalsare integrated and compared with a reference voltage (near to zero,but in practice differing from zero by a small amount). These'difference' voltages are digitised and stored in two up/downcounters. The outputs from these counters are converted back toan analogue signal and fed to a pair of electronic attenuators inthe R and B signal paths - compensating for any non-standardlighting conditions.

HOUSEKEEPINGThe various other functions to be performed by the camera aresync generation, encoding and power supply regulation.

The generation of all sync, control and colour sub -carriers is

usually achieved via the HD 44007 IC, a CMOS device that hascornered the market for this sort of function. As for the deflectioncircuitry it is fairly straightforward as are the power supply sections.

The encoder circuit's job is to bring together all the various sync,chroma, luminance and blanking signals to produce a PAL spec,composite video output signal. Figure 9 shows that once again thistask is largely taken care of by ICs.

SONY'S SYSTEMThe Trinicon system developed by Sony uses a different methodfor extracting the chroma information from the image formed onthe vidicon's faceplate. In a Trinicon camera, the stripe filterconsists of Red, Green and Blue stripes, the chroma informationis encoded by means of an Index Electrode.

In order to understand the Index Electrode's operation it willbe necessary to take a closer look at the way in which a vidicontube converts the light incident on its face plate into a modulatedbeam current.

Figure 8 shows a simplified outline of a vidicon tube togetherwith its equivalent circuit considering just one element of thephotoconductive layer, which may be thought of as a resistance(whose value varies according to the amount of incident light fallingupon it) in parallel with a small capacitance, as the scanning electronbeam passes the 'beam side of the plate assumes the cathode'spotential (oV) while the 'signal plate' sides is at target voltage (r).Any light incident on the tube's face will have the effect ofdischarging the capacitance as the value of the parallel resistance

DECEMBER 198251

Figure 9: The PAL encoder of the 3V20 camera is largely based on IC devices.

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is reduced. The next time the beam scans the particular element,it will restore the plates initial conditions, the charge required todo so being supplied by an increase in nominal beam current.

Output current at any instant in time can conveniently beexpressed as

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Where is the time that the beam is on a 'picture element'.Figure 10 shows the position of the indexing electrodes with

respect to the photo conductive layer. The indexing electrodes area series of transparent stripes parallel to the 'colour' stripes,alternate stripes being connected to one of two bus bars. Applyinga voltage to an index stripe will raise (or lower) the signal platevoltage along the stripe and the expression for the instantaneousbeam current for a picture element along its surface will be amodified version of the one shown above; namely

It = A C(AVs + AVD)

At

where D is the voltage applied to the indexing electrode.The voltage applied to the indexing electrodes is inverted at the

end of each horizontal scanning line. Reference to the blockdiagram of Fig. 11 and the timing waveforms of Fig. 12 will showhow the Trinicon's combination of Red, Green and Blue stripesplus the indexing electrode achieves the separation of the threecolour signals.

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Figure 12: A block diagram of a Trinicon camera.

The first line of Fig. 12 shows the output of just the Green stripewhile the next two lines show the potentials applied to the indexingelectrodes.

Adding the indexing offset voltages to the Green output givesthe waveforms shown on the next two lines.

The significance of the block marked one line delay in the blockdiagram now becomes apparent by adding the chroma and indexsignal from any line together with delayed signal from the previousline produces a signal that is twice the output of the primary chromasignal. Subtracting the same two signals produces an output thatis twice the index signal.

The indexing signal and chroma signal, when applied to asynchronous detector produce the familiar R -Y and B -Y signalsready for PAL encoding.

The rest of the trinicon system, white balance, scanning, powersupplies etc, follows the pattern outlined for the 3V20.

Another point of note in Sony cameras is the optical low passfilter that is placed in front of the vidicon tube. This removes anyhigh frequency component of the scene being videoed, these highfrequency signals would cause interference in the colour encodingprocess if passed to the vidicon tube.

The filter is of a double refraction type which, in effect, slightlyblurs the image, forming a double image shifted half the pitch ofan individual filter stripe.

The Sony system, using the indexing electrode and delay systemis said to offer superior results to encoding systems such as theone adopted by the 3V20. Certainly the quality of results producedby Sony cameras is very good with excellent definition and colour

rendition.

OVERVIEWMany cameras feature an elctronic viewfinder - these followconventional TV practice, although in miniature, and have no RFcircuits to worry about. So, that's about it, a brief look at thevarious sections of a typical colour TV camera, devices that packa great deal of electronics into a small light -weight package.


NI -CADCHARGER

Adrian Barnes presents a novel design for charging your 'run-down' NiCads.

THE R&EW NI -CAD CHARGER enablesa wide range of Ni-Cads to be given aquick, safe, charge. The circuit monitorsthe batteries on charge and will shut downif a fault condition is detected.

Our circuit allows the user to decideultimately what charge current is employed,and uses two VFET's (in parallel) as aconstant current source. Four cells may becharged at a time using battery holders, sothey're effectively in series. It should benoted that these must be single cells, withthe vented tops, such as supplied by Ever -Ready, who also helped with informationfor this article.

Since the cells are in series, they shouldall be in approximately the same state ofcharge - being used usually in fours, thisshould not present a great problem. If somecells do overcharge a little, they will onlydissipate the extra energy as heat - howeverprolonged overcharge will damage the cell.To this end, a monitor point (in the battery)is taken between the third and fourth cellsfrom earth. If the cells are in a vastlydifferent state of charge, or are internallyshort- circuited, the voltage at this pointwill be detected and the unit will cease tocharge.

When the overall voltage on the batteryreaches a certain level the charge changesto a trickle. This is taken as a 'sample',about every thirty seconds, so that thebattery has to reach a constant level ratherthan reverting to trickle charge at aspurious peak. Four arbitrary samples are

taken, so the counter is reset if the batteryis charged - to ensure this reset (whenchanging batteries), touch the test point tothe negative of the battery connector,turning Q6 and 7 on and Q5 off.

CONSTRUCTIONAs usual start with the IC sockets, links andresistors. The transformer and C3 shouldbe left until last - please remember toinsulate all the mains connections. Ifdesired, the fuse can be mounted remotely,with indicator LEDs to show the state ofthe relays - that is, charge/sample,fast/trickle and fault.

A PP3 type connector can be used forthe output and a small piece of tin plate actsas the test point probe. The PCB issupported by the transformer and theheatsink should be bolted on to the outsideof the case.

SETTING UPSet RV1,2 and 5 to midway, and RV4 fullyclockwise to turn Q5 on. Apply a potentialto the test point of about 4.8-5V, about thenegative end of the battery and adjust RV3so that RLA2 switches off if the voltageincreases above this. Then set RV4 so thatthe relay switches off if the test point goesbelow 3-3.2V, above the negative end of thebattery.

Adjust RV2 so that the supply voltageacross 1C4 is 5V. Then, finally, adjust RV5so that pin 10 of IC4 goes high when the

top of RV5 is at 6.1V.RV I sets the charge rate, which depends

on which cells are being charged. Cells willbe damaged if the charge rate is muchgreater than Cr!, (the current necessary tocharge the cells in one hour) - the life ofthe cells being inversely proportional to thecurrent.

As a guide, if the current is set between1.2 and 1.5 amps, AA cells will charge inabout an hour and larger cells will takelonger.

IIIIIIIiililliiiIIIIii

Immumawizrm.mumaimmommmmommooligliommommoOhMMOMM

IMMAIMOIMEI:1:1111111:119111

sag

414

2

IIIIIIIMUMMEMMEll NMMININIMMI1111EN11111111

MEME111110"'"°41111rtlammillliMEN NMIFAINEXIMM1111 s"EOVERCHARGE

0 1 3 4 5 6 8 9 ,0 12 13 14 15

CHARGE TIME (HOURS)

Figure 1. Charge/discharge curves fortypical NiCad cells

DECEMBER 1982 53

NI -CAD CHARGER

O00OO

R&EW

AutomaticNi-CadCharger

Figure 2: The Ni-Cad charger PCB

T1

R16

C2 R15

7

R4

0R10

Q2CLD VR5

R2 :)LINK

D5 ED

Q5R8

R9 .4-1.Q6 4='

R3

WIRE LINKS RUN FROM PAD B TO PAD BON THE UNDERSIDE OF THE BOARD,LIKEWISE WITH PADS MARKED C.

TOFUSE

.11411M110

R17

4R5

Q7 VR3

D2

CeVR4

BR1

D3471}

RLA3

VR2ID

Q3

R121C1

Figure 3: Component Overlay


PROJECT

NOTES IC1 is 4011IC2 & 3 an 4040IC4 4040801 & 2 11,1. VN66AF0.14.5 & 6 4nk BC23907 is BC309

r

Vdd,c2 011

MR Vu 0711 8 113

RLA312VKVIT B

R7 1k8 RV3226

Figure 4: The Ni-Cad chargercircuit diagram.

CIRCUIT DESCRIPTIONA normal transformer -rectifier circuit,smoothed by C3, supplies the circuit. Thecurrent is controlled, on the negative rail,by two VFET's. VN66AF's are used here,because they are fairly cheap and easy tomount onto heatsinks - two are used to givemore current capability. R9 and R11 set thetrickle current and RV I the charge current,which is switched by RLA1.

RLA1 is controlled by IC4 and Q3. Apotential divider, RV5, lowers the voltagefrom the battery being sampled and Q3 andD4 provide a switch at a given voltage. Thesupply voltage on IC4 is adjusted, alongwith the collector voltage on Q3, in orderto lower the triggering threshold of IC4.R12 pulls the input down, when Q3 isturned off, and Cl decouples it. The Q2output of IC4 (pin 6) is used, so that Q4changes state every fourth time that Q3does.

The sampling is controlled by IC1,2 and3. ICI is set up as an oscillator; IC2 dividesthis down and gives out approximately 30second pulses at Q11. This is fed to theclock input of IC3. Master reset on IC3 isconnected to Q7 of IC2, thus a high at theoutput Q1 (IC3) is only obtained whenthere is a negative -going edge on Q11 (IC2)and Q7 (IC2) is low - since MR is activehigh. This produces a pulse, which via Q6,turns RLA3 on once every thirty seconds,for about a second.

The final part of the circuit is the faultsensor. RLA2 is normally held on by Q5,7

COMPONENTS LIST

ResistorsR1,2,3R4R5R6,7,8,9R10R11R12,13,14R15R16R17

CapacitorsC1C2

C3

SemiconductorsBR1Q1,2Q3,4,5,6Q7,8

100R75R220R1K86K88K210K150K3M333K

10n Ceramic150nPolycarbonate4700u 35V Radialelectrolytic

PW02VN66AFBC239BC309

D1,2,3D4D5D6D7IC1IC2,3,4

PresetsRV1RV2,5RV3,4

IN40015V6 zener 400mW12V zener 400mW6V8 zener 400mW15V zener 400mW40114040

10K 6mm22K cermet 6mm22K 10mm

MiscellaneousT1 C5006 transformerChassis fuse holer +3.15A fuse.RLA1RLA2RLA3

12v kuit A6V kuit B12V kuit B

Heatsink type E1.58 Ambit 21-08030Two 6BA 3/8" round head slotted two6BA plain washers.8pc half pinsPCBDil set.

and 8. Q8 lowers the threshold at which Q7turns off, which is adjustable with RV3.Similarly, if the voltage is too low at thetest point, Q5 will turn off. R & EW

Your ReactionsExcellent will make oneInteresting - might make oneSeen BetterComments

Circle No.

29303132

DECEMBER 1982 55

A DIGITAL RECORDING SYSTEM

What constitutes a 'perfect' audiorecording? Briefly, it must be a systemwhich introduces no changes whatever ina high quality signal being recorded andplayed back. Using the finest qualitymicrophones it would be a very finerecording system that would introduce nochanges to the sound quality possible fromthe mics. Up to now, with conventionalanalogue tape recording, the changes canbe remarkably small, as a result of themany individual improvements made tothese machines.

Ignoring cassette recorders for themoment, at a cost, analogue reel to reeltape recorders can have a frequency rangeof 20Hz to 20kHz (but with irregularitesat the low frequency end and compressionof the dynamic range of high frequenciesat high levels), low intrinsic noise (but stillworse than the best mics), low modulationnoise (but still a noticeable clouding of highlevel high frequency signals due to noiseproduced by signal modulation), low printthrough (but still a problem on, saytrumpets, with consequent audible pre orpost echo), generally inaudible pitchchanges (wow and flutter, depending ondeck transport design and maintenance),ability to produce a few multigenerationcopies (with careful machine alignment andlevel control, good 2nd generation copiesare possible - progressively deterioratingwith more than this). All the parameters area magnitude worse with the compact

M.G. Skeet looks at Sony's PCM Flanalogue to digital convertor that

makes use of a video recorder404444.1 to provide a digital audio

recording system.

cassette of course, but surprisingly goodresults can be achieved on a good tape anda machine aligned for it.

It has taken a radical change in signalprocessing to remove the constraintsimposed even by the best conventionalaudio recorders. This change involvesconverting the audio waveform into a PCM(Pulse Code Modulation) or Digital signal,then recording the digital stream of pulsesand on playback re-creating the originalaudio waveform. The system allows wideband frequency ranges right up to peaklevels with intrinsic noise, modulation noiseand print through, better than 90dB down(conventional machines might manage70dB with respected noise reductionsystems) and unmeasurable wow andflutter. Add to this the possibility ofmultigeneration copying and theimportance of Digital audio recording isevident, doing justice to the use of decentmicrophones or recording from anycommercial digital sources that will appearbefore long (the Compact Disc?)

NOW AVAILABLEThis home quality revolution is availablenow, courtesy Sony and the PCM F1Analogue to Digital convertor which usesany Betamax or VHS video recorder as thestorage medium. Why a video recorder?Simply to get the bandwidth needed for themillions of pulses generated per second inthe A to D conversion.

Interestingly, mentioning 'home' use isnot entirely correct, for a number ofprofessional recordists have taken up its usein lieu of their previous digital equipments(at 1/10 the cost!)

PCM & VIDEO PACKAGEThe PCM F1 A to D convertor acceptsnormal domestic 'line' inputs or lowimpedance (200 to 600R) microphones. Thelink to the video recorder is rated at 1 voltpeak to peak. The PCM Fl unit is suppliedwith a mains power box (AC700) but canbe run on a NP1 nicad pack or for thatmatter a car/boat battery. The modelbrought into the UK and Europe is ofcourse a PAL/SECAM version to couplecorrectly with PAL or SECAM videorecorders.

In the October 1982 issue of R&EW welooked at Sony's portable SL F I videorecorder. This and its mains adaptor ACFl are an ideal physical match for the PCMFl. Together they are shown in a proposed'hold it all together' case from WhitetowerRecords. It enables the package to be easilycarted around to recording sessions. Athird matching unit, TT F1, programmabletuner/timer provides theTV signal sourcefor the SL F1 when used in its other rollof TV recorder. With the latter also havinga camera input, the whole system is verymuch the home audio/video recordingcentre. But to look at the audio use of thePCM F 1 .


REVIEW

270°

0°

180°

20 25 -90°B dB

- 100 Hz-- 1000 Hz--- 7000 Hz

Figure is: The theoretical pickup pattern ofan omnidirectional microphone. Note that athigh frequencies the microphone becomesincreasingly directional.

AUDIO RECORDINGQuite frankly, the only source capable ofdoing justice to the PCM F1 available atthe moment would be a pair of high qualitymicrophones! Assuming of course that theowner wishes to get out and about,recording music. The system is not in anyway stretched by recording conventionalLPs or cassettes. A decent FM tuner andaerial system would however be an idealway of collecting superb microphonematerial, by proxy from BBC radio 3'smany live concerts or their own digitalrecording. No point in recording anybroadcast disc program!

There is very little knowledge aboutconcerning microphones. The run of themill moving coil or electret capacitor micswould be useless. No, the only way is toape the professionals and use the same micsas they do! This will mean 'proper'capacitor mics from such makers as AKG,Neumann, Schoops, Sennheiser, Milab orCalrec.

If it's orchestral, choral, small ensemblesor similar 'non pop' activity, then a simplecrossed pair produces a superior stereorecording of the sound sources and theacoustic's of the venue. This latter pointis almost the most vital part as far as thewriter is concerned. One is conveying themusic and its environment. A coherent,realistic and hence satisfying illusion iscreated by coincident crossed pairs ordirectional microphones.

The alternative of spaced pairs or thejumble or multimiking fails to produce acoherent stereo in the writer's view andinterestingly the advent of phase stabledigital recorders is showing up deficienciesin the commercial recording world'smicrophone techniques.

MICROPHONE TYPESThe type of microphone one is looking forin the crossed pair field is the wide, flatfrequency response, uniformly directionalat all frequencies, type. Figure 1 shows thetheoretical polar pickup patterns of thebasic different type of mics. Uniformlydirectional responses means that similar

270°

0°

180°

_90°

Figure lb: The 'figure of eight' responsetypical of a ribbon microphone.

patterns are produced at all frequencies -many low cost direction mics have narrowhigh frequency polar pickup giving poorcentre stage definition when used as crossedpairs. Figure 2 shows a pair of 'cardioid'mics crossed at around 1100 on an easilymade stereo bar and Fig. 3 shows theconcept of crossed pair stereo coherencefrom mics to listener.

The manufacturers listed earlier allproduce a number of flat response 'proper'capacitor directional mics. Prices varyconsiderably as many offer variable polarpatterns. I must define 'proper' capacitormics as opposed to electret capacitor types.The former require polarizing by externalpower supply whereas the latter arepolarized at manufacture - the internal 1V5battery in the body simply powering theFET impedance convertor.

Most mics in the class being describedoffer balanced feeds - the powering beingby 'phantom' feeds down the signal wiresin parallel with screen return. The PCM F1is in fact unbalanced at its input and a

Figure 2: A pair of cardioid mica crossed at 110°.

270°

0°

180°

Figure lc: A cardioid's pickup pattern.

certain amount of involvement would benecessary at the input with transformers toallow phantom powered capacitors to beconnected. But there is a neat solutionprovided by the only UK microphonemanufacturer in the list, Calrec. They havea CM652D cardioid capacitor mic which isunbalanced and is powered by 50V DC onone wire and screen return. Long leads areperfectly feasible and the combination ofthese mics and the PCM F1 is easily thelowest cost way of getting an input qualityup to the recording potential. The powersupply can be made by DIY (battery or

of between £150 to £180 depending on thelead length and mic stand arrangementdecided upon. This is significantly less thanequivalent performance units from othersources or even Calrec themselves - theyhave the unique Soundfield microphonesystem at around £2000!

RECORDING WITH THE PCM FlThe metering system is quite respectableand it needs to be. Live microphone signals

DECEMBER 1982 57

A DIGITAL RECORDING SYSTEM

LEFT CHANNEL

SOUND SOURCEIBAND,ORCHESTRA etc.)

MICROPHONES ARRANGEDAS A CROSSED PAIR

RIGHT CHANNELLTV

LISTENER

have amazing dynamic range - all othersources are compressed to a remarkabledegree in comparison. In theory digitalsystems have a finite peak handlingcapability - analogue systems squash gently.When the input exceeds the quantizationrange available somthing has to happen.Interestingly the PCM F1 tolerates oddexcursions 'over' - but it is poor techniqueto drive the system that hard. There is noneed to as the 'other end' is a long 90dBdown.

Figure 3: Stereo soundfrom source to listenerusing the 'crossed pair'microphone technique.

Allowing one's recordings to generallyhover around the minus 20dB position onthe PCM Fl units metering will allow theodd climax and natural dynamic range tobe encompassed. With analogue recordingthere is undoubtedly a lot of gentle clippingand compression going on. The scaling hasan expanded area above the -20dB pointand levels anywhere in this area are safe.Unlike analogue, particularly cassette,where the HF compression effect is presentthe higher one goes.

Waveform height measured (sampled).

One channel's waveform sampledFigure 4: The first step in the digital recording process is to samplethe analogue signal.

Sharp edgesare unwanted

/ harmonics

Voltage levels switchedas required by eachsamples code.

Ideally one should set up and monitorin a separate room. Taking along a pair ofdecent speakers and an amplifier isnecessary. It is very easy to monitor off thePCM Fl. When idle or recording, the inputsignal is fed to the line output. Playing backautomatically substitutes the recording.

My favourite input arrangement isunfortunately absent on the PCM Fl.There are two separate record level controlsinstead of the ideal, ganged master andseparate pre-sets. Balanced fades andsensible peak setting is then possible.

Where to place the mics is the old agequestion. No amount of writing on thesubject substitutes for getting out andmaking mistakes! It is not easy to judge onsite just what is a satisfactory balance. Oneis out of one's normal listeningenvironment and so are the speakers, whichaffects their performance in turn.

Obtaining a balance means placing theperformers and mics so that the music isinternally balanced and the whole isbalanced against the acoustic. It's a caseof experimentation - you have to startsomewhere - so put the mic initially whereimpulse and your ears in the room suggest.The sound in the monitoring room will notbe exactly the same! It will be stereo asopposed to the natural surround sound ofthe 'studio' itself. But long critical listeningwill give one ideas for improvement. Is themic too distant or too close? Do some ofthe instruments or singers leap out or aretoo recessed? The stereo presentationshould be judged - there is no point inhaving a 20 ft wide piano or a quartet aswide as a full orchestra.

Otherchannel

1 1 11 11 11 11 1 1 1 11 1 1

101 011 0011 oo nono 1010 10 110 0 10 1 0 0 11 011

Each 'amplitude' converted into abinary code

Figure 6: The stream of digital data that represents the audio signal.

After sharp filteringby low pass filter -unwanted harmonicsremoved.

Figure 5: The sampled audio signal.

Stt

Figure 7: The audio signal is recovered after digital to analogue conversion.


REVIEW

DIGITAL PCM GLOSSARY

P('N1

Sampling

Quantizationaccuracy

Pulse Code Modulation -the use of Pulses (digits,hence digital) in a BinaryCode to quantisize theamplitude of a signalwaveform.The rate at which theamplitudes are sampled.Has to be at least twicethe highest audiofrequency required.The more bits persample, the greater thenumber of amplitude

Stereo handling

levels that can beaccurately realized.Telephone systems use 8bits (28 = 256 levels).Currently 16 bits are thenorm for high qualityaudio (216 = 65,536levels). More bits, lessnoise - theoretically 6dBbetter for eachadditional bit.Alternate sampling ofthe left and rightchannels.

Basic Bit Rate

Avoiding Wow& flutter

Calculated by thenumber of channels Xthe sampling rate X thebits per sample. (2 X44.1K X 16 =1,411,200)The signal off tape isput into a buffer storeand is read out understrict time clock controlat the 44.1KHz samplingfrequency. Thus anyspeed drifting into thestore is of noconsequence.

SOME INTERESTING TEST RESULTSThe overall excellent specification wasobviously being very well met. In fact it canbe regarded as an amplifier, rather than asa recorder as far as testing is concerned. Iam more interested in the 'practical'technical aspects so here I shall brieflyrelate some of these.

When hovering around the 20KHz

SONY PCM Fl SPECIFICATION

Quantization

SamplingFreq responseDynamic rangeTHDWow & Flutter

16 bit linear (14 bitoption!)44.1kHz (PAL/SECAM)10-20kHz ± 0.5dBMore than 90dBLess than 0.005%Not measurable

The Beta cassette on which the Fl records thePCM signal.

region it is possible to produce audible byproducts similar to those often heard inanalogue tape equipments with bias beats.This seems to be due to beats with the44.1kHz sampling rate. In practice it isinaudible as it is provoked by high level20kHz signals and there is not much of thatabout in music signals - program maskingoccurs anyway.

I like to know where I am with themetering and a system's limits. When the`over' legend is lit, that is the genuine peakpoint. On tones this is easily heard. Onsignal transients which flash the legend,limiting merely occurs with no nastyaudible effect!

On the test sample I was not all thatenamoured with the scaling accuracy. Neg20dB being minus 16 in practice withsimilar other relative errors higher up thescale. The metering shows the emphasis atHF used in signal paths - compared to my'flat' BBC type PPM there is a lot ofleaping about with audience clapping andthe transients from drum kits etc. It isessential that these things are seen to bepresent and the metering clearly showswhat is going on and should be believed.

Line inputs, signal to noise ratios are notdegraded by the record gain controlposition but on mic inputs there is a limitof around 40% if this is to be avoided.Luckily in both cases it is possible to workdown to small rotations without clippingproblems. An essential feature thisespecially where mic inputs are used. Withthe Calrec capacitors the author frequentlyuses it is possible to trim the levels in thepower supply. The PCM F1 input is notaffected by source impedance it sees.

Sometimes in playing around with reviewequipment some novel opportunitiespresent themselves. The PCM Fl was infact invited along to the Albert Hall torecord experimentally for the BBC andCalrec the last two nights of the 1982 Promseason direct from a Calrec Soundfield mic.Some spectacular single mic balances wereobtained making an interesting comparisonwith the Radio 3 broadcast possible.

SUMMING UP ON THE SONY PCM FlIf the video out and video in connectionsare linked, by-passing any recorder, it is notpossible to detect any difference inswitching the processor in or out of a highquality audio chain in ideal listeningconditions! Remember, a full A to D andD to A process is taking place. The processof recording and playing back cannotchange it - so we truly have a 'straight wire'recorder. It is sobering that it is now leftto improvements in microphones andloudspeakers (and their arrangement forAmbisonics for instance) to improve soundreproduction. The Sony Compact Discplayer uses the same LSI chip as the PCMFl and this augers well for the performanceof CD, expected next spring.

SUPPLIES AND FURTHERINFORMATION

CalrecMicrophones -

Sony PCMFl etc -

details and DIY powerunit circuit availablefrom Whitetowerrecords, 2 RocheGardens, Bletchley,Milton Keynes, MK36HR. (0908) 73969Details available fromFeldon Audio, 126 GreatPortland Street, London,WIN 5PH. (01) 580 4314

Mention RADIO & ELECTRONICS WORLDof course.

R & E W

Your Reactions Circle No.17181920

Immediately InterestingPossible applicationNot interested in this topicBad feature/space waster

DECEMBER 1982 59

iiikruda CWSRTTY COMMUNICATIONS TERMINAL

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Professional keyboard with many special functions. Real-time clock (constantly displayed).

Transmit and receive both CW (morsel and RTTY(teleprinter).

Users call sign programmed in. Receive CW speed tracking and display. Self checking facility. Char. by char. or 'page' transmission modes. Stylish two tone metal cabinet.

OTHER OPTIONAL FEATURESPrinter interface board (Centronics compatible).

On -board 40 column printer (12V). External 80 column printer (SEIKOSHA GP100A).

£381.74 ,nc carriage (Standard unit cost VAT not included)

Forget all those messy wires, the MICRODOT now offers a totallyintegrated communications system.

Write for full details to:

POLEMARK LTDLower Gower Road, Royston, Herts SG8 5EA

Tel: Royston (0763) 47874


MASTER ELECTRONICS MOW!The PRACTICAL way!

This new style course will enableanyone to have a real understandingof electronics by a modern, practicaland visual method. No previousknowledge is required, no maths, andan absolute minimum of theory.

You learn the practical way in easysteps mastering all the essentials ofyour hobby or to start or further acareer in electronics or as a self-employed servicing engineer.

All the training can be carried out inthe comfort of your own home and atyour own pace. A tutor is available towhom you can write personally at anytime, for advice or help during yourwork. A Certificate is given at the endof every course

You will do the following:Build a modern oscilloscopeRecognise and handle current electronic

componentsRead,draw and understand circuit diagranCarry out 40 experiments on basic

electronic circuits used in modernequipment

Build and use digital electronic circuitsand current solid state 'chips'

Learn how to test and service every typeof electronic device used in industry andcommerce today. Servicing of radio, T.V.Hi-Fi and microprocessor/computerequipment.

NewJob? New Career?NewHobby?Get into ElectronicsNow!FREE! Picase send your brochure without any obligation to REW/12/821

NAMEICOLC', BR(p,

ADDRESS

I am interested in.

POST NQW T0:-

Electronics''& School Reading, Berks.13G1 1BR


Compiled by Arthur C. Gee,

MOST AMATEUR radio signals in theVHF -UHF region, ie., above 20 MHz, arepropagated via the lower part of theatmosphere about 5Km above ground. Theterm 'troposphere' is applied to this regionand the chief properties of the air whichaffects these signals are the verticaldistribution of the temperature and thewater vapour content. The ionospherehowever, does occasionally give VHFpropagation, in layers of ionisation about100 Km above ground. One of these modesis 'auroral propagation' which as its namesuggests, is associated with the appearanceof displays of the aurora in the skies aroundthe earth's magnetic poles.

The past few months have producedsome of the best 2 metre auroral conditionsever experienced. Auroral openings wererecorded in January, throughout Februaryand early March. April 10th provided aparticularly good opening. Again in May,June and July openings occurred; on July13th one of the most intense everexperienced, was being recorded, and evennow, at the time of writing, reports of veryintense auroral openings are still coming in.

We reproduce herewith, a chart recentlyissued by the Sunspot Index Data Centrein Brussels, which shows very well that wehave now reached the downward trend insunspot activity in Solar Cycle 21. With thisdecrease in solar activity, it might seemsurprising that this auroral activity shouldstill be so strong. However, according tothe pundits, a peak in auroral activityoccurs on either side of the 11 year cycle

150

100

S.I.D.C. Solar Cycle 21dots: predicted values (C.Z.M.)line: smoothed monthly means

11. 111 el B2

G2UK.

maximum and we are now enjoying thedownward peak. This is however, not likelyto last much longer. So make the most ofthese openings whilst they last.

Much influenced by ionosphericpropagation conditions is, of course, the10 metre band. Activity on this band isnowhere so great as it has been during thepast few years, but DX contacts are stillpossible particularly from the south. In thepast few weeks PY and ZS stations havebeen coming in strongly at times. A verygood idea of the conditions on 10 metrescan be got by listening for the 10 metrebeacons of which there are a considerablenumber. These have been purposelyestablished to give an indication of'conditions' and quite a lot of interest canbe had by listening for them and keepingrecords of their signal strengths. The writerhas logged DLOIGI on 28.20, 5B4CY on28.22, HG2BHA on 28.225, LA5TEN on28.236, VP9BA on 28.237, Z21ANB on28.248, DKOTE on 28.257 and ZS6PW on28.270 recently.

With future changes in propagationconditions which may affect the 10 metreband in particular, fears are beingexpressed that the 10 metre band may beneglected by radio amateurs and may betaken over by 'intruders'. To promote theuse of 10 metres, J.D. Harris, G3LWM ofBishop's Stortford, J.D. Petters, G3YPZand N.J. O'Brien, G3ZEV of Harlow,recently issued a 'news sheet' in which theyoutlined what they feel are dangers likelyto befall the ten metre band. As they say: -'With the advent of 27 MHz CB;widespread use and congested channels, theamateur radio movement faces a new andworrying threat. Already there are manyintruders in the bottom end of 10 metres,using rigs widely available that go up to 30MHz. The CB operators find 28 MHz agodsend, due to the apparent lack of useby amateurs at times when there is no DXpresent.'

G3LWM and his colleagues aim to bringto the notice of the amateur radio fraternitythe benefits of 10 metre as an alternativeto 2 metres for local - and 'not so local' -working. They point out that historically,10 metres has always been lumped into theHF spectrum and is looked upon as one ofthe best amateur radio DX bands. This itcertainly is during sunspot peaks, but itprovides little in the way of DX openingsat other times. Not so much notice,however, is taken of the fact that when it

is not providing DX propagation, it is avery useful band for less distantcommunication. Direct line of sight,refractive, tropospheric and sporadic Etypes of propagation are far more prevalentthan is realised. This is a point that hasoften been made in the past, but still seemsto be little appreciated. 3LWM asks whythis should be and suggests one reason isthat 10 metre operation is approached withH F rather than VHF techniques. As hesays:- 'Whoever heard of anyone using atrapped vertical, long wire or dipole for 4or 2 metres or 70 cms? At VHF, the correctaerial and polarisation are essential to getresults. A good, sensitive receiver is alsoneeded.' Again as he says, many of thereceivers designed for amateur band use are'deaf' at 28 MHz! 3LWM continues:- 'Inthe mid -70's, a group of stations inBermuda set up a local net on 29.60 MHzusing low power and vertical aerials.Activity spread to the U S A with PMRand C B sets being converted for FM use.The availability of the FT 901 with its FMfacility created world wide FM activity on10 metres. G3YPZ with a modified FT 101was the first 'G3' on FM and caused muchinterest and some 'pile-ups'! The followingprefixes have been worked on FM byG3YPZ:- W 0,1,2,3,4,5,6,7,8 and 9; VE1,2,3,6 and 7; JA, JH, HH, PY, ZS, VO7, UA, EA, DL, LA, OZ, HB 9, 4Z4 andVK. All except the VK were using 10 wattsand vertical aerials.

G3LWM suggests that, to encourage 10metre activity, Groups should be formedto monitor 10 metres regularly, particularlyat the low end; they should encourageactivity on 10 metres, particularly when itseems to be dead; they should reportintrusion from C B and other intrudersinto the low end of the band.

Since G3LWM's first Newsletter wasissued, a very satisfactory response hasbeen received. So it was decided to forma national group to be called '10 -UK'. ANewsletter will be issued two or three timesa year. Annual subscription £3.50. Detailsfrom:- N.J.J. O'Brien, G3ZEV, 88, TheMaples, Harlow, ESSEX.

R&EW

Your Reactions Circle No.

Immediately Interesting 25Possible application 26Not interested in this topic 27Bad feature/space waster 28

DECEMBER 1982 61

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N.B. We regret we cannot supply the 2 metre version on MailOrder as it is too long to go by post.Please allow up to 28 days for Delivery

DEALERS FOUND GUILTY!The CQ Centre in Merton Park were

recently found guilty of paying excessive pricesfor second-hand radio equipment. Roads in thedistrict were totally jammed as eager customersflocked in to take advantage of the generousprices being offered. A spokesman for the com-pany would only comment that this was a firmpolicy and would be continued in the future.Further investigations revealed that there was asale or return service in operation for which thecharges are only 10%. It was also found thatcopious amounts of tea and coffee were beingserved on the premises.


ELECTRONICHOBBIES FAIRAlexandra Pavilion London

November 18-21 1982

The biggest and bestevent ever to bestaged for the

electronic hobbiesenthusiast!

Walk into a whole world of electronicequipment - Everything from resistors, IC s tohome computers, transmitting and receiving

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way to discover all the latest developments inyour particular field.

Ticket pnces at the door are £2 for adults £1 forchildren but party rates are available for 20

people or more. To find out more contact theExhibition Manager Electronic Hobbies Fair

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Electronic Hobbies Fair is sponsored byPractical Electronics, Everday Electronics and

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OPENING TIMESThursday 18 Nov -10.00.18.00Friday 19 Nov -10.00-18.00Saturday 20 Nov -10.00.18.00Sunday 21 Nov.- 10 00 17.00

Choo ondra

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R&EWPROJECTPACKSSSB CW GENERATORCW add on for the SSB transceiver system.PCB and all components.Stock No. Price40-10704 £6.21

PEAK PROGRAMMER METERHigh accuracy professional design PPM.Mono meter and driver unit, with uniquestereo add-on.

Mono Unit

Stock No. Price40-10240 £49.68

Stereo Add-onPCB, all components and LEDs.Stock No. Price40-10241 £11.61

WIDE BAND AMPLIFIERWide band, 14 - 70MHz, transmitter amp.,with a gain of 40dB.Stock No40-14700

Price

£4.18

6m

6m TRANSVERTERProject packs available for these previouslypublished designs:MULTIBAND UP CONVERTERPCB and components for mixer andoscillator 194MHz) sections.Stock No.40-280076m PRE AMPPCB and components.Stock No.40-08007PRE AMP PCBStock No. Price44-08004 £1.85

Price£14.89

Price£4.71

AUTO NI -CAD CHARGERAutomatic battery charger for fastcharging of 4 Ni-Cad cells.PCB, mains transformer, heatsink andall board mounted components.Stock No. Price40-40004 £22.70

TX10 VIDEO INTERFACEComplete kit of parts available directlyfrom the author. PCB, all components,sockets, switches, sub chassis andinterconnecting cable.Price £21.60 inc. VAT and P&P.From: Paul Pitts

7, Inglewood Drive,OtleyW. Yorks. LS21 3LD

All prices include VAT @ 15% Pleaseallow 21 days for delivery. Postage& Packing 60p per order.Send your order to Radio & Electronics World,

200, North Service Road,Brentwood, Essex CM14 4SGTel: (02771 230909

Access/Barclaycard Welcome.

`PROJECTROARDS'January ZX81 Keyboard B £2.99

UHF/VHF Converter £3.51 0.30v PSU £4.50TV Pre -Amp £1.28 2m PA Mk II £5.91TV Pre -Amp PSU £0.96 ULN3859 lUndrilled) £0.96LC7137 £2.73 LM1035 lUndrilled) £1.29

February JulyTV Pattern Generator £6.55 SSB Exciter £3.87TV Antenna Selector £4.65 HA12017 £2.48TV Antenna Select PSU £0.96 DC Controlled Pre -Amp £12.00TK10321 lUndrilled) £2.04 Radio Control £1.84

March Autobridge £3.5070cm Pre Amp £1.38 Autobridge RF Head £2.2523cm Converter £8.33 Autobridge LED £0.73Converter PSU £1.77MC145151 £2,95 August

ULN2283B lUndrilled) £0.46 18W Power Booster £3.74

AprilZX81 Expansion Board £9.60

Radiation MonitorRewbichron Logic BoardRewbichron Rx Board2m Pre -Amp

£3.27£6.76£3.04£1.11

Ga As Fet Pre -AmpGa As PSUMultiband Up ConverterKB4436 lUndrilled)Switch Mode Power Supply

£4.37£1.54£5.460.67

£2.92Key Pad Security LockKB4417 lUndrilled)

£1.79£0.69 September lUndrilled)

KB4413 (Undrilled) £0.58 CB Noise Squelch £1.20

MayUOSAT4 -way Distribution AmplifierpH Meter

£10.17£5.91£5.04

Drill Speed Controller4/6/10m Pre -AmpA/D ConverterAirband R X

£4.76£1.86£3.73£8 83

KB4412 lUndrilled) £1.43 DFM £4.83

JuneULN2240 lUndrilled) £0.94

DFM Display4448 (Undrilled)

£2.07£0.93

Radio Control Tx2ch Mains Timer - Display

£3.58£6.40

October

PSUTriacSwitch

£2.07£2.07£0.85

70cm PASSB Mixer

£4.02£2.89

CB Selcall £3.33 SSB Buffer £0.98

ZX81 Keyboard - A £2.99 2m GaAs FET Pre -amp £4.14

Train ControllerU264 (Undrilled)MF10 (Undrilled)

NOVEMBER PCBs

£4.96£0.46£0 69

2m Converter £4.1420Hz - 150MHz DFM £2.90Video Interface:

Thorn TX9 £3.95Amstrad CTV1400 £2.21

TDA4420/1 £1.10DNR (From Oct. issue) £3.31

DECEMBER PCBsWide Band Amp £2.79SSB CW Generator £1.86PPM - Mono £1.86PPM - Stereo add-on £1.86Auto NiCad Charger £5.83TX10 Video Interface £3.10

All Prices include VAT @ 15%Please allow up to 28 days for delivery.

'Postage & Packing 60p Per Order.Send your orders to:200, North Service Road, Brentwood,Essex CM14 4SGAccess and Barclaycard Welcome.

DECEMBER 1981 63

Z8 ASSEMBLER IN EPROMDr. B. Jasper of Zilog discusses

new software for the Z8 board consistingof a line assembler and improved utilities.

Many users of the Ambit 8671 microcomputer board will have bynow realised that when programming with BASIC/Debug, it is arelatively easy matter to enter and modify programs or to inputand output data to I/O ports, counter timers and locations in thememory/register file. For applications where the response timesrequired are of the order of tenths of seconds or slower, thecomputational speed of the interpreted BASIC is usually adequate.However, in situations which are time critical and require a programto respond in milliseconds or even microseconds, it becomesnecessary to use machine language. Moreover, a machine languageprogram often requires less code to implement than a equivalentBASIC routine, particularly if bit text and bit manipulationoperations are required.

As an example, consider the two programs shown in Fig. 1. Bothprograms are capable of providing a pulse train at pin 4 of port

25 C=A

30 IFC=0 RET I Check for end of pulse

40 IFG=F STOP I Check for 200 pulses

50 C=C -1

70 GOT030

100 A=6: G=0: F=200 I Entry point

110 @3=%10 I Set bit 4 in por 3=1

115 G=G+1

120 GOSUB 25

130 @3=0 I Set bit 4 in port 3=Q

140 GOSUB25

150 GOTO 110

MACHINE CODE ROUTINE

110

120

PUSH 253

SRP, 11120

130 LDR14, 1200 1 load number of pulses

140 LDR12,

150 LDRIO, 1%6E I Pulse time value in

160 LDR11, 1%09 1 R10 i R11 (RR10)

170 XOR R12, 1%10 1 XOE bit 4 in reg 12

180 LD3, R12 I Output to port 3

190 DECW RRIO I Loop around until RRIO

200 JR 2.190 I = 0

210 DEC R14 I Check for 200 pulses

220 JR NZ 150 I Gone

230 POP 253

240 RET

3, consisting of 200 equal mark -space ratio pulses each ofapproximately 400 milliseconds. The machine language routinetakes 28 bytes of code against 117 for the equivalent BASIC routine.Further, if we want to reduce the pulse period, the minimum timethat can be achieved with the BASIC routine is 74 millisecondswhile with the machine language routine we can get down to 23microseconds.

With the Z8 BAS1C/Debug microcomputer, it is possible to solvea particular programming problem by using either BASIC, Machinecode or a combination of the two. If circumstances dictate thatboth languages are to be used in a program, the mechanism forcomunication between them is for the machine code sections tobe constructed as subroutines and called by either the GO@command or the USR function.

Both GO @ and USR require a subroutine address argumentwhich in turn may be followed by two optional arguments usedfor parameter passing.

i.e. GO @ % 2000, A,B

or GO @ % 2000, A,58

The USR function is similar to the GO@ command, but it canalso be used to return an argument back to BASIC. For example,C = USR (0102000,A,B). The argument returned will be assignedto the variable C.

To enter a machine code routine into memory, however, is notquite so easy. Certainly, it is possible to modify bytes or wordsby using BASIC operators such as @ (ADDRESS) = (BYTEVALUE) or A (ADDRESS) = (WORD VALUE). But if a largesubroutine is to be entered, then this method is both tedious and,since the programmer must know the exact coding for each machineinstruction, prone to error.

With Version 2.0 software, it is now possible to invoke a lineassembler routine which will convert standard Z8 assemblermnemonics entered via the free format BASIC/Debug editor, intomachine code at some specified address in memory. The lineassembler occupies the lower half of the 2732 monitor EPROMand utilises only the internal registers in the Z8 for datamanipulation, thus freeing the RAM space for storage of sourceor object code and the parameters used by the BASIC interpreter.

To write a source code program, it is a simple matter of justentering a line number and the appropriate Z8 mnemonic plus twoassembler directives. Note that this is possible because the editorwill accept any text on a line providing there is a valid line numberie 100 RUBBISH.

Two directives are used to indicate to the assembler where thesource code ends and where the object code is to be located. Thedirective 'END' is mandatory, and is placed at the end of the sourcecode. The other directive '$ABS(ARG)' is used to define where

100 SABS%2000 I Location directive

110 PUSH 253 I Push RP onto stack

120 SRP.1%20 I Set RP - hex 20

130 LDR3,2 I Load R3 from port 2

140 LDR4,1%06 I Load R4 with hex 6

150 AND R3,R4 1 AND R3 with R4, result in R3

160 POP 253 I POP 253

170 RET I Return

180 END I END directive

Figure 1. Figure 2.

64RADIO & ELECTRONWS WORLD

FEATURE

the object code will be located; ARG being the location address.If this directive is not given then the assembler will automaticallystore the generated code at the first location available after thesource text. It should also be remembered that machine codesubroutines must be stored in memory that is not otherwiseoccupied by the BASIC program or the stack.The entry point for the line assembler is at hex location B3EO,so to invoke the assembler we simply type

GOE4B3E0,<Source line number>

where the source line number is the first line of code to beassembled. For the program in Fig. 2 we would write

G08163E0,100

The assembler will then return the message 'NO ERROR' or'ERROR' depending on whether or not assembly was successful.If we use the USR call rather than GO@, the assembler willreturnthe line number of the first error detected. Thus, by writing LISTUSR(010133E0,100) to invoke the assembler, the first lineencountered that contains an error will be listed. For example, saywe replaced the 'AND' in line 150 with 'ANDD' the assembler willreturn: -

ERROR

150 ANDD R3,R4

The assembler is able to detect the following errors:

1. Syntax error.

2. The line number given as the first line to assembly does not

exist.

3. No END directive.

4. The line referred to by a does not exist.

5. Invalid operands for this mnemonic.

6. Displacement>127 or< -128 (relative addressing).

7. Mnemonic unknown.

8. Condition code unknown.

PSEUDO-OPSApart from the standard Z8 instruction mnemonics, there are twopseudo -operations which can be helpful for data insertion. Theseare DEFS and DEFB. The DEFS n (define storage) pseudo -operation can be used to reserve n bytes of memory space startingat the current program pointer ie, DEFS 30 reserves 30 bytes andincrements the program pointer by 30.

The second pseudo -operation DEFB has two forms and is usedto both reserve space and to initialise data. If we say DEFB&n,where lower case n is any decimal (or hex -decimal number, it ispossible to initialise several (n) bytes at a time by separating eachbyte by a delimiter (coma). For example

100 DEFS 6 820,IEE,S44,2,32

will initialise 5 bytes with the respective hexadecimal values20,EE,44,2,20.

DEFB"X is the second form of this operation and is used whenit is required to initialise a string 'X'. For example, 100 DEFB'HELLO will reserve 5 bytes and initialise them with the ASCIIvalues of the charactors HELLO.

BRANCH INSTRUCTIONSBranches or subroutine calls to line numbers (labels)take the formJPN, JRN, CALLN or DJNZ RkN where N is the linenumber. If we need to reference a program or subroutine at aknown absolute location, then we leave out the sign before theargument N which now becomes the address value. The followinginstructions are all valid codes.

JR 82100

JR 9000

CALL 8400

DJNZ R5 82500

It may be noted that another method that can be used to specifyan absolute branch or subroutine call address is to use indirectregister addressing. For example, JP@20 or CALL@20 has theeffect jump or call to the address in register pair 20/21.

MIXING BASIC AND MACHINE CODEWe now look at a modified version of the earlier pulse generationproblem. Assume that we want to generate a pulse train of givenlength, only this time, with the facility for specifying the pulse'OFF' time as well as the pulse width.

The example uses BASIC/Debug for inputing parameters fromthe terminal, while a machine code subroutine is used inconjunction with counter timer T1 to define the pulse 'ON' and'OFF' periods. The output signal is taken from T1 output, Tout(pin 40).

In order to produce the variable mark -space ratio pulse at Tout,use is made of the Z8 feature which allows the counter timersCOUNTLOAD register to be modified without disturbing the countin progress (see Fig. 3). Assuming that the pulse 'ON' time valuehas been programmed into the COUNTLOAD register, setting theload bit for T1 in the TMR (Timer Mode Register) will cause thevalue in the COUNTLOAD register to be transferred into theCOUNT register and, if the count enable bit is set in TMR, startthe COUNT register counting down. The value representing thepulse 'OFF' time can then be immediately programmed into theCOUNTLOAD register and will be transferred to the COUNTregister only when EOC (End of Count) occurs. Once EOC hasbeen detected, say by monitoring IRQ5 in the IRQ (InterruptRequest Register), the pulse 'ON' value can again be reloaded intothe LOADCOUNT register to await transfer to the COUNT registeron the next EOC. This process is repeated until the desired numberof pulses have been output from Tout.

T N XTAL

CLOCKLOGIC

PRESCALERLOAD REG.

76 BIT PRESCALER

COUNT LOAD PEG.

7COUNT REG.

COUNT READ REG.

.2

DECEMBER 198265

Z8 ASSEMBLER IN EPROM

100 List v68(883E0,105) I Make object code

102 STOP

105 $ABS%2000 1 Location directive -hex 2000

110 Push 253 I Push neg ptr onto stack

120 SRP,I1%20 I Set neg ptr to hex 20

130 LD 242,%31 I Load Ti (Count Load) with "ON' time

140 LD 243,$%8F I Load Ti prescaler with 35 & modn

150 LD241,11%9E I Load Ti TM neg

155 LD250,8%17 I Load IRQ neg with reset IRQ5

160 LD242,%30 I Load Ti (Countload) with "OFF' time

170 DECW, RR14 I DECW working reg pair 14615 (2E)

180 JRZ *300 ! Jump out f RR14 = 0

190 CALL *400 I Call "Test for DOC'

200 LD242,%31 I Load Ti (Countload) with 'ON' time

210 CALL * 400 I Call "Test for EOC'

220 JR 160 ! Jump back

300 LD243,11118E Load prescaler with 35 & single pass

310 POP 253 I POP neg ptr.

320 RET I Return

400 TCM 250,./.20 I Test bit 5 in IRQ

410 JR NZ *400 I Jump back = 0

420 LD250 t%17 I Reset bit 5

430 RET ! Return

900 END I END directive

1000 "Pulse on time='; GOSUB1100

1010 6831 -

1020 "Pulse OFF time='; GOSUB1100

1030 8%30

1040 "Number of pulses=' INPUT C

1050 /\%2E=C

1060 GO @ %2000

1070 "<BELL)'

1080 GOTO 1000

1100 Input I

1110 IF I>255 1=255

1120 RET

I

Rgure 4.

The source program for the machine code subroutine is shownin Fig. 4 along with the BASIC terminal interface routine (lines1000-1120). In the subroutine source program, the instructionsPUSH 253, SRP %20 and POP 253 have been included to savethe register pointer (Rp) value used by BASIC and to set a valueof hex 20 for use by the machine code subroutine. The reason forthis is that registers hex 21 to hex 3F are available for the user andtherefore if working register instructions are to be used, Rp mustbe set to point at this free area of the register file. If we don't dothis there is a serious risk of overwriting parameters used for theinternal workings of the BASIC interpreter, and hence causing anunpredictable situation when control returns to the BASIC mode.

Parameters are passed from BASIC to the machine codesubroutine via registers o31 and %30 for the 'ON' and 'OFF'times, and register pair olo2E and %25 for the value representingthe number of pulses to be output. (Note Rp = %20 thereforeRp + R14 = 07o2E). To run this program we simply type GOTO1000 and then, when the BASIC routine asks for them, type inthe appropriate parameters. The performance figures are asfollows:

Number of pulses that can be output = (0 to 65,536)Minimum pulse 'ON' and 'OFF' times = 37.97 microsecondsMaximum pulse 'ON' and 'OFF' times = 9.68 millisecondsMark -space ratio range = 255.1 -> 1:255

The values for Maximum and Minimum pulse time are governedby the size of T1 COUNT register (8 bits) and the delay in thesubroutine loop line 150 to line 200 (approximately 30microseconds) respectively. Calculation of machine codeinstructions can be made using the simple expression:Instruction time = (Execution cycles + No Bytes)*0.271microseconds

UTILITY VERSION 2.0 VERSION 1.0

Program EPROM Time to program 4K . Time to program 4K =

3 minutes 24 seconds 10m 5sec1

Read EPROM <1 sec to read 4K 7m 15sec to read 4K.1

Find Program <1 sec for 4K Basic 2m 34sec for 4K basic

Program Program

Memory More <1 sec for 4K Block 3m 4sec for 4K Block

Display Takes 3sec to display Takes 38sec for full

full screen (255 Bytes

of hex + ASCII) Press

screen

"Q' to Quit.

Ramchange Enter only hex Needs spiace+ %sign

% sign & space no longer

required -

for every hex value

Will discard non hex

value -

Use 'Dot' to continue

"0' to quit.

Fill Memory <lsec for 4K block NA

Compare Displays both bytes that NA

Memory are = Q=quit P=pause

Cassette Asks for start & stop Only asks for address

Write addresses and a file

number <0-65535>

- no file identity

Cassette Asks for start & stop Only asks for address

Read address and a file

number. Will search for

correct file number

printing file numbers

passed during search

- no file identity

Exit Return to immediate mode

Table 1: Comparison of version 2.0 software against version 1.0.N.B.*1 in version 2 software the start address of the EPROM to beprogrammed is 1000 hex and the end is I FF F.


FEATURE

Instruction instruction Addr Mode OPcod Flags AffectedSummary and ration dst arc (1C) CZ S V D H

ADC dat,src (Note 1) 10dat - dat + arc + C

0

ADD dst,src (Note 1) ODdat dat + arc

0

AND dat,arc (Note 1) 50dat - dat AND arc

- 0

CALL dat DA D6SP - SP - 2 IRR D4OSP PC; PC-datCCF EFC - NOT C

CLR dat Bodst - 0 IR B1

COM dot Wdat - NOT dat IR 61

CP dat,src (Note 1) AOdid - arc

- -

DA dat 40dat - DA dat IR 41

. X - -

DEC dat R 00dst dst - 1 IR 01

- * * - -

DECW dst RR 80dst - dst - 1 IR 81

- * * - -

DIIMR (7) - 0 8F

DMZ r,dat RA rAr - r - 1 r = O -F

if r * 0PC -PC + dst

Range: + 127, -128

Ei 9FIMR (7) - 1

INC dat r rEdat - dst + 1 r = 0-F

20IR 21

INCW dat RR AOdst dst + 1 IR Al

MET BFFLAGS -0 SP; SP - SP + 1PC - a SP; SP - SP + 2; IMR (7) - 1

JP cc,dstif cc is true

PC-dat

DA

IRR

cDc =0-F

30

JR cc,datif cc is true,

PC - PC + dstRange: + 127, -128

RA cBc=0 -F

LD dat,arcdat - arc

r Im rCr8r9

r =0-FX C7

X r D7Ir E3

Ir r F3E4

R IR E5Im E6

IR Im E7IR R F5

LDC det,srcdat arc

Irr C2Irr r D2

LDCI dat,arc Ir Irr C3dat - arc Irr Ir D3r - r + 1; rr - rr + 1

Instruction Adds Mods °Peed(' Flags Affectedand Operation at Byte

(Hex) CZSVDHLDE &Lemdst - arc

r Irr 82Irr r 92

LDEI dat,arc Ir Irrdat - arc Irr Irr r + 1; rr - rr + 1

8393

NOP FF

OR dat,arcdat dat OR arc

(Note 1) 40 - 0 - -

POP datdat - OSPSP - SP + 1

IR5051

PUSH arc R 70SP - SP - 1; 0 SP arc IR 71

RCFC-0CF 0

HET AFPC -0 SP; SP SP + 2

AL dstIR

9091

* -RLC dat

1;111310

IR 11

-RR dst 14, IR E0

El _

RRC dstEl =El IR

COCl

_

SBC dat,arcdst - dat - arc -C

(Note 1) 30 1

SCFC - I

DF 1

SRA dst G R DO

SAP arcRP - arc

Im 31

SUB dat,arc (Note 1) 20dat dat - arc

. l

SWAP dat i, *4. .1

FO X X -IR Fl

TCM dat,src (Note 1) 60 - 0 - -(NOT dat) AND arc

TM dst, arcdat AND arc

(Note 1) 70 - 0 - -

X011 dat,arcdat dat XOR arc

(Note 1) BO - 0 - -

Note 1

These instructions have an identical set of addressingmodes, which are encoded foi brevity. The first opcodenibble is found in the instruction set table above. Thesecond nibble is expressed symbolically by a 0 in thistable, and its value is found in the following table to theleft of the applicable addressing mode pair.

For example, to determine the opcode of an ADCinstruction using the addressing modes r (destination) andIr (source) is 13.

Addr Mode

dat arc

LowerOpcode Nibble

r Ir

R R

R IR

R IM

IR IM

Opcode map of the Z8

DECEMBER 198267

Z8 ASSEMBLER IN EPROM

OpcodoMap

Lower Nibble Ohm/

0 1 2 3 4 5 6 7 8 9 A

6, 5 6,5 6,5 6, 5 10,5 10,5 10,5 10,5 6,5 6,5 12/10,5 12/10,0 6,5 12/10,0 6,50 DEC DEC ADD ADD ADD ADD ADD ADD LD LD DJNZ IR LD IP INC

RI 1111 ri, fa ri, Ir2 112,111 RI ALIN 1111,1M t 12, R1 ri, RA cc, RA ri,IN cc, DA ri

6, 5 6,5 6, 5 6, 5 10, 5 10,5 10,5 10,51 RLC

RIRLC ADC

ri,raADCr 1,113

ADCR2,111

ADCU12,11i

ADC111,1M

ADC1111,IM

6, 5 6, 5 6, 5 6, 5 10,5 10,5 10,5 10,52 INC INC SUB SUB SUB SUB SUB SUB

Ai IRi 11, is 11,113 92,91 MLR' ROM 1111,1M

8, 0 6,1 6,5 6, 5 10, 5 10,5 10,5 10,53 IP SRP SBC SBC SBC SBC SBC SBC

IRR1 IM 11,12 Ir2 Rs, Ai 1112, RI 111,1M 1111,1M

8, 5 8, 5 6, 5 6, 5 10,5 10,5 10,5 10,54 DA

RIDAIR 1

OR11,12

ORri, Ira

ORR2,91

ORm2,91

ORR 1, IM

ORIRLIM

10, 5 10,5 6,5 6,5 10,5 10,5 10,5 10,5S POP

I

POPIRi

AND11,12

ANDIra

ANDHz RI

ANDIRa,Ri

ANDit 1, al

ANDMI, U4

6, 5 6,5 6, 5 6, 5 10, 5 10,5 10,5 10,5

6 COMAi

CONIRi

TCMri, r2

TCMri, Ira

TCMAi

TCM1113,11i

TCMRI,Bd

TCMMI, D4

10/12,1 12/14,1 6, 5 6, 5 10, 5 10, 5 10,5 10,57 PUSH

RaPUSH

11113

TMr 1, ra

TMri, Ira

TMR2,92

TM1112, RI

TM114

TMHI 1, D4

10, 5 10, 5 12,0 18,0 6, 1DECW

RRIDECW

1111

LDEmina

LDEIIr 1, Irra

DI

96, 5

ELAl

6,5EL011

12,0LDE

ra,

18,0LDEI

Ira, Irri

6, 1

El

A10, 5

INCWRAI

10, 5

INCW1R1

6, 5

CP11,13

6, 5

CPr1, 1r2

10, 5

CPR2,R1

10, 5

CP1/12,111

10, 5

CP111,1M

10,5CP

IA 1, IM

14,0RET

6, 5 6, 5 6, 5 6,5 10,5 10, 5 10, 5 10,5 16,0B CLR CLR

IR'XORr1, 1.2

XORri, Ira

XORRa, RI

XORM2.111

XOR111,1M

XORI91, 04

IRET

C6, 5

RACRI

6, 5

RRCIRi

12,0LDC

ri, Irr2

18,0wa

Ir 1, lira

10,5LD

r1, s, Fla

6, 5RCF

6,5 6,5 12, 0 18, 0 20, 0 20, 0 10, 5 6,5D SRA

RISRA

IRLDCra,lrri

LDCIIra, Irr

CALL*IRR

CALLDA

LDrs,

SCF

6,5 6, 5 6, 5 10,5 10,5 10,5 10,5-1

6,5E RR

RIRRIRi

LDr1,1112

LDR2, Ri

LD1112,R1

LD LD111,1M [ROM

CCF

8,5 8, 5 6, 5 10,5 6,0F SWAP SWAP LD LD NOP

Al 1111 Iii, 13 R2,11,11

Bytes perInstruction 2 3 2

LowerOpcodeNibble

Execution PipelineCycles 4 Cycles

UpperOpcode A

NibbleMnemonic

First SecondOperand Operand

byte instruction; retch cycle appears as a 3 -byte instruct:on.

Legend:R = 8 -Bit Addressr = 4 -Bit AddressRI or rl = Dst AddressR2 or r2 = Src Address

3 1

Sequence:Opcode, First Operand, Second Operand

Note: The blank areas are not defined.


FEATURE

The reason that 'No Bytes' is included in the equation is becausethe extended timing mode is enabled (bit 5 of R248)which will putan extra t pulse into every machine cycle. Faster machine coderoutines can be run if we place an instruction at the beginning ofthe routine which disables this bit.

UTILITIES

Apart from the line assembler, version 2.0 software also containsimprovements on the version 1.0 software and some additions,notably FILL and COMPARE (see Table 1.0 for comparison). Auseful feature of this software is that nearly all of the utilities usemachine code subroutines for the main body of the utility, withBASIC used for inputing and outputing parameters. Therefore,providing the appropriate parameters have been loaded, it ispossible to call these subroutines from a user program or from theimmediate mode.

As an example, if we wished to assemble the previous programand then examine the code produced, we might write the following:

100 LIST USR (SB3F0,105)

The routine at %B8EE would then give a hex and ASCII dumpof the memory contents between the limits of A and B (o2000to olo2100).

I should like to thank my colleague Alain Georges of our Frenchoffice for allowing me to modify his line assembler to work in theAMBIT Z8 board.

Next month: interrupts and math routines.

For more information the following documents should bereferred:

Z8 Microcomputer Technical Manual.Z8 PLZ/ASM Assembly Language Programming Manual.

NB. Z-8 is the registered trade mark of Zilog Inc.

R&EW101

102

A - $20000

GOMBEEz B - 82100

Your ReactionsCucle No Circle No

104 STOP Immediately Interesting 65 Not Interested in this Topic 67105 SABS112000 Possible ApplicationL 66 Bad Feature/Space Waster 68

-1

ASSEMBLER EXAMPLES NOP LD R0,854(R8) +

CCF LD 40(R2), R12@=Indirect register

CLR R15 LD 20, 424=Immediate data

CLR @30 LD @20,R14B=Hex value.

CLR 30 SUB @R4,$0R=Working register designator

COM R4 TCM 4,@R10

CON @R3 TM R4,20ADD R4,@R8 DJNZ R3 82006

CP 20 JP *150ADC 30,20 DJNZ R12, *300

POP 253 DECW RR8ADC RO, @123 IRET

SR @R15 RLC 25ADD tED,@RO RET

OR 4,668 RL @ R6DEFS 15 DEFB ' HELLO

RCF RR @30DEFS 820 SWAP R5

DEFB 524,36,1tEE RRC R15LDC R3,@RRIO SWAP 20

DI SRA R9LDCI @RR4,@R6 XOR R4,R5

INCW RRIO SBC R9,@73CALL *210 SWAP @ 30

INCW 60 LDE R3 @RR12CALL @30 XOR R5,41

INC R2 LDEI @R1,@RR7CALL 83000 XOR @R6,17

DA R5 JR * 500CALL 8040 XOR 60,859 Index mode)

LOW COST PROFESSIONAL TEST INSTRUMENTS

116.8'43521 ILI KNI elernic

I. u ' s

Hand Held

Analogue andnotatr orlic

Digital

sabtronics Multimeters=,1

FREQUENCY METERS :16 Models100MHz, 600MHz, and1GHz Models

from £62from £18.75

PST

FREQUENCY METERSANALOGUE MULTIMETERSDIGITAL MULTIMETERSFUNCTION GENERATOROSCILLOSCOPESPOWER SUPPLIESLOGIC PROBESCOPE PROBES

Write or phone for illustratedtest instrument catalogue and pricelistBlack Star Ltd.9A, Crown StreetSt. Ives, HuntingdonCambs. PE17 4EBTel: (0480) 62440 Telex 32339


DECEMBER 198269

HITACHI 9500

A 'second generation' recorder that boasts full IR remote control and Dolby NoiseReduction amongst many other features. At around £500 Peter Luke concludes thatit's a bargain.

THE RECENTLY LAUNCHED 9000series of video recorders from the Hitachistable are not merely cosmeticallyengineered versions of their previous 8000range, but are, what might be termed,second generation recorders. Theexperience gained during the design andsubsequent production run of the 8000models has enabled Hitachi to produce anew batch of recorders that boast animpressive array of features, excellentperformance and reliability at a reasonablylow retail price.

The 8000 series was developed aroundthe 8500 model (see R&EW July 1982), therange being expanded with the addition ofthe full spec. 8700 and the 8300 budgetmodel. The 9000 series features directreplacements for each of the earlierrecorders in the shape of the 9700, 9300and, the subject of this review, the 9500.Each of the new models enters the marketat about the same price as its predecessorbut each has more facilities than theequivalent earlier machine. This philosophyof more and more machine for the samesum of money, rather than a continualdownward move in pricing is common tonearly all consumer electronic goods -presumably there's no reason for Hitachito 'buck the system'.

A MATTER OF STYLEThe appearance of the 9500 is a departurefrom that estabished with the 8000 series,being a mixture of the familiar Japanesemetallic grey together with an all blackfront panel. Attractive yes, but some of the

The Hitachi's IR remote control unit duplicatesall front panel motion controls land addsframe advance) as well as offering sequentialup and down channel changing.

controls suffer from the black cat atmidnight syndrome, being rather hard toaccurately locate. The channel selectorbuttons, of which there are eight, sufferparticularly in this respect, especially duringprogramming of the timer as the channelnumber legend lights are extinguishedduring this process. Finding the rightchannel is very much a question of feeling

your way along the row of buttonscounting as you go.

The tape motion controls are all solenoidoperated, a standard feature on even thecheapest machines today and under fulllogic control - again, to be expected on anynew machine. The controls are large andfeature LED indicators in most cases (thecat's eyes?).

The eject function is still manual ratherthan solenoid operated, although fullyinterlocked to prevent a cassette beingejected whilst the tape is in motion. Thisat least has the advantage that the cassettecan be removed in the absence of power.The cassette draw is not damped, onefeature that has surprisingly been droppedduring the 8000 to 9000 transformation.

TRICKS OF THE TRADEThe 9500 offers most of the useful trickfunctions, omitting the gimmicky doublespeed play and the slightly more useful halfspeed functions. Also missing is an indexfacility. This feature is found on many 'upmarket' recorders and records, on a controltrack, a brief pulse that identifies the startof a recorded section. Very useful in rapidlylocating various sections on a long tape andperhaps the facility most missed in the9500's list of features.

The recorder does however providevisual search at nine times normal speed inboth the forward and reverse directions.Also featured are pause, frame advanceand audio dub.

We'll discuss the performance of therecorder later in this review, merely


REVIEW

ri ri DILi. Ai f Le. _I

oaf

MIN

0 I-1 ZI CI

I MOW

The clock display and the four digit'electronic' tape counter.

working our way through the list offeatures for the moment.

Full IR remote control is a standardfacility on the 9500, the remote unitduplicating all front panel motion controlsand offering sequential channel change(step up/step down).

A full complement of audio/videoin/out facilities are provided via fourphono sockets concealed behind a frontpanel flap. The front panel location ofthese sockets does make them easilyaccessible but means that if leads are to bepermanently connected to any of them (asmay well be the case if the audio output isused to feed an external amplifier/speakercombination) a slightly untidy appearancecan result.

As is usual on Hitachi machines,switching between video and audio sources(built-in tuner or front panel input) is doneon a priority basis, thus inputting a signalvia the input sockets will override the off -

air signal. If the recorder is in the playmode, the played back signal will overrideall other sources.

The front panel flap also conceals aremote pause socket and a `mic' input -both for use if the 9500 is to be operatedin conjunction with a TV camera andsuitable mains adaptor.

TAPE MEASUREThe 9500 features an electronic tapecounter, although this is strictly anelectronic implementation of a mechanicaltape counter rather than a true elapsed timeindicator. A disappointment as an elapsedtime/time remaining indicator is a veryuseful device and a few pounds more spentin this area would have been very welcome.Having said that, the digital display of the9500 is easily read, something that cannotbe said for the tiny mechanical display ofthe 8000 series.

COUNTIIIM

11010111101i1

CLOCK

MIN

I rII" I Li

VOW 1161111

The first stage in setting up the Hitachi's timeris to select the program memory to be entered(one in this case( and the program start time.

The tape counter's display is separatefrom that of the clocks and can be turnedoff by a front panel button and isextinguished when the recorder itself is setto standby - although in both cases its`position' is memorised.

The counter is reset by another frontpanel button but is not automatically resetwhen a cassette is ejected - a useful featureon some machines: who said Fl?

The recorder also has a memory option,which will stop the tape during rewind asthe counter reaches the zero mark.

The most important facility that hasfound its way into the mid -priced 9500 isthe Dolby Noise Reduction System. Someform of noise reduction is a must if the lowlinear tape speeds used in the VHS and Beta

produce an audioperformance that is anyway acceptable interms of S/N ratio.

The Dolby circuitry is activated by afront panel control, rather than beinghidden away behind a flap somewhere. Aminor irritation however, is that there is noLED to indicate that the Dolby system isactive and impossible to tell from a glanceat the recorder - back to those black cats.

Construction of the 9500 is of anadequate quality although it does not oozerobustness with the on/standby and timeron/off switches not looking up to the job.It should, however, stand up to the gentledemands of domestic life - in fact accordingto some trade sources Hitachi recorders aresome of the most reliable with a failure rateof only 1% during the first year - someother brands rating a 10, which unlike BoDerrick's case, is not very good.

IN ACTIONInitial setting up of the recorder is a fairlystraightforward procedure with each stepbeing adequately explained in the manual

The program duration and the day on whichthe recording is to commence are thenentered

for the benefit of the video tyro.Tuning of the eight channels of the

recorder is via a set of thumbwheel pots,rather close together and 'fiddly' to set butas this is a once and only - or at least rarelyperformed - operation such a failing iseasily forgiveable.

Tuning the TV set to the Hitachi'smodulated output is aided by a (visiononly) test signal - the modulator'sfrequency is adjustable to allow it to be setat a frequency other than the preset channel36 if this results in co -channel interferencewith a broadcast station in your area.

Setting up the recorder's clock is simpleenough; set AM/PM (it's a 12 hour clock),then set hours (tens and units) and minutes(tens and units) - these operations

by means of advance and setbuttons. An operation that's more timeconsuming to explain than to implement.

It is not necessary to set up the day asthe timer is only capable of recording up

to 10days in advance, the precise day beingentered as 'present' plus a number from 0to 9.

Operation of the timer is delightfullyeasy - so much so that no error messageswere thought necessary. Having set up theprogram memory to be entered (1-3) thestart time is set in the same manner as theclock. At this stage, rather than enteringa stop time, the duration of the recordingis entered. Finally the day of the recordingis entered (day 0 will record a program laterthe same day). The contents of the threeprogram memories can be easily verified.

QUALITY COUNTSThe quality of the results obtained with the9500 are up with the best that the VHSformat can offer until, that is, the promised'professional' VHS recorders make theirdebut.

The 9500's in/out sockets are concealed behind a front panel flap.While this means there's no groping about at the back of themachine to find the appropriate socket it can lead to an untidy appearance.

DECEMBER 1982

HITACHI 9500

The recorderfeatures amanual asopposed toelectronictuner, andprovides atest signalgenerator.A displaybrightnessoption isalso available.

Playback of material recorded on the9500 showed adequate resolution and littlein the way of chroma shift or displacement.

Engaging play blanks the screen forabout five seconds as the recorder's circuitrystabilises - an approach that is preferable,in this reviewer's opinion, is to maintainthe off -air signal during the stabilising ofthe circuits.

On the subject of muting, manymachines mute sound and vision while nooff -air signal is present. A good idea as,while 'snow' on screen is not tooobjectionable, the roar of unmodulatedaudio is very annoying if, for example, themachine is stopped during a late night videofilm when the broadcast stations haveclosed down.

This photograph shows that the 9500's stillframe performance is excellent.

The nine times visual search produces apicture that is viewable, noise bars arepresent and, as explained in last month'svideo news, the number of noise barspresent depends on the linear tape speedand, as might be expected, a nine timesvisual search produces quite a few suchbars.

The visual search functions arecontrolled by 'dedicated' buttons, muchbetter than sharing the function with therewind controls.

Pause worked well, with any noisehidden from view at the top or bottom ofthe screen. The recorder has about threeframes in which to get things right, takingabout half a second to do so.

Frame advance is just that, with the tapebeing 'pulsed' forward one frame at a time.

The Dolby system did an excellent job,with the annoying HF hiss, characteristicof any recorder without some form of noisereduction, being reduced to an acceptable

level.Leaving the Dolby 'on' when playingback unencoded tapes resulted in a slightlydull, but quite acceptable, audio quality.

GOOD VALUEThe 9500 is widely available at around the£500 mark and at this price must beconsidered a good buy. The provision ofIR remote control and Dolby NoiseReduction take it firmly out of the budgetgroup of recorders, and the facilities itprovides are comprehensive enough formost uses.

These points, together with Hitachi'sname for reliability, make the 9500 worthyof serious consideration.

FOOTNOTESince preparing this review at least oneother assessment of the 9500 has passedR&EW's way. While the general consensusformed by the other review was much thesame as that of our look at the machine -namely that it offers excellent value formoney in terms of quality and features -in other areas the review finds fault withthe recorder's operation which to us seemedfaultless.

In particular the other magazine'sreviewer found the Hitachi's timer difficultto master - reinforcing this opinion withphrases such as 'you'd need a degree to beable to fathom the timer's operation and'the manual had to be left near the machineas it had to be constantly referred to whensetting up the timer'.

If you've read the above review, you'llfind that we thought the timer to beparticularly easy to use. Now it may be thatthe R&EW staff, being in the main froman engineering background, are at one withcomputers/calculators and video recordertimers and that people from a more'artistic' background would find the timeran obstacle. We somehow doubt it.

The divergent views on this machine'soperation do highlight the fact thatreviewers are only human and as such, anyreview will to some extent be a subjectiveassessment of a piece of equipment'sperformance (no more so than many of thereviews appearing in hi-fi magazines). Thisreinforces the oft made point, that whilereviews can point buyers in the rightdirection and, to a certain extent, educatethem as to what to look for, there is nosubstitute for going along to your localdealer and asking for a demonstration. Anyreputable dealer should be able to put therecorder through all its paces and be ableto answer any of your questions withouthaving to continually refer to the manual.If he cannot, take your custom elsewhere.

R&EW

Your ReactionsImmediately InterestingPossible applicationNot interested in this topicBad feature/space waster

Circle No.

49505152


PEAK PROGRAMMEMETER

Following on from last month's introduction to audio specs and thetheory of professional PPM design, David Strange describesa Peak Programme Meter project; easily adaptedfor mono or stereo signal sources.

The basic unit consists of a mono PPM andoptional adaptor board, which allowsstereo presentation on a single meter. Theimpedance of the inputs is high, to preventloading of the circuits being monitored,and although the amplifiers are intendedfor standard levels (0.775 V RMS = OdB),their gain is adjustable. `Line-up', a lengthyand sometimes tedious task with somePPM circuits, has been simplified to just2 steps -without compromising the meter'saccuracy. The R&EW PPM will drive anyBS PPM movement, and is dimensioned tomount directly onto the input studs of mostcommonly available meters.

CONSTRUCTIONHigh stability 2% resistors should be used,as indicated, and the first step is to insertwire links, pins and sockets into the boards.Round off the ends of the cage jack pins(if used) before soldering. ZD1, RI, CI andC201 should be omitted if the PPM is tobe driven from a split supply. It ispreferable to use sockets to mount the IC's

and then insert all the other components,checking correct orientation - thetransistors used in the prototype were 'I,'suffix types (collector centre leg). Finally,note that R11 and R10 are mounted viapins (RIO = 68R, R11 = 68k monoversion; R10 = 68R, R11 = 220k stereoversion).

SETTING -UPMono version: having had one last look atthe boards to check everything is in place,secure the mono board to the meter studs,observing polarity. Check the mechanicalzero of the meter and adjust if necessary.When using a single rail supply the audiomay be referenced to either positive ornegative rail, but when a split rail is usedthe signal should be referenced to OV.Apply power and adjust the meter to readzero using RV2. Then adjust RV3 so thatthe divider chain voltage is at maximum.Apply a 1kHz tone of -8dB (see equivalentRMS voltage in specification table) andadjust RV1 to bring the meter to read -8dB

Both boards are required for stereo - these plug together via longconnecting pins.

e

or PPM mark 2. Next apply a + 8dB 1kHztone and adjust RV3 to bring the meter to+ 8dB or PPM mark 6. Check the meterzero again and calibrate all scale pointsagainst the specification table. The timeconstants should be correct, but may bechecked if the facilities for applyingappropriate tone burst exists (rememberthat R 11 has a different value in the stereoversion).

DIMENSIONS (mm):

POWER REQUIREMENTS:

INPUT:

SENSITIVITY:

FREQUENCY RESPONSE:

61 wide x 74 long x 30 deep(with 2 boards combined)24V to 30V DC or +12Vto +15V DC (current 40mAat 24V)Unbalanced; may bereferenced to either rail orOV.

50k impedance.Adjustable from -6dB tobeyond +20dB (indicatedas 0dB on the meter)31.5Hz to 16kHz + 0.3dB

Table 1: The specifications for our stereo/mono PPM.

When you've established the mono version is working correctly,switch off and plug in the stereo adaptor board. Restore power,and with no signal applied check zero; adjusting RV2 as necessary.Check that both LED's are extinguished. Next apply a + 8dB I kHz

boards and adjust RV201 so that + 8dB is indicatedand both LED's remain lit. You should be able to observe the 'take-over' point, from one rectifier to the other, by watching the meterneedle as well as the LED's. Once the PPM has been aligned, RV!and RV201 may be used as gain control.

DECEMBER 1982 73

PEAK PROGRAMME METER

CIRCUIT DESCRIPTIONThe signal is applied to RV1, via ACcoupling capacitor C2, and then to the non -

inverting input of ICI. This has unity gain,in the positive half cycle of the input, andx2 gain in the negative half cycle. The signalis recovered from the junction of R3 andD2 and applied to the inverting input ofIC2. Here, differential summation with the`unprocessed' signal at IC2's non -invertinginput, results in a 1:1 undirectional versionof the original signal, which is then appliedto the base of Q1. This transistor is usedto obtain a lower output resistance fromthe rectifier and D4 is present to isolate thecharged capacitor C7. In order to removeany non -linearity effects from Q I and D4,feedback is taken from D4 to the input ofIC2.

A capacitor, C7, is charged through R10,and discharged by R11, to provide the timeconstant of the PPM. From C7 the DCsignal is applied to IC3, whose output isused to drive the PPM movement (viaR25). With regard to IC3's gain, it isentirely signal dependant. Initially, whenthe signal is below approximately - 10dB,the gain is set by R15 and R16. However,with higher levels, Q5 is turned on and R17is then 'seen' as parallel with R16. Thisincreases the gain, which is `held' untilabout -2dB input, when Q4 begins toconduct (R14 is parallel with R15) and thegain is decreased again. At about + 2dB,Q3 conducts and R13 parallels with R15and R14 reducing the gain still further.Finally at about + 6dB, Q4 conducts andR12 parallels in- circuit to reduce the gainof IC3 to a terminal value.

The points at which Q2, Q3 and Q4conduct, are set by voltages on a resistordivider chain across ZD2 - VR3 adjusts thevoltage at the top of the chain, allowing forzener tolerances.

0VE SUPPLY

L AUDIO

0ov

R1

TO ALL IC PIN 7,01 COLLECTORAND R27

ZD112V

47t,

C2680n

VE SUPPLY0 /TO ALL IC PIN 4

R347k

t 7

IC1NE531

R447k

1N41418

COMPONENTS LIST

Resistors

R1,27,214,215 1k82,3.4,5,6,202,203,204,205,206 47kR7,8,25,207,208 4k7R9,26,209 2k2R10 68RR11,13 68kR12 27kR14 180kR15,19 120kR16 39kR17 56kR18 470kR20 22kR21 82kR23 3k3R24 5k6R25 4k78210,211,212,213 10k

Potentiometers

Vi.11 201 50k 20 turn cermetpreset

VR2.3 10k 20 turn cermetpreset

CapacitorsC1,201C2, 202C3,4,5,6.203.204,205.206C7

SemiconductorsLED 201,202BC182L8C212L1N4148

B2788C12VB2788C5V6ICI,2,201,202IC3,203,204,205

47u elec680n poly

47p22u tent

TIL21201,5,201Q2.3,401,2,3,4,201,202.203,204ZD1ZD2NE531741

Miscellaneous8 pin sockets, cage jack sockets, cage Jackpins, 1mm PCB pins, PCB (A and BI SifamPPM (movement type 24AI.NOTE. The meter movement may be replacedby a bargraph driver and a row of LEDs,though the specification may be altered

The capacitors C3, C4, C5 and C6 (incombination with R7 and R8) compensateICI and IC2 which, because of their highslew rate, would otherwise oscillate.The stereo adaptor was designed to be usedwith the mono section already described.So, circuit operation will be consideredassuming the boards are connected.

As can be seen, the input and rectifierstages are the same as the mono version.If the voltage on D204 is greater than thaton D4, then D4 becomes reversed biased(ie open circuit), allowing C7 to be chargedby D204. However, if the voltage on D4 isgreater, then it will charge C7 - the voltageon C7 is either L or R, whichever isgreatest.

Since only one diode conducts, RIO is the

R5 R6471. 47k

01BC182L

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R841/7

+2% OR BETTERt SEE TEXT

D41N41418

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R1068R

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same value in the both versions. However,R11 must be increased, for the stereo pair,since the decay time is reduced by parallelresistors R205, 206 and R5, 6. The channelresponsible for C7's voltage, is determinedby IC203 and IC204. These are used ascomparators for the voltages on D204 andD4 - the largest signal being shown by oneof the LEDS. To prevent either LEDlighting when no signal is present, athreshold is introduced by IC205. Thevoltage from IC3 is then compared with astanding voltage from potential dividerR216 and R217 (the switching threshold isnot critical, being around -30dB).

R12*02 27k

0111110BC212L

R1120k

05BC182L

26V

VE SUPPLY

R271k

R26 VR32k2 10k '

5 R20 R24 I R25 22k 5k6 4k7VR2

10k

R17 R1956k 120k

R18470k

Figure 1: Circuit of one board for the PPM (mono version)

PPk1MOVER -Et T

Z025V6

C


PROJECT

ATO ALL IC PIN 7,0201 COLLECTOR ANDAND R216

0R.AUDIO

C2021u

VR20150k

' R204 R205 ' R20647k 47k 47k

R2037k

1N4148

D2011N4148

2 IC201NE531

4470470

C20347p

R202. R20747k 4k7

2

3

D2031N4144

IC202 6NE531

8

4 1471.11170C205 C206

R2084k7

AVE

02041 N4148

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R21010k

R21110k

R21210k

R2092k2

R21310k

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7 R2141k

IC203 6

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IC204741

4

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R21511.

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01 02 03 04

PIN NO 1.61EG SUPPLYPIN No. 2 - AUDIOPIN NO 3 POS SUPPLYYIN NO 4 OV0= PC PIN

, CAGE JACK SOCKET

IC3

± 2% OR BETTER

441 i.1 R16 h.

I

815 ).

METERyr

R11 AND RIO MOUNTED ON PC PINE

be c b e

L VERSION 13 VERSIONTRANSISTORS

Figure 3: Component overlay for the mono PPM board

IC205

C202

1 2 3 4

0 --softA B

PIN NO 1 MEG. SUPPLYPIN NO 2 , AUDIOPIN NO 3 = POS SUPPLYPIN NO 4 - OV

LED 201 LED202

I

0 o d 0CATH L

IC204

R212

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Figure 4: PCB overlay for the extra components required to constructthe stereo version.

OV

Figure 2: Circuit diagram of the stereo add-on board

R21727R

PPM MARK V RMS dB ERROR dB

1 0.195 -12 ±0.52 0.308 -8 ±.0.23 0.489 -4 ±0.34 0.775 0 ±0.25 1.228 +4 ±0.36 1.946 +8 ±0.27 3.084 +12 ±0.5

Table 2: Results obtained from accuracy tests at each PPM mark.

TONE BURST mS INDICATION dB

100 0 ±0.510 -2.0 ± 0.5

5 -4.0 ±0.751.5 -9.0 + 1.00.5 -17 + 2.0

Table 3: Dynamic response (attack) to varying period tone bursts (ze ocrossing bursts of 5kHz sine wave - at + 8dB continuous reading - and10kHz for the 0.5mS burst).

DYNAMIC RESPONSE, DECAY (time taken formeter to fall between +12 dB and -12 dB, whena steady signal is removed): 2.8 + 0.3 secs.

DYNAMIC RESPONSE, OVERSHOOT: < 0.5 dB

Table 4: Other test results (using the procedures indicated).

PPM AND VUMCalibration of the PPM against an existing VU meter - in a tapemachine say - is quite simple. A )kHz tone should be used to makethe VU meter indicate 0 VU and then simultaneously on the samesignal, the PPM should be adjusted to read mark 5 or + 4dB. Thiscalibration having been carried out, the VU meter should be ignoredand signals monitored on the PPM alone (signals should be allowedto peak up to + 8dB or mark 6). R&EW

Your ReactionsCircle No Circle No.

Excellent - will make one 41 Seen Better 43Interesting - might make one 42 Comments 44L

DECEMBER 1982 7C

QRV? FER EOMICR70, The very latestfrom Icom! £469.

z °a _..j"

Now that we have tried the R70, we believe that it is going to be areal winner.

The R-70 covers all modes (when the FM option is included), anduses 2 CPU -driven VFO's for split frequency working, and has 3 IFfrequencies: 70MHz, 9MHz and 455KHz, with a dynamic range of100dB.

Other R-70 features include: input switchability through a pre-amplifier, direct or via an attenuator, selectable tuning steps of1KHz, 100Hz or 10Hz, adjustable IF bandwidth in 3 steps (455KHz).Noise limiter, switchable AGC, tunable notch filter, squelch on allmodes, RIT, tone control. Tuning LED for FM (discriminator centreindicator). Recorder output, dimmer control.

The R-70 also has separate antenna sockets for LW -MW withautomatic switching, and a large, front mounted loudspeaker with5.8W output. The frequency stability for the 1st. hour is ± 50Hz,sensitivity- SSB/CW/RTTY better than 0.32 Av for 12dB (S+N)+N,Am -0.5µv, FM better than 0.32 for 12dB Sinad. DC is optional on theR-70. It has a built-in mains supply.

The IC -R70 measures 286mm x 110mm x 276mm and weighs7.4Kg., making it a very attractive package indeed. Are you readyfor this truly excellent receiver? You must hear it, we know you willbe impressed!

IC -25E, The Tiny Tiger ,mERF4

£239.inc.

Amazingly small,yet very sensitive.Two VFO's, five memories,priority channel, full duplex and reverse, LED S -meter, 25KHz or5KHz step tuning. Same multi -scanning functions as the 290 frommic or front panel. All in all the best 2M FM mobile ICOM have evermade.

Remember we also stock Yaesu, Jaybeam, Datong, WelzG -Whip, Western, TAL, Bearcat, RSGB Publications.Agents (phone first - all evenings and weekends only,except Scotland).Scotland - Jack GM8 GEC (031 665 2420)Midlands - Tony G8AVH (021 329-2305)North West - Gordon G3LEQ (0565 4040 Ansafone available)

Introducing the NEW IC740.£699.

This latesttransceiver containsall the most asked -for features, inthe most advanced solidstate HF base station on the amateurmarket...performing to the delight of the most discerning operator.

Study the front panel controls of the ICOM 1C-740. You will seethat it has all of the functions to give maximum versatility to tailor thereceiver and transmitter performance to each individual operator'srequirements.

Features of the IC -740 receiver include a very effective variablewidth and continuously adjustable noise blanker, continuouslyadjustable speed AGC, adjustable IF shift and variable passbandtuning built in. In addition, an adjustable notch filter for maximumreceiver performance, along with switchable receiver preamp, and aselection of SSB and CW filters. Squelch on SSB Receive and allmode capability, including optional FM mode. Split frequencyoperation with two built-in VFO's for the serious DX'er.

The IC -740 allows maximum transmit flexibility with front paneladjustment of VOX gain and VOX delay along with ICOM's uniquesynthesized three speed tuning system and rock solid stability withelectronic frequency lock. Maximum versatility with 2 VFO's built inas standard, plus 9 memories of frequency selection, one per band,including the new WARC bands.

With 10 independent receiver and 6 transmitter front paneladjustments, the IC -740 operator has full control of his station'soperating requirements.

See and operate the versatile and full featured IC -740 at yourauthorized ICOM dealer.

Options include: FM Module Marker Module Electronic Keyer 2 - 9MHz IF Filters for CW 3 - 455MHz Filters for CW Internal AC Power Supply

Accessories. SM5 Desk Microphone UP/DWN Microphone Linear Amplifer Autobandswitching Mobile Antenna Headphones External Speaker Memory Backup Supply Automatic Antenna Tuner

Ask about the new range of CUE DEEantennas, the winners in recent tests!



[ARV? FER ICOMThe World's most popular portables1C.2E £159.1C4E £199.inc.

and now the marine version

IC -M12 £199 -VAT.

ft II*440,11

Nearly everybody has an IC -2E, themost popular amateur transceiver in theworld, now there is the 70cm version whichis every bit as good and takes the sameaccessories.Fully synthesized - Covering 144-145 995 in 400 5KHz steps. (430-439.994E) Power output -1.5W. BNCantenna output socket Send/Batteryindicator. Frequency selection - bythumbwheel switches, indicating thefrequency. 5KHz switch -adds 5KHz to theindicated frequency. Duplex Simplexswitch - gives simplex or plus 600KHz orminus 600KHz transmit (1.6MHz and listeninput on 4E). Hi -Low switch - 1.5W or150mW External microphone jack.External speaker jack.The IC -4E is revolutionising 70cm!

Multimode Mobiles1C.290E £366.1C -490E £445.inc.

290E-144-146 MHz/490E-430-440 MHz.10 W RF output on SSB, CW and FM.Standard and non-standard repeater shifts.5 memories and priority channel.

Memory scan and band scan, controlledat front panel or microphone. Two VFO's.LED S -meter. 25KHz and 1KHz on FM -1KHz and 100KHz tuning steps on SSB.Instant listen for repeaters.

IC.720A Possibly the bestchoice in HF. £883.inc.

One way of keeping up with rapidlyadvancing technology is to look at what theIC -720A offers in it's BASIC form. Howmany of it's competitors have two VFO's asstandard, or a memory which can berecalled, even when on a different band tothe one in use, and result in instant retuningAND BANDCHANGING of the transceiver?How many include really excellent generalcoverage receiver covering all the way from100KHz to 30MHz? How many need "notuning or loading whatsoever? and take careof your PA, should you have a rottenantenna. How many have an automatic RITwhich cancels itself when the main tuningdial is moved? How many will run full powerout for long periods without overheating?How many have band data output toautomatically change bands on a solid statelinear AND an automatic antenna tuner unit?

The IC -720A may be just a little moreexpensive than some, but it's better thanmost! Make your choice an IC -720A.

IC-PS15 Mains PSU £99.

Tono RTTY and CW computers

7000E £500. 9000E £650.inc.

The TONO range of communicationcomputers take a lot of beating when itcomes to trying to read RTTY and CW in thenoise. Others don't always quite make it!

Check the many facilities offered beforeyou buy - especially look at the 9000E whichalso throws in a Word Processor. Previousads have told you quite a lot about theseproducts - but why not call us for furtherinformation and a brochure?

IC.730 The best for mobile oreconomy base station £586.inc.

ICOM's answer to your HF mobileproblems - the IC -730. This new 80m -10m,8 band transceiver offers 100W output onSSB, AM and CW. Outstanding receiverperformance is achieved by an up -conversion system using a high IF of 39MHzoffering excellent image and IF interferencerejection, high sensitivity and above all, widedynamic range. Built in Pass Band Shiftallows you to continuously adjust the centrefrequency of the IF pass band virtuallyeliminating close channel interference. DualVFO's with 10Hz, 100Hz and 1 kHz stepsallows effortless tuning and what's more amemory is provided for one channel perhand. Further convenience circuits areprovided such as Noise Blanker, Vox, CWMonitor APC and SWR Detector to name afew. A built in Speech Processor boosts talkpower on transmit and a switchable RF Pre -Amp is a boon on today's crowded bands.

Great base stationsIC.251 £499.1C-451 £599.inc.

e40 444?A.eor e"

ICOM produce aperfect trio in the UHF

base station range. ranging from 6 Metersthrough 2 Meters to 70 cms. Unfortunatelyyou are not able to benefit from the 6mproduct in this country. but you CANown the IC -251 E for your 2 Meterstation and the 451E for 70::ms. Mains or 12 volt supply.SSB. CW and FM.

DECEMBER 1982 77

Gary Evans looks at a 16 bitcomputer, computer careand hopes Sony are gamefor a laugh.

SIXTEEN BIT MACHINES are beginningto dominate the market in all but theconsumer sector. The new Comart CP 1000is an excellent example of such a 16 bitmachine. Based on the Intel 8086 6MHzmpu and supporting up to 1 megabyte ofmain memory, the machine offers apowerful processing package.

5" Winchester hard disks, floppies andup to 14 basic modules, will allow thesystem to be expanded to 80 + megabytesof on-line storage and to support up to 7concurrent users.

Operating systems available includeCP/M86, MP/M86 and MS-DOS andsoftware packages offering high levellanguages, financial planning, accountingand word processing applications isavailable, further software will beannounced soon.

Volume production will begin before theend of this year and will initiallyconcentrate on the CP1500 with 128K ofRAM, 5" floppy and a 5M byteWinchester. The price will be £3395.

Details fromComart Ltd.,Little End Road,Eaton Socon,St. Neots,HUNTINGDON,Cambridgeshire.

ALIVE AND WELLSales of the ZX81 are still at a healthy leveland add-ons for this little money spinnerare still appearing at regular intervals.

Latest is a 16K RAM pack from Groundcontrol. Priced at £19.95 the unit fits inwith the overall low cost computingconcept of the ZX81 and has been designedto overcome the 'wobble' and hence dataloss, problems of the Sinclair RAM pack.

An extra £5 will get you a RAM packwith built-in keyboard sounder that canmake data entry faster and less of a strainby giving an audible feedback whenever akey is pressed.

Details from:Ground Control,Alreda Avenue,HULLBRIDGE,Essex, SSS 6LT.

BIB BITSBib, the people that help you clean thosebits of your equipment that other productscannot reach, have launched a range ofcomputer care products.

We all know the benefits of preventivemaintenence, but very few of us areprepared to tackle such tasks if they are atall time consuming. The Bib products makesuch operations so painless that there reallyis no excuse for not tackling them.

The photograph shows the current rangewhich should be available from your localcomputer store.

MICRO FUNSony have sent us a story concerning their3 1-2 inch micro floppy system asfeatured in their SMC-70 micro. It's nowto be made available to OEM customers.

An interesting item, accompanied by arather strange photo. As we've no room forthe caption competition elsewhere in thisissue, we thought we'd give computingnews readers a chance to exercise their wits.

As a hint, the original caption reads'Sony micro floppy disk system productmanager Robin Allison shows off hiswares' can you top that.

Entries to the editorial offices please.The winner of this and last month'scompetition will be announced in ourJanuary issue.




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R&EW Data Brief MSL 9362 RS

The MSL9363RS decodes the digitallyproportional signals from the MSL9362RSencoder (data brief 1). The 14 pin DIL packagedecoder has an AF amplifier input with anoptional low-pass filter (formed by connectinga suitable capacitor on the 'C' input, pin 10).

To decode the signal, the internal oscillatormust be set to the same frequency as theencoder's oscillator. The frequency is defined byresistor (Ro) and capacitor (Co) connected to theinputs OSC 1 and OSC 2. By using the samevalues the two oscillators are synchronized.

The 4 proportional signals, from the AF amp,are defined as the periods between the pulsesfollowing the sync pulse. The sync is producedby the signal generator, as a result of thecoincidence between the transmitted pulse, atframe frequency, and the decoder's internaloscillator frequency.

The decoder, then, gives 4 proportionaloutputs on pins Ito 4 of the IC. Channels 3 and4 are also connected to a latch controlled by thesignal generator. This latch provides 2 logicalON/OFF functions for switching controls, whichgives us two likely modes of operation:

1) 4 proportional channels2) 2 proportional channels + 2 switching

channels.It is interesting to note that when the 4proportional channel mode is being used, theON/OFF outputs are operating simultaneouslyand could be used if a particular applicationrequires it.

14 8

VCC(+4V TO +8V) 0 r1),

OSC 1 011

OSC 2 O1

IN 9

NC

NC

10

0'

OSC

SIG. UP

TYPICAL DECODER CIRCUIT6V

O+

4 0

220KVoc GND

IN OSC2MSL 9363 RS

013

AFAm.

SignalGenera-tor

C OSC1

CI 1 C112 CH3 C114 CH3 C114

I NH

DATA

SYNC

BLOCK DIAGRAM

Decoder

ON/OFF

1

5K I +33u

Ro

33K

Co470p

0 cii 1

V CH 2

0 CH 3

Latch6

CH 4

0 CH 3 ON/OFF

() CH 4 ON/OFF

DECEMBER 198279

ELECTRICAL CHARACTERISTICS (Ta=-10'.+60°C, TYP: Ta=25°C)

PARAMETER CONDITIONSI

MIN TYP i MAX UNIT

Logical "1" 1

I

1

I VI,h VCC = 4VInput Voltage

1

1

i

1.5 I - -1

V

Logical "0"Input Voltage 'IL VCC = 4V - - 0.5 V

Logical "1"Input Current IIN VCC=7V, VIH=7V 0.1 - 1.0 mA

Logical "0"Input Current IIL Vcc=7V, VIL=1V - - -5.0 µA

Logical "1"Output Voltage

VOH Vcc=4V, Imi=-5mA 1.5 - - V

Logical "0"Output Voltage

V 0 V CC=4V,

-mI OL-5A- 0.25 0.4 V

Logical "1"Output Current OH VCC = 4V -8 - -30 mA

OutputLeakage Current ILO VCC=7V, V0=5V - - 10 µA

Supply Current1

ICC1 VCC = 6V - 16 21 mA

ABSOLUTE MAXIMUM RATINGS

*1: IN

*2 : CH1 CH4

4 ch

PARAMETER CONDITIONS RATINGS UNIT

Supply Voltage Vcc Ta = 25°C 15 V

Input Voltage Vin*1

Ta = 25°C -7 A. +10 V

Output Current Io Ta = 25°C*2 -30 % +30 mA

PowerDissipation

PD Ta = 25°C 200 mW

StorageTemperature Tstg

_ -55 '1, +150 °C

aoch 1 c13

MSL9362 RS

ch2 ch4

2 Channels Proportional x 2

2 ch

Control

2 ch Box

chl ch3

MSL9362RSch2 ch4

v

Modulator

Modulator

Receiver

Receiver

MSL9363 RS

ch

1 2 3 4

MSI.9363 KS

h 2 4


NOTES FROM THE PASTCentre Tap's column, from 1951, features some views on the value of a practical

approach to equipment servicing and some adviceon the production of Club Magazines.

A young man fresh from a Technical College, who has recentlystarted in the industry, told me of his surprise to find so muchignorance of mathematics and higher theory among radioservicing engineers. When I pressed the point he admitted thatmany of them were highly successful troubleshooters. PersonallyI should be inclined, despite all his theory and advanced maths,to put my money on some of the troubleshooters I have met ina time -limit servicing competition with him - chaps, too, whomight easily flounder in the simpler examinations. The highlytrained youngster would, of course, track down faults, but hewould do so by complex conscious reasoning. The far lesstechnical veteran would probably put his finger on it half -instinctively in much less time.

Such men, and I have met a fair number despite a ratherlimited acquaintance with servicing engineers generally, are likethe green -fingered gardeners. They have a natural flair for it.Many of them can, with particular makes of sets with which theyare familiar, spot quite obscure and unusual faults almostinstantly. They cannot explain how they do it nor can they teachanyone else. They just have a 'feeling' that a certain thing is notquite right, possibly picked up from some clue such as the formof distortion, the sort of hum, or a trace of melted wax in thecorner of the chassis.

When I was with the Services we had one such chap who hadpreviously run a successful one man repair business. If it hadbeen a private firm, and not the army, he would have had thesack before the first week was up. He was hopelessly lost withstrange and complicated apparatus, but within a few weeks hewas doing the 'sticky' ones - those in the corner over which alot of time had already been unsuccessfully spent, and had beenput aside until we were less busy. Once they got there, by theway, nobody else liked to take them on unless driven to it. Heexplained it quite simply by saying he had now got the 'feel' ofthe sets. Most of us will know just what he meant by the 'feel',but it baffles a more scientific description. True to form, heusually did badly on the various courses on which he was sent,and I believe he even flopped in his first attempt on the trade test.

JUST THE TOUCHThis, which for the want of a better term we call 'feel' cannotbe logically explained. Almost all of us must have met thecraftsman who can accurately judge the quality of materialssimply by handling them. Maybe a baker who knows by the lookand feel of a handful of flour, just what sort of bread it will make,and how much water it will take to the sack, or the chef whocan spot with absolute certainty the tender joint at a glance orgentle thumb pressure. They cannot explain how they 'know',nor can they describe to what extent they depend on sight orother senses.

Similarly, I have seen experienced radio repairers tell the causeof a particular type of background noise simply by listening. Theunaccustomed ear can differentiate between intermittent andcontinuous crackling, or irregular bangs and rumbles, and mostof us are able to reduce the cause to a half -a- dozen possibilities.But the real radio green -fingers detects a subtler difference andcan identify the form of trouble almost instantly in models hehas grown to 'know'.

It seems that unless you are born with the gift you can neverlearn to do it by instinct, and even if you are born with it, it seemsto need quite a bit of practice before it develops. The theorists's

instincts are often blunted by too much theory and examinationknowledge, and while the text -book gets him there just the same,it takes much longer. Perhaps the man with the natural flairwould.be slowed down equally if, instead of 'doing what camenaturally', he tried to work to a book of rules.

CLUB MAGAZINESFrom time to time copies of duplicated Radio Club magazinesreach me, and many of them are very good efforts. Unfortunatelymany of them, after a promising start, soon flicker out ofexistence. Their failure is invariably due to apathy on the partof the members - not the members who read them but thosewho should be helping to write them. The stalwarts who set offto an enthusiastic start gradually lose heart after manydisappointments in their efforts to get suitable material from theirfellow members.

This is a subject on which I can speak with some experience,having in the dim distant past been associated with a radio clubmagazine which, despite a flying start, flopped after a few issues.A second venture with another club (not strictly radio but anallied hobby) ran for well over 40 issues. Why the difference?It was not just luck - there were very solid reasons for it.

For the benefit of amateur editors, here are some of the lessonslearned from the first failure which helped to ensure success thesecond time. Don't wait for the contributions to roll in, and bythat I don't mean for you to keep worrying your fellow membersto simply do 'something'. Plan out what you want from themand then worry them if you must. If they are pen -shy soften themup with a little flattery, and if they are tongue-tied, help themto write it. Warm them up on their pet subjects. Every Club hasa meter expert, a keen TV builder, a gadget merchant, a highfidelity group, and the fellow who is always trying to build amidget small enough to carry in his vest pocket.

Dates and times of future meetings should be given prominentdisplay, and the more unusual events such as outings, parti visitsand general notices, should be accompanied by briefdescriptions.

Finally, get a good production manager to look after thedupicating side of the magazine. One who has a flair fo: thatsort of thing and who takes a pride in making clear, unsmudgedcopies with a minimum of waste.

A well -produced, lively Club News Sheet is a great help bothin maintaining the Club spirit and stimulating local interest. Italso makes the secretary's job easier (and often cheaper) byavoiding the need for him to prepare and send out frequentcirculars. If you can persuade local dealers to display publicitycopies it can also serve as a first class means of recruitment ofnew blood.

Another useful idea is to include among the supporting featuresa review of the leading articles to be found in the current radiojournals. Few hobbyists buy them all and they can thus beassured of not missing items of special interest to them.Occasionally editors of professional periodicals aresympathetically inclined to bona fide amateur group magazines,and may permit reproduction of extracts of articles in past issuessubject to the usual acknowledgement. Don't omit to ask first!

The editor and I are, of course, always interested to see copiesof club and group magazines to see any new ones that may comeinto being as a result of this encouragement.

DECEMBER 1982 81

ReceptionReports

Compiled by Keith Hamerand Garry Smith.

There were no shortages of Sporadic -Ereception during August and there wereseveral days when openings lasted fromearly morning until late evening. Signalsfrom the south and south-eastpredominated and on at least two occasionsthe Jordanian channel E3 transmitter atSuweilih (104 kW) was seen.

Signals from Spain (RTVE) were notedon the 1st at 0841 BST with the colour testpattern carrying the identification `riveGAMONITEIRO 3' on channel E3.Programmes from Eastern Europe werereceived on channels RI and R2 at 0900 andat 0947, the 'RAI PM5544 electronic testcard was seen on channel IA from Italy.

On the 2nd there were no signs ofSporadic-E(Sp.E) reception althoughsignals were noted due to slightly enhancedtropospheric conditions. Receptionincluded the Netherlands on channels E32and E29 with a `TROS' identificationcaption at 2222. At 2245 an unidentifiedFuBK electronic test card from a WestGerman transmitter was seen on E48 withgood quality colour.

Trophospheric conditions were alsopresent on the 3rd with the Netherlands(NOS) on channel E32 at 0725 using the oldPM5540 electronic test card which wasfollowed by the 'EBU Bar' with theidentification `PTT-NL AVVC-HVS'. At1728, Sp.E activity produced Spain on E3and Italy on channel IA.

August 4th was a day to remember withtwo 'exotics' making an appearance. Sp.Ereception was first noted during the earlyafternoon period withCzechoslovakia(CST) on channel RI usingthe 'EZO' test card and the East Germannetwork of DDR:F on E4. The PM5544test card from TVP-Poland was seenduring the same period on channel RI. At1623BST, Yugoslavia was noted on E3from the Belgrade studios with their `JRTBGRD PM5544 which included a digital

clock. At 1627 another PM5544 test cardwas noted on E3 and at first it was assumedto be a different JRT outlet. As the signalstrength increased it soon became apparentthat the signal was not coming fromYugoslavia but Jordan as the identification`JTV AMMAN' could be clearly seen.Unfortunately, reception from thetransmitter at Suweilih was soon swampedby JRT although reception reports fromother enthusiasts suggest that the Jordaniansignal was about for some considerabletime. Later in the day, at 1835, the second'exotic' signal was noted on channel E2with a programme which included acoloured gentleman speaking. Thisprogramme was identified as originatingfrom the Gwelo transmitter in Zimbabwe(ZTV).

At lunch time on the 6th, Hungary wasobserved radiating the `MTV -1BUDAPEST' PM5544 on RI and onchannel E2a, Austria were transmitting theold monoscopic 'Telefunken TO5' test cardcarrying the identification 'ORF FS 1'. Thiswas also noted on E3 from the low -power(100 watts) outlet at Breitenstein. On E2,the ' + P17 SRG FuBK test card wasreceived from the Swiss transmitter locatedat Uetilberg (60kW ERP). The 'EXO' testcard from CST was also noted at this timeon RI. The Portuguese FuBK test card wasseen at 1816 on channels E2 (from the40kW outlet -at Muro), E3 (Lousa, 60kW)and E4 (Valenca Do Douro, 35 watts!) withthe inscription `RTP 1'. At 1830 the 11OMEGA' clock caption was noted fromRTP showing GMT + 1 hour. At 1954 aPM5544 was seen on E4 and this issuspected of being RUV-Iceland sinceIcelandic test transmissions continue untillate.

On August 8th the maximum usablefrequency (m.u.f.) rose sufficiently to allowreception from the USSR on channels R3and R4. Programmes were also received

from Spain (E3), Switzerland (E3), Italy(IA) and Yugoslavia (E3).

Reception on the 11th was limited tomainly medium -hop signals from the south-east. The RAI test card was noted on IAand on RI the CST `RS-KH' electronic testcard appeared. An FuBK test card wasreceived on E2 from West Germany withthe inscription 'GRUNTEN' in the centralblack bar. At 1700 on E3, West Germany(ARD) was again received with theidentification caption 'BR DEUTSCHESFERNSEHEN'. This caption originatedfrom Bavarian television.

Sample pages from 'Teletexto', theSpanish version of CEEFAX, were receivedon the 12th at lunch time on channel E4,and on E3 the black -white -black patternfrom Portugal was noted. Reception fromSpain continued with the 'LA MUELA 3'colour pattern on E3 from RTVE. TheSwiss FuBK test card from SRG was notedon E3 at 1700 BST.

On Friday 13th, signals from Austriaappeared at 0731 with the PM5544 on E2aand on E2 Switzerland was observed fromthe transmitter at Bantiger. At 0830 on RIthe USSR (TSS) monoscopic test cardknown as the '0249' (see R&EW,September 1982) was in evidence, possiblyfrom the 240kW transmitter at Leningrad.

August 15th was a notable, if not astrange day for long- distance television. Afew vigilant enthusiasts noted Sp.E activityas early as 0400 BST although Band I waswide open to the south-east even earlier, asone reader reports. The Italian piratetelevision station, NCT, situated to thenorth-east of Venice was seen presumablyclaiming air space on channel IA. Thepattern displayed did not carryidentification and the caption resembled afootball pitch layout from a video game:Enthusiasts with scanners covering Band Ifrequencies were able to tune in the variousItalian pirate FM transmitters operatingbetween 50 and 60MHz. Many OIRT(Eastern European) FM signals between66 and 70MHz were also present, butreception faded just before 0500. Russiantelevision on channel R2 was received at0611; this had a very slow -fadecharacteristic which suggests a very longreception path. Vertical intervalidentification signals (VITS) were notpresent. Later in the day (at 0916!) aPM5544 test card from Yugoslavia wasreceived with the identification 7RV-1LJUBLJANA'. Also noted on the 15th

Figure 1: Yugoslavian PM5544 test card fromRTV- Ljubljana.

Figure 2: A Cyrillic caption used between JRTcommercials.

Figure 3: The latest Spanish opening -sequence caption.


were sustained signals from Spain,Portugal, Austria (on channel E4), Italy(with RAI and two further appearances ofNCT), the USSR, Hungary (MTV with afrequency -bar pattern and the PM5544)and also an African signal, ZTV-Zimbabweon channel E2 at 1833. Band I activity waspresent until well after 2300.

On August 31st, ZTV was again presentfor a few minutes on E2 from 1820 togetherwith RAI programmes on channels IA andIB. There were also several pop pirate FMradio stations broadcasting between 50 and60MHz.

FEATURED FORTUNESSeveral dedicated enthusiasts have sent uslogs for the August period. A typical logis included here from Clive Athowe(Blofield, Norfolk) detailing reception forthe second half of August.15/8/82:Ch E2,E3 RTP-1 (Portugal) FuBK testcard; E2,E3,E4 RTVE-1 (Spain) progs: IA,IB RAI-1 (Italy) progs, also on channel IDvia Sp.E. Italian FM radio stations notedup to 107MHz plus RTT (Tunisia) FMradio on 96.5MHz.

Ch F2, F4 TDF (France) prog; RI EESTI(USSR) tv prog, also R2. E3,E4 JRT(Yugoslavia); R3 TVP (Poland); E2 NRK(Norway) 'NORGE MELHUS' PM5544;E2 BR- 1 (West Germany); E3 JTV(Jordan) with a programme schedule at1800 BST; IC RTS (Albania) with 'Revista'News prog; E2, E3 YLE-1 progs; R2 TVR(Rumania).17/8.82:IA,IB RAI PM5544; RI TSS 'Letterbox'test card; RI MTV- I PM5544; E3 JRTwith `RTV LJNA' PM5544; RI TVP; E2aORF-1 PM5544;R2 CST 'BRATISLAVA'PM5544; R2 TVR 'Telejurnal' Newsprog;E2,E3,E4 RTVE;E3 RTP.18/8/82:RI TSS(USSR) '0249' monoscopic testcard; RI TVP; E3 unidentified sawtoothpattern to the south-east; R1,R2 TSS Newsprog.19/8/82:RI MTV; RI TSS; RI TVP.21/8/82:Rl,R2,R3 TSS; RI EESTI-tv; E2,E3,E4YLE (Finland) `TV l' FuBK; E2 NRK(Norway).24/8/82:RI ,R2 TSS.

Figure4: An identification caption transmittedregularly by NRK-Norway.

FROM TUNER OUTPUT

Figure 5: Philips G8 selectivity moduleconnection data.

25/8/82:RI TSS colour test card; R2 TSS prog; T IEESTI-tv prog; E2a ORF.26/8/82:E2,E4 RTVE 'Central Control RTVE 09'colour -bar pattern.27/8/82:IA RAI; RI MTV; E2 NRK.28/8/82;RI TSS.29/8/82:RI TSS; RI MTV; E2a ORF.31/8/82:E2,E4 RTVE colour bars; E3 RTVE `riveGAMONITEIRO 3' colour test pattern;E2, E3 RTP; IA, IB RAI 'Telegiornale'News prog; E2 ZTV (Zimbabwe)programme via F2 -layer propagation.

It may be noted from the above log thateven in East Anglia (a DX-ers paradisethanks partly to the terrain, lack of UKtransmitters and close proximity to theContinent) there were days when receptionwas absent. This should give some comfortto other DX -TV enthusiasts who may havebeen peering at blank screens during themonth! Our thanks to Clive for sending hisDX log.

CHANNEL WHAT?Tropospheric reception in Band III andUHF was disappointing during Augustalthough the UHF channels seemed ratherbusy. This was largely due to the IBAChannel 4 test transmissions which mostDX-ers regard as the latest obstacle for DX -TV reception. On the other hand it willprovide endless hours of fun for ourEuropean DX colleagues. Digressing for amoment, the incorporation of a usefulfunction such as a digital clock insert onthe Channel 4 test pattern (ETP-1 type)would be extremely welcome to servicetechnicians. It would, in fact, be one of thevery few useful tests provided by thepattern. Several Continental test cardsalready display such information.

OOPS!In the article `DX -TV: Getting Started'(R&EW September 1982) we gaveconnection details for the Philips G8iselectivity module. On the diagram (seepage 41), an extra connecting pin appearedfrom somewhere. The correct data is shown

in Fig. 5. In case of difficulty in obtainingone of these modules, Hugh Cocks (CrippsCorner, Robertsbridge, Sussex TN32 5RY)can supply but minus the screening cans.An SAE should be sent with any enquiries.

RECEPTION REPORTSGraham Angel of Sheffield has been Dx-ing since May. Already he has receivedmost countries in Europe via SpE. Hislocation is one of the highest points aroundthe city and he can receive many differentIBA regions on UHF, although the localYTV relay does tend to introduce cross -modulation problems with some signals.Graham intends to obtain a Sanyo 9300VCR (fitted with a multi -band tuner) inorder to record DX reception.

Ray Davies (Happisburgh, Norfolk) wasalerted at 0400 on August 15th and henoted the NCT caption on channel IA. Healso saw the Russian '0249' test card onchannel RI around the same time. Ray usesa 26 -inch Grundig colour receiver as a DXmonitor which also acts as the maindomestic set when there is no Dx around.The receiver has been modified to enableboth the 5.5MHz and 6.0MHz soundchannels to be resolved.

Another enthusiast to participate innocturnal DX reception was Cyril Willis(Little Downham, Cambs). He too notedthe Italian pirate activity of the 15th butalmost an hour prior to Ray.

Simon Hamer (Presteigne, Powys) hassent details of recent Sporadic -E receptionwhich includes TSS and other Eastern -bloccountries. During the earlier part of theseason, Simon noted weak vision syncpulses on channel R5(93.25MHz) which liesin the Band II spectrum. Channel R5 isoften overlooked by TV-DXers due mainlyto the severe interference caused by thevarious FM radio stations. Perhaps withsuitable filtering it may be possible toreceive the 100kW transmitter at Choumenin Bulgaria on this channel. The only otherpossibility of receiving this country is viathe E3 outlet at Arbanasi but the ERP isonly 50 watts! Gone are the days of the latesixties when Bulgaria used channels RI andR2 with several kW ERP.

Finally, Robert Copeman has writtenagain with details of recent troposphericreception. Robert lives at Mount Waverleyin Victoria (Australia) and comments thatslightly improved trop conditions result inthe reception of ABRV 8 Cobden Start,GMV 11 and ABGV 5A Alexandra (allthree stations located in Victoria), ABGN11 Verilderie (New South Wales) andABKT 11 King Island in Tasmania. ViaSp.E activity, Robert has noted TVQchannel 0(46.25 MHz vision) from Brisbanein the state of Queensland. TV-DXers inthe UK have received Australian channel0 signals on several occasions duringF2 -layer activity. R & EW


Immediately Interesting 5

Possible application 6Not interested in this topic 7Bad feature/space waster 8

DECEMBER 1982 83

R&EW BOOK SERVICENEW BOOKS

POPULAR CIRCUITS: READY REFERENCE1982. 216 pages. 275 x 210mm. Paperback.

by John Markus. Stock No: 0240458 9.50

Most inveterate dabblers share an interest in the wayothers design circuits, and sooner or later begin to builda collection of photocopied abstracts from books andperiodicals.

I was fascinated to find that John Markus' collectionof electronic memorabilia, from the last 10 years or so,contains a large number of the very circuits that lurkfiled away (in a couple of binders) on the R&EWshelves marked simply 'ideas'.

The book is a well indexed and collated, and actuallyrecognizes the fact that life exists in sinusoidal form aswell as between logic levels. Markus doesn't go intothe theory of the circuits but that isn't the functionof this work.

It's a lot easier than keeping track of a wad ofphotocopies

SCHAUM's OUTLINE SERIES:THEORY & PROBLEMS OFBASIC CIRCUIT ANALYSIS1982. 340 pages. 205 x 275mm. Paperback

by J O'Malley. Stock No: 02-47820 15.95

Although basically a work intended for students of thesubject, the style is easily assimilated by anyoneundergoing a reasonable attempt at self -teaching. It

mercifully avoids higher maths; pitched at about 'A'level standard, but progressing the material just beyond.

Speaking as one who just about remembers Nelkonand Parker, this book seems to be a rather morereadable and concise approach.

Each chapter is supplied with many worked examples,plus many problems land answers) to exercise theconcientious reader's grasp of the subject. It's goodvalue for money and an excellent basic reference workfor DC and AC circuit analysis. Thevenin rules OK?

TRS-80 COLOUR BASIC1982. 378 pages. 170 x 250mm. Paperback.

by B Albrecht. Stock No: 0209644 6.75

The appearance of a rather jaunty dragon illustration,on the cover of this book, must either rate as thelucky coincidence of all time or a neat piece of insideknowledge. Ostensibly written for the Tandy ColourComputer, all good followers of the micro scene willknow that Mettoy's Dragon 32 uses the same CPU(68091 and thus mainly interchangeable software.

The book is presented as a self teaching guide withself- assessment Cl&A sessions in each chapter, capableof taking a novice through the paces of very basicfamiliarisation ("What is a ROM"), and on to somereasonably advanced concepts in BASIC. It's a bit of ashame that the author doesn't credit the reader, whohas got as far as subscripted variables and arrays, witha bit more intelligence than the style implies but

notwithstanding this gripe, the book is tailor made for

the growing band of Dragon fanciers.The index is easily driven for reference purposes.

ACTIVE FILTER DESIGN1982. 134 pages. 150 x 225mm. Paperback.

by C Chen. Stock No: 0209593 6.75

Well, what can you say about this perenially favouritesubject? Well, the bad news is that most activethinkers and enthusiasts will not be able to put thisbook down, without adding it to their collection ofactive filter reference works.

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Use the reply paid coupon for ordering.

the book is all about design, and a few more workedexamples might be helpful. Still,the indexing is

excellent.

LOCAL AREA NETWORKSNCC, 1982. 254 pages. 150 x 210mm. Paperback.

by K C E Gee. Stock No: 0223658 15.00

Not exactly cheap at the price, but nevertheless avaluable, well indexed and well presented collection ofthoughts and concepts, in the style of an 'overview' ofthe subject. It is a British book, covering such subjectsas the Cambridge Ring, Econet, plus virtually all theothers that have been mooted in connection with micro

computing.It was interesting to see the very system upon which

this is being written, described on one of the pagesKirk Gee has done a very thorough job with this bookand anyone with a serious interest in understandingnetworking will not begrudge the money.

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AMATEUR ANTENNA TESTS AND MEASUREMENTSby H D Hooton. Stock No: 0221466 7.95

BEGINNERS HANDBOOK OF AMATEUR RADIOby C Laster. Stock No: 0202156 10.20

CB RADIO CONSTRUCTION PROJECTSby L Buckwalter. Stock No: 0220952

FERROMAGNETIC CORE DESIGNby M F 'Doug' DeMaw. Stock No: 0240881

MICROWAVE DEVICES AND CIRCUITSby S Y Liao. Stock No: 02-58120

RADIO HANDBOOK 22nd Edition.by W I Orr. Stock No: 0221874

QUESTIONS & ANSWERS ABOUT CBby L G Sands. Stock No: 0220893

TV ANTENNAS AND SIGNAL DISTRIBUTIONSYSTEMSby M J Salvati. Stock No: 0221584

DESIGN OF OP AMP CIRCUITS, with experimentsby H M Berlin. Stock No: 0221537 8.70

DESIGN OF PHASE LOCKED LOOP CIRCUITS, withexperiments by H M Berlin. Stock No: 0221545 8.70

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ADVANCED COMPUTER DESIGNby J K Iliffe. Stock No: 0201125

APPLESOFT LANGUAGEby B & G Blackwood. Stock No: 02-21811

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ABC's OF INTEGRATED CIRCUITSby R P Turner. Stock No: 0221462

ACTIVE FILTER COOKBOOKby 0 Lancaster. Stock No: 0221168

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BUILDING & INSTALLING ELECTRONIC INTRUSIONALARMS New Editionby J E Cunningham. Stock No: 0221465 8.70

CHEAP VIDEO COOKBOOKby D Lancaster. Stock No: 0267221

CMOS COOKBOOKby 0 Lancaster. Stock No: 0221398

COLOUR TV TRAINING MANUAL 4th Editionby H Sams Editorial Staff. Stock No: 02 21412

COMPLETE GUIDE TO READING SCHEMATIC

DIAGRAMSby J Douglas -Young. Stock No: 02-04244

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DECEMBER 1982 85

SHORT WAVENEWS FOR DXLISTENERS Frank A. Baldwin

All times in GMT, bold figures indicate the frequency in kHz.

.dforir

`'..1\ Affij

1511111C AMA'111111 0/111110;

NW/\Wiwi" b.mtvisii.,7

Now is the time to tune yourreceivers to the LF bands and searchfor those signals from Indonesia.Reception of some of these stationsrepresents a Dx feat of no meanachievement.

Indonesia, formerly theNetherlands East Indies, lies inSouth East Asia and is comprised ofmany small islands which straddlethe equator for over 4800km, thosein the west being of volcanic originwhilst those in the east are of coral.The country is mostly under-developed, only Java showing signsof modern technology, thisincluding oil wells.

For those who wish to try forIndonesia, a few possible 'targets'are mentioned here - with more tocome next month. For UK listeners,the best chance of reception is fromaround 1500 to 1600 GMT, at whichlatter time most close down. Sign -on is around 2100 to 2200 and thistime slot provides a furtheropportunity to log some of these Dxstations.

For a start, try 4719, on which

channel RRI (Radio RepublikIndonesia) Ujung Pandang, thecapital of the Propinsi SulawesiSelatan (Selatan Province ofCelebes), which operates from 0830to 1530 (Saturday 1600) and has apower of 50kW, making it one ofthe easiest of the Indonesian to loghere in the UK.

Then there is RRI UjungPandang on 4753, it closes at 1530and has a power of 20kW; RRIMedan on 4764 which opens at 2300and closes at 1700 with a power of50kW; RRI Palembang on 4856where it opens at 2200 and closes at1600 with a power of 10kW; RRISorong on 4875 opens at 2100 andcloses at 1400.

These are just a few of those mostoften reported in the SWL press. Allof the Indonesian stations relaynewscasts from RRI Jakarta at 2300and at 1500 and at other timesthroughout the transmission periodbut these are unlikely to be heardhere in the UK. Good luck with theIndonesians.

AMATEUR BANDSWandering over these bands canprovide some enjoyment and a senseof achievement, especially when areal Dx call is logged. Not that I canmake any claims on that score,except possibly for the FR7 on

14 MHz, but it did make a changefrom roving over the variousbroadcast bands which takes mostof the available time.

As usual, a start is made with -

160 Metres (1800-2000kHz)Working on CW, as with all thebands reported here, Top Bandfailed to provide much Dx on thisreportable occasion. Mid -month didhowever produce some signals fromW. Germany in the form ofDJ8WL, DK2QL, DJ2ZX andDL300. Nothing loath, we turn to -

40 METRES (7000-7100kHz)On the few occasions the digitalreadout indicated this band wasbeing tuned - or at least the first50kHz or so - the only signals ofnote were those mostly from theSouth American area, notablyCOI RA from Cuba, the BraziliansPY I AJK, PY2RRG and PY4BWwith the Russian UD6DHC comingin at the tail end. On to betterthings, the next band visited was theold favourite of most SWL's,14MHz.

20 Metres (14000-14450kHz)It was on this band that thingsstarted to brighten up somewhat, a

start being made by logging CO1HJfrom Cuba, FR7CM fromTromelin, KH61J in Hawaii vainlycalling CQ Eur but finding notakers, KL7GU in Alaska going itgreat guns with stateside QSO's,U180AE from Uzbek busily workingEuropeans, the AustraliansVK2ALH, VK2DHF and VK5AUSall calling CQ whilst last but notleast the New Zealanders werebeginning to come through led byZL1AAG.

Graeme Caselton, G6CSY,Orpington, tells me he loggedNP4AT in Puerto Rico causing aright old pile-up of hopefuls,VK70C in Tasmania and 4N9OLYasking for QSL's via YU4EXA.

15 Metres (21000-21450kHz)Some fun and games here. Graemenoted the Japanese JAODAF,JAOWRF and JH2LTL, the latterworking into HA; 8P6OV onBarbados and on a later occasionthe Japanese JA3BOA calling CQAfrica.

For us Chile CE6CWEcommenced the proceedings,followed by CXIDZ and CX7DUfrom Uruguay, FC8TT fromCorsica, HCIVU from down therein Ecuador, HKIDBO poundingaway in Colombia, LU1DCT andLU4FGO in Argentina, NP4BN andNP4FJ in Puerto Rico, ZC4CWT inCyprus, tailing off with the SouthAfricans ZS6ANW and ZS6BWD.Not a lot of Dx I must confess butit was the best I could rake up.

10 Metres (28000-29700kHz)For myself, I failed to get on to thisband through sheer lack of availabletime but Graeme tells me he dug outthe following very interesting calls.H5AHF in Bophuthatswana (c/oZS6), OUIEHB/YB on the GolanHeights, 3X1Z sited in the Republicof Guinea - the only active amateurin that country - and 6W8AR inSenegal.

A good List Graeme and thankyoufor your support.

LOTHIANS RADIO SOCIETYMel Evans GM6JAG informs methat this society now holds itsmeetings at the Drummond HighSchool, Edinburgh (off BroughtonStreet). Meetings are held onalternate Thursday evenings andcommence at 7.30pm prompt (clocktime). Meetings at the new venuecommenced on September 9th, afull programme being planned.Further details may be obtainedfrom Mel Evans GM6JAG, 4Burdiehouse Street, Edinburgh (Tel:031-664 5403).

BROADCAST BANDSThe information listed under thisheading is correct at the time ofwriting, the various loggings beingoffered to readers as a guide to someof the stations that may be heard onthe short waves. Every month in thisarticle some attempt is made tointerest both the short wave listenerand the Dxer. The details presentedare therefore a mix of each interest.

The degree of success achievedwill depend in some measure on theequipment in use at the receving endand the conditions prevailing at thetime of listening. For some of thelow frequency band loggings areceiver exhibiting a narrowbandwidth (good selectivity) will berequired.

SpainMadrid on 9765 at 1950, YLannouncer presenting a programmeof typical Spanish music - ideal forrecording enthusiasts - during theEnglish transmission for Europe,timed from 1900 to 2000 and thenrepeated from 2000 to 2100 daily.

Madrid on 17890 at 1535, OMand YL alternate announcements inthe Spanish programme intendedfor the Americas and featured onthis channel from 1530 through to1900.

RomaniaBucharest on 11940 at 1956, OM(male announcer) with news ofinternal events in a programmeentitled 'Radio Newsreel' during an

English programme to Europe,scheduled from 1930 to 2030.

Bucharest also on 17720 at 1511,OM and YL (female announcer)alternate with comments onRomanian affairs in the Englishtransmission for Asian consumptionand timed from 1500 to 1530 on thischannel.

BulgariaSofia on 11720 at 1958, OMpresenting a programme of classicalmusic as part of the Englishtransmission to Europe, scheduledfrom 1930 to 2000.Poland"Radio Polonia", Warsaw on 9675at 2002, OM with stationidentification at the commencementof the English transmission forAfrica, scheduled from 2000 to2030. This was followed by aprogramme review and a newscast,mainly of Polish affairs.

YugoslaviaBelgrade on 9675 at 2004, OM witha newscast during the Englishtransmission to the Middle East andAfrica and scheduled from 2000 to2030.

Hungary"Radio Budapest" operating on11910 at 2007, YL presenting anewscast, mainly of internal eventsbut with some world items duringthe English programme for the UKand Europe, being scheduled from2000 to 2030.

CzeChoslavakia"Radio Prague" on 5930 at 2012,OM with a newscast of world affairsin the English transmission toEurope and timed from 2000 to2030.

Prague on 17705 at 1457, YL withstation identification at the end ofthe English programme for Africa,South Asia, the Far East and thePacific area and timed from 1430 to1500.

NetherlandsHilversum on 17605 at 1503, OMexplaining the meanings of variousEnglish phrases during the Englishprogramme for the Far East andSouth Asia, being aired from 1430to 1520. Still Holland as far as I amconcerned!

w. GermanyCologne on 21600 at 1500, YL withstation identification at the start ofthe English programme to Centraland East Africa (at least accordingto their schedule) and timed from1500 to 1550.


E.Germany"Radio Berlin International",Berlin on 21500 at 1525, OMpresenting the English programmefor West Africa. He was wasting histime, most of it was wiped out bythe jammer identifying as WD inMorse - obviously a broadcast directfrom its diesel motored generator!SwedenStockholm on 17790 at 1518, YLwith the programme in Frenchintended for Europe and NorthAmerica and timed from 1500 to1530 on this channel.

Kuwait"Radio Kuwait" on 17650 at 1954,Arabic music and songs during theDomestic Programme radiation onthis channel, timed from 0730through to 2105.

EgyptCairo on 17670 at1540, whenradiating a progamme of Arabicmusic and songs in the DomesticService which is on this frequencyfrom 1300 to 1900.

Cairo on 17690 at 1524, OMannouncer, YL with songs duringthe Hindi transmission to South andSouth East Asia, featured on thischannel from 1430 to 1530. Into theUrdu programme at 1530 and thislasts until 1700.Equatorial GuineaRadio Nacional, Bata, Rio Muni on5004 at 1917, OM with a talk inSpanish. This one operates in bothSpanish and vernaculars and is onthe air from 0430 to 0655 and from0955 through to 2200. The power is100kW but don't worry if youcannot log radio Nacional on thischannel. Try 4925 and you willprobably find it there. For reasonsbest known to themselves theyalternate to no known pattern andin addition, the frequencies can varyslightly!

ChinaCPBS Peking on 15670 at 1131, OMwith announcements then YL witha song in the Tibetan programme,part of the Domestic MinoritiesLanguage Service, this particulartongue being broadcast from 1100to 1155.

Radio Peking on 17450 at 1855,OM speaking in the Hausaprogramme to West Africa which,according to the schedule, is from1830 to 1900.

Radio Peking on 17700 at 1527,YL with an interesting talk aboutChinese history and archaeology,especially dealing with some for thelatest digs and finds. All in theEnglish transmission to South Asia,scheduled from 1500 to 1600.

Radio Peking on 11445 at 1847,YL with a talk about Chinese affairsin the Italian programme toSomalia, timed on this channel from1830 to 1900

Radio Peking on 6665 at 1958.'East is Red' interval signal onchimes, 'pips' time -check at 2000,OM station identification, 'East isRed' orchestral version - there is achoral rendering which is used bysome Chinese stations - at theopening of the Domestic Service 1stProgramme, scheduled on thischannel from 2000 to 1730.

EcuadorHCJB (Herald Christ JesusBlessing) Quito on 17790 at 1949,OM and YL with the Englishprogramme for Europe, scheduledfrom 1900 to 2000. Mainly religious.

ColombiaEmisora Nuevo Mundo Bogata on4755 at 0439, OM announcer inSpanish, local pops on records. Thisone operates around the clock andhas a power of 1kW.

Radio Guatapuri, Valledupar on4815 at 0333, OM with a newscastof world events in Spanish. Alsooperating around the clock R.Guatapuri has a power of 10kW.

La Voz del Cinaruco, Arauca isa good one to go for. Listen on4865, where it was logged at 0345when featuring a talk on internalaffairs. The schedule is from 0900to 0400 and the power is 1kW.

HondurasLa Voz Evangelica, Tegucigalpa on4820 at 0446, YL with a ballad inEnglish. This one is an old friend,quite often logged and operates tothe schedule 1030 to 0300 inSpanish, 0300 to 0500 in English andfrom 0500 to 0600 in Spanish. Thepower is 5kW.

PeruRadio Andina, Huancayo on 4996at 0451, OM with announcements inSpanish then into a programme oflocal music and songs. Anotherregular with me, this one isscheduled from 1000 to 0500 andhas a power of 1kW. It is a goodmarker for Peru, if you can hear thisone then others should be audible- providing the QRM is absent!

SurinamSRS Paramaribo on 4850 at 0342,OM's in chorus with a song inDutch, YL with a song in the samelanguage. This one operates inEnglish, Spanish, Dutch andIndonesian to the schedule 0900 to0430 (Saturday to 0530). The poweris 10kW.

BrazilRadio Nacional Cruzeiro do Sul on4765 at 0330, OM stationidentification in Portuguese then YLwith a local pop song - all colourfulstuff! This one operates from 0900to 0500 and the power is 10kW.

VenezuelaRadio Tachira, San Cristobal on4830 at 0047, OM with stationidentification followed by a talk inSpanish. Radio Tachira is on the airfrom 1000 to 0500 and the power is10kW.

NOW HEAR THISRadio Tingo Maria, Tingo Maria on4760 at 0412, OM with a song inSpanish, OM station identificationat 0416. Off at 0503 afteridentification and orchestralNational Anthem. My first loggingof this Peruvian station.

Your ReactionsImmediately ApplicableUseful & InformativeNot ApplicableComments

C,oe No53545556

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DECEMBER 1982 87

NEWS BACKGROUND

Setting standardsHeaven preserve us from 30k 1W Potentiometers....

ONCE UPON A TIME, when there wasonly the ECC82 and a handful of othervalves in virtually all types of electronicequipment from Q meters to TV sets, anelectronic engineer's life was a relatively un-complicated one.

Then someone spoilt it all by inventingtransistors, and latterly, integrated circuits.Far from getting the Nobel Prize for suchendeavours, those in the trade whosebusiness it is to try and collate and managethe hopelessly burgeoning ranges of all typesof electronic component, would rather theinventors had been on the other side of theuniverse at the time of the discovery.

Even the most feeble attempts to constrainthe imagination of designers seems doomedto failure, when circuits appear that requiresuch pointless things as 30k 1W poten-tiometers in the lower end of a long tailedpair that could not possibly dissipate morethan 50mW, and could quite happily useanything from 22K to 47K. Aarrgh!

Did you know that there are over 5,000basic types of potentiometer available thesedays? That's not actually counting the per-mutations of the actual values - simply thingslike shaft dimensions, fixing, terminations,tolerances, wattages etc.

STANDARDIZING STANDARDSTo top all this, there now seems to be com-petition between various authorities whohave set themselves up to implement 'stan-dards' to see who can produce the greatestvolumes of paper, and the most detailedtrivia. Most countries now have their ownstandards and approval systems, frequent-ly one inspired by the military, one by thetelecommunications authorities, and one bytrade associations, several by broadcasters- and several inspired by some meddlingcombination of all these. It's good news forpaper manufacturers and computer databasemanagers, but no-one else.

However, one of the most persuasive stan-dards in the UK appears to be the one thatis based on the availability of parts. The manwho designed -in the aforementioned 30k 1Wpot probably leaned over his junk box, andspotted this item floating near the top.

`Let's give that a bash', he probablythought.

And so he did, and thereafter it becameenshrined on the parts list. One or twofamous broadline component distributorshave benefitted enormously from the 'lineof least resistance' (excuse us) approach tocircuit design, and whilst this is notnecessarily a pointer to elegant academicdesign, it is a laudable recognition of thereality of actually trying to find 'standard'parts in this day and age.

88

pprua/NEW Gu1MEA

77:017-;,

.S /(NOW THE ay, You "a -RA/ -

boob epvinITY RA0 rive Mper PRae..TWAr's W( cove WE Doter- Srac,e

THE COUNTRY GIRLThere is some evidence that this om-nipotence has gone to the head in somecases, leading to a policy whereby eng-ineers find themselves in the positionof Max Miller's famous Country Girl of'ave it - and like it'. The result is cer-tainly not the most cost effective solu-tion, but one that suits the purveyorsof parts very nicely.

Radio & Electronics World tries hard towork to within the constraints of parts thatare available and cost effective. They maynot be from the schedules of BS9000 (do youknow how long approval can take, and howmuch it reflects in the cost of the part?), butthey are actually quite suitable for the pur-pose. At the danger of being tedious, darewe suggest that R&EW recognition/approvalis a reasonable indication that a part is notonly suitable for a 'normal commercial ap-plication' within the manufacturers statedlimits, but that it represents good value (ajudgement based on the combination ofquality and cost) into the bargain.Something that no other standard seems totake into account.

In fact, this seems like such a good ideato us, that it may be an area where we cancontribute to the confusion existing over theapproval of components - and so we aim totake a look at a few selected ranges of com-ponents and see if this might not be a usefulcontribution to the debate. We wouldnaturally be delighted for your brandednominations. This is not a 'distributorsurvey', but a product survey, so please letus have the component manufacturer'sname whenever possible.

OFFERINGSThis publication has always beenrather keen on the occasional reader offer -and as the Christmas season approaches, itseems appropriate that we should wheel ina few of the goodies that have passed our wayin case loved ones are still trying to think ofsomething suitable to buy for you.

The high quality Japanese auto -rangingdigital multimeter offer with this issue isstrictly limited to the first 100 orders,although judging by the rate at which theoffer stock is being depleted by contributorswho drop by, and others with an eye forvalue, you'd better make your minds upquickly.

The other offer is our perennial NiCadbattery bonanza. We have now included acouple of useful accessories in the shape ofthe battery adapters that allow you totranslate various types of battery to help outin an emergency - or to take advantage ofthe fact that 2.2Ah C cells are actually rathermore substantial than consumer (the sortyou usually find in the Sunday Supplementads) D Cells at 1.2Ah, and about the sameprice!

The battery tester is a marvel of HongKong value -for -money. Like the multimeter,to see one is to want one, and most membersof staff and visitors have added one to theircollections.

BOOKS, BOOKS, BOOKSAnother R&EW service that has beenpopular since we started it, is the BookDepartment. One of the original planks inour 'launch' platform was that magazinesshould not get bogged down in material that


NEWS BACKGROUNDis best read in textbooks: so we have triedto provide a useful assortment of books toprovide the foundations which any seriousenthusiast or engineer is going to needsooner or later.

We have tried to be slightly different inour ranges of titles and our general approachto the method of selection, although in thecourse of trend setting, it's inevitable butflattering to find others doing the same. Wehave now started to build up a new seriesof books from the enormous range offeredby Wiley and McGraw-Hill, and we arepleased to say that REWTEL is now beingfed with a `BOOKTEL' database that willhelp you select exactly the type of book youneed. If you don't yet plan for your own ter-minal - then we will be pleased to give youa printout of BOOKTEL listings that coverstitles in the areas you are interested in: watchthe book pages for details of the commence-ment of this service.

The standard REWTEL access techniqueis ideal for finding books containing the sub-jects you're interested in - and the page ofinfo we can provide is just about enough tohelp guide your choice - or so we hope.Whilst we will not be able to afford to carryall the books ex -stock (yet) we have arrang-ed a very expeditious shipping service thatmeans that all the Wiley titles can be orderedfrom us for delivery in 7 days.

FREE MONEY:HEADS YOU WIN, TAILS YOU WINAfter the hard sell, now for the hard buy.We occasionally remind you lot that R&EWis unique amongst electronics publicationsin that we actually supply free componentsto applicants with a reasonable propositionfor a design project that will eventually bepublished somewhere. Not necessarily inResPEW, although we would naturally likefirst refusal, just as long as something wor-thwhile and interesting gets disseminated toas wide an audience as possible. We can helpwith practical information, books, copies ofarticles, computer time etc as well as the

basic bits.Apart from the free hardware, we pay an

average of f50 per page of project material(including the diagrams etc), and that goesfor worthy design ideas, software featuresetc.

We are pleased to report that there is asteady increase in external submissions, butthere is always room for plenty more. If youdon't fancy yourself as a writer (or like somany potential authors, claim you do not`have the time'), then do not despair, sincewe are frequently required to write the wordsworking from a fairly rough-and-ready setof notes. What we need are:1) A circuit digram where component

values are clearly marked.2) A complete parts list that agrees with

the circuit diagram.3) A prototype - which need not be the

last word, but just adequate for us toengineer a 'presentable' version. Infact, it's quite likely that we will wantto incorporate a few changes andfeatures if we haven't been previouslyinvolved with the proposed project, soit's just as well to submit the itembefore you go too far towards a totallyrefined item.

4) Printed circuit layout. Again we canhelp here, but it is usually a greatdeal more satisfactory if you can getto grips with this aspect, since there isno-one as well qualified as theoriginal circuit designer when itcomes to the transfer of paperwareand prototype lash -ups to a neatPCB. The bits to do it professionallyon 2:1 tape system are free from usonce you get to this stage of thedevelopment, and the skills you willacquire will be invaluable in futureendeavours.

5) We would like details of anyreferences (books, articles etc. youhave used).

Despite this unprecedented philanthropism,we really don't have enough takers. The

scheme would seem to be ideal for collegeand university projects - yet we have onlyhad a handful of enquiries from thesequarters.

We are considering expanding the schemeto support software projects as well (whichcould entail free access to our computers andperipherals at weekends), and all we ask isa simple outline of your project, stating thefollowing:a) Your name and address.b) A summary of the project you wish to

undertake, block diagrams will do atthis stage.

c) Details of any previous experiencethat you have had that seemsrelevant.

d) An undertaking that you will use yourbest endeavours to complete the pro-ject, even if the conclusion is onlythat the original idea was not feasible!

e) If you are in full or part time educa-tion, and intend to use the sponsoredproject as coursework, a brief notefrom your teacher/tutor indicatingacknowledgement that the project willnot interfere with any other formalwork.

That doesn't seem like too much to ask, doesit? We place no formal limit on the amountsinvolved, all cases are assessed on merit. Ifyou would rather just get on and submit theproject without any 'commitment' from thesponsorship aspect, then remember that wewill also be happy to refund you for all com-ponents in connection with the project thathave been purchased from the WR&Ecatalogue. Just keep the receipts.

R&EW



EVENTS: MOBILE RALLIES November 1982November 6th North Devon Mobile Memorial Hall, Bradsworthy

RallyK J Nicholls, C8MX1Tel: 040 924 202

November sees two Hobby Electronics shows both in London and within days of each other. Bothshould be worth a visit and watch out for R&EW at the Electronic Hobbies Fair stand. Details ofthe two shows are as follows:

November 10-14 Breadboard

November 18-21

The Royal Horticultural HallsVincent Square, London,SW I.

Electronic Hobbies Alexandra Pavilion, London.Fair.

DECEMBER 1982 89

Digital inverters, buffers and logic gates

can be built in either IC or discrete form. Which typeshould be used in a particular application? Ray Marstonanswers this and many other 'logic' questions in the

next few pages.

Figure 1: (a) Standard symbol and (b) truth table of a digital inverter,with (c) a resistor -transistor version of the unit.

(a)

(b)

IN

IN OUT

IN OUT

0

1

0

1

OUT

(c)

Figure 2: (a) Symbol and (b) truth table of a non- inverting bufferstage, which can be made by (c) cascading two inverter stages.

90

PULSE INVERTERS, BUFFERS and GATES are the most basicelements used in digital electronics. When designing complex digitalcircuits, it is often necessary to work out the most economic orcost-effective method of implementing these elements. Sometimesit's best to use discrete components (diodes -resistors -transistors)to make an element, and at others it's best to use a dedicated CMOSchip. How do you make the choice? We'll expain that in the nextfew pages.

The best known logic gates are the OR, NOR, AND, NAND,EX -OR and EX -NOR types. Less well known is 'majority' logicwhich, as the name implies, gives an output only when the majorityof an odd number of inputs are high. Majority logic is useful in'voting' and pseudo -intelligent applications, such as decision -making in robotic and security systems. We give comprehensivedetails of all these types of logic in the present edition of 'DataFile'. Read on.

BUFFERS AND INVERTERSThe most basic type of digital circuit is the simple pulse inverter.Figure la shows the standard circuit symbol of the inverter, andFig. lb shows its truth table; Fig. Ic shows a discrete resistor -transistor version of the inverter. In digital circuits, input andoutput signals are either at zero or logic -0 values, or at the fullsupply -rail voltage or logic -1 value. Thus, in Fig. Ic, when the inputis low (at logic -O) the transistor is cut off and the output is pulledhigh (to logic -1) via R2, and when the input is high the transistoris driven to saturation and the output is pulled to zero volts. Theimportance of the Fig. lb truth table is that it illustrates thisinformation in short -hand form.

The standard inverter is the most versatile of all logic elements.It can be used to convert an OR gate to a NOR type, or vice versa,or to convert an AND gate to a NAND type or vice versa. A pairof inverters can be used to make a bistable, monostable or astablemultivibrator, etc. Usually, a practical inverter has an inputimpedance that is high relative to its output impedance, and canbe used as an impedance 'buffer'.

Not all buffers are of the inverting type, and Fig. 2a shows thestandard circuit symbol of a non -inverting buffer stage, which canbe made by cascading two inverting elements as shown in Fig. 2c.

Inverters and buffers are available in dedicated CMOS IC form,and Fig. 3 gives details of five popular examples. The 4041, 4049and 4069 types use the unbuffered (UB) low -gain form of CMOSconstruction, and the 4050 and 4502 use the high -gain bufferedform of construction.

The 4069UB is a simple general-purpose hex inverter, housedin a 14 -pin package, and has 'standard' output drive capability.The 4049UB hex inverting buffer and the 4050B hex non -invertingbuffer, on the other hand, have high output drive capability andare specifically intended to drive TTL loads; they can accept inputsignals far greater than the supply voltage, so can be used to givesignal -level translation between CMOS and TTL circuits.

The 4041UB also has high output -drive capability and can beused to drive TTL, but cannot accept input signals greater thanits supply voltage. The device is a quad invert/non-invert buffer.If, for example, an input is applied at pin -3, an inverted outputis available at pin -2 and a non -inverted output at pin -1.

The 5402B is a hex inverting buffer capable of driving TTL loads,and has a tri-state output which can be selected via pin- 4; whenpin -4 is low the IC gives normal inverting operation, but when pin -4


7

OV

+3 TO 18V

J14

4069UBHEX INVERTER

13

12

11

10

+3 TO 18V

4041U8QUAD INVERT/NON-INVERT

BUFFER

+3 TO 18V

4049U8HEX INVERTING BUFFER

450213TRI-STATE HEX

INVERTING BUFFER

16

15

14

13

12

11

10

+3 TO 18V

INHIBIT

.3 TO 18V

NC

4 44

48

ov

4

4

NC

'-- 16

15

14

- 13

12

11

10

40508HEX NON -INVERTING

BUFFER

NORMALLY PINS 4 AND 12 AREGROUNDED. IF PIN 4 IS HIGH,THE OUTPUTS GO INTO THE

v"' HIGH -IMPEDANCE TRI-STATE MODE.

IF PIN 12 IS HIGH, ALL OUTPUTSGO LOW (IF NOT IN THE TRI-STATE MODE)

Figure 3: Five popular CMOS inverter and buffer ICs.

is high all outputs go into the high -impedance tri- state mode. TheIC also has an INHIBIT control terminal (pin -12), which isnormally held low but which drives all outputs to ground (in the'normal' mode) when pin -12 is taken high.

The basic guidance rules for using inverters and buffers inpractical circuits are simple. If you need a large number of stages,use as many dedicated ICs as necessary. If you get to the pointwhere you are short of just one or two stages, see if you can makethem from spare stages of existing logic ICs (we'll show how later)or, failing that, consider using simple resistor- transistor stages ofthe Fig. Ic type.

OR & NOR GATESFigure 4a shows the standard symbol of a 2- input OR gate, andFig. 4b shows its truth table. As indicated by its name, the outputof the OR gate goes high if any of its inputs (A OR B, etc) go high.The simplest way to make an OR gate is to use a number of diodesand a single load resistor, as shown in the 3 -input OR gate or Fig.5. The diode OR gate is reasonably fast, very cost effective, andcan readily be expanded to accept any number of inputs by addingone more diode to the circuit for each new input.

Figure 6a shows the standard symbol of a 2 -input NOR gate(which functions like an OR gate with an inverted output) and Fig.6b shows its truth table. Figure 7 shows how a diode OR gate canbe converted to a NOR type by feeding it's output through atransistor or IC inverter stage. Figure 8 drives this lesson homeby pointing out that an OR gate can be made from a NOR gateplus an inverter and a NOR gate can be made from an OR gate

A OUT

A

0

0

1

1

B OUT

0

0

0

(b)

Figure 4: (a) Symbol and (b) truth table of a 2 -input OR gate.

Figure 5: 3 -input diode OR gate.

DECEMBER 1982 91

PROJECT

A B OUT

0 0 1

A0 1 0OUT

0 0B

0

(a) lb)

Figure 6: (a) Symbol and (b) truth table of a 2 -input NOR gate.

Figure 7: The diode OR gate can be converted to a NOR type byfeeding its output through a transistor or IC inverter.

plus inverter. Figure 9 shows that a NOR gate can be made to actas a standard inverter, and an OR gate can be made to act as anon -inverting buffer, by either grounding all but one of the inputsor by connecting all inputs in parallel.

Figure 10 gives details of three popular CMOS OR gate ICs, the4071 quad 2 -input type, the 4076 triple 3 -input type, and the 4072dual 4 -input type. When using IC OR gates, note (Fig. 11a) thatthe effective number of inputs can be reduced by grounding allunwanted inputs, or can be increased (Figs. I lb and 11c) by addingmore OR gates (either integrated or discrete) to one of the inputs.

Figure 8: An OR gate can be made from a NOR gate, or vice versa,by taking the output via an inverter.

Figure 9: A NOR gate can be converted to an inverter, and an ORgate can be converted to a non -inverting buffer.

Figure 12 gives details of five popular CMOS NOR gate ICs.The 4001, 4025 and 4002 are quad 2 -input, triple 3 -input and dual4 -input devices respectively. The 400013 contains two 3- input NORgates and a single inverter, and the 4078B is an 8- input gate thatgives an OR output at pin -1 and a NOR output at pin -13. Notethat, since a NOR gate is equal to an OR gate with an invertedoutput, the effective number of inputs of a NOR gate can beincreased or reduced by using the techniques that have already beenshown in Fig. 11.

Figure 13 illustrates a simple example of logic design using ORand NOR gates and inverters, the aim being to design a simple low -power tone generator (using a PB-2720 acoustic transducer) thatcan be activated via any one of four inputs. Look first at Fig. 13a.At first sight, the design seems to call for the use of a 4 -input ORgate, with its output feeding to a gated tone generator. A suitabletone generator can be made by connecting a 2 -input NOR gate andan inverter in the standard astable configuration shown, but thisastable is gated on by low input signals, so (in Fig. 13a) the required

4

7

+3 TO 18V

4017BQUAD 2 -INPUT OR GATE

13

12

11

10

7

OV

40758TRIPLE 3 -INPUT OR GATE

3 TO 18V

14

13

12

11

10

4

5

6

+3 TO 18V

7rrcOVA

NC

13

12

11

10

NC 8

40728DUAL 4 -INPUT OR GATE

Figure 10: Three popular CMOS OR -gate ICs.


FEATURE

Figure 11: The effective number of Inputs of a CMOS OR gate canbe reduced (a) by grounding all unwanted inputs, or increased(13 or c) by adding more OR gates to one of the OR inputs.

circuit action can be obtained by interposing an inverting stagebetween the output of the 4 -input OR gate and the input of theastable. The Fig. 13a design thus calls for the use of three ICs.

Figure 13b shows a simple rationalisation of the Fig. 13a circuitwhich enables the IC count to be reduced to two. Here, the 4 -inputOR gate plus inverter of Fig. 13a is replaced by a 4 -input NORgate, and the inverter section of the astable is made from a 2 -inputNOR gate with its inputs shorted together.

Finally, Fig. 13c shows how the design can be further rationalisedso that it uses only a single IC (a triple 3 -input NOR gate) anda couple of diodes. Here, the astable is made by converting a 3 -inputNOR gate to a 2 -input type by shorting two of its inputs together,and by shorting all three inputs of another gate together to makean inverter, and the input gate of the circuit is converted to a 4 -inputtype by connecting a 2 -input diode OR gate to one of its inputs.

Figure 13: Low -power tone generator activated by any of four 'high'inputs. The 'over -designed' version shown in (a) uses three CMOS IC.,but the rationalised design shown in (b) uses only two CMOS chips.In (c) the design is further rationalised so that it uses only a single IC.

Continued next month R & EWYour Reactions

L

Circle No. Circle No.Immediately Interesting 112 Not Interested in this Topic 114Possible Application 113 Bad Feature/Space Waster 115

.3 TO 18V

12

11

10

7 8

OV

40018QUAD 2 -INPUT NOR GATE

.3 TO 18V

1143 TO 18V

14

2 13

3 12

4 4

10 5

6 NC

7 8NC 8

OV(NZ

40008DUAL 3 -INPUT NOR GATE

PLUS INVERTER

40258TRIPLE 3 -INPUT NOR GATE

.3 TO 18V

407888 -INPUT NOR/OR GATE

40028DUAL 4 -INPUT NOR GATE

+3 TO IBV

Figure 12: Popular CMOS NOR -gate ICs.

DECEMBER 1982 93

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CHARTS AND ABACS. Set of five withinstructions for quick calculations of OhmsLaw, inductance, capacity, resistance, etc.Only £5.00, including postage from: G.W.Services, IA Grosvenor Crescent,Dartford, Kent, DA1 5AP.

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S/HAND MOBILE RADIOS for sale.High band and low band. Westminsters,Cambridges, Vanguards and many others.Box No. REW30.

TRIUMPH DOLOMITE SPRINT 1977.Taxed to December 1982, M.O.T. May,1983. Sundym glass, Westabo Sun Roof,cloth interior, overdrive and radio. Yoursfor £1,395. Tel: Brentwood (0277) 214406after 5.30.

AERIALS: TELEVISION, RADIO, CB,(91-elem. wide band UHV DX aerials),Masthead amplifiers, poles, brackets,towers and CB radios. London's cheapest!AAC Ltd., 132 Hermon Hill, London E18.Telephone 01-530-6118.

POWER MOSFET 4-400W Driver Module50 x 50 x 30mm with instructions. £7.00.Vicelec, 30 Crosby Road, Southport,Merseyside, PR8 4TE.

AUDIO: VIDEO: DATATRANSMISSION. Professional gradecables from TRANSOUND/FILOTEX.Made by Europe's premier cablemanufacturers. Example: EHEA shieldedtwin -twisted 'easy strip' audio cable (onceused you will use no other (100 metres£25.00. Total which includes p&p and VAT(UK only). CWO. For data sheets, largequantity discounts, exports, etc. SAE to:Transound International Electronics Ltd.,PO Box 148, Welwyn Garden City, Herts.Or telephone 043-879-262.

G4BVS COMPUTERISED MORSETRAINER for Apple II (48K DOS 3.3).Sophisticated program allowscomprehensive structured training in bothreceiving and transmitting morse code invarious modes/speeds/pitches. Automaticscoring and instantaneous visual fullyG4BVS/REW, 22 Highland Road,Amersham, Bucks HP7 9AX, or £9 toinclude disk.

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PRINTED CIRCUIT BOARDS &LABELLING Designer and manufacturerto freelance and industrial users. Try mefor: Conventional signal and double sidedPCB production (non PTH) handproduced artworks and photography.Quickly made prototypes. Self adhesiveprocess printing. - G.N. Slee, 78 DerryGrove, Thurnscoe, Rotherham, SouthYorkshire, S63 OTP. Phone: (0709)895265.

AVO VALVE Characteristic Meter 163. 4years old. Immaculate condition. Currentprice £1400.00 plus. Will accept reasonableoffer. Phone Swansea 0792-69841.

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RF3100L Panasonic double superhet, 32wavebands, synthesised PLL, crystalcontrolled. Brand new. £165. PhoneEdwards, Chard, 046-06-2848.


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RANK TX/RX RADIOS, pair of pocketsize professional units, 4 channels PMRband incl. charger, handbook. £55. PhoneCheltenham (0242) 581667.

FRENCH B/W TV PHILLIPS TP412with preamp and aerials for Brest. £40.Telephone St. Austell (0726) 3608.

MTL HUNTRON TRACKER 1980 modelfor repair centres, computer servicing.Good condition. £400 ONO. Box No.REW29.

FRG -7 with 2400Hz SSB filter £140.Microwave modules, receive converters for70cm, 2m, 4m £22 each, or receiver andconverters, as one lot £200. L 3 Devaney,phone 01- 579-2424, x2565, day time only.

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Two stories concerning those keepers of the telecommunicationsmonopoly, the newly born British Telecom, nee the GPO. The firstconcerns a visit to the most phallic of London's tourist attractions,the Post Office, sorry, Telecom Tower. The excuse for the visitwas the handover of various sound and vision links to the newChannel 4 TV set up which, by the time you read this, will beoffering a nightly dose of radically different TV programmes.These, judging by the promotional material that has appeared todate, consist of soap operas, court room dramas, historical playsand news - if this sounds much the same as the offerings of thepresent networks, fear not for there will be a difference. We canexclusively reveal that the reason that music drowns out thesoundtracks of all the clips from Channel 4 programmes, is thatITV's intellectual channel will consist of material spoken exclusivelyin Franglais, a language that has found wide acceptance amongthinking readers of the 'Sun'.

Back to the BT Tower, however, and the hand over of theChannel 4 distribution system. The hand over itself featuredspeeches from the big white chiefs of Telecom and, via the newnetwork, Channel 4's Jeremy Isaccs from their Charlotte St studios.You may have guessed that this was destined to be a boring affairas indeed it was. As the hard stuff was being held over until afterthe ceremony, there was a general wish to get things over with.

The offer of a tour around the switching centre at the end ofthe speeches was taken up by most of the technical journalistspresent, including the R&EW representative - we like to showwilling - and off we went to the switching room.

Here the mysteries of pushing switches at the correct time wereexplained (a large clock is the secret behind BT's success in thisarea) and our guide indulged in a gentle bit of back slappingpointing out that the general public were not aware of BT's rolein our country's TV networks. At this point the R&EW personpointed out that the Telecom's staff threat to pull the plug on BBCand ITV during any industrial dispute, meant that many of the

public were aware of BT's involvement. The guide glared andignored the question.

The very next day, as part of the TUC's day of action/inactioncampaign, most papers carried an item about the threat from BTengineers to pull the plug out during prime time TV. Point made.

One other titbit of information was that the restaurant at thetop of the tower (nearer the end of the universe than most eateries)might re -open in the near future. It was closed some time ago asit was thought to be too tempting a target for bombers and othernasty people.

A number of ideas for reopening the venue were considered -a conference centre would be ideal but for the fact that the circularshape of the tower, and its central service shaft, would make anypresentation/discussion, almost impossible.

The idea most in favour was a fast food joint, with an externallift for ferrying customers up the side of the building. Who's fora Buzby Burger?

FLYING HIGHNothing to do with electronics this, but a warning for those of youwho have not taken to the skies yet. Judging by the image projectedby the airlines, airtravel is a sophisticated form of travel, a cutabout land bound transport in all senses of the word.

In fact, according to one member of the R&EW staff, flyingis a very overrated experience. The feeling on take off was saidto be somewhat akin to sitting on board a rather overcrowdedLondon transport bus whose driver had positioned said vehicle atthe start of the M l prior to flooring the accelerator and hopingto God that the thing took to the air. Of course the bus won't takeoff and a plane, usually, will. At any rate, flying was thought tobe very much a thing for the birds.

1HE LAST WORD.

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Gould Instruments 85


e ELECTRONICIGNITION KM

Two years ago we launched the Total Energy Discharge System, we knew itcould outperform any competing system and the sales have proved just howgood it is. With thousands of systems sold in over 30 countries around theWorld, from the cold of Norway to the tropical heat of Singapore, thesystem is an outstanding success.THIS IS WHAT MAKES TOTAL ENERGY DISCHARGE SO GOOD-

ta tBroneakecr

T 1

BLOCK A Li

BLOCK B

BLOCK C

Circuit Diagram

The discharge circuit in block A is the heart of the system. It looks simplebut outperforms any other by far. A 2 I/ F storage capacitor (twice the usualsize) charged to + 370 volts, is discharged into the ignition coil primary bySCR1, providing a high energy pulse of the correct polarity. Long after thestorage capacitor is discharged, the current in the ignition coil is sustainedby 'flywheel' diode D4, preventing energy flowing back to the capacitor andgiving 3% times the spark energy and duration. Instead of relying on theeffects of coil 'ringing', inductor L1 commutates the SCR, giving completefreedom from the usual latching problems and allowing the storage cap-acitor to be recharged whilst the discharge current is still flowing in the coil.

Block B is the trigger circuit and provides faultless spark timing. The emitterof TR1 is biased from the supply to provide a variable trigger threshold,allowing triggering with the supply down to about 3.5 volts but rejectingnoise and signals from contact shuffle and vibration. Capacitor C3 and itsassociated resistors provide a variable inhibit period, after the contacts close,which filters out extreme contact bounce on 4 cylinder engines yet stillallows 8 cylinder operation to over 7500 rev/min. In effect the longer thecontacts stay open the longer they must remain closed before the nextspark can be triggered. (Be warned:- untimed sparks can seriously damageyour engines health).

Block C is the inverter, the power behind the spark. It's a 'ringing choke'type. Well designed, this type can not only be regulated and charge thecapacitor from zero volts, effectively a short circuit, but is also more effic-ient than the traditional push-pull type. Even though it provides around 3times the power, it still doesn't need the usual finned heat sink. TransistorsTR4 and TR5 regulate the invertor output, by controlling the amount offeedback, and are in turn controlled by TR3 which compares the voltageon the storage capacitor with the reference zener D5. The output voltageis set by the zener voltage so the full output is available over the wholesupply voltage range, a powerful spark is produced even with the batterydown to 4 volts.

These are the more obvious features, there are many more details like theabsence of 'spikes' and low di/dt and dv/dt applied to the SCR, which to-gether with top quality components make Total Energy Discharge not onlya top performer but far more reliable.

This advanced circuitry gives all the well known advantages of the bestcapacitive discharge systems:Peak Performance; Improved Economy; Fires Fouled Plugs; AccurateTiming; Smooth Performance;PLUSSuper Power Spark; Better Starting; Optimum Spark Duration; CorrectSpark Polarity; L.E.D. Static Timing Light; Low Radio Interference;Designed In Reliability.

Information disclosed above does not imply any freedom from patent orcopyright of Electronize Design.

Electronize Total Energy Discharge Ignition issuitable for use with:ALL 6 and 12 volt negative earth vehicles

fitted with a conventional contact breaker and coil system.

ALL Ballast resistor (cold start/low voltage)systems.

ALL Voltage triggered electronic tachometers.(Some older current impulse types (Smithspre 1974) require an adaptor)

ANY Number of cylinders up to & including 8.

SPECIFICATION(using a typicalignition coil)

Spark PowerSpark Energy

(stored energy)Spark DurationOutput Voltage

clean spark plugfouled spark plug

Voltage Rise Timeto 20kV

TOTAL ORDINARYENERGY CAPACITIVE

DISCHARGE DISCHARGE

140W 90W36mJ 10mJ135mJ 65mJ500pS 160pS

38kV 26kV26kV 17kV

25jS 30jJ S

You can buy your Total Energy Discharge system asa ready assembled and tested unit ready to fit to yourcar or as a comprehensive kit of parts containingeverything required, even a length of solder and atube of heat sink compound. The kit comes completewith detailed, easy to follow instructions which enableeven a beginner to assemble a kit in just a matter ofhours.The same top performance system is also available,in ready assembled or kit form, to suit cars andmotorcycles fitted with twin ignition systems.

STANDARD UNITAssembled and Tested

STANDARD UNIT KIT

TWIN OUTPUT UNITAssembled and Tested

TWIN OUTPUT KIT

£26.70

£15.90

£36.45

£24.55

All systems are available direct from the manufacturer.Prices include VAT, postage and packing £1.00 extra.Access and Visa cards are welcome, just write or tele-phone quoting your number.

VISA

ELECTRONIZE DESIGNDept H Magnus Rd Wilnecote

Tamworth B77 5BYtel 0827 281000

SOMEDAY, ALLCOMPONENTS WILL BE

SOLD THIS WAY!

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