SEPTEMBER 1987 £1.40

NEW ZEALANDNORTH AMERICA $2.95

AUSTRALIAHOLLAND

D71699

e 1411CThe communications and electronics magazine World

[Manufacturers, importers and suppliers of world famous communication products584 HAGLEY ROAD WEST OLDBURY, WARLEY, BIRMINGHAM B68 OBS021-421 8201/2/3. CELLNET 0860 323056. PRESTEL MBX 214218216 FAX 0215614074Amateur Radio. Business Radio, Radio Telephones, Sales, Service Accessories and antenna systems.

R. WITHERS COMMUNICATIONS LTD

ICOM YAESU

IFIAAPRICES DOWN - - Due to better exchange rates - we can now offer

NEWS FLAS many brands at reduced prices for a change. prices are coming down - -this rarely happens time to take advantage9 Compare our prices - some amazing reductions on Hand Helds reductions on scanners - -popular models at the moment are -

FRG9600 Mk 1/2/3 - - FT209R - - FT23R FT73R FT727R - FT767 _ FT757 Mkt -All at lower prices than the competition - _ call now

°Y- THE TECHNICALLY ORIENTATEDRADIO COMMUNICATION

SPECIALIST

* HANDHELD TRANSCEIVERS *WE OFFER MORE TO CHOOSE FROM . .* Extended RX available, TX for Export Only

* KENPRQ KT220EE 2MTR 5W LCD H/H £199.00 P/P £10.00KENPRO KT400EE 70CM 2W H/H £199.00 P/P £10.00

* CTE 1600 2MTR 3W (SAME AS IC2E) £165.00 P/P £10.00* ICOM MICRO 2E 2MTR 2.5W EXT RX £229.00 P P £10.00* ICOM IC28E 25W MOBILE EXTD. RX £349.00 F' P £10.00* YAESU FT209R 2MTR FNB3 NICAD £199.00 P/P £10.00

YAESU FT29OR MK1 2MTR M MODE £319.00 P P £10.00YAESU FT29OR MK1 C VV NICADS £339.00 P P £10.00YAESU FT29OR MK2 2MTR M/MODE £399.00 P/P £10.00YAESU FT690R MK2 6MTR M/MODE £369.00 P/P £10.00YAESU FT690R MK2 C/W NICADS £389.00 P/P £10.00

* FT23R 2MTR HANDHELD ENB10 inc charger £239.00 P/13- £10.00* FT73R 70CM HANDHELD FNB10 inc charger £249.00 P/P £10.00

FT727R DUAL BAND HANDHELD £385.00 P/P £10.00

* BASE STATIONS *YAESU FT26R WITH 2M £799.00 P/P FREEYAESU FT757GX MK 1 £749.00 P/P FREEYAESU FT757GX MK 2 £899.00 P/P FREEICOM IC275E 2M BASE STATION (Probably the best 2m Base Station available) £899.00 P/P FREEF1767 Super multi band base station £1390.00 PP £10.00

FULL RANGE OF MATCHING ACCESSORIES IN STOCK* SCANNING RECEIVERS *

WE OFFER THE LARGEST RANGE AND OPTIONSYEASU FRG9600 MK1 60-905 MHZ £459.00 P/P £10.00YEASU FRG9600 MK2 60-950 MHZ £499.00 P/P £1000YEASU FRG9600 MK3 100 KHZ-950 MHZ £599.00 PP £1000

* YAESU FRG9600 MK3 PACKAGE: *MK3 Receiver. ICOM AH7000 Super Discone Antenna. PA4C AC Adapter. 1 2 size G5RV. CompleteH/F-UHF BroadcastAmateur PMR Receiving Station £699.00 inc. carriage. Options: PAL Video Unit ,/, £27.50,BBC CONTROLLER PROG. £49.50 inc. post. Existing owners please note we offer extended coverage. improved sensitivity. HPmod. sae or phone for more details

* ICOM ICR7000E *25-1300MHZ SPECIAL PRICE £862.50 carr. £10.00. ICR7000E with AH7000 antenna at £942.50. carr. £10.00.

THE WORLD'S BEST KNOWN SCANNERS, DIRECT FROM THE DISTRIBUTORSBearcat Scanners are value for money and the most popular

* BEARCAT *UBC100XL LB/AIR BAND VHF UHF Handheld £219.00 POST FREEUBC175XL as above. desk -top FREE DISCONE £209.00 POST FREEFDK AIR BAND SYNTHESIZED RH 118-136 MHZ £139.00 POST £3.00FDK VHF -FM SYNTH. 1-1/HELD 139-174 MHZ £145.00 POST £3.00REGENCY HX850 AM -FM VHF -UHF 1-1/1-1 SCANNER £235.00 POST £3.00REGENCY MX7000 AM -FM VHF -UHF D.TOP SCANNER.. £399.00 POST £5.00

(Coverage the same as the AOR2002)

WE STOCK ALL CURRENTLY AVAILABLE MAKES OF SCANNING RECEIVERS* SPECIAL MOBILE ANTENNA OFFER *

SUN KG309SE2 5/8 Ant ow Moulded S0239 Lead and guttermount assy £20.00 inc post* 6 METERS *

SPECIAL OFFER for PYE A200 Linear Amplifiers. We have various models available. Tested working with 3 month guarantee. For 4m. 6mand 2m. .5W to 10W input, 10-60W output. All modes, mod kits available for 6m conversion.Prices range from £39.00 P/P £3.506M DIPOLE KIT £9.50 P/P £3.00Important. Please contimi your order before sending payment as we do not wish you to be disappointed d the rruJel you require is sold out or the pnce has gone up' Special offers are subtect toavailablity we DO NOT advertise products or models that are NOT normal stock ,tems The above otters will be sold on a first come first served basis Please DO NOT DELAY as with previousoffers we always get hundreds of enquiries when the otters are SOLD OUP instant Credit available Subject to StatusMail Order welcome. you may order by Access. Visa. Diners Club. Amex or CWO for immediate despatch. Please call for further details or brochures. Prices variable and aresubject to change without prior notice.

ALL PRICES CORRECT AT TIME OF GOING TO PRESS. EWE.

Tel: 021 421 8201 (24hr answerphone)

Telex: 337676 G TELEX -G71-71rirrr

M EIREERc

CONTENTSEditorJane Berry

Assistant EditorAnita Ley

Editorial AssistantLisbeth Stedman

Advertisement ManagerMarian Vidler

Advertisement ExecutiveKaren Turner

PublisherPeter Williams

Published byRadio & Electronics WorldMagazinesSovereign HouseBrentwoodEssex CM14 4SEEnglandTel: (0277) 219876

ISSN0262-2572

PrintedIn Great Britain

Newstrade salesArgus Press Sales &Distribution Ltd12-18 Paul StreetLondon EC2A 4JSTel: 01-247 8233

SubscriptionsTei: 01-760 0409

0 Copyright 1987Radios ElectronicsWorld Magazines

Safety in the shackSome of the constructional projectsfeatured refer to additions ormodifications to equipment; pleasenote that such alterations may preventthe item from being used in itsintended role, and also that itsguarantee may be invalidated.

When building any constructionalproject, bear in mind that sometimeshigh voltages are involved. Avoid eventhe slightest risk - safety in the shackplease, at all times.

Whilst every care is taken when acceptingadvertisements we cannot acceptresponsibility for unsatisfactory transactions.We will. however. thoroughly investigate anycomplaints

The veers expressed by contributors are notnecessarily those of the publishers

Every care is taken to ensure that thecontents of this magazine are accurate. weailaume no responsibility for any effect fromerrors or omissions.

Cover PhotographsTop-The Hitachi V42540MHz, 2 channel oscilloscopefrom Thurlby Electronics (p4)Bottom-One of the PowermagA1500 series of PSUs from Advance(p10)

SPECIAL FEATURES22 Laboratory Power Supply

David Silvester presents a design for a cheap andvery useful PSU

28 Lighthouses of the AirPart 2 of Brian Kendal's occasional series on aviationelectronics details navigational aids

32 Data FileRay Marston concludes his mini-series on LM10application circuits

36 Soldering - Art or Science?P J Cooper with some useful tips on a subject close tomany home constructors' hearts

38 The MFJ-1274 INC 2Ken Michaelson says this unit is good news for packetradio enthusiasts

40 What is Image Processing?Dr C J D Catto explains how new developments in thisfield could soon bring it within the reach of the homeenthusiast

42 Duo -Band Loop AntennaA simple indoor antenna design, by Richard Marris

REGULARS4 Product News

12 News Desk14 Amateur Radio World18 ATV on the Air19 Network 93445 Medium Wave DXing47 Spectrum Watch49 Latest Literature54 DX -TV Reception Reports57 QSO60 Short Wave News62 Free Classified Ads

READER SERVICES27 Subscription Order Form50 Newsagents Order Form50 Back Issues Order Form59 Amateur Radio Subscription Order Form63 Free Classified Ad Form66 Advertisers Index66 Advertising Rates and Information

NEXT MONTH46 What's in Store for You

Next IssueCover Date October 1987, on sale Thursday10 September

Publication DateSecond Thursday of the month preceding cover date

Lab PSU - p22

AIL

0

Duo -band loop - p42

Up in the air - p28

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying tc any advertisement 3

PRODUCT NEWSFeatured on these pages are details of the latest products in communications, electronics and

computers. Manufacturers, distributors and dealers are invited to supply informationon new products for inclusion in Product News.

Readers, don't forget to mention Radio & Electronics World when making enquiries

40MHz OSCILLOSCOPE

The new Trio-Kenwood CS -1045, available ex -stock fromThurlby Electronics, is a low-cost 40MHz oscilloscope ofunusually high specification.

The CS -1045 has the rangeof facilities normally associ-ated with more expensivewideband oscilloscopes.These include dual timebaseswith calibrated delay timemultiplier, and a choice ofimmediate or triggered Bsweep following the A sweepdelay. An alternate -sweepcapability enables simul-

taneous display of theexpanded and unexpandedsections of a waveform.

The oscilloscope has threeinput channels, with indivi-dual position controls, givingit a six -trace capability in thealternate sweep mode. Themaximum input sensitivity is1mV per division and themaximum sweep rate is 10nanoseconds (ns) per divi-sion. Trigger facilitiesinclude dc and HF rejectmodes, single shot and anactive sync separator for TV -

and video frame and linesynchronisation. The A time -base can be frame synchro-nised while the B timebase isline synchronised, allowingeasy selection of individuallines. A variable sweep hold -off provides for stabletriggering on complex wave-forms.

The instrument has a 6inrectangular CRT with a 12kVpost -deflection accelerationvoltage which gives a sharptrace with the brightnessreserve needed to viewhighly -expanded waveformsections.

The CS -1045 is easily port-able, measuring only 12.5 x 5.2x 14.9in (319 x 123 x 380mm)and weighing just 9.2kg. It issupplied complete with twowideband switchablesensitivity probes. It is pricedat £695 + VAT.

A 60MHz version is alsoavailable.

Thurlby Electronics Ltd,New Road, St Ives,Huntingdon,Cambs PE17 4BG.Tel: (0480) 63570.

SIGNAL MULTIPLEXERAvailable from Thurlby

Electronics is the 0M358 sig-nal multiplexer which con-verts any conventionaloscilloscope into a eight -channel oscilloscope.

The 0M358 accepts up toeight signals with a band-width content from dc up to35MHz, and multiplexes themtogether so that they may bedisplayed using just onechannel of an oscilloscope.The ability to observe a largenumber of waveforms simul-taneously can be an impor-tant aid in analysing complexequipment. Typical applica-tion areas include micro-processor based products,data transmission systems,phase locked loop productsand analogue to digital con-verters.

Each channel of the 0M358has an input impedance of1MI//20pF and accepts inputsignals up to ±6V (12V peak -to -peak). This can be

extended to ±60V using astandard x10 oscilloscopeprobe. A switched attenuatorprovides three differentsensitivity levels and has acalibration accuracy of ±3%.The multiplexing rate is con-tinuously variable over a widerange.

All inputs and outputs arevia standard BNC sockets.The multiplexer is connectedto the CH1 input and to theexternal trigger input of theoscilloscope. An eight -wayswitch enables any of theinput channels to be used asthe trigger source. A fourposition mode switch is pro-vided which gives a choice ofdisplay between all eightchannels, channels one tofour, channels five to eight, orany single channel.

The 0M358 is equally suitedto the display of analogue ordigital signals. It is compactand lightweight, measuringonly 230 x 230 x 90mm (9 x 9 x31/2in) and weighing 1.3kg.

Thurlby Electronics Ltd.New Road.St Ives,Huntingdon,Cambs PE17 4BG.Tel: (0480) 63570.

LOW-COST SCOPECurrently available from

Thurlby Electronics is theHitachi V425, a 40MHz, two -channel oscilloscope.

A major feature of thisinstrument is its digital CRTreadout of voltage/timedifferences whereby the usersimply adjusts the cursor toobtain a direct digital readoutof the voltage difference andtime difference between twopoints on the display. Thepanel setting display functionprovides a digital CRT displayof the CH1 sensitivity and thesweep time, thus preventingerrors.

The V425 has an 8 x 10cmhigh resolution display withan internal graticule. 0%, 10%

90% and 100% scale markingsare provided to simplify pulsemeasurements.

Other features include a dcoffset function which enableshigh accuracy, verticallyexpanded measurements ofany desired portion of a

waveform: an alternate mag-nification facility wherebysimultaneous observation ofthe x10 magnified waveformand the original waveform ispossible; and stable trigger-ing on both channels, even ifthe signal frequencies of CH1and CH2 differ.

The V425 also has a guaran-teed ±35% accuracy for vol-tage and time over the 10°-35°C operating temperaturerange and a vertical sensitiv-ity of 1mV/div, thereby enab-lirig accurate measurementof the low level signals oftenencountered in microcompu-ter test and measurementapplications.

Other features includeeight divisions of dynamicrange: a dedicated TV syncseparation circuit whichspeeds up measurements ofvideo signals: a built-in signaldelay line, enabling measure-ment of the leading edge offast rise -time signals; and anX -Y mode which enablesaccurate phase -differencemeasurements.

The Hitachi V425 measuresjust 310 x 130 x 370cm andweighs only 7kg.

Thurlby Electronics Ltd,New Road,St Ives,Huntingdon,Cambs PE17 4BG.Tel (0480) 63570.

QUALITY DM MThe M3560 digital multi -

meter from Electronic & Com-puter Workshop Ltd offers awide range of measurementranges including voltage, cur-rent, impedance, continuity,transistor hFe, frequency andcapacitance.

Competitively priced, it ismeant for use in all types ofelectronic and electrical tes-ting. Its front panel has asingle 30 -position range -

4 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

selector switch and it fea-tures full protection for allranges, together with auto -zero and surge protectionfrom 1.5 to 3kV.

The measurement rangesinclude voltage up to 750V ac,1000V dc, dc/ac up to 20A,resistance from 200 ohms to20Mohms, LED/audible con-tinuity testing, transistor hFE,capacitance from 2000pF to20A.LF and frequencies up to200kHz.

The 31/2 -digit '1999' LCD hasa range of annunciatorsincluding a low -batteryindication and shows theunits selected.

The operating temperaturerange is from 0 to +40°C andthe M3650 measures 90 x 176x 36mm.

Electronic & ComputerWorkshop Ltd,Unit 1,Cromwell Centre,Step field,Witham,Essex CM8 3TH.Tel: (0376) 517413.

MODAL ANALYSERSolartron's new 1202

structural analyser offersfacilities for 4 -channel modalanalysis in a single package.

The 1202 is suited to prob-lem -solving applications inthe field, but is also versatileenough for the laboratory.Solartron has solved the com-patibility problems assoc-iated with combined systemsusing spectrum analysers andcomputers. In the 1202, soft-ware and hardware arematched for optimised sys-tem performance, yielding asystem with low costcapability.

Results are presented on afast graphic display featuringhidden line animation ofmode shapes, strain contourmaps, cross sectioning andflexible stack plots. Manyfeatures which are usuallyavailable only as accessoriesare standard in the 1202, forexample forced responsesimulation and structuralmodification software. It isstraightforward to operate,

Wes. af. wimMall. di. Win odaalb1iwM.i. a.

sift Ai

with self-explanatory menusand soft keys. All operationscan be programmed forrepeat testing, and consider-able built-in memory is pro-vided.

IEEE -488 and RS232 inter-faces and signal generatorare standard. The 1202 can beexpanded to provide up to 36channels for fast. accurateresults in large-scale testsusing stepped sine analysis.

Generator capability inc-ludes burst, periodic orpseudo -random noise, sinewave at arbitrary frequency,and user -definable wave-form.

Solartron Instruments,Victoria Road,Farnborough,HantsGU14 7PW.Tel: (0252) 544433.

;.41771.:iitunimimitni

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11h8An I/O module for VME-bus users offering both serialand parallel I/O is now avail-able from UECs (UniversalEngineering and ComputingSystems Ltd).

The GMS VO1 has 24 para-llel I/O lines offering a Cen-tronics -compatible printerport plus 12 additional bi-directional buffered I/O lines(or second printer port). Eightserial channels are provided.In addition to this I/O themodule features a fully prog-rammable 24 -bit timer/coun-ter with interrupt capability. A

control latch enables inter-rupt on any level from 1 to 7,with masking and disablefunctions.

The module gives VMEusers a building block forconfiguring multi-user I/O.Terminal, modem and printerports can be configuredallowing systems or com-munications control. Allserial I/O is via one-to-oneribbon cable. All parallel I/Ois accommodated through theP2 connector.

Serial channels are oper-able on RS232 or RS422 stan-

dards. Up to 18 programmablebaud rates are available from50 to 38.4kbps. The GMS VO1also features one user -defin-able baud rate.

Universal Engineering andComputing Systems Ltd,5/11 Tower Street,Newtown,Birmingham B19 3UY.Tel: (021) 359 1749.

FORTH COMPUTERThe TDS9090 is a powerful

control computer based onthe high level language,Forth. Although small, it hasfeatures which make it easyto use in instrumentationapplications. For example, itinterfaces with an alpha-numeric liquid crystal displayand has a built-in keyboardencoder. The software sup-port included helps in writingprograms for operator inputand output. Its low powerCMOS and surface -mountconstruction allow theTDS9090 into applicationswhere some control cardscannot be used.

The computer uses theHitachi 63A03Y micro-processor. It has a 16KbyteForth and full symbolic

assembler. Programs can bewritten in high level languagemixed with assembler fortime -critical parts. There is30K of RAM and 16K for theuser's program. There are 35parallel input -outputs andtwo serial ports. An on -card256 byte EEPROM is forstorage of system parameterswhich have to be kept whilethe unit is not working.Additional features includethe watchdog timer, time -of -day clock, multitasking and itssingle power supply drawingonly 3mA in a low poweroperational mode.

The TDS9090 is just 100 x72mm in size. In one version ithas a DIN connector so this isa shortened Eurocard. Theother has pin headers and youconnect to it by ribbon cable.

Any serial terminal can beused as the developmentinterface to the TDS9090 butan IBM-PC compatible isbest. BBC computers are alsosupported. The developmentcard costs £194.95 and sup-port software is £90.

Triangle Digital Services Ltd,100a Wood Street,Walthamstow,London E17 3HX.Tel: 01-520 0442.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 5

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PRODUCT NEWS

LIGHTNING PROTECTIONThe Swedish company Wes-

termo Teleindustri has laun-ched a lightning -protectedmodem for asynchronouscommunication over shortdistances, up to 18kilometres.

The modem, called MA -12,is designed for transmissionspeeds of up to 38,400 bits/sec, full duplex.

Both the modem and theequipment connected to it

are protected against light-ning and other forms ofelectrical interference bybuilt-in transient protection.In addition, the line andterminal sides are electricallyisolated, to provide evenmore interference protec-tion.

The modem can be con-nected to all equipmentwhich uses the RS232C andV24/V28 specifications. It canalso be used to communicate

with Westermo's earlierasynchronous modem.

Two or four -wire connec-tion can be used. Transmis-sion is not code -dependent,so that the modem can handleall protocols, codes, bit for-mats and parity requirements.

The standard MA -12 ismounted in a plastic box, butcan be supplied as a plug-incard for rack mounting or as awall -mounted unit.

The modem is one of a newseries of units called Access,which according to the manu-facturer have high reliabilityand long life expectancy.Specially manufactured hyb-rid circuits are said to ensurea dependable modem withvery few fault nodes.

A special tri-state techni-que is used to give error -freetransmission. This techniqueadditionally allows status sig-nals to be transmitted.

Westermo Teleindustri AB,Jan -Erik Lundstrom,S-640 40 Stora Sundby,Sweden.Tel: +46-16 612 00.

DIGITAL PLOTTERNew from Advance Bryans

Instruments is the Colourwriter 6400 series of digitalplotters.

The 6400 digital plotter hasa large 240K buffer memorywhich permits transfer ofcomplex plots at high speed,thereby releasing the hostcomputer and operator tocontinue other tasks. Theplotter accepts the HPGLstandard graphics language.

The 6400 series has a max-imum writing speed of 40cm/sand a pen -up speed of 55cm/s

to ensure fast generationaccurate plots. To optimisefor different writing media,the speed is programmable insteps of 0.4cm/s.

The 6400 accepts a widevariety of plotting mediaincluding coated or bondedpapers, or transparencies.

The 6400 series allowsunattended automatic plot-ting of up to 105 consecutivegraphs; and a digitising sightcapability enables the Col-ourwriter to digitise and feedback to a computer coordin-ates from maps, diagrams and

plots for storage orprecise positioning andreplotting of -stored shapes.

Built-in intelligence is pro-vided, including over 65 com-mands, which include bar andpie charts, fills, three charac-ter sets and seven line types.The plotter is software com-patible with a wide variety ofprograms.

A standard RS232 or IEEE -488 interface is included.

Advance BryansInstruments Ltd,14/16 Wates Way,Mitcham,Surrey CR4 4HR.Tel: 01-640 5624/640 3490.

NEW EEPROMRapid Silicon have intro-

duced a high performance65,536 -bit electrically eras-able and programmable readonly memory from Samsung.

Known as the KM2865A, thisdevice is organised as 8,192words by 8 bits, and is fabri-cated with the well definedfloating gate NMOS technol-ogy using Fowler-Nordheimtunnelling for erasing andprogramming. Its circuitdesign is such that data

written on the device can beeasily modified using simpleTTL levels and a single 5 voltpower supply.

Writing to the KM2865A isvery easy. The internally self -timed write cycle latches bothaddress and data to provide afree system bus during the10ms (max) write period.

The device features twoend of write detectionschemes to provide maximumdesign flexibility whileenhancing the system per-formance. DATA Polling is asoftware detection scheme todetect the early completionof a write cycle without usingany additional hardware.

Other features include afast access time of 200ns anda low power requirement of120mA active (max), 50mAstandby (max).

The KM2865A is housed in a28 -pin DIP which conforms tothe JEDEC byte -wide memorypin -out specification.

Life expectancy of thedevice is 10,000 write cycles/byte.

Rapid Silicon,Rapid House,Denmark Street,High Wycombe,Bucks HP11 2ER.Tel: (0494) 26271.

MINIATURE PRINTERCrotech's MP -280-40 is a

ruggedly -designed miniatureprinter module which is cap-able of printing 40 highlylegible characters per line on69mm wide plain -paper rolls.

It is ideal for use in instru-ments and equipment wherespace is an important con-sideration. The dot matrix is 5x 7 and provides a graphicpoint density of 240 per line.Print speed is 4 dot lines persecond and the power supplyrequirement is +5V dc. Theaverage motor current is 0.2A,while peak needle current isapproximately 2.5A. The smalldimensions of the printer(103.6 x 15.4 x 45.5mm) allow itto be incorporated into com-pact and portable packages.

RRP for the MP -280-40 is£48.94 excluding VAT.

Crotech Instruments Ltd,2 Stephenson Road,St Ives, Huntingdon,Cambridgeshire PE17 4WJ.Tel: (0480) 301818.

8 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

PRODUCT NEWS

Rendar have introduced anefficient low-cost method ofblocking mains -borne inter-ference.

The Combicord is a mainscable cordset which uses thecable itself as a capacitance,together with the coils andcapacitors built into the plugand receptacle. Excellentsuppression characteristicsresult. The Combicord retainsits filtering efficiency even atvery high frequencies. Thereis virtually no interference onthe appliance side.

Filters are not always builtinto basic equipment. Retro-fitting can be an expensivenuisance and is frequentlynot carried out. Susceptibleequipment can be suppres-sed by utilising the Com-bicord.

Rendar Ltd,Durban Road,South Bersted,Bognor Regis,West Sussex P022 9RL.Tel (0243) 825811.

UNINTERRUPTABLE MODULENew from Coutant is an

uninterruptable power supplymodule for the ML range ofswitched mode power sup-plies that provides an auto-matic changeover to batterypower should the mains 'sag'or break altogether.

Called the MLU250, the unitconnects to the ML via a pairof wires and to a NiCad or leadacid battery. Power hold uptime depends on the capacityof the battery employed andcan be in excess of twentyminutes - more than enoughto shut the powered equip-ment down in an orderlyfashion should the mains fail.When the mains is present the

battery is charged, the char-ging current being depen-dent on the state of thebattery.

There are four models inthe MLU range, covering allcombinations of either 24 or48V input and capability witheither a NiCad or a lead acidbattery.

Coutant Electronics Ltd,Kingsley Avenue.Ilfracombe,Devon EX34 8ES.Tel: (0271) 63781.

TCO FUSESA new range of miniature

thermal cut-off (TCO) devicesfrom Steatite is designed toprovide fast, accurate protec-tion against thermal over-loads in electronic equip-ment.

Small enough to beincorporated into motor win-dings, solenoids and heat -sinks, the TCOs are rated foroperation at 125 or 250 voltsfor the protection of mains -operated equipment. Axialand radial -leaded as well asplug-in types are available tosuit different applicationrequirements.

Elcut TCOs cover rupturingtemperatures from 76°C to187'C.

Steatite Group,2 The Square.Broad Street,Birmingham B15 1AP.Tel: (021) 643 6888.

QUAD OP -AMPNational Semiconductor

Corporation has announcedthe arrival of a quad operatio-nal amplifier which achievesa low 140dB dynamic rangewith less than 0.0015% distor-tion. This feature gives theLM837 the high performancerequired by the latest genera-tion of compact disc playersand digital audio systems. Inaddition, the LM837 requiresless board space than low -noise duals, which increasesreliability.

The LM837 has the ability todrive 600 ohm loads, a highslew rate exceeding 8V/ms,and a wide power bandwidthof 140kHz.

The LM837 quad op -ampcontains a new type of outputstage that drives a 600 ohm

CO -AX SWITCHES

Micronetics have a newrange of co -ax switchescovering the frequency banddc to 18GHz in single polechange -over and transferconfigurations.

Both dc and ac operation isavailable, as well as latchingand fail-safe options. Con-nector interfaces availableare N, SMA, TNC, togetherwith PCB mounting models ormicrostrip and strip line.

Waveguide models are also

available from the Microneticrange, covering the mostpopular waveguide desig-nated bands. Modular driveheads provide the option formanual or motor operation.

Tony ChapmanElectronics Ltd,Electron House,Hemnall Street,Epping,Essex CM16 4LS.Tel:

load, and so is well suited foramplification and signal -con-ditioning circuits.

The LM837 is also wellsuited for active filterdesigns, since it has a low -input noise voltage of 0.5i1Vand low THD of 0.0015%, andcontains four very low noiseamplifiers on a single chip.

The LM837 also has a pin -out compatible to other stan-dard quad op -amps, and socan be used to upgradeexisting systems with little orno design changes.

National Semiconductor,lndustriestrasse 10,D-8080 Furstenfeldbruck,West Germany.

CONNECT SBulgin's BS4491/I EL, 320

ultra -sonically welded, non-rewirable connectors havegained BSI approval, as wellas VDE and UL recognition.

The appliance connectorscan be supplied as compo-nents in their own right or ascord sets with BS1363A, CEE7,American and many othertypes of mains plugs to meet

customer requirements.The BSI Kitemark has been

awarded to both cold condit-ions (P887 and P887SE) 6 ampand hot conditions (P897 andP897SE) 10 amp connectors,whilst VDE and UL recogni-tion has been granted for the6 amp versions and SEMKOfor (P887) 6 amp.

AF Bulgin and Co PLC,Bypass Road,Barking,Essex IG11 OAZ.Tel: 01-594 5588.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 9

PRODUCT NEWS

POWERMAGNew from Advance Power

Supplies is the recentlyexpanded range of Power-mag A1500 series PSU.

The Powermag range is nowavailable with 2V, 300A; 5V,300A; 12V, 125A: 24V, 65A; 48V,35A; and 60V, 25A outputs. Theranged units deliver up to

1680W dc output (modeldependent), when poweredfrom either a nominal 220V acor 110V ac input.

Features of the rangeinclude dual input (user -selectable input voltageranges of 88-132V ac and 176-264V ac); input frequency of47-63Hz; soft switching andmagnetic amplifier technol-ogy, ensuring high reliability,full filtering to VDE 0871,Curve A and creepage andclearance distances to VDE0806 and IEC 435.

The Powermag range hasan efficiency of better than70% and a temperature coeffi-cient of 0.015°/0/*C. Both para-llel and series operation areenabled.

The series has an operatingtemperature range of 0°C to+ 70°C.

Advance Power Supplies,Raynham Road,Bishop's Stortford,Herts CM23 5PF.Tel. (0279) 55155.

SMARTPAKCommunication Develop-

ment Specialists Limitedhave introduced what theyclaim is a new concept incommunication power sup-plies.

The design of the powersupply was inspired by thefact that standard power sup-plies used in communicationenvironments have severaldrawbacks. The main problemis that the power supply mustbe capable of supplying fullload without any ripple ordegradation of supply vol-tage. This full load conditionmay only occur 5-10% of thepower supply duty cycle time,with the remaining load only20% of the full load condition.

This means that most powersupplies are manufactured tosupply a continuous output atfull load condition and oper-ate at 20% of their capacity for90% of their duty cycle, andare bulky and unnecessarilyexpensive. Power suppliesdesigned for intermittent fullload condition can generateunwanted heat and some-times fail under extremeconditions if their specifica-tion is not strictly adhered to.

Regular non -specialisedpower supplies are designedas stand-alone units and are

often unattractive, and prob-lems may arise when attemp-ting to mount or connect fixedequipment to their enclo-sures. Also, many power sup-plies are entirely reliant onthe availability of a con-tinuous mains supply.

The Smartpak communica-tion power supply is an attrac-tive unit, with adhesive frontpanel and indicator filter forOEM applications. A quicklydetachable equipment trayhas adequate clearance forbolting guest equipmentbracketry.

The power supply internalsconsist of a 6AH gas recom-bination (totally sealed) leadacid battery, to provide up to20A of 13.8V dc (or more ifrequired). A battery conditioncircuit and a dual rate chargerensure the battery is workingto full capacity.

The advantage of this com-bination is that should themains fail the power supplybattery will maintain power tothe extent of its capacity.

Smartpak will operate on120 or 240V ac mains, and canbe supplied with 6, 12 and18AH standby capacity.

CDS Ltd,PO Box 83, Basingstoke,Hampshire RG25 2PX.

When a monitor is used inareas of high magnetic inter-ference it is likely that thequality of the display willbecome distorted, or eventotally unreadable.

Sources of such magneticinterference are common infactories, near undergroundrailways and in any other areawhere heavy motors orswitching gear are employed.It is also possible for electro-magnetic cross talk to occurbetween two monitors thatare mounted side by side orone on top of the other.

To solve the problem, theCanadian company Electro-home have introduced ascreening case which is avail-able as an optional extra for

their range of high -resolution13in colour monitors.

The cases are manufac-tured from laminate or sheetmetal and a special ultra -thinhigh permeability foil whichhas excellent electro-magne-tic shielding characteristics.

Tests have shown that thenew case attenuates bothstatic and dynamic electro-magnetic fields by more than60dB.

At the same time as reduc-ing the effect of electro-magnetic interference on themonitor, the new case has anequal effect on the electro-magnetic fields generated bythe monitor. Not only doesthis make the monitor moresecure, it being more difficultto 'eavesdrop' on the dis-played data using radioreceiving equipment, it alsomakes the monitor a goodchoice in those applicationswhere the generation of radiointerference has to be kept toa minimum.

Electrohome Electronics,7 Civic Way,Ellesmere Port,South Wirral,Cheshire L65 OAX.Tel: (051) 356 1365.

INTRUDER ALARMThe increasing incidence of

burglary and other crimesinvolving the illegal entry ofproperty has caused manyhouseholders to try toimprove the security of theirhomes.

The fitting of good qualitywindow and door locks isimportant, but in many casesthe determined criminal canstill force an entry. A cost-effective way to deter them isto fit an intruder alarm. Infra-red alarm systems are simpleto set up and install, with agood sensitivity to movementwithin the protected area.

Electronic and ComputerWorkshop (ECW) can nowsupply an infra -red securitysystem which consists oftransmitter and receiver mod-ules used in conjunction witha central alarm station. Thetransmitter/receiver units aresited at strategic points in therooms to be protected and theinfra -red light forms invisiblebeams that can be used todetect the presence of intrud-ers. If the beams are broken, a

10 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

PRODUCT NEWSsignal is sent to the centralunit which can be program-med to sound an alarm.

The transmitter can be sitedup to five metres from itsreceiver unit, and both runfrom low voltages supplied bythe central station. Theirsmall size means that theycan be unobtrusively placedat almost any location.

The central alarm stationcan run with up to threetransmitter/receiver pairsand offers a range of alarmalternatives, set by the user.Normally operating frommains power, the central sta-tion has an automatic batteryback-up function that pro-tects the system in the eventof a power failure.

ECW offers the K2549 trans-mitter unit at a mail orderprice of £19.61, the K2550receiver at £23.09 and thecentral alarm station at £26.98.Prices are for easy -build kitversions and include post/packing and VAT. Ready -builtversions are available at asmall extra cost.

Electronics and ComputerWorkship Ltd,Unit 1, Cromwell Centre,Step field,Witham,Essex CM8 3TH.Tel: (0376) 517413.

PORTASOL TIPSA range of replacement

tips, with diameters of 1.0, 2.4,3.2 and 4.8mm, is availablefrom Freetrade (TEP) Ltd forthe Portasol portable gaspowered soldering iron.

The tips are easily fitted andinclude the patented catalyticconverter that generates heatright at the tip for maximumefficiency. Powered by gascigarette lighter fuel, thePortasol has a variabletemperature range of up to400°C - equivalent to anelectric iron's output powerfrom 10 to 60W. One filling ofgas gives up to 60 minutes ofcontinuous operation.

No larger than a felt-tip pen,Portasol can be carried in atop pocket and has a clip -oncover with a built-in igniter.The powerful gas -operatedheater gives a stable outputthat is superior to battery -operated portable types. Thisfrees the user from having towork near a mains power

CORDLESS SOLDERINGThe Oryx Iso-Tip range

of rechargeable battery -powered soldering irons isnow available from Green-wood Electronics. Perform-ance is said to match that of a50W iron with a tip tempera-ture of over 370°C. Onecharge is sufficient for atleast 100 soldered joints.

Each tool comprises an ironand a base stand/chargerunit. Typical zero to fullcharge time is between threeand four hours but a batterywhich is only partially dis-charged will return to fullcapacity in under two hours.An iron can be left on chargeindefinitely without risk ofover -charging.

A version which can becharged from a 12V car bat-tery (via the vehicle's cigarlighter) is also available. Tipscan be quickly changed with-out tools.

A PC drill attachment is alsoavailable which fits in place ofthe tip and can be used forcleaning excess solder fromthe PCB holder or as a small,low power, general purposeminiature drill.

Greenwood Electronics,Portman Road,Reading RG3 1NE.Tel: (0734) 595843.

point or bother with exten-sion cables.

Freetrade (TEP) Ltd,Moor Lane,Witton,Birmingham 86 7HH.Tel: (021) 356 2582.

Cobonic Limited hasannounced a battery -oper-ated electronic timer,

a

incorporating a true stop-watch, a countdown/alarm/count -up timer, and a clock.

The timer has a memory anddoes not need to be keyed inagain for repetitive identicaltimer settings. The multipur-pose clip can be used toattach the timer by magneticforce to metallic surfaces orby a spring -loaded clip to awriting pad. Alternatively, itcan be stood on a desk. Thetimer sells for £17.50 butduring the company'sintroductory sale, they areoffering it at a 20% discount,at £14.00.

If a cheque or postal orderis sent in advance to Cobonicthey will pay the carriage.

Cobonic Ltd,32 Ludlow Rd, Guildford,Surrey GU2 5NW.Tel: (0483) 505260.

BONDING TOOLSThe Gaiser Tool Company's

range of semiconductor wirebonding tools is now avail-able in the UK from DageIntersem.

For thermosonic and ther-mocompression bonding,Gaiser introduced the cera-mic capillary to the industryand now offers sapphire andruby -tipped ceramic capillar-ies. These give a Icng tool life,with reduced friction on thebonding wire to eliminatelooping and breaking prob-lems. Gaiser wedge bondingtools are designed to ensurebond integrity whatever thematerials and techniquesused. The range includeshigh -strength tungsten car-bide wedges for minimumwear, and special alloys forreliable room temperaturebonding of gold wires.

The tools are suitable foruse with both thermosonicand thermocompression bon-ding machines, from simplemanually operated to high-speed pattern -recognisingautomatic types. Die colletsand vacuum pick-up tools arealso available.

Dage (GB) Ltd,Rabans Lane, Aylesbury,Bucks HP19 3RG.Tel: (0296) 393200.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 11

Goonhilly celebratesTwenty-five years ago

world-wide communicationsentered a new era. Telstar,the world's first commercialcommunications satellite,was launched on July 10th,1962, and the first live tele-vision signals via satellitewere received by BritishTelecom's Goonhilly earthstation in the early hours ofthe following morning.

Today, British TelecomInternational (BTI) handlesmore than three million min-utes of telephone calls, tele-vision pictures, data, facsi-mile and telex every daythrough Goonhilly and itsother intercontinental links.

World-wide satellite com-munications began with thatfirst live television transmis-sion from America, and, onthe evening of July 11th, thefirst live television transmis-sion from Goonhilly to theUSA. Two days later theworld's first telephone call bysatellite was made, from Lon-don to New York.

Tests during the Telstartrials showed that satellitetransmission had a commer-cial future in world tele-communications, heraldingthe introduction of serviceswhich are now taken forgranted. Six days after Telstarwas launched, Goonhillytransmitted the first colourtelevision pictures via satel-lite, long before colour tele-vision was commonplace inthe United Kingdom or theUnited States.

The first antenna, used inthe Telstar transmissions,and still operational, wasunique. British -designed, itwas a 'dish' antenna, com-pared to the French andAmerican 'horn' antennas.But the unique dish designwas to prove superior forsatellite communications andis now used generally bynearly 700 satellite stations in

a than 150 countries.Goonhilly visitors' centre is

open to the public from 10amto 6pm, every day of the weekbetween Easter and the endof September.

A day to rememberTwenty-five enthusiastic

young electronic designers,ranging from 12 to 21 in ageand representing sixteendifferent educational institu-

tions in virtually all parts ofGreat Britain, took part in thefinals of the 1987 YoungElectronic Designer Awardscontest at the Institution ofCivil Engineers, GreatGeorge Street, London SW1.

Projects were designed tosatisfy key requirements ineveryday life and were judgedon their commercial viabilityas well as presentation,technical competence andorginality. They were createdin response to the YEDAScheme's challenge foryoung people to apply elec-tronics know-how in thedevelopment of world beat-ing products, which are soimportant to the futureprosperity of British industry.

Each of the overall winnersin the three age groups wasawarded a trophy, individuallysculptured in solid bronzeand engrained with silver bySir David Hughes Bt, whichrepresents a three dimen-sional YEDA seedling.Designed to symbolize youthand technical creativity, thetrophy can be retained as apermanent memento of theoccasion.

Winner in the Senior categ-ory was Douglas Mackay,aged 21, of Robert Gordon'sInstitute, Aberdeen, for his

NEWSDESK

robotic functional arm.First in the Intermediate

category were Paul Dagley-Morris, 16, and Roger Lucas,15, of Cheltenham College,for their animal stress meter.

In the Junior category NeilMotson, 14, and JonathanCragg, 14, of WilfordMeadows School, Notting-ham, came first with theirdigital tyre pressure gauge.

Wilford Meadows Schoolalso won the Texas Instru-ments Business -Pro compu-ter for the project adjudged tohave the most commercialpotential.

Come out to playThe tenth Personal Compu-

ter World Show this yearhopes to illustrate a thrivinggames and leisure industry,complete with the top 20names in entertainment soft-ware and a new generation ofmore sophisticated videogames. Stand space in Olym-

pia's National Hall is sold outand visitors can expect anaction -packed exhibition,with the chance to try forthemselves the latest gamesfrom all over the world.

Last year, 66,030 visitorsclicked through the turnstilesat Olympia, creating record -breaking attendance figureson all five days of the show. Aneven bigger turnout isexpected at this year's exhibi-tion, which runs fromWednesday 23rd to Sunday27th September. The first twodays are for business andtrade visitors only, but thepublic are admitted from Fri-day 25th onwards.

Regular faces amongst theexhibitors include Activision,launching the BangkokNights successor to The LastNinja, Amstrad, Ocean Soft-ware, Prism Leisure Corpora-tion, US Gold, Acorn Compu-ters, Mastertronic, ElectricDreams, Elite Systems and

Mobile dataSweden, Norway and Fin-

land agreed recently to goahead with a common systemfor mobile data comms.

The system, called Mobitex,has been in operation inSweden since October 1986,and is the first public radiotelecommunication networkfor text, voice and data.

Finland has definitelydecided to introduce theMobitex concept, and Norwayplans to follow suit. Denmarkis not committed, but isundertaking a quick marketresearch exercise to deter-mine the concept's potential.

Following the acceptanceof the mobile telephone as aneveryday business tool, thedemand for mobile datatelecommunications hasincreased. In addition, textand data transfer providesmore efficient use of theavailable frequencies thanspeech.

The Scandinavian mobiledata market is still in its

infancy. Forecasts indicatethat there will be 40,000mobile data terminals in theregion by 1990, increasing to160,000 by 1995. It will take.11111111r

energetic marketing of boththe service and the terminalsand application systems toachieve this rate of expan-sion.

111

12 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Mirrorsoft. Atari is planningto repeat its successful vil-lage style stand, and thisyear's show sees a number ofmajor new exhibitors, manyfrom abroad.

The Personal ComputerWorld Show is sponsored byPersonal Computer Worldmagazine and organised byMontbuild Ltd. Opening timesare 10.00 until 19.00 hoursevery day except Sunday 27thSeptember, when the exhibi-tion will close at 17.00. Ticketsare available through KeithProwse ticket agencies (tel:01-741 9999), or at the door,priced at £3 for the public,with discounts on groups of 10or more.

CB licence evasionA concerted campaign to

combat Citizens' Band (CB)licence evasion is to becarried out in London overthe next few weeks by theDepartment of Trade andIndustry's Radio Investiga-tion Service (RIS).

The campaign is part of acontinuing effort by the DTI to

ensure that CB users arelicensed. As well as counter-ing licence evasion, the RISwill also be checking on theuse of illegal equipment.Linear amplifiers (known as'burners'), AM and singlesideband equipment, as wellas certain types of aerials, areall outlawed under CB regula-tions.

A CB licence currentlycosts £10 and can be boughtfrom post offices. The max-imum penalty for unlicenseduse is a fine of up to £2,000and/or up to three monthsimprisonment. The courts canalso order forfeiture of equip-ment.

The brain drainFor some years there has

been an increasing concernthat among factors adverselyaffecting science, technologyand engineering in the UK is agrowing loss of talent abroad-the so-called 'brain drain'. Inorder to secure a sounderbasis of data on this subject,the Science and EngineeringPolicy Studies Unit of the

Royal Society and the Fellow-ship of Engineering hasundertaken a study of theinward and outward flows ofscientists and engineers toand from the UK. The scope ofthe study was limited to thoseworking in Biochemistry,Chemistry, Earth Sciences,Electronic Engineering andPhysics, who left or came tothe UK between 1975 and1985.

A report describes theresults of that study. It isbased largely on a question-naire survey of universitydepartments, researchgroups and industrial, gov-ernmental and researchcouncil establishments.

The numerical scale of mig-rants identified here wouldnot generally be consideredlarge in comparison with theoverall size of the groups thatmigrants left or joined. Butthe significance of migration,inward or outward, lies notonly in counting heads butalso in the intellectual capac-ity of the migrants, theirexperience and the period of

Radlopaging by satelliteTrials of British Telecom's

world -first satellite radiopag-ing service are to start at theend of the year.

It will enable drivers oflong-distance lorries to becontacted immediately bytheir companies while theyare on the road - particularlythose of road haulage firmsoperating on routes across

Europe, the Middle East andAfrica.

The service will provideanother international exten-sion to the existing radiopag-ing service operated in theUnited Kingdom by BritishTelecom Mobile Communica-tions (BTMC).

Earlier this year BTMCannounced that it would pro-vide a transatlantic paging

service through a joint opera-tion with Metrocast, a US -based paging company. TheMetrocast service is due to belaunched this autumn. It usesa frequency -agile pager anddoes not .depend on satellitetransmission.

Customers taking part inthe trials will make theirsatellite paging calls inexactly the same way as aninland paging call. Messageswill be routed via BTI's satel-lite earth station at GoonhillyDowns, Cornwall, to anINMARSAT satellite. The sig-nal the satellite sends back toearth will be received by asmall 'patch' antennamounted flush with the roof ofthe lorry cab. A MessageMaster pager in the cab willdisplay the message and aprinter will provide a copy.

The receiving equipmentforms the most compactmobile receive -only satelliteearth terminal yet designed,while it requires no morepower from the vehicle's bat-tery than a 6W side -light bulb.

Prospective customers canobtain more information bycalling 01-388 4222 and askingfor satellite radiopagingsales.

time they spend in any oneinstitute or country. Themajority of those leaving theUK did so for long-term postsabroad; most foreign scien-tists and engineers coming toBritain from overseas camefor relatively short periods.

Thus, although almost asmany 'experienced' scien-tists and engineers enteredthe UK as left, the dataprovides no grounds for com-placency. It was found that,over the ten year period of thestudy, many recent PhDs leftthe UK without having takenup employment in this coun-try. A greater proportion ofthese young people emigratepermanently than was thecase 25 years ago. This illus-trates that an increasingproportion of our mosttalented scientists have beenamong those who have leftthe UK.

Home taping royaltyIt was announced in June

that a home taping royalty of10% will be added to the priceof blank audio tapes, as partof a new copyright law. Theproceeds of the royalty will bedistributed to the performers,composers and producers ofsound recordings. The newlegislation will be introducedduring the 1987-88 session ofParliament.

Commenting on the move,Ian Thomas. the DirectorGeneral of the InternationalFederation of Phonogram andVideogram Producers (IFPI)said: 'As the internationalorganisation of the recordingindustry, IFPI welcomes theBritish Government's firmcommitment to copyrightreform and in particular itsproposal to deal with thehome taping problem.Although a royalty does notrepresent a totally satisfac-tory solution to the problemof private copying, such amove will bring the UnitedKingdom into line with themajority of its European Eco-nomic Community partners.Three member states(France, Germany, Portugal)already have such a royalty,while bills have beenintroduced in the Parliamentsof Spain, Belgium and Italy,and the Dutch Governmenthas announced its intentionto provide a private copyingroyalty.'

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 13

AMATEUR RADIOWORLD

Compiled by Arthur C Gee G2UKAt long last, the much heraldedRussian amateur radio satellites

have been launched. Because of a lack ofprior information from the Russianauthorities, the launch, which took placeon 23rd June from Plesetsk, came assomething of a surprise, and the lack oftracking information and orbital predic-tions led to much confusion which istaking some time to clarify. Matters werenot helped by the complexity of thesatellite - or satellites - launched. Thelaunch of further Russian amateur radiosatellites in the RS series had been'confidently' predicted by some amateurradio commentators for the past twoyears or so, and their predictions helpedto confuse the issue still further.

A TASS statement received in thiscountry on 25th June by the spaceauthority, Geoff Perry, and immediatelypublished in a newsheet from theKettering Group, said that an 'artificialEarth Satellite Cosmos 1861 had beenlaunched. It was intended for operationas part of the space navigation systemestablished to determine the location ofships of the marine and fishing fleets ofthe Soviet Union in any point of theworld's oceans. The Sputnik was put intoan orbit with the following parameters:the initial period of revolution - 105minutes; the maximum distance from thesurface of the Earth - 1014km; theminimum - 995km; the inclination of theorbit - 83 degrees.

The Sputnik Cosmos 1861 also carriesequipment designed by wireless enthu-siasts of the Voluntary Society forassisting Army, Air Force and Navy, toensure amateur radio communicationsand carry out experiments in scientificand education purposes. The systemsaboard the Sputnik are functioningnormally.'

This would suggest that the amateurradio equipment was part of the Cosmos1861 spacecraft and not two separatesatellites launched along with Cosmos1861, as was stated in some quarters.

Monitoring the frequencies expectedto be used revealed that the navigationalsignals were on 150.00MHz and that theamateur radio signals were on a numberof frequencies around 29.350 -29.450MHzand used the callsigns RS10 and RS11.Besides the beacon CW telemetry, quitea number of other signals were identi-fied, suggesting data, RTTY, etc modes

of transmission. It was thought that thesemight be due to cross -modulation of thenavigational transmission with the radioamateur ones. If this is so and isincurable, this might mean a permanentshut down of the amateur radio transmit-ters.

The complexity of the new satellite'package' is illustrated by the quiteextraordinary number of modes ofoperation of the amateur radio side ofthe set-up. There are transpondersworking with an uplink in the 15 metreband and a downlink in the 10 metreband, there is another with a 2 metreuplink and a downlink in the 10 metreband and there is also one with a 15 metreuplink and a 2 metre downlink, plusvarious combinations of these. There arealso robot transponders.

So far most of these modes have beenidentified by amateurs, and QSOs havebeen had through some of them. At thetime of writing, the telemetry has notbeen deciphered completely and theredoes not appear to be any indicationfrom the beacons about which channelthe satellite is working on or is going towork on in the immediate future. Nodoubt in time all will be revealed, butuntil it is, confusion reigns!

Youth awardWhen John Butcher, the Industry

Under-Secrtary in the previous Govern-ment, opened the RSGB National Con-vention earlier this year, besides hintingat the increase in facilities beingcontemplated for the 50 and 70MHzbands, he said that to mark the 75thanniversary celebrations of the RSGBnext year, the DTI is to award a prize forYouth Achievement in Amateur Radio.He said this idea had been enthusias-tically welcomed by the RSGB, who willmake it a joint DTI/RSGB venture. This,he hoped, would focus a lot of youngpeople's attention on the hobby ofamateur radio.

With their subscription reminders, theRSGB is enclosing a smart brochuredrawing members' notice to the advan-tages to be gained from RSGB member-ship: a good idea to remind members ofwhat they get for their money, as well asencouraging non-members of the meritsof joining the society.

During the past six years, membershiphas nearly doubled, from 19,000 in 1977 to

34,000 today. As the brochure points out,this is very comforting and flattering -everyone likes to think of their specialinterest as going from strength tostrength rather than declining.

Apart from this, there are otherimportant considerations. The larger thenumber of members, the greater theservice that can be provided and thelower the cost. A further, very importantconsideration is that amateur radio isessentially international in nature. Astrong national society is essential if it isto continue to play a leading role amongthe 117 other national societies which goto make up the International AmateurRadio Union. Without a concerted efforton the international scale there would begreat difficulty in maintaining, let aloneextending, that most valuable, andessential, requisite of our hobby - ouramateur radio bands.

Operation RaleighWe have mentioned the activities of

Operation Raleigh several times in thiscolumn and the amateur radio opera-tions from the flagship, SES Sir WalterRaleigh.

The Sir Walter Raleigh has had toreturn home prematurely, the mainreason being one of cost. The day to dayrunning costs of a 2,000 ton ship absorb agreat deal of cash, which the OperationRaleigh organisers consider could bebetter spent on other projects.

The amateur radio station on board theship, GBOSWR, participated in someinteresting VHF experiments during herreturn journey. Running 100 watts on144.175MHz into a 4 element quadantenna at 15 metres above sea level, itwas found that contacts with the UKcould be achieved with relative ease andgood signal strengths over a distance of1000km.

50 and 70MHzApparently, the release of the 50 and

70MHz bands to Class B licensees seemsto have been one of the most popular ofthe recent achievements of the RSGB.The response to this success by letterand telephone leaves no doubt about theappreciation of the membership. Gettingthese facilities was no easy task and wasthe result of a lot of very hard work by thesociety.

Having secured these facilities, every

14 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

responsible user of these frequencies isvery anxious that the selfishness of a fewmight put these privileges in jeopardy.50MHz is still allocated to the broadcas-ting service in numerous countrieswithin range of the UK. If interference tothese broadcast services occurs fromamateur radio activity, the use of theband will be immediately withdrawn.

The power limits at 50MHz are 14dBWcarrier and 20dBW ERP. How do youcalculate these? The problem seems tobe bothering more than a few users ofthese bands. If you are one of them,consult the News Bulletin feature in theissue of Radio Communication for July1987, page 502. Here you will find thetopic very well covered indeed. We needsay no more. If you are in doubt, this isessential reading for you.

Computer softwareOne of the snags about computers is

that each variety seems to specialise inone particular type of activity, or, moreoften perhaps, ignores one particularinterest.

The Sinclair computers are very wellsupplied with a lot of good software foramateur radio activities - particularlywith regard to satellite interests. Themost popular computers nowadays seem

to be those in the Amstrad series, butthey do not accept Sinclair software nordo they seem to be producing technicalsoftware of an amateur radio interest.

There is, however, an organisationknown as the Sinclair Amateur RadioUser's Group - SARUG for short. Theyhave recently added the Amstrad CPC totheir interest. They were formed in 1981to provide amateur/SWL users of Sinclaircomputers with a way of sharing know-ledge concerning the wide range ofactivities opened up by cheap homecomputers. They became the mainsource of supply for a wide range ofpublic -domain software for amateurradio users and they claim that they havehelped to influence the commercialavailability of both software and hard-ware by bringing members' needs to theattention of those working on radio -computing projects.

This has included RTTY, weather fax,satellite telemetry, etc. The group has a5 -times yearly newsletter of 16 pages.The newsletter is circulated to otherinterested groups in several countriesand is read in over thirty countries. The'software service' makes certain prog-rams available on tape free to members.SARUG is the sole source for GM4IHJsatellite and propagation software for

the Spectrum micro. The membershipfee is £5.00. Readers with Amstradcomputers should contact this group notonly to see what software they cansupply, but also to register their interestin technical software for the Amstrad.Write to Paul Newman G4INP, 3 Red -house Lane, Leiston, Suffolk IP16 4JZ.

Free from the DTIThe following are available free of

charge from the DTI. They are all verywell worth getting, particularly theAnnual Report for 1986. They can beobtained by phoning the 24 hour answer-ing machine on 01-275 3072 or by writingto The Librarian, CommunicationBranch, DTI Room 605, Waterloo BridgeHouse, Waterloo Bridge, London SW1.

You may ask for any or all of thefollowing, post free: The Annual Reportof the DTI Radio Frequency Service;Radio Amateur Information Sheets 1 to 5;Frequency Allocation Wall Chart.

The number of current amateur radiolicences in the UK at the end of April lastwas as follows: Class A - 30,242: Class B-27,166, making a total of 57,408. This is anincrease of 2.4% over the last 12 months.The number of prosecutions for offencesunder the Wireless Telegraphy Act forthe first quarter of 1987 was 111.

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 15

1 NEW MOBILEMASTERPIECESIC900 Super Multiband FM System.

This new addition to ICOM s Ham radio equipment is a rnulttbandFM transceiver system that allows the mobile operator to customize acommunications system for his favourite bands. Up to 5 optional band -units can be installed with the 10-900 for instant access to a wide rangeof frequencies from the 28MHz HF band to the 1240MHz UHF band.Only a small remote controller is necessary for control of all these bands.A flexible optical fibre is used between the Remote Controller and theInterface Unit. The IC -900 has independant, full duplex capability on allbands, providing simultaneous receive and transmit operation.The function display on the Remote Controller shows two separateoperating frequencies simultaneously. The 10-900 system transceiveris equipped with 10 fully programmablememory channels in each Band Unit.The system can therefore store up to50 different memory channels.This revolutionary new concept inMultiband operation is available fromyour ICOM dealer. Also feel free tocontact ICOM (UK) LTD for assistanceor information. The IC -900 Multi -bandsystem consists of a Remote ControllerInterface Unit A Interface Unit B and aseries of specially designed Band Units.UX19 28-30MHz 10 watts*UX59 50-54MHz 10 watts*(No mobile operation allowed in UK)UX29 144-146MHz 25 wattsUX29H 144-146MHz 45 wattsUX49 430- 440MHz 25 wattsUX129 124n-12o0MHz 10 watts

IC1100, 13(ms FM Mobile.To complete the range of VHF. UHF FM

Mobiles this new model is now available for the23cm Ham band, it is based on similar featuresto the already existing IC -28E 2m and IC -48E70 cms mobile units. This Mini -mobile trans-ceiver will fit easily anywhere in your vehicleor shack. Power output is 10 watts or 1 watt low.The IC -1200 is so new we do not even have apicture of it, however, the large front panel LCDreadout is designed for wide angle viewing andfront panel controls are straightforward to makemobile operation safe and easy. The IC -1200 isa superb example of ICOM's dedication toexploring new communication equipment.

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16 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

CommunicationsVHF/UHF FM HandportablesIf you want a handheld with exceptional features qualitybuilt to last and a wide variety of interchangeable access-ories. take a look at the ICOM range of FM tranceivers,all ICOM handportables come with a nicad battery packAC wall charger. flexible antenna and wrist strap

Micro 2E/4EThese new micro -sized 2 metre and 70 centimetre hand -portables give the performance and reliability you vecome to expect from ICOMMeasuring only 148 x 50 x 30 the Micro fits in your pocketas easily as a cassette tape. The Micro 2E 4E features anup/down tuning system for quick frequency adjustments10 programmable memories. a top panel LCD readout.up to 2.5 watts of output (optional)

IC -2E 2 metre Thumbwheel HandportableThis popular handheld from ICOM is still availableFor those amateurs who require a straightforward andeffective FM transceiver the IC -2E takes some beatingFrequency selection is by means of thumbwheelswitches (with 5Khz up switch) simplex or duplex facilityPower output is 1.5 watts or low 150 milliwatts (2.5 wattspossible with BP5A battery pack)

IC-02E/04E 2 metre and 70cm Keypad HandportableThese direct entry CPU controlled handhelds utilise a16 button keypad allowing easy access to frequencies.memories and scan functions Ten memories storefrequency and offset. these handhelds have an LCDreadout and power output is 2 5 watts or low 0 5 watt5 watts is possible with the IC-BP7 battery pack orexternal 13 8v DCl

IC -12E 23cm HandportableSimilar in design and style to the 02E04E this 1296Mhzhandheld utilises 1COM s experience in GHZ technology,gained by the excellent 1C -1271E base station Poweroutput is 1 watt from the standard BP3 nicad pack.external 13.8v DC powering is available to the top paneljack With the growing number of repeaters on 23cmThe IC -12E makes it an ideal band for rag chew contacts

ALSO AVAILABLE FOR ICOM HANDPORTABLES AREA LARGE RANGE OF OPTIONAL EXTRAS INCLUDINGA VARIETY OF RECHARGEABLE NICAD POWERPACKS, DRY CELL BATTERY PACKS, DESK CHARGERS.HEADSET AND BOOM MIC, LEATHERETTE CASESAND MOBILE MOUNTING BRACKETS

[You can get what you want just by pickingup the telephone Our mail order departmentoffers you free same day despatch wheneverpossible instant credit interest free H PBarclaycard and Access facility 24 houranswerphone SPTVIrP

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Tel: 0227 363859SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 17

Andy Emmerson G8PTH puts you in the picture

CARWIG as you'll remember, is theIGEuropean Amateur Television Work-ing Group, founded a little more than ayear ago. The second internationalmeeting was held at Crick in May,coinciding with the BATC's annualconvention there. Delegates came fromSwitzerland, Italy, France, Germany.Holland, Belgium and Britain, while onlyour Austrian colleague was unable toattend

One of the decisions taken at themeeting was to invite other Europeancountries with ATV activity to join theworking group and consolidate ourefforts, with the hope of becoming trulyrepresentative of all European televisionamateurs. Letters accordingly went off inthe direction of Sweden, Norway andSpain (we don't know of ATV operation inother countries), and so far HelmerSM6CCD has replied from Sweden. Hesays that, as far as he is aware, there aresome 10 to 12 ATVers in Sweden and thusthey do not have an ATV manager. Hewill however, act as contact and feelsthat international cooperation is veryimportant for all ATV -interestedamateurs in the future.

Repeater newsReaders may be interested in another

list of ATV repeaters to add to that whichI recently published for Europe (right).This time they're for Down Under, justthe thing for the next big lift! A similar listfor North America would be useful; cananyone supply this?

There are now more that 50 ATVrepeaters in Europe, of which some 12are in the UK. An interesting develop -

Area

ATV repeaters in New Zealand

Callsign Input - MHz Output - MHzVision Sound Vision Sound

Gisborne 1251.25 1256.75 443.25 448.75Kaiti Hill

Belmont 443.25 448.75 614.25 619.75

ATV repeaters in Australia

Area Callsign Input - MHzVision Sound

Output - MHzVision Sound

Canberra VK1RTV 426.25 431.75 579.25 584.75Wagga VK2RTW 444.25 449.75 579.25 584.75Bendigo VK3RMZ 426.25 431.75 579.25 584.75Melbourne VK3RTV 444.25 449.75 579.25 584.75Townsville VK4RAT 444.25 449.75 579.25 584.75Brisbane VK4RTV 426.25 431.75 579.25 584.75Central North VK5RCN 426.25 431.75 444.25 449.75Central North VK5RCN 579.25 584.75 444.25 449.75Adelaide VK5RTV 426.25 431.75 579.25 584.75Adelaide VK5RTV 444.25 449.75 579.25 584.75Perth VK6ROD 426.25 431.75 579.25 584.75Perth VK6RUF 426.25 431.75 579.25 584.75Devonport VK7RAE 444.25 449.75 579.25 584.75North West VK7RTV 444.25 449.75 426.25 431.75

ment is the planned 10GHz 'gateway' forGB3TV (Dunstable Downs). To be situ-ated in the Milton Keynes area, the ideais that this should act as a remote base tofeed signals into and out of the repeater.Much of Milton Keynes is shielded fromthe repeater site, but a well -locatedstation can of course access the repea-

European ATV Working Group members at the Crick Convention

ter. If poorly situated stations could 'see'this remote base station with 10GHz, theycould then use it to get into the repeaterproper. It's a novel concept and I shallkeep you informed of progress.

The BATC has been liaising with theRSGB's microwave committee on TVworking frequencies for 10GHz and hasalso agreed a 13cm bandplan. TheWorthing video repeater group isproposing a 2.3GHz repeater co -sitedwith their 23cm machine at Brighton(GB3VR). The Bristol repeater, GB3ZZ, isnow fully operational, as is GB3TV's newhigh -power output stage. No applica-tions have been made yet for theproposed repeaters at Emley Moor(Yorkshire) or Nottingham.

News from RugbyGB3RT, the Rugby TV repeater, goes

from strength to strength and is hoped tobe fully licensed by the time you read this(fingers crossed!). The transmitter hasbeen fully air -tested (approximately 210hours to date) and all necessary adjust-ments have been carried out. The outputpower is set at 10 watts, resulting in anERP of 25 watts. This is the maximumcurrently allowed by the DTI for videorepeaters - we wait to see if Cambridgegets the kilowatt ERP it requested!

The receiver is running continuouslyand the sound ident generator,

18 please mention RADIO 8 ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

incorporating a Morse code EPROMkindly programmed by Geoff Mather ofthe Worthing group, has also been air -tested.

The repeater continues to operate inattended relay station mode, with regu-lar QSOs and good picture reports. Mostof these tests are carried out on Fridaysand Mondays, according to the commit-ments of Mike G610M, on whose pre-mises the repeater resides. Full spe-cification CCIR pre -emphasis and de -emphasis are now incorporated, and toobtain the best results users shouldensure that their transmitters and

receivers are similarly equipped.The repeater's licence application has

passed the Radio Investigation Serviceand site clearance stages, and is nowwith the frequency planning committee.The box has been funded by the bring-and-buy sale held at May's BATCconvention, and also by the followingkind donations: Bob G6GSG, main powersupply; Barry G6I KC), erection of repea-ter aerials; Worthing and District VideoRepeater Group, two Alford Slot aerials;David G1GPE, glass fibre stub mast; andMike G8DLX, interdigital bandpass filterand brand new Microwave Modules

receive preamplifier.

Sign -offDon't forget this Autumn's contests!

Saturday 12th and Sunday 13th Septem-ber see the international ATV contest.This is for fast -scan TV on all bands,lasting from 1900 to 1300 local time. TheAutumn Vision contest is held on Sunday25th October on all bands, all scanspeeds from 0001 to 2359. Finally, anSSTV-only event on Sunday 29th Novem-ber, from 0001 to 2359 local time. See younext month, when I hope to include yourcontribution! IR*

This month we attempt the hazardousI feat of looking into the future.

Luckily there are some firm steers, so notmuch guesswork is involved!

PRS, SSR and PARSRemember PRS, the personal radio

system? It was (and is) a cross betweenCitizens' Band and cellular radio. provid-ing private communication between tworadio users. You could call it anautomatic selcall (selective calling) sys-tem. As it doesn't use an exchange youcan only link up with people withinnormal radio range, but conversationscost nothing once you have the equip-ment - and a licence!

PRS is big in Japan and is also inoperation on the 933 and 934MHz bandsin Switzerland, where it appeals tobusiness and private users alike. It is dueto come into operation in Holland as welllater this year.

The concept also has some appeal tothe British authorities, who promptlyrenamed it SRR, short range radio. Sincethen, there has been pressure fromindustry to design a higher specificationsystem which would use the sametechnology as the next generation ofdigital cellular car phones and offerextra facilities.

This has been given the title PARS,private advanced radio system, and thereis now some momentum to develop thiscommercially for sale throughoutEurope. It was recently announced thateleven European electronics firms,including British Telecom, Plessey, GEC,Philips and Racal, have formed a jointventure to develop PARS. We'll have tosee if this takes off, and also whether itwill be as affordable as the currentgeneration of 934MHz sets. The chancesare that it will ...

DTI speaks outSome useful information was con-

tained in a recent talk given to the annualgeneral meeting of the 934MHz Club UKby Mr Robert Pringle of the Departmentof Trade and Industry's Radio Com-munication Division. You can read thefull text of his speech in the latest editionof the club's magazine (you are a

NETWORK934

Andy Emmerson G9BUP

member, aren't you?), but here are someof the high spots:

'Around the middle of last year mysection within the division began torevise the entire licensing process of CB- the actual document itself and theregulations and restrictions. This wasprompted by our decision to launch aEuropean 27MHz system, which will beavailable from 1st September this year,and the need to amend legislation toallow this to happen. We also needed tolook at 934 since the two are licensedunder the same document.

'We were pleased to talk to repre-sentatives of major national user groupsfor both frequencies. Members of thecommittee of the 934MHz Club UKactually took a leading role in puttingforward suggestions for the develop-ment of the licence, pointing out ruleswhich were considered unnecessary andhelping us to consider areas that,perhaps, we had not considered before.

'We had a big meeting towards the endof last year which the club, together withother groups, attended. We put forwardour proposals for the development of thelicence and received back a reactionfrom the groups, and I am pleased to saythat we were able to take on board mostof the things that were put to us.

Fewer restrictions'The most important result of the

review is that we are going to liftrestrictions on antenna use for 934MHz.We are going to allow, in future, 12element antennas of any configuration,providing each element does not exceed17cm. You may use 12 element beams,

collinears or slots - whatever you want-providing it is within the 12 element limit.

'We were considering controls onpreamplifiers and, at 27MHz, we had torespond to interference problems byprohibiting them. However, it is widelyrecognised that they are used at 934MHz.The 934MHz Club UK pointed out theextensive use of them and assured usthat they have had no problems. I ampleased to tell you that you may continueto use your preamplifiers.

'We also looked at the attenuationruling contained in the present CBlicence. which requires attenuation tothe signal by 10dB if the antenna is morethan 10 metres above ground level. Thisrule, it was felt, was unfair to operators,particularly at 934MHz, who are inlocalised hollows and who may be able toerect masts with the appropriate localauthority permission.

'We undertook an extensive amount ofmonitoring and field tests, and experi-enced no interference problems in thefield. I am pleased to tell you that theattenuation ruling will disappear onSeptember 1st.

Licence revision'We are also conscious that, as people

get more involved with their hobby, theytend to buy more equipment. At themoment we charge you more if you usemore than three sets. As I have alreadytold you a moment ago, we are introduc-ing an additional service-the European27MHz system - and this means thatpeople are going to have more and moreequipment.

'We felt it was, perhaps, an unfairrestriction to license on the basis of thenumber of sets. I am pleased to be able totell you that, as from 1st September youwill be able to use any number of CB setsunder the cover of a single licence.Other changes we have in mind will limitthe current hire clause, which is per-ceived as being a loophole. It hascertainly been mentioned to us by usergroups as being unfair, so we are goingto restrict licences to cover individualpersons or anyone under their supervi-sion. This is in line with other govern-ment policy such as your driving licence,

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 19

NETWORK 934for example. All changes will, I point out,come into effect on 1st September 1987.

More to pay?'One question I will not be able to

answer concerns the licence fee. Thelicence fee has stuck at £10 sinceNovember 1981. I do not need to tell youthat inflation would suggest that the feeshould now be at least up to £14. I think Iwould be misleading you if I said we werenot considering adjusting the fee. Sinceall these other changes are happeningon 1st September it would seem to be agood date for an adjustment, but I ampleased to assure you that we do notintend to adjust the fee to a vast level.

Or lose 934?'One question that always crops up

when people telephone or write to meabout the 934MHz radio frequency: "Arewe going to lose our service? We haveheard that the DTI is going to shut down934." You can take it from me today thatwe are not going to shut down 934: itsfuture is assured for the foreseeablefuture.

'The Government will be reviewing allCB allocations in 1990 and this is part of arolling programme. For example, at themoment the defence spectrum is beingreviewed. The CB review is obviously ona smaller scale but whatever the out-come, whatever the recommendationsmade by the minister, he has committedthe Government to allowing a good lifefor users' sets, and we are taking this tomean that the specification will still beavailable up to at least the mid 1990s. Soplease do not worry about buying newequipment, thinking that it will becomeout of date.

Looking further afield'Another area that raises queries is the

scene in Europe at 900MHz. A lot of youwill know that there is a Japanese systemcalled 'Personal Radio Service' thatoperates at 903-905MHz in Japan. This isoften seen as being a second or third

generation CB system. European admi-nistrations, the UK amongst them, havebeen looking to introduce such a systemin the 933-934MHz bracket, and, indeed, ithas been agreed in Europe to leave thisparticular slot in the spectrum for CB andpersonal type radio systems. The goodnews is that if we were to introduce sucha system it would, in effect, be giving youmore of the spectrum to use and the twosystems could live quite happily side byside.

'The not quite so good news is that theUK will not be introducing the system forat least three years. This is to allow thedevelopment of competing technologywhich is a British -inspired move towardsa digital system. I can tell you that, inadvance of a European -wide agreementon the introduction of one or othersystem, some administrations haveunilaterally opted for the Japanese -stylesystem. The Swiss you are already awareof, the Netherlands plan to introduce onelater this year and the Spanish, I

understand, have one available althoughI do not think it is being used very much.

'The European front is an importantone and I am pleased to say that it is acase of Europe catching up with the UK.We knew that 900MHz was perfectlypracticable for mobile radio and forhobby communications back in 1980/81and you, the users, have recognised thatit is technically difficult to get going.However, once established it can pro-duce a very high quality service.

Friendliest service'Finally I would like to relate a few of

my hopes for the future. One is that the934MHz band gets much more popular.We have a quorum of a few thousandlicensed users, who operate to a highstandard. They enjoy, I think, one of thefriendliest services on radio, certainlycompared to other CB and. I would say,licensed amateur services as well. Therelaxed, informal but well -orderedatmosphere is, I think, a treat to listento. I hope that this develops and

continues as the band expands.'I hope also to see more commercial

use of 934. A lot of you will say "What's hetalking about? We don't want businesscoming onto the band and taking usover." Well, I do see there is a very realneed for a simple, local system for verysmall businesses. I am thinking of,perhaps, a small shop with a singledelivery van. The 934MHz band is a goodslot for those people to use, and it is agood way of defending the band andensuring its survival into the long-termfuture. The Government is very keen topromote business use and business hasfirst call on the spectrum - even abovethe Ministry of Defence. We have seenthe defence spectrum review and minis-ters are pressing for the spectrum to betaken away from the military and allo-cated to private users. If the 934 CB bandis also used by small businesses, that is abig bonus for it and will help to defend itin the long-term.

'My other hopes are that the 27MHzservice takes on board some of theoperating practice of the 934MHz sys-tem. and I also hope that the European27MHz system is the prelude for Euro-pean systems elsewhere.'

That's it - I hope you feel reassured. Icertainly find this very encouraging andagree with nearly all these thoughts. Bythe way, if you have any further informa-tion on the Dutch or Spanish servicesplease let me know. We can then sharethe knowledge. ICI

Keep up to datewith developmentson 934MHz with thefirst and bestcolumn on thesubject

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TRIACS diacs 25pNEC Triac ACOBF 600V TO 220 11/C2 100/130NEC Triac 150L Tab TO220 6A 400V 2/C1ACOV8FGM 800mA 400V 1092 TRAC

3Diacs 4/1;11TXAL225 8A 400V 5mA gate 2/11 100/135TRAL 2230D 30A 400V isolated stud C4 each

CONNECTORSCentronics 36way IDC plugCentronics 36way IDC sktCentronics 36way plug (solder type) C40USED Centronics 36W plug 6 socket C3'D' 9 -way El. 15 -way £1 .50: 25 -way LS37 -way C2: 50 -way £3.50, covers 50p ea

WIRE WOUND RESISTORSW21 or Sim 2.5W 10 of one value ClRIO OR15 OR22 2R0 4R7 5R0 5R6 8R2 lOR 12R 15R 18R 20R22R 27R 33R 36R 47R 56R 62R 91R 100R 120R 180R 390R430R 560R 680R 820R 910R 1K2 11(5 1K8 2K7 3K3 3K0 5K010K

R05 (50 milii-ohm) 1% 3W 4 for ClW22 or Sim 6W 7 of one value ClR47 R62 IRO 1R5 1R8 3R3 6R8 9R1 10R 12R 20R 24R 27R 33R51R 56R 62R 68R 100R 120R 180R 220R 270R 390R 560R

KEYTRONICSMAIL ORDER ONLY

P.o. Box 634Bishops Stortford, Herts, CM23 2RX

TELEPHONE: 0279 505543 ADD 15% VAT TO TOTALELECTRONIC COMPONENTS BOUGHT FOR CASH

100/C1.50100/C3

10/C1100/C3100/C4

e5p

04 10. C3.50C4

620R 910R 1KO I K2 1K5 1K8 2K7 3K3 3K9 4K7 8K2 101< 15K16K 20KW23 or Sim 9W 6 of one value C1R22 R47 1R0 1R1 3R0 15R 56R 62R 68R 120R 180R 220R 300R390R 680R 1K0 I K5 5K1 10KW24 or Sim 12W 4 of one value ClR50 1R0 2R0 6R8 9R1 10R 18R 22R 27R 47R 56R 68R 75R 82R100R 150R 180R 200R 220R 270R 400R 620R 11(0 10K 15K

PHOTO DEVICESSlotted opto-switch OPCOA OPB815T2 Ni L5871 77

018 Photo transistor

60:1.30onev

C1TIL38 infra red LED 5/C1OP12252 Opto isolator 110pPhoto diode 50p 6/C2MEL12 (Photo darlington base n/c) 50pRPY58A LDR 50p ORP12 LDR 70pLEDs RED 3mm or 5mm 12/11 100/C6GREEN or YELLOW 3 or 5mm 10/11 100/C6.50FLASHING RED OR GREEN LED 5mm 50p 100/C38

SUB MIN PRESETSHORIZONTAL1K 4K7 10K 22K 47K 1 M 10M 15/C1 100/C5

MULTITURN PRESETSlOR 20R 100R 200R 250R 500R 110p2K 5K 10K 22K 50K 100K 200K 2K2 2K5 47K 500K 2M2

IC SOCKETS6 -pin 15/t1 8 -pin 12/11; 14 -pin 10/11.00; 18/20 -pin 7/£1:22/24/28 pin 4/11 40 pin 30p

TRIMMER CAPACITORSsmallSmall all types 5/50pGrey 1 5 to 6.5pF Grey larger type 2 to 25pF purple 3pF to50pFTransistors 2N4427

10/C8"1Feed Thru Ceramic Caps 1000pF

SOLID STATE RELAYS NEW 10A250v ACZero voltage switchingControl voltage 8-28v DC ELIO40A 250V AC Solid State relays CISPOLYESTER/POLYCARBCAPS10/3n3/5n6/13n2/10n I% 63v 10mm looms10n/15n/22n/33/47n/68n 10mm rad

100/C11,801uF 250V Mullard/Siemens AX 1=1 100/Ce100N 250V radial 10mm 100/1324 160v rad 22mm 100410470n 250v AC X rated rad WEI33n/47n 250v AC X rated rad 15mm 10/C1.00lu 600V Mixed dielectric 00000Paper cap, I uF 700V ideal for electronic Ignition

01.00

BEADTHEIIMISTORSGLASS BEAD NTC Res Cu 20'c 808250R 1K2 50K 220K 1M4

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MONOLOTIIIC CERAMICCAPS10n 50V 2.5mm 100/C4.50100n 50v 2.5mm or 5mm 100/C8100N 50V axial Shortleads 100/C310N 50y 100/C3100N 50V dil package 0.3' rad 100/C1010N 50y dil package ar rad.14/100

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 21

La3oraTorupower SJOOLU

loL Pavia elLveserIf batteries are not to form the main

method of providing power to smalltransistor projects, the constructor willneed to build a variable voltage powersupply unit to replace them; the cost ofelectrical power from batteries is some2,000 times the cost of mains power.

A quick evaluation of the requirementreveals that the supply should have thefollowing characteristics: mains derivedpower; output voltages of 3, 6, 9V, etc tocover the battery voltages normallyused; current capability in excess of 1Aas a nicad replacement.

It is possible to build a PSU to fit thisspecification using a single CA3140 op -amp and one unregulated input voltage,but the author did not like the resultingmethod of setting the output voltageusing a potentiometer even if a 10 turnpot could be used to improve accuracy.

It was decided to use digitally selectedoutput voltages using a group of threeBCD encoded thumbwheel switches.These switches are used to representthe output voltage in tens, units andtenths of a volt. The tens switch is limitedto a maximum setting of 3 and a minimumof zero, the values 4 to 9 being made non -selectable by stops on the tens switch.Thus, the output voltage can range from0.1 to 39.9V in steps of 0.1V.

The problem is that to be able to do thisthe op -amps need to have a separate±15V supply from the unregulated mainsupply at 55V, but as this is at very lowcurrents a small secondary transformerand a simple fixed power unit is built onthe main PSU to supply the necessaryvoltages.

The design of the power supply unitderives from the circuit in Figure 1. A

Fig 1 Basic supply

Rs

-Input

Itotoritnc.

input

Fig 2 Supply for increased output voltages

reference voltage is provided by aseparate circuit into the non -invertinginput to the op -amp 101, and a portion ofthe output voltage selected by thepotential divider R2 and R3 is placed onthe inverting input of the IC. Providedthat the IC does not load the potentialdivider due to its input current, then ifsay R3 is 10Kohms and R2 is 90Kohms theoutput voltage will be 10 times thereference. The resistor R1 is used for thecurrent limit circuitry, but this is notshown in this diagram. Now, if thereference comes from a potentiometerwith one side grounded, the output canrange from zero to theoretically 10 timesthe maximum reference voltage.However, the op -amp itself limits theavailable outputs that can be obtained.

How if worksIf we look briefly at the op -amp inputs

and outputs, only expensive and difficultto obtain types can operate with supplyvoltages in excess of 36V, and of thecommon types the bipolar output stagelimits the maximum finished powersupply output voltage to a guaranteedvalue of 31V. Consequently, in Figure 1the maximum output voltage from thePSU will be 29.8V. In this diagram thetransistor Tr1 will have a voltage drop of0.65V and R1, which is the current detectresistor for the current limit circuit, willalso show a maximum voltage of 0.65V atthe point of operation. As for theminimum output voltage available, onlythe CA3140 will operate correctly with itsinputs both close to the low input voltagerail, but the circuit is still unable to giveus the full range of zero to 40V required.

MO

Fig 3 Basic reference generator

a Output

22 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Figure 2 cures all problems caused bythe op -amp limits. In this circuit, theseparate supplies for the op -amp IC2allow the reference voltage to vary fromzero to between 12 and 14V, dependingon the IC type, before the IC causes anyproblems. Negative reference voltagesare obviously not acceptable, as the mainoutput cannot go below zero. With R7 andR8 fulfilling the same function as R2 andR3 in Figure 1, the output could vary up to120V, if the transistors can cope withthese voltages.

Theoretically, this can be extended sothat if we used 500V breakdown transis-tors and altered the feedback ratio byincreasing the value of R7, increasingthe unregulated input voltage to 480V,then we could make a 475V output PSU.The transistors used in this project allhave breakdown voltages of 80V or more,so outputs up to 75V are possible if themain unregulated voltage is increased.However, the power dissipation of thepass transistor will be exceeded if theoutput current exceeds about 1A.

In Figure 2, transistor Tr2 is turned onby the action of R4, whilst Tr3 under thecontrol of IC2 attempts to turn Tr2 off.Due to the inverting action of Tr3, thereference signal goes into the invertinginput of the IC and the portion of theoutput voltage goes into the non -inverting input. D1 is included to provideprotection for Tr3 in cases where theoutput of the IC goes negative. It ispossible for the voltage into this transis-tor to be -15V when the op -amp demandsa quick turn on of the output current dueto transients and, as no transistor is ableto stand a reversed base -emitter voltageabove 5V, D1 limits this reverse voltageto 0.65V. It is frequently necessary to adda capacitor between the inverting inputand the output of the IC to suppress thehigh frequency loop of IC2, Tr3, Tr2 andthe resistors, this being a simple methodof adding extra frequency compensationto that which is internal to the IC.

Up to this point we have ignored thereference voltage, but this is derivedfrom the simple inverting amplifier stageshown in Figure 3. In this amplifierconfiguration the operational amplifiertries to maintain the voltage at itsinverting input at ground potential,known as the virtual earth point. If a

negative potential is applied to the endof R9 then a current will flow through R9and, since the op -amp input cannotsupply current, the op -amp output willrise to a positive voltage sufficient todrive the same current through R10 andretain its input voltage at virtually zero.

R11 is a compensation resistor toovercome the temperature effects ofinput bias current and should be of avalue similar to the parallel resistance ofR9 and R10. By keeping a fixed voltage atthe end of R9, but allowing the value of R9to be altered - in our case by switching aparallel bank of resistors controlled bythe BCD thumbwheel switch - andprovided that the correct values of

Or 1

36V

0 550

F79 4 Input powersupplies

CO1000.2SV

.C3711115

CO100n

0 1511 to 1C.

TkomOwOoeloo...1

parallel resistor are chosen, the outputvoltage of the IC in Figure3can be variedin 0.01V steps up to 3.99V. This is, in fact, asimple digital to analogue converter.

Having broken the circuit into itsconstituent parts, it is now easy toexamine the full circuit shown in Figures4, Sand 6. T1, Br1 and C1 provide the main+55V used by the control circuit, whilstT2, Br2, C2, C3 and the three -terminalregulators IC3 and IC4 give the + and-15V supplies to the op -amps 101 andIC2. The capacitors C4 and C5 help toincrease the stability of the output of theregulators and also assist with noisereduction. The voltage for the input tothe DAC comes from the 7905 IC5, butdue to the manufacturing limits on thisdevice the output voltage may varybetween 4.8 and 5.2 volts. I will giveadvice on how to cope with this toleranceproblem later.

C6 provides noise reduction for thissupply. The tolerance on the + and -15Vsupplies in no way affects the operationof 101 and IC2. An interesting problem isthat the three terminal regulator, IC5,does not like to work into an open circuit

represented by the thumbwheelswitches being set to zero or into adigital voltmeter with a typical inputimpedance of 10Mohms, and to give astable ouput voltage a current leakresistor, R37, has to be included.

The reference generatorThe similarity between Figure 5 , the

reference generator, and Figure 3 canbe seen with the nominal input of -5V.R1, R2, R3 and R4 in the prototype were0.1% tolerance resistors, as errors inthese resistors have the greatest effecton the output of the DAC. Althoughsingle resistors of the correct values (800ohms for R1 + R2) are available to specialorder, it was easier to use standardvalues and have two resistors in series.The parts list gives the supplier of the0.1% resistors. 1% devices may be usedbut with a corresponding error in theoutput from the DAC.

A similar problem exists with thevalues of R5, R6, R7, R8, R11, R12, R13 andR14 and, although the Author was able toobtain suitable single resistors for thisarticle, it was felt better to select more

SV

C3.11000. ZOO T

IC41

CO

ICS"Os

0,

0 'MY lo IC.

CO100n

SC io

Fig 5 Reference generator

00. OOOOO

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 23

LABORATORY POWER SUPPLYcommon resistor values. As the 7905'soutput can be between 4.8 and 5.2V, Vr2needs to be included in the circuit tocope with this variation.

Let us look at the way that the valuesfor the resistors in the DAC arecalculated. The easy way is to workbackwards from a nominated resistorvalue for one of the thumbwheel lines. Itwas assumed that the 8 line had a 1K0resistor equivalent to R9 in Figure 3, andthat the 7905 output voltage was accur-ately 5.0V. With the values selected andthe information that the op -amp will try tohold the inverting input at groundpotential, a current of 5mA flows awayfrom the op -amp input and the op -ampmust supply this current from its outputpin via R10 of Figure 3. But we also knowthat with the thumbwheel set on 8representing an 8V output, the DAC mustgive a 0.8V output due to the ten timesgain of the next stage. Thus, the value ofR10 can be calculated as we have thevoltage 0.8V and the current 5mA, and

this gives a value of 160 ohms.To allow for the tolerance of the -5V

regulator, the same calculations can becarried out for the highest and lowestvalues for the -5V supply; in practicalterms the values become a resistor of 150ohms and a 20 ohm pot. The rest of thevalues for the DAC resistor bank can becalculated very easily, as the values willbe in the inverse ratio to the switchsettings. Vr1 and R13 provide a zeroingfor the output, with no resistor selectedby the thumbwheel switches. By the useof Vr1 and Vr2, the output from the DACcan be set to give outputs from 0 to 3.99V.

The main regulatorAs in Figure 2. the main circuit of

Figure 6, showing the main regulator,consists of an op -amp controlling atransistor Tr3, with the feedback comingfrom the combined resistors of R21, R22,R23 and Vr3. The 56pF capacitor, C7,provides a high frequency short aroundthe feedback network, speeding up the

input fig..YO

N29 Tr 4

IN1

1132

231

Tr 3

1130

NSA

-

1124

527

0 111V

A

it

117,

52

5V3

AV -

-10V

229

Orange

AC

No

AC

M.M.Input

Orne

Oty

14471Ink

0- 3.99Vale **

Fig 6 Control unit

1123

7

? 0 1 gm. re

00return

.0 *****

.Output

Snot

Thunnrovhiti mot

300

0 0 0.-4.-011put *nor

owOtennd return

F7g 8 Off bandconnectors

00

Ribbon cItl

0

0Ti

1112A0

Output Output

high frequency response of this part ofthe circuit.

In the prototype, the feedback systemhas been made variable so that anaccurate setting of a divide by ten can beobtained. In practice, this setting can beignored, provided that 1% or bettertolerance resistors can be used for thefeedback loop as the variability in Vr2and consequently small offsets of the 0 to3.99V output of IC1 can be used to correctfor any error in the feedback to IC2.

In the fixed resistor case, the values ofR21, R22 and Vr3 become fixed 1%resistors of the values 6K8, 1K2 and 1K0ohms respectively. Once again, Vr4 andR36 provide zeroing of the output of IC2when its reference input is at zero. As inFigure 2 , D1 protects Tr3 from negativeinput voltages, with R35 as a current limitfor the diode. C9 is an additionalfrequency compensation capacitorneeded to overcome the larger loops'(IC2, Tr1, Tr2, Tr3) high frequencyresponse, as at some voltages there maybe a tendency to go into high frequencyoscillation. C10 and R33 provide a switch -on soft start signal in that whilst C8 ischarging, Tr3 will be partially turned on,limiting the output voltage.

The pass transistor (Tr2 of Figure 2 )becomes a Darlington transistor of Tr1and Tr2 in Figure 6. R32 is again the turnon resistor and the resistors R30 and R31act to give stability to the Darlington, justas the inbuilt resistors of a singlepackage Darlington transistor would do.A current limit selection switch, S1, hasbeen used to enable the choice of 15, 150or 1500mA current limit settings; thelower the resistance selected the higherthe limit current. This is a three -positionswitch, ie, two-way plus centre off, beingthe lowest cost alternative for this itemconsidering the fact that the switch willcarry the full output of 1.5A. It will benoted that neither of the output lines hasbeen connected to the mains earth sothat the unit can be used with outer itemsof equipment that may already haveearth connections.

The output error sensing of the supply(Figure 6, right-hand side) can be seen tobe separate from the two output rails. Inall supplies it is advisable to arrange that

Table 1

non Connection

1 1 of tens thumbwheel2 2 of tens thumbwheel3 C of tens thumbwheel, the -5V supply4 no connection, remove wire5 no connection, remove wire6 1 of units thumbwheel7 2 of units thumbwheel8 4 of units thumbwheel9 8 of units thumbwheel10 C of units thumbwheel, the -5V supply11 no connection, remove wire12 1 of tenths thumbwheel13 2 of tenths thumbwheel14 4 of tenths thumbwheel15 8 of tenths thumbwheel16 C of tenths thumbwheel, the -5V supply

24 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

LABORATORY POWER SUPPLYthe point at which the output error issensed is as close to the item beingsupplied as possible. In the case of thisproject, the actual output socket waschosen as the sensing point, althoughsome constructors may choose to fitseparate sense and supply sockets. Inthis case, extreme care must be taken inensuring that when in use the senseconnection is always made, and it may beadvisable to add two 50 ohm resistorsbetween both source and sense lines asa safety precaution. The resistive valueof the normal connecting wires willswamp the effect of these 50 ohmresistors.

The only extra item is the current limitsystem, using the resistors R24 to R27,transistor Tr4, opto-coupler IC6 and theopto-diode current limit resistor R29.The switch S1 selects a value of resistorin the current sensing circuit so that atthe current limit set the transistor Tr4 isturned on. The current that flows throughTr4 illuminates the diode in the opto-coupler and turns on the opto-transistorconnected between the controlling tran-sistor Tr3 and the +15V supply. When Tr3turns fully on, the collector voltage willbe reduced to about 0.2V, which isinsufficient to turn on the output Darling-ton transistor, and the output voltage willfall to zero independent of the signalfrom the control op -amp, IC2.

Although it was originally intended touse CA3140 op -amps, the selection of asystem with a separate power supply forthe ICs means that any FET input op -ampcould be used, but modifications to thezeroing circuits may need to be madesince many other op -amps may notaccept the 4K7 ohm resistor in additionto the 10kohm pot. Theoretically, thegood old 741C could also be used forboth op -amps, but in practice the higherinput bias current for this and otherbipolar input devices means that errors

0 to t o0/P rrrrr no

Ground°return

To Tr 1

55V 0

GPID m I rom Clo

CND to0/P ockI

in the output due to this input currentwould occur.

ConstructionFigure 7 shows the layout of the

components on the main PSU, whilstFigure 8 shows the connections off theboard. The only components not on thePCB are the two transformers, the mainreservoir capacitor C1, the main bridgeBr1, the thumbwheel switch and the passtransistor Tr1 which is mounted on a1.1'C/W heatsink. The thumbwheelswitch is connected to the board througha ribbon cable and an IDC 16 -way plugand socket.

Initially, solder into the PCB the two8 -pin DIL IC sockets and the IDC socket.The IDC socket has a notch cut into one

Fig 7 Component overlaySeel Currnt hmst serttch

0

1W.11":1,127

3

W ,8

face and this should be orientatedtowards the resistor bank. Failure to dothis will mean that the connections in theribbon cable will not be valid, Table 1.The opto-coupler has only 6 pins and inthe prototype another 8 -pin DIL socketwas used, but with pins 1 and 8 removedbefore soldering the socket to the board.

Before proceeding any further it isessential that the constructor check thateach connection on the IDC socket isseparate from its neighbour. With only0.1 inch between the pins and with trackspassing between the gaps it is very easyto form a solder bridge that will give themost peculiar effects with the DAC. TheAuthor, so far, has yet to solder an IDCsocket down without forming at least 1bridge, but luckily the bridges are easy to

10C Sockt

Subeedueretrnsformer

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 25

LABORATORY POWER SUPPLYremove using a small modelling knife.

Incidentally, a very small solderingiron is needed - anything with a tipdiameter over 1mm is asking for trouble.The Author suggests an iron with a 0.4mmtip to make the connections easier. Afine solder is also needed and 22 gaugeseems suitable. Table 1 gives the cablenumbering for the ribbon cable. The IDCplug can only fit one way round in thesocket and the ribbon cable is pressedhome into the back of the plug with thered polarity lead on the left-hand side, ieclosest to R1.

Check carefully to see if the IDC plug issupplied with an extra supporting clip, asthe ribbon cable will be bent back on

itself with the extra support and may endup coming out over the PCB rather thanaway from the board. The rough end ofthe cable can be cut back level with theedge of the plug using the modellingknife. Using Table 1, the wires can besoldered to the three thumbwheelswitches and the setting for the max-imum and minimum positions for the tensunit can be set by the insertion of stops inthe small holes on the side marked Eand J.

The rest of the components can befitted to the PCB using Figure 7 as theguide. There are no special problems insoldering any of these components asthere is plenty of space around all the

Parts ListResistors (all 0.25 watt tolerance 1% unless stated)Available from Verospeed. Stansted Wood, Eastleigh, Hants S05 4ZY

680R 0.1%120R 0.1%220R 0.1%1BOR 0.1%6K81K22K01K068K12K20K10K15OR4K7470R8K243R4R7R47 3 watt 5%6R875R2K7220K

R1

R2R3R4R5R6R7, 8, 9, 35R10, 23, 29, 37R11R12, 32R13, 14, 15R16, 20, 28. 34R17, 18R19, 36R21R22R24R25R26R27R30R31R33

Vr1, 4Vr2Vr3

CapacitorsC1C2, 3C4, 5, 6, 10C7C8C9

SemiconductorsI C1 , 2

IC3IC4IC5Tr1Tr2Tr3, 4Br1Br2D1

10K 20 turn pot20R 20 turn pot500R 20 turn pot

4700µF 63V electrolytic radial470µF 63V electrolytic radial0.1µF ceramic56pF ceramic0.01µF ceramic470pF ceramic

CA3140E7815 regulator, 78L15 may also be used7915 regulator, 79L15 may also be used7805 regulator, 78L05 may also be used2N3055MPSUO6MPSA06Any 200V 2A bridge rectifier, such as BR82DW004 200V 1A bridge rectifier1N4148 or similar diode

MiscellaneousHeatsink - Redpoint 6W-1IDC socket and plug, 16 -way30cm of 16 -way ribbon cable - may have to be made from 20 -way ribbon3 thumbwheel switches. BCD encoded. end cheeks and stop set (Maplin)Transformer 0-15 + 0-15V. 3W each windingTransformer 0-18 + 0-18V 80W torroid (Maplin YK17T)Case to constructor's requirements. noting heatsink positioningMiniature single pole centre off switch

terminals. Layout of the supply in thecase is again up to the constructor,remembering that the case must besufficiently large to allow the heatsink tobe mounted with its fins in a verticaldirection. There are a number of wirelinks on the board, and these simply savethe expense of a double -sided PCB. Thetolerances of the 0.1% resistors can beaffected permanently by overheatingduring soldering, and so a heat shuntmay be advisable just as in solderingsemiconductors.

The main reservoir capacitor with itsmounting bracket can be screwed to thecase at a later stage and the main bridgeBr1 is soldered to the capacitor using itswires to hold it in place. Two wires to takethe 55V to the PCB should also be added.The power transformer has two windingswith 18V ac outputs and the blue andyellow wires are joined to form a singlewinding of 36V ac. The remainingtransformer output wires (the red andgrey) are soldered to the ac input to Br1.The heatsink with Tr1 attached, when inthe vertical position, ensures the fullheat dissipation capability of the heat -sink of 1.1°C/W. With this heatsink powerrating, the power supply is capable ofwithstanding the full current limit of 1.5Aon a continuous basis, although the sinkwill become very hot, reaching about100-C. If the constructor will accept areduced continuous current from thesupply and a reduced time for the 1.5Acurrent limit, then the heatsink may bemade smaller, which will ease theproblem of positioning it on the case.

The problem is that if an overload suchas a short circuit current limit of 1.5Aoccurs and is allowed to continue, thenthe heatsink will be unable to dissipatethe continuous power of 75 watts(actually 55V by 1.5A) without allowingthe pass transistor junction temperatureto exceed its maximum of 200-C and thepass transistor will fail. The PSU will beOK until this junction temperature isreached, and the thermal mass of thesink will keep the transistor in a safecondition for a short time. However, if theconstructor chooses the smaller heat -sink option then he/she can use anovertemperature cut-out (RS part no 331-528) on the heatsink to cut off the supplywhen the heatsink temperature reaches90'C.

Setting up and testingBefore describing the set-up proce-

dure it is possibly a good idea to look atthe errors that occur due to thetolerances in modern multimeters. If weignore the effect that an analoguemeter's current drain can have on acircuit, then in addition each of theranges has a tolerance, indicating themaximum error between the true andindicated readings. For an analoguemeter this may amount to 5%, whilst forlow cost digital meters 0.5 to 1% is morecommon. The problem is that in settingup the power supply unit we must

26 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

LABORATORY POWER SUPPLYremember these errors exist betweenthe ranges.

Having built the unit, ensure beforeinitial switch on that the two ICs and theopto-coupler are removed from theirsockets. Find one of the ground rails (thecentre tap of the transformer T2 is themost suitable) for the negative terminalof the DVM for the voltage tests. Theauthor used a low cost 0.7% tolerancedigital voltmeter for his tests as, likemost constructors, he cannot condonethe expenditure of over £200 on a DVMwith a maximum 0.1% tolerance.

The problem is that when switchingbetween ranges with the same inputvoltage the reading may alter by morethan the factor of 10 expected. Theauthor's meter shows that if the output ofthe DAC is made 1.00V on the 2 volt rangeof the DVM, then on the 20 volt range thereading is 1.01V - your own DVM maybehave differently. This apparent error isinside the guaranteed accuracy of themeter, being less than twice the quotederror of 0.7%.

Check that the voltage across C1 isabout 55V: in fact, anywhere below 80Vthe breakdown voltage of the transistorswill be safe for the supply. Also ensurethat the voltage across C2 and C3 isabout 27V, remembering that, with

respect to ground, the voltage across C3will be negative. Next check the voltagesat the outputs of the three terminalregulators. The + and --15V are on pins 4and 7 of the two IC sockets and the -5V ison the link wires across the spacebetween the resistor bank R1 to R16 andthe IDC socket. The 15V supply voltagesshould be between 14.4 and 15.6 volts ifthe regulators are in spec, and the -5Vshould be between 4.8 and 5.2V. If all issatisfactory at this stage, insert IC1 onlyand if not connected plug in the IDCconnector along with the thumbwheelswitches.

The testing of he digital to analogueconverter consists of setting the zero Vr1and scale Vr2 potentiometers. The op -amp end of R31 is a convenient connec-ting point for this test. Firstly, set thethumbwheel switches to zero and turnVr1 until the output of IC1 becomes zerowith the DVM set on its most sensitiverange normally 200mV full scale. Set thethumbwheel switches to 100 and theDVM to the 2V range. The thumbwheelsetting of 100 represents a 10.0V finaloutput, but this gives 1.00V at the outputof the DAC. If 1.00V is not obtained thenvary Vr2 until the meter shows therequired value.

The full DAC can now be tested as the

reading on the thumbwheel switches willbe reflected in the readout on the DVM,but don't forget the tolerance problem atvoltages above 2V DAC output when theDVM range will need to be changed. Anyproblems that occur at this stage aremost likely to be caused by solderbridges in the !DC socket and can beisolated by looking at the -5V supplied tothe end of the resistor bank, R1 to R10.This test will give an idea of the errors inthe output that are likely to occur due tothe tolerance of the resistors in the DAC.

When the DAC is working correctly,turn off the mains input and allow thevoltages on the capacitors to fall to zeroor the ICs may be damaged on plugginginto the sockets. Insert the remainingICs and switch on again, then set thethumbwheel switches to 002. As thesupply cannot work to zero with anydegree of adjustment left, the value 002gives some play in the system. With theDVM probes across the output, thevoltage measured should be 0.2V and ifnot then Vr4 can be adjusted to give thisvalue. Now switch the thumbwheels to100 and set the output to 10.0V using Vr3(Vr2 if Vr3 has been replaced by the fixedresistor). The only test left is to try themain output at other thumbwheel set-tings to verify that all is correct. ICI

THE COMMUNICATIONSgcicISO AND ELECTRONICS

MAGAZINEIN Regular well-informed columns on various aspects of

amateur communication Up-to-date news on the latest technologyII Simple and useful constructional projects, plus clear

explanations of the theory behind them Delivery to your door by publication date each month Inflation proof -price guaranteed for 12 months

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 27

lat NUSin describing the airways system in my

article on air traffic control andcommunications, which appeared in theJuly issue, I mentioned that the route ofan airway is delineated by VHF omni-range/distance measuring equipment(VOR/DME) and/or non -directionalbeacons (NDB).

The latter is by far the oldest andsimplest aid in use today, for although ithas serious operational disadvantages incrowded airspace, its simplicity, low costand ease of maintenance have ensuredcontinuing use, whilst in many lessdeveloped countries it is the only aidavailable.

The equipment is a simple transmitteroperating on the 250-450kHz waveband.The carrier is modulated by a continuoustone, which is interrupted from time totime to key the beacon callsign ininternational Morse code.

The NDB is used in conjunction withthe aircraft automatic direction findingequipment, sometimes called the radiocompass. To home onto the NDB, theaircrew simply steer the aircraft so thatthe beacon is ahead and in due coursethe facility will be overflown.

Unfortunately, however, when cross-winds are present, the aircraft will bedeflected from its track to the leewardand, although it will still eventuallyoverfly the beacon, its track whilst usingthe aid will be anything but a straightline. This is of little consequence inregions of low traffic density, but incrowded skies, such as over WesternEurope, the deviation from the desiredtrack could cause a traffic confliction orworse. However, for short range use,such as an airport identification beacon,

Aviation ElectronicsPart Two

NDBs are still very useful andeconomical.

The waveband in which NDBs operateis extremely crowded, and often geo-graphically separated beacons share thesame frequency. It is therefore essentialthat the minimum power necessary isused and that this level is carefullymaintained at all times.

Within the United Kingdom the signalstrength of each NDB is checked daily bythe Civil Aviation Authority from theirmeasuring station near Rugby, and anydeviation from the specified level isquickly followed by a request for correc-tive action. Such is the congestion on thebeacon band that airports wishing toextend their facilities have been knownto wait years for an NDB frequency tobecome available.

The third major problem with NDB isthat as it operates on the LF band itsuffers heavily from static interference.This is even more evident in tropicalregions, where I have heard experiencedpilots say that in these areas the radiocompass needle invariably points at thenearest electrical storm! To overcomethis difficulty to some degree, beacons intropical countries frequently run highpower, 1kW being common, comparedwith 10-200 watts being more usual intemperate climates.

To overcome these problems, the VHFomni-range beacon (VOR) wasdeveloped. In this, the course informa-

Airway

NDB Aircraft track

(al Track under still air conditions

Wind

Airway

NOB

.

i

(b)Effect on aircraft track in crosswind conditions

lel

THE Ation is provided by the beacon, so thatregardless of wind speed and directionthe approach path will always be astraight line. Furthermore, by using VHF,static problems are eliminated and theinherently short range of VHF transmis-sions ensures that frequency sharingproblems are minimised.

VOR operationVOR operates in the 112.0-117.9MHz

waveband with an output power of 200watts using horizontal polarisation. Thetransmitter radiates three, sometimesfour modulations, two of which providenavigational guidance, the third identi-fies the beacon in international Morsecode and a fourth is sometimes providedto give operational information regar-ding the airport with which the beacon isassociated.

The navigational information com-prises two 30Hz modulations whosephase difference corresponds to themagnetic bearing of the receiver fromthe VOR beacon. Obviously these mod-ulations (or phases as they are called)cannot be directly impinged on oneanother, for they would then beindistinguishable. Other methods arenecessary and that chosen is for one tobe a direct 30Hz amplitude modulation ofthe carrier (variable phase), whilst the

Fig 2 Conventional VOR (a) Building layout,(b) Schematic

tone

rt

9960 Ha borntone wheel

keyed identity tone

speech Id required'

Fig 1 The disadvantage of using an NDB for airway delineation

VHFTRANSMITTER

slots

horizontal rotatingdipole

plinth including drivemotor and tonewheel assembly

counterpoise

equipment room

to senorsrelerence variable

ODULATIONELIMINATOR

28 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

BY BMAsecond is a 30Hz frequency modulationon a 9960Hz amplitude modulated sub -carrier. The total modulation depthcontributed by the two phase modula-tions amounts to less than 100%, thusleaving adequate modulation depthavailable for identification signals, etc.

There are two means of generating thismodulation pattern. These are known asthe Conventional (CVOR) and Doppler(DVOR) systems. Each has advantages.the former being cheaper and moreconvenient to install whilst the latter ismore accurate and is less susceptible tositing difficulties.

CVORAlthough the most modern equipment

uses all -electronic methods of generat-ing the aerial radiation pattern, todescribe this would take far more spacethan is available in this article. I willtherefore describe one of the earliersystems which, nevertheless, stillremains in service in many countries ofthe world.

The heart of almost every radionavigational system is the aerial systemand in the case of CVOR the horizontalpolar diagram radiated is a limacon, asomewhat heart -shaped pattern which, ifrotated, causes the signal strength at aremote receiver to vary sinusoidally at afrequency equal to the rate of aerialrotation.

This pattern is achieved by radiating anunmodulated signal from a horizontaldipole which is fitted to a shaft androtated at 1,800 rpm (ie, 30Hz). In spacethis combines with the omnidirectional

radiation of the reference phase signalto produce the required rotating limaconradiation pattern.

The reference phase modulation mustbe locked to the variable, and this isachieved by fitting a metal tone wheel tothe shaft supporting the variable phaseaerial. The tone wheel has 332 teetharound its periphery. Mounted closely tothese teeth is an electromagnetic pick-up which will give an electrical outputeach time a tooth passes by its head. Ifthe wheel is rotated at 1.800 rpm, theoutput will be 9960Hz, ie, the referencesub -carrier frequency. The teeth,however, are arranged in a somewhatstaggered manner and the irregularityimparts a cyclic variation of between9480Hz and 10440Hz on the outputfrequency, this being dependent on theinstantaneous position of the toothedwheel.

The output from the pick-up is thencoupled to the input of the amplitudemodulation circuits and the RF from thetransmitter is radiated omnidirec-tionally.

A simple variation from this techniqueis that the metal tone wheel is replacedby a transparent disc on which bands areprinted to correspond with the metalteeth they replace. The 9960Hz signal isthen picked off with an optical pick-up

This IAL equipment is typical of the moderngeneration of fully solid-state, non -directionalbeacon transmitters. The output power is up to100 watts, which is continually monitored withchangeover to standby equipment automa-tically initialled should the output power varyfrom the preset level (photo: IAL)

before being fed to the modulator.To ensure that the correct RF phase

relationship between reference andvariable phase signals is maintained, the

received frequencyless than f.

rotating aerial

central fixed aerial transmitting on fc

aerial transmitting onIfc + f,)

aerial transmittingon Ifc - f51

Fig 4 Principle of double sideband Doppler VOR. The central aerial radiates thecarrier frequency, fc, one of the rotating aerials radiates fc + k and the other k - k,where f5 is the frequency of the sub -carrier

transmitting frequency f.

received frequencyhigher than f.

VOR R,gnsl input

RECEIVER

113 Ile FAH:

Fig 3 Effect of rotating the transmitting aerial in a circle.Frequency f will only be received at either receiving site when thetransmitting aerial is either at point of nearest approach to. orfarthest from, the receiving site

AM

DETECTOR

autho output

9960 Hz

FILTER

Fig 5 Airborne VOR receiver

30 Hz

FILTER

LIMITER

PHASE

OFAPARTOR

FREOUENCr

DISCR lAiNATOR

30 Hz

FILTER

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 29

LIGHTHOUSES OF THE AIR

Ground

aerial

RECEIVER TRANS-MITTER

50usDELAY

Aircraft

/ blade aerial

RECEIVERTRANS-MITTER

RANGINGCIRCUIT

Fig 6 Principle of DME

aircraft skin

distancereadout

unmodulated variable phase is derivedfrom the reference phase signal byfeeding a proportion of the transmitteroutput through a limiting stage (often aClass 'C' amplifier) to strip the modula-tion before feeding to the rotatingdipole.

Allowance is also made in the modula-tor design to receive a keyed audio tone(for identification) or speech, which maytypically take the form of air trafficcontrol information such as aerodromeunserviceabilities, altimeter pressuresettings, etc.

DVORAlthough the radiation pattern of a

Doppler VOR is identical to that ofConventional VOR the means of

A Doppler VOR installation photo. Raca

generating it are quite different.In the DVOR, the well-known Doppler

principle, in which the frequency of anapproaching source of radiation isincreased and, conversely, that of areceding source is decreased, is used togenerate the frequency modulation ofthe reference phase signal. The variablephase signal is radiated from a central,omnidirectional aerial as carrier, ampli-tude modulated at 30Hz.

To understand the generation ofreference phase frequency modulation,first consider the effect of fitting anaerial to one end of a horizontal shaftwhich is pivoted at the other. If the shaftis rotated rapidly around the pivot andthen to a receiver located at a distantpoint, as the aerial approaches, the

frequency will increase, and as itrecedes it will decrease. Due to thecircular motion of the aerial, thereceived frequency variation will besinusoidal with the deviation beingproportioned to the diameter of thecircle being described by the aerial.

It can be proved mathematically that ifthe length of the shaft is 22ft, and therotational speed is 1,000 rpm, then thefrequency variation due to the Dopplereffect will be ±480Hz, ie that specifiedfor VOR.

If, therefore, the rotating aerial isenergised from a transmitter whosefrequency is 9960Hz displaced from thatradiating the 'variable phase' signal,then a standard VOR radiation patternwill be produced.

Obviously, rotating a 22ft arm at 30revolutions per second is mechanicallyimpracticable. However, the same effectmay be achieved electronically byinstalling a ring of aerials of theappropriate diameter and switching thesignal from one aerial to the next bymeans of solid-state switching circuits.

However, as the reference and vari-able phase signals have effectivelyexchanged places - ie instead of thereference phase being fixed and thevariable phase rotating, the variablephase now is fixed and the referencephase is rotating - in order to maintainthe correct relationships the rotation ofthe reference phase pattern must be inthe opposite direction to that used inCVOR.

The similarity to CVOR may beimproved by adding a second transmis-sion displaced 9960Hz on the oppositeside of the variable phase signal andfeeding this to the diametrically oppo-site aerial of the array.

The airborne receiverThe airborne receiver consists of a

standard multichannel equipment inwhich the signal is split three ways aftersignal detection.

The first is connected to the aircraftintercommunications system to enablethe aircrew to identify the facility beingreceived and the second and third arefiltered to separate the variable andreference phase signals. The latter isthen applied to a discriminator torecover the 30Hz modulation.

The phase difference of the two 30Hzmodulations is measured, the resultbeing applied to either the flight directoror an electro-mechanical indicator, asappropriate.

Distance measuring equipmentAlthough the navigational information

radiated by a VOR beacon enables thepilot to determine his bearing from thatfacility with a high degree of accuracy,he is still ignorant of his actual positionfor he does not know his distance fromthe beacon. This information is providedby distance measuring equipment.

DME operates between 960 and

30 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

LIGHTHOUSES OF THE AIR1215MHz, with the aircraft interrogatingthe ground beacon on one of the 126channels between 1025 and 1150MHz andthe beacon replying 63MHz either aboveor below that of interrogation. Whenworking in conjunction with VOR, byinternational agreement, the frequen-cies are paired in a predeterminedmanner. Likewise, DME may be pairedwith instrumental landing systems togive distance -to -run on the finalapproach path.

The principle of DME is that the aircraftinterrogates the beacon by radiating apair of pulses, each 3.5 microsecondswide, spaced by either 12 or 36 mic-roseconds at a repetition rate of about150Hz. On receiving a valid interrogation,the transponder delays by 50 mic-roseconds and then replies with a pulse -pair spaced 12 or 30 microseconds. Theairborne equipment receives this reply,measuring the elapsed time between theinitiation of interrogation and receipt ofreply, deducts 50 microseconds anddisplays the remainder as a distancepresentation in nautical miles.

With such a relatively simple system itwould appear that two main problemswould arise if more than one aircraft wasinterrogating the beacon at the sametime:1. How does the aircraft identify its ownreply?2. What happens when too many aircraftinterrogate the beacon?

The first of these is achieved in a quitesimple manner, for the interrogatorcircuitry is arranged to make the pulserepetition frequency somewhat unstableand the receiving equipment is designedso that it will only respond to replies withexactly the transmitted PRF.

The second problem is tackled in twoways. The beacon is only capable oftransmitting 3.000 pulse -pairs persecond. If the interrogations do notreach this figure, random pairs areradiated to maintain a constant duty -cycle for the transmitter.

The initial aircraft interrogation is atabout 150 pulse -pairs per minute (knownas search mode). However, once com-munication is established, the airborneequipment automatically reduces theinterrogation rate to about 25 pulse -pairsper second (tracking mode), thus enab-ling more aircraft access to the beacon.

Should the number of interrogations ofthe beacon approach 3,000 pulse -pairsper minute, then the sensitivity of thebeacon receiver will be automaticallyreduced, thus removing service from themost distant aircraft. An extreme case ofthis would occur if the beacon were tofail for a brief period whilst beinginterrogated by 100 aircraft.

Under such circumstances all theaircraft would revert to search mode andon restoration to service the beaconwould be faced with 15,000 pulse -pairinterrogations per second.

The beacon receiver gain would thenautomatically reduce until only 3,000

to aerial

POWERAMPLIFIER1025-1150

KAHr

PULSE

MODULATOR

FREQUENCYMULTIPLIER

RANGINGCIRCUIT

to Tacan beabng cacoa

RANGEDISPLAY

PRE

SELECTOR

CRYSTALOSCILLATOR

126FREQUENCIES

FREQUENCYCHANGER

IF AMPLIFIERAND

DECODER

Fig 7 DME airborne receiver block schematic

beacon identity code

interrogations were being received, ie,the nearest 20 aircraft. As each of theseaircraft regained communication withthe beacon and reverted to track mode,so the number of interrogations wouldreduce, thus allowing the beaconreceiver to increase in sensitivity andaccept more distant aircraft. Gradually,after a few minutes, all aircraft wouldhave reverted to track mode and the totalwould be less than 3,000 interrogationsper second.

An interesting alternative to DME is asystem which was developed in Australiafrom wartime Rebecca/Eureka beaconsand operates on approximately 200MHz.This, however, has only ever been usedin Australia and the South Pacific areaand is now coming to the end of itsoperational life.

The combined VOR/DME system pro-vides a course accuracy in the order oftwo degrees and a range accuracy of 0.1mile up to 200 miles range.

First Airbus 84 for Korean Airlines

Over the thirty -odd years during whichVOR/DME has been the standardaeronautical short range radio aidthroughout the world, it has proved to beaccurate, reliable and popular with theaircrew which it serves.

As such there are, at present, no plansfor its replacement in the foreseeablefuture.

When in the fullness of time replace-ment eventually becomes necessary, it ispossible that this will be by a space -based system such as a development ofNaystar which will be described in anarticle later in this series.

In my next article I shall be dealing withthe approach and landing systems:instrument landing systems (ILS) andmicrowave landing systems (MLS),which allow suitably equipped aircraft tomake a safe landing in visibility condit-ions in which most of us would thinktwice before venturing forth on a pedalcycle. -I

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 31

DATA FILE . . .Ray Marston presents a final selection

of LM10 application circuitsRtrnc

Balance5

2

Output 1..db.ck6

V+

Input R eeeeee coutput

4

Fig 1 Functional diagram of the LM10

R1

M,c36 to 12k

+5V

Fig 2 Remote 20dB voltage amplifier for use with inductive or magnetic input device

R1

M,c3R to 12k

Fig 3 Remote 40dB voltage amplifier for use with inductive or magnetic input device

X Itssnoutdvic

oV

R31k2

Out10 es.,2V21

V

Fig 4 Remote 20dB voltage amplifier for use with a high impedance (crystal) input device

In the last three editions of Data FileweShave looked at the basic details andpractical applications of the LM10, aunique bipolar linear IC that is producedby the National Semiconductor Corpora-tion. It houses a high performance op -amp plus a precision 200mV band -gapvoltage reference and a 2 -input bufferamplifier in a single 8 -pin TO5 package.To help refresh the reader's memory,Figure 1 shows the functional diagramand pin notations of the LM10.

In this month's edition of 'The File', weconclude the LM10 applications themeby looking at a variety of practical remoteamplifier, 2 -wire transmitter and movingcoil meter amplifier circuits.

Remote amplifier circuitOne of the most interesting aspects of

the LM10 is its suitability for use as ashunt -connected, 2 -wire, remote ampli-fier unit. The op -amp section of the IChas an output current drive capacity thatis a couple of orders of magnitudegreater than the device's quiescentcurrent value, and this factor, combinedwith the op -amp's 96dB supply -voltagerejection figure and a wide operatingvoltage range, enables the op -amp to beused as a linear amplifier even when itsoutput terminal is shorted directly to oneof the device's supply terminals. In thiscase the supply leads can be used tocarry both supply and output signalcurrents. Figures 2 to 4 show somepractical examples of circuits of thistype.

In the Figure 2 to 4 circuits the pin 6output and pin 7 supply terminals areshorted together, enabling supply andsignal currents to flow along the samewire via R3. Thus, the circuit to the left ofR3 can be regarded as a signal amplifying'transmitter' that is connected to the R3'receiver' via only two wires (or via asingle wire if a common earth return isused). This 2 wire type of circuit thusoffers a very simple and inexpensive wayof remote monitoring a microphone orvibration sensor, etc.

Note in the above circuits that pins 1and 8 are shorted together so that a200mV reference voltage is developedon pin 1, and this voltage is thenceapplied to the pin 3 non -inverting inputterminal of the IC.

Each circuit is given a dc voltage gainof x 11 via the R1 and R2 values and thusgenerates a quiescent output voltage of2.2 volts, but this voltage can bemodulated by the op -amp's output signalvoltages.

The Figure 2and 3 circuits are suitablefor use with low to medium impedanceinput transducers such as moving coil ormagnetic microphones, etc, and theFigure 4 circuit is suitable for use withhigh impedance devices such as crystalor ceramic microphones, etc. The Figure2 and 4 designs each give an ac signal

32 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

voltage gain of about 20dB, and theFigure 3 design gives a gain of 40dB.

Figure 5 shows a simple circuitmodification that enables the basicdesign to be used with any resistivetranducers wired into the Rx position.Here, the op -amp signal gain is set atx7.6 via R1 and R2, but the pin 3 inputvoltage is variable from 200mV upwardsvia Rx, thus giving the output voltagesshown in the diagram.

Fault IndicatorsThe shunt -connected 2 wire amplifier

technique can easily be modified to formthe basis of a variety of 2 level 'fault'indicator transmitters with either resis-tor, LED or transistor outputs at their'receiver' ends, as shown in Figures6 to 9.

In each of these circuits the LM10 iswired as a precision voltage comparatorwith a fixed reference voltage applied toone input terminal and a variable inputapplied to the other, with its outputgrounded via R3 and its supply currentpassing through R4. The basic circuitaction is such that when the op -ampoutput (pin 6) is low (giving zero driveinto R3), only 200mV is lost across R4, butwhen the output is high (giving a highdrive current into R3), about 3.5 volts arelost though R4.

In practice, the circuit output canfrom the pin 7

supply terminal of the IC, or via an LED ora transistor that is wired across R4, asshown dotted in the diagram. In theformer case, the LED ON current isdetermined by the R3 value: in the latterthe final output can be taken from acrossTr1 collector load resistor R5 andswitches between an OFF value of zerovolts and an ON value of 4.8 volts.

In each of the Figure 6to 9circuits pins1 and 8 are shorted together to generatea 200mV reference voltage that is appliedto one of the input pins of the op -amp. InFigure 6 an external test voltage is fed tothe pin 3 non -inverting input terminal ofthe op -amp via potential divider R1 -R2,and the circuit action is such that pin 7output switches low (to 1.5 volts) whenthe pin 3 voltage exceeds 200mV: this

It, 200n.V51

52

N1

100k

112

15k

+5 V

N31k2

V out=1V5 when R:=0

= 3V when R.. 114

Fig 5 A 2 -wire transmitter for use with a variable resistance sensor

v,.= zoom. (121.A

'Si

I ,. _.114I- -----4-r. IT"

....1.

i Itree. o

wowOf 040E.11..V eft al OR a 101 5...> 01. ev

120Orn1f e Coe / ISOM11,11 a.' On 0.11 IE110011 for tLED ttttt 1

e

V

Fig 0 2 -wire precision over -voltage transmitter with resistor, LED ortransistor output

V in

200mV to 00

LED'r -14--7

04

11 outOf I 41,111

On= 101

113

3401111005 forLED output 1

200mV 52

51

52105

LED1r - -

I 04 I

V Out01f4V5On = /V5

53540010011 for

LED output I

ar770V

Rs j

5V

VentOtt OVOn = 4V4

Fig 72 -wire precision under -voltage transmitter with resistor, LED ortransistor output

V

11 V out

115Of, 00

lY5 c On 0 4011

20001,111

L11 0C

LE01

1

1 1141

WoolOff 4115On 0101

53560511005 for

LEOoutput)

avOV

Fig 8 2 -wire precision over -current transmitter with resistor, LED or Fig 82 -wire precision under -current transmitter with resistor, LED ortransistor output transistor output

I 152

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 33

DATA FILEcircuit thus acts as an over -voltagedetector. The Figure 7 circuit gives thereverse of this action, with its pin 7output going low when the pin 3 inputvoltage falls below 200mV, and thus actsas an under -voltage detector.

The Figure 8 circuit is similar to that ofFigure 6 except that the pin 3 inputvoltage is taken from across R1 and isdirectly proportional to the R1 inputPcurrent; this circuit thus acts as anover -current detector. The Figure 9circuit is similar, but has its inputterminals reversed and thus acts as anunder -current detector.

Finally, Figure 10 shows how this typeof circuit can be modified to act as a lightor temperature sensitive detector byusing a cadmium -sulphide photocell or anegative temperature coefficient ther-mistor in the R1 position. In this case R1-RV1-R2 and R3 are wired in the form of aWheatstone bridge that has its outputsfed to the pin 2 and pin 3 inputs of the op -amp, and the bridge is powered from a400mV supply that is set up via R4 and R5.

In Figure 10, the LDR or thermistorshould have a resistance in the range 500ohms to 9K0 at the desired trigger level.If the LDR or thermistor is wired in theposition shown in the diagram, thecircuit will act as either a 'dark' or 'under -temperature' detector, its output switch-ing on when either the light level or thetemperature falls below a value presetvia RV1. Alternatively, the circuit can bemade to act as either a 'light' or 'over -temperature' detector (in which theoutput switches on when the light ortemperature level rises above a presetvalue) by simply transposing the posi-tions of R1 and RV1.

Fault alarmsThe Figure 6 to 10 fault -detecting

circuits give a simple ON or OFF form ofoutput and can thus fairly be describedas simple 'fault indicator' circuits. Bycontrast, Figures 11 to 14 show aselection of fault detectors that giveeither a flashing LED or a 400Hz audible

monotone alarm signal output and canthus be fairly described as 'fault alarm'circuits. These alarms are, in fact, verysimilar to the four gated fault indicatorcircuits described in Figures 12 to 15 oflast month's edition of Data File, exceptthat they are connected in the 2 wire'shunt' mode and can thus give remoteindication of the fault condition.

In each of the Figure 11 to 14 circuitsthe op -amp section of the LM10 is wiredas an astable multivibrator or square

wave generator that is gated (via D1) viathe output of the internal referenceamplifier, which is wired as a voltagecomparator with one input taken fromthe 200mV band -gap reference and theother taken from an external source viapin 8. The Figure 11 and 12 circuits arewired as under -voltage and over -voltagealarms respectively, and Figures 13 and14 are wired as under -current and over -current alarms respectively.

Note in the Figure 11 to 14 circuits that

For LED output. Cl; 720n 67-.1MFor eeeeeee output.C1'10n.117 6116V.. 200otV(R5 "

RI101.

62106

Fig 12 2 -wire precision over -voltage transmitter withflashing LED or monotone audio (400Hz) output

RI10k

62106

RI Cdmouto-ulphrel pkorocIl orthroirstor. orroth SOON to 9knI

eeeeee t tr.goor te.toiLEO 1

r - 1

V outOf 41116

N On 11/5no.11006 tor

LEO

Ov

Fig 10 2-w re precision 'dark' or 'under -temperature'transmitter with resistor, LED or transistor output

162

163 S

01101/Con e VII

61

10k

112

10k

111)

SVLED,

RS SPKR I

1006 I

361.256

For LEO output C1:220n;R7:11AFor eeeeee r output: C1,10n;R7:61111

1001, v,,,9' 200...V66 1

0vFig 11 2 -wire precision under -voltage transmitter withflashing LED or monotone audio (400Hz) output

S V

For LEO output. C1.2209.117.1111For aaaaaaa output Cl'100.67119k

4 vv

Fig 13 2 -wire precision under -current transmitter withflashing LED or monotone audio (400Hz) output

34 please mention RADIO 8 ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

DATA FILE

112'Si

+BY

SP55L35 too 25W

F., LID 5 33... 57 INFr eeeeeee CI 105.47 NY

I, y Oar10100.

Fig 142 -wire precision over -current transmitterwith flashing LED or monotone audio (400Hz)output

the astable timing is controlled by the C1and R7 values. If a circuit is to be used togive a flashing LED output, thesecomponents should be given values of220n and 'IMO respectively, to give a flashrate of 100 flashes per minute. If a circuitis to be used to give a 400Hz audiblealarm tone output, the componentsshould be given values of 10n and 68Krespectively.

Meter amplifier circuitsTo conclude this look at applications of

the LM10, Figures 15to 18 show a varietyof ways of using the device as a very lowvoltage amplifier that can be used togreatly increase the effective sensitivityof a normal moving coil meter ormultimeter.

In the Figure 15 circuit the op -amp isused as a simple non -inverting amplifierand increases the effective sensitivity ofa 1mA meter by a factor of about 100, to10/2A fsd. Note that this circuit has no 'setnull' facility, and can give no indication ofreverse -connected signals. The mod-ified circuit of Figure 16 does not sufferfrom this defect.

The Figure 16 circuit uses a 100/AAmeter and increases its effectivesensitivity by a factor of 100 to 1p.A fsd.Note in this case that the 200mVreference voltage of pin 1 is used tocreate a 'common' input and outputsignal line that is 200mV above the 'zerovolts' value, thus enabling the op -ampoutput to swing between +1.3 volts and-0.2 volts, therefore enabling the meterto indicate both forward and reversevoltage values. RV1 provides the circuitwith a 'null' facility, enabling the outputto be set to give a meter reading of zerowith zero input signal applied.

Finally, to complete this LM10 mini-series, Figures 17 and 18 show how thebasic Figure /6 circuit can be adapted foruse as a 4 -range dc millivoltmeter and a4 -range dc microammeter respectively.Note that each of these op -amp drivenmeter amplifier circuits is powered froma single 11/2 volt battery supply!

100mV10uA

10k

Fig 15 Simple meter amplifier giving asensitivity of 100K/volt to a 1 mA fsd meter

1/6

100..V1uA

Fig 18 Precision meter amplifier, with nullfacility, giving a sensitivity of 1MO/volt to a1001.1A meter

111

SW'

1.1516C

66

151

NVIn

S.

AtteNiest fad

57Gig

Fig 17 A 4 -range dc millivoltmeter, with asensitivity of 1MO/volt

15A

15p1.,

as

IVO562

is.est 1mi

Fig 18 A 4 -range dc microammeter, with a fullscale sensitivity of 10mV

166

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 35

SOLDERING:Art or Science?

Some tips on a subject of relevanceto all home constructors

by P J Cooper G3CXIWe all speak glibly of soldering aconnection, but do we know what is

involved in making a sound joint?Due to the prohibitive costs of amateur

equipment, home construction is be-coming increasingly popular, and this inmy opinion is a good thing; in buildingsomething yourself you get a better ideaof how and why it works - but back to thesoldered joint.

In the initial stages, thought must begiven to the compatibility of the basemetals to be soldered.

Soldering can be affected by storagetimes, and it is a good idea to check thesolderability before assembling. Somecomponents may be tarnished andrequire tinning before assembly. Mostsmall components will have a protectiveflux in the wire ends. But don't takechances; in most cases a wipe with thesnipe -nose pliers will suffice. Rememberthat many dry joints start life because ofthis problem.

Fluxes and fluxingFlux is used primarily to prevent

oxidisation of the metallic interfaces ofthe joint and should have these charac-teristics:1) It should be a liquid cover over thematerial and exclude air from the joint.2) It should continue to do this right up tosoldering temperatures.3) It should dissolve any oxides on themetal surface or on the solder and carrythese unwanted materials away.4) It should be displaced from the metalby the liquid solder.

A mineral oil or jelly would satisfy thefirst two requirements, but not thesecond two. With regard to number 3,metal oxides dissolve in molten alkalis athigh temperatures inconvenient to softsolders, but they also dissolve in acids attemperatures below the melting point ofsolders. Soldering fluxes are thereforeacids or substances that yield acidswhen heated.

Hydrochloric acid in water is a goodflux for soldering zinc. Lactic acid,phosphoric acid and oleic acids are usedcommercially for soldering fluxes. Resinyields an acid (abeitic) when heated tosoldering temperatures.

The halide group of fluxes - fluorine,bromine, iodine and chlorine - whichform hydro -acids to become fluorides,

bromides, etc are very strong and quickacting, but they absorb water readily andthen rapidly start corrosion, especiallynear the actual joint where sputtering ofthe flux has taken place. For this reason,exercise extreme care when using thesefluxes. They are banned for use onelectronic equipment but are still avail-able, so take care.

Let us look at what happens chemicallywhen a copper clad board is solderedusing a tin -lead solder and zinc -chlorideflux.1) ZnCl2 +H20 = Zn (OH)CI + HCI

The acid attacks the oxide on thecopper.2) 2HCI+ CuO = CuCl2 + H2O

The copper chloride dissolves as soonas it forms in the zinc chloride solution,the bulk of which is still unchanged. Atthe same time, tin in the solder isdissolved by some of the hydrochloricacid.3) Sn + 2HCI = SnCl2 + H2

The tin chloride also becomes dis-

solved in the zinc chloride solution. Theclear copper surface underlying the zincchloride flux now reacts with the tinchloride forming copper chloride andliberating metallic tin which deposits onthe surface of the copper.4) Cu+SnCl2 = Sn+CuCl2

The deposited layer of tin now dis-places the zinc chloride from the surfaceof the copper up to the edge of themolten solder. In the molten solder thereis tin which instantly merges with thedeposit of tin, and the edge of the moltensolder therefore advances rapidly overthe surface, pushing the flux ahead of it.

Although the zinc chloride contentmay be quite low, a strong possibility ofcorrosion exists and so another activatormust be used instead of this for the sakeof future circuit safety.

Activated flux use in electronicsResin, rosin, or colophony, call it what

you will, is the gum exuded from the pinetree. It reacts mildly at temperatures,

Examples of soldering irons currently on the market

36 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

yielding abeitic acid, and this is what wenormally use for electronic circuits.

By itself it may not be strong enoughfor some stubborn oxides, so an additiveis used. This is usually one of the aminesgroup of hydrachlorides: hydrazine, ani-line hydrachloride and glutamic acidhydrachloride (GAH). The latter isnormally used and is limited to 0.7% ofthe volume. Any higher activation couldgive rise to corrosion again. There is nosuch thing as non -corrosive flux -whatever the adverts say.

Making the jointMaking the joint requires a little

intelligent thought - in other words, usean iron that is adequate for the job. Mosthobbyists will have various sizes of iron,to cater for large or small work surfaces.Generally, you must choose an iron andbit size best for the job in hand.

The temperature of the iron mustremain reasonably hot in contact withthe mass to be soldered. Apply the soldernot to the iron, but to the joint. When thejoint temperature is high enough thesolder will flow round the joint to the ironand both iron and solder can then beremoved together. Never, ever applysolder to the iron and then the loadediron to the joint, because that wisp of

smoke you will see is all your flux burningaway, never seeing the joint it isintended to work on. That is the way dryjoints lie.

Cooling the jointCooling the joint is simply a matter of

removing the iron. Do not blow on thejoint or subject it to any forced cooling.The joint cools from the liquid statethrough the plastic state to the solidstate in a fairly short time. The criticalperiod is between 183 C and 140-C, and itis within this temperature range thatthings can go wrong if the joint isdisturbed.

Cleaning the assemblyAfter your soldering work is finished it

is time for inspection. If you have done agood job much cleaning will not benecessary, but if it needs it then don't usea flux solvent: this will only brush fluxresidue all over the assembly withpossible faults due to tracking later. Usea stiff brush and that should be adequate.

Storage of part built assembliesIf you do not complete your assembly

in one go, lightly solder the connectionsyou have made - otherwise the inter-faces will oxidise and you have the

makings of a first-class dry joint later.When choosing which solder to use on

your work you may not have a lot ofchoice. Try running the solder wirethrough your finger and thumb, thenhave a look at it. Is it lumpy? If so it is poorquality material. The flux is put into thewire solder in the correct volume per unitmeasure. If it appears lumpy then thereare voids in the flux distribution through-out the solder, and this will createsputter.

Another cause of sputter is an iron thatis too hot. 370-C is the ideal for normaloperations. This allows the mass to bebrought quickly to soldering tempera-ture (183C) and allowance for thecooling of the iron by the mass to besoldered.

ConclusionThis short article has only scratched

the surface of soldering methods and theassociated problems.

The soldered joint is probably one ofthe major means of connection in theelectronics world, but is usually dismis-sed as merely a means of joining A to B. Aphysicist once remarked to me that ifthere was a better way of connecting twoobjects together in an electrical circuit,no one had told him about it.

ECW FoR KITSK2622 - AM/FM Antenna Amp. 22dB gain from 10MHz £12.13 >to 150MHz from this kit. Complete with metal case

)er kit12- 15V d c. supply voltage direct or via coaxial input.50- 75ohm impedance lines

DK2554 - Quality FM Tuner. Varicap tuning from £32.0285 108MHz. 1.2uV sensitivity, 70dB S/N ratio. AFC,AGC and output for digital frequency display. per kit

>K2553 - Stereo Decoder. Works with K2554 tuner kit, £1 799includes stereo indicator signal, stereo on/off and19kHz filter. Excellent stereo radio reproduction. per kit

K1771 - Short Range Transmitter. Miniature FMtransmitter for short distance communications. Inputsfrom all mics., pre --amps, etc. 1Megohm inputimpedance, 5mV sensitivity. 100- 1G8MHz adjustableoutput frequency. 9 12V d.c. supply.

£9.20per kit

K610 - LED VU Metier. VU level display using a 12 LED C15.47bar graph. Adjustable input sensitivity for all types ofsignals. per kit

> K1798 - 16 LED Stereo VU Meter. Stereo VU display, £26.75twin 16 LED high resolution bar -graph output.Internal adjustable pre -amp to give sensitivity from per kittoomv to 10y full scale

K2032 - 3 digit DPM. Three digit digital panel metermodule, -999 to -- 99mV full scale, zero adjust,overload indication. 1mV resolution and 0.1% linearity20uV/ C temperature stability. Compact unit 9asilybuilt in to other equipment.

K1803 - Universal Preamplifier. For signal matching,low level input boosting, etc. 40dB gain, adjustableoutput. 20Hz 20kHz bandwidth. 40mV full scale input

K2576 - 40W Power Audio Amplifier. No adjustmentsnecessary and non -critical power supply from 2x6 to2x18V unstabiltsed. 250mV input sensitivity10Hz- 50kHz bandwidth. I+ / -3c113). Protected againstshort circuit and thermal overload

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 37

The FIFJ-1274 MC 2Packet Radio

There is good news indeed for those ofyou who have become interested in

Packet Radio. Because of a growingmovement towards it, prices have fallento such an extent that, whereas one oncehad to budget for £600 plus as the cost ofa top of the line unit or slightly less forone in kit form which had to be importedfrom the USA, it is now possible to buy aready built packet radio transceiver forsignificantly less than one would pay fora typical 2 metre FM mobile transceiver.The MFJ-1274 is such a unit and,interestingly, was made in Hong Kong. Itis available in this country from Amdat.

The MFJ-1274 is a TAPR (TucsonAmateur Packet Radio) TNC 2 clone, andall the circuitry is contained on one PCB.Twenty-four integrated circuits are usedin the unit, four of which operate thetuning bar. The bar consists of 20 redLEDs placed vertically and I found it agreat help when attempting to tune in asignal on the HF bands. The tuning unitcan be purchased separately from Amdatand is suitable for connection to any TNC2 clone.

The MFJ-1274 is quite a small piece ofequipment, measuring only 192mm (7.5inches) wide by 39mm (1.5 inches) high by242mm (8.5 inches) deep. There is a 2mmoverhang all round the front panel whichreduces the actual measurements of thecase by 4mm in respect of width andheight. The case is made of aluminium,the body being painted matt black andthe front panel matt silver, a pleasingcombination.

The front panel carries five LEDindicators: DCD (data carrier detect),PTT (transmit line state), STA (unack-nowledged packets), CON (connect sta-tus) and PWR, the rear panel having allthe necessary sockets and switches forthe operation of the unit. The micro-processor is a CMOS Z80 running at2.5MHz, and all the serial in/out data ishandled by a Z80 S10.

An additional facility in the MFJ-1274was the ability to accept input/output

TTL voltages from computers such as theCommodore 64 and the VIC-20. The MFJ-1274 will, in fact, operate from anycomputer having an RS -232 port. Thepower required is 12 volts dc at400/500mA.

As with other packet radio transceiv-ers, there is a fair amount of setting up todo before any actual operation can takeplace. The interconnecting leads have tobe made up between the BBC computerwhich I was using and the MFJ-1274, butsince 'xon/xoff' handshaking is used onlythree wires are required, transmit data,receive data and signal ground. Thetransmit tones and the PTT line are takendirectly to the rig.

I was using two rigs, one for HF and theother for 2 metres, but found no means ofconnecting both rigs at the same time.This proved to be most inconvenient and,since the connections for the rig used for2 metres and the main HF rig weredifferent, I had to make up a smalladaptor lead, one end being female andthe other end male.

The software used for this review wasan EPROM supplied by Amdat which wasinserted in a vacant socket in the Beeb. Ityped '*TNC' to call up the program, andthe display was in the form of a splitscreen similar to a number of otherdisplays used for RTTY and AMTOR. Theprogram used the function keys of theBBC to activate different commands, andthere were 25 alternatives which couldbe brought into action via the functionkey, some in conjunction with the shiftkey or control key.

Before any information could beshown on the screen, the baud rates hadto be set via an eight -way DI L switch onthe rear panel. This controlled both thecomputer and the radio in/out rates. Thefirst five switches from the left applied tothe computer side and the remainingthree to the radio. The baud rates for thecomputer in/out were 300,1200, 2400, 4800and 9600 and the rates for the radio sidewere 300, 1200 and 9600. The 9600 baud

tied 4-IAFJ TNC 2 PACKET RADIO

MODEL MFJ 1274

OCI> PIT STA CON PWR

rate was not usable with the internalmodem but was included for use with anexternal high performance modem.

Personally, I found this operation veryfiddly. It had to be done using a smallscrewdriver, and movement of theswitches themselves was very stiff.Admittedly, the baud rate for the compu-ter only had to be set once (in my case,for the Beeb, it was 1200 bauds), but thesetting of the different baud rates forVHF and HF working I considered to bevery awkward. When changing from VHFto HF one had to remember to press aswitch to change the tones and band-width and also to move the audioinput/output lead from one rig to theother. In my view, an altogether inconve-nient operation.

Once everything was set up andswitched on the sign -on messageappeared. A lithium back-up battery wasincorporated in the circuitry: this has alife of about five years and will retain allthe personalised details entered into theRAM. The first thing I did was insert mycallsign and the date/time.

There are more than 80 user configur-able parameters and a number ofimmediate commands available, but inthe main the default values are accept-able. Any different values would have tobe set by the operator. Options areprovided in the commands for monitor-ing other traffic on the frequency, whichproved very interesting, but for the initialstart of a contact it was only necessary totype CONNECT (or 'C') G3XYZ RETURNand the unit promptly went into thetransmit mode and sent the packet. Itwould attempt to make a connection bysending the packet the default numberof times (default for RETRY was 10), andthen if no connection resulted themessage '*** DISCONNECTED RetryCount Exceeded' would appear.

At the second attempt contact wasmade with GB3UP, the mailbox at theUniversity of Surrey. This time thecontact was satisfactorily completed,although the amount of activity on144.650MHz in the London area wasphenomenal, resulting in extra attemptsbetween GB3UP and my QTH.

The unit also was able to 'digipeat', afacility which I was not able to takeadvantage of because my CITH is not in avery good position for VHF. Two types ofconnection are available. The first, andthe one I used to contact GB3UP, isknown as the 'CONVERSE' mode, and israther like RTTY, where, hopefully, onecan have a real-time QS0. I must admitthat here in London it was very frustrat-ing to try and do that because of the highoccupancy of the frequency. Doubtless,

38 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

elsewhere in the country it wouldn't beso difficult.

The other mode is called 'transparent'and is just that. It transmits all characterswithout modification, but can only haveone connection at a time and would beused for the transmission of files, etc.The CONVERSE mode can support up to10 different connections at the sametime, with all incoming packets displayedshowing the sender. There is also a'BEACON' command, which sends out apre -prepared message at given inter-vals. In my opinion, the use of beaconshere in London is not a good thing: as anexample of usage, I printed out aconnection to GB3HQ (RSGB Headquar-ters station), which took place at 0325UTC (!), which shows that even at thattime of day packet is being used.

The HF operation was not so easilyachieved. As I mentioned above, it wasnecessary to unplug the lead, connect itto the other rig and manipulate theswitches before any operation couldtake place. However, this was done and

by Ken Michaelson G3RDGon a frequency of approximately14.101MHz (this being one of the agreedfrequencies for packet radio) I hadseveral good QSOs, also gaining accessto two mailboxes, LA3T-1 in Tromsoe andEA4PE in Madrid.

The tuning bar came into its ownduring HF operation; without it, tuning ina transmission would have been difficult.One moved the transceiver tuning con-trol until the illumination was centralisedwith the two end LEDs more brightly lit.Curiously enough, the TNC-220, which Ibuilt from a kit and reviewed for anothermagazine, had two radio ports, soconnections to the two rigs could beinstalled permanently, the change fromone to the other being carried out bycommands to the unit. This was muchsuperior.

It is unfortunate that the front panelhas been cut out with some form ofguillotine, thus giving it a sharp edge allthe way round. I feel that it would nothave been too much of an effort tosmooth the edges down. However, this is

a minor point. The MFJ-1274 performedperfectly during the period of the review,and a bouquet must be given to theauthor(s) of the Owner's Manual, whichcontained 157 pages of information, a 17 -page index in alphabetical order and 4pages of circuitry. The cost of the MFJ-1274 ready built and cased, completewith an ac adaptor giving the requiredcurrent at 12 volts dc, is £189.00. At thatprice, you can't go wrong. The AmracEPROM containing the driver program isavailable at £11.50 extra.

For more instruction and informationon the subject of Packet Radio, I wouldrefer you to the ARRL Handbook 1986,sections 19/23 to 19/47, and also to anarticle written by Margaret MorrisonKV7D and Ben Morrison KV7B. Thisarticle, entitled Amateur Packet Radio,was published by Ham Radio Today inJuly and August 1983.

Thanks are due to Martin Stubbs ofAmdat, Crofters, Stoke Road, BristolBS12 6HQ (tel: (0272) 699352/559398) forthe loan of the unit for the review. IRoval

AK D TEL.0438 351710

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 39

What isImage Processing 7

Dr C J D Catto explains how newdevelopments in this field could soon bring

it within the reach of home enthusiasts

Clectronic image processing is not aGtotally new science, but advances insemiconductor technology over the pastfew, years have brought it within thereach of many more users: not justscientists working for well -fundedresearch establishments, but also educ-ationalists and quite soon even home -based enthusiasts.

Manipulation of true grey -scaleimages (as opposed to graphics)requires a huge amount of RAM andprocessing power. The key developmentthat has brought down the size and costof electronic image processing equip-ment is the steady improvement insemiconductor memory, averaging a

doubling in density each year over thepast decade.

HistoryWhereas in 1970 it would have been

necessary to go through time-consum-ing optical and photographic processesif anything more advanced thanrudimentary video processing wasrequired, the ensuing years saw thegradual entry of digital techniques, aswell as the introduction of analogue -to -digital and digital -to -analogue conver-ters. This permitted the construction of'solid-state' TV standards converters (egto 'translate' NTSC to PAL), but in thosedays such equipment filled many racksand was within the budget of the nationalbroadcast authorities only. They werefollowed by what we would understandas the original 'studio effects' machines,again somewhat bulky and not tooversatile.

It was the arrival of the relativelycompact Quantel machine that even-tually achieved the breakthrough, mak-

ing this TV production technology avail-able, and perhaps essential, to all TVstudios. In the not too distant future,even domestic TV sets will include somebasic image processing hardware suchas picture memory, as part of theproposed high definition TV system forexample.

ResearchThere are, of course, many applica-

tions of image processing outside the TVfield. In scientific research, the user ofan optical or electron microscope canbenefit from a system that will improvecontrast, reduce noise, sharpen edges,or even just act as a rapid -accessarchive. For routine image analysis, egthe counting of particles on a micro-scope slide or the measurement of grainboundaries in a specimen of steel,dedicated machines (such as the Cam-bridge Instruments' Quantimet) havebeen in production for more than adecade, but in many ways the moreinteresting field of true processing (asopposed to analysis) has opened up inonly the last few years.

We now stand at the threshold of a newand potentially huge industry. For exam-ple, since the launch of the French'SPOT' satellite, an enormous amount ofhigh resolution remote sensing data iscommercially available at a relatively lowCost: a company prospecting for mine-rals in Africa, say, is wise to commission astudy employing such data beforeembarking on an expedition to drill holesin the ground.

EquipmentThe heart of an image processing and

display system is the framestore, which

can be a basic video memory board withlimited processing, such as the SPC512card made for use with EPIC software bySynoptics of Cambridge. Such cardsplug into the expansion slots of an IBMPC or clone, and need little more thanthe addition of a TV monitor for imagedisplay before quite interesting princi-ples can be studied and experimentedwith.

More powerful systems employ sep-arate framestore and processor boards,joined by high speed data buses, but forflexibility and ease of program controlthey generally require a link to a

computer with keyboard and VDU. The'host' may be as simple as a PC or asserious as a VAX, but the real-timecontent of the image processing mustnecessarily be handled by the 'guest'boards. Current generations of digitalcomputers are adequate for graphics,but rapid manipulation of proper imagesneeds dedicated IP hardware.

Video dataClearly the video path through the IP

boards is a vital consideration whendesigning a system whose object is toimprove picture quality; in contrast withsimple computer graphics circuitry, pic-ture information of at least 8 bitsbrightness resolution must be handled.In a typical system, a TV video signal isconverted to digital form by a 'flash' A/Dconverter, at a sampling rate of 15MHz.

Once in digital form, the data is storedin RAM and is available for digitalprocessing, under hard -wired control, orincreasingly by digital hardware which isunder software control. The data isgenerally passed back to RAM. It can betransferred to hard disc for long term

40 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

storage. In cases where the imageprocessing algorithm is beyond thecapability of the on -board hardware, thepicture data may be sent to the 'host' viaan interface or bus. The nature of thisinterface obviously has considerableinfluence on the speed available, quiteapart from the limitations of the 'host'itself.

Picture outputAssuming the data is back in the video

RAM, in order to display it on a CRT orprojection TV screen a high speed DACis required, and the sync signals may beadded or sent out on a separate cable.One 'wrinkle' that is now often employedis the colour look -up table (GLUT); thiscan be loaded under software control soas to assign colour values to the grey -scale signal, giving a 'pseudo -colour'result. Since the human eye is quitesensitive to colour variations, thismethod allows the perceivable contrastrange of the video signal to be expandedconsiderably, at moderate extra cost. Infact, reasonably high quality colour TVmonitors capable of linear display (suchas the Philips CM8533) are no longerexpensive.

Software developmentSoftware for image processing has

been developed in centres of learningsuch as Cambridge over a couple ofdecades, but it is the advent of lower -cost computers such as the IBM PC andsimilar machines that has widened therange of users and potential converts.

What used to be a subject accessible toonly the most prestigious researchdepartments is now open to anyone whocan afford a personal computer, soft-ware, framestore card and TV monitor.

ProcessesSome of the key mathematical proces-

ses in this subject will be mentionedbelow. The basic arithmetic operationssuch as extracting sub -regions from animage, shrinking or expanding them andso on do not require much in the way ofprocessing, but rotation by an arbitraryangle clearly needs more complexoperations. Work on the grey -levelcontent of an image covers many topics,for example extraction of contrast statis-tics, creation of brightness contourmaps, overlaying of text and graphicsand non-linear or pseudo -colour conver-sion to enhance the contrast range of animage.

ExampleFor comparison of images, simple

subtraction routines can be used, butthey do depend on the original imagesbeing well aligned. This can nowadays beovercome by more advanced software,which can form the 'rubber sheet'corrections. As for statistics, an example

of histogram generation is shown inFigure 1, where a silicon chip is beingexamined in a scanning electron micro-scope.

Filters and transformsRather more interesting operations

provide spatial filtering, for instance tosmooth or to sharpen an image. Animportant point here is that digital imageprocessing is able to provide true two-dimensional filtering, whereas a con-ventional analogue filter operating on,say, a TV signal can offer processing inthe line -scan direction only.

Beyond the basic filtering and con-volution operations, there are moreabstruse transforms such as Fourier,Walsh or Hilbert. These 'classical'methods may be familiar to those whohave studied signal processing for radioand communications. The advantage ofusing these transforms is that by conver-ting an image from the spatial to thefrequency domain, a mask or filterspecially tailored to the task in hand maybe employed, before the data is trans-formed back to an image for display;much superior results can be achievedthis way.

Needless to say, such operationsrequire a great deal of computation, andin order to speed up the 'numbercrunching' it is useful to have an extracouple of megabytes of RAM (semicon-ductor disc). Where speed is vital, adedicated array -processor is a practic-able proposition, now that the requisite'hefty' chips are available.

Removing noiseFor images obtained in electron mic-

roscopy or in astronomy, where one isdealing with low contrast data or signalsburied in a background of noise, it isuseful to have a means of averaging outthe noise and enhancing the desiredpicture elements. This is traditionallydone by taking some kind of long timeexposure, either by averaging a sequ-ence of stored images, or by continuous(recursive) filtering. Beyond this, it isoften desirable to calculate diffractionpatterns, for example to make a com-parison with those calculated from

'theoretical' molecular structures.

CorrelationAnother useful tool in the armoury of

the image processor is the ability tocalculate correlation functions. For aregular array of atoms on a grainybackground, for example, an auto -correlation exercise will emphasise theatomic array at the expense of therandom background. On the other hand,for comparison or alignment of twoimages, a cross -correlation would beused. The principle here is that thecomputed result shows peaks for thoseregions that are well matched. It is alsopossible to obtain correction signalsfrom this process, for rotational as wellas lateral alignment purposes.

Future developmentsIf current trends in semiconductor

science continue, more powerful pro-cessor chips and higher density RAMswill come onto the market, and this willencourage designers to pack more IPcapability onto their circuit boards;surface -mount technology is alreadymaking an impact here. As a result, theuser will be able to carry out morecomplex processes, or alternatively toachieve the basic results more quickly,and to do more work in real time.

This last point is quite important, sinceIP will not make much impact onproduction -line and other industrialinspection applications unless resultsare obtainable rapidly, eg fast enough toreject faulty items on a conveyor belt.Equally, we can expect to see moreintelligent office equipment, eg with theability to handle true images as well astext and graphics. This will improve'desk -top' publishing, as well as permit-ting better communications. With theparallel improvement in the telephonenetwork, a video telephone with reason-ably rapid response is not far away.

ConclusionJust as the microcomputer opened up

an enormous new field of activity inbusiness, science and hobbies, theimage processor will offer a similar boostto new applications in these fields. n

Fig 1 (left) SEM micrograph and (right) the histogram derived from it

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 41

DUO -BAND

LOOP ANTENNAHave a crack at this simple,

low cost designBy Richard Marris G2BZQ

Vhe loop receiving antenna which I

I shall describe here was designed foruse indoors next to a communicationsreceiver. It is simple, low cost and, aboveall, it works. It can be put together by themost inexperienced hobbyist, as long ashe or she can do a bit of woodwork andwield a soldering iron. It will also be veryuseful to many experienced SWLs andTxers!

It was initially required for the 160metre amateur band, although the pro-totype covered from 1.3MHz to 4MHz. Inother words, with an amateur band Rx it

Fig la The duo -band loop antenna

VC

500p

FIg lb Circu:t cl,agram

can be used for 160 and 80 metres, or witha general coverage Rx it can be usedfrom the HF end of the medium waveband right up to 4MHz (75 metres).

The intention was to provide a compactindoor antenna which would reduceQRM and QRN plus all the generalelectrical interference generated byhouse wiring, domestic appliances, etc.

The physical dimensions of the loopare not necessarily the best, but were themost convenient for me at the time ofconstruction.

Construction is dealt with in somedetail with the inexperienced in mind. Nodoubt, however, the old hand will adapt(or mutilate!) the design to suit his ownneeds - that's what it's all about!

DescriptionThe overall height of the loop is

approximately 36 inches, with 24 inchesmaximum width. The winding circumfer-ence is 68 inches.

The final construction is shown in

Figure la, and the very simple conventio-nal circuit in Figure lb.

The loop consists of four turns of wireresonated to frequency by a 500pFvariable capacitor. A one turn couplingcoil is used for connection via a coaxialfeedline to the antenna input of the Rx.Originally it was intended to fit a slowmotion drive to the resonating capacitor,but initial tests indicated that this is notreally necessary.

ConstructionThere are two basic units: the frame

unit with windings ( Figure 2) and thebase unit ( Figure 4). For the frame unit,cut out two pieces of 5/8 inch dia woodendowel to lengths of 24 inches and 35inches. These should be dove -tailed, asshown in Figure 2. At the centre 'X' a pilothole should be drilled using a fine drill,and then a larger drill should be putthrough to accommodate the fixing nutand bolt. If you go straight at it with thelarger drill, then you will probably split

T

11"

24"

InsulatorI tstl

4 1 turnI tatl

FIg 2 Frame unit with windings

or/ T

24"

42 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

the dowel. A spot of glue should beapplied to the mating surfaces andwashers put under the screw head andnut. The nut should be tightened until thewashers just start to 'bite' into the dowel.

A number of ideas were tried for thecorner insulators. Finally, at the local DIYshop four 13/8 inch diameter rubberdoorstops were purchased at 16p each.They are 1 inch long with a centre hole.This diameter ensures that the winding iswell away from the insulator fixingscrews.

A ridge appears around the end of theinsulator blocks, which convenientlystops the wire coming off the end duringwinding. The use of rubber ensures thatthe wire turns do not slip out of place ifwound tightly.

The corner insulating blocks should beattached as shown in Figures 2 and 3.Once again, don't forget a fine pilot holebefore drilling the bolt hole. A washershould be placed under the nut, and thenut tightened until the surface of therubber block makes a slight indentationin the dowel.

For the windings, multistrand 7/0.2 PVCcovered flex was used, with an o/d of1.20mm. Firstly, wind on a single turn (L2)in the middle of the insulator blocks andsecure it with tape at the bottom, leavingends of at least 7 inches which can betrimmed back later.

L1 consists of 4 turns of wire, and twoturns should be wound, evenly spaced,either side of L2 (see Figure 3) and theends secured. This can best be done bypre -drilling the bottom insulator, with a2mm drill, at the start and end of thewinding. Leave at least 6 inch wire endsfor trimming back later.

The turns should be 'dressed' to giveeven spacing - approximately 1/a inchbetween turns. This can be seen inFigure 3.

For the base unit (see Figure 4) the

following items are required:

500pF variable capacitor and knob.Coaxial socket to suit individual taste.Piece of fibre glass or paxolin circuitboard, 51/4 inches x 41/2 inches (notcopper clad).Piece of wood, 9 inches x 1/2 inch x 3/4inch.Wooden base 1 inch thick and 7 inchesminimum diameter (could be 7 inches x 7inches square).Metal bracket (size not critical - must berobust).Nuts, bolts, washers and wood screws asrequired.Two terry clips.

Firstly, as shown in Figure4, drill a holein the exact centre of the base, andcountersink to take the head of a suitablewood screw. Secure the base to thepiece of 9 inch x 1/2 inch x 3/4 inch woodusing a suitable wood screw and a spot ofglue.

Fit a convenient size metal bracket, asshown. Next drill the piece of circuitboard to take the coaxial socket andvariable capacitor, as shown in Figure 4.

The position of each hole is not criticalas long as the variable capacitor does notfoul the 1/2 inch x 3/4 inch piece of wood.

Using two small roundhead woodscrews, secure the piece of circuit boardto the 1/2 inch x 3/4 inch vertical member,as shown. Assemble the coaxial socket,variable capacitor and knob. Secure thetwo terry clips to the vertical member, asshown, and then clip the frame unit intothem, thus securing the two unitstogether as shown in Figure la.

All that remains is to trim back andsolder the ends of L1 to the variablecapacitor and the ends of L2 to thecoaxial socket.

OperationAfter it has been connected to the Rx

with a short length of coaxial cable, theloop antenna is ready to test. If a signal

1

SY4"

I..

41'2 ''

7"dia

5/8- dia. dowel

13/gdiameter rubberdoor stop

FRONT VIEW

Fibre glassboard

Coupling coil (1 turn /

Loop coil I 4 turns I

513" dia. dowel

fan3111=11111111111111111111111111111.110

SECTION

Fig 3 Detail of insulator assembly

4 V2'.--1101

Carefully drill &seeure with bolt,washer & nut.Tighten untildowel 'bites'into dowel.

IVTerry clips

Co -ax

MIMI

VC

11

S Slue-1_Fig 4 Base unit

Screw

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 43

DUO -BAND LOOP ANTENNAgenerating source is not available, thenit is suggested that the testing should bedone in the evening, when there shouldbe plenty of signals available.

Tune the Rx to approximately 3.5MHzonto a strong signal, and peak the loopVC for maximum signals. Repeat atapproximately 4MHz, and also at aroundmid -band. Repeat the operation at1.8MHz and 2MHz. If a general coverageRx is being used then check at frequentspots between 1.3MHz and 4MHz.

Next, tune to a medium strength signalin the 3.5MHz band, peak loop VC androtate the loop for maximum signal. Then

turn the loop slowly through 90 degreesand the signal should be eliminated orgreatly reduced. See Figure 5 for theloop polar diagram directivity pattern.Repeat the operation in the 1.8M Hz band.

Minor adjustments to the frequencycoverage of the loop can be effected bywidening or reducing the spacingbetween the wire turns. It is also mostimportant to ensure that the leads fromL1 to the VC are as short as possible.

It will be found that the nulling of theloop is very effective. Interferencecomes from other stations (QRM), and itwill be found that in most cases this can

be eliminated, or greatly reduced,except where two interfering stationsare on exactly the same or reciprocalbearing.

In the domestic area much electricalinterference is radiated from wiring anddomestic appliances (and the TV!), and itwill be found that a judicious use of theloop rotation will greatly reduce oreliminate this in most cases. Static fromelectrical storms (not overhead) is oftendirectional, and again it will be found thatthe loop is most effective in reducing theracket. It must also be remembered thatthe loop is a very convenient compactreceiving antenna for the lower HFbands.

Using a receiver with good RFamplification, it will be found that theloop can be plugged straight into theantenna socket. If the receiver hasmediocre or poor RF amplification, thenit is advisable to use a preamplifierbetween loop and Rx. Wideband RFamplifiers can be purchased commer-cially or made up from various publisheddesigns and kits.

This loop has been used over a periodof some months alongside the Rx, mostlyon 160 metres, and has produced goodDX results.

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44 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Over the last few months I have beenfocusing my attention mainly on

MW-DXing techniques and equipmentthat would allow more stations to beheard. It's about time now to take a moredetailed look at what sort of stations theMW-DXer is likely to hear. The MW bandis often overlooked by the SW listener,who views it merely as a source of localentertainment and information, but it isjust this accessibility that can attract thenew or casual listener into the world ofDXing. Indeed, it is true that many a radiolistener has found the MW band a freshchallenge, away from the mega -wattshort wave propaganda stations andtheir associated jammers.

Stations galoreThe MW band, covering those frequen-

cies between 525kHz and 1605kHz, isused around the world by broadcastersin virtually every country. There areliterally thousands of stations on the airat any one time operating on just 120channels available in the MW band.Faced with this daunting situation, onemight well give up any chance of hearingreally distant stations, but as we shall seeit is not all that difficult to pick out theinteresting from the mundane.

For the UK based listener tuningaround the MW band for the first time,the impression will be of a banddominated by local stations during theday and European stations at night.However, with a little care you'll soonpick out non -European languagesemanating from stations in North Africaand the Middle East which will be audiblemost nights. Some of these stations willbe up to 4000km away, but it should beremembered that the most audiblestations will be using powers of 1000kWor more.

Across the waterIf it is so easy to hear the Middle East,

why is North America, at roughly thesame distance, such a tough nut tocrack? In contrast to the megawattsradiating from the Mid -East, stations onthe other side of the Atlantic arerestricted to maximum powers of 50kW.Whilst there are a few exceptions to thisrule (located in Central and SouthAmerica), the majority of stations aretruly local operations using powers verymuch less than the upper limit. Even forthe experienced DXer, the AtlanticOcean can form a formidable barrier, yetfor most UK based DXers the first taste ofreally long distances will be a station inthe Americas.

It is often the case that many sleeplessnights and much perseverance areneeded to hear your first transatlanticstation. However, having jumped thishurdle, you'll wonder why it was impossi-ble to hear these stations before! Now, togive you a fighting chance, here are a fewtips and suggestions.

The majority of transatlantic stationsoperate on frequencies that are multi-ples of 10kHz, whereas the Europeansare spaced by 9kHz. This means thatthere are certain 'window' frequencies

by Steve Whitt

where there is 4 or 5kHz separationbetween stations on the two continents.Some of the best window channels to DXon are 580, 590, 670, 680, 770, 850, 940, 950,1130, 1210, 1220 and 1570kHz. There are, infact, a total of 24 such frequencies, but onsome, DX opportunities are limited bythe low power used by the target DXstations.

Don't forget that you are likely to hear arange of languages; obviously English isthe principle language of N America andmuch of the Caribbean, but you'll findsome French stations in Canada and afew stations in the USA operating inSpanish (even Hebrew and Polish areused by some stations). From LatinAmerica, Spanish is the dominant lan-guage, but look out for Portuguese fromBrazil, Dutch from Surinam and someEnglish from Guyana. In addition tolooking at the window channels fortransatlantic DX, there are a number ofother stations that are almost regularvisitors to these shores. Try looking aftermidnight for:CJYGI in St Johns, Newfoundland on930kHz playing pop music and using the'Q Radio' slogan.WINS in New York on 1010kHz withcontinuous news (a bit like LBC inLondon).WFAN in New York on 1050kHz withcontinuous sports and talk programmes(this station used to be the country musicstation, WHN).

For Latin America try for R Globo in Riode Janeiro on 1220kHz with a mix ofphone-ins, sports, news and music, all inPortuguese of course. As a final tip in thissection, you could try for the Caribbeanby looking at the out -of -band frequencyof 1610kHz, where you should find theEnglish religious programmes of theCaribbean Beacon located on the islandof Anguilla.

Finally, do not be too disappointed if atfirst you do not hear any transatlanticsignals, since reception is very depen-dent on good propagation conditions.Some days absolutely nothing can beheard, whilst on others reception is sogood that stations like CJYQ are audibleon just a simple portable transistor radio!

Whilst many DXers enthusiastically

chase rare transatlantic DX, they oftenoverlook the DX in their own backyard.Although many local radio stations canbe very difficult or even impossible tohear, they are often regarded as notbeing real DX on account of their closeproximity. However, they can presentquite a challenge to the listener andcertainly make a good target for both theseasoned DXer as well as the newcomerto the band. Under this heading I'dinclude all of the UK and Eire, wherethere are around 200 local stations on air,as well as much of Western Europe whichincludes another thousand or so stationsunder this umbrella.

To hear rare local stations the DXerneed not rely on special ionosphericpropagation conditions so much asskilled timing. It is sometimes onlypossible to hear a rare local station whena stronger co -channel station has closeddown (either for the night or perhaps formonthly transmitter maintenance). Inother cases it may only be possible touniquely identify a station when it optsout from its usual network programmingto carry local material. In addition, itoften pays to tune the band when specialevents are happening (such as publicholidays, government elections, etc)since stations will often extend or modifytheir usual broadcasting schedule, thuspossibly allowing reception of a raresignal.

Although I have made the distinctionbetween local radio and transatlanticreception, it should be remembered that,unlike the short waves, the MW band isprimarily a local broadcasting mediumno matter where in the world the signalcomes from. Nevertheless, radio signalsdo not respect geographic boundariesand MW reception has been reportedover distances as great as 20,000km.From the UK, however, some of thefurthest DX ever reported has been fromChile and the Philippines, both about12,000km distant (only Australia and NewZealand are further).

Info fileThis month the spotlight falls on two

very useful and highly recommendedstation listings. Firstly, there is the AM

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 45

MEDIUM WAVE DXINGRadio Log published by the NationalRadio Club (the premier MW -DX club inthe States). The log is a comprehensive,200 -page, loose leaf, A4 size book listingevery N American station in two lists(frequency order and callsign alphabeti-cal order). Information includes powers,operating status, networks, formats,addresses and verification signers(where known). Although I've spotted afew errors in my copy, this still remainsthe most up-to-date info source avail-able, because regular updates are pub-lished. The current issue is the 8thedition, which retails in the States for$12.95. DXers outside North Americashould write to the National Radio ClubPublications Centre, PO Box 164,Mannsville, NY 13661, USA for an exactprice (probably around $16).

Secondly, we come to the Brazilian SW,MW and FM List (8th edition) by AntonioRibeiro da Motta, which is a 44 -page, A5format booklet of interest to both MWand Tropical Bands enthusiasts. It onlylists stations in frequency order, butincludes info on callsign, power, hours ofoperation and partial address (town andpostcode). It even has an Englishintroduction. To order, send 8 IRCsdirect to Antonio at Caixa Postal 949,12201 Sao Jose dos Campos - SP, Brasil.

Clandestine DXIt seems to be a fact of life that

wherever there is war, strife or oppres-sion radio becomes a powerful weaponused by all factions in the struggle, sinceit provides such a universal voice.Indeed, in almost every coup d'etat thefirst targets are the broadcasting sta-tions.

Radio Liberacion, the new Contrastation beamed to Nicaragua, officiallybegan broadcasts on 15th January thisyear, using 50,000W of power on 1520kHz.With such a power it's not surprising thatI managed to hear this station back inMarch whilst on a DXpedition toAnglesey (it is regularly heard as faraway as Ecuador and Mexico), but it isquite clear that such a station is notoperating from a remote shed in theNicaraguan jungle. In fact, spokesmenfor the United Nicaraguan Opposition(UNO) have openly talked about thepurpose of the station and the nature ofits programmes, but they have notrevealed the transmitter location - bestguesses seem to indicate a location inHonduras, despite on -air claims that thestation is in northern Nicaragua.

Radio Liberacion operates entirely inSpanish from 6pm to 6am local time(0000-1200UTC) using the slogan, 'The

Voice of Those Who Have No Voice'.Look also for an ID as 'Escuchas RadioLiberacion, Voz de la Unidad Nicar-aguensa en la frequencia 1520kHz sur laonda large'. Good luck with this one but,as with most clandestine stations, don'thold your breath waiting for a QSL card.

Odds and endsSometimes whilst I am researching

material for this column I come acrosslittle snippets of unusual news. One suchitem concerns station WRHC, located insunny Coral Gables in Southern Florida.This station has recently received per-mission to move frequency and in doingso to relocate its transmitter site.Unfortunately, a small piece of radiohistory will be lost forever when thishappens since WRHC has its 10,000Wtransmitter site located offshore. It isactually the only multi -tower transmittersite to be built entirely at sea installedsolely on piers and pilings. In fact, thestation engineers can actually fish out ofthe windows and some have installedlobster pots in the pilings down below!

Well I'm afraid that's it for yet anothermonth and until we meet again I'll lookforward to your tips, queries or othercorrespondence- as usual c/o the Radio& Electronics World offices.

NEXT ISSUE

Radio&Electronics

WorldThe communications and electronics magazine

MULTI -ARRAY AERIALSCompact, high gain antennas for UHF TV and VHF/FM radio,

by Ivor Nathan

LINEAR INTEGRATED CIRCUITSDavid Corder presents the final part of his occasional

series on this subject

PLUS ALL THE USUAL FEATURES!On sale 10 September

To be sure of your copy, why not take out a subscription?

46 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

SPECTRUM WATCHIn the December 1986 issue of the IEE

Proceedings on Communications,Radar and Signal Processing, an articleby J I Glaser on 'Fifty Years of Bistaticand Multistatic Radar' presented someinteresting information on the Russian'Woodpecker', which so often makes itspresence heard on the amateur bands.Barry WA4VZQ posted some excerpts onan American bulletin board and youmight like to share some of theseinsights, since many people are a little inthe dark on this subject.

'A system recently developed in theUnited States which employs bistatic(two -site) operation is the AN/FPS-118over the horizon backscatter (OTH-B)radar.

This will be used to provide long-rangeearly warning against bomber aircraftand cruise missiles approaching thecontinental United States. This OTH-B,which operates in the 5 - 28MHz waveband, uses an FM/CW waveform ratherthan pulses to eliminate high peak -power components and to minimiseradio frequency interference.

'The Soviet Union has a similar OTH-Bradar, although information about this issketchy. The initial evidence of SovietOTH-B capability came to light in mid -1976. The first of these units, nicknamedthe 'Kiev Buzzsaw' or 'Ivan the Terrible',was a 2 megawatt transmitter near Kiev,augmented by a smaller receivinginstallation near the Black Sea town ofNikolayev. From these initial efforts, theSoviets have expanded their system intoa fully functional high -frequency earlywarning radar.

'Most of the information concerningthe Russian 'Woodpecker', as it is nowknown because of its characteristicsound, has come from the efforts ofamateur radio operators throughout theworld. There are currently three OTH-Bsystems in operation in the Soviet Union.

'The current Soviet OTH-B systemshave increased power and operate in the20 - 50MHz range. Their capabilities are1000 - 4000km, with longer rangespossible through multihop transmis-sion'.

As WA4VZO says, 'Just think what I

could do on 20 metres during the next DXcontest with their multimegawatt trans-mitter. I might even be heard over theW6s!'.

Pirates

Writing in Broadcast, Nick Highamnotes that despite the 209 raids carriedout last year on 70 land -based piratebroadcasters, there is still a healthyalternative radio scene in Britain. TX,

by John Andrews

one of the newer publications coveringthis field, claims that London boasts atotal of 43 regular unlicensed broadcas-ters and the rest of the country a further30 -plus. That last figure is probablyunderestimated.

In recent years, the DTI's RadioInvestigation Service has becomeincreasingly sophisticated, yet the mostpersistent offenders seem to be com-pletely undeterred. The north LondonGreek Radio station has lost more than100 transmitters confiscated during RISraids, yet their enthusiasm remainsunabated.

It is probably political rather thancommercial motivation that keeps itgoing, an argument supported by the factthat more than half of London's piratesare 'ethnic', mainly 'black music' sta-tions. Given the current state ofresources in government departmentsthe pirate radio phenomenon looks likelyto continue.

High technology

British Aerospace's military aircraftdivision is reported to be enjoying earlysuccess in its flight tests of a jointtactical information distribution system(JTI DS) on an air defence Tornado FMK3.JTIDS is a British -American project, withequipment manufactured by SingerKearfott and Rockwell Collins in the USAand by GEC Avionics in the UK. Thesystem offers high capacity, secure, jam -resistant digital communication for air,ground and maritime operations.

JTIDS operates just below the amateur23cm band and uses time divisionmultiple access techniques to provideeach user with controlled and simul-taneous access to a constantly updateddatabank.

During the initial flight tests, success-ful secure voice, text and fixed formatcommunications were establishedbetween the Tornado and a terminal onthe ground.

Plessey has also enjoyed success witha contract to give the Australian army themost advanced battlefield communica-tions network in the world. Known asProject Raven, the system employsfrequency -hopping techniques andoperates on both HF and VHF bands. Itincorporates substantial electroniccountermeasure capabilities and a novelfield repair facility.

A mobile workshop with sophisticatedelectronics and computerised test andrepair equipment is an integral part ofthe system and can be deployed inforward area to reduce time lost due tofaulty or damaged radios.

Instant auroras

For many years the more adventurousamong the amateur fraternity haveexploited auroras for making contactsbeyond their normal range, but nowresearchers in America are trying toexploit and enhance the Northern Lightsfor carrying operational traffic.

Professor Alfred Wong of the Uni-versity of California in Los Angeles ishoping to create a 'pie in the sky' orcircular charge in the ionosphere, whichcould be used as a cheap alternative tocommunications satellites for reflectingradio waves.

The aurora borealis, seen as curtainsof beautiful colours shimmering in theArctic skies, is hundreds of kilometreswide and its glowing apparition is causedby electrons raining along the lines ofthe Earth's magnetic field, which con-centrate near the poles.

Unfortunately it is not very stable orpermanent, but Professor Wong is aim-ing to change this.

During the past six years and at a costof some $4 million, he has built a 1.2megawatt radio station in Alaska. Bydirecting a small amount of RF energyinto the ionosphere he can measurereflections and reconstruct a kind ofhologram of the shape and intensity ofthe aurora. After this, 1.2MW of power

The picture shows a cellular radio antennaundergoing vibration testing at Marconi Com-munications Systems Ltd in Chelmsford

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 47

SPECTRUM WATCHcan be directed upwards to create a 'pie'of oscillating electrified air about onekilometre by 30km, which will reflectradio waves. Careful testing finds thecorrect resonant frequency to permitsignals to bounce off the pie.

Professor Wong also hopes to seedlarger fluctuations in the 40.000 mega-watts of energy estimated to be locked inan aurora by mixing two radio frequen-cies and broadcasting a third, lowfrequency around the world. This lowfrequency cannot support fast data ratesbut such signals could penetrate 30 feetinto the sea and would be suitable forsending coded messages to submarines,for instance.

Getting there

British Rail, which for some years hashad a nationwide trunk -dialling internaltelephone system, is close to completingits National Radio Plan which will give adirect -dialling radiophone capabilitycovering 98 per cent of the rail network.

The new National Radio Network istrunked, unlike the older 105/138MHzsystem, and operates in Band III, close to200MHz. It offers users the valuable

facility of intercommunication betweenmobiles and with the fixed network, andis remarkably economical in channelusage.

By using modern trunking techniques,mobile sets automatically select a freechannel from those available. Carefulplanning and frequency allocation havegiven national coverage with just twenty-four channels, and the system isdesigned to use the same channel forcall set-up throughout all of the twenty-five radio areas. Digital signalling isemployed for dialling and selectivecalling of mobiles, while air time is savedby allowing the user to key the wantednumber before pressing the transmitbutton.

The new system now covers about 60per cent of the country, while the oldermid -band system covers the rest for thepresent but is due to be replaced by 1995.Sets are also to be installed in traindrivers' cabs. starting on Inter -City trainson the London -Liverpool and Manches-ter routes.

They will be extended to cover allInter -City. freight and major provincialroutes by 1988. All equipment is beingsupplied by Storno, who are the maincontractors, and by Philips (Pye). Watchthis space for new developments.

QRO at VHF

High -power klystrons made by Philipsin Eindhoven are powering 'Tristan', theworld's largest particle accelerator,housed at the research facilities of KEK,the Japanese Laboratory for HighEnergy Physics. According to Philips, thetwin 508MHz klystrons - models YK1302(800kW) and YK1303 (1000kW) - are thefirst to use vapour cooling at high powerlevels. In all, the Philips klystrons willgenerate 9.2 megawatts of power for theKEK. They might go quite well on 70cm,too!

John Andrewspresents this lively

and informativenews column

every other month.Don't miss theOctober issue!

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Millions of components: thousands of different linesRechargeable Nickel Cadmium batteries (ex unusedequipment) AA(HP7) 1.25 volt 500 mA Set of four £2ITT Mercury Wetted relay 20-60 VDC Coil. SPCo, 2A 79p. 10-£5LED illuminates Red, Green or Yellow depending uponpolarity/current. 5 x 21/2mm Face

25p or 100 for £23 or 1000 for £20010,000 Resistors. 1/3 to 2 watt. 10 to 22meg. 1/2% to 10% NOT ajumbled mass, but ready sorted into values

£25 collected £29 Mail Order5mm Red Flashing LED 25p or 10 for £2.25Watch/Calculator/Lighter etc Mercury Batteries Made byRay -O -VAC 1C mixed popular sizes £1.50, 50 for £5.00IN4004 or IN4006 Diodes 300 for £6.50KBS005/01/02 3 amp 50 V/100 V/200 V/bridge rectifiers.35p/36p/40p. 10 off £3.20/£3.40/£3.70. 100 off £30/£31/£34Plessey SL403 3 Watt amp, From Bankrupt source, hence soldas untested 4 for 60p or 10 for £1.20p5mm LED, clear, lighting hyperbright (600mcd), red up to 200times brighter (gives beam of light) 25p. 100/£20, 1000/£150Mullard 5mm LED, 40 red, 30 green. 30 yellow - 100 mixed £7'HARVI' Hardware packs (nuts -bolts -screws -self tappers, etc)marked 35p retail, 100 mixed packs for £11.Modern silver/black/aluminium, etc knobs 50 mixed, £6 (sent as10 sets of 4 - 5 sets of 2 - 15 different type/sizes).

SEND PAYMENT PLUS 18p SAEPostal orders/cash - prompt dispatch.Cheques require 9 days from banking to clear.Crossed postal orders and cheques - add 20p handling due toBank's increasing 'commission on business accounts.

Cheques drawn on Barclay's Bank not accepted.Prices you would not believe before inflation!

BRIAN J REEDTRADE COMPONENTS, ESTABLISHED 30 YEARS

161 ST JOHNS HILL, CLAPHAM JUNCTIONLONDON SW11 1TO.

Open 11am till 6.30pm Tues to Sat. Telephone 01-223 5016

VARIABLE VOLTAGE TRANSFORMERS

5/UT 2201240V AC 50/80 OUTPUT 0-2150V200W 01 amp max C19 50 p&p 03 00 (C2568 inc VAT0 SKVA 2 5 amp max C22 03 03 75 (029 60 inc VAT)

1KVA 5 amp max C31 00 E4 25 1E10 54 inc VAT)2KVA 10 amp max C45 OD £550 (C5608 Inc VAT)3KVA 15 amp max C5900 06 25 (07505 inc VAT)5KVA 25 amp max C10500

10KVA 50 amp max £190 00 *;1'.15KVA 75 amp max 0285 00 ." satCarnage on request

111

.0,3 -PHASE VV TRANSFORMERSDual input 200-2105 or 3430-415V Star Connected 3KVA6KVA 10KVA available Phone for detailsComprehensive range of TRAIISPORNIMIS-LT.-ISOLATION & AUTO (110-240V Auto transf either casedwith American socket and mains lead or open frame

requesttypvailable for immediate delivery Leaflet on

ULTRA VIOLET SLACK MINT FLUORESCENT TUSKS411 40 watt C10 44 (01200 inc VAT) Callers only2f1 20 watt £744 01 25 p&p (0999 inc VAT)13in 10 watt E5 50 - 75C' P&p (E7 19 inc VAT)12in 8 watt C4 50 75p pap (E6 04 inc VAT)gin 6 watt 03 60 50p p&p (04 72 inc VAT)6in 4 watt 0360 - 50P P&P ICI 72 Inc VAT)230V AC SALLAST KT for either We Sin et 121,, tubes0.5For5013102.Ttu55bpes10£669600inpc,PVA75Tp)

(07 76;ric VATIWATT &

Complel0543.80 £3.50 soapI0e9.35 Inc VAT)400 WATT IN LAMPonly 02800 p&p C2 50 (35 06 inc VAT)175 WATT SUP SALLASTED BLACK !JONI

riliFICUPY1400 papOMNI Available with BC or ES fitting

Cr 25 (0,7 54 nc. VAT

1200 SLOE PUMPSBuy dined noon the invertersSOO OPI1 158 head 3 anopC12 08 0)01 50 (1562 inc VATI700 OPE ION head 3.8 amp015 50 pAp 01 50 )11955 Inc VAT,1750 OPII 1311 heed 9 map019 25 pap 02 00 )12444 inc VAT)Wd110111 ERASURE KITBuild your own EPROM ERMINE for a fraction of theprice of a made-uo unit kit of parts less case includes12in 8 watt 2537 Angst Tube Ballast unit pair of bi-pinleads neon indicator on/off switch. safety microswitchand circuit C1360 pAp 75p (1650 inc VAT)SANOAMO WESTON TIME Type 52312001250V AC 2 on/2 off every 24 hours 20 amp contractswith override switch leastal Ion 1111111.01160 neaten4in Dia 3in high 09 50E1 50 p&p (C12 65 inc VATI RATAlso available with Solar Dial Other Time Switchesavailable from stock

INNER NY4.113NT STROSII KITDeadwood tor Nees, Theenleal !man McAppro. 16 pules Adiustabie speed C45 DO P&PC200 1154 05 inc VATICase and reflector C17 00 p&p t2 00 121 65 inc VAT)SAE for further details including Hy -Light andindustrial Strobe Kits

WIDE RANGE OF XENON FLASHTUBESWrite'Phone your enquiriesROBOT EKTIOUINASTSSWAP precision Swiss -made ironies, rotor 6V DCGeared motor with 70 1 gearbox 6V DC - 16 rpm 3VDC - BromAmazing power no load current only 10 ma approxsize 40 x 25mm Ex Equip tested and guaranteedONLY 34.50 p&p 500 105 75 inc VAT)38.3 IIPIN GEARED MOTOR Torque UN Inreversible 115V AC inc star. capacitor C1400 p&p0200 (01940 inc VAT)Suitable TRANSPORININ for 230V AC operationE5 20 pile El 00 107 13 inc VAT)57NPN 240VContinuously rated reversible 601b/,n Manuf by GEC New ideal for garage doors curtains etc Inc,capacitor Only C18 00 -C2 pD 102300 ,0I VAT).

Mg*Ilsrbt'd;""t," m'dbyf ir,ryGVaiscVickers

Water 08 50 p&p C1 00 (11oVinienc VAT) NUS240V AC SOLW1041) VALVE designed for AirGasat 0 7 Water 5 psi inlet -outlet 46 BSP Forgedbrass body Mf Dewraswitch Asco CS 50 pap 01 00(C863 inc VAT) NMSCOOLING FAIN{ - BRAND NEVI200/240V AC American Boxer Pewee 7 -bladedhigh efficiency cooling unit 80mm act x 40rnrn deep400rn approxAmerican Boxer 'mini' 5 -bladed 92mm sq a 38rnmdeep 50 cfrn approxEither type at fraction of manuf s price £8 CO -C1 00 p&p )11035 inc VAT)SMFI - CROUZET Mini t t5V AC 5 -bladed 92mmsq x 25mm deep 40 ern approx Price 06 00 - Cl 00P&P 108 05 inc VATINEWOUIPNWIT PANS 120rnm sq x 38mm deep ineither 115V or 230v AC Tested and guaranteedPrice £7 75 - £1 00 Dap (07 76 inc VAT)VSM4 CENTRWULUIL BLOWW1 230V AC2800 RPM 023 amp Cast const inc mounting feet100rnrn dia impeller Outlet 40 x 43mm Overall size160 x 150 x 165mm long 01600 p&p 02 75 (023 86 incVAT)

PION STOCK AT MC= TINT DEFYCONPENTKMAC Geared Motors C F BlowersDC Motors Small AC CapacitorsMicroswitcries RelaysSolenoids AC A DC ContactorsProgramme Timers Synch Motors

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57 BRIDGMAN ROAD CHISWICK LONDON WI 58% utik, st.t01-995 1560 Lender, RCN 7JJ

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48 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Ida AtedzikeTRANSISTOR SELECTOR

GUIDEbyJ CJ Van de Ven

This guide has beendesigned to be of use to theelectronics designer,engineer or hobbyist.

Prepared with the aid of apowerful computer system,the specifications of manythousands of electronicdevices have been selectedand indexed in tabular form.

Several different selectionand sorting options wereused in the production ofthese tables, so it can be usedto choose a device, forexample, for a particulardesign application byreference to the electricalcharacteristics, case type,etc, or to choose areplacement equivalentdevice when there is aknowledge of the originaltechnical specification.

Bernard Babani (publishing)Ltd, £4.95. ISBN 0-85934-179-8

TRANSISTORSELECTOR GUIDE

SIMPLE APPLICATIONS OFTHE AMSTRAD CPCs FOR

WRITERSby W Simister

Anybody who needs to writearticles, reports, essays, etcon a regular basis willunderstand the benefits ofowning a word processor.

Spelling mistakes can becorrected without the need toretype whole pages ofmanuscript, and paragraphsof text can be deleted orinserted quickly and simply.

Now the Amstrad CPC464,

664 or 6128 computers, used inconjunction with disc drivesand the DMP1 or DMP 2000printers, can be transformedinto simple word processorsusing a Basic program only 15lines long.

The author assumes noprevious experience withBasic, so those encounteringthis language for the first timeshould experience littledifficulty.

A useful book for owners ofthe early Amstrad computers.

Bernard Babani (publishing)Ltd. £2.95. ISBN 0-85934-165-8

C01.31(1

MODERN OPTO DEVICEPROJECTS

by R A PenfoldIn this book the ubiquitous

Mr Penfold presents anumber of practical designswhich utilise modern opto-electric devices, includingfibre optics, ultra bright LEDsand passive IR detectors.

Although some of thedesigns are suitable forbeginners, most are aimed atthe hobbyist with someexperience of electronics

11 construction.

Bernard Babani (publishing)Ltd, £2.95. ISBN 0-85934-68-2

NEWNES

RADIO andELECTRONICS

ENGINEERSPOCK ET BOOK

17th echhon Keith kind*

RADIO AND ELECTRONICSENGINEER'S POCKET BOOKby Keith Brindley

The 17th edition of thisuseful book has beenconsiderably updated interms of the broadcastinginformation included and newdevelopments in the radioand electronics field.

The service engineer,designer and hobbyist willfind the data contained in thisbook invaluable and logicallypresented. At £6.95, it can behighly recommended.

Heinemann Newnes, £6.95.ISBN 0-434-90179-2

(247 to p(E co,e/FADCirkit

Ci rkit's summer cataloguepresents many new lines,especially in test equipment,with the introduction of a newfrequency counter, benchand hand-held digitalmultimeters, lab PSUs and auseful hand-held inductance,capacitance and resistancemeter.

The kits and module sectionalso includes new designs, alow noise 23cm receiver and a2 to 80 metre transverter toenable class A licensees tooperate on 80m using a 2metre multimode rig. There isalso an updated design of thepopular FDO kit withimproved DIP and anextended LF range.

Cirkit are also running acompetition in this issue of

the catalogue, and there aresix multimeters to be won. It ispriced at£1.20.

Cirkit Distribution Ltd,Park Lane,Broxbourne,Herts EN10 7NQ.Tel: (0992) 444111.

ECWAn informative and easy -to -

understand book, describingin detail how to get the bestfrom an oscilloscope, is nowavailable from Electronic andComputer Workshop Ltd.

Written specifically for usewith the cost-effectiveCrotech range ofinstruments, the booknevertheless provides ageneralised introduction to

the internal workings andoperation of an oscilloscope,describing the function of itscontrols, aimed at those witha basic knowledge ofelectronics.

The intricacies of X -Y useare covered, such as phaseand frequency measurement,and the abilities of Crotech'sbuilt-in component tester aredescribed, along with typicaldisplays of 'good' and 'bad'semiconductors.

Entitled How To Get TheBest From Your Scope, thebook is a valuable sourcedocument and is available bymail order from Electronicand Computer Workshop at£3.50 including post/packing.

Electronic and ComputerWorkshop Ltd,171 Broomfield Road.Chelmsford,Essex CM1 1RY.Tel: (0245) 262149.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 49

Latest igreitatukeOryx

Greenwood Electronics'new Oryx cataloguepictorially demonstrates thecompany's extensive range ofequipment.

Products illustratedinclude a wide range ofsoldering equipment and aidsto PCB construction.

Greenwood Electronics,Portman Road,Reading,Berkshire RG3 1NE.Tel: (0734)595843.

SolartronRecently issued by

Solartron Instruments is a160 -page hardback cataloguedetailing the full range of testand measurementinstrumentation availablefrom this division ofSchlumberger.

Details o1 many productsare given, coveringapplications from precisiondc voltage measurement tostate-of-the-art optical fibre

instrumentation.Products are divided into

three broad areas accordingto shared measurementtechnology, and each sectionis prefaced by a discussion ofthe technology, its historyand up-to-the-minutedevelopment.

This comprehensive, two-colour production is avaluable source ofinformation to anyonepurchasing or specifying testequipment, and is availablefree.

Solartron Instruments,Victoria Road,Farnborough,Hants GU14 7PW.Tel: (0252)544433.

BulginJust published, the new

Bulgin catalogue offers aguide to the company's rangeof electrical andelectromechanicalcomponents.

The new 272 -page

illustrated publicationincorporates the necessarytechnical data in easyreference format.

AF Bulgin and Company PLC,Bypass Road. Barking,Essex IG11 OAZ.

WalmoreThe 1987 catalogue from

Weinschel, now availablefrom Walmore, provides in its256 pages detailedspecifications for theextensive range of fixed,variable and switchableattenuators and other coaxialcomponents made byWeinschel. Among the manynew components featured inthe 1987 catalogue is theModel 150 compact binarystep attenuator. This highreliability attenuatorprovides up to 75dB of loss insteps of 5dB for frequenciesup to 18GHz. It has beendesigned for equipmentmanufacturers to build intomicrowave instrumentation.

Other new productsfeatured include precisioncoaxial panel adaptors foruse to 26.5GHz, a coaxialshort circuit and a dc block,each with Type N connectorsand for use to 18GHz.

Walmore Electronics Ltd,Laser House,132/140 Goswell Road,London EC1V 7LE.

Diamond H ControlsDiamond H Controls has

published a two -page, fullcolour leaflet on thecompany's embossingcapabilities for membraneswitch panels.

The leaflet explains bothpassive and tactileembossing and also givesdetails of the company'srange of standard dies.Diagrams and photographsare also included.

Diamond H Controls Ltd.Vulcan Road North,Norwich NR6 6AH.

RADIO & ELECTRONICS

BACK ISSUESWORLD

TO: Back Issues Department Radio &Electronics World Sovereign HouseBrentwood Essex CM14 4SE

NAMEADDRESS

POSTCODEPLEASE SUPPLY: (state month and year of issue/s required) NOTE.Jan & Feb 82 and Dec '83 issues not available

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Should you have anydifficulties obtaining acopy, phone (0277) 219876or write to CirculationDepartment, Radio &Electronics World,Sovereign House.Brentwood, Essex CM14 4SE

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Newstrade distributors: Argus Press Sales and DistributionLtd, 12-18 Paul Street, London EC2A 4JS. Tel: 01-247 8233

50 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Penetrate the four corners of the earth with the

DX "PENETRATOR"HERE'S THE SPECIFICATION* 3 elements on each band* Heavy duty 2kW rated* Gain up to 8dB* No spares problems as with imported antennas'

* Broadband operation* Stainless steel hardware* SWR less than 1.3:1

HERE S WHAT THE CUSTOMERS SAY1 VK7NOW "I have recently installed a DX -33 beam and I would like to advise youthat I am extremely satisfied with it. It certainly outperforms the TH3JNR which Ipreviously used and also the VSWR is lower.'2. G3AEE "This letter is to tell you how pleased I am with the DX -33 antenna Onunpacking the OX -33 I was immediately impressed with the quality of the hardware.and in operation it is lust as impressive I have used it on all three bands and havebeen obtaining excellent reports from DX stations all over the world I haveconducted tests with other stations and these show the electrical figures includedin the DX -33 specification are fully met in practiceCongratulations on a very fine product'

ROTATORS ...we stock the best. EMOTO...buy 'reliability'...buy EMOTO.

. WE ARE THE SOLE UK DISTRIBUTORSMOTO 105TSX For light HF and large VHF arrays

£218.50EMOTO 502SAX For heavier HF beams plus VHF/UHF

[304.75MB -303 Rotary bearing for up to 60mm dia E17.25452 Flexible mount for '105' £26.45451 Flexible mount for 1102/3. 502 E27.150

DX -333 Element3 Bands

SSB Power taster

Gives steady indication of peakoutput power on SSB.Type - PM2000A 2Kw to 30MHz

£86.82Type - PM2001 200W 50-150MHz

£63.25

NOW IN USEFROM VK7 TO VE7!

PRICES (INC CARR AND VAT)ANTENNAS

Cat NoWESTERN ANTENNAS (!:ards", paid)1075 00.7 2 ,'MHz 2 ele rays.Gamma matched, 20ft Doom1076 DX7/3 7MHz. 3 ele YAW, Gamma matched. 40ft boom1077 DX -51 Rotary dipole ter 213. 24, 21. 16 and 14M Hz

Price

C402.50C546.25ciaa.oe

1060 DX -6V 10-030m Multi -band vertical plus 30m C126.50Wet DX -3i Dipole 10/15/20m 2Kw p a p (103.501082 DX -32 2 element 10/15/20rn 2Kw p e p C184.001063 DX -33 3 element 10/¶ 5/20m 2Kw p e p C270.251064 DX -34 4 element 10/15/20m 2Kw p e p C356.501065 DX -31/32 Conversion Kit DX -31 to DX -32 C80.501096 DX -32/33 Conversion Kit 00-32 to 00-33 [136.25¶067 DX -33/34 Conversion Kit DX -33 to DX -34 086.25¶069 DX -103 3 element tern Yagi 0109.25l090 DX -105 5 element lOrn Yagi (161.001093 DX -40K Converts DX -31/2/3/4 to 40rn dipole C115.001094 DX"27/1 Rotary dipole for 27MHz CB .. [14.501095 DX-27/33ele Beam for 27MHz Gamma matched C92.001096 DX -240 2 ele quad 2 10 ¶5 & 20m [2434.501097 DX -260 2 ele quad 2.10. 16 16 6 2051 0310.50tee.) DX -7/14-2/62 ele 40m 6 ele on 5011 boom C920.00

KENWOOD

is) 4811WINE-Fat_ IF*

-xr

**VR-2000

R-2000The R-2000 provides outstanding performance through use of microprocessor controlled operating functions, allowing maximum flexibility and easeof operation throughout its operating range. An all mode receiver, it covers 150kHz-30MHz in 30 bands. on SSB. CW, AM and FM. Key features includedigital VFOs, ten memories that store frequency, band, and mode information, memory scan, programmable band scan, digital display with 24 hour dualclock, plus timer, and a host of other features to enhance the excitement of listening to stations around the world. Price, £599. R-1000 is £499.Western your 'one -stop' source for Towers, Antennas, Yaesu or Kenwood.

Weitern Electronic/ (UK) Ltd FAIRFIELD ESTATE, LOUTH, UNCS LN11 OJHTel: Louth (0507) 604955. Telex: 56121 WEST G

Payment by telephoneaccepted with Access

and Barclaycard

S N WILLETTSFACTOR

37 HIGH STREET, WEST BROMWICH, STAFFS B70 6PBTEL: 021 553 0186

Radio Television Video & ComponentsGRUNDIG Infra Red Remote control System VIF-KI (13 function) consist Transmitter TPV355 and ReceiverVI F -El. Brand new & boxed £5.99 P&P £2 6 volt battery for same £1.50 extra.Box of 10 VIF-El Receivers £12.99 P&P £3.50

" Wilo ow -

4

REMOTE CONTROLS Infra -red & Ultra -sonicReplacement for FERGUSON, JVC, PHILIPS,NORMENDE, THORN, ITT £22.50 GRUNDIG &SONY £25.50 P&P £1.00. Brand new & boxed, makerguarantee.GRUNDIG panels suitable for 2x4 Super Stereo£10 each. Power supply panel £29 Head assemblycomplete with heads £29 P&P £2.PYE (V2000) 21VR20 Video/Tuner-timer andcharger 15 TV channels, time memory, brand new &boxed £25 P&P £4.

V2000 blank Video tapes VCC360 £6.95 VCC480 £7.99. p&P £1.PANEL METERS 72x72mm, moving coil, 25 and 40 amp, £2 each P&P £1, new & boxed.'HARRY MOSS' 8 track cartridge player and F/M multiplex stereo tuner 12 volt. Brand new £5.99 P&P £2.`SAXON' lightweight Sportsman CRONOGRAPH ALARM watch, brand new & boxed £2.99 P&P 50p.Refurbished Televisions from £50 TELETEXT £99.VIDEO RECORDERS from £59-£199.We are interested in purchasing all types of stock -videos, TV-' portable cameras, etc.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 51

Pliny

40MPUTER WAREHOUSE0'

mitim.vc100s OF

THE ALLADINS CAVE OF COMPUTER AND ELECTRONIC EQUIPMENTDON'T MISS THE CPM Deaf

OF the CENTURYNOT LIME DATA OW.*

The ORIGINAL FREE OF CHARGE dial up database. Buy, browse or place YOUR OWN AO forgoods or services to sell. 1000's of stock items,

spares and one off bargains. Updated daily.ON LINE NOW. CCITT, 8 bit word, no parity.

For 300 baud modems call 01-679 1888For 1 200-75 baud modems call 01-679 6183

FREEYour monitor from its computer!! For

MOH QUALITY COLOUR TV SITonly £29.95 it becomes a SUM=

Thefabulous TELEBOX an INVALUABLE MUST for the owner orANYyideo monitor with a composite input colour or monochromeMade by a major UK Co as a TOP QUALITY, stand alone UHFtuner and costing OVER £75 to manufacture this opportunity togive your monad a DUAL FUNCTION must not be missed' TheTELEBOX consists of a compact, stylish two tone charcoalmoulded case containing ALL electronics tuner. power supply etcto simply plug in and convert your previous) y de Stated Computermonitor into a HIGH QUALITY COLOUR' TV SET. giving a realbenefit to ALL the I amity.' Don't worry if your monitor doesn't haveSound -THE TELEBOX even has an integral4 watt audio amplifierfor drIvIng an external speaker. PLUS an auxiliary output for Superbquality television sound via your headphones or HI Fl system etcOther features include. Compact dimensions of only 15 75 w75" d x 35 h. latest technology. BRITISH manufacture fully -tuneable7 channel push button tuner. AutoAGC ctrcidt SAW filter.LED status ondicator, fully isolated 240v AC power supply for totalsafety, Mares ON -OFF switch etc Marty other uses

LIMITED QUANTITY- DON'T MISS THIS OFFER!!ONLY £29.95 OR £24.95 if purchased with ANY of our;

video monitors Supplied BRAND NEW with full instructionS end 2 YEARwarranty. Post and packing £:350 When used with colour crt

The FABUL U PM TATUN PC2000Professional Business System

A cancelled export order and months of negotiation enables us tOO$er this professionalPC. CPU system, recently on sale at OVER E1400 at a SCOOP price just over the cost of

Y. the two internal disk drives'. Or less than the once of a dumb terminal"Not a toy the BIG BROTHER of the EINSTIEN computer. the DUAL PROCESSORPC2000 comprises a modern stylish three piece system with ALL the necessities for theSMALL BUSINESS, INDUSTRIAL, EDUCATIONAL or HOBBYIST USER Used withtne THOUSANDS of proven, tested and avaiiabie GPM software packages such asWORDSTAR, FAST. DBASE2 etc the PC2000 spectficatton. at our paces. CANNOTBE BEATEN.'The central processor plinth contains the 64K, ZBOA processor. DUAL TEAC 55F 51/4

Double sided 40/80 track disk drives It Mb per drivel. PSU, 4K of memory mapped screen RAM. disk control:sp. R$232,CENTRONICS and system expansion ports and tithes not enough a ready to plug tntoSTANDARD8 DRIVE port for up to FOUR8 disk drives either in double density or IBM format. The ultra shm 92 key, detachable keyboard features 32 user definable keys,numeric keypad and teat editing keys even Its own integral microprocessor which allows the main MCA to devote ALL Is time toUSER programs eltm !noting " IOSt Character' problems found on other machines The attractive. detachable 12 monitor combineSa green anti -glare etched screen wdb full swivel and tilt movement for maximum user comfort Supplied BRAND NEW with CPM2.2. user manuals and full 90 day guarantee Full data sheet and Info on request

COLOUR & MONOCHROMEMONITO SPECIALS

PC2000 Systemwith CPM Etc

COST OVER £ t 400

'SYSTEM ALPHA' 14 COLOUR MULTI INPUT MONITORMade by the famous REDIFFUSION Co. for their own professional computersystem this monitor has all the features to suit your tmmedtate and futurerequirements Two video inputs RGB and PAL Composite Video allow directconnection to BBC/IBM and most other makes of micro computers or VCRsincluding our very own TELEBOX An internal speaker and audio amp may beconceded to computer or VCR for superior sound quality. Many other featuresPIL tube. Matching BBC case colour. Major controls on front panel SeparateContrast and Brightness - even in RGB mode Separate Colour and audiocontrols for Composite Video input BNC plug for composite Input 15 way 'EYplug for RGB Input. modular construction etc etc

This Must Be ONE OF THE YEARS BEST BUYS. PC USERSupplied BRAND NEW and BOXED, complete wan DATA and 90 dayguarantee ONLY £149.00 as above OR IBM PC Version £165.0015 Day Tf skt E1.00 BNC skt 75p BBC interlace cable £5.50DECCA 8016 COLOUR monitor. RGB InputLittle or hardly used manufacturer's surplus enables us to offer dim specialconverted DECCA RGB Colour Video TV Monitor at a super low pace of only£99.00. a pace for a Colour monitor as yet unheard of, Our own Interfacesafety modification and special 16 high del tmtion PIL tube coupled with theDECCA 80 serves TV chassis give 80 column delmtfion and quality found onlyon monitors costing 3 TIMES OUR PRICE. The quality for the price has to beseen to be believed' Supplied complete and ready to plug direct to a BBCMICRO computer or any other system with a TTL RGB output Other featuresare Internal speaker. modular construction. auto degaussing circuit attractiveTEAK CASE. compact dimensions only 52cm W 34 H x 24 D. 90 dayguarantee Although used units are supplied in EXCELLENT condition.ONLY £99.00 + CarriageDECCA 80, 16 COLOUR monitor. Composite video input Same as abovemodel but fitted with Composite Video Input and audio amp for COMPUTER,VCR or AUDIO VISUAL use ONLY £99.00 + CarrREDIFFUSION MARK 3, 20 COLOUR monitor. Fitted with standard 75 ohmcomposite video Input and sound amp This large screen colour display is Idealfor SCHOOLS. SHOPDS. DISCOS CLUBS and other AUDIO VISUAL oat,cations Supplied in AS NEW or tittle used condition ONLY £145.00 + Carr

BUDGET RANGE EX EQUIPMENT MONOCHROME video monitors.All units are fully cased and set for 240v standard working wIth composite videoInputs Units are pre tested and set up for up to 80 Column use Even whenMINOR screen burns exist - normal data displays are unaffected 30 dayguarantee12 KGM 320-1 B/W bandwdth input will display up to 132 x 25 Imes £32.9512 GREEN SCREEN version of KGM 320-1 Only £39.959 KGM 324 GREEN SCREEN fully cased very compact unit Only £49.00

Carriage and Insurance on all monitors E1000

V110174:1FilII147i;t0111fillGOULD OF443,enclosed. compact switch mode supply with DC regulatedoutputs of +5v i 5 5a. +12v 2. 0 5e. -12e 0 la and -23v Ga, 002a Dim 18 xI I 6 cm 110 or 240v Input BRAND NEW only £15.95GOULD G6 -40A 5v 40 amp switch mode supply NEW £130.00AC -DC Linear PSU for DISK drive and SYSTEM applCations Constructed on arugged ALLOY chassis to continuously supply fully regulated DC outputs of +5v

3 amps -5v 4 06 amps and +24v - 5 amps Short circuit and overvoltageprotected 100 or 240v AC input Dim 28 x 12 5 a 7 cm NEW £49.94

Carriage on all PIUS £300

Manufacturer's BRAND NEW surplusDEC LA34 Uncoded keyboard with 67 quality gold plated switches on X -Ymatrix - Ideal micro conversions etc £24.95AMKEY MPNK-114 Superb word processor chassis keyboard on single PCBwith 116 keys Many features such as On board Micro Swig* 5v rail full ASCII

coded character set with 31 'unction keys numeric keypad cursor padand 9600 baud SERIAL TTL ASCII OUTPUT' Less than half price

Only £89.00 with data Carriage on Keyboards £3.50

PC2000 Business System with CPMand 'Ready to Hun' FAST Sales and

PurchaSe ledger, SuPPOrtS up to9000 Accounts. VAT etc

COST OVER £1700

NOW only £499Carriage InsuranZre 00 MODEMSr

PRESTEL - VIEWDATA - TELEX

PC2000 WordprOCeSSOr Systemwith CPM and TEC FP25 daisywheel i

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Various disk drive PSLI s Ex Stock SEE PSU section.HARD DISK DRIVESDRE/DIABLO Series 3025 Mb front load £525.00Exchangeable version £295.00. ME3029 PSU £95.00DIABLO 44/ORE4000A, B 5+5 Mb from £750.00CDC HAWK 5+5 Mb£795.00. CDC 978280 Mb RMO3

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D I PAll prices quoted are for U K Matnland pad cash with order In Pounds Sterling PLUS VAT Minimum order valueELMMinimum Credit Card orderE10.00 Minimum BONA FIDE account orders from Government Depts. Schools. UnMersities andestablished compamesE20.00 Where post and packing not indicated please ADD £1.00 + VAT Warehouse open Mon -Fri9.30-5 30 Sat 10 30-5 30 We reserve the right to change prices and specifications without notice. Trade. Bulk and Export

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52 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

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Due to our massive bulk purchasing programme, which enables us to bring you thebest possible bargains. we have thousands of ICs. Transistors Relays. Caps. PCBs.Sub -assemblies. Switches etc etc surplus to OUR requirements Because we don'thave sufficient stocks of any one item to include in Our ads we are packing all theseitems into the BARGAIN OF A LIFETIME Thousands of components at giveawayprices Guaranteed to be worth at least 3 times what you pay Unbeatable value andPerhaps one of the most consistently useful items you will every buy." Sold byweight

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 53

\MN IIKL14101 1DilD0145Compiled by Keith Hamer and Garry Smith

nespite a sluggish start to the month,sporadic -E DX -TV really got going

during the second half of May. Some ofthe openings were prolonged, some-times lasting from very early morninguntil after midnight.

The 24th and 25th were dominated bytropospheric activity, mainly fromFrance and West Germany, althoughsuspected ducting on the 24th permittedthe reception of Switzerland at UHF.

DX -TV logs for MayThis month we are featuring two

reception logs from the Leeds area. Thefirst covers up to, and including, May 19thand has been sent in by Mark Dent. Thesecond log shows conditions noted byKevin Jackson.9/5/87: MTV (Hungary) on channels R1and R2 with sample teletext pages at0950; JRT (Yugoslavia) E4 (from theZagreb studios) with programmes at1011; TSS R1 prog at 1015; TVE-1 (Spain)on E2 with show -jumping at 1135; RAI(Italy) IA (2 transmitters) and IB onprogrammes at 1311; NOS -1 (Nether-lands) E6 and E39: NOS -2 E45; NDR-1

(Norddeutscher Rundfunk - West Ger-many) E10; WDR-1 (WestdeutscherRundfunk) E9; HR -1 (Hessischer Rund-funk) E7; DDR-1 (East Germany) E6.17/5/87: TVE-1 E2, golf at 1505; unidenti-fied channel R2 greyscale pattern at1537; RAI with programmes on channelsIA (from 3 transmitters) and IB.18/5/87: TVE-1 E2, E3 and E4 withregional programmes at 1047; TSS R1UEIT electronic test card with digitalclock at 1056; RAI IA (3 transmitters) andIB with programmes at 1110; RTP (Portu-gal) E3 radiating the 'RTP-PORTO' FuBKtest card at 1234; TVP R1 and R2 showingthe PM5544 at 1245; DDR-1 E4 test patternat 1245; TVE-2 on channel E2 with a barpattern at 1418; RTP E2 'RTP LISB1' FuBKat 1634.19/5/87: TSS R1 '0249' monochrome testcard at 0945 from the Kuldiga transmitter;TSS R2 UEIT test card at 1000 from theLeningrad outlet; TSS R2 'EESTI TVTALLINN' PM5537 test pattern from theoutlet at Tallin; TSS R2 UEIT test cardwith a white rectangle in the centre ofthe top identification line - suspectVilnius transmitter; YLE (Finland) E4

'YLE TV1' FuBK at 1137; NRK E2 and E3with the 'NORGE TELEVERKET' PM5534at 1148; RUV (Iceland) on channel E4radiating the 'RUV ISLAND' PM5544 at1159; TVE-1 E4, 'TVE ANDALUCIATELESUR' caption with digital clock at1215; SVT (Sweden) E2 showing the 'TV1SVERIGE' PM5534 test card at 1220; TVE-1 E2 programme at 1220: YLE E3 'YLE TV1'FuBK at 1227; SVT E4 PM5534 at 1300;TVE-2 E2 bar pattern at 1526; RTP E2 andE3 broadcasting the 'RTP-PORTO' FuBKat 1546.20/5/87: TVP R1 and R2 PM5544 at 0645;TSS R1 'HOBOCTN' at 0652; TSS R2 UEITwith 'LRRTPC' identification at 0659; TSSR1 UEIT (Leningrad identification inCyrillic) at 0728; TSS R1 '0249' monosco-pic test card at 0739; NRK E3 'HEMNES'and 'KAUTOKEI NO' PM5534 at 0915; NRKE2 'STEIGEN' PM5534 at 0915; TDF L3prog at 0919; TSS R1 UEIT 'yrA' identifica-tion at 0924; unidentified R1 colour barsat 0946; NRK E4 'HADSEL' PM5534 at 0950;YLE E3 'YLE TV1' FuBK at 1006; RAI IA andIB progs at 1120; SVT E2 and E4 progs at1810 - also E3 at closedown at 2104.24/5/87: TDF tf1, L27 and L42; TDF

PHOTO FILE PHOTO FILE PHOTO

Fig 1 Armenian announcer received in Finlandby Jukka Kotovirta

Fig 4 Arabic newsreader - note the characteris-tic headgear

Fig 2 News programme from the Albanian TVservice, RTS

Fig 5 Czechoslovakian FuBK test card receivedin Malta via sporadic -E

Fig 3 PM5534 from ETP-2 in Greece, receivedby Carmel Sommit in Malta

4Fig 6 An old clock caption from Denmarkreceived some years aao by Simon Hamer

54 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Antenne 2 on L21, L34 and L39; TDF FR -3,L24 and L45; TDF Canal Plus, L5; ZDF(West Germany), E33, E34, E35 and E37;NDR-1, E50 and E53; NDR-3, E40, E42, E43,E48, E56 and E60; RB (Radio Bremen,West Germany), E45; BRT-1 (Belgium,Flemish -language service), E10 and E43;BRT-2, E46; NOS -1, E6, E7, E29 and E39;NOS -2, E27 and E45; RTBF-1 (Belgium,French language) E8; DR (Denmark) E7;TSI-1 (Switzerland, Italian language net-work), E34 from the Santis transmitter.28/5/87: All -day opening from 0715,including JRT on channel E4 with the'JRT ZGRB1' FuBK test card at 1102; JRT,E3 and E4 radiating the 'JRT BGRD'PM5544 at 1136; Band I was awash withsignals at around 1608.

Our thanks to Mark and Kevin forsupplying details about their impressivereception during May. Some loggingshave been omitted due to space restric-tions.

Reception round -upQuite a few interesting sightings and

observations occurred during May. TheRussian test pattern, known simply as the'Leningrad' type (or to use its technicalabbreviation, the 'UEIT'), has beenwidely observed using various inscrip-tions, which in certain cases can helpidentify the originating transmitter. UEITidentifications noted at Derby on the18th included 'Leningrad' (in its Cyrillicform), 'LRRTPC' (from the channel R2Vilnius transmitter in Lithuania) and'MTR'. Kevin Jackson managed to seethe old Russian 0249 monochrome testcard switch over to the UEIT whichcarried the name 'LATVIJAS TV' (LatvianTV) at the top. This occurred on channelR1 and it is thought to have originatedfrom Kuldiga.

A new Yugoslavian transmitterappears to be using channel E4, radiatingprogrammes from the Beograd studios.The PM5544 test pattern was seen byseveral enthusiasts during the morningof May 28th. The identification was 'JRTBGRD'. Normally this is seen only viaKapaonik on E3. Regular readers of thiscolumn may remember Kevin Jacksonand Mark Dent of Leeds seeing thisparticular PM5544 on channel E4 towardsthe end of last year.

Another mystery is the appearance ofthe Spanish TVE-2' logo in animatedform over channels E2, E3 and E4. At firstit was thought to be a programmeproduced by TVE-2, but there have beenrepeated sightings. Can anyone helpclear up this mystery?

Channel IA receptionRenewed interest has been centred on

channel IA, which until the late seventieshad been used exclusively by the Italianstate-owned 'RAI-1' service. Theintroduction of private (at one stagepirate) television favoured channels inBand III and UHF, with only a handful of

private stations choosing Band I alloca-tions. To the delight of the TV DXer, thissituation seems to be changing, thanksto the congested higher frequencies.

Last year saw the introduction of'Radio-Tele-Uno' on channel IA. Fortu-nately, most of the station's broadcastingtime seemed devoted to radiating acolour test pattern and its very distinc-tive design made identification easy.Prior to Radio-Tele-Uno, the only otherprivate station regularly seen was NordCentre Television, a service in operationnear Udine in Northern Italy. Towardsthe end of the last sporadic -E season, asmall number of enthusiasts spottedanother private station in existence onthis channel. It was identified by thesmall on -screen identification letters'TAI' which, thanks to our Italian cor-respondent David Bocca Corsico Picco-lino, who lives virtually next door to it,was confirmed as being 'Telealtitalia'with an ERP of 200W.

Since then, a few more stations havecome to light using this channel, such asRete 4, Canale 5, Italia 1 and, a morerecent discovery, TVA. At this stage, wedon't know what this abbreviationmeans, and only at the end of the monthwas it actually occupying channel IA.Early sightings were on channel E3 withthe logo 'TVA CANAL A'. This particularlogo is also superimposed in the cornerof the screen during programmes, soidentifying it shouldn't pose a greatproblem. For newcomers to the hobby,we hasten to add that the on -screenidentification isn't there for the benefitof the TV DX enthusiast. Its main purposeis to thwart attempts of programmepiracy by other stations. Many of thesestations remain on the air during thenight to prevent other services startingup and occupying the channel. Fortu-nately, all of this is good news for the TVDXer living outside Italy, but not forthose actually living there.

Arabic DXThere has been at least one definite

sighting of an Arabic station so far thisseason. Kevin Jackson of Leeds saw it onchannel E3 during an intense mid-morning opening on the 18th. Here atDerby, a suspected Arabic station cameout of the noise on channel E2 on the 17that 1050 BST. It consisted of a man talking,wearing Arab dress. The programmelasted for almost two minutes beforedisappearing into the noise. No othersignals were present in Band I at thetime.

Tunisian signals on channel E4 havebeen well received in the UK duringintense openings from the south. Fortu-nately, reception has coincided with atest transmission towards late afternoon.The FuBK test pattern is used with theidentification 'RTT' to the left of centreand its Arabic equivalent to the right.Transmissions are in SECAM colour and

originate from Ramada in the south ofthe country.

A reception report has arrived from aTV DXer living in Malta and his logindicates that an Egyptian transmitter isin operation on channel E3. Anyoneinvolved with TV DXing during theseventies should remember the listingby the EBU of a 1QkW channel E3transmitter at Port Said. Later listsdeleted this outlet and it was assumed tohave been taken out of service, resultingin the discontinuation of Band I for TVtransmissions. However, recent informa-tion shows two low power (900W) relayson channels E2 and E4 in operation atDumyat for the Egyptian 2nd and 1stservices respectively.

Reception reportsTrygve Thue, of Solheimsvik in Norway,

witnessed a sporadic -E opening on the19th with test cards and programmesfrom Central Europe and Russia. Thelatter country was present on channelsR1 and R2 showing the UEIT colour testpattern, but at 1258 co -channel signalsappeared which Trygve described as 'anunknown test card overshadowing TSS'.

A tropospheric lift on the 22nd broughtin early morning broadcasts for Trygvefrom the Durris transmitter located inScotland. Reasonably clear UHF chan-nels are available for Norwegian DXersthanks to the absence of high powertransmitters in Norway.

An excellent log arrived from SimonHamer, of New Radnor in Powys, detail-ing some of the more unusual DX whichwas around during the month. The bestday was the 28th when the sporadic -EMUF (maximum usable frequency) rosesufficiently for Band II TV reception totake place. The Italian RAI-1 outlet onchannel IC (82.25MHz vision) was pre-sent, coinciding with similar signals onchannels IA and IB.

However, the most significant eventoccurred when Russian reception mater-ialised on channel R5 shortly before 1800BST. The lower channels, R1, R2, R3 andR4, were carrying the same programme.The vision frequency of channel R5 at93.25MHz is extremely difficult for mostTV DXers to resolve owing to the highconcentration of FM radio broadcastsoccupying this part of the spectrum.Since Simon is situated in a valley he hasthe advantage of very few FM stationsbeing present, which indeed helped onthis occasion.

Another surprise occurred on channelIA, when a feature film was observed withthe identification 'NCT' superimposed insmall letters in the corner of the screen.The abbreviation stands for 'Nord CenterTelevision' and, although it was a raritylast year, it is the longest establishedprivate Italian service in Band I to beregularly received in the UK. Othergoodies included Rumania on channelR2 showing the news programme

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 55

1Dk-TV tICLUT101 IDE RTS'Telejurnal' and Austria on test card fromthe low power Birkenfeld outlet onchannel E3 on May 19th.

Bob Brooks of South Wirral has had anexcellent month, with DX receptionoccurring most days. Like most of us, healso noted that the bulk of signals arrivedduring the second part of the month andby the 29th most countries had beenlogged. For Bob, the 29th was one of thebetter days with an all -day opening frommost of Europe. At 1055 on E3 the usualSwiss FuBK with '+ PTT SRG 1' identifica-tion was noted but with a difference. Anadditional feature was a moving line oftext at the bottom of the pattern.

Tony Privett of Basingstoke was luckyenough to log two Arabic stationsfloating together on channel E4 at 1604on the 23rd. These arrived from the southand one of these must be Tunisia. Theorigin of the second station is uncertain.Morocco does have an E4 outlet but itslocation is some 800 miles south-west ofthe Tunisian transmitter. Perhaps thereis a more interesting explanation, suchas the introduction of another E4transmitter in North Africa. Tony queriedthe presence of a 'TVA' caption onchannel E3 on the 19th and 23rd, whichwe now know happens to be one of thelatest Italian private stations on Band I.

Carmel Sammut of Malta began TVDXing earlier this year, with manysuccesses in Bands I and III. Unfortu-nately, problems exist on UHF due tocongestion from Italian private stationsoperating in Sicily. Despite this, a fewstations do succeed in penetrating theband and to date UHF reception fromGreece and Tunisia has been possible.At Band III, Libya, Greece, Tunisia andAlgeria are frequently available. On May3rd, Band III reception consisted ofGreece on E9, Algeria on E5 and E10, andAlbania on R7. Egyptian signals werenoted on channels E5, E7 and E8 duringthe early evening of the 23rd but perhapsof greater importance was the presenceof the same programmes on channels E2and E3.

Finally, on the 6th via sporadic -E, anunidentified African station wasresolved between channels E3 and E4.This has been logged as channel R2 butthere is no official information availableto confirm its use in Africa. There is atransmission system K (in use by FrenchTerritories Overseas) which shares thesame frequencies as those of system DinBand III. There are Band I allocations forthis system and one of these channels,known as K3, does in fact lie between E3and E4. However, none of the Band I

channels are known to be in use but aninteresting entry was found in an earlyWRTHB, in which the Libreville transmit-ter in Gabon was listed as 'E3' and PortGentil as E10. Both transmitters usedsystem K. Could the prefix be wrong?This could explain Carmel's mysteryreception.

During early June, the RAI-1 PM5544was noted by a number of enthusiasts,with the 'RAI-ROMA' identification in thelower black rectangle.

Ray Davies, of Happisburgh in Norfolk,noted the Greek PM5534 test pattern onchannel E3 and the Iranian FuBK testpattern on channel E2.

Andrew Webster of Billinge nearWigan saw the Syrian PM5534 test cardon channel E4 on June 4th.

Service informationPoland: Despite previous rumours, itwould appear that TVP-2 will, in fact,continue to broadcast on VHF. Due tofinancial restrictions, only one new UHFstation is taken into service each year.Many viewers would be deprived of thesecond network if VHF outlets wereclosed down.

This month's service information waskindly supplied by G6sta van der Linden(Rotterdam, Netherlands).

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56 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

OSOOn these pages we present details of

interesting contacts from clubs and

individuals. We would be happy to

receive any similar items from readers

Bristol rallyA busy month awaits the

South Bristol Amateur RadioClub, who have been prepar-ing for some time for theBristol Radio Rally (specialevent callsign GB2BRR), to beheld on September 6th.

The club also has a videoevening planned for the 16th,followed by a computer activ-ity evening on the 23rd and alecture on the 30th. Plenty tokeep the club members occu-pied here!

The club meets everyWednesday at the WhitchurchFolk House, East DundryRoad, Whitchurch, Bristol,Avon. For more informationcontact Len Baker G4RZY.Tel: Whitchurch 834282.

SMC open dayOn August 30th, South Mid-

lands Communications Ltdare holding another specialopen day, similar to last

year's, to celebrate the open-ing of their new premises-anevent not to be missed, as it isnot going to be held annually.

SMC are offering 10% offnew equipment (exceptmasts), cash only, and therewill also be many ex -demoand second-hand bargains, aswell as a car boot sale.

SMC are offering a freeradio spec check, 1.8-430MHz,with prizes including anFT290R. In addition, there aremany local attractions, so itsounds like an ideal familyday out.

The venue is SM House,School Close, ChandlersFord Industrial Estate, East-leigh, Hampshire. Tel: (0703)255111.

Space programJohn Biro K1KSY is

apparently the latest DigitalCommunications Experiment(DCE) station to interface

Roger Worth (right) of the Bristol FM TV Group gets turned on with the aid ofFulton Parish Council

with the UoSAT OSCAR 11DCE, according to AmateurSatellite Report, Amsat'snewsletter.

John joins NK6K, N5BRG,WDOETZ and WA9FMQ in theUS, and VK5AGR among otherDCE participants outside theUK. K1KSY's home packetBBS is K1UGM in Wakefield,Massachusetts.

K1KSY will be able to for-ward limited packet traffic tothe authorised UK DCE sta-tions and other DCE stationswith which the US has thirdparty agreements. You canmonitor the DCE title frames

Car boot saleEach year the Dunstable

Downs Radio Club organisesand runs the NationalAmateur Radio Car Boot Sale,which has become a verypopular rally. Although manytraders are present, the eventcaters mainly for amateursselling to amateurs.

Bargain hunting at Dunstable Downs

There were over 250 stallslast year and more than 2,500visitors created a greatatmosphere, with people sell-ing many items from newtransceivers, computers andtelevisions to components,kits, aerials and, yes, someplain old 'junk'!

The club has managed to

provide a great day out for thewhole family, as the event isheld at one of this country'sfamous aircraft and motormuseums, 'The ShuttleworthCollection', located at OldWarden Aerodrome, near Big-gleswade, Bedfordshire. Themuseum has aeroplanes dat-ing back to the pioneers ofaviation, and many are still inregular flight today. Com-bined with a restaurant,souvenir shop, bar and chil-dren's playground, all set inthe Bedfordshire country-side, this makes for an inter-esting and unique day out.

This year the rally will beheld on Sunday 13th Septem-ber. It is open from 10am till5pm, and admission is 50p(parking free). Old Warden isabout 2 miles west of Biggles-wade and is well sign -postedfrom all major routes.Enquiries about the event andadvance plot bookings can bemade to Wendy on (0582)451057, or Clive on 27907.

by observing the DCE datatransfer in straight ASCII onU0-11.

Monitoring the DCE orother U0-11 data at 1200bpsrequires only a terminal and asurplus type 202 modem. UO-9data can also be monitoredwith the same set-up.

TV repeater GB3ZZThe Bristol FM TV repeater,

GB3ZZ, was switched on at8.30pm on June 2nd.

Filton Parish Council werevery helpful in providing thesite for the repeater for 'apeppercorn rent'. Withouttheir help a small group suchas the Bristol FM TV Groupwould have difficulty inmaintaining a repeater.

The repeater is on RMT2,which has an input of1249MHz and an output of1318.5MHz. To date, coveragereports have been receivedfrom Bath, Portishead, Chep-stow, Stroud and all overBristol.

Construction contestThe Farnborough and Dis-

trict Radio Society is having apre -AGM discussion on 9thSeptember, while later in themonth, on Wednesday 23rd, itis holding a construction con-test. For further details con-tact the club secretary, Tim,on Camberley 29231. The clubis pleased to announce theappointment of a new awardsmanager, Mr Ivor IrelandG4BJQ QTHR.

Club meetings are held at7.30 for 8pm on Wednesdaysat the Railway Enthusiasts'Club, Howley Lane, Farn-borough.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 57

QS0Video on radio

Club secretaries shouldnote that the Radio Com-munications Division of theDTI now has three videosavailable which can be bor-rowed free of charge - per-fect for a club evening.

Subjects covered are thefixed links mobile service andthe work carried out by thedepartment.

To obtain the videos con-tact the DTI, Radio Com-munications Division, TheLibrary Room, 605 WaterlooBridge House. WaterlooBridge Road, London. Tel: 01-275 3140 (24 hour answeringmachine).

Past and presentOn Thursday 10th Septem-

ber, Ray Marden G3MWF willtreat members of the South-gate Amateur Radio Club to atalk on the SARC's history.

This will take place at7.45pm at the Holy TrinityChurch Hall (Upper), GreenLanes, Winchmore Hill, Lon-don N21.

The club is also planning tooperate special event stationGB4EMC on 19th and 20thSeptember EnfieldTown Show at Enfield TownPark on HF and 2 metres.

For further details, contactDave G4YLL on (0992) 30051.

More about MorseThe Coventry Amateur

Radio Society starts itsSeptember programme with a2 metre direction finding con-test on the 4th.

For those who want to knowmore about Morse, specialtuition and a night on the airare scheduled for the 11thand 25th.

On the 18th the club isrunning an evening of minilectures, at their regular timeof 8.00pm on Fridays, at BadenPowell House, 121 St NicholasStreet, Radford, Coventry.

For more details of clubactivities, contact Bill HahnG3UOL, 91 The Chesils,Coventry CV5 9NA. Tel: (0203)414684.

Exhibition weekendThe Sheffield Amateur

Radio Club is holding anexhibition on Saturday 5thand Sunday 6th September,linked to the 'Sheffield Festi-val Spectacular'.

On the 21st the club hopes

to have a talk by Pete Shep-pard G4EJP on Raynet, due tobe held at 8.00pm in the FirthPark Stadium.

Details of both these eventsare available from AlanG8ZHG on (0742) 395287.

DX picnicIf you are in the Slough and

Windsor area on 12th/13thSeptember, the BurnhamBeeches Radio Club is hol-ding its autumn DX picnic.Bring good weather with you!

Club activities for themonth include a Packet Radiodemonstration on the 7th anda talk on slowscan TV on the21st.

The BBRC meets at theHaymill Youth and Commun-ity Centre, Burnham Lane,Slough at 8.00pm on the firstand third Mondays of eachmonth.

For more information con-tact Eileen Chislett G6EI L onMaidenhead 25720.

RATS auctionIf you want to combine

bidding for bargains with abarbecue, the Rugby AmateurTransmitting Society is hol-ding an amateur radio auctionand barbecue on the 8th,admission only 20p.

The event will be held at theCricket Pavilion, 'B' BuildingEntrance, BTI Radio Station.A5 Trunk Road, Hillmorton,Rugby, Warwickshire.

For further information,please contact Kevin MarriottG8TWH, 41 Foxon's BarnRoad, Brownsover, Rugby,Warwickshire. Tel: (0788)77986 (evenings only).

HamfestThe Lincoln Short Wave

Club would like a mention fortheir Hamfest, to be held atthe Lincolnshire Showgroundon the 13th. A barbecue willbe held on the 12th at thesame venue, if the weatherholds out.

Tom Arris G4OSB will pre-sent a lecture on 'QRP Com-munication' on the 23rd, andanyone wanting to know moreabout this or other activities,including a forthcomingphotographic contest, shouldcontact Pam Rose G4STO onGainsborough 788356.

Natter nightThe Bath and District ARC

is holding a 'Club Natter

Night' on the 16th and a VHFnight on the air on the 30th.

All meetings are at theEnglishcombe Inn, English-combe Lane, Bath at 8.00pm.Club contact is H WelchmanG6EIY on Bath 28010 day-times, Bath 318128 evenings.

How bazaarThe Wimbledon and District

Amateur Radio Society isholding its annual bazaar onthe 11th.

All meetings are on thesecond and last Fridays of

each month at 7.30pm in StAndrews Church Hall, Her-bert Road, Wimbledon SW19.

Enquiries should go toGeorge Cripps G3DWW on 01-540 2180.

BBC OrfordThe Felixstowe and District

Amateur Radio Society isstaging a visit to the BBCTransmitting Station atOrford on the 21st.

The new venue for thesociety is the Scout Hut, BathRoad, Felixstowe. All lecture

RAE CoursesCroydon College, RAE on Mondays from 7.30 to 9.30pm,Morse on Thursdays from 7 to 9pm, starting September. Forinformation, contact Tom G3EUU, QTHR.

Kidderminster College, Hoo Road, Worcestershire DY101LX, RAE from 23rd September, enrolment 7th, 8th, 9thSeptember, 2pm-8pm, course fees £25 approx. Classes 7pm-9pm Wednesdays, plus a Morse class on Tuesdaysdepending on numbers. Further details from D OakleyGODAA or Head of Department of Science and Technologyon (0562) 820811.

Brunel Technical College, Ashley Down, Bristol BS7 9BU,RAE enrolment on 8th and 9th September. Mondays RAETheory, Tuesdays Morse and Thursdays RAE practical.Tutor is Phil Brouder G3ZJH. Further details from theDepartment of Aerospace and RadiocommunicationsEngineering, on (0272) 41241, extension 2164.

Stevenage and District Amateur Radio Society (G3SAD),SITEC Ltd, Ridgemond Park, Telford Avenue, Stevenage,Herts, RAE classes from Tuesday 6th October, at 8pm.Further information from Peter Daly GOGTE. Tel: (0438)724991 or Andy Adamson on Prestel MBX 219994795.

Reddish Vale Evening Centre, Reddish Vale Road,Stockport, Cheshire SK5 7HD, RAE classes from thebeginning of the September term on Monday eveningsfrom 7pm to 9pm, Morse on Thursday evenings 7pm to 9pm,both courses are a series of 25 sessions. Enrolment is on14th, 15th and 17th September between 7pm and 9pm. Formore information, phone Dave Wood, course tutor, on(0606) 41511 between 12.30 and 1.00pm.

Avondale Evening Centre, Heathbank Rd, Edgeley, Stock-port, RAE enrolment for classes from 14th -17th Septemberfrom 7.15-10.15pm. For further information, contact Mr G RFranklin (Principal) on (061) 477 2382, or Rik WhittakerG4WAU (course tutor) on (061) 427 4730. A Morse course isalso planned for Mondays.

Clacton Adult Education Centre, Green Lodge, 180 OldRoad, Clacton on Sea, Essex C015 3AY, enquiries andenrolment from 7th September to 18th September. Classvenue will be Colbaynes High School, Pathfield Rd, Clactonon Sea, Essex C015 3AY. A 30 -week RAE course will pc heldon Wednesdays from 7-9.15pm, commencing 23rd Septem-ber, plus a 15 -week Morse course on Tuesdays from 7-9pm,commencing 22nd September. For further informationcontact Green Lodge Adult Education Centre on (0255)424151, or Mr J Harris G3LWM on (0255) 432621 (daytimes).

58 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

QSOmeetings take place at8.00pm.

Further details from PaulWhiting G4YQC, (0473) 642595(daytime).

Call the worldThe summer issue of Data-

com, BARTG's quarterly jour-nal, gives details of a world-wide RTTY DX contest, itsojective being for amateurs tocontact others around theworld in as many CQ zones aspossible, using the digitalmodes.

This takes place over 48hrsfrom 0000 UTC on 26thSeptember to 2400 UTC on27th September, but no morethan 30 hours of operation areallowed for single operatorstations. Multiple -operatorstations may operate the full48 hours.

Contacts may be madeusing Baudot, AMTOR,(FEC/ARQ), ASCII and AX.25(no digipeating QS0s).

Bands are 160, 80, 40, 20, 15and 10 metres, only onecontact per station allowed.

Standard CQ contest logand summary forms are to beused, samples from CO.Please include an SAE orappropriate postage. Entriesmust be in by 1st December1987 (postmark), althoughextensions will be con-sidered on request. Logsshould be mailed to CQ RTTYContest, 76 N Broadway, Hick-sville, NY 11801 -USA.

Meter meetThe Bury Radio Society's

meeting of the 8th will be onelectricity metering and willbe given by N Nurney ofNORWEB.

Regular meetings are heldon Tuesay evenings at 8.00pmin the Club Room at theMosses Youth and Commun-ity Centre, Cecil Street, Bury.

Don't forget! Wewant to hear whatyour club ororganisation is up to-write to the Editor.

Notes from the PastTo many amateurs it comes as a surprise

when they discover that the new idea theyhave thought of, or a new application of anold one, has long since already beenpatented. Equally great is their surprise tofind that such commonplace things as TVaerials, etc, cannot be marketed withoutinfringing on patents covering certainaspects that are already held by someoneelse.

Radio and electronic patents nowadaysare legion. Yet suprisingly enough we findthat the first patent in the way of a

'wireless invention' was not granted until1896. This was taken out by GuglielmoMarconi who was quicker than others inseeing the commercial possibilities ofradio communications. The foundations ofradio had long since been laid by thenineteenth century scientists. They hadregarded their work as a contribution toscientific knowledge - but, as far as we canjudge, they were blissfully unaware of thepossibilities their discoveries opened up.Perhaps they did not even look upon theirdiscoveries as having a practical value, letalone think of commercialising them.

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 59

SHORT WAVENEWS FOR DXLISTENERSBy Frank A BaldwinAll times in UTC, bold figures indicate the frequency in kHz

A % e

111 AWL

110,1 II II .- 1111

PI SA4111if %AMURwm-Vat troy

I last presented a review ofIsome Bolivian transmitters,then operating on the lowfrequencies, some years ago.In this update, informationboth on the country and thecurrent Bolivian short waveradio scene is presented forthe interest of newcomersand those DXers whose aim isto log some of the stations inBolivia.

The Republic of Bolivia inwest South America is one oftwo inland countries on thecontinent, the other beingParaguay. The legal capital isSucre, La Paz being thepolitical and commercialcentre.

The eastern part of Boliviais tropical, the northern sec-tion being in rain forestsdrained by rivers of the Ama-zon basin. The southern partmerges into the Chaco whilstthe western part is Andean,one cordillera of which tracesthe border with Chile. Theother cordillera runs north tosouth through the centre ofthe country. In the south-westthere is a large salt plain andin the north-west is the greatbasin of Lake Titicaca.

On the high Altiplano(plateau) and contained invalleys are the main centresof urban development,industries and transportation.

Bolivia is fortunate to havesome of the richest mines inthe world, products of whichinclude antimony, bismuth,copper, gold, lead, silver andwolframite. Thg importantmining centres are Oruro andPotosi, the cities of Cocha-bamba and Tarija beingagricultural and commercialcentres.

Indian settlements were inevidence long before thecountry became part of theInca empire, the Spanishconquistadores beginningtheir conquest in 1538. A largepercentage of the population,some fifty per cent in fact, isof Indian stock, the remainderbeing of white and mixeddescent.

The official language is

Spanish, the state religionbeing Roman Catholic, andthe country is governed by aPresident and Congress. TheBolivian peso was devalued inJanuary of this year, beingreplaced by the Boliviano,one million of the formerequating to a single Boli-viano.

DXing BoliviaThe reception of Bolivian

transmissions is a far fromeasy matter. Reports of suchtransmissions tend to besparsely scattered in theEuropean and UK short wavelistener press. The difficul-ties involved are mostly thoseassociated with the low pow-ers of many of the stations,who exist solely by cateringfor the inhabitants_ of therespective service areas.Moreover, as will be notedbelow, many Bolivian stationsoperate on out -of -band chan-nels often subjected to com-mercial interference.

Both late night and earlymorning listening sessionsare the order of the day whenone is attempting to tune toBolivian transmissions, thisbeing impractical to manylisteners, who are required toattend their respectiveplaces of work during week-days. Weekends are there-fore preferable when plan-ning a late night or earlymorning session, the hopebeing that propagationconditions prove helpful inLatin American reception.

Start hereOn 4421.6 Radio Reyes,

Reyes. is scheduled from 2315to 0335. Listed with a power of0.4kW, it is thought to haverecently installed a 1kWtransmitter. It has reportedlybeen heard signing -off at0240. This one has beenlogged several times recentlyby the writer.

I should mention here thatonly those scheduled timeslots coinciding with a periodduring which reception wouldbe possible for us here in the

UK are included in thisupdate.

Radio Santa Rosa, SantaAna, on 4440 programmes inSpanish from 2300 to 0230 witha power of 1kW, but is seldomheard outside the locality.

Radio Capitan Victor Ustari,Villa Tunari, identifying as LaVoz de Tropico, on 4458.2 ison the air from 2100 to 0200 at0.3kW.

In Santa Ana de Yacuma,Radio Movima is on the airfrom 2200 to 0300 at 1kW. It isreported from time to time byEuropean DXers and hasbeen entered into the log-book here several times oflate. The frequency is 4471.9.

Also in the town of SantaAna de Yacuma is the trans-mitter of Radio Santa Anawhich currently operates on4648.5 with a power of 1kW.The current schedule is notknown but it has beenreported by DXers at 2330 andlogged by the writer at 0121.

Guayamerin is the home ofRadio Paititi, entertaining thelocal populace on 4682.2 from2100 to 0300 at 5kW. This onehas also been heard severaltimes recently during goodconditions for Bolivian recep-tion here in the UK.

The frequency of 4710 isthat of Radio La Voz de laFrontera in Puerto Suarez,operating in Spanish from0900 through to 0330 at 0.5kW.

Radio Abaroa, Riberalta, ison 4712.4 from 1100 to 0400with a power of 0.5kW. beinglogged here at 0158.

On 4712 are the signals fromRadio Los Andes, Tarija,working to its stint from 1000to 0400 (Sunday around -the -clock). Often heard in Europe,the power is 2kW.

Logged by the writer andother UK DXers on severaloccasions over the past fewyears have been transmis-sions emanating from RadioNueva America located in LaPaz. The power is 1 kW and it ison the air from 2200 to 0400,the current frequency nowbeing 4794.9.

Radio Emisora Libertad.

Santa Fe, on 4810 is sche-duled in Spanish from 1000 to0300 at 1kW but alas co -channel occupants denySWLs world-wide a logging.

Radio Grigota in Santa Cruzde la Sierra on 4829.6 trans-mits from 2200 to 0300 (Sundayfrom 1100 to 0100) with apower of 5kW.

La Paz and locality is servedby Radio Fides on 4845 from1000 to 0300 (Sunday from 1200to 0315) with a power of 5kW.

Radio Paititi, Radio Fidesand Radio Grigota, all at 5kW,do represent primary targetsfor newcomers to the Bolivianhunt.

The 1kW Radio El Condor inthe town of Uyuni is sche-duled from 1100 to 0210 on4855. It is rarely heard in ourpart of the globe.

Radio 16 de Marzo, MinaBolivar, is now reportedly on4864.3, and reactivated, thisrepresents a change of fre-quency from the former 3365channel.

This update will be con-tinued in the next issue.

ISM '87Readers interested in the

short wave broadcast bandswill be interested to know thatthe International Short WaveLeague 1987, which com-menced operations on 1stJanuary this year, currentlyoffers to its membershiptwelve different DX awardcertificates, these beingavailable post free to mem-bers and applicable to bothamateur and broadcast inter-ests.

Each month a broadcastband is specified as theFeatured Band, this beingsurveyed by members. Subse-quent reports to leagueheadquarters are collatedand published in the monthlyjournal, Monitor, providing anindication of current activityon the set band. Additionally,results obtained on otherbands are featured.

Articles of broadcast inter-est to both international andtropical band listeners and

60 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

DXers are published, in addi-tion to amateur bandcoverage.

Various free services existfor members, including IBIS(ISWL '87 Broadcast BandsIdentifications Service),which provides station iden-tifications to those seekinganswers to their unidentifiedloggings.

Details may be obtainedfrom ISWL HQ, 10 ClydeCrescent, Wharton, Winsford,Cheshire CW7 3LA. A samplecopy of Monitoris available at60p post paid.

AROUND THE DIAL

AFRICABotswana

Gaborone on 3356 at 1846,UK recorded pop songs andmusic, announcements inSeTswana. This 50kW trans-mitter is on the air in Englishand SeTswana from 0400 to0700 and from 1500 to 2100.

CameroonYaounde on 4850 at 2102,

OM with an English newscastof local events. The schedule,in French and English, is from0430 to 0700 and from 1630 to0002. The power is 100kW.

Cape VerdeRadio Nacional de Cabo

Verde on 3931 at 1957, folksongs in Portuguese togetherwith local style music. Thepower is 10kW, the schedulebeing from 1900 to 0005entirely in Portuguese.

MalawiBlantyre on 3381 at 1845,

OMs with a discussion inChichewa. The schedule isfrom 0255 to 1105 (Sundayfrom 0325) and from 1300 to2210. The power is 20kW.

NigerNiamey on 3260 at 1947, YL

with a song in French. Diffi-cult to log owing to on -channel commercial interfer-ence, Niamey operates in0530 to 0645 and from 1700 to2201 (Sunday until 2301)entirely in French.

CENTRAL AMERICACosta Rica

Faro del Caribe (Light-house of the Caribbean), SanJose, on 5055.2 at 0425, OMwith announcements, somesongs in Spanish with music

typical of the locality. This5kW transmitter operatesfrom 1100 to 1800 and from2300 to 0600 (Saturday andSunday until 0612). There is anEnglish programme timedfrom 0300 to 0400.

Dominican RepublicRadio Clarin, Santo

Domingo on 11700 at 0120, OMwith a CID (Cuba Indepen-diente Y Democratica) iden-tification, followed by a talk inSpanish about Cuban involve-ment in Angola.

SOUTH AMERICABrazil

Radio Sao Carlos on 2420 at0153 on a good night for SouthAmerican reception here inthe UK, OM with promoscomplete with echo -effectthen YL with a song inPortuguese. This 0.5kW trans-mitter is scheduled from 0800to 0330.

Radio Difusora, SenaMadureira on 4117 at 0057, OMwith announcements in Por-tuguese, YL with a ballad. Theschedule is from 1000 to 0300at 1kW.

BoliviaRadio Padilla, Padilla on

3474.4 at 0005, announce-ments and folk songs inSpanish. At 0.5kW, R Padilla ison the air from 2200 to 0330 inSpanish.

Radio Abaroa, Riberalta on4712.4 at 0158, OM with aballad then YLs with a duet inSpanish. The schedule is from1100 to 0400 with a power of0.5kW.

EquadorRadio Naciona' Espejo.

Quito on 4679.9 at 0126,announcements followed by atalk in Spanish. RN Espejooperates from 1100 to 0500 at5kW.

PeruRadio Universo, San Igna-

cio on 6815.2 at 0202, YL with aballad then OM with anannouncement in Spanish.The schedule is from 2300 to0300, the power unknown.

VenezuelaRadio Occidente, Tovar on

3225 at 0337, folk songs andmusic then an announcementin Spanish. At 1kW, R

Occidente is on the air inSpanish from 0955 to 0400.

ASIAIndia

AIR Delhi on 9910 at 2135,play theatre in an Englishpresentation to Australasiatimed from 2045 to 2230.

JordanAmman on 9560 at 1405, OM

with a talk in English aboutthe history of some Africancountries, station identifica-tion then the pop song 'Pup-pet on a String'. The Englishprogramme from Amman tothe Western Middle East isfrom 1200 to 1600.

PakistanKarachi on 15605 at 1410,

cricket commentary in theEnglish Service directed tothe Persian Gulf area and theMiddle East from 1315 to 1545.Islamabad was in parallel on11615 and 15190 at the time ofreported reception.

QatarDoha on 11820 at 1843, local

style music and OM with asong in the Arabic prog-ramme for Europe, timed from1700 to 2120.

North YemenSan'a on 9780 at 0337, OM

with a harangue in Arabicduring the Home Servicetransmission timed on thischannel from 1000 to 2110.

SOUTH-EAST ASIANorth Korea

Pyongyang on 9960 at 2007,YL with a news bulletin duringthe English programme dir-ected to the Middle East,scheduled from 2000 to 2050.

VietnamHanoi on 15010 at 1900,

National Anthem, YL with thestation identification fol-lowed by the local news. ThisEnglish transmission toEurope is scheduled dailyfrom 1900 to 1930.

PACIFICAustralia

Carnarvon on 9655 at 0850,OM with news of local spor-

in an Englishthe Pacifictimed from

ting eventsprogramme ofIslands Service0700 to 1030.

Shepparton on 11910 at0600, OM with the stationidentification and a timecheck, followed by news ofPacific events and affairs.

This English programme isbeamed to the South Pacificarea from 0400 to 0630.

CLANDESTINERadio Iran on 7070 at 1827,

the 'Internationale' then YLwith the station identificationand a talk in Farsi (Persian).This transmission is for Mid-dle Eastern consumption, thefrequency used resulting indifficult reception due toamateur band transmissions.This clandestine transmitter,formerly announcing as FreeVoice of Iran, is located inIraq. Radio Iran is organisedby the National ResistanceMovement of Iran and is pro-Bakhtiar, the ex -PM.

Radio Iran Toilers on 10870at 1548, YL and OM alternatewith items of, presumably,news in Farsi. Scheduled tothe Middle East from 0230 to0330 and from 1530 to 2100, thisclandestine station broad-casts via Radio Afghanistanfacilities and is pro -IranianTudeh (Communist) Party. Itidentifies as Radio -yeZahmatkeshan-e Iran.

NOW HEAR THESEXinjiang PBS, Urumqi,

China on 2560 at 2225, man-dolin orchestral music withannouncements in the higherprogramme scheduled from2200 to 0130 with a power of50kW.

Radio Orion, Johannes-burg, S Africa, on 3955 at 1958,announcements in Englishthen the song 'Oh Play to meGypsy'. This Afrikaans/Engl-ish programme is radiatedfrom 1930 to 0300. The poweris 100kW.

Radio Candip, Bunia, Zaireon 5066 at 1844, songs andlocal style music, OM withannouncements in vernacu-lar. The schedule is from 0330to 0600 and from 1300 to 1915 inFrench and local vernaculars.The power is 10kW, the fre-quency is subject to commer-cial interference.

NOW LOG THESERadio Zaracay, Santo

Domingo, Ecuador on 3395 at0354, YL with a ballad inSpanish, OM with someannouncements then sign -offwithout the Hymno Nacionaleat 0400. The power is 25kW andthe schedule is from 1000 to1400 and from 1900 to 0400entirely in Spanish.

SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 61

FREE CLASSIFIED ADSFREE CLASSIFIED ADS CAN WORK FOR YOU

We are pleased to be able to offer readers the opportunity to sell yourunwanted equipment or advertise your 'wants.

Simply complete the order form at the end of these ads. feel free to use enextra sheet of paper it there is not enough space on the order form. We willaccept ads not on our order form.

FOR SALE AOR AR2002 scanner in mint condition, only 1week old. Boxed with power supply, battery leadand telescopic whip aerial. £450. Extra coverage of800-1300MHz not required, hence reason for sale.Also SSB adaptor for Grundig Satellit 2000/2100.£20. Telephone Brian on Dungannon (08687) 24029between 0930 and 1200 (Mon-Thur) or after 1830any evening Dressler active antenna, ARA-30 200kHz to40MHz, as new. Purchased Feb '87 cost £122,bargain at £80. Tel: Kirkham 683098, Lancs TV-DXers! Are you interested in TV -DX? If so,Screen Europe is the newsletter for you! It coversall aspects of long distance TV reception with logs,photos, programme schedules, articles and muchmore! For a free sample copy and full subscriptiondetails send an SAE to 0 Anderson. 2 Burry Rd.Silverhill, St Leonards, East Sussex TN37 6QX R2000 Trio with VC10 + CW filter, offers over£500 for this super receiver. 100kHz to 174MHz.New model has come so need space. Tel: after 6pm(0706) 218290 3 Pye Motophones. high band AM, £40 each or£110 for the 3. One high band Burndept FM unit. nomic or I/spkr, squelch fault, £50. Bags of 100 newmixed components, £2.50 each. Xtals type T71Kasst freq's, £1.00 each or 10 for £8.00. Buyer to paypost and packing. Tel: C R Cooper, (0705) 386254 Goldring Lenco GL75 stereo, 4 speed transcrip-tion, turntable. in teak case with Shure M55Ecartridge. No rubber turntable mat. Also Eddy-stone type 820 FM tuner. Tel: (0730) 62049 Trio 9000 2 metre t/ceiver, boxed. Trio dc powersupply, PS20. Base unit BO Also peakwattmeter 5. 20, 200 watts. Offers to GeogeG140H I. Tel: (0232) 860243 Geared tuning condenser for HRO receiver,good condition, mains transformer, 230/250 in,115V out. Genuine Ericsson BBC headphones(vintage), Burroughs tape cassette drive module.150 untested (cased) home-brew ATU for amateurbands, transmit, receive. transformer ex CR100.working, offers. Borthwick, 92 Linglie Road,Selkirk, Selkirkshire TD7 5BD Solartron regulated power unit 2 x 6.3V, 5 amps,20-500V, variable 300mA. 0-170V negative line. Builtlike a tank. Offers. Almost complete 19 set Mk111,free to good home. Sinclair Mk14 with improvedkeyboard and display tape interface, manual andbook Understanding Micros with MIC14, £35.David, 160 Thoday Street, Cambridge CB1 3AX. Tel:(0223) 210722 Hewlett Packard 1415A time domain reflecto-meter (pulse test set) in 140A oscilloscope. withmanuals, £15. Or swap 1415A module for 'scopetimebase module. Phone Alan (0342) 312329. after6pm HP-41CX calculator, perfect condition. £125.Also CWR-610 RTTY decoder, £100. MicrowaveModules MTV435 TV -Tx, £100. Diawa IR mobile mic,£15. 250A 100piv diodes. £3 ea. PT100 tempcontroller. £10. 100 kilowatt valve type RS-3150CS,offers. This item very heavy, prefer buyer collect.Contact lain GM1PSU. Tel: (0506) 857262 Sony ICF6700D, mint in box with PSU, £95. Apple80 col card, £15. Will swop for SX200N with cashadjust. Phone New Milton, Hants (0425) 616490 Tristar 747 120 channel AM. FM, USB. LSB. willconvert to 10m, £40 ono. 6 amp 13.8V PSU, £12 ono.Write to S R Mohan, 75 Pennine Road, SK13 9UL Yyoko UHF/VHF system B/G/I TV for British andContinental, unwanted present, offers. NATO 2000for sale, suitable to convert to 10MHz, offers. R2000memory, 3 months old, £375. Tel: (0283) 221870 Iwatsu 20MHz dual beam 'scope, excellentcondition, manual probes, £200. No offers, worthover £300. Or exchange for Cortex computer

Send to Radio di Electronics World. Sovereign House, Brentwood. EssexCM14 4SE

DEADLINE AND CONDITIONSAdvertisements will be inserted in the first available issue on a first come firstserved basis. We reserve the right to edit and exclude any ad. Tradeadvertisements are not accepted,

(working), preferably with disc support, orexchange for Amstrad or Commodore + disc, orcassette units. Enclose stamp for reply. TechnicsSL10, linear tracker t/table. needs new perspexinlay and stylus, otherwise immaculate, worthwhen new £250+, definitely good buy at £150. Nooffers. Write with stamp first to: Millhouse, 7Bentinck Street, Mansfield, Notts NG1B 2QQ R107, stored last 20 years, don't know if it works!£20. Also SX27 VHF, £20. Trio MC60A desk mike, asnew. Buyer collects. Tel: (0908) 313507, MiltonKeynes Trio TS820 with digital frequency readout equalto TS820S. Complete with YG-88C CW filter andMC35S noise cancelling mic. Modified for Amtoruse and also for operation on 10MHz. Recent newdriver and 6146B PAs. Excellent condition, £440.Will deliver for cost of petrol. Also ICs FAX -1decoder. Requires G/C receiver and Epsoncompatible printer, £200. G3RDG. Tel: 01-455 8831QTHR FRG9600, all mode scanning receiver, modified60-950MHz, no gaps, as new. £325 ono. Icom AH-7000 super wideband omnidirectional antenna.stainless steel discone, covers 25-1300MHz. Tel:01-472 9056 after 6pm, £45 ono Panel mounting meters, mostly MA: 0 to 10MA. 0to 15, 0 to 20, 0 to 50, 0 to 100, 0 to 1A, £3 each. Willsell separately. Please write for details. Bewlet, 26Summerfield House. Guilden Sutton, near Ches-ter, Cheshire CH3 7SW FRG7700 receiver with FRT7700 ATU andservice manual, both as new, £285. World Radioand TV H/book, 1987 edition, £9.00. Bound volume1973/4 goodcondition, offers. TV Explained by Miller andSpreadbury, 1957. Band I/III. offers. DX -TV Recep-tion by Roger Bunney, offers. Geared tuningcondenser for HRO, good condition, offers.T/former 115V out, offers. buyer collects or payscarriage. Borthwick, 92 Linglie Road. Selkirk,Selkirkshire TD7 5BD Yaesu FRG9600 Mkt. Coverage 100kHz 950MHzusing ADK HFC1 HF converter antenna socket,with PA4C ac adaptor. 5 months old. four hundredpounds or near offer. Jack Wingrove, 114Wakehurst Road. London SW11 6BT. Tel: 01-2284835 MM 70cm transverter 2mtr i/p, £110. Rig framestore kit 3 PCB with memory chips, 18 other chipsplus nearly all RC switches. etc, £45. Electronicmultimeter with 50/75 ohm RF probes with leads,etc, £27. JVC 3 inch b/w TV/rad TV bands 1/3/5, suitDX -TV with ac PSU, £60. Atari games, various from£2. Atari ham progs Morse, Maidenhead, talcs£3.50 disc/cass. Tel: Ben (0562) 743253 Tentec Argosy HF transceiver, with PSU,calibrator, audio filter inbuilt, xtal CW filter.Mobile leads, manual plus Tentec ATU, all vgc,£450. Original boxes. Yaesu FRG7 Rx with externalfreq counter and details, manual, vgc, £120 ono (inoriginal boxes). HF beam TB3 MK2, £100 ono.G4GWE. Tel: Milton Keynes 511129 Trio R1000 receiver, AT1000 ATU, royal bluefolded dipole, £240. Sony Air -7 scanner, boxed andin mint condition, £180. Paul. Tel: Northampton(0604) 413131 after 5.30pm Scanner users. I have photocopies of servicemanuals for the following scanners: Tandy,Realistic, Pro 30, Pro 31, Pro32 and Pro2021, Yaesu,FRG9600 and combined AOR 2001-2002 (UK)version, all at £6.00 inc P&P. Phillips. Tel: 01-7430811

WKS1001 Tx/Rx. £60 ono. Also magazines April1985 to December '85 except July '85 RadioCommunication , and January '86 to December '86Radio Communication . Also January to July '87Radio Communication . January '85 to December

'85 except February '85 Amateur Radio . AndJanuary to February '86 Amateur Radio , Februaryto June '85 Practical Wireless and June '84 toDecember '84 Radio Electronics , January '85 toDecember '85 Radio Electronics and January '86to December '86 except July '86 Radio Electronics. Also January to July '87 Radio Electronics .

Finally February, April, June and July 1985 HamRadio Today. and February and May '85 ShortWave Magazine . All in good condition. Sensibleoffers only. Mr Martin Fuller, 37 Greenfield Close,Eccles, Nr Maidstone. Kent ME20 7HU. PS havejust found the July Radio Electronics ! Free: Large quantity of components, includingsome transistors, just send stamp. Some largeritems, £1 post. Not just electronic parts but somephotographic items too. Send stamp for list. All bypost only. Mr Lawrence, 7 Griffin Crescent,Littlehampton, Sussex Vintage parts. Carbon rod resistors (spot. tip,body colour coded) and small wire -wound, colourcoded resistors. Just the job if you want thatvintage set to look right. Send SAE with your exactrequirements, description or enclose old resistor,send cheque/PO, 50p per resistor or take pot luckand buy 50 assorted for £5.00. 100 assorted £9.00.250 assorted, £20 (post free). Mr K Bailey, 40Seymour Close. Selly Park, Birmingham B29 7JD.Tel: (021) 472 3688 Shack clear out. space needed for new project,so selling large quantities of ICs, caps, relays,boards, and loads more! Two big lots (approx 251b),£25 each inc post, plus 5 small lots (approx 51b), £8each inc post. Stock up with really good stuff at agreat price! Alan Kelly, 1 Bryn Seion, Rhosgoch,Anglesey, Gwynedd LL66 OAE Advance AF sig gen. type H-1 with manual,£15.00. Bradley Electronic multimeter dc -

1500MHz with probes and manual, £20.00. SGBrown prof padded headphones. £5.00. 2 metremobile whip and mounting pod, £3.00. Mobilehand-held PTT mic (Racal), £5.00. Mobile 12V PSUfor use with scanner Rxs Bearcat, SX200 etc, £5.00.4 h/duty ceramic AE insulators. £3.00. BA/metricsocket driver set with ratchet for radio/TV work -new. £4.00. 13A fused distribution block, 6 sockets,£5.00 Box of radio valve & transistor data books,radio text books. RadComm & Amateur Radiomagazines. etc. £8.00 the lot. Box of useful radiocomponents. meters. PSU modules, packets ofnuts & screws, resistors, caps, clean PCB, etc,£5.00 the lot. G4FZG OTHR. Tel: (0242) 580329 DX -TV: Goldstar 12in monochrome VHF/UHF,covers bands 1,3,4 and 5, system B/G. Rotary tuners- VHF tuner clicks to channels E2 -E12 but finetuning control allows reception of the whole band1 and 3 frequency range, giving excellentselectivity. One year's use only, as new. etc. Stylishmodern 'upright' design. Single VHF/UHF aerialinput socket plus removable whip aerial. Comeswith full details and circuit diagrams for multistan-dard conversion. £75. Please contact Mike onPorthcawl (065671) 5813 Yaesu FT757 GX transceiver, £625; FP757 HDheavy duty power supply. £190: FC757AT Automa-tic ATU, £290: realistic Pro -32 200 channelprogrammable scanner with accessories £220;video camera power supply with leads. £19; LCRbridge. £12; transistor tester, £9. valve RF/AFsignal generator, £12: home-brew 'scope £17;Miranda 35mm camera auto focus and exposure,motorised with flash, E45; Spectrum Plus computerwith interface one and microdrive with amateurradio software, £70: Scarab Communicationencode/decode board for RTTY and CW. £15;Scarab RTTY and CW terminal unit, £35; Scarabsoftware for RTTY and CW, £7; Scarab hardwareand software for Rx SSTV, £12 (all for Spectrum);

62 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Multiface One with monitor 0/P and joystickinterface, £12; Boris Diplomat dedicated chesscomputer with infinite levels of play, £25; largestocks of radio mags vis PW, Radio and ElectronicsWorld, Radcom, Television, Elektor plus manyothers. Gordon Jackson, Stanmore, NW London.Tel: 01-907 2253

WANTED Amateur progs etc for MSX computer. HaveTandy spare keyboard, suits Radio Shack compu-ters. Texas 7199/4a power unit, manual and leads.Lots Spectrum programs. J Brown, 45 Marl-borough Avenue, Falmouth, Cornwall TR11 4HS Military equipment: R107, R109, TCS12, 38AFV.Command series equipment including dynamo -tors, 19 set PSU. working or for spares. Alsomounting bases, grills, canvasses, connectingleads, manuals, spares, etc for the above. AR880loudspeaker. Other military receivers, transmit-ters, equipment etc considered. Can possiblycollect. Tel: Tyneside (091) 4103706 Scanner owners - can you help? Am compilingUK complete HF/VHF/UHF aeronautical fre-quency list. I need any frequency information oncivil/military/company communications, pri-vate/company airfields, airport security/opera-tions, airborne traffic spotters, police air opera-tions, helipads, air displays + absolutely anythingelse. (How about 'Treasure Hunt' comms?). Allcontributions will be acknowledged (finally).Contact: Mr P J Lee, 141 Manor Green Road,Epsom, Surrey KT19 8LW Short wave receiver Sony, Panasonic, Grundig,Trio, 'corn, etc, age and condition immaterial, cashor p/exchange hi-fi TV, VCR considered. Collec-tion arranged. Please phone (02302) 2438. Bedford FT75 manual or circuit diagram, borrow forcopying or purchase, all expenses paid. R FCashmore, 65 Michaelston Rd, CulverhouseCross, Cardiff CF5 4SX. Tel: 593057

II Does anyone know where I can obtain a brandnew AOR AR2001 scanner or who imports/distri-butes AOR equipment in Great Britain? If you do,telephone Brian on Dungannon (08687) 24029between 0930 and 1200 (Mon-Thur) or after 1830any evening Can anyone sell to an OAP or lend me a bulktape erazer to enable me to eraze a quantity of 7intapes? I would prefer to buy this. Please ring Bobany evening after 6pm on (0303) 76230 Taylor 31A scope, data and circuit. TelonicSM2000 sweeper units, L -7M S -4M SH-1M 3001,others considered. R C Taylor, Bwlch Glas,Penrhyndeudraeth, Gwynedd LL48 6RUMI Exchange DX160 receiver, general coverage,150kHz, 30MHz, in five bands, good cond. Will swapfor R216 FM, AM receiver or Eddyson 770R. quitewilling to pay carriage. Clive, 28 Kington Gardens,Chelmsley Wood, Birmingham B37 51 -IS. Tel: (021)788 8447 Information on SD200 computer, also softwareCP/M on 8in disk, anything. Wanted, grid computerwith manuals, disk drive. CP/M d'base I I on Bin diskwith manuals. Phone New Milton (0425) 616490 SSB CBs wanted dead or alive, in any condition,must be very reasonably priced. Write with detailsto S R Mohan, 75 Pennine Road, SK13 9ULIIII 2m FM for around £100, write with details to S RMohan, 75 Pennine Road, SK13 9UL Eddystone receivers wanted by collector, alsoany sales leaflets, catalogues and manuals. RingRichard Baker (021) 556 3324 Yaesu FT7B wanted in perfect order. Tel: (0283)221870 Output triodes and audio valves. Early hi-fi.Tannoy, Lowther. Voight, Vitavox, Western -Elec-tric, Quad, Decca. stereo Deccola, FFSS heads,Ortofon, SME arms. AEI, Altec Lancing, BTH,Garrard 301 turntables, Thorens TD124, etc. Alsocinema audio equipment. speakers, driver units,horns. Please contact John Baker, 57 Birkenhead

Street, London WC1H 8BB. Tel: 01-833-3008Practical Wireless, Radio Constructor, Ber-

nard's Short Wave Transistor Superhet 1968,Simple Short Wave Receivers, Simple RadioCircuits, Key Line books, Practical WirelessCircuits, 1968. Savage, 18 Bideford Close, Pic -north, Swindon, Wilts SN3 2LB FT707 or similar solid-state HF ORO rig, capable12V operation, for club use. Plus ATU 3.5-30MHz.Write Peter GOGTE, 48 Lincoln Road, Stevenage,Herts SG1 4PJ. Tel: (0438) 724991 or 350136 or352932 Want Racal 197 protection unit. Also anyone gota Pocom 2010 RTTY unit, any info on how it worksand does it work?! ie, is it as good as adverts say?Tel: Milton Keynes (0908) 313507 AC power unit for Codar AT5. Old Heathkit RA1Rxs. Details, condition, and price to RichardMarris, 35 Kingswood House, Farnham Road,Slough, Berks SL2 IDA Pye PF70s, will pay up to £20 ea (with powerpack). Also wanted, any min 2 way radios, to beused for radio comma training. Will pay up to £15.Mr S Clapson, Jubilee Day Care Centre, 49 SladeRoad, Portishead. Tel: (0272) 846484 Circuit diagrams and alignment procedures forPye Bantam high band FM - same required forGEC Kenilworth or Sinclair Comms 10 channel,and ERD Ottawa 4 channel AM 5W high band AMPMRs. Any info on conversion to FM would bemuch appreciated - circuit diagram for Sinclairmultimeter DM2 - all info, however brief will begreatly appreciated. M Cartwright G4TYK, 75Whites Road. Bitterne, Southampton SO2 7NR.Tel: (0703) 441345 British MK123 Tx- Rx. Must be complete with allaccessories and in good working order, withmanual. Also class D w'meter, pref 240V mains withmanual. Wanted by much hospitalised OAP. FrankGlynn, 41 Crossways Avenue, East Grinstead,Sussex. Tel: (0342) 22967

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 63

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JAPANESE Ic's (PART OF OUR RANGE)A5301 1350 AN1'40 L220 A''.45 C195 Ars7'46 f223 BA532 1,150134536(240 M41377 (220 MA1398E2 75 MA13001 02 95 LA4460E1 801.44481 (1 80 LA4507 £425 LC7137 C275 M51515 (250.M51517 £280ME13705 Et 80 M83712 Et 50 M83722E3 50 M837300250 MB3731 C350M93756 £260 MB8719 £385 STK461 (750 STK463 (8 40 TA7205AP£1 00 TA7222AP El 30 147229C3 25 TA7240 E2 95 TA7607 (2 95 TA7614£275 TA7628 02 95 147640 £175.UPC575 (1 00 UPC1001 (220UPC1031 (1 95 UPC1158 95p UPC1181 El 10 UPC1182 El 10 UPC1185£250 uPcitas C2 75 UPC1230 E2 50 UPC1277 E2 75 UPC1365 E3 60ADD Epp POS' AND PAC.KiN 'HFN ADD .5-- VAT TO TOTAL

T POWELL 16 PADDINGTON GREEN LONDON W2 ILOOPEN MON-FRI 10AM-5PM, SAT 9AM-1 2 NOON.

TELEPHONE: 01 723 9246CCESSNISA. TELEPHONE ORDERS ACCEPTED OVER (5.00

BEAM VIDEOThroughout the house on Channel 36

Price £10.50 - P&P 50p Phone for leafletElectronic Alailorder A

62 Bridge Street, RantsbottornLancs BLO 9AG

Tel: 070682.3036 (24hrs)

JAYCEE ELECTRONICS LTDJOHN GM3OPW

20 Woodside Way, Glenrothres,ivFife KY7 SDP

Tel: 0592 756962Open Tues-Sat 9-5

Quality secondhand equipment in stock Fullrange of TRIO goodies. Jaybeam - Microwave

Modules - LAR.

WORKSHOP SERVICE MANUALSANY MUSIC AUDIO. MONO TV - £4.50ANY COLOUR TV. AMATEUR RADIO - £9.50ANY VIDEO RECORDER. TEST - £19 50

STATE MAKE/MODEL/TYPE. PLUS 50p post.LSAE ENQUIRIES OTHERS PLUS FREE REVIEW

MAURITRON (REW), 8 CHERRY TREE ROAD,CHINNOR, OXFORDSHIRE 0X9 40Y.

FREE MEMBERSHIP to a new nationalelectronics club. For details and a freepack of components worth over £10 sendonly £1 p&p to Dept REW. Woodside.Dowsett Lane. Ramsden Heath. Billericay.Essex CM11 1JL

G4 DXXVideo Electronics

For Icorn, Dray, Wells. DAIWA. Datong N934 MHzequipment, logbooks.

rotators. cable. etc.

OPEN 9-5pm. Closed Wednesdays

141 Lancaster Road. Morecombe. Lancashire LA4 SOJ

Phone: (0524) 418873

MORSE CODE PREPARATIONCassette A 1-12 wpm for amateurCassette B 12-25 wpm for professional examination pr.p.r.t.o,Each cassette is type C90Price of each cassette (including booklets) C395Morse key with separate battery (PP3) - driven solid -Std:'oscillator and sound transducer produces clear tone for send^1practice Price of key with electronic unit Et 95

Price includes postage etc only14111 ,IN.IW011 (NW

12 Lorooltoro Wm, Milton, PeatarrwWh PO4 BLS

THE SCIENTIFIC WIRE COMPANY811 Forest Road, London E17. Telephone 01.531 1568

ENAMELLED COPPER WIRESWG 1113 Box 4o1 2oe

8 to 34 363 209 1 '0 08835 to 39 382 2 31 1 27 09340 to 43 600 320 225 1.6144 t047 867 580 349 27548 15 96 958 638 3 69

SILVER PLATED COPPER WIRE14 to 30 909 520 2 93 1 97

TINNED COPPER WIRE14 to 30 397 241 139 094FluxcOreSolder 590 325 182 094

Please add 15% VAT Orders under £2 add 20pSAE for list of copper and resistance wire

Dealer enquiries welcome

SelectronicThe UK s leading suppliers of934MHz personal radio equipment

203 High StreetCanvey Island, Essex,

Tel: 0268 691481(Open Mon -Sat 9-5.30)

Amateur radio equipment also in stock

D & D ELECTRONICS(Kennington}

The sort of shop you used to see inLisle St. All sorts of surplus supplies. so come

along and browse or sendSAE for info. sheets.

3a Braganza Street, London SE17 3RDTel: 01-793 0054 (Open 6 days a week)

ALL THE SUPERBARGAINS AREON THEINSIDE -FRONTCOVER OF THISMAGAZINE!!

Service Sheets from E2.50/Isae ctvimus-c/combisE3.50/1sae. Sae Newnes & TV Technic books instock. Thousands service & repair manuals.

SAE Free rev,ew/Pricelists.T1S (REW) 78 Church Street, Larkhall,

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64 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

Telephonethe advertisingdepartment on:0277 219876for details

RF DEVICES AT ROCKBOTTOM PRICES!

Nobody beats us!Over 30,000 RE devices at low prices

REPLACEMENT RF TRANSISTORSMRF454 HF/SSB 80WMFR450 HF/SSB 50WMRF238 VHF/FM 25WMRF475 HF/SSB 20W2SC1969 HF/SSB 18W2SC2043/1307 HF 16W2SC1947 VHF 3.5W2SC1946A VHF 32WBLW 6OR HF/VHF 50W (Special)

£20.00£11.60£12.80£2 99£2.50£2.00£7.60

£14.30£7.50

REPLACEMENT RF POWERMODULES

M57704/SAU3 UHF 15W £36.00M57712/37 VHF/FM 25WM57713/SAV8 VHF/SSB 15W £39.00M57718/SAU4 UHF/SSB 15W £49.00M57719 VHF/PMR 15W £29.00M57727 VHF/SSB 38W £45.00M57749/SAU11 934/FM 7W £29.00

Send £1.00 p&p or SAE for full listAll prices inc. VAT

Many Ic's and other types in stock

RAYCOM LTDDEPT AR 584 HAGLEY RD WEST

QUINTON BIRMINGHAMB68 OBS

021 421 8201-3= (24hr answer phone) En

ETESON ELECTRONICS15B Lower Green,

Poulton-le-Fylde, BlackpoolTel: /0253) 885107

Open 9 30am - 12.30. 1.30 - 5.30 Closed Wed & SunElectronic Component Specialists

A wide range of electronic components. ICs. capacitors,transistors. resistors. plugs and sockets etc

NEXT ISSUEON SALE

10th SEPT1987

['Manufacturers, importers and suppliers of world famous communication products584 HAGLEY ROAD WEST OLDBURY, WARLEY, BIRMINGHAM B68 OBS021-421 8201/2/3. CELLNET 0860 323056. PRESTEL MBX 214218216 FAX 0215614074Amateur Radio. Business Radio, Radio Telephones, Sales, Service Accessories and antenna systems.

R. WITHERS COMMUNICATIONS LTD

olcom YAESU c'Y THE TECHNICALLY ORIENTATEDRADIO COMMUNICATION

RADIO SERVICE ENGINEERS\ SPECIALIST

28 000-215,000 per annumplus expenses

Ray Withers Communications Ltd. based near Birmingham are a small. but very dynamic marketing lead company. Due toincreasing business we are urgently seeking service engineers for field work and bench servicing on the latest portable. mobileand based transceivers often employing CTCSS tone squelch. as well as general Amateur Radio equipment servicing.

Do you have the flexibility and skill required for this well paid position' Practical ability would be even more important thanformal qualifications. if for instance you are a radio amateur who can, with confidence, build and repair your own equipment, youcould be ideal,

A basic knowledge of radio is essential. and a practical test may be given If you want to improve your career prospects. thencome and show us what you can 00'

We are conveniently situated close to Junction 3. M5. We use modern test equipment end work in a small friendly environment,with a team of talented people

Please send a written application or call Ray Withers personally. on the above telephone numb,

WE OFFER YOU THE CHANCE TO GROW WITH AN EXPANDING COMPANY, PROVIDING BUSINESSAND AMATEUR RADIO ENTHUSIASTS WITH TOMORROW'S RADIO TECHNOLOGY TODAY ..

G.W.M RADIO LTD40/42 Portland Road, Worthing,

Sussex. Tel: 0903 34897Constantly changing stock of

interesting items for callers. Receivers,Marconi Apollo £250. Racal RA17 £200

for callers. Datel 2412 modem units 2/TG2507-8 modules 1, 2 & 3 in modern caseassembly £30 inc p&p. Other telephone

parts in stock. Ex -navy quartzchronometers clear 7cm dial in wood

case £27 inc p&p.

TURN YOUR SURPLUSICs TRANSISTORS etc, into cash, immediatesettlement. We also welcome the opportunity

to quote for complete factory clearance.CONTACT:

COLES-HARDING & CO103 South Brink, Wisbech, Cambs

TEL: 0945 584188Est Over 10 years

AGRIMOTORSMERTON CB AND RADIO CENTRE

MERTON GARAGE AND POST OFFICE, MERTON.Nr OAKHAMPTON, DEVON EX20 3DZ

OPEN 6 DAYS 9-6 LUNCH 1-2pmEARLY CLOSING THURSDAY 1.00pm

(SUNDAYS BY APPOINTMENT)SPECIALIST IN 934 MHz

SUPPLIERS OF ALL 27MHz AND 934 MHz EQUIPMENTAMATEUR ACCESSORIES CATERED FCR

08053 200

Radiotelephones, Terminal Units, TestEquipment, Ex -RAF Radar andInstruments.Forward DO PO ,Retundable on first purchase for list')Address to

Brent Electronics 8 Comma49 Seaview Street, CleethorpesSouth Humberside DN35 8EUTel: 0472 890383

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TO: Radio & Electronics World Sovereign House Brentwood EssexCM 1 4 4SE England (0277) 219876

print your copy here

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SEPTEMBER 1987 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement 65

ADVERTISERS INDEXAerial Techniques 56AKD 39

J Bull 67

P M Components 6, 7

Display Electronics 52,53

Electronics & ComputerWorkshop 37

Grosvenor Software 20

lcom 16, 17

Keytronics 21

Matmos-Computer App 59

Brian Reed 48

Service Trading 48Sherwood Data 44Smith Elect 20SpecialistSemi -conductors 68C R Supply 56

Western Electronics 51

Stan Wi I lets 51

R Withers 2

Xen Electronics 15

Radio&.tiecrronics ADVERTISING RATES & INFORMATION

m. communleanota and crlacionks magazine World

DISPLAYAD RATES series rates for consecutive insertions

depth mm a width mm ad apace I issue 3 Issues 6 Issues 12 issues61 x 90 '5page128 x 90 or 61 x 186 ' 4 page128 x 186 or 263 x 90 ' '2 page263 x 186 1 page263 x 394 double page

£91 00£160 00£305 00£590.00

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SPECIAL POSITIONSCovers Out ide back cover 20% extra. inside covers 10% extraBleed 10% extra (Bleed area - 307 x 220)Facing Matter 15% extra

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Issue colour & mono proof ad mono no proof and small ad mono artwork on vale ChunSept 87 16Jul El 7 22Jul 87 24Jul 87 13 Aug 87Oct 87 13 Aug 87 19 Aug 87 21 Aug 87...... 10Sept 87Nov87 10 Sep 87 16 Sep 87 18 Sep 87 8 Oct 87Dec 87 15 Oct 87 21 Oct 87 23 Oct 87 12 Nov 87

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li series are contract is cancelled the advertiserwill be liable to pay the unearned seres discountalready taken

COPYExcept for County Guides copy may be changedmonthlyNo additional charges for typesetting or illustra-tions ((weep' for colour Separation')For illustrations Just send photograph or artworkColour Ad rates do not include the cost ofseparations

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FOR FIMINIR INFORMATION CONTACT available on requestRadio S Electronics World Sovereign House Brentwood Essex Curd 4SE102771 219816

66 please mention RADIO & ELECTRONICS WORLD when replying to any advertisement SEPTEMBER 1987

£1 BAKERS DOZEN PACKSPrice per pack is £1.00.' Order 12 youmay choose another free. Itemsmarked (sh) are not new butguaranteed ok

1. 5 - 13 amp ring main !unction boxes2. 5 - 13 amp ring main spur boxes4. 5 - surface mounting5. 3 - electrical switches, white flush mounting7. 4 - m flex line switches with neons9. 2 - mains transformers with 6V 1A secondaries10. 2 - mains transformers with I 2V A secondaries11. 1 - extension speaker cabinet for 6 speaker13 12 - glass reed switches17. 2 - ultrasonic transmitters receivers with circuit19. 2 - light dependent resistors25. 4 - wafer switches - 6p 2 way, 4p 3 way. 2p 6 way, 2p 5 way. 1p

12 way small one hold fixing and good length spindle your choice28. 1 - 6 digit counter mains voltage30. 2 - Nicad battery chargers31. 1 - key switch with key33. 2 - aerosol cans of ICI Dry Lubricant34. 96 - 1 metre lengths colour -coded connecting wire39 1 - long and medium wave tuner kit41. 8 - rocker switch 10 amp mains SPST45. 1 - 24 hour time switch mains operated Is h.)49. 10 - neon valves - make good night lights50. 2 - 120 DC or 24V AC, 3 CO relays51. 1 - 12V 2 CO miniature relay very sensitive52. 1 - 12V 4 CO miniature relay54 10 - rows of 32 gold plated IC sockets (total 320 sockets)55 1 - locking mechanism with 2 keys56 1 - miniature uniselector with circuit for electric jigsaw puzzle60. 5 - ferrite rods 4" x 5/16" diameter aerials61. 4 - ferrite slab aerials with L & M wave coils63. 1 - Mullard thyristor trigger module66. 1 - magnetic brake - stops rotation instantly67. 1 - low pressure 3 level switch can be mouth operated69. 2 - 25 watt pots 8 ohm70. 2 - 25 watt pots 1000 ohm71. 4 - wire wound pots - 18, 33, 50 and 100 ohm your choice77. I - time reminder adjustable 1-60 mins clockwork85. 1 - mains shaded pole motor 1" stack - a shah89 1 - mains motor with gear box 1 rev per 24 hours91. 2 - mains motors with gear box 16 rpm96. 1 - thermostat for fridge98. 1 - motorised stud switch Is. h.)101. 1 - 2j hours delay switch103. 1 - mains power supply unit - 6V DC104. 1 - mains power supply unit - 4 V DC107. 1 - 5- speaker size radio cabinet with handle112. 1 - heating pad 200 watts mains114. 1 - 1W amplifier Mullard 1172115. 1 - wall mounting thermostat 24V118. 1 - teak effect extension 5" speaker cabinet120. 2 - p c boards with 2 amp full wave and 17 other recs121. 4 - push push switches for table lamps etc122. 10 - mtrs twin screened flex white p. v. c outer124. 25 - clear plastic lenses 1; diameter127. 4 - pilot bulb lamp metal clip on type128. 10 - very fine drills for pcbs etc129. 4 - extra thin screw drivers for instruments132. 2 - plastic boxes with windows, ideal for interrupted beam switch134. 10 - model aircraft motor - require no on/off switch, lust spin to

start137. 1 - 6; " 4 ohm 10 watt speaker142. 10 - 4 BA spanners 1 end open, other end closed145. 2 - 4 reed relay kits 3V coil normally open or c/o if magnets added146. 20 - pilot bulbs 6 5V 3A Philips154. 1 m 12V drip proof relay - ideal for car lobs155. 3 - varicap push button tuners with knobs169 4 - short wave air spaced trimmers 2-30f172 10 - 12V 6W bulbs Philips m e s178 3 - oblong amber indicators with lilhputs 12V180 6 - round amber indicators with neons 240V181 100 -pvc grommets yl hole size182 1 - short wave tuning condenser 50 pf with i" spindle184 1 - three gang tuning condenser each section 500 pf with trimmers

and good length :"spindle188 1 - plastic box sloping metal front, 16 x 95mm average depth

45mm193. 6 - 5 amp 3 pin flush sockets brown195. 5 -B.C.lampholders brown bakelite threaded entry196. 1 - in flex simmerstat for electric blanket soldering iron etc197. 2 - thermostats, spindle setting - adjustable range for ovens etc199. 1 - mains operated solenoid with plunger 1" travel200. 1 - 10 digit switch pad for telephones etc201. 8 - computer keyboard switches with knobs, pcb or vero mounting206. 20 - mtres 80 ohm, standard type co -ax off white211. 1 - electric clock mains driven, always right time - not cased216. 1 - stereo pre -amp Mullard EP9001232. 2 - 12V solenoids. small with plunger236. 1 - mains transformer 9V 1 amp secondary C core construction241. 1 - car door speaker (very flat) " 15 ohm made for Radiomobile241. 2 - speakers 6" x 4" 4 ohm 5 watt made for Radiomobile243. 2 - speakers 6" x 4" 16 ohm 5 watt made for Radiomobile244. 1 - mains motor with gear -box very small, toothed output 1 rpm245. 4 - standard size pots, j meg with dp switch249. 1 - 13A switched socket on double plate with fused spur266. 2 - mains transformers 91/ L A secondary267. 1 - mains transformers 151 IA secondary p c b mounting291. 1 ten turns 3 watt pot spindle 100 ohm296 3 car cigar lighter socket plugs298 2 15 amp round pin plugs brown bakelite300. 1 mains solenoid with plunger compact type301. 10 ceramic magnets Mullard 1" x 3/8 x 5/16303. 1 12 pole 3 way ceramic wave charge switch305. 1 tubular dynamic microphone with desk rest308. 1 T.V turret tuner (black & white T V I310. 2 oven thermostats313. 5 sub miniature micro switches316. 1 round pin kettle plug with moulded on lead453. 2 - 2 in 80ohm loudspeakers454. 2 - 2 in Bohm loudspeakers463. 1 - mains operated relay with 2 sets cro contacts464. 2 - packets resin filler/sealer with cures465. 3 - 5A round 3 pin plugs will fit item 193468. 4- 7 segment I e d displays470. 4 - pc boards for stripping, lots of valuable parts473. 1 - 5" 4ohm speaker with built in tweeter Radio mobil480. 1 - 3A double pole magnetic trip, saves repairing fuses498. 4 - 1000uf 25V axial electrolytic capacitors

3" DISCS For our £27.50 F.0 D -Amstrad 664,Einstein, etc, pack of 10 £25, ref 25P3 or sample £3, ref.3P24.

COMPACT FLOPPY DISC DRIVE For Only(27.50

As used in the Amstrad 664/6128, the Einstein and otherpopular computers. Drives the new standard disc, only 3"but with a capacity of 500k per disc, this is equivalent tothe 51- disc. Other features are:1. It has the shugart compatible interface (34 way edge

connector).2. It is plug compatible with the 51" disc, the recording

method, data transfer rate and rotation speed are thesame as 51".

3. Is fitted with long life brushless motor and uses steelband driving for reliability and assessing at 3mS.

4. Its touch loading mechanism makes easy handling anddisc slot protects against dust.

5. The back of the disc in use can be seen, and up to fourdrives may be daisy chained.

We include the operator's manual and other informationshowing how to use this with popular computers BBC,Spectrum, Amstrad etc. Brand new and at only £27.50including post and VAT.Data available separately £2, refundable if you purchasethe drive.

Ea -Electricity BoardGuaranteed 12 months

VENNER TIME SWITCHMains operated with 20 amp switch, oneon and one off per 24 hrs repeats dailyautomatically correcting for thelengthening or shortening day Anexpensive time switch but you can have itfor only E2.95 without case, metal case- £2.95. adaptor kit to convert this intoa normal 24hr time switch but with theadded advantage of up to 12 on/offs per24hrs This makes an ideal controller forthe immersion heater. Price of adaptor kitis E2.30.

SOUND TO LIGHT UNIT

Complete kit of parts of a three channei sound to iight unitcontrolling over 2000 watts of lighting Use this at home if youwish but it is plenty rugged enough for disco work The unit ishoused in an attractive two tone metal case and has controls foreach channel, and a master on/off. The audio input and output areby ;" sockets and three panel mounting fuse holders providethyristor protection A four pin plug and socket facilitate ease ofconnecting lamps Special price is £14.95 in kit form

NEW ITEMSSome of the many described in our current list which you will receive with your parcel

RE -WIRING?Beres a bargain for you -MEM 3 rncuit soldier 454 switch with 3x154 rewirablefuses normal cost over CIO, but yours for only C5 Our let 5P100

AUTO TRANSFORMER BARGAIN200W 230,115V encapsulated into a very neat met size 4x4,,1 apex Only E3, piusC2 post our ref 3P22

HOW ARE YOU GOING TO KEEP YOURCHILDREN OUT OF MISCHIEF THISSUMMER?Why not buy them a computer. they can have tun and be learning at the same time Wehave a real bargain the 'Acorn Electron" it comes complete with mains adapter. TV lead.starter cassette and Iwo handbooks The only extra you need is a cassette recorder Itsideal lot all the family and Dad while the kids are not playing their games on it you caneven do some of your office work with it This computer as its 300 page handbookshows can do most things that the BBC computer can do but will only cost you ahactron of the price only f 39 50 plus f 2 post

SOFTWARETo go with the Acorn CI each or 5 for 04 00Desk Diary Hoppe!Business Games Sphinx AdventureStatship command ArcadiansChess Boxer

Snapper

9" VDUIdeal to work with computers or video cameras uses Philips black and white tube refM24/ 306W Which tube is mplosron and X.ray radiation protected VDU is brand newand has time bases and EHT circuity. requires only a 16V d c supply to set it going Itsmade up el a lacquered metal frame work but has open pries so should be cased nil youare handy with a dull and file you could make a case out of two of our 61 speakercabinets) The VOU comes complete with circuit diagram and has been line tested andhas our six months guarantee Offered at a lot less than some firms are asking for thetube alone only (16 plus C3 post We also have some that faded the line test againbrand new but altered without guarantee at Ell plus E3 post

IONISER KITRefresh your home. office. shop, work room. etc. with anegative ION generator. Makes you feel better and workharder -a complete mains operated kit which weguarantee is ten times more powerful than other popularkits. Price includes case and instructions. E9.50 plusE2.00 post.

TELEPHONE BITSMaster socket (has surge arrestor - ringing condenser etc) andtakes B.T. plug E3.95Extension socket 02.95Dual adaptors 12 from one socket) C3.95Cord terminating with B.T. plug 3 metres C2.95Kit for convening old entry terminal box to new B.T. master socket,complete with 4 core cable, cable clips and 2 BT extensionsockets E11.50100 mtrs 4 core telephone cable C8.50

J & N BULL ELECTRICALDept. R.E., 250 PORTLAND ROAD, HOVE,

BRIGHTON, SUSSEX BN3 5QTMAIL ORDER TERMS: Cash, P.O. or cheque with order Ordersunder E20 add El service charge Monthly account orders acceptedfrom schools and public companies Access & 8/card ordersaccepted Brighton 0273 734 648 Bulk orders: write for quote

£2 POUNDERS*2P2 -Wall mounting thermostat, high precision with mercury switch and

thermometer2P3 -Variable and reversible 8.12v psu for model control2P4 -24 volt psu with separate channels for stereo made for Mullard UNILEX2P6 -100W mains to 115V auto -transformer with voltage tappings2P8 -Mains motor with gear box and variable speed selector Series wound so

suitable for further speed control2P9 -Time and set switch Boxed, glass fronted and with knobs Controls up to

15 amps Ideal to program electric heaters2P10 -12 volt 5 amp mains transformer2P12 -Disk or Tape precision motor - has balanced rotor and is reversible 230v

mains operated 1500 rpm2P14 -Mug Stop kit - when thrown emits piercing squawk2P15 -Interrupted Beam kit for burglar alarms, counters. etc2P17 -2 rev pr minute mains driven motor, ideal to operate mirror ball2P18 -Liquid/gas shut off valve mains solenoid operated2P19 -Disco switch.motor drives 6 or more 10 amp change over micro switches

supplied ready for mains operation2P20 -20 metres extension lead, 2 core - ideal most Black and Decker garden

tools etc2P21 -10 watt amplifier, Mullard module reference 11732P22 -Motor driven switch 20 secs on or off after push2P26 -Counter resettable mains operated 3 digit2P27 -Goodmans Speaker 6 inch round Bohm 12 watt2P28 Pump - always useful couples to any make portable drill2P31 -4 metres 98 way interconnecting wire easy to strip2P32 -Hot Wire amp meter - 4; round surface mounting 0-10A - old but

working and definitely a bit of history2P34 -Solenoid Air Valve mains operated2P38 -200 11 P M Geared Mains Motor 1" stack quite powerful, definitely large

enough to drive a rotating aerial or a tumbler for polishing stones etc2P43 -Small type blower or extractor fan, motor inset so very compact, 23002P46 -Our famous drill control kit complete and with prepared case2P49 -Fire Alarm break glass switch in heavy cast case2P51 -Stereo amplifier, 3w per channel2P55 -Mains motor, extra powerful has 1 j " stack and good length of spindle2P62 -1 pair Goodmans 15 ohm speakers for Unilox2P64 -1 five bladed fen 6j" with mains motor2P66 -1 2Kw tangential heater 115v easily convertible for 230V2P67 -1 12v -0-12v 2 amp mains transformer2P68 -1 15v -0-15v 2 amp mains transformer2P69 -1 250v -0-250v 60 mA & 86 3v 5A mains transformer * 50p post2P70 -1 M.I. tape motor two speed and reversible2P12 -1 115v Muffin fan 4" x 4" approx Is h )

2P75 -1 2 hour timer. plugs into 13A socket2P82 -9v-0-9v 2 amp mains transformer2P84 -Modem board with press keys for telephone rethaller2P85 -20v-0-20v A Mains transformer2P88 -Sangamo 24 hr time switch 20 amp Is h2P89 -120 min time switch with knob2P90 -90 min time switch with edgewise engraved controller2P97 -mains transformer 24V 2A upright mounting2P98 -20m 4 core telephone cable, white outer2P99 -500 hardened pin type staples for telephone cable2P101 - 15V mains transformer 4A upright mounting2P105 -capillary type thermostat for an temperature with c/o switch2P108 -mains motor with gear box giving I I 0rpm2P109 -5" wide black adhesive pvc tape 33m. add f1 post if not collecting

OVER 400 GIFTSYOU CAN CHOOSE FROM

There is a total of over 400 packs inour Baker's dozen range and youbecome entitled to a free gift with eachdozen packs.

A classified list of these packs andour latest "News Letter" will be enclosed with yourgoods, and you will automatically receive our nextnews letter.

£4 POUNDERS"4P9 Ace Prestel Unit new but less most ICs Contains useful Modem Add El

post

4P14 Mains transformer uptight mounting 43V 3 4V output. add £2 post4P15 Motor with gearbox final speed 60rpm very powerful would operate gate

etc4P11 Uniselector 3 pole 25 way as used on automatic telephone exchange etc

£5 POUNDERS`5P1 12 volt submersible pump complete with a tap and switch, an ideal

caravan unitP2 Sound to light kit complete in case suitable for up to 750 wattsP6 12V alarm bell with heavy 6" gong. suitable for outside if protected from

direct rainfall Ex GPO but in perfect orderP12 Equipment cooling fan - mini snail type mains operated

5P15 -Uniselector 4 pole, 25 way 50 volt coilP18 -motor driven water pump as fitted to many washing machines

5P20 -2 kits, matchbox sue, surveilance transmitter and FM receiver5P23 -miniature lam 2 wide) tangential blow heater. 1-2kw5P24 - hp motor. ex computer. 230V, mains operation 145Orpm If not collect

add £3 post5P25 -special effects lighting switch Up to 6 channels of lamps can be on or off

for varying time periodsP41 -5" extractor fan, very quiet runner Is h I, gold 12 mths

5P48 -telephone extension bell in black case ex -GPOP52 -mains transformer 26V 10A upright mounting. add E2 post

5P54 -mains motor with gear box, final speed 5rpm5P58 -Amstrad stereo tuner FM and IN AM

P62 -21 kw tangential blow heater, add El 50 post if not collectingP73C high pressure mains operated gas Of water valve with tube connection

sortable solderingP82 1 25rpm mains 60w muter with gearbox

5P84 1 delay time switch, adjust 0-20 seconds5P69 1 light box size 14" x 12" for circuit tracing pcb s Add f 3 for postage

and packingP81 1 stepper motor bi-directional, 7 5' steps 12-I40 cod

5P88 1 24V 5A mains transformer in waterproof case, ideal for gardenbighting, pond pump etc. Add f2 post

P90 18" tangential blower with mains motor5P91 14" tangential blower with mains motor in centre

P92 10 metres twin screened computer co ax5P93 6" alarm bell 24 volt d c on 50V a c5P94 Current transformer 1 amp thro primary -1405P95 Photo magic -original 'vintage. photo cell

LIGHT CHASER KIT motor driven switchbank with connection diagram, used inconnection with 4 sets of xmas lightsmakes a very eye catching display forhome, shop or disco, only £5 ref 5P56.

BIO-FEEDBAGACCESSORIE

A METERMOVEMENTwhich can be bud?into your bio- feedback monitor10 make it a completelyself-contained instrumentDon I worry if you we already drthe terminal holes - the meter

SENSITIVE METER MOVEMONLY £1.90. VAT

SPARE ELECTRODESAND GEL

5 sets of electrodes 110 electraand a sachet of conductive gelall for £ 2.90 , VAT

TACHOMETEDWELL METFEATURED IN E'JANUARY 1987

:K LEDsni

RECTANGULARLEDs

Greenrectangular LEDsfor bar -graphdisplays50 for £3 50 100 for f6 .,500 for £25 MO for £45

DIGITAL AND AUDIO IEQUIPMENT LEDs

Assorted 3mm LEDs red, green yellow andorange 25 of each t 100 LEDs) for £6.80 . VAT

BIO-FEEDBACK HI-FI POWERMETERFEATURED IN ETI / Alliffi

S.111.111,

FEATURED IN ETI 411..,DECEMBER 1986 . , ,L

A complete pans set for theETI biofeedback monitorIncludinginuding meter Originallyoffered from limited stocksat £14 55 (without meter?.powerthis sensitive GSR monitorhas proved so popular that r

we have decided to makeit a permanent feature of our catalogue

The complete pans set includes case PGB allcomponents leads electrodes gel meter andVI instructions

BIOFEEDBACK PARTS SET ONLY

MAY1987Measure the outputpower of yourhi-tij.,with the ETI

meter The meterscan be back -lit for effectthe scale and power legend will glow green tocontrast with the red pointer Two switchedranges give readings of 0-10W and 0.100W

The parts set consists of metermovement. PCB all componentsrange switch and full

MONO POWER METERPARTS SET £3,90. VAT

STEREO POWER METERPARTS SET £7.20 . VAT

,

/-7 -7

'a..(-7.-'

diedall cover them up'

NT

le pads(

£11.50. VAT SUITABLE CASE £7.50 . VAT

R AND BRAIN WAVEMATCHBOX K2 csER Aw AMPLIFIER MONITOR_

FEATURED IN ETIAPRIL 1986 lei/ . /711

... ileNu ordinary amOlitets

FEATURED IN ETIAUGUST 1987 IW-- these When our first 1-tcustomers 1001, an ,I, a,rALPHA HOW TO SUCCEED WITHOUTREALLY TRYING

. PPP interest it kvas for thediminutive siSe !both KNIGHT RAIDER .11, was the title of a recent OE D television program Cr

sty.. 410,45 lite can be dramatically improved with aid,Opha training Alisdair Mc Beth overcame his shyness A

modules will fit Inamatchbox', the total disregard tor pow, supplies andspeaker impedances and the impressive power output FEATURED IN ETI. JULY 1987 ,tins others became more confident improved their

. VAT, (Previouslyle parts set includes

horn these little amptiters When they re ordered 'I wasldr the sound quality

Two amplifier modules were described both based onThe , i , .. , erects ior r.:cy, yamborgmn Maser. EP,.

ia plot powenu: igm.

sporting abilities learned M cope with stress and allwithout really trying,

OMpOnents plug the powerloill6SV C The single C version will deliverdayneryard centre! boy a. a poen or sght mores laely Iron. ill lc

4:40,4 monitors are net new but good ones are hard to4 «o To detect a lees us/ of brain waves in the midst ofclips meter and over 20 Watts reln a suitable speaker and power soppy

The bridge version can provde up to SOW' Although thespecified supply aria and speaker impedance must be

nom wavind ,ornet s tar behind Clip the sworn agAn and thepant of horn becomes a bar bounce, beckedeCts and forwards

press again and try one cd me other sr patterns,,,,..,,,,:;:on

noise that's lens of thousands of times as great IS noteasy, The ETI Alpha Monitor is probably the rhOst pOwe

used to achieve maximum power both moo:lutes are guilenappy 10 work from any voltage between 12V and 32V and

r7t, a.,e-con,ro, boy lets , . who, tee e,a,e ,,,,are 004.

and effective design to be found outside an EEGlaboratory The sensitive circuil locks on to Me all impon

will accOrmnodate any type of speaker The bridge version The angle Rader can be ...to any car id makes an mice., lug alpha rythm and helps you to strengthen and Control it

METER is ideal for giving a boost lo car Hi Fi systems driving two4 Ohm speakers in parallel on each channel fo, best effect

Both deSagner approved parts sets consist Of a roller

i,ntri or wen low powered bulbs it can turn any child s pedal car crbcycle.10 a spectacular TV age toy'The coned box parts set consists of case switches l E Ds PCB

Quickly Then you put it to work for you strengtheningyour confidence and abilitreS day by day

0 i VAT tinned printed circult board and all components The comrenents hardware and nstrucnons The sequence boardincludes PCB ICs pave* FE Ts ccmoonents hardware and

Our approved partS Set consists of EEG (tectrodes andheadband case two PCBs screening box top qualityL165V Cs are also available individuaIN with a tree mini ing,rtions PMI amplifiers all and full instructionSdata sheet giving specilicatrons and suggested circuits KNIGHT RAIDER CONTROL BOX ONLY

componentsincluding training exerCiSeS1 Assembly time is about In

',WA. E is MAI, He ), Bhipc.EMant ir 4 R ,y, 45104at 0 0 el SF' £6.90 VAT, to six hours

KNIGHT RAIDER SEQUENCE BOARD ONLY ALPHA MONITOR PARTS SET ONLYire exhausted £6,50. VAT £8.90. VAT £3.90. VAT £11.90 . VAT, £29.90 . VAT'

Last few to clear at only £9.50 .offered at E16 40 I The complecase. printed circuit board. all csocket switches test leads anr

lull instructions

TACHOMETER AND DWELLPARTS SET ONLY £9.5

Offer applies only until stocks

rchitith

dui

ant

Complete Parts Sets for ETI ProjectsMAINSCONDITIONERFEATURED IN ETI.SEPTEMBER 1986It is astonishing how manypeople buy or build lop -flightIsli equipment and thenconnect it to a noisy spikyMains supply Ratherlike buying a Ferrari andtrying to run it on paraffin you might think Expectingcrystal clear sound the poor music enthusiast endsup with a muddy contused mush, and feels thathe haS somehow been cheated Is this 1,10My music centre sounded NV as good'

The domestic mains supply is riddled withRF interference noise Transient spikes andgoodness knows what else Computers crashradios pop and crackle tape recordings are spoiledand hi-fi soundS not quite right Why put up withit when the solution iS SO simile' The ETI mainsconditioner is the lowest cost upgrade you will everbuy and probably he most effective,

Our approved parts set consists of PCB. ancomponents torcad* enamelled wire fixing lieslast response VDR' and full instructionsETI MAINS CONDITIONER PARTS SET

ONLY £4.60! . VAT'Note: the toroid and VDR supplied are superiorto the types specified in the article

PROJECT BOXPROJECT CASEWITH PP3 BATTERYCOMPARTMENT

ONLY £2.60! VAT

CASINO PARTSSET ONLY£5.90! . VAT

CREDIT CARDCASINO i r '7,3e'N7

tii toilFEATURED IN ETI.MARCH 1987

This wicked little pocketgambling machinemeasures only3 x2 x1 .- It will play allkinds of casino gamesincluding

Roulette Craps PontoonOur approved parts set comes completewith case self-adhesive fascia. tinnedand drilled printed circuit boardall components. hardware. fullinstructions and three differentgames to play'

Fiveextra

FREE gatheSWith ev.

°rder yaws.

LM2917

EXPERIMENTER SETdetailed ,nstruCtiOnS with data and circuits for eightdiner°. Protects to build Can be used to eypermentwith the Circuits in the Neat Great Lime IC leatureCET' December 19861

LM2917 Experimenter Set C5.80 VAT

Prices shown are exclusive of VAT, so pleaseadd 15°n to the order total UK postage is 60pon any order Carnage and insurance foroverseas orders f 1 50 Please allow up to14 days for delivery

igeAllipetr.!

WI

MAINSCONTROLLERFEATURED IN ETIJANUARY 1987

Have you ever wondered *Oatpeople au will, all those combo.,interlaces, Put your computerin control say the ads TheSpeclrabeeb has eight TItCO.. What on earth Canyou control with a TIL ChM,A torch bulb'

the E TIMains Controller a a jog. t,.,44,4445 /441eoatMuch Mows y0.10 COA004404105 041.4010 500W from yourcomputer or bgic circuits An opto COW.; gives isotatqn eial least 2 500V so the centre:41er can be connected toesdeerneetal circuits computer, and Control Prefects 'complete safely Folio. your computer interface tom leiconed', and you re really in busness Win automat,cone,

The mains controller connects directly to most 111far,ies without external components and can be driven byCMOS with he addition of a transistor and two resistersi Supplied

Your mans contr.°, pans sal Contains high Quality idle'tinned PCB MOC3021 optpcoupler power mac witnheatsink mounting hardware and heatsinS compound allcomponents inducting 5.00pr .:04nponen45 5.0 5.,014.4o0u0/ Ye loads transosror and 045451044, 10, CMOS oteetoey

,nseuctio,

MAINS CONTROLLER PARTSSET £6.20. VAT'

RUGGEDPLASTIC CASE

and mains controller

ONLY £1.65 . VAT

D VC

POWERFUL AIRIONISERFEATURED IN ETI.JULY 1986

its have been describedas vitamins of the air bythe health magazinesand nave been creditedwith everything fromuring hay fever andSthma to improving COnCentralqn and coning an end

lo Insomnia Although some of the claims may be«xaggerated Mere is no doubt that poised air is much/ 1..4 and purer and seems much more invigoratingthan dead air

The DIRECT ION ioniser caused a great deal ill.cilemen, when appeared as a constructional protc,1..

ETI At last an ioniser that was comparable with.oener than-lt commercial products was retiabie goodto build and Ion' Apart irom Inc serious applicationssome of Inc suggested experiments were outrageous'

We can supply a matched set of parts tallyApproved by Me designTinnedild Mrs unique protectThe sel inctudes a rolleprinted cirCuil boardh6 components case mains lead and even the partsfor the tester According to one CuStorner Me set costsabout a third of the price at the individual ComponentsWhat more can we say'

DIRECT IONInstructions arenutrdea PARTS SET £9.50. VAT

Our best setting ioniser kir Isnow available with an eiegant while case

WHITE IONISERPARTS SET ONLY C9.80! . VAT

FOUNDERS HOUSEREDBROOKMONMOUTH

LIMITED GWENT