UK £1.50IR £2.20
(incl. VAT)
MMICS REVOLUTIONIZE WIDEBANDRF AMPLIFIER DESIGN
DCF77 Receiver and Frequency StandardPortrait ol Sir Clive SinclairEuropean Education Software
01
9 770268 451012
111 EE
January 1988
BBC Micro Computer SystemBBC MASTER SERIES:Ah1B15 BBC MASTER 128K E380ADCO6 Turbo (65C102) Card 199ADC08 512 Processor E189ADF14 Rom Cartridge ... £12.75ADF10 Econet Card £41ADJ22 Ref. Manual I £14ADJ23 Ref. Manual Part 11 . £14ADJ24 Adv Ref Manual £18
(a)(dl
(dl(dl(c)(c)(c)
BBC ARCHIMEDESPlease enquire about avaAaty anddetails of the stem.
UPGRADE KITS:1_2 OS ROM E15DNFS ROM E17.50BASIC II ROM (BBC £22.50ADFS ROM £261770 DES Kit £43.50Econet Kit (B&B+l £55
(dl(dl(d)(dl(dlId)
ACORN ADD-ON PRODUCTS:Torch ZEP 100 E229 (a)512 2nd Processor £195 IblIEEE Interface £265 Ib)Teletext Adapter (95 lb)Acorn 65CO2 Turbo E99 lb)
Ask for (IA details on our full range. of software
WORD PROCESSOR ROMs:VIEW 2.1 £35 (d) VIEW 3.0 £48 (e)Seel/master E49 (dl VIEW INDEX £12 (dlWORDWISE E24 (dl WORDWISE÷ £38
SPELLCHECK IIIMM.* ÷ £21 (dl £31 (dlINTERWORD £46 (dl EDWORD II £43 fa)LANGUAGE ROMS:Micro Prolog £62 (Cl hOcrotext - £52 (elISO PASCAL £51 (c) LOGOTRON _ £55 (c(LOGO E46 (c) MACROM E33 (dlLISP E39 (dl COMAL 143 (di
Oxford Pascal £36 (e)COMMUNICATIONS ROMS:TERMULATOR £25 (dlMASTER TERMULATOR £34.75 (dlCOMMUNICATOR £49 (dlCOMMSTAR II E28 (dlMODEM MASTER £11 (dlCOMMAND £34 (dlUTRITY ROMs:DOTPRINT PLUS for FX/RX compatiblesDOTPRINT DUAL for MX rangeAcorn Graphics Extension Rom ... £28 (dlMerin with 57 disc utikty commands100 page manual £37.50 (c)
MULTIFORM Z80 2nd Processor for the BBCThis unique 280 2nd Processor r-_-- OSM wig allow use of almost any standard CP/M soft-ware on the BSC micro. It is supy with a ntariber of different CPIM formats and includes autility to configure it to read other f ormats. This is particularly useful in environments where com-puters with different CP/hi formats are used and the data cannot be easily exchanged betweenthem. Mains powered (includes Pocket Words -tar & MSDOS RAY vary) £249 (b)MSDOS Read/Write £49 Icl
META Version 3 ASSEMBLERAssembles 17 of the popular processors. Over 70K long postern on two corns and a disc andprovides complete Editing and Assembly fealties. It uses appropriate mnemonics for differentprocessors. Fully nestable macros, nestable conditional assembly OF/FISF/ENDIFI: modularsource code, true local and global labels, 32 bit labels and arithmetic. 30 ways to send objectcode and 50 directives.A powerful editor with many features. Send for dented leaflet. £145 lb)
BBC DISC DRIVES5.25" Single Drive:1 a 400K 40'80T DS: TS400 E99 lo) PS400 with psu £109 lb)5.25" Dual Drive:2 a 400K 40130T DS: TD800 . . E179 la) PD800 with psu2 x 400K 401307 DS with psu and built in monitor stand PD800P3.5" Drives:1 a 400K 80T DS TS35 1 E75 (b) PS35 1 with psu1 x 400K 80T DS with psu TD35 2 E129 (b) P035 2 with psu
£199 lel£209 lal
£99 110£169 lb)
3M FLOPPY DISCSIndustry standard floppy discs with a life time guarantee. Discs in packs of 10:
5Y4 DISCS 3% DISCS40T SS DD £8.50 (d) 40T DS DD £10.50 (dl 80T SS DO £15.00 (d)80T SS DD£11.50 (dl 80T DS DD E13.25 (dl SOT DS DD £19.50 (d)
DISC ACCESSORIESEngle Disc Cable E6 (di Dual Disc C:.- = £8.50 (dl10 Disc Library Case £1.80 (c) 30 Disc Stc,:= Sox E6 (el40 Disc Lockable Box E8.50 (c) 100 Disc Lockable Box E13 (c)Repoidene Drivehead Cleaning r.. : ,. :1 20 disposable cleaning kits 51!," £14.50 (d): 33" £16 (dl
BT APPROVED MODEMSMIRACLE TECHNOLOGY WS Range
WS4000 V21;23.(Hayes Compatible. Intelligent, Auto Dial,Auto Answer) £135 lb)WS3000 V21/23 ProfessionalAs WS4E00 and with BELL standards andbattery back up for memory £244 (b)WS3000 V22 ProfessionalAs WS3000 V21/23 but with 1200 baud fullduplex £409 (a)WS3000 V22 Ms ProfessionalAs V22 and 2400 baud IL' E537 (alWS30001B8C Data Lead - E7 (d)
SPECIAL OFFEREPROMs/RAMS
2764-25 £2.80 Id)27128-25 £3.60 Id)27256 £5.00 Id)27512 £9.90 (d)6264LP-15 £2.60 (d)
WS2000 V21.1/23Manual Modem £92 lb)WS 2000 Auto Dial Card £27 Id/WS 2000 Auto Answer £27 (dlWS 2000 SKI Kit ES (d)WS 2000 User Port Lead E5 (dl
(Offer /inked to current crocks!
PROJECTS:Junior Computer Kit £86 (b)Housekeeper kit £58 (b)Elekterminal Kit 11980) £50 (b)ASCII Keyboard kit £75 (b)J C Books 1. 2, 3, & 4E6.90 (c) eaUniversal Terminal (6502) Kit £75 (b)Elekterminal Kit (1983) £70 (b/
LANGUAGES:6502 Assy Lang Prog8086 BookAcorn BCPL User Guide E15.00Acorn FORTH 17.50Acorn LISP £7.50Acorn ISO Pascal Ref Manual .110.00Intro to COMAL £10.00Intro to LOGO £7.50Micro Prolog Ref Manual £10.00Introduction to Turbo Pascal.. E14.95Prog the Micro with Pascal _ . .£8.50The UNIX Book E7.50Unix User Guide C19.95Understanding Unix £18.45813C MICRO GUIDE BOOKSBBC User Guide Acorn £15.00BBC Plus User Guide 115.00Drawing your Own BBC PrograrnsE6.95
Math Prog in BBC Basic E7-95Toolbox 2 £10.95VIA 6522 Book 450PROGRAMh1INGILIT1UTYAdvanced Sideways Barn UserGuide E9.95Advanced User Guide (BBC! £12.50Applied Ass.,Lang on the BBC £9.95B3C Micro Sideways ROM's RAM'sE9.95Guide to the BBC ROM £9.95Beginners le to £7.95
EPSONLX800FX800FX1000EX800EX 1000L0800 (80 ad)LQ1000 (135 col)
PRINTERSKP915 i156 coil (369 (a)
£189 fa) BROTHER HR20 £349 (al£299 fa) STAR NL10 (Parallel Place) £190 fa)£405 (a) STAR NLIO (Serial . £219 (a)£409 la) JUIU 6100 (Daisy Wheel) _ £295 fa)E549 (a) INTEGREX (Colour) £549 (a)£399 la) NAT PANASONIC KX P 1081 £149 (a)E529 fa) NAT PANASONIC KX P 3131 _ £249 (a)
TAXAN KP815 (80 col) ..... E269 fa)We bat/ in stock a large variety of printer attachments. interfaces and consumables.Pf,-.= write or phone for details.
ACCESSORIESBUFFALO 32K Buffer for Epson printers £75 (dl; FX80 plus sheet feeder E129EPSON Serial Interface: 8143 £30 (01; 8148 with 2K buffer £65 (b).EPSON Paper Roll HoMer £17 lbl; FX80`80485 Tractor Attach £37 RXFX80Dust Cover £4.50 (dl; 1X80 Tractor Unit £20 (c); 10800 Tractor Feed £47 lb).EPSON Ribbons: MKRX/FX80 £5; MXI1VFX100 E10 (dl LX80 E4.50 Idl;JUKI: Serial Interface £65 (dl; Tractor AtrsciL E149 (a): Sheet Fccdcr £219 la):Ribbon E2.50 (a); Spare Daisy Wheel £14 td).BROTHER HR20: Sheet Feed £229; Ribbons - Carbon or Nylon £3: Tractor Feed1116 (a): 2000 Sheets Fanfold with extra fine perf. 9.5" -113.50: 15" E17.50 (b).BBC Parallel Lead £6; Serial Lead E6 (d); IBM Parallel Lead (2m) £12 (d).
MONITORSMICROVITEC 14" RG81431 Standard Resolution...£179 (al1451 Medium Resolution £225 (al1441 Hi Res E365 lal
MICROVITEC 14" RGIAPAL & Audio1431 AP Standard Resolution E199 (a)1451 AP Medium Resolution £259 Ia)MICROVITEC 20" RGBfPAIJAudio2030 CS std Res E380 (a)2040 CS Hi Res E685 (a)Mitsubishi 14" RGB Med Res, (138C11BM)
£219 (a)
TAXAN K12SV620 12" £279 (a)TAXAN K12SV625 12" .... £329 fa)12" MONOCHROME MONITORS:TAXAN:Taro," KX 117 12- Green P31 E 85 (alTaxan KX 118 12" Green P39 E 95 (a)Taxan KX 119 12' Amber .. E 95 (a)PHILIPS:7502 Green Screen E 75 (al7522 Amber Screen 1 79 (al7542 White Screen E 79 la)All Mims Monitors supplied with swivelstand
BOOKSNo VAT on books; Carriage (c)
. 3.0 User Guide E9.00£9.00£9.00E9.95
£19.95£23.95 Wordwrse Plus
SOUND & GRAPHICS:Mastering Music £6.95
DISC DRIVE SYSTEMS:Advanced Disc User Guide ....114.95Disc Book £3.50Disc Programming Techniques 17.95Disc Systems £6.95
on the BBC £6.95
APPLICATIONS:Interfacing Proj for BBC £6.95BBC and Small Business £5.75
PROFESSIONAL SOFTWAREWordstar made easy £16.95Introduction to Wc--rrar £17.95Wordstar Handle:, -.. £11.95nBase rfor the 'we user 116.95
- =: £22.95£18.95£16.95E17.45£16.95£22.95£17.95£16.50
- - '23
AtIv T, = , aBase 11111Maste, -
CPA( -Introducing CP/M on BBC & 280 £9.95Ms Pc DOS E10.95
PROGRAMMED ROMS FOR ELEKTORPROJECTS
503-N Jilt. Computer Monitor =' Dice 2716 E 7.302708E 4.80 )=. * _ & Video Routine for DOS
504 Disco fights 2708 E 4.80505 Chess Intelekt . 2 x 2716 £14.60506 J C Tape Monitor . 2716E 7.3050714 J C Printer Mon & PME
2716 £ 7.30508 J C Bus Control 82523 E 4.80510 150 MHz Freq Meter 2.82523
£ 9.60514 Dark Room Computer 2716 £ 7.30
522 C-arGen & video; Routine for ex-tended junior 2732 a 2.2716 124.00523 Char. Generator . _ 2732 £ 9.00524 Ouantisizer 2732 E 9.00525 Universal Term 2732 E 9.00526 Wind Dir Ind 2716E 7.30527 Elabyrinth 2716 E 7.30530 Daisywheel Iface 2 2716 £11.00
ALL PRICESEXCLUDE VATPlease add carnage 50p unless
indicated as follows:
fa1f8 1102.50 (clE1.50) fillf 1.00
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13 Editorial14 Electronics news16 Computer news18 Telecommunications news50 Letters
A new approach to effectivelearningp. 48
Science mobilizes to combatmurder in the airp. 59
Light -powered thermometerp. 64
INFORMATION23 New literature; 37 Events;50 People; 61 & 73 NewProducts; 70 Readers'services; 71 Subscriptions;72 Terms of business.
GUIDE LINES75 Switchboard; 76 Buyers'guide; 78 Small ads;78 Index of advertisers.
ELECTRONICSTECHNOLOGY34 Synchrotron X-rays reveal how ice flows:
nev./ laboratory equipment reveals details ofthe flow mechanism of ice.
38 MMICs revolutionize wideband RF amplifierdesign: Avantek's new devices make someof the dreams of RF designers come true.
43 Application notes: a newly developed opto-triac enables automatic mains voltageselection.
44 Sir Clive Sinclair: portrait of a super elec-tronics entrepreneur.
45 The rise and rise of the micro: a shorthistory of the development of the micropro-cessor and the microcomputer.
48 European education software: a nevi ap-proach to effective learning.
51 Test & measuring equipment: Julian Nolancontinues his series with a revie'.v of theGould 0S300 and Grundig cv1020oscilloscopes.
56 Telecom 87: a preliminary report from theITU's quadrennial telecomms exposition.
59 Science mobilizes to combat murder in theair: new equipment for the detection of ter-rorist material at airports.
PROJECTS22 Software update for EPROM emulator.
24 DCF77 receiver and locked frequency stan-dard: the highly stable signal from FederalGermany's DCF77 is eminently suitable forcontrolling a locked frequency standard.
30 Switch -mode power supply: a compactSMPSU rated for 2.5 A.
32 Double -trace extension for VLF add-on unit.
33 Software update for microprocessor -controlled frequency -meter.
55 Front end for short-wave receiver: a freshapproach to high-level front-end design.
57 Stereo limiter: a quality unit for use in taperecorders, transmitters, PA systems, anddiscotheques.
64 Light -powered thermometer: an accurate,digital thermometer that operates fromsolar cells.
63 Noise blanker: an indispensable unit for im-proving reception of very weak signals inthe SW bands.
66 Wideband aerial booster and splitter: thissingle -transistor unit provides a means offeeding several radio or TV sets withoutloss of quality.
69 Front-end for FM receiver.
In next month'sissue:The main theme isTelecommunicationsand a number ofarticles will deal .viththis important topic.Further, The flat dish aerial Pre -scaler for
multi -function fre-quency meter
Intelligent timestandard forDCF77 receiver
Telecom 87: ISDNand all that
80C186: industryis moving toCHMOS
Active loudspeaker
see pages 8 and 9for our specialoffer of three Crotechoscilloscopes
Front coverA computer -controlled testsystem from SIRAmeasures the op-tical transfer functionand the modulationtransfer function oflens systems to givean indication of thequality and theability to resolve finedetails in the imagewith adequatecontrast.Photograph CROWNCOPYRIGHT RESERVED
EE
January 1988
8052 -BASICMICROCONTROLLER-KIT
I/O CONNECTIONSJ
r5UFFERS
TI142,40 / P1i1.1 PT
5052 -BASICCONTROLLER
RS232CONVERTERS
- PRINTER-4' DUPLEX
PORT
EPROM PROGRAMMER
AD CABB
DATA
32K BYEPROMMEMORY
I\
CONTPOL.
BUFFERS
X00EXPANSIONCONNECTOR
32K BY 8STATICMEMORY
POWERSUPPLY
T
B TO 15VSUPPLY
FEATURES INCLUDE* Pov..,erful Enhanced Basic Interpreter,* On Board EPROivl Programmer,* Program Development from a VDU,* 32K Bytes of CiviOS Static RAM,* 32K Bytes of CMOS EPROM (expandable to 56K
Bytes),* Two RS232 Ports,* Single Unregulated Supply Requirements,* Small Physical Size (80 by 100mm),* Expansion with range of Compatible Circuit
Boards.
KIT including all components, full instructions andoperating manual -E129
Manufactured and Fully Tested Circuit Board -£244.
"All prices exclude VAT.Packaging and Postage FREE (UK onlyo.Overseas P&P : -- Europe £2.75
Elsewhere £6.50."
For full details please contact
Li11 electronics ltd
MONIFIETH BUSINESS CENTREDUNDEE DD5 4PJ Telephone: 0382 534944
MATMOS LTD. 1 Church Street, Cuckfield, West Sussex, RH17 5JZTel: 104441 414484 454377COMPUTER APPRECIATION, 111 Northgate, Canterbury, Kent.CT1 18H. Te': 102271 470512
ITT SCRIBE III WORKSTATION. Compact monitor sized unit with high quality high resolution2- Green screen monitor (separated video & sincL 5V & 12V cased switchmode power.pply. processor electronics incorporating TEXAS 9995 & 280H processors with
"28 kbytes & associated support chips. all BRAND NEW but with only monitor & powersupply guaranteed working. Original cost at least £2500.£39.95 (cam £5.00)DATA GENERAL microNOVA Model MPTI100 SYSTEM with the following features: terminaliced desktop unit. mN602 processor with 64kbytes RAM. 2 x RS232 interfaces. connec-!,:r for microNOVA 1.0 bus. dual D5013 5`.." floppy disc drives. 83 key keyboard, green,,creen 12" monitor, 25 r 80£165.00 lean. £10.001?.1ATMOS TERMINAL MATMOS PC with terminal emulation. With set-up menu & with data
e. up to 9600 8.ad. Machine is easily modified for split Baud rate operation. 75:1200a=ROAISpluos into ROM socket accessible from exterior. Emulation is VT -52 compatible for:rsor addressing. MICROSOFTBASIC is available from the keyboard. BRAND NEW.
£69.00 (can. (5.001TRANSDATA MODEL 307 ACOUSTIC COUPLER. Low cost self contained modem unit allow -
micro or terminal connection to BT lines via telephone handset. V.24 interface. up to 300Saud, originatetanswer modes. etc. BRAND NEW(19.95 (caw. £3.00)DUPLEX Model 100 green screen high resolution monitor with composite video input. Withtilt & swivel stand. BRAND NEW. (can. £5.001f 39.50PLESSEY Model T24 V22,1/22 bis 2400 Baud MODEM. Compact. automatic modem offer -^g both V22 & V22 bis comparability, 1200'2400 Baud duplex operation with auto bit raterecognition, auto call and auto answer. BRAND NEW. NEW LOW PRICE.£169.00 (cam £5.001PANASONIC Model JU-363 3W' floppy disc drives. Double Sided Double Density 80 track1 megabyte capacity unformatted. Latest low component 1,3 height design. SHUGART in-terface using 34 way IOC connector. Will interface to just about anything. BRAND NEW. Current model.£59.50 tcarr. £3.001HITACHI Model 305S,SX 3" disc drives. W,th SHUGART interface. Uncased. Single sided250K (double density,: 40 track; 100 ipi: soft sector: 3rns track to track time: standard 34...ay edge connector: 12V & 511 powered (standard connector) overall 3.7W. Suitable far BBCwith DFS. AMSTRAD 6128. TATUNG EINSTEIN. AMSTRAD 664 & as a second drive for theAMSTRAD 464. BRAND NEW. Data cables are available from us for the AMSTRAD 6128 &FiRC at £7.50. and with data & power cables for TATUNG Einstein at £12.00.£24.95 (can. £3.001FUJITSU Model M2230AS WINCHESTER disc drive. 6.66mbyte capacity unformatted.'5 32 sectors. 320 cy:',,ders. MIti ST508 interface. BRAND NEW.£75.00 (care. £3.00)DRIVETEC Model 320 high capacity 514" disc drives. 3.3Mbyte capacity drive 160 track.
gradab!e to 48 No further info at present. BRAND NEW.£45 00 (care. £3.00)SHUGART Model 405R 5';;" disc drives. Full height. single sided. 40 track. untested vnth-: :
66.95 Icon. (3.001ASTEC SWITCH MODE PSU. 5V f=8 A: 12V # 3A; -12V e0.3A - to a total 65W. Com-= BCI cased Lni. BRAND NEW.£14.50 (care. (3.001=,-ease note.- ' V/S4 :3; ACCESS 3CCe;7!:, VAT must be added to all prices quoted.
1-1 HappyPart type4116 (Pulls)4164 15Ons Not Texas41256 150ns41256 120ns41464 12Ons2114 200ns Low Power6116 150ns Low Power6264 150ns Low Power62256 120ns Low Power2716 450ns 5 volt2532 450ns2732 450ns2732A 250ns2764 250ns Suit BBC27128 250ns Suit BBC27256 250ns27512 250ns
ernories1 off 25-99 100 up1 00 .90 .851 20 1.05 .973.40 3.15 2.953.50 3.25 3.053 45 3.20 2.991 75 1.60 1.551 40 1.25 1.202.75 2.55 2.40
10.95 10.25 9.653 20 Call Call5.40 Call Call3.20 Call Call3.95 Call Call2 85 Call Call3.95 Call Call4.55 Call Call8.45 Call Call
Low profile IC sockets: Pins 8 14 16 18 20 24 28 40Pence 5 9 10 11 12 15 17 24
Please ask for quote on higher quantities or items not shown.Data free on memories purchased. Enquire cost for other.
Write or 'phone for list of other items including our 74LS seriesand a DISCOUNT ORDER FORM.
Please add 50p post & packing to orders under £15 and VAT tototal. Access orders by 'phone or mail welcome.
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Elektor sariRoute Nationale; Le Seau; B.P. 5359270 Bailleul - FranceEditors: D R S Meyer;G C P Raedersdorf
Elektor Verlag GmbHSitsterfetd-Stralle 255100 Aachen - West GermanyEditor: E J A Krempelsauer
Elektor EPEKaraiskaki 1416673 \Joule - Athens - GreeceEditor: E Xanthoulis
Elektor Electronics PVT Ltd.Chhotani Building52 C, Proctor Road, Grant Road (ElBombay 400 007 - IndiaEditor: Surendra lyer
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Copyright 1988 Elektuur B.V.
ABC.1/1WAR G MEMM./LI c CPCL,LATV5
-9:11NO REAL SOLUTIONSIN THE HAGUEAs was expected, at the end of their two-day meeting in The Hague lastNovember, 12 of the 13 members of the European Space Agency -ESA -gave their cautious approval to a toned -down multi -billion dollar plan thatwill decide Europe's role in space for the rest of this century. Britain did not- and for very good reasons.
The three major projects on which a decision had to be made were: (a)Ariane V, French -led and estimated to cost close to $4 billion; (b) theFrench -designed Hermes mini space -shuttle, estimated to cost almost $5billion; and (c) Columbus, Europe's contribution to the manned Americanspace station (EE, December 1987) and estimated to cost just over $4billion. ESA's total budget for the next 13 years is a staggering $37 billion. Ifhistory is anything to go by, this figure may well be exceeded by an ap-preciable amount.
Ariane V, formulated ten years ago, is already out of date. The main reasonfor this is that, in spite of what was thought then, satellites have not be-come much heavier in the intervening years, and are unlikely to do so inthe foreseeable future. There is, therefore, no need for a heavy -lift rocketlike Ariane V. Arianespace, which is responsible for the Ariane launches,has said that the more powerful version of Ariane IV, which can lift over 4tonnes into geosynchronous orbit, is more than adequate for its needs.
According to many experts, Hermes is likely to cost well in excess of itsestimated $4.9 billion. Mr Kenneth Clarke, Minister of State for Trade and In-dustry, said at the meeting that the British Government believed theHermes was not justified on commercial, industrial, and scientific grounds,since it simply imitates what the Americans and Russians did in the 1960s.Federal Germany, and some other members, have also expressed seriousdoubts about the viability of Hermes.
Britain also believes that the ESA's policy as regards the development ofcommercial products is a serious impediment to much of the European in-dustry. Compared with NASA's technology utilization programme, that of theESA is embryonic. There is also a feeling among British space contractorsthat the influence of the ESA is already on the wane, because satelliteoperators have begun to order satellites direct rather than through the ESA.Eutelsat, for instance, whose first generation of satellites was supplied bythe ESA, has itself awarded the contract for four second generation EutelsatII satellites to Aerospatiale.
None the less, the meeting decided to go ahead with the development ofAriane V; a three-year further study, costing close to $600 million, ofHermes; and a three-year further study of Columbus, costing well over$700 million.
Equally grave problems, such as the liberalization and deregulation of sat-ellite broadcasting and telecommunications were not seriously discussed.The main obstacles to a deregulation programme remain the national tele-communications agencies and their monopolies. Such monopoliesthreaten the economic success of telecommunications and direct broad-casting satellites.
It is to be hoped that the liberalization of satellites, as put forward in theEEC's green paper on telecommunications (EE, September 1987), which isessential for the development of a strong European satellite manufacturingindustry will be undertaken in the very near future.
Hasn't the time come for the other western European countries to follow theexample of Britain and Luxembourg, and America, and stop putting hugeamounts of taxpayers' money into satellite systems and leave it to com-mercial (non -government) organizations to provide telecommunicationlinks and direct -broadcasting satellite TV services? That way, we might evensee a pan-European standard for high -definition TV services in the not toodistant future.
14' EE
January 1988
ELECTRONICS NEWS ELECTRONICS NEWS
The MM -20 twenty -watt multiple outputpower supply measures only 69 x 114 x37 mm and is available from IntelligencePower Technology Foredown Drive PORTSLADE BN4 2BB Telephone (0273)420196.
Benefits for Scottishelectronics plants?Marconi and Hughes Aircraft Companyare determined that the companies'Scottish plants will benefit substantiallyshould a four -nation contract formanufacture of the radar for the newEuropean Fighter Aircraft (EFA) go to aEuropean consortium, in which MarconiDefence Systems is a prime partner.The plants, all located in Fife, are Mar-coni Command and Control Systemsand Marconi Instruments, with a totalworkforce of over 2,000, and HughesGlenrothes with 900 employees.These plants are in the forefront of tech-nology, with Marconi involved inmanufacturing support equipment,while Hughes in Glenrothes specializesin a wide range of components andassemblies.The MSD radar proposed for the EFA isbased on the Hughes AN/APG-65 in-stalled in the F/A-18 Hornet. This Air-craft is being operated or supplied to theCanadian Armed Forces, The RoyalAustralian Air Force, the Spanish AirForce, and the US Marines as well as theUS Navy. The Federal German Air Forcehas also selected the Hughes radar aspart of the Luftwaffe's F-4 ImprovedCombat Efficiency programme. The ad-vanced radar represents business worthmore than £1 billion, one third of whichwill be carried out in the UK.Design of the EFA has been frozen. Afull-scale model was displayed at the
Paris Air Show last June. The go-aheadfor full-scale development is expected tobe given within a few months.Expected EFA ordefs stand at 250 eachfor Britian and Federal Germany, 165 forItaly, and 100 for Spain.
Advanced CMOS 4 -bit binaryadderContinuing to build up its advancedCMOS logic (ACL) line, GE Solid Statehas added a 4 -bit binary full adder withfast carry. Called the CD54/74AC/ACT283, the device adds two 4 -bitbinary numbers and generates their sumplus a carry output if the sum exceeds15. ACL is GE's advanced CMOS logicfamily whose switching speed is compar-able to that of high-speed bipolar logicsuch as Schottky (S), Advanced Schot-tky (AS), and FAST. Because of itsCMOS design, ACL consumes far lesspower than bipolar logic.
THE LOGIC FAMILYSPEED - POWER SPECTRUM
LST,t
strC5 NCTS
a-. raLcn s 10
. 700 JECL
EC L1.1,
0 3 1'0 20
vERAGE CC MWERDISS7PAT/01,10.,W5
rAS,AS
anen 54/74AC/ACT283
Full information from GE Solid State Beech House 373-399 London Road CAMBERLY GU15 3HR Tele-
phone (0276) 685911.
RCCB becomes RCDThe Electrical Installation EquipmentManufacturers' Association-EIEMA-Working Group is to en-courage industry to adopt the term"RCD"(Residual Current Device) inplace of "RCCB (Residual CurrentCircuit Breaker).The present use of different names forthe same device was highlighted in a re-cent BBC TV "On the House" pro-gramme. The use of the term RCD willbring the industry into line with thereferences used within the IEE WiringRegulations.
National Semiconductor'spurchase of FairchildcompletedNational Semiconductor's president andChief Executive Officer, Charles E.Sporck, announced recently that hiscompany's purchase from Schlumbergerof Fairchild Semiconductor Corpor-ation's worldwide semiconductorbusiness had been completed. He wenton to say that this cleared the way tocombine the two businesses into onecompany.Experts feel that the National -Fairchildcombination will create America's besttechnologically balanced semiconductorsupplier. National's advanced CMOStechnology should fit in well with Fair-child's strong position in advancedbipolar technologies.
BR contract for WestinghouseWestinghouse Signals, a Hawker Sid-deley subsidiary, has been awarded asignalling equipment contract by BritishRail worth £1 million. The contract callsfor the company to supply, install, andtest, solid-state interlocking (SSI) equip-ment for the resignalling of the areafrom London's Liverpool Street Stationto Bethnal Green.Solid-state interlocking is a computer -based safety system using "redundancymanagement" techniques for optimumefficiency, reliability, and operationalsafety. It is designed to replace conven-tional electro-mechanical relay in-terlockings. The central SSI com-municates serially with lineside pro-cessors over a data link cable to controltrackside signalling functions.
The Philips PM6665 Timer/Counter isavailable from Electronic Brokers 140-146Camden Street LONDON NW1 9PB Telephone 01-267 7070.
EE
January 1988
ELECTRONICS NEWS ELECTRONICS NEWS
Cossor wins CAAFU projectmanagement contractCossor Electronics Air Traffic ControlSystems has been awarded the contractto project -manage the programme torefit the Civil Aviation Authority's cali-bration flight, based at Stansted Air-port.
In the photograph, Mike Shadwell (2ndfrom left), General Manager Operations,Cossor Air Traffic Control Systems Div-ision, presents a framed photograph of aCAA Flight Calibration Unit aircraft toCAAFU Manager, Dave Reiffer (farright). Also shown are (from left,clockwise): Neil Munro, Cossor ProjectManager - CAAFU; Richard Barber,Cossor Regional Sales Manager, ATCSystem Devision; and Anne Rangeley,Cossor Public Relations Officer.
Much work needed for freeEC market by 1992At a meeting of Presidents of Europeanelectrical and mechanical tradeorganizations in Berlin, the EuropeanCommission was told that there weremixed views in Britain about the goal offree trade within the EEC by 1992."Our instincts and our logic still take ustowards free trade, but that must be fairtrade - and on this there is a firm needfor us to be convinced," said Sir WilliamBarlow, who was representing the UK,and especially the electrical and elec-tronic manufacturers' trade federation,BEAMA.Sir Williams, who is chairman of BICCPLC, was replying to Dr. Karl -HeinzNarjes, Vice President of the EuropeanCommission, who gave a survey of EECindustrial policy and the completion ofthe EC internal market in 1992.Sir William outlined the areas whichwould need attention to support a freeinternal market. These were: (a) owner-ship of companies and movement ofcapital; (b) labelling and origin marking,quality assurance, and standards; (c) im-
proved surveillance of products; and (d)public sector purchasing.Sir William said that any nationalcompany within the EC should be ableto purchase equity or take over other ECcompanies. There should be completelyfree movement of investment capital andEC member national financial insti-tutions should be required to trade andto finance freely within.the EC.He continued to say that there was aneed for further development ofreciprocal agreements involving themutual acceptance of national stan-dards, of national test and qualityassurance reports.Sir William called for the termination ofthe "automatic and chauvinistic actionsof local officials and inspectors, and ofpurchasing officers, which preclude con-sideration and supply of other ECcountries' alternative products. Im-proved surveillance should be aimed atpreventing the abuses of counterfeiting,of wrongful claims of compliance, ofquota and sanction breaking, and ofavoidance of commitments and laws.This activity must be greatlystrengthened. It must be organized, co-ordinated, well -funded, and better -ledand directed".
Thermoprobe replacesvoltmeterA new, low-cost electronic test instru-ment called Thermoprobe quickly ident-ifies dead active components on PCBswithout direct contact.
The solid-state device consists of a ther-mistor probe connected to a modifiedWheatstone bridge circuit. It is designedto measure minute temperature changesof 0.02 °C. Since defunct resistors,transformers, diodes, or ICs, do notemit heat they can be quickly identifiedon the unit's built-in S -meter as theprobe is moved in close proximity tothem.Its small size makes the Thetmoprobeparticularly useful in field service appli-cations for computers, electronic instru-
mentation, video, and hi-fi equipment.It operates from a 9 -volt battery.The Thermoprobe is available at $21.95from Metrifast 51 South DentonAvenue New Hyde Park New York11040 USA.
Revolutionary electron beamtesterAn innovative new system for testingVLSI chips has been introduced bySchlumberger Technologies AutomaticTest Equipment. Combining scanningelectron microscope (SEM) technologywith CAD/CAE tools within a familiarworkstation environment, thecompany's Integrated Diagnostic System(IDS) 5000 Workstation brings un-precedented efficiency and accuracy tothe field of VLSI diagnosis andcharacterization, yet remains easy forengineers to use. The system waslaunched at the recent Productronicatrade fair in Munich.Full details from SchlumbergerTechnologies, Automatic Test Equip-ment Ferndown Industrial Estate WIMBORNE. B1121 7PP Telephone(0202) 893535:
Flash EEPROMs from SEEQTechnology/National Semi-conductorSeeq Technology and National Semicon-ductor have concluded a four-year ex-clusive technology licensing andmanufacturing agreement whereby thetwo companies will together market anew family of high -density, competi-tively priced CMOS Flash EEPROMs.Flash .EEPROMs have several advan-tages over standard UVEPROMs. TheFlash can be erased electrically andreprogrammed in less than one minute,compared with the 20 minutes requiredfor the UVEPROM. This erase/repro-gram process can be achieved in a singlestep with one piece of equipment for theFlash. For the UVEPROM, the erase/reprogram process is a two step cycle, re-quiring several pieces of equipment. Asa result, field service costs can be re-duced, since the Flash devices do nothave to be removed for reprogrammingand can be reprogrammed through adown -line load operation.Seeq International Ltd DammasHouse Dammas Lane o Old Town SWINDON SN1 3EF o Telephone(0793) 694999.
16 EE
January 1988
COMPUTER NEWS COMPUTER NEWS . CONew MC68HC11 developmentsystemAshling Microsystems, which designsand manufactures microprocessor devel-opment systems, has introduced a com-plete development system for theMotorola MC68HC11 8 -bit microcom-puter range. Called the CT68HCII, thesystem supports all current versions ofthe Motorola device. The CT68HC11supports software development in high-level language and in assembler. Allthree operating modes of the Motorolapart can be emulated up to full chipspeed and activity on all of themicrocomputer's I/O ports is traced inreal time.
Further information from AshlingMicrosystems Ltd Plassey Techno-logical Park Limerick Ireland Telephone + 353 61 334466.
Euromicro 88 - Call forpapersEuromicro 88 is the fourteenth annualsymposium on microprocessing andmicroprogramming to be held at Zurichfrom 29 August to 1 September this year.The purpose of the symposium is tobring together people from business, in-dustry, government, and academic in-stitutions, who are interested in all prob-lems related to the underlying tech-nology and use of microcomputer sys-tems.Authors are invited to submit originalpapers on recent applications, develop-ments, and research associated withmicrocomputers. Abstracts of the papersshould reach the Programme Chairmanno later than 15 January. Full details onhow to submit papers and short notesmay be obtained from the ProgrammeChairman, Stephen WinterPolytechnic of Central London Fac-ulty of Engineering and Science 115New Cavendish Street LONDONW1M 8JS Telephone +44 1631 4263 Telex 25964.
CMOS version of 80186Intel has recently introduced aCHMOS* version of its 80186, a highlyintegrated microprocessor for embeddedcontrol applications in industrial auto-mation, communications, and officeautomation. It is type -coded 80C186 andis currently available for 12.5 MHz oper-ation; a 16 MHz version will becomeavailable shortly.The 80C186 in compatible mode is pin-for -pin compatible with HMOS* 80186systems, but it has been enhanced tosupport Intel's next -generation numericsco -processors.It is claimed that, under normaloperating conditions, the 80C186 needsonly 20% of the power the HMOS 80186requires.*CHMOS and HMOS are patented pro-cesses of Intel Corp.
New VME-bus fromCompcontrolIncorporating a unique combination offeatures, Compcontrol's new Type CC -97 VME-bus replaces four separateboards in 16 -bit systems: SCI interface,processor, 2 Mbyte dual -ported dynamicRAM, and 384 kbyte static RAM -EPROM. The board works as an in-telligent SCSI and serial communi-cations controller, a single -board com-puter, or a CPU board in multiprocessorsystems. It is particularly suited tomultiprocessing, since it generates andaccepts seven levels of interrupt, can re-quest the VME-bus to use any of fourpriority levels, and has a mailbox formessage passing.Further information from CompcontrolBV Stratumsedijk 31 P.O. Box 193
5600 AD Eindhoven TheNetherlands.
Olivetti launches new rangeof PCsBritish Olivetti has just announced theprices and availability of the new rangeof 80286 -based PCs, the M280. Thesenew machines combine high perform-ance with an open architecture allowingfor the widest choice of data storagemedia, including 3.5 inch diskettes, andgraphic display standard, including EGAcompatibility.The M280s use the Intel 80286 processorrunning at 12 MHz and have sockets foran optional 80287 numerical co-processor built into the motherboard.The processor speed is matched by the
40 ms access time on the 20 and 40Mbyte hard disk models, and 28 ms onthe optional 60 Mbyte model. Thismakes the M280 one of the fastest 286 -based PCs on the market.In readiness for OS -2, and to providesufficient resource for multi-userXENIX or network file server configur-ations, the M280 is equipped as standardwith 1 Mbyte of RAM mounted on themotherboard. This is expandable up to 7Mbyte via the system's expansion bus.Recommended prices of the M280 rangefrom £3,011 for the 20 Mbyte hard -diskversion (1.2 Mbyte 5.25 inch diskette or1.44 Mbyte 3.5 inch diskette; OGC dis-play controller; monochrome display;102 -key keyboard) to £3,600 for the 40Mbyte hard -disk model with EGAcolour graphics. A large number of op-tional components is also available.
Emulation of PLCC devicesPentica has introduced a more reliablemethod of connecting a PLCC-basedtarget system to an in -circuit emulatorprobe.The header is. made of fibreglass rein-forced material, similar to that used forPCBs. The contacts undergo a thickplating process before they are finishedin hard nickel gold. Connection to theprobe is completed with a flat, mylar-based, flexible ribbon cable.
The new connector system offers twosignificant advantages: the solid blockconstruction prevents the contacts frombeing bent or broken and the printed rib-bon cable allows the track pattern, in-cluding guard tracks, to be optimized forthe microprocessor, which reduces noiseand cross -talk and improves the re-liability of the connection.Further information from PenticaSystems Ltd Oaklands Park WOK-INGHAM RG11 2FE Telephone(0734) 792101.
EE
January 1988
COMPUTER NEWS ® ©NViIPB 7:31/ NEWS CI:1
Real-time solids modellerThe Real-time Solids Modeller from Sili-con Vision provides a sophisticateddesign tool for creating 3-D solid orwireframe objects of any complexity.
Unlike other packages, this system canperform full colour hidden -surfaceremoval for any solid object at highspeed. Colour hard copy of the designscan then be produced on a range ofpopular pen plotters or printers for pro-fessional results. Further informationfrom Silicon Vision Ltd 47 DudleyGardens HARROW HA2 ODQ Telephone 01-422 2274.
OS -2 available at lastIBM has commenced deliveries of thenext generation PC operating system,OS -2, it has developed in conjunctionwith Microsoft. The basic version of thenew system will cost just under £250; anextended version will become availablelater in the year.The new system will allow users to runmultiple concurrent applications and togain access to greater amounts ofmemory. It can address 16 Mbyte ofmemory, which is more than 25 timesthat accessible by MS-DOS, the currentoperating system. According to IBM.OS -2 will work on virtually any PCbased on Intel's 80286 or 80386microprocessors.Microsoft hopes to introduce a morepowerful version of the system to takefull advantage of the 80386.
TimekeeperA new Timekeeper* for the IBMPC/AT/XT and compatibles provides a
low cost real-time clock that can keeptrack of hundredths of a second throughdays and months to years, with leap yearcorrection. The built-in crystal keeps itaccurate to within one minute permonth, and the two built-in lithium cellsmaintain non -volatility of data for morethan 10 years in the absence of power.Software supplied with the Timekeeper*allows the user both set time and readtime and either display it or update theMS-DOS software clock. Programmingsupport can be given for using theTimekeeper* on PCs that are not com-patible with the IBM PC/AT/AXT.
* Timekeeper is a trademark of PinnaElectronics Ltd.Further information from Pinna Elec-tronics Ltd S22 APL CentreStevenson Ind. Est Ayrshire KA203RL Telephone (0294) 605296.
No problems when lightningstrikesRendar's Spikebloc protects all sensitiveelectronic equipment against damageresulting from lightning strikes andpower supply glitches, such as elec-
tromagnetic pulses (EMP) and radio -frequency interference (RFI).Rendar Ltd Durban Road SouthBersted BOGNOR REGIS P022 9RL Telephone (0243) 825811.
8052 -based STEbusArcom's SC52 STEbus board containsan 8 -bit 8052 CPU with built-in BASIC,four memory sockets, EPROM pro-grammer, and serial I/O. It offersdesigners all the facilities necessary toimplement a simple control system withunlimited expansion potential via theSTEbus interface for more sophisticatedapplications.SC52 is based on Intel's 8052AH-BASIC, a maskprogrammed version ofthe 8052 single -chip microcomputer withan 8 K BASIC interpreter. This chip alsooffers 256 bytes of RAM, three counter -times, a UART, and interrupt inputs.Further details from Arcom ControlSystems Unit 8 Clifton Road CAMBRIDGE CBI 4WH Telephone(0223) 411200.
World's fastest 8 -inchWinchester disc driveA new family of 8 -inch Winchester discdrives that combine the world's fastestseek performance with a very high levelof reliability has been announced by Ver-mont Research.The first product in the new Ascutneyfamily, the model 7030, is a 600 Mbyteunit with extremely fast seek times: amere 22 ms for full stroke seek, which isnearlv -10% faster than most 8 -inch discdrives. A rigorous testing programmehas established a predicted MTBF ofover 30,000 hours.
Full details from Vermont Research Ltd Cleeve Road LEATHERHEAD
KT22 7NB Telephone (0372) 376221.
18 EE
January 1988
TELECOMMUNICATIONS NEWS TELECOMMNorwegian Air Force order forCossorAirmatcomnor, the Material Commandof the Royal Norwegian Air Force, hasordered three precision approach radarsystems, valued at £3.2 million, fromCossor.The systems, known as CR62, consist ofa transportable cabin situated by therunway with both an azimuth and anelevation antenna, and a dual displaysystem situated in the air traffic controltower. The display of both azimuth andelevation positions of the aircraft givesthe controller the visual information re-quired to "talk down" an aircraft in badvisibility or in an emergency.The equipment is exactly the same asthat provided to the Royal Air Force,who have now completed installation of46 systems at all RAF airfields in theUK. Gibraltar, Cyprus, FederalGermany, and the Falkland Islands.Similar equipment has been installed atthe Air Force of Zimbabwe's ThornhillBase.
New optical waveguidetransmission system for videosignalsTelevision cameras are today used for avariety of surveillance applications, e.g.for tunnels, outdoor premises andbuildings, and also for monitoring traf-fic flow at busy intersections. In all thesecases, the analog signals from the videocameras must be transmitted over com-paratively short distances to themonitors. In contrast to the coaxialcables used up to now, optical cables of-fer the advantage of practicallyunlimited immunity to interference fromstray electromagnetic radiation and highsecurity against interception. In the 860-nm wavelength range, Siemens has nowdeveloped a video transmitter modulefor optical waveguides that provides alow-cost means of realizing video trans-mission systems.The transmitters and receivers are en-cased in plastic packages. Their elec-trical connections follow the 2.54 -mmpitch DIL pattern. For the optical con-nections either DIN (2.5 mm plug pin)or SMA 3.175 -mm plug pin) connectorsare provided. Optical cables with fibresof 50 pm/62 pm or 100 pm corediameter can be used.The maximum transmission distance is2 km when using 50 pm graded -indexfibre with a maximum route attenuationof 9 dB. The optical transmission uses afrequency modulation method. In order
to increase the range, repeaters can be setup with digital optical modules (50 MBdsystem). Thus, without appreciable lossof quality a distance of up to 8 km (3repeaters, 4 x 2 km route) can becovered. The supply voltage is 5 V. Thesignal bandwidth of typically 7 MHzand the output voltage of 1 V p -p into75 Q permits connection of a colormonitor.Siemens AG Postfach 103 D-8000MUNCHEN 1 Federal Republic ofGermain Telephone 089 2340.
$2 million contract forCincinnati ElectronicsCincinnati Electronics has been awardedcontracts by the McDonnell DouglasCorporation to manufacture and testrange safety receivers for two importantUS space launch vehicle programmes;the USAF Medium Launch Vehicle(MLV/Delta II), and the McDonnellDouglas Commercial Delta. Theagreements call for Cincinnati Elec-tronics to provide 70 range safetyreceivers. The combined value of thesecontracts is S2 million.A range safety receiver is a device used toterminate the flight of a space launch ve-hicle should it veer off course andthreaten range personnel or buildings.The Delta programmes reflect renewedAmerican interest in unmanned satellitelaunch vehicles to complement the SpaceShuttle fleet.The primary use of the MLV will be tocarry global positioning satellites intoorbit. These satellites are used as ultra-reliable reference points for terrestrialnavigation.
Streamlining cable TV controlA computerized system to streamline ad-ministration of cable television networkshas been developed by British Telecom incollaboration with the Digital Equip-ment Company-DEC-and BusinessManagement Systems-BMS.Called System Administration and
Control-SAC-it is the first British -designed software program that billscustomers and monitors maintenanceneeds. It gives automatically an ef-ficient, speedy service for both clientsand cable companies. Costing £1.5million to develop, SAC can be adaptedeasily to the requirements of world cableTV networks.SAC software, currently running onVAX and PDP computers from DEC,not only introduces a highly efficientbilling and administrative controlsystem, but provides on-line diagnostics,statistical reporting, and analysisfacilities. Besides ensuring up-to-the-minute maintenance, it also coversvideotex, video library, the Prestelviewdata service, up to 30 TV channels,satellite transmission, and FM radio.Full details from British Telecom Vision British Telecom Centre 81 NewgateStreet LONDON EC1A 7AJ Tele-phone 01 356 5369.
World's most powerful satelliteTV receiverMultipoint's Type M1400 ultra -low -threshold receiver operates at 5 dBcarrier -to -noise ratio, which affords a30% reduction in the size of dish anten-na required. It contains three inter-nationally patented methods ofthreshold extension and was developedfor use with the European Ku bandsatellites. In response to considerable in-ternational demand, a C -band version isnow also available. This means that theM1400 can be used in the USA, CentralAmerica, Caribbean, Pacific, Africa,and the Middle East, as well as inEurope.
The receiver, which is in current use bymany organizations, including BritishTelecom and France's TDF, operateswith PAL, SECAM, and NTSC.Full details from Multipoint Communi-cations Ltd Satellite HouseEastways Industrial Park WITHAMCM8 3YQ Telephone (0376) 510881.
EE
January 198819
TELECOMMUNICATIONS NEWS TELECOMMBT bids for major IT defencecontractA consortium of InformationTechnology-IT-specialists, led byBritish Telecom, has been chosen to bidfor a 10 -year multi -million pound officeautomation contract from the Ministryof Defence. Other member of the con-sortium are Systems Designers PLC,Honeywell Bull Ltd, and Nixdorf Com-puter Ltd.To be installed during the 1990s, theCorporate Headquarters Office Tech-nology System-CHOTS-will serve24,000 users in more than 40 MoDbuildings throughout the UK.The British Telecom consortium is oneof four selected by the MoD to bid forthe provision of prototype schemes. Thefinal choice will be made between twosuppliers, each of whom will provide twodifferent prototype systems. Each proto-type system will support about 500users.Eventually, the system will comprise alarge number of UNIX -based com-puters, supporting 12,000 terminals and3,000 printers. It will provide secure of-fice automation facilities with a single"terminal on the desk" which can beused to access other MoD systems.UNIX is a standard operating systemthat offers full portability of softwareacross different hardware. Its flexibilityand extensive communications facilitiesensure that UNIX -based systems areideal for multi-user, multi -task, multi -location applications.
Fourth internationalconference on satellitesystems for mobile communi-cations and navigationPapers are now requested for the FourthInternational Conference on SatelliteSystems for Mobile Communicationsand Navigation. The conference is beingorganized by the Institution of ElectricalEngineers (IEE) and will be held at theTEE, Savoy Place, London, from 17 to 19October 1988.The conference aims to provide an inter-national forum to review the currentstate of development and application ofsatellite systems for aeronautical,maritime, land mobile and personalcommunications and navigation viasatellites. This will include consider-ations of the space segment, earth seg-ment, propagation and spectrum utiliz-ation.Papers are invited on a multitude of
Papers are invited on a multitude oftopics: those wishing to offer a contri-bution should submit a synopsis of notmore than 1,000 words to The Con-ference Services Department LEE Savoy Place LONDON WC2R OBLTelephone 01-240 1871.
In -car telephone answeringmachineThe in -car telephone answering machinedeveloped by Vanderhoff is aimed atkeeping the executive in touch at alltimes, and thus provides a vital link inthe communication chain.The Knight machine will automaticallyanswer calls and take messages wheneverthe car is unoccupied or conditions re-quire the driver's full attention. It can beset to answer calls at intervals of betweenthree and 15 seconds, giving the driverthe option of taking the call personally ifrequired.The Knight can also be used as an in -cardictation machine, taking standard minicassettes compatible with many officedesk -top machines. Even more con-venient, a secretary equipped with aduplicate access device can save valuabletime by retrieving the dictated materialover the telephone instead of waiting forthe executive to return to the office.Further details from Vanderhoff PLC Station Approach Fleet ALDER-SHOT GI113 8QY
Plessey telephone exchangesfor ScandinaviaIntegrated Services Digital Exchanges-ISDX-made by Plessey BusinessSystems are to be distributed exclusivelyin Scandinavia by Nokia, the Finnishtelecommunications and electronicsgroup. This follows an agreement signedbetween Plessey and Nokia, which theBritish firm hopes could eventually leadto sales to the Soviet Union and EasternEurope, where its Finnish partner is amajor supplier of equipment.
Debut for VideophoneThe world's first true videophone foruse on ISDNs or switched 56-64 Kbpsdigital networks made its debut al the re-cent Telecom 87 exhibition.Developed by British Telecom, the IRIS
Videophone represents the prototype ofthe cost-effective desk -to -desk businessvideo communications system that willbe commonplace in the 1990s.The IRIS comprises a desk -top -terminalincorporating a CCD camera and colourmonitor together with a separate com-pact video codec (coder/decoder).IRIS is available in 525 -line 60 Hz and625 -line 50 Hz versions, which in-teroperate automatically without theneed of additional standard conversiondevices.Full details from GEC Video Systems 79 Silver Street READING RGI 2SZ Telephone (0734) 864490.
World first for TeliA telefax, photo copier, and computerprinter all rolled into one-the firstmachine of this kind in the world-hasbeen introduced by Swedish Telecom andTeli. Omega, as the machine is called,made its debut at the recent Telecom 87.In ISDNs, the telefax operates at Group4 transmission speed, but for trans-mission to conventional telefaxmachines, it operates at Group 2 orGroup 3 speed.
The internal memory of 10 Mbyte holdsup to 200 A4 -size pages and trans-mission can take place automatically toa maximum of 100 different recipients.Full details from TELL AB P.O. Box1001 S-149 01 NYNASHAMN Sweden Telephone 0752 63962.
20 EE
JanuE.r,, 1988
TELECOMMUNICATIONS NEWS TELECOMMTV SAT -1 OFF TO A FLYINGSTART
One night in the middle of lastNovember, Arianespace and ESAreported the successful launch of TVSAT -1, Federal Germany's first high -power direct broadcasting satellite(DBS), from the ESA launch site atKourou, French Guyana. The launch ve-hicle deployed was Ariane 2. Almost 25years after its conception, and con-siderably delayed by launch failures ofother satellites, TV SAT -1 is expected tobe taken into service next month.TV SAT -I was developed and manufac-tured alongside TDF-1, the Frenchnational DB satellite, under a jointGerman -French governmental pro-gramme. The industrial contractor isEurosatellite, whose shareholders in-clude Aerospatiale, Alcatel Space,AEG/Telefunken, ANT, MBB and ET-CA/ECEC. The Eurosatellite group hasparticipated in more than 50 nationaland international satellite ventures, andhas acquired its know-how from suc-cessful operational communicationsatellites including Symphonie, ECS,Marecs, MeteoSat, Intelsat 4, 4A, 5, 5Aand 6, Telecom 1, Arabsat and DFSKopernikus. It is also involved in thetechnical and commercial co-ordinationfor the future satellites in the Eutelsat 2series. The French DB satellite, TDF-1,will be launched in a few months' time.Both satellites will be positioned ingeosynchronous orbit at 19 °W.
TV SAT -1 has 5 channels installed, 4 ofwhich can be operated simultaneously.There are 6 TWTAs (travelling wave tubeamplifier) each with' an adjustable RFoutput power of 230-250 W. Thetransponder output frequencies lie in the12 GHz DBS band, in accordance withthose assigned to Germany by theWARC (World Administrative RadioCommittee). The boresight EIRP ofTV SAT -1 is claimed as 65.6 dBW(3,500,000 W)Functionally, TV SAT -1 consists of thepayload and the platform.The platform is a product fromAerospatiale and MBB/Erno,designated Spacebus 300. This com-prises the following subsystems:II power conditioning-this provides
the 3 electrical bus systems with 50 Vregulated (payload and platform), and26-50 V unregulated (platform)
oriented solar array-this has a totalweight of 157 kg, and is dimensioned
for an "end of life/summer solstice"power output of 3,215 W. There are43,000 cells on 8 panels, and each panelmeasures 1.6 x 3.6 m.. Each wing on thespacecraft is composed of 4 panels. telemetry (TM) and telecommand
(TC) -this subsystem weighs 40 kg.The satellite position is controlled via a17/18 GHz TC link, while TM is beameddown via 11/12 GHz. S band (2 GHz)equipment is on board for TC and TM inthe transfer orbit, and for back-up.There are approximately 500 measured
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body stabilization throughout allflight phases, including the transfer orbitperiod. The satellite body positioningaccuracy obtained with momentumwheels is about 0.2°. A beam precisionof 0.05° is ensured by an RF sensor andcontrol circuits. unified propulsion-on board is
1,050 kg of liquid propellants (MMHand N204). The apogee kick motor hasa thrust of 400 N. There are 14 thrustersof 10 N each for attitude and orbit cor-rection manoeuvres. structure subassembly-this weighs
181 kg, and is a modular combi-nation of a communications unit, a ser-vice module, and a propulsion module thermal control-this part of the
Spacebus 300 platform utilizesabout110 m of heat pipe with a dissipation ca-pacity of 1,400 \V to ensure an evenoperating temperature of the TWTs.
The footprint of TV SAT -1 covers alarge part of central Europe, so thatsmall dishes may be used for individualand/or community reception:
DishLocation EIRP diameter
Germany 64.0 dBW 35-40 cmVienna 61.5 dBW 45 cmParis, Lyon 60.0 dBW 50 cmLondon, Rome 57.0 dBW 70 cmStockholm,Warsaw 57.0 dBW 70 cm
Reference: ECS-1 boresight EIRP is42.5 dBW.
The above figures are based on:I. TV picture grade 4.0, corresponding
to C/N =13 dB2. LNB noise figure: 3.0 dB3. additional atmospheric attenuation:
1.5 dB4. satellite pointing error: 0.05°.
The positioning and testing of TV SAT -1
EE
January 1988
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,1-SII suns sow Isde mut Ssmuzz
is expected to be completed next month.The Deutsche Bundespost has an-nounced that all transmissions viaTV SAT -1 will be in the D2 -MAC for-mat, so that earlier rumours of tests inPAL are false. Meanwhile, the GermanTV industry is busily engaged in pro-viding equipment for direct reception ofTV SAT -1. Notably set -top convertersand transcoders for the new D2 -MACstandard pose problems, since ITTSemiconductors have only recentlystarted the production of a suitabledecoder chip Type DMA2270.
Many abbreviations and technicaldenotations used in this report are ex-plained in:
Satellite TV reception. Elektor Elec-tronics, September 1986.The MAC system. Elektor Electronics,July/August 1987.
Note: just before this issue was sent tothe printers, the control centre at Ober-pfaffenhofen reported difficulties un-folding one of the wings of the satellite.
BASYS outstrips competitionSixteen television and radio stations inthe USA and Canada, fourteenEuropean, and three Australian news op-erations have purchased BASYS news-room computer systems since last year'sannual Radio & Television News Direc-tors Association convention. In ad-dition, Jefferson Data Systems-JDS-of the USA, which markets BASYSnewsroom under licence, has contractedfor nine other installations throughoutthe USA.This sales performance has securedBASYS's position as market leader innewsroom computer systems with a totalof more than 120 installations in tele-vision and radio newsrooms worldwide.Moreover, the appeal of BASYS equip-ment is broad -based: radio and tele-vision new brooms regardless of marketsize have chosen BASYS as the most per-fectly suited to their needs.BASYS International Ltd 45 Mor-timer Street LONDON W1V 1PF Telephone 01-631 0286.
Marconi equipment for HongKongAn export order valued in excess of £1million has been awarded to MarconiCommunication Systems by Cable &Wireless (Hong Kong) for the upgradingof the Hong Kong 4 satellite groundstation.Under the terms of the contract, Mar-coni will upgrade the transmit system ofthe terminal, thereby facilitating thetransmission of Intermediate DataRate-IDR-carriers. This internationaldigital satellite communication service,recently introduced by INTELSAT, pro-vides for the transmission of data atrates of up to 8.44 Mbps.
6,000 INMARSAT usersA new Polish cargo vessel, m.v.Wladislass, Gomulka, has become the6,000th user commissioned into the IN-MARSAT global mobile satellite com-munication system.INMARSAT is the 48 member -countryco-operative that operates a system ofnine geostationary satellites to providemaritime, and soon aeronautical, mobilesatellite communications. Services of-fered on the INMARSAT system includetelephone and voice communications,telex, data, facsimile, and slow -scan tele-vision.
Space system now has20 coast earth stationsThe new coast earth station at Maadi,which came into service last October, isthe 20th to provide maritime communi-cations through the satellite network ofINMARSAT.The Maadi station, owned and operatedby the Egyptian National Telecommuni-cations Organizat ion-ARE NTO-isthe first on the African continent. It islocated on the outskirts of Cairo andwas officially opened by the PrimeMinister of Egypt, Mr Arta Sedky.With its 13 -metre diameter antennafocused on INMARSAT's satellitestationed over the Atlantic Ocean,Maadi is capable of providing high -quality, reliable telephone and telex ser-vices for shipping in the Atlantic,Mediterranean, and Persian Gulf areas.For the provision of distress and safetyservices, it will be interconnected withthe Middle East Rescue Co-ordinationCentre near Cairo.Consideration is also being given toequipping Maadi for satellite communi-cations services to aircraft, which willbecome available via INMARSAT laterthis year.International Maritime Satellite Organ-ization 40 Melton Street LON-DON NW1 2EQ.
Four -nation collaboration onoptical fibre systemsFour European companies are col-laborating in the development of2.5 Gbit/s optical fibre systems that cancarry vast quantities of data, video traf-fic, and telephone conversations. Insimple terms, this represents 40,000 tele-phone calls over two hair -thin glasfibres. With the development of broad-band integrated services digital networks(B-ISDNs) and managed local andnational optical networks, such veryhigh capacity optical fibre systems willfind widespread application in the tele-communications networks of the 1990s.The firms are GEC Network Systems ofBritain, ANT NachrichtentechnikGmbH of Federal Germany, SocieteAnonyme de Telecommunications (SAT)of France, and Telettra, Telefonia Elet-tronica e Radio SpA, of Italy. The pro-ject has been given EUREKA status,which is a framework for promoting col-laborative, advanced -technology pro-jects and exploiting research among 18European countries and the EuropeanCommission.
SOFTWARE UPDATE FORUNIVERSAL EPROM EMULATOR
Judging from the reactions of a greatmany of our readers, the universalEPROM emulator (reference "9 is awell -liked construction project for ad-vanced microcomputer enthusiasts. Un-fortunately, a transcription error wasmade on the suggested layout for thefront panel shown in Fig. 6. The follow-ing switch indications on the front panelshould be interchanged: SI and S3; S4and S5; S6 and S7. The correct switchdenotation is shown in the accompany-ing layout of the front panel. Please notethat the front panel foil is not availableready-made through the Readers Ser-vices.
As to the 8748H resident controlprogram for the emulator, it was foundthat an update may be required for thespecial data transfer formats of Intel,Tektronix and Motorola. In the examplesgiven in Fig. 4, the addresses at the be-ginning of each line are always con-sidered as absolute for a simulatedEPROM addressed from 0000H on-wards. This means that the simulator ig-nores the actual address in the targetsystem. In other words, it does not takeinto account that a simulated 2764 canbe adressed at, for example, 6000n to7FFFH, but equally well at E000H toFFFFH in the target system. TheEPROM simulator considers thesimulated memory block invariablylocated between 0000H and IFFFu.Likewise, a 2732 is invariably addressedbetween 0000H and OFFFH. TheEPROM emulator, therefore, reports anerror upon receipt of an address higherthan 7FFFH from the host system,because 7FFFH is the highest availablelocation in the 32 Kbyte RAM, corre-sponding to the capacity of a Type 27256EPROM (see Fig. 3). Thus, when thereare adrresses higher than 7FFFH in, say,a file to the Intel format, the simulatorrefuses to load these although there isessentially nothing wrong with the dataor the format. In general, therefore, thelowest address in the simulated EPROMmust always be 0000H when either oneof the special transfer formats is used.Consider the following example relevantto the Intel file format:
:02 00 10 00 A9 IF 26 ...:00 00 00 01 FF
In the simulated EPROM, the databyteA9H is at address 0010H, and thedatabyte 1FH at address 0011H. If thisEPROM, regardless of its capacity, isaddressed starting at, for example,
E000H in the target system, theassembler generates a data block to theIntel format that looks like this:
:02 E0 10 00 A9 IF 26 ...Consequently, the EPROM emulatorwill not load this file, because it com-prises EPROM addresses higher than7FFFH.
This, admittedly serious, shortcoming inthe simulator software can be traceddown to the use of the 2 assemblers usedfor developing and testing the EPROMsimulator in our design department. Theassemblers offer the possibility of speci-fying an offset which is automaticallyadded to the originate (ORG) addressesin the assembled object code. The aboveproblems in loading files with startingaddresses higher than 7FFFH weresimply not encountered becauseassembled data blocks with an ORG ad-dress of, say, E000H were automaticallyassigned an offset of 2000H during theconversion to the Intel format. Theresult is that the blocks sent by the hoststart invariably at 0000, since E000H +2000n = 0000H.To help those users wishing to use the In-tel, Motorola or Tektronix formats inconjunction with an assembler that doesnot feature the previously described off-set facility, a special updating service isavailable for programmed 8748Hs sup-plied by Elektor Electronics. Interestedusers are advised that the correctionsand additions to the contents of the8748H are effected without replacing orerasing the device: the relevant bit lo-cations reading 0 are simply changed(programmed) to 1. In short, the up-dated software masks the addresses in
the special formats with the highest ad-dress of the EPROM in question, count-ing up from 0.
The update described here is not strictlyrequired for the standard binary format.This mode of the EPROM emulatorcontinues to be usable alongside thespecial formats used in conjuction withan assembler that provides for an auto-matic offset.
All 8748Hs supplied by us after1 November 1987 contain the update de-scribed here (ESS 558-A).Users wishing to avail themselves of thefree update service may send in their8748H, duly packed, with a stamped andaddressed return enevelope, to
Elektor Electronics Software Service1 Harlequin Avenue Great West
Road Brent ford Middlesex TW89EW.
Microcontrollers Type 8748H without anoriginal adhesive from Elektor Elec-tronics are not accepted for updating.Th
Reference:
") Universal EPROM emulator. ElektorElectronics, September 1987, p. 54 ff.
IELEKTOR EPROM EMULATOR
S3 S2 51 EPROM SS 54 FORMATo o 0 2708 o o INTELo o - 2716 o - BINARYo - o 2732 - o MOTOROLAo - - 2764 - - TEKTRONIX- 0 o 27126- o - 27256
S7 S6 BAU0FLATEo o 1200o - 2400- o 400- - 9600
o = OPEN -=CLOSED 58 = NC
sv RoT
0
RE:.: - -0
RESET
RS 232-
CENTRerCCS
0
EE
January 1988
NEW LITERATURE NEW LITERATURE NEWElectrical and ElectronicEngineering Principlesby J.O. BirdISBN 0 582 41399 0134 pages - 185 x 122 mmPrice f2.95 (soft cover)Few, if any, of us can remember morethan the most often used formulae andgraphical symbols connected with elec-trical and electronics technology. Elec-trical and Electronic Engineering Prin-ciples should, therefore, be of interest toall involved in electronics, more particu-larly students and staff in colleges,polytechnics and universities, but alsotechnicians and engineers in industriesinvolved in electrical and electronicengineering.The aim of the booklet is to present aready reference guide to the most :com-mon quantities, units, symbols, defi-nitions, formulae and circuit diagramsymbols used in electrical and electronicengineering. In my opinion, the authorhas succeeded in meeting this aim.A useful, inexpensive book that will, nodoubt, be welcomed by anyone with aninterest in electronics.Longman Scientific & TechnicalLongmanBurnt MillHARLOW CM20 2JE
BRITISH STANDARDSBS9000:Part 3:1987This new part of the General re-quirements for a system for electroniccomponents of assessed quality detailsthe implementation in the UK of theIEC quality assessment system for elec-tronic components (IECQ) by showinghow the IECQ rules of procedure,clauses 10 to 16, are implemented inBS9000:Part 1. It came into effect on 31July 1987.
BS6600:Part 1:1987This part of the new Outline dimensionsof transformers and inductors for use intelecommunication and electronicequipment specifies the outline dimen-sions of transformers and inductorsusing E and I laminations, built for thefour most commonly used forms ofmounting style, namely bracket mount-ing, U -clamp mounting, printed wiringboard (p.w.b) mounting, and framemounting. It came into effect on 31 July1987.
British standards may be ordered fromThe Sales DepartmentBSILinford WoodMILTON KEYNES MK14 6LE
Readers should note that each County inthe UK has at least one or two largeLibraries that keep complete referencesets of British Standards for general con-sultation.
CATALOGUESTHE 1988 GREEN 'VELD ELEC-TRONICS COMPONENT A N DEQUIPMENT C47:4 LOGUE isavailable at £1.00 from Greenweld 443E Millbrook Road SOUTHAMP-TON SOl OHX.
Cirkit's electronic constructor'scatalogue (Winter 1987/8) is available at£1.20 from Cirkit Holdings PLC ParkLane BROXBOURNE EN10 7NQ.
Electroplan's Rental Catalogue 1987/88,detailing an expanded range of equip-ment available on short- or long-termhire is available free from ElectroplanRental P.O. Box 19 Orchard Road ROYSTON SG8 5HH.
Norway Exports - Telecom-munications TechnologyThis new survey details high perform-ance products and systems designed tomeet the advanced communicationneeds of modern industrial societies andhighlights the impact being made byNorwegian companies internationally inthis field.The 16 -page full -colour booklet isavailable free of charge from The ExportCouncil of Norway Norway TradeCentre 20 Pall Mall LONDONSW1Y 5NE.
.y.621/ lnputlOutput Modules
Grayhill's Input/Output Modulescatalogue is available free from GrayhillInc. 561 Hillgrove Avenue P.O. Box10373 LaGrange Illinois 60525 USA.
Microelectronic Systems & Instrumen-tation, a 44 -page full -colour catalogue,is available free from Flight ElectronicsLtd Flight House Ascupart Street SOUTHAMPTON SOl 11,11.
A six -page, full -colour guide to one ofthe world's largest continuous operationflowmeter and valve calibration facilitiesis available from Kent IndustrialMeasurements Ltd Oldends Lane STONEHOUSE GLIO 3TA.
A semiconductor dice selection guidecontaining full and abbreviated data onthe Ferranti range of planar, discrete,and integrated semiconductors in unen-capsulated dice and wafer form isavailable free of charge from FerrantiElectronics Ltd Fields New Road Chadderton OLDHAM OL9 8NP.
A new and expanded European RegionSoftware Directory, listing some of thethousands of commercial applicationswritten in Micro Focus COBOL isavailable from Micro Focus Ltd 26West Street NEWBURY RG13 1JT.
24 EE
DCF77 RECEIVER AND LOCKEDFREQUENCY STANDARD
The extremely stable signal from the VLF time standard transmitter DCF77 in Ivlainflingen, WestGermany, can be received in most European countries, and is eminently suitable for controlling an
advanced, locked frequency standard offering a stability of 0.5 ppm.
DCF77 is an AM, 25 kW (ERP), VLFtime signal transmitter operating on77.5 kHz. The station is located inMainflingen, near Frankfurt am Main,in West Germany (co-ordinates: 50° 01' N,09° 00' E). The station is operated by theDeutsche Bundespost, but the Physika-lisch-Technischen Bundesanstalt (PTB)in Braunschweich is responsible for thestability of the carrier and the timesignals, which are used in many labora-tories and scientific institutions for ac-curate timekeeping purposes. The rangeof DCF77 is claimed as 800 kilometres.The stability of the carrier is derivedfrom a caesium atomic clock with anaverage deviation of 2 x 10-u over aperiod of 100 days. The time signalsfrom DCF77 are not the main concernhere, however, and a detailedof their structure will be given in a forth-coming article in Elektor Electronics.DCF77 transmits in AM at a modulationdepth of 75%. This is in contrast to theRugby MSF on 60 kHz-in this station,the carrier is switched off completelyduring pulse modulation. This unfortu-nate fact makes Rugby unsuitable forbuilding a locked frequency standard asdescribed here. In addition to the AMtime signals, DCF77 transmits a numberof phase modulated services.The block diagram of Fig. 1 shows howthe 77.5 kHz carrier is used for keepinga crystal oscillator stable at 10.000 MHzwith the aid of a phase locked loop(PLL). The oscillator signal can be usedas an accurate clock for a wide range ofequipment. The 10 MHz oscillator signalis divided by 128 to give 78.125 kHz.This signal is heterodyned with the77.5 kHz carrier from DCF77 to give anintermediate frequency of 625 Hz. Theoscillator signal is also divided down to625 Hz through subsequent division by32, 125 and 4. The two 625 Hz signalsare applied to a phase comparator,which provides an error signal for con-trolling the frequency of the 10 MHz os-cillator.
Circuit descriptionThe circuit diagram of the active aerial isgiven in Fig. 2a.This small unit is constructed in a man-
ner to facilitate fitting it in a locationwell away from noise sources. The con-nection to the receiver is made inscreened or thin coaxial wire. The VLFaerial itself is a parallel tuned circuit,Ls -C34, resonating at 7-7.5 kHz. The RFsignal induced in the tuned circuit ismagnified in a source follower, T13, anda further amplifier, Tis. FET Tit func-tions as a current source to achieve opti-mum bias for T13. Preset Pa enablessuppressing oscillation of the sensitiveamplifier. It forms part of a damping re-sistance across Ls -C-14, and hence deter-mines the quality (Q) factor of thistuned circuit. The active aerial is fed bythe supply in the receiver via the core ofthe downlead cable.An optional 77.5 kHz hand -pass filtermay be inserted between the active aerialand the receiver input to limit the overallbandwidth and thus cope with signal im-pairment caused by interference. Theband-pass is discussed further on in thisarticle.
The circuit diagram of the receiver inFig. 2b shows that the VLF signal fromthe active aerial is filtered in networkLi -C3 -C4 and then applied to gate 1 ofdual gate MOSFET Ti, which functionsas a mixer. The transistor is switchedhard at 78.125 kHz because the signal atoutput Q7 of divider IC3 is applied togate 2. The resultant heterodynedfrequency -625 Hz-available at thedrain is fed to a gyrator, T2 -Cs -C9,
which ensures high local amplification.The DC setting of Ti is controlled bythe (negative) AGC potential applied togate 1. The 625 Hz signal is filtered in a700 Hz low-pass section Rs-Cio-R9-C12-
Rio-Cii-T3 and a 550 Hz high-pass sec-tion C13-Rn-C14-R12-05-R13-Ts. Transis-tors 14 and T6, and resistors Rua andRio, provide the bias for the activefilters. Alternating voltage amplifier ICIis dimensioned for an amplification ofabout 100.The signal provided by ICI is fed to 4sections of the circuit.
Fig. 1. Block schematic diagram of the DCF77 receiver and locked 10 MHz frequency stan-dard.
EE
January 1988
2
(>2-3V Cala 0.1-3-2-3V(>11-4--13" 6F255C
TA
35124.1.24
I
BC434
TP
770,04
41/74000M
73
4700
a
BC550C
10n I 100 I 100
1
BF256A
T5
TP313
TR
RTC
BC550C
RIS
I CIS
mpl11e1
BF256A
47
03
AA119
70
2xBC5ECC
IC2504ZP
15'1
RIR
1116 11" R22
tsa
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IC3 IC44024 -C" 40103 CO
a . es ed 0
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112 i n1 91
so 0 MX 00 -0c a
ri FF1 FF2
R S.71=
AA119
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711
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C35 I CIS R46
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FF1,FF2=105=4013Bz 1 Hi-M=1M = mna
bbbbIC3 - ICI- IC5 ICEI
15V
S5124-1-26
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Fig. 2. Circuit diagram of the active aerial (a), the receiver plus PIA, based 10 MHz frequency standard (b), and the power supply (c).
26 EE
January 1988Symmetrical mixer IC2 is set up as ananalogue PLL. This circuit has the dis-advantage of reducing the bandwidthalong with the signal-to-noise (S/N)ratio of the input signal, but thispresents no problems as long as the PLLremains locked. This feature is in con-trast to a digital PLL, which would loselock as a result of strong spurious pulsesand a reduced S/N ratio. The 625 Hzsignal obtained from ICI is limited by a"soft" clipper, Di -D2, and its phase iscompared to the complementary signalsQ and Q from FF1, applied to the sym-metrical inputs of the S042P. The phaseerror signal at pin 2 of the mixer isfiltered in low-pass R22 -Cm, and formsthe control voltage on varactor set D4.The output of the 10 MHz oscillator isthus corrected for minimum-theoreti-cally, zero-phase difference betweenthe heterodyned 625 Hz signal and the625 Hz reference from the timebase: inother words, the central clock circuit isforced to oscillate at 10.000 MI-lz pre-cisely.The output of ICI is also rectified by D3to obtain an AGC (automatic gain con-trol) signal which is fed to gate 1 ofmixer Ti via voltage limiter Rai -D5.Next, the output of ICI is fed to recti-fier D --C22, which provides the referenceat the ± input of comparator IC6.Sample and hold transistor TH drivesthe - input, and toggles along with the625 Hz reference for the phase compara-tor. The time signal from DCF77 isavailable for a clock circuit at output T.The 4th circuit driven by the output ofICI is an acoustic and digital error indi-cator. The output signal of N2 and thereference signal of the phase comparatorare applied to the inputs of XOR gateM, whose function is best compared tothat of a digital mixer. The amplitude ofthe signal obtained from filter R39 -C36 isa measure of the phase difference be-tween the heterodyned and the reference625 Hz signals. The inputs of gate N4are at different logic levels when thephase difference is such that the PLLloses lock. Piezo buzzer Bzi gives anaudible warning of this condition, andIC7 arranges for Ti: to short-circuit the10 MHz output signal. The digital errorsignal at output E can be used forswitching to the internal, free -running,timebase of a frequency meter when the10 MHz standard loses lock owing to im-paired reception of DCF77. It should benoted that the buzzer is not an absoluteindication of the quality of the receivedsignal; it may, therefore, produce inter-mittent sounds to give an early warningof increasing interference.At the heart of the circuit is the varactor& crystal controlled 10MHz oscillator.MOSFET Tio functions as a buffer andlevel adaptor for driving divider 1C3.The 15 Vpp, rectangular, 10 MHz signalis unsuitable for putting on a long coaxcable to the timebase input of external Fig. 3. Component mounting plan ()I' the doubleided. ready-made PCB.
test equipment. It is, therefore, first at-tenuated and then filtered. Terminated in50 Q, the 10 MI-lz output of the circuitsupplies a sinusoidal signal of 750 mVpp.The stability of this signal is approxi-mately 0.5 ppm.The divider cascade for the referencesignal is of conventional design. TheType CD4024BE in position ICs caneasily handle a rectangular input signalof 10 MHz, and the Type 40103 pro-grammable counter in position IC4 ishard wired for division by 125.The power supply for the receiver/fre-quency standard is shown in Fig. 2c.This simple circuit merits no further dis-cussion.
Construction and alignmentBefore embarking on this project, con-sider the following important points:
1. The construction and alignment ofthe DCF77 receiver and frequency stan-dard requires accuracy in soldering, andconsiderable experience in dealing withRF circuits.2. A sensitive oscilloscope, a digitalmultimeter and a function generator arenecessary for alignment and, if required,troubleshooting.3. Before ordering the ready-made PCBfor this project, it is strongly rec-ommended to check whether DCF77 canbe copied locally on a good quality VLFreceiver. Alternatively, experienced con-structors should have little difficultybuilding the active aerial experimentallyon a piece of veroboard, and measuringthe output signal with the aid of an os-cilloscope. The RF output amplitude isof the order of 5 to 50 !Winn4. A number of try -outs have shownbeyond doubt that the present project is
Parts list
Resistors (±5%):
RI;R2;R4s= 68R1,13;R5;R7;Rte;Rz5;R2e;Rze;Rao;R31 =220KR4= 1M0R6 =680KRc;Re;Rto;R47 = 100KRT i;RIE;R19;R33;R34= 22KRtz=10KRi3;R14=330K815= 2K21317=470RRzo;1121;1324;R32;R4o:R41;R46=1K0F122=22OR
1323;1139=47K
R27= 56RR26=5608R35;R36= 10MR36= 3K3R37= 1K2R42:R43= 12KR44 = 6K8
R45= 2K7R.:9=150RR50 = 220K
Pt =10M preset HP2=2M5 or 2M2 preset H
Capacitors:
Ci:Ca=471x; 16 VC2= 5n6C3=80 p trimmerC4=56 pCe;C7:C13;C14;C1e= iOnCs= 560nCe;C t7:C26;Ca4 = 47nCto=3n3CII:C23:C24 = 470pCtz=8n2Ci6;C1s;C45=4p7; 16 VCle=47p; 10 VCzo=470p; 16 VC21;C22 = 150nC25= 100pC27;C31= 1n0C28;C29 = 220pC30;C35;C36;C39= 220nC32= 22nC33;C41 = 14; 16 V
C37;C38;C42;C43= 100nC40= 1000p; 40 VC44= 2n2C46= 1000p;16 V
Inductors:
Li =33 mH radial choke Toko Type 181LY-333:Cirkit stock no. 34-33302.
1_2;1_4=2pH7
L3 = 3pH9L5= home made inductor: see text
Semiconductors:
Dt;D2=1N4148133;D6.. _De incl. = AA119D4=136212Ds= zenerdiode 4V7; 0.4 WDm... 013 incl.= 11'44001TI;Tio=BF981T2;T3:Ts:T1i;Tts=BC5.50C
T 4 = 6F256A1-7; T5 = 6C560C
Te;T12=E1F494113 = 8F256CICI =153561C2=S1342P1C3=4024BE or HEF4O24BIC4=40103IC5=40131C6;IC7=CA3130EICe=4030ICs= 7815
Miscellaneous:
St = DPDT mains switch.Ft = fast acting 50 mA fuse plus panel mount
holder.Int = mains transformer: 18 V; 100 mA.X1= 10 MHz quartz crystal (CL=30 pF; parallelresonance; HC18 enclosure).
Bzt = passive piezo buzzer.PCB Type 8612-A (available through the
Readers Services).10 cm long ferrite rod (010 mm).Paxolin or cardboard former 012 mm.Enamelled copper wire 30.2 mm 1S1NG36).
Parts and veroboard for the optional 40 Hzbandpass (not on ready-made PCB).
EE
January 1988.unsuitable for beginners.5. DCF77 is normally operated on a 24hour basis, but the station is switchedoff during transmitter or aerialmaintenance work, and also duringthunderstorms.6. Forthcoming articles in Elektor Elec-tronics will discuss these advanced pro-jects that require the present re-ceiver/frequency standard: a 8052AH-BASIC based, menudriven, central clock unit with an in-telligent LC display and a serial time anddate output; a 8748H based slave indication unit.7. A divider cascade which accepts the10 MHz reference signal, and outputsstandard timebase frequencies, is pub-lished in the new Elektor Electronicsbook 303 Circuits.
The track layout and the componentmounting plan of the double -sided, butnot through -plated, PCB for the re-ceiver/frequency standard is shown inFig. 3.Commence the construction with cut-ting off the section of the board in-tended for the active aerial. Inductor L5is wound on a 50 mm long, round card-board or paxolin former and a diameterof about 10 mm to enable sliding it on a12 cm long ferrite rod. The former andthe rod may be cannibalized from adiscarded MW radio. The inductor iswound as 200 turns of 0.2 mm dia.(SWG36) enamelled copper wire. Tem-porarily secure the winding withSellotape, but do not secure the formeron the rod as yet. The completed activeaerial is shown in Fig. 4. The PCB-notthe ferrite rod! -may be fitted in ametal enclosure.Many components on the receiver boardare fitted upright, and require solderingat the track side and the componentside to effect through -contacting. Theunetched copper surface on the compo-nent side funtions as a large groundarea. Populating the board with the aidof the parts list and the indications onthe component overlay is fairly straight-forward, with the possible exception ofthese points:
1. Ascertain the position of MOSFETsTi and Tie with the aid of the pin -outsdiagrams shown in the circuit diagram.Depending on the make of these devices,it may happen that the type indicationmust face the board surface!2. The short lead of vertically mountedresistors R3= and R50 is soldered at thecomponent side also.3. Regulator IC9 is fitted without aheat -sink.4. All ICs should be fitted in sockets.
Do not yet connect the completed re-ceiver board to the active aerial. Connectthe secondary of the mains transformerto the AC input on the board, and con-
28 EEJanuary 1988
4
Fig. 4. The ferrite rod is secured to the active aerial board with plastic cable ties.
nect an AF amplifier or headphones toTP1. Set the trimmers and presets to thecentre of their travel. Apply power: thepiezo buzzer should then produce an ir-regular, crackling sound, and the AFamplifier soft, steady noise. Check thepresence of the supply voltage on all therelevent points, and use an oscilloscopefor finding the rectangular signals in thedivider chain.Connect the active aerial to the receiverwith about 1 metre of screened wire orthin coaxial cable (RG174/U). Preset P2on the active aerial board is turned fullytowards R47. Check the voltages onpoints A, B and C.Set a function generator to 77.5 kHz,sine -wave, 1 Vpp out, and fit a 1 kg re-sistor in series with a test lead connectedto the generator output. Wind the testlead loosely onto one end of the ferriterod, and slide the paxolin former withthe inductor on it across the rod to finda point where a voltmeter connected toTP2 (AGC) reads a minimum (i.e., maxi-mum negative) voltage. It is, of course,also possible to look for the 77.5 kHzsignal at the output of the active aerialwith the aid of the oscilloscope, but theamplitude of the signal on the downleadis still quite small (5-50 mVpp). Reducethe output amplitude on the functiongenerator, and peak C3. Reduce thecoupling of the test lead by moving thisaway from the inductor on the ferriterod. Reposition the inductor for opti-mum "reception" of the induced77.5 kHz signal. The best results are ob-tained when the inductor is approxi-mately central on the rod. Should opti-mum reception occur when the inductoris partly off one end of the rod, it isnecessary to reduce the number of turnson a trial and error basis. Keep reducingthe RF input to the receiver by adjustingthe generator output and/or increasingthe distance between the test lead andthe ferrite rod. Find the optimum pos-ition of the inductor, and re -adjust C3(measure the received signal on gate 1 of
Ti). Carefully advance P2 until theamplifier in the active aerial is observedto start oscillating. Turn the wiper backuntil oscillation just stops: this settingensures maximum sensitivity. It shouldbe noted that oscillation may not occurat all cases. Check the selectivity of theactive aerial by monitoring its outputsignal on the scope and tuning the gener-ator a few kilohertz around 77.5 kHz.Switch off the function generator, androtate the ferrite rod in the horizontalplane until the piezo buzzer graduallystops crackling. This indicates that thePLL locks onto DCF77. Optimize theinductor position, and once more peakC3 and P2 for the highest negative AGCvoltage on the anode of D3. The ampli-tude of the 625 Hz signal at the outputof ICI should be greater than 1 Vpp.Secure Ls on the former, and the formeron the ferrite rod.Connect the oscilloscope to output T,and rotate the aerial horizontally untilthe buzzer indicates that the PLL is onthe verge of losing lock. Reception canalso be disturbed by touching gate 1 ofMOSFET Ti. Adjust the triggerthreshold of comparator IC6 with theaid of Pi for minimum noise pulses onthe scope. Check the amplitude of the10 MHz sinewave at the output of thecircuit-see Fig. 5.The buzzer normally produces a softregular hiss, and the time signals are alsoaudible. The phase modulationemployed on DCF77 is clearly visible ona scope connected to TP1. Listen to themodulated 625 Hz signal at this point tonote the fairly strong background hisscaused by the PM services. In general,the more noise from the buzzer, theworse reception.
An add-on bandfilter fordifficult casesFigure 6 shows the circuit diagram of aband-pass filter with a -3 dB bandwith
of about 40 Hz ( -40 dB: 1400 Hz) anda gain of 10 dB. This circuit may be in-serted between the output of the activeaerial and the receiver input as shown inFig. 1. The selectivity of the bandfilter isobtained from 2 L -C networks, LI-CI-Csand L2 -C2 -C4, with capacitive top coup-ling (C3). The loaded Q (quality) factorof this filter is ensured by the use of dar-lington transistor Ti. Negative feedbackis provided by T2 and R -C network R5-
PI -C6. The bandwidth of the filter is setby Pi. The feedback circuit causes a re-duced input impedance for frequenciesoutside the pass -band, and so improvesthe dynamic range of the active aerial.The add-on circuit is readily constructedon a small piece of veroboard. It is rec-ommended to use 5% or 2.5% poly-styrene (styroflex) capacitors as indi-cated in the circuit diagram. InductorsLi and L2 are formed by as 102 and105 turns of 00.2 mm (SWG36) enam-elled copper wire, respectively. Thepotted cores are Siemens TypeB 65541 N400 A48 (ElectroValue: Tele-phone (0784) 33603 or (061 432) 4945).The inductance span of these adjustablepotcores is fairly small, and the statednumber of turns may have to be alteredslightly to ensure resonance of the tunedcircuits at 77.5 kHz.The adjustment of the bandfilter is car-ried out with a correctly functioning andfully operational DCF77 receiver. Set Pifor maximum resistance, and fit the cir-cuit in the downlead cable between thereceiver and the active aerial. Check thevoltages on the test points in the activeaerial. Use a sensitive oscilloscope topeak Li and L2 for resonance at77.5 kHz. Then carefully adjust Pi upto a point where the circuit starts clip-ping the time pulses.
An applicationThe circuit diagram of Fig. 7 shows thenew, DCF77 based, 10 MHz clock sourcefor the microprocessor controlled fre-quency meter discussed in reference (".The circuit is essentially a discrete PLLconstructed on a PCB that replaces the
Fig. 5. The 10 MHz signal at CMOS level(lower curve; 15 Vpp), and at the output ofthe frequency standard (upper curve;750 mVpp in 50 4).
Fig. 6. Cicuit diagram of the optional add-onhandfilter.
Fig. 7. Circuit diagram of the PLL based10 MHz clock circuit for the microprocessorcontrolled frequency meter.
Fig. 8 The PCB for building the new 10 MHzfrequency meter (not available ready-made).
Parts list
Resistors (±5%):
R1=68KR2= 1K2
R3;R4;Re=270KR5=47KRs = 1K5R7 = 390RRs=22K
Capacitors:
Ci =20p trimmerCz;Ca =470pC4 =39nC5=100n
Semiconductors:
01:D2=138105BTI;Tt =8F494ICI = 74HC861C2 = 74HC74
Miscellaneous:
X 1 =10 MHz quartz crystal la =30 pF; parallelresonance).
PCB Type 87105 (not available through theReaders Services).
404' Lx:
11'
- 41k_,fiti )! '
c '
r -=-",
1-c - -
EE
January 1988existing 10 MHz clock board in the in-strument. The PCB for building thisuseful extension of the instrument isshown in Fig. 8. With reference to Fig. 7,the 750 mVpp 10 MHz reference signalfrom the frequency standard is appliedto amplifier/digital converter Ti.Bistable FF1 divides the signal by 2, anddrives phase detector N2, which formspart of a PLL. A tuneable 10 MHzcrystal oscillator is set up around T2, Xiand varactors Di -D2. Components Rs -R9 -C4 form a loop filter at the output ofthe phase detector, and provide the errorsignal, i.e., the tuning voltage for thevaractors. Gate N3 buffers the oscillatoroutput, and N4 drives the logic circuitryon the main board in the frequencymeter. The function of FF2 is similar tothat of FF1.In the absence of an input signal fromthe frequency standard, FF1 stops tog-gling, and remains in its previous logicstate. Bistable FF1 is still active, how-ever, so that N2 continues to supply asymmetrical rectangular signal, and thePLL control voltage on Cr rises toabout half the supply potential. In orderto ensure minimum PLL action in theabsence of the DCF77 signal, trimmerCi is used for adjusting the VCO fre-quency such that the tuning voltage hasa small control span centred around+ 2.5 V.The following adjustment procedure as-sumes a correctly operating receiver/fre-quency standard, and loud and clearreception of DCF77. Switch on all unitsand allow a few minutes for warming up.Use a high impedance DMM to measurethe voltage on C4 (TP). Slowly adjustCi until the meter reads +2.5 V. Wait10 minutes or so to observe the trend ofthe reading, and redo the adjustment ifrequired.
Reference:
29
The fully assembled receiver plus frequency standard. Details on fitting it in an enclosure willbe given next month.
"' Microprocessor controlled frequencymeter. Elektor Electronics January 1985.
30 EL.
SWITCH MODE POWER SUPPLYFollowing the general introductions into the operation and application of switch mode power supplies in
reference (1) and (2), this article discusses a practical design of a versatile, compact and highly efficientSMPSU rated at 2.5 A.
The circuit described here is basedaround the integrated switch modepower supply controller Type L4960from SGS. Briefly recapitulating thegeneral introduction in reference (2), thisIC has the following features:
Input voltage range: 9-50 VDCO Output voltage adjustable between 5
and 40 V. Maximum output current: 2.5 A.IN Maximum output power: 100 W. Built-in soft start circuitry.111 Stability of internal reference: ±4%. Requires very few external compo-
nents. Duty factor: 0-1.II High efficiency: ri up to 90%. Built-in thermal overload protection.El Built-in current limiter for short-
circuit protection.
The pinning of the 3 regulators in SGS'sL496X series of switch mode regulatorsis shown in Fig. 1. The Type L4964 ishoused in a special 15 -pin enclosure, andcan supply up to 4 A. The Type L4962is the least powerful version (1.5 A),housed in a 16 -pin DIL package.The internal organization of the TypeL4960 has been discussed with referenceto Fig. 1 in 0). The operation of the on -chip soft start circuitry, and the currentlimiter, is illustrated by the waveformdiagrams in Fig. 2a and 2b, respectively.The thermal shutdown circuit in theL4960 is activated when the chip junc-tion temperature exceeds 150 °C.For the sake of safety, the proposedSMPSU is a transformer based design.The alternating input voltage to theboard is obtained from the secondary ofa mains transformer, which ensures thatthe DC input to the regulator is at least3 V higher than the required outputvoltage at the maximum output current.It goes without saying that the trans-former is preferably a toroidal type.
Circuit descriptionFigures 3a and 3b show the circuitdiagram of the mains section, and theDC power supply, respectively. The alter-nating voltage from the secondarywinding is applied to the respective in-puts on the supply board, while thecentre tap is connected to ground. Theunregulated input voltage, U., for theL4960 is supplied by a full -wave rectifier
circuit composed of two 3 A diodes Type1N5404, Dl -D2, and an electrolyticreservoir capacitor, Ct. Network RI -C3 -C4 defines the gain of the closed regu-lation loop. A second network, C2 -R2,is dimensioned for an oscillator fre-quency of about 100 kHz. The functionof capacitor Cs is twofold: it defines theperiod of the soft start ramp (see Fig.2a), as well as the average short-circuitcurrent. The feedback input of the regu-lator is connected to the junction of out-put voltage divider R3 -R4.The output voltage, U0, of the L4960 iscalculated from
U.=5.1[(R 3 + R4)/R3] assuming thatU.-U.a.-3 V.
Remember that the minimum value ofU1 is 9 V. A fixed output voltage of5.1 V (±4%) is obtained when R3 isomitted, and R4 replaced with a wirelink. When R3 has the fixed value of5K6, R4 alone determines the outputvoltage:
U0=9 V: R4 = 4K28U0=12 V: R4 = 7K58U0=15 V: R4 = 10K87U0=18 V: R4 = 14K16U0=24 V: R4 = 20K75
These resistor values are, of course,theoretical, and require ascertaining inpractice. The output voltage is readily
L4960
itZ.- Tao emanacted to pin I.
L4962
C
OUTPUT
NC
NO
ONO
C
!I Put
T. c [
OUTPUT
SOFT SlamOSCP.Lt04u NO
raEci COMPa FEEDBACK INPUT
INPUT
NC
S SOFT START
rea,PLATOR
3 DUD
DUO
MEC& COMP
1: FEEDBAG,.
C
L4964
Tsn ce.-Tltra <x
C
PC.CS(
T MSIT
CtaiaarNT
mist! P.RITOSCa.L.C.1,ICCaleaca PourFalturlaCa CCP.SaSaT,Ca
tG.Ova9say: MTV,
Vv..TSCVTSTaPT CCPTKit C
880001 - 1
Fig. I. Pin -outs of the integrated switchmode regulators in the L496X series fromSGS Ales.
A prototype of the switch mode power supply. Note that this is set up for U°=5.1 V, sinceR4 is a wire link, and R3 is omitted.
EE
January 1988
2a C5 =Wei.witnorrmat errorarrrp. cutout
ouutCalera
cral,pea cowamp. output
soft startar
580001.2a
currentIrriter
Fig. 2. Operation of the soft start (a) and current limit (b) circuits in the L4960.
3aF1
51
860001-3a
2x1N5404
ti
* see text
0
IDI
02
R4
IC
L 4960
7
5
Cl C2 R2
ami10005 2n240V
C321,240V
*C4 R3
Nam
60.a
03 *A at C7 C6= =
SOOn 2.220540V
8R05 0
Fig. 3. Circuit diagram of the mains section (a) and the switch mode power supply (b).
Parts fist
Resistors ( 5%):
RI =15KR2=4K3R3;84= dimension as required for Uo; see text
Capacitors:
C t =1000p; 40 V; radial (pitch 7.5 mm)C2= 2n2C3= 33nC4= 390pC5= 2p2; 40 V; radial (pitch 2.54 mm)Ce;C7=220,u; 40 V; radial (pitch 5 mm)Ca= 100n
Semiconductors:
DI;D2=1N5404D3=8R05. (SGS-Ates) or BYV28 (Bullard)ICI =L4960. (SGS-Ates)
SGS-Ales (UK) Limited Planar House Walton Street Aylesbury HP21 7()J. UKbased distributors are listed on Infocard 508:EE May 1987.
inductor:
1_1=150...300pH toroid suppressor, e.g.Newport 1400)11/3 or Siemens 882500-B-410 (axial). Home made: approx. 60 turns of
1 mm. enamelled copper wire on a suitablyrated 015-20 mm ferrite core.
Miscellaneous:
T0220 style heat -sink.T0220 style mica washer and bush.In = toroidal mains transformer with centre
tap; ratings as required (see text). E.g. (LPseries: Jaytee Electronic Services 143Rcculver Road Beltinge Herne Bay Kent CT6 6PL. Telephone: (0227) 375254.
PCB Type 880001 (see Readers Services page).
Fig. 4. The printed circuit board for the compact SNIPSU.
made variable by fitting R3=6K8 andreplacing R3 with a 25K potentiometer.Power diode D3 is included as a safetymeasure. This fast rectifier limits thenegative potential at the input of chokeLi to a safe -0.6 to -1 V when theoutput transistor in the reeulator isswitched off. In the absence of D3, thevoltage at pin 7 would increasedangerously to several volts Below theeround potential. Choke Li is an essen-tial part in the L -C network for noise
and ripple suppression at the output ofthe supply.
ConstructionThe compact primed circuit board forthe SNWSLI is shown in Fie. 4. The com-pletion is extremely straight -forward.Start off by selecting resistors R3 and R4as explained above. Fit the componentsin the centre, RI... R4 inclusive andC2. . Cs inclusive. Prior to soldering
111 EE
January 1988onto the board, regulator ICI andpower diode Di are bolted back to backonto a common heat -sink as shown onthe component overlay. Do not forget tokeep the heat -sink electrically insulatedfrom the metal tab of D3 with the aid ofa thick mica washer and a plastic bush.It is possible to use the Type BYV28diode in position D3. This device ishoused in an axial SOD64 enclosure,however, and requires a different mount-ing method than the TO220 style 8R05from SGS. The BYV28 is mounted up-right, but the anode lead is not bentdown until is has been soldered to acable eye. The eye is then insulated andfitted onto the heat -sink as detailedabove. Whatever diode or mountingsystem is used, check the insulation witha continuity tester! Push the leads ofICI and D3 into the respective holes un-
til the heat -sink rests securely onto theboard surface. Solder the leads and cutoff their excess lengths. Now fit the re-maining components, Li, CI, C6, C7, Cs,Di and D2. Be sure to observe correctpolarization of the diodes and the elec-trolytic capacitors. Great care should betaken to avoid any likelihood of a short-circuit between the winding on the chokecore and the heat -sink for the regulator.It is recommended to secure Li with theaid of a central nylon bolt and nut.
TestingCheck the position, insulation andorientation of all the parts on the boardbefore connecting this to the secondaryof the mains transformer. It should benoted that the supply requires a load at
all times for proper operation. When theSMPSU is fed with 30 VAC, and loadedwith 2 A at an output voltage of 5 V, thetemperature of the heat -sink should notexceed about 60 °C at room tempera-ture. The efficiency of the supply underthese conditions is approximately 68%.With a load of 2 A, the efficiency in-creases from 80% at U0=10 V, 85% atUo =15 V, to 87% at at U0=25 V. Gb
References:
") Switch mode power supplies, ElektorElectronics October 1987, p. 49 ff.", High -current switching regulator ICsimplifies supply design, Elektor Elec-tronics October 1987, p. 22 ff.
DOUBLE TRACE EXTENSION FORVLF ADD-ON UNIT
by E Fano
A handful of components and some minor alterations to the VLF add-on unit for oscilloscopes enablethis popular unit to be used for two -channel measurements.
Thanks to its versatility, low cost, andease of construction and use, the VLFadd-on unit for oscilloscopes publishedin reference In has become one of themost popular construction projectsfeatured in Elektor Electronics. The fol-lowing description shows that the circuitis readily modified to achieve two -channel operation on a single -beam os-cilloscope. The required modificationand the extension circuit are useful formany applications involving the simul-taneous analysis of 2 slowly varyingquantities.
Input multiplexing and 256bytes moreIn the original design of the VLF storageunit, address lines A8 to A10 incl. ofRAM IC2 are kept permanently logiclow. This means that only the first 256 ofthe available 2048 programmable lo-cations in the RAM are used for storageof converted data. The idea behind thepresent extension is to drive address lineA8 with a signal that creates an ad-ditional data block of 256 bytes. Thisblock is written to during every seconddisplay-conversion cycle, and can thushold the digitized data for a second in-
put channel. The input signal for opampICI is, of course, multiplexed according-ly.
The modificationsThe bold lines and the shaded area inFig. 2 give all the necessary details on themodifications and the extension circuit.It is recommended to cut the connectionbetween pins 23 and 22 of the socket thatholds RAM IC2. This modification isperformed at the track side of the board,and effectively insulates pin 23-addressline A8 -of the RAM. Solder a wire tothe insulated area that connects to socketpin 23, and run it to pin 3 of 'Goo ( =output 1QA). Construct the inputmultiplexing circuit in the shaded areaon a small piece of prototyping board.and connect it to the VLF storage unit asindicated by the bold, lines. The elec-tronic switches in the 4066 toggle oneach pulse from output 1QA. This ar-rangement ensures that the correct data,i.e., the measurement values for eachchannel, are stored in the relevant 256byte area in the RAM. Zener diodes DAand Da protect the inputs of the 4066against overvoltages. To prevent distor-tion of the displayed image, the signal
Fig. 1 Output %uveform of thestorage unit using incorrect (a) and correct(b) trigger settings on the oscilloscope.
2 -channel
EE
January 1988
271V/iliaCI 5
7.6Ctra
EE2fititA
iil a C2 a JeaCT:aNU. a 71.CTS-11105.-10 a 0a MCI 16/CIS .7114CTI1/9
Fig. 2 Circuit diagram of the complete 2 -channel unit. The modifications are shol% n in bold lines. the extension in the shaded area.
applied to input B may not go negative.Figures la and lb illustrate the effect ob-tained with the modified and extendedVLF storage unit.Finally, some constructors have reportedthe absence of count pulses on pin 7 of1Cio on selecting display range b(12.5 s). This effect is probably due to
parasitic capacitance blocking thedecimal counter, and may be remediedby fitting a 33 k52 series resistor on theTRIGGER output line to the oscilloscope.This resistor also protects the output ofFF2 against short-circuits on the TRIGGER
output. Th
Reference:
(" VLF add-on unit for oscilloscopes.Elektor ElectrOnics, February 1987 p. 38ff.
SOFTWARE UPDATE FOR pPCONTROLLED FREQUENCY METER
The software for the Elektor micropro-cessor controlled frequency meter (seereference")) can be updated as shownhere to enable selecting triggering on theleading or trailing edge of pulses whenthe meter is set to the event count mode.The addition to the existing program en-sures a stable readout when a sawtooth-like input signal is applied to the meter,because triggering can take place on thefast rising edge.As from now, the EPROM for the pro-ject, ESS536N, contains the update.
Reference:
") Microprocessor controlled frequencymeter. Elektor Electronics, January1985.
$E578 JSR SEE90 20 90 EE SEEB3 LDAIM $40 A9 40$EEB5 AND $84 25 B4
$E593 JSR SEE90 20 90 LE $EEB7 EORIM $40 49 40$£E89 ASLA OA
$E5DC JSR $EEAO 20 A0 EE SEEBA ORA $0700 OD 00 07$EEBD RTS 60
$EE90 JSR SEEBO 20 BO EE$EE93 JSR $E528 20 28 ES$EE96 RTS 60 Checksum:
$EEA0 JSR SEEBO 20 BO EE for EPROM ESS831N:SEEA3 JSR $E547 20 47 ES $E811 15SEEA6 RTS 60
for EPROM ESS536N:SEEBO STA $0700 8D,00 07 $E811 1A
34 EE
January 1988
SYNCHROTRON X-RAYSREVEAL HOW ICE FLOWS
by Dr Robert Whitworth, Department of Physics, Birmingham University
Ice covers a great deal of the Earth's surface. Understanding the way it flows is important for manypractical purposes such as exploiting oil reserves and helping the engineer in an ice -bound environment.An ice physics group at Birmingham University is employing a powerful research tool, the synchrotronsource of X-radiation at the UK Science and Engineering Research Council's Daresbury Laboratory, toreveal detail of the flow mechanism of ice in a way not previously possible. Ice has been found to bean especially suitable material for study by this means and the group's findings promise to yield new
insights into crystalline materials.
Everyday experience tells us that piecesof ice are brittle. Yet glaciers, largemasses of ice, flow down the sides ofmountains. In the polar regions hugesheets of ice flow out towards theoceans. The significance of such flow isbrought home when something unusualhappens as, for example, when the Hub-bard Glacier in Alaska advanced rapidlyduring 1986 and blocked an inlet fromthe sea.Engineers who work in the ice -boundregions of the world erecting buildingsor drilling for oil have a great interest inthe mechanical properties of ice, whileice physicists seek to understand the fun-damental principles of its behaviour.With ice, or any other solid, there is stilla great deal to be done before we cananswer the question "Given thecrystalline structure of a material andthe properties of a single molecule, howfast will the material deform when astress is applied to it?" At that point theproblems of engineering and of physicsinteract and progress in either field canbe of benefit to the other.We can tell from the regular forms ofsnowflakes or the patterns formed byfrost that ice is crystalline. This meansthat the molecules within it are arrangedin a regular pattern. Bulk ice consists ofmany crystals or grains of differentorientation, all joined together to form asolid mass. When such polycrystallineice is deformed, several processes mayoccur. With each grain, layers of mol-ecules may slide over one another; this isknown as slip. In addition, grains maymove relative to their neighbours. Dur-ing deformation the structure suffersdamage, which can be annealed out bythe diffusion of molecules or by thenucleation and growth of new grains.These processes occur in all crystallinematerials, but their relative importancedepends on the material and on the tem-perature. The basic process is slip; butwhen ice is close to its melting point theother processes are important, too.
DislocationsIt is a little over 50 years since it was
The process of slip by which plastic deformation occurs in crystals. The original block at theleft is deformed to the shape on the right by one horizontal layer of atoms slipping overanother by the spacing between two atoms. This does not take place all at once: in the in-termediate state shown here, slip starting at A has reached the broken line BC. This is calleda dislocation line and is a region of distortion in the crystal. The deformation of crystals oc-curs by the movement of such lines.
Dislocationline
- ray beam
Crystal
Central spot(very bright)
Topographs
..--Screen
Formation of images of a crystal by X-ray topography using the beam from the SynchrotronRadiation Source. Because the beam is highly parallel, each point on the crystal diffracts theX-rays to the corresponding point in each of the diffraction spots formed on the film.
realized that one layer of a crystal can-not slip over another as a rigid whole. Ifwe imagine that slip over one atomicspacing starts at a corner, for examplepoint A in the first diagram, and con-tinues up to the line BC, this line marks
a region of distortion in the crystal. It iscalled a dislocation line or, for short,just a dislocation. Arrangements of theatoms near B and C are then as il-lustrated. The plastic deformation of asingle crystal takes place through the
EE
January 1988
Three topographs from a sequence showing the movement and multiplication of dislocations during the plastic deformation of a single crystalof ice at -20 °C. These illustrations are negative prints, so dislocations appear bright against a dark background. The width of the regionshown is 4 mm on the crystal.
movement of these dislocation lines.How much stress is required to movethem and the way in which they movehave been extensively studied in metalsand many other materials: the mostpowerful technique for observing dislo-cation lines is transmission electronmicroscopy. A limitation of this tech-nique, however, is that the samples haveto be very thin foils held in a vacuum,and it has so far proved impossibly diffi-cult to study the properties of dislo-cations in ice in this way.A different technique, which has in thepast been used successfully to observethe dislocations in ice, is known as X-raytopography. Great improvements to thistechnique have recently been achievedthrough the use of X-rays from a syn-chrotron radiation source. By using thesource at the UK Science and Engineer-ing Research Counsil's Daresbury Lab-oratory we have been able to investigatethe motion of dislocations in crystals ofice several millimetres in size in a degreeof detail that has not previously beenpossible.The Synchrotron Radiation Source is alarge installation in which a beam ofelectrons with an energy of 2 GeV (giga-electronvolts) is bent by magnets to cir-culate in an orbit of diameter 30 m. Asit does so it emits intense electromag-netic radiation in the plane of the orbit,with a spectral range from infra -red toX-rays. When the X-ray beam falls on asuitably oriented single crystal, as shownin the second diagram, the crystal dif-fracts the X-rays to produce a number ofbeams in accordance with Bragg's law ofdiffraction. When the beams fall on ascreen behind the crystal they formspots. In topography experiments atDaresbury the X-ray beam travels 80 mbefore it reaches the crystal, so it is virtu-ally parallel. Because of this, every pointon each diffracted spot corresponds to aparticular position in the crystal. How-ever, the diffraction from any pointwhere the crystal is distorted will beslightly altered in such a way as to pro-duce contrast at the corresponding pointin the diffraction spot. In our ex-
periments the diffraction spots arerecorded on photographic film, therebyproviding images of the crystal known astopographs. Dislocations are clearly vis-ible within them, usually as dark lines. Asequence of such topographs taken whilethe crystal is under stress reveals the mo-tion of dislocations as the crystaldeforms. Compared with a normal X-ray source the synchrotron radiationbeam is very intense and exposure timesare comparatively short (typically 15 s).This makes proper dynamic experimentsa realistic proposition for the first time.
MultiplicationCrystals used in these experiments mustbe of very high quality because the in-itial density of dislocations has to be lowenough for them not to obscure oneanother in the topographs. Large, singlecrystals are specially grown in Birm-ingham for the experiments. In thecourse of deformation, the density of
dislocations increases, as seen in theseries of topographs making up the thirdillustration. This increase is essential tothe process of deformation. The dislo-cation line is the boundary on the slipplane between the region which hasslipped and the region which has not;the rate at which the boundary movescorresponds to the rate of deformation,but if all the dislocations that were pres-ent to begin with merely moved acrosstheir slip planes and out of the surfacethe deformation would stop. New dislo-cation lines are created by a process ofmultiplication, the mechanism of whichwas first suggested in 1950 by F.C. Frankof Bristol University and W.T. Read ofBell Telephone 'Laboratories. If a dislo-cation line does not lie entirely on oneslip plane, but makes a step from oneplane to another, the dislocation lines onthe separate planes form a spiral aroundthe step as shown in the fourth illus-tration. This means that the dislocationsdo not pass out of the crystal but con-
Dislocation multiplication by the so-called Frank -Read mechanism. The dislocation line is in-itially at ABCD, with the sections AB and CD lying on different slip planes. Under stress thestep BC does not move, but as AB and CD move forward to All and CD' and then to A"Band CD" they generate spirals around B and C. Seen in projection on the slip plane it appearsas if loops are being generated from the point corresponding to BC. These are the 'loops' seenin the lower right of the sequence of topographs.
36 EE
January 1988tinuously grow longer. Near the centre ofthe spiral, slip amounts to as manyatomic spacings as there are turns in thespiral.In the sequence of topographs, a pair ofopposite spirals can be seen developingin the lower right-hand corner. The pos-ition of the step from which theyoriginate is marked by the arrow in thefirst topograph. Often, the multipli-cation is more complicated as is shownin the topograph on the front page.When we recall that the dislocation lineis the boundary of the region which hasslipped, it is remarkable how convolutedthe boundary can become. Thesetopographs of ice are some of theclearest images of dislocations moving incrystals of this size ever obtained in anymaterial; the study promises to yield anunderstanding of the processes ofdislocation multiplication in bulksamples which will be significant in theunderstanding of other materials, too.The crystal structure of ice has a hex-agonal axis of symmetry which is easilyseen in the shapes of snow flakes, anddeformation of single crystals is know tooccur almost entirely by the slip ofplanes, called the basal planes, lying
Basal slipplanes
Prismaticslip planes
Shuffleplane
- Glide plane
Diagram of the crystal structure of ice. The circles represent water molecules, each of whichis linked to four others by hydrogen bonds. The hexagonal axis of symmetry is vertical andthe normal slip planes (the basal planes) are horizontal. There are two sets of such planes,the glide set and the shuffle set, between which slip may occur. Possible prismatic slip planesare shown as vertical. As in the case of basal slip, the slip direction on these prismatic planesis horizontal, approximately into or out of the plane of the diagram.
This image shows part of a single crystal of ice after a small amount of plastic deformation. It is an X-ray topograph, formed diffractionof X-rays from the Synchrotron Radiation Source al the UK Science and Engineering Research Council's Daresbury Laboratory. Deformationtakes place through the movement of defects in the crystal known as dislocations, seen here as bright lines. Dense bands of them are spreadingfrom the left-hand side and are just beginning to do so from the right, generated by a process of dislocation multiplication which can be seenhappening more clearly in the formation of the tangled loops at the lower right. The spiral to upper right of centre was formed by diffusionof defects prior to deformation. Taken by scientists from Birmingham University, the topograph is of an area of crystals one centimetre across.
perpendicular to this axis. The finaldiagram of the structure shows that thereare two kinds of basal planes betweenwhich slip might occur, in two sets calledthe glide set and the shuffle set. It hasnot yet been possible to find out by ex-periment which set slips. By comparisonwith other materials of similar structure,and for theoretical reasons, the glide setseems the more likely. From the diagramit is far from obvious why ice should notdeform just as easily by slip on verticalplanes known as prismatic planes. Butexperiment shows that it takes about 50times more stress to deform ice in thatway.To deform a polycrystalline mass of ice,slip within the grains must take place inmore than one set of parallel planes ifthe grains are not to come apart at theboundaries. This is the main reason whypolycrystalline ice is stronger than asingle crystal. From our topographs wehave found that, in certain circum-
stances, dislocations on prismatic planesmove as fast as or faster than those onbasal planes. This comes as a surprise toanyone who knows how difficult it is todeform ice along the prismatic planes,and it looks as though the preference forbasal slip arises not because it is difficultto move dislocations along other planesbut because multiplication is easier inthe basal plane.Another effect that is important poten-tially is that the strength of ice is verysensitive to the presence of minute tracesof certain impurities. Some years ago,Dr S.G. Jones ans Dr J.W. Glen in ourlaboratory found that one part in amillion of hydrogen fluoride reduces thestress needed to deform a single crystalof ice to as little as one -quarter of nor-mal. It may be significant that small ad-ditions of hydrogen fluoride also pro-duce large changes in the electricalproperties. We hope to use X-ray top-ography to investigate these effects, and
EE
January 1988so learn more about the processes whichlimit the rate of movement of thedislocations.A proper understanding of the physicsgoverning dislocation movement in amaterial is necessary for a theoretical in-terpretation of the strength of thatmaterial. Metallurgists have made greatuse of knowledge gained from electronmicroscopy in developing new alloys foruse in aircraft, nuclear reactors andelsewhere under other extreme con-ditions. A similar understanding of thephysics of ice is needed to predict ormodify the behaviour of ice in the en-vironment. It is even more necessarywhen we wish to forecast how ice willbehave in less familiar conditions. Forexample the recent discovery that someof the moons of the planets Jupiter andSaturn are composed mainly of ice hasled to questions about how ice woulddeform on a geological time scale at highpressures and at low temperatures.
EVENTS EVENTS EVENTS EVENTS IEE meetings this month6 Computer -based diagnosis7-8 Mathematical modelling of semi-
conductor devices and processes11 The impact of ASICs on equipment
design12 Military aircraft satellite communi-
cations14 Industrial LANs-the real issues14 Gallium -arsenide: a new generation
of devices and integrated circuits19 Speech processing20 Satellite instrumentation21 Electronically scanned antennas26 Advances in technology for solid-
state broadcast transmitters26 Engineers in management27 Towards optical integrated circuits28 The role of highly elliptical orbits in
satellite communications29 Managing ASIC design projectsFull details from The Institution ofElectrical Engineers Savoy Place LONDON WC2R OBL Telephone01-240 1871
Information ShowcaseInformation Showcase, a new eventwhich will seek to bring together thevarious aspects of information-fromcreation, organization and handling totransmission, use, display andexploitation-is planned for the Bar-bican Centre, London, from 15 to 17March 1988. It is being organized byFocus Events in association with the In-titute of Information Scientists. Theevent is aimed at computer managers,government officials, professionalgroups, such as financial managers,market researchers, solicitors, stock-brokers, publishers and advertising
agencies, as well as all those involved inthe information industry.Details from Focus Events LtdGreencoat House Francis Street LONDON SW1P 1DG.
Frost & Sullivan events thismonth (all in London)11-12 Voice Network Design & Optimiz-
ation13-15 Evaluating and Implementing
Local Area Networks18-19 An Introduction to Data Com-
munications and Networking forthe IBM PC
20-22 The OSI Reference Model andNetwork Architectures
25-27 X.25 and Packet Switching Net-works
Frost & Sullivan Ltd Sullivan House 4 Grosvenor Gardens LONDON
SW1W ODH Telephone 01-730 3438.
British Computer SocietymeetingsA Data Protection Seminar will be heldat the Green Park Hotel, London, on 19January; at The Grand Hotel, Birm-ingham, on 16-18 February, and in theGeorge Hotel, Edinburgh, on 3 March.Plenary and Working Group Meetingsof the International Standards Organiz-ation will be held from 25 January to 4February at the St. Pierre Park Hotel inGuernsey.Details of these events from The BritishComputer Society 13 MansfieldStreet LONDON W1M OBP Tele-phone 01-637 0471.
ICS courses this monthExpert systems: design & development
26-29 London and Paris (in French)Real-time operating systems19-22 LondonHands-on programming in C26-29 Paris (in French) and Stockholm
(in Swedish)Details from ICS Publishing Company(UK) Ltd Telephone 0800 282 353(UK only) or +44 372 379211 (outsideUK); France: Integrated ComputerSystems Telephone (1) 48 39 88 00;Sweden: ICSP Utbildning AB Tele-phone (08) 18 99 00.
Electrex '88Electrex '88, the XXIV InternationalElectrotechnical Exhibition, will be heldat the National Exhibition Centre, Birm-ingham, from 29 February to 4 Marchnext. BEAMA's annual dinner will beheld during the exhibition on 2 Marchwhen the principal speaker will be theRt. Hon. Cecil Parkinson, MP, Secretaryof State for Energy.Details from Cavanagh Associates 10Vaughan Road HARPENDEN ALS4ED Telephone (05827) 68219.
International BroadcastingConventionThe Call for papers and exhibition infor-mation for IBC 88 has been issued:copies can be obtained from the IBCSecretariat The Institution of Elec-trical Engineers Savoy Place LON-DON WC2R OBL Telephone 01-2401871.The convention will be held at theMetropole Conference and ExhibitionCentre, Grand Hotel, and the BrightonCentre, BRIGHTON from 23 to 27September next.
EE:38
janua V 1981VIMICS REVOLUTIONIZEWIDEBAND RF AMPLIFIER
DESIGNA small 4 -pin device that, together with a few external passive components, can be used for building an
unconditionally stable RF amplifier which guarantees a moderate noise figure and high amplificationfrom DC (yes!) to well over 1,000 MHz, without the need of extensive bias circuits, decoupling, and
cable matching at input or output.The latest dream of an RF designer? No, an MMIC from Avantek of Santa Clara.
Recently, Avantek added 4 devices totheir existing series of monolithicmicrowave integrated circuits (MMICs).Up to then, MMICs had found appli-cations mainly in the RF sections of pro-fessional telecommunication equipment.The new devices are the MSA01xxthrough MSA04xx, plastic encapsu-lated-and, therefore, less expensive-versions of the existing ceramic (Micro -X) chips.The aim of this introductory article is toshow that these new devices enable anydesigner with a reasonable knowledge ofapplied electronics to build a wideband,high performance RF amplifier withhardly more effort than necessary forgetting, say, an LM386 based AF ampli-fier to work.
What is an 111MIC?
Avantek's MODAMP1) series ofMMICs is essentially a family of siliconbipolar wideband amplifiers that areavailable in a variety of ceramic and-recently-plastic packages. MivIICs arefabricated using nitride self alignment,ion implantation for precise control ofdoping, and nitride passivization forhigh reliability. They house an accuratelyengineered darlington transistor con-figuration with extremely low stray in-ductance and capacitance. Internal seriesand shunt feedback ensures high re-peatability from amplifier to amplifier.The complete family of Avantek MMICsis listed in numerical order in Table 1. Itis seen that the devices can be selectedfor highest amplification, lowest noisefigure, and optimum 3rd order intercep-tion point, as required for the appli-cation in question.The performance of the MMIC can bededuced from the 4 or 6 digits followingthe letters MSA in the type number (re-fer to Table 1):
Digits 1 and 2. Electrical perform-ance:
01: Low output power (Pidg = 1
ASO - stfo 14H -a.RI(
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1.5 dBm), high gain (18.5 dB), andmoderate noise figure (WF=5 dB).
02: Medium output power(PUB= 4 dBm), medium gain(c. 11 dB), and moderate noise figure(NF= 6 dB).
03: High output power (Pi dB =10 dBm),medium gain (c. 11 dB), andmoderate noise figure (NF = 6 dB).
07: 02 series with lower supply voltageand lower NF.
08: special device optimized for highestgain (30 dB) and lowest noise figure.Medium output power(Pup =12 dBm). Requires a non-standard bias decoupling network toensure stability.
Digits 3 and 4. Package style:
04: low cost, 145 mil, round, plasticpackage.
20: 200 mil, square, ceramic (BeO)package for optimum therMal con-ductivity.
35: 100 mil. square, Micro -X glass sealed
trAtt
secin.kur.
raap,-A,-"
wourery Prtx--46Si MIMS
Csscadabte 41.616,..1,d A..re 194,1
package for minimum parasitic in-ductance and capacitance.
70: 70 mil, square, gold plated package.for high -reliability applications.
85: low cost, 85 mil, round, plasticpackage similar to Micro -X.
86: surface mount package; decreasedRF performance with respect to style85.
I Digit 5. Supply voltage:
1: MMIC has an on -chip series bias re-sistor, and can be fed from +12 Vvia a small choke. Device has 1
ground terminal.2: MMIC requires an external series
bias resistor plus choke to ensure anoperating voltage of 5 to 6 V. Devicehas 2 ground terminals.
Digit 6. Performance indication:
1: Premium device with extended fre-quency range.
2: Standard device.
120
18
16
14
TT,. 12
Z 10
0 86
2
+20
+15
+10
+5
0
TYPICAL GAIN vs. FREOUENCY
MA 01 I 1111=11111111111-imummullII MIER111111_ -03)0( 1111111111
SASA 0270071 NIMBINEMPfflil_ I_ AIM
BUM111111111111111111MINIZEll
11111111M111111111111111
MSA 04XX
-5 2FRED GH2
OUTPUT POWER AT 103 GAIN COMPRESSIONvs_ JUNCTION TEMPERATURE
Fo = 500 MHz, Ica TYPICAL VALUE
10
MSA O4XX
037JC
MSA 02XXMSA 01XX
-75 -2s +25 +75 +125
Fig. I. These curves enable quick selection ofan MMIC for a given application.
Fig. 2. Basic connection diagrams forMMICs with (a) and without (b) an on -chipbias resistor. The version is indicated by digit5 in the part number.
11111111111111111111 \ 111111111\11 \ 1
Fig. 3. The new plastic encapsulated MMICsType MSAXX04 are considerably larger thanMicro -X types in a ceramic enclosure.
The photograph of Fig. 3 shows the dif-ference in size between the plastic encap-sulated MMICs Types MSA0204 andMSA0304, and 2 MSA0435s housed theMicro -X package. Note the type indi-cation on the plastic MMICS; theMicro -X types are so small that a col-oured band around the ceramic body isused for type reference. Fortunately,Avantek supplies all MMICs in separateplastic enclosures with the type indi-cation printed clearly on the back.The performance of the MMICs in theMSA series, excluding the special 07xxand 08xx types, is shown in Figs. la andb. The curves enable ready selection of asuitable device for a given application.The gain of all devices exhibits aremarkable flatness from 100 MHz upto I GHz. Types MSA03XX andMSA04XX reach up to 2 GHz with again ripple of ±1 dB. In a standardamplifier based on discrete components,this son of performance is almost im-possible to achieve without resorting toeleborate feedback networks and expens-ive, gain controlled, active devices.MMICs are well suited to cascading in2- or 3 -stage wideband amplifiers with again of up to 25 dB. In general, the RFinput stage will be dimensioned forlowest noise figure, while the secondstage is set up with an \IMIC that en-sures high gain.Figure 2 shows the remarkably simplebasic configurations of amplifiers basedon MMICs. The difference between thecircuits is mainly the connection of thechip to the supply voltage, as dis-cussed above (Digit 5). The value of thebias resistor in the circuit of Fie. 2b iscalculated from
R = (Vcc- Vmmic)/Immic
where VNIMIC and Immic are the optimumvalues taken from the relevant datasheet. The resistor is preferably a carbontype to ensure an total reactance of theR -L combination greater than 500 Q atthe frequency of operation. Without thechoke, the MMIC would see the supplyresistor connected in parallel with theload impedance, because the decoupledpositive supply rails is simply ground forRF signals. It is recommended to ensurea mimimum drop of 2 V across the re-sistor.The only other components required tomake a functional wideband amplifierare 2 suitable RF sockets (BNC, SMA,TNC) and 2 blocking capacitors. One ofthe most striking characteristics of theMMIC based amplifier is the absence ofany form of impedance matching cir-cuitry at the input and output. This ob-viates the need of difficult -to -make in-ductors, and decoupling of the biaspotential applied to the amplifier input.The input and output impedance of anyMMIC in the MSA series is 50 Q, andthe VSWR (reflection coefficient; the
EEJanuary 1988
voltage standing wave ratio, Zo/R) isnever worse than 2:1 when the device isfed with the recommended supplyvoltage.The blocking capacitors should present areactance of the order of a few ohms,and have good RF properties. Silvermica types can be used with satisfactoryresults for HF and VHF, but leadless cer-amic chip, or SMA, types are a mustwhen frequencies higher than 1 GHz areinvolved. Due care should be taken toallow for the stray capacitance at theMMIC input and output.It is, of course, possible to dimension theblocking capacitors such that a low fre-quency roll -off is created, purposelylimiting the bandwidth of the amplifierat the lower end of the spectrum. WithZi=Z,=R =50 Q, and C fitted at theinput and output of the amplifier, the6 dB cut off frequency, fc, is calculatedfrom
fc= 1/(2700C)
39
Although MMICs work fine below, say,30 MHz, some discrete or integratedVHF/UHF power amplifiers may re-quire bandwidth limiting capacitors toavoid spurious oscillation due to thehigh gain -bandwidth product.
Drop -in amplifiers
MMICs are often referred to as drop -inamplifiers by virtue of their directmatching to 50 Q sources and loads,their unconditional stability and im-munity to source or load impedancevariations (filter drivers!), and theabsence of alignment points. Single orcascaded MMICs enable quick and costeffective building of accurately tailoredRF and IF sections in VHF, UHF andSHF receivers. In transmitters andtransverters, the more powerful MMICsof Table 1 can be used in driver stagesand oscillator buffers. A wideband ac-tive probe for use with an 1 GHz oscillo-scope or a frequency meter is yet anotherof the many applications that come tomind considering the low cost and easeof use. The simple supply voltage ar-rangement for MMICs makes it possibleto power the amplifier via the coax cablethat carries the output signal to the in-strument.
More power: more MMICs
Identical MMICs with a high outputpower compression figure may be con-nected in parallel to increase theavailable power output. All MMIC out-puts are simply connected and fed froma common RF choke and biasing re-sistor. This set up requires only I outputblocking capacitor between the supply
40 EE
January 1988
Fig. 4. Connecting MMICs in parallel ar-rangements to achieve higher output power.
junction and the RF output. EachMMIC input, however, needs its ownblocking capacitor to the amplifier in-put. With n MMICs in parallel, the in-put and output impedance is simply50,n Q. Figure 4a shows the use of 4MMICs in parallel, with 4:1 step upbaluns (balance -to -unbalance trans-formers) to maintain 50 Q input andoutput impedance. It should be notedthat the parasitic capacitance of thebaluns may have a limiting effect on theoverall bandwidth of the amplifier.Another example of a multi-NINIICamplifier is shown in Fig. 4b. This is theso-called unilateralized push-pull ampli-fier. Unilateralization is a technique inwhich the imaginary as well as the realterm of the feedback elements is can-celled. This creates an amplifier withhigh isolation between the input and theoutput. The technique differs fromneutralization as a means of stabilizingan amplifier. In neutralization, only theimaginary terms of the feedback reac-tances are cancelled because thenecessary inverse feedback is providedthrough a small inductor or capacitor,which does not track the reactance of theinductive or capacitive feedback overfrequency. Consequently, the conven-tional neutralized amplifier is only stableover a relatively small frequency range.In the circuit of Fig. 4b, each MMICforms the active, negating element in thereactance of the other's feedback circuit.The inductors in the circuit serve thedual purpose of 4:1 impedance transfor-mation and balun. The reason thatMMICs are so easily unilateralized isthat their internal feedback network isof very low Q compared to that of con-ventional amplifiers, ensuring apredominantly resistive rather than reac-tive feedback. It should be noted, how-ever, that unilateralization in push-pull
5
AVANTEK 04 PLASTIC PACKAGE
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5 50 05 a8 7055 ; 50 10 -5 5 50 - GPO - 255 50 1 0 r cam - 12
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EE
January 1988
circuits is only useful for providingslightly higher gain or substantially moreisolation between the amplifier inputand output.
The main technical specifications of theType MSA0404 are given in Fig. 5. It isseen that this device provides a virtuallyflat power gain of about 8 dB from50 MHz right up to 2 GHz. The noisefigure of the MSA0404 makes the deviceless suitable as an RF preamplifier, but itis ideal for building a wideband signaldistribution amplifier for use in, say,CATV or satellite TV systems.
Construction: generalconsiderations
The scope of this introductory articleallows only general considerations onthe construction of MMIC basedamplifiers. The subject will, therefore,be reverted to in greater detail in a forth-coming issue of Elektor Electronics.An experimental HF or VHF amplifierbased on MMICs is readily built on apiece of double -sided, unetched glass -epoxy circuit board material. All ter-minals that require grounding aresoldered direct onto the copper surface,and the blocking capacitors are fittedwith flying leads between the MMIC andthe respective RF socket. The circuitboard can be secured in a small alu-minium enclosure. A hole is drilled inthe circuit board to enable the groundleads of the MMIC to be soldered to thecopper surface with the shortest possiblelength. MMICs have substantial gain atlow frequencies, requiring due attentionto be paid to the dimensioning of thesupply decoupling. A 4.7 pF tantalumbead capacitor and a 1 nF disc ceramictype in parallel should work satisfac-torily in most cases. The use of metalfilm resistors for powering the MMIC isnot recommended. Some inductanceshould be provided, so that a common
\V or VAV carbon resistor gives farbetter results.Microstripline techniques are a must formaintaining the correct input and out-put impedance of 50 Q when MMICsare used at frequencies higher than1 GHz. Figure 6 shows the rec-ommended lay -out of an amplifier basedon a single MMIC with external bias re-sistor (types -21 and -22). The PC boardmaterial is preferably RTE Duroidwhich ensures a uniform dielectric con-stant, and low loss at frequencies up to4 GHz. The bypass and blockingcapacitors are leadless ceramic or SMAtypes, and the rectangular copper areasat the input and output of the MMICform the 50 Q matching microstriplines.The centre pins of the RF connectors aresoldered straight onto the input and out-put areas.The layouts of the printed circuit boards
Fig. 6. Component arrangement for anMMIC based RF amplifier in microstriplinetechnique.
in Fig. 7 can be used for building 1, 2, or3 -stage microstripline MMIC amplifiers
, based on Micro -X devices with externalbias networks.
Conclusions
The introduction of the plastic MSA0104through MSA0404 MMICs is sure toboost the interest in these extremelysimple -to -use RF amplifiers, since theseare now available at affordable cost, andin an easy to handle package. MMICsare, however, not always the best choicefor designing an RF input stage. Theirnoise figure of 3 to 6 dB is still relativelyhigh compared to GaAs FETs (0.5 -2 dB) at frequencies higher than about
Fig. 7. Suggested PC board layouts formicrostripline amplifiers using theMSA0X35 series of cascadable MMICs inMicro -X style.
Tab'e 1
MSA SERIES 17-01,1cal Spe,-.5hcations a 25°C Case TeMperalule)118.4... Sr,. ft.i
c1/4.1 -
thew.Here.. l',
Gaine Li Mu 1, a
Fiski.eC. 0.5 GK.
P,.5 03 000
s.,5 0.5 Gift Case
14amber 40410 gel Kiiiii tai ta-,,,, tAs.1 Toe
LISA -0104 2.5 183 03 5.5 15 150 4 -Pat- 5300401.1511.0204 25 125 08 60 40 170 4 -1140 c4. -W-4-
119543304 2 5 11.5 0 9 6 0 10 0 23 0 4 -Lac 1:41-1-,C
MSA-0404 3_0 82 1.5 6 5 17 0 260 4.-.Pac, 04a5z...-
1151A44207 3 0
2.08_5 2 5 6.
5439 0
1034-0145
203 rrii Beta119A-0135-11
rn.cro-X18.5 --051455-0135-12 15 16.5 03 5.0 1.0 14$ Plvii-XUSA -0135.21 30 19.0 07 50 15 150 micto-X113.A.0136-22 25 19.0 04 50 1.5 150 mczy-X1151-0235-11 2.0 115 11 60 30 160 r...7,c-X1151-0235.12 1.5 11.5 09 60 3.0 160 riiizro-X0353-0735-21 3.0 125 1/ 60 40 710 rracro-X1055-023512 25 115 1 4 6 0 4.0 17.0 tr-o-3.USA -0335-11 2-0 115 1.1 60 90 22.0 'micro -1
1495-0335-12 15 11.5 0 9 6.0 90 220 mcro-X315A-0335-21 3_0 125 17 60 100 230 0005-X115A-033522 2.5 12.5 IA 60 100 230 mpe00.21151-04351 30 65 22.5 60 130 28.0 11iao-IC115A -0735i 40 135 17 15 5.0 200 mom-%115A-01351 50 330 - 30 125 250 41-1:4LX
--- 115.1-0170-11 2.0 185 0.6 2-0 1.0 145 70 rr:11455-0170-12 15 185 04 50 1_0 145 701.11149A-0170-21 3.0 190 0.7 5.0 15 15.0 70 m-...1
6/31-0 I 70-22 25 150 05 50 1.5 15.0 70 rril1153-027311 2_0 11.5 1.5 60 30 160 70 Psi5131-0270-12 19 11.5 1.1 60 30 16.0 70 nti1455-027041 30 125 1.9 60 40 173 701x95151-0270-22 2.5 125 15 60 4.0 17.0 70.,1USA -037041 2.0 115 1.4 6.0 90 220 70 mi1x51,0370-12 15 11.5 1 1 60 93 220 70 001435-037041 3.0 125 1.9 6.0 10_0 230 70121453-0370-22 25 125 I 5 6 0 100 230 70 0JM5511470, 30 85 22 ,..- T 130 280 70 ,004, 5 A-07704 4.0 735 17 50 200 70,001055.0370= 6 0 33 0 - 12 5 22-0 70 ms
155.4031557 25 15 5 0 5 = = 1 5 150 35 0017570.71155-02851 2.5 130 I z 4.0 180 65 ml va47.4USA -03357 25 110 ' 10.0 : 23.0 85 and gilasic1435-04651 3_0 8 5 130 22.0 115 rr 534.e.-1.155-0735= 4 0 135 2-0 17.0 85 00 534111.--1451.01551 60 330 - 70 115 27.0 85 .7.3 r-,.....-5151,31161 yEastc surface massMSA-02161 111517 Solace mairs!1455-03551 025L,C 14,17".311,14.4-11055-04357 pkar.:c 3,015:4 e3c5474/1SA-0735= FA4ste 3.10ce rnoura5151,0156.1 034E4 urtece r5a.84
NOTES:1 1573e1 IX 13.041 Gro74,73-repi--eE 5.7 a ilarr tral 04434.0 14 .*137.4 at 0* 904901 R141415 51414,110 844w,11
-174 51sgie viir,-...1--ez... .. 12 .:, 51 511435 4. Refer 10 5,./*, -31:c (Paw:4n2 Dkiai 6451x41 Orgy.3 tie. 94.040 S,..4.4 7.....7I p...401, .1.x ke hult-v 800Li3 of irdoemaicei.C.0,-5,.01 y7"...4t7 2354.1 kran%4 Neve:v1.1e
42 EE
January 19881 GHz. A GaAs FET is fairly difficult toconfigure as a wideband amplifier, how-ever, and that is the application par eX-ellence Of the new monolithic microwaveintegrated circuits. Bu
References:Avantek product application infor-mation:Recommended Mounting procedures SiMMIC cascadable amplifiers.
Paralleling & unilateralization ofMODAMP'', silicon MMIC amplifiers.Filter design using MDDAMP! siliconALIIIC amplifiers.
Monolithic Microwave Integrated Cir-cuits. By Al Ward, WB5LUA. QST,February & March 1987.
Table 1, Figs. 1, 2, 4, 5, 6 and the photo-graph opposite were reproduced for thisarticle by courtesy of Avantek Inc.Fig. 7 was reproduced by courtesy ofFocus GMBH, Kaisheim.
Avantek worldwide
[lead office:3175 Bowers AvenueSanta Clara, CA 95054-3292U.S.A.Tel. (408) 727-0700.Semiconductor Customer Service:Tel. (408) 970-2659.TWX: 310-371-8717
AUSTRALIAG. Bendixen and Associates Pty. Ltd.Suite 9, Level 510 Help StreetChatwood, SydneyNSW 2067, AustraliaPhone: (02) 411-8005
Graphic Electronic Industries Pty. Ltd.168 Payneham RoadEvandale, So. Australia 5069Phone: (06) 363-0277
BELGIUMSimac Electronics S.P.RPLRue du Progres, 52 Boite 21000 Brussels. BelgiumPhone: (32)-2-2192453
INDIAHinditron Services Pvt. Ltd.69-A.L. Jagmohandas MargBombay 400 006, IndiaPhone: 8221529 or 8229677
INDONESIAP.T. Subur Sakti PuteraJ1 Cideng Timur 68A, P.O. Box 4467 Jkt.Jakarta Pusat, IndonesiaPhone: (62) 359163 or (62) 359764
ISRAELma -.1. Engineering Ltd.182 Ben Yehuda StreetP.O. Box 16349Tel -Aviv 61162, IsraelPhone: (972)-3-249-273
CANADASheppard Agencies Ltd.P.O. Box 8Georgetown, Ontario 170 4T1, Canada(416) 877-9846
FRANCESerrgop4, rue Paul Bert92150 Suresnes, FrancePhone: (33) 45 06 3303
HONG KONGEnrich Transworld Ltd.240M, 7 Seas Shopping Centre121 Kings RoadHong KongPhone: 852-5-663-062 or852-5-663-087
ITALY
Sistrel Elettronica Micro-Onde S.P.A.Via Luigi Chiarelli N. 1900137 Rome, ItalyPhone: (39)-6-827-8551 through 8554
JAPANSogo Electronics, Inc.3-13-15 Minami KarasuyamaSetaeava-KUTokyo, 157 Japan
Simac Electronics B.V.Veenstraat 205503 HR WldhovenThe NetherlandsPhone: (31)-40-582911
PHILIPPINES"Y Engineering Corporation2212 Marconi StreetP.O. Box 3355Makati, Metro ManilaPhilippine IslandsPhone: (63)-89-51-28
SWEDEN, NORWAYFINLAND, DENMARKVisitron AllP.O. Box 6063Krosseatan 40S-16206 Vaellineby, SwedenPhone: (46)-8-38-01-30
SWITZERLANDWalter Electronics AGBruehlwiesenstrasse 17CH -9545 WaengiSwitzerlandPhone: (41)-5.1-512-277
TAIWANEvergo Corporation4th Floor, 75, Section 3P.O. Box 96-546Nan King East RoadTaipei 104, TaiwanPhone: (886)2-536-7451
THAILANDG Simon Radio Co.. Ltd.30 Patpong AvenueBangkok, ThailandPhone: (6)-2-340-9913
UNITED KINGDOMWave DevicesLaser House132/140 Goswell RoadLondon EC1V 7LEEnglandPhone (44)-1-251-5181
Focus Electronic GmbHNimrodstr, 1 Bergstetten8851 Kaisheim, West GermanyPhone: (49)-9-09009/591
YUGOSLAVIA
REPUBLIC OF SOUTH AFRICA WEST GERMANY -AUSTRIASouth Continental Devices (Pty.) Ltd.P.O. Box 56420 Pinegowrie, 2123Republic of South Africa
5th Floor Randover HouseDover StreetRandburg, Republic of South Africa Belram S.A.Phone: (27)-11-789-2400 83 Avenue des Mimosas
1150 Brussels, BelgiumPhone: (32)-2-343-332
EE
January 198843.
APPLICATION NOTESThe contents of this column are based on information obtained frommanufacturers in the electronics industry, or their representatives,
and do not imply practical experience by Elektor Electronicsor its consultants.
AUTOMATIC MAINS VOLTAGESELECTOR
by K Wetzel
A newly developed opto-triac (SITAC) obviates the need for manual line voltage selection any timemains powered equipment is transferred between 110/117 and 220/240 VAC networks.
The application circuit discussed here isa high voltage DC power supply as usedin TV sets. With reference to the circuitdiagram of Fig. 1, the SITAC TypeBRT12 is turned off when the HV supplyis powered from a line voltage between180 and 270 VAC. This means that the 4diodes in GI form a full -wave rectifierthat provides about 300 VDC across theseries connected smoothing capacitors atthe output of the circuit.When the circuit is connected to a110 VAC mains network, however, theSITAC is conductive, causing a low re-sistance connection between the rectifierand the junction of the smoothingcapacitors. The bridge rectifier thenfunctions as a voltage doubler, so thatthe output voltage of the circuit is stillabout 300 VDC.The SITAC is driven by a simple controlcircuit set up around the SIPMOS powerFET Type BUZ74. The 22 V zenerdiodeprovides the reference voltage, while the1N4001 plus the 22 pF capacitor form asingle-phase rectifier. When a low AC in-put voltage (110 V) is applied, the smallsignal npn transistor Type BC237 isswitched off by the 220K -18K potentialdivider at the base. The SIPMOS FET isconductive, because the gate is held atthe zener voltage of 15 V. The source re-sistor of 5K6 limits the current to about2 mA, however, even when the AC inputvoltage is relatively high (>240 VAC).The SITAC is triggered by the drain cur-rent of the power FET. When more than165 VAC is applied to the circuit, theBC237 is switched on, and effectivelyshort-circuits the gate voltage for the
BUZ74, which in turn interrupts thetrigger current for the SITAC. The pro-posed control circuit accepts line volt-ages between 50 and 300 VAC. Thetoggle point for the conductive or non-conductive SITAC is reached at an inputof about 165 VAC, and is determined bythe potential divider at the base of theBC237.The output power of the circuit isgoverned by the SITAC type, the bridgerectifier and the smoothing capacitors.The application circuit as shown cansupply a maximum continuous outputcurrent of 200 mA at Ta =45 °C.
Source:
Siemens Components no. 25 (1987),issue 1,Siemens distributors in the UK are listedon InfoCard 509-sec EE May 1987.
Mr K Wetzel is with Siemens A.G., Com-ponents Division.
Mr K Wetzel is with Siemens A.G., Com-ponents Division.
1
85 to 270V
V 1N4007 SITAC
_ORTIZ
022MS/0220W L-Y-21__LI&j
1-3114- 81E74
E 15V11.- 220F
18 kg
o0%,
BC 237
05.6 kfl
4x1N4007
E 22 V
+ 310 V
47 uF
47 uF
Fig. I. Automatic line voltage selection using SITAC Type BRTI2 from Siemens.
Mr,
SIR CLIVE SINCLAIR: SUPERELECTRONICS ENTREPRENEUR
As both a leading developer of originalideas in the electronics industry and abusinessman who pioneered mass mar-keting of his products well below theprices of his rivals, Sir Clive Sinclair hasfirmly established himself as the bestknown Britain in his field today.A public opinion poll a few years ago inthe United Kingdom placed him in a listof the top ten scientists of all timealongside Leonardo da Vinci and AlbertEinstein, although he has no pro-fessional academic background and didnot even go to university. After over 25years in business, he is still producingideas for new electronic products andlaunching the firms to manufacturethem.To achieve this, he often drives researchteams to turn his ideas into productsahead of the competition worldwide.But his commercial origins lie in techni-cal fields far removed from the waferscale chips and portable telephones thatnow dominate his business plans.
Early commercial pursuitsIt is noteworthy that his early days offerlittle clue that he would become the oneindividual associated in many people'sminds with the spread of high tech-nology products into everyday life. Heleft school at 17, with a less than glitter-ing academic record, and before startinghis career as an independent business-man, he was employed on a magazinefor amateur electronics enthusiasts,Wireless World .
The publication is famous throughoutelectronics and communications, and forpublishing Arthur C. Clarke's 1945futuristic article on geostationary com-munications satellites-creations thatnow dominate international telecom-munications.His first company, Sinclair Radionics,opened its doors in 1962 and in manyways marked the start of his career as anelectronics entrepreneur. Its business wasto supply kits to radio amateurs whowanted to make their own equipment,but had previously had to go to a varietyof sources for the necessary parts.The idea was ingenious and workedcomparatively well, but lacked the otherkey ingredient of Sinclair's businessprojects in recent decades-the possi-bility of a mass market for the product.
by Martin Ince
Fig. 1. Sir Clive Sinclair, electronics genius.
There simply are not millions of peoplewanting to build their own radios.However, there was a potential massmarket for his next generation ofproducts-a range of cheap calculatorsand digital watches designed (in anotherSinclair hallmark) to make sophisticatedequipment available at well below theprices of rival suppliers.
Low cost computersWhile some satisfied users of Sinclaircalculators are still to be found in theUnited Kingdom, the increasing com-petition from Far Eastern and othermajor suppliers of cheap consumer elec-tronics soon meant that these prod-ucts-commercial successes when theywere launched-ceased to be majormoney -spinners. But by now his atten-tion was on another market-that forcomputers-where his name would bemade on a wider scale.At this stage, his tactic was to produce a
Fig. 2. Sir Clive Sinclair and his miniaturetelevision receiver.
computer for under £100-vastly lessthan the price of the Apple machinesthen sweeping the world. The result ofSinclair's computer development pro-gramme was a series of machines of in-creasing power, starting with the ZX80and proceeding through the ZX81, theSpectrum (regarded by the experts as thebest Sinclair computer) and the QL (forQuantum Leap).Sir Clive's vital role in British electronicshas been to open up markets for sophis-ticated goods at low prices, sometimes ina way that has benefited competitorsmore than himself.His own computers were not best-sellersin the long term, and his interests in thisfield have now been sold to Amstrad, thefirm that has popularized home comput-ing and word processing in the UnitedKingdom. Another Sinclair product, theC5 electric car, which is no longer on themarket, was even less of a success, thistime because of technical problems withthe vehicle itself.
High technology telephonesBut he shows no signs of bowing out ofthe high technology business. He is adirector and part owner of a new firm,Shaye Communications, which plans anew, miniaturized form of portable tele-phone for business and private users.This time the aim is to produce a port-able telephone at about half the size anda fifth of the price of existing machines,with a retail price of about £200.The idea is to manufacture a telephonethat can be used via a network of publicaccess points, providing a route into thegeneral network and therefore offeringmany advantages over cellular telephony.Because Britain has an acute shortage ofradio spectrum space, the telephoneswould economize on radio spectrumspace and would be less prone to inter-ference and eavesdropping than existingcellular phones.Moreover, Sinclair recently launched hislatest computer, the Z88, a cheap laptopmachine costing about £230, weighingless than 4 kg and under 3 cm thick. Itcannot be sold under his name, however,because Amstrad now has the rights tocall a computer a sinclair. Instead, itis sold by Sir Clive's new firm, theCambridge Computer Company. De-spite missing out on university himself,Sinclair has long found Cambridge a
congenial site for his high technologycompanies.He also has plans to tackle the highestlevels of computer technology via a newfirm called Anamartic, which aims todevelop a wafer scale electronic memory.British banks have put several millionpounds sterling behind the company,which proposes to produce a practicalmemory on which the chips used areconnected on a single wafer, allowingmore speed and scope than existingmemory devices.
Same Sinclair thinkingSinclair must hope that Anamartic will
live up to its name, which comes fromthe Greek for "faultless". His idea ofestablishing a British presence in waferscale memory technology is undoubtedlyambitious. The technology is one thatother British manufacturers would prob-ably choose to import from Japan orelsewhere, but he did run Europe'slargest calculator manufacturer at a timewhen that area was thought to be beyondthe scope of Britain's own electronics in-dustry.Anamartic bears clear signs of tra-ditional Sinclair thinking. If the tech-nology developed at his Metalab devel-opment centre in Cambridge works, itwill provide a breakthrough in cost andsimplicity, which will allow computers to
EE
January 1988be yet cheaper, smaller and moreavailable.The first market Anamartic wants totackle is business automation, includingmanufacturers of office workstations.But anyone who knows Sir Clive's tastefor taking technology to consumermarkets cannot doubt that this will behis next stop if it proves a success.
45
THE RISE ANDRISE OF THE MICRO
by C H Freeman
California's 'Silicon Valley', that conglomerate of many semiconductor and electronic equipmentmanufacturers, has its roots in 'the Fairchild takeover'. Fairchild Semiconductor had been bought out in
1959 by Fairchild Camera and Instrument. With the takeover there came the implementation of new,rigid management structures. The managers of the old style Fairchild found themselves the middle-
management of the 'new' company, and became dissatisfied and disillusioned. Resignations began.Those who resigned began to set up their own semiconductor manufacturing companies, companies
such as the (now) familiar Signetics, Intersil et al emerged. In total, about 50 IC companies have theirroots in Fairchild.
Birth of themicroprocessorIt was in 1968 that Robert Noyce, generalmanager at Fairchild, left the companyto co-found Intel. Noyce had been oneof the founding fathers of FairchildSemiconductor in 1957. He had been in-timately involved with semiconductortechnology for most of his professionallife and had acquired a very considerableexpertise in that field. It was Noyce whopioneered research and development ofthe monolithic integrated circuit at Fair-child Semiconductor, quite literally fromsketchbook to production line in theearly 1960s. Such was his reputation thatventure capital flooded into the newly -founded Intel with Noyce's announce-ment that the company intended tospecialize in memory chips; very much agrowth sector in the IC market of theday.During the next two years, Intel's repu-tation grew, along with the sophisti-cation of its products. By 1970 Intel hadintroduced a 256 bit RAM, stimulating
in earnest the switch from magnetic coreto IC main memory. It was in the sum-mer of 1969, however, that Intel were ap-proached by Busicom, a now -defunctJapanese calculator manufacturer, to de-velop a set of chips for a new line of pro-grammable electronic calculators. Intelhad recently announced the developmentof new IC manufacturing techniques formaking 2,000 transistor chips andBusicom hoped Intel would be able tomake even more sophisticated devices.
Fig. I. The IBM 7351 Computer. Photographcourtesy of PPM Instrumentation.
The Busicom engineers had preparedpreliminary designs which called for 12chips, performing logic and memoryfunctions, in each calculator. By varyingthe 'program' held in the ROM chips, awhole line of calculators with differentcapabilities and functions could be pro-duced. Intel assigned Marcian E. Hoff,Jr to the project. Hoff studied theBusicom designs carefully and con-cluded that, whilst technically feasible,they would be too complicated to pro-duce in a cost-effective manner; therewere simply too many chips per device.The more Hoff considered the problem,the more he became convinced that oneparticular route led to the solution of theproblem. Along that route lay the con-cept of a general-purpose logic chipwhich, like the central processor of acomputer, could perform any logicaltask. Such a micro -sized processor-amicroprocessor - would be program-mable, acting on instructions and dataheld in RAM and ROM.The advantages were clear. Busicom'scalculators could now be re -designed
46 EE
January 1988into cost-effective 4 chip (microproces-sor, ROM, RAM and an I/O interfacechip) machines, rather than the original12 chip uneconomic devices initiallymooted. As Hoff critically examinedthese proposals, he began to see thepromises such a device held. A reducedchip count meant fewer interconnectionsbetween discrete IC's, a simpler, moreflexible and powerful design specifi-cation could be issued. The most ex-citing prospect, however, lay in thedevice's programmability, and program-mability meant versatility. This schemewas accepted by Busicom and in late1970 the first microprocessor, the Intel4004, began rolling off the productionlines.The 4004, as its title suggested, was a 4-bit microprocessor. The 4 -bit architec-ture was, at that time, state-of-the-artstuff. A wider data bus was nottechnically possible at the time. Thismattered little, however, as the 4 -bit ar-chitecture was perfectly suited to pro-cessing single decimal digits. The other 3chips were similarly of limited capa-bility. The ROM, containing thecalculator program, had a capacity ofjust 2k bits, whilst the RAM held 320bits. The calculators were duly producedby Busicom, using the 4 Intel chips andthe few months after the introduction ofthe calculators onto the market saw thechips prove themselves as reliable, flex-ible, cost-effective pieces of hardware.The 4004 had been developed exclusivelyfor Busicom and Intel had no marketingrights to the device whatever. Theeconomics of the calculator business inthe summer of 1971 saw Busicom ask In-tel for a price cut on its chips. In ex-change for this cut, Intel were to receivefull marketing rights to the 4004 and itsassociated support chips. With themarketing rights to the chips firmly es-tablished, Intel launched the chips ontothe public market in November 1971.The advertising hype used to promotethe 'new' MCS-4 family belies the uncer-tainty behind the launch. Intel'smarketing division really did have a'fingers crossed' attitude towards sales.No one was really certain if the publicwould buy the devices. The first advertsays much about the type of applicationenvisaged for the MCS-4 family. Toquote from the advertisement:
"MCS-4 systems provide complete com-puting and control functions for testsystems, data terminals, measuringsystems, numeric control systems andprocess control systems ...MCS-4systems interface easily with switches,keyboards, displays, printers,readers..."Orders were slow. The initial sales levelsattained by the 4004 were not highenough to justify further microprocessordevelopment. It was most unlikely thatthe next Intel microprocessor, the 8008,
2
CUOMO
c1111111111111111111111111101
Fig. 2. Transferring schematics to PCBlayouts by computer. Photograph courtest ofBetroner Ltd.
would have reached research stage had itnot been for a CRT research projectundertaken by the Display Terminal Cor-poration (as they were then known).Texas Instruments and Intel had enteredinto an agreement with DTC, the objectof which was to produce a monolithicprocessor capable of controlling a CRTterminal.A few months after drafting the agree-ment, Texas Instruments pulled out,leaving Intel to continue developmentalone. Intel came up with the goods:almost. The chip worked well, butslowly. Too slowly for its intended appli-cation as a CRT controller and the Intel-DTC contract was dissolved. This left In-tel with an (apparently) unsaleable mi-croprocessor on their hands; what werethey to do? Almost unbelievably, the8008 microprocessor was released ongeneral sale in 1972 on the assumptionthat it would assist sales of memorychips! The Intel microprocessor researchteam were duly disbanded and that, itwas thought, was that. However, it was
Fig. 3. Elektor Electronics' Junior Computerannounced in May 1980 was built bythousands of computer enthusiasts all overthe world.
far from being 'that'. To everyones sur-prise, the 8008 was a big -seller and,almost overnight, microprocessorsbegan to be perceived in a new light: asa growth market with attendant impli-cations of large capital returns. Thechanges the 8008 imbued into the semi-conductor manufacturers manifestedthemselves in the explosion of 'metoo' microprocessor manufacturers:Rockwell, Signetics, Motorola etc. allannounced their intentions to markettheir own microprocessors. Intel, realiz-ing they were on to a good thing, hastilyre -assembled their design team and setthem to work on the next processor, the8080. The commercial desirability ofsoftware compatibility had long beenrealized within the industry and the 8080was designed to be software compatiblewith the 8008. A year after the introduc-tion of the 8008 the 8080 was launchedto an even more enthusiastic reception.Competitors set to design and markettheir own processor chips in direct com-petition with the 8080. It is significantthat the next three years saw the in-troduction of chips now regarded as in-dustry standards: the 6502, the 6800, theZ80, the TMSI000 series etc.By 1976 the microprocessor had estab-lished itself in many applications,proving itself a reliable, efficient, cost-effective component. The semiconduc-tor manufacturers had come to acceptthem as a necessary and lucrative part ofa manufacturing operation. The micro-processor was here to stay!
Enter the minicomputerThe late 1950s had seen the computerevolve into a useful, if difficult and ex-pensive, tool. The computer's place inthe scheme of things seemed clear; scien-tific research, defence depts., largeautomated accounts depts., educationalestablishments-they all found comfort-able uses for their new-found computerpower. The advent of time-sharingsystems saw an even greater degree ofcomputer penetration. Aside from theobvious advantages of allowing manyusers within a single company or organ-isation to simultaneously 'use' theorganisations computer, a new use fortime-sharing systems was spotted. Com-mercial time-sharing services began toappear. Customers of the service woulduse remote terminals to communicatewith the time-sharing computer via'phone lines, buying time on themachine on a minute -by -minute basis.By 1960 time-sharing was very much agrowth sector of the computer marketand was being confidently hailed as the'way of the future'.The big machines required to run anysort of computing operation were stillcostly, however: they were costly in termsof full-time operations staff needed,
costly in terms of physical space andpower required and, above all, costly interms of initial outlay. In the early 1960sa new need for a breed of smaller andrelatively less complex (and hence rela-tively inexpensive) machines was begin-ning to be identified. Thus it was that in1963 the American computer manufac-turers Digital introduced the PDP-8. Incomparison with the mainframes of theday it was a limited machine. The PDP-8ran just one program at a time, pro-cessed data in 12 bit words and had just4K words of memory, but the advantagesthe machine offered were obvious. ThePDP-8 was, physically, about the size ofa large domestic freezer, did not requirea legion of trained support staff and,most importantly, cost just 518,000; afraction of the price of then availablemain-frame computers. The PDP-8 soldextremely well, penetrating both old andnew markets. Scientists, defence andeducational establishments, industrialplants and financial institutions allwelcomed the new minicomputer withopen arms. Every drop in the price of thePDP-8 captured new customers, hithertounable to afford their very own com-puter power.By the end of the '60s a firm dichotomyhad been established, with the main-frame and the minicomputer occupyingtwo different and well-defined marketsectors. A measure of the impact of themini can be gained from the fact that by1971 at least 70 American firms weremanufacturing them, with estimatedsales running into many thousands ofmillions of dollars. The minicomputerhad arrived.
Birth of the microcomputerThe development of the first microcom-puter is a story that is, economicallyspeaking, quite different from the devel-opment of the minicomputer.The first serious, documented researchinto the possibility of producing a home(or personal) computer occured atDigital (again) in the early '70s. It ismost probable that other companies in -t vestigated the personal computer ideaalso, but the Digital investigation re-mains the most documented experience.David Ahl joined Digital in 1969 as amarket researcher. An engineer by trade,Ahl became involved in marketing thecompany's minicomputers to schools.colleges and other 'small' institutions.In addition to the 'regular' type oforders for machines from institutionsand groups, Ahl occasionally receivedorders from individuals for a Digitalmini. This set a train of thoughts in mo-tion in Ahl's mind as he began towonder if there would be a market for asimple, low cost personal computer. In1973 Ahl moved to Digital's research anddevelopment wing, investigating (among
other things) new markets for certainproducts. A separate engineering studywas being simultaneously pursued in theR&D group, the object being to manu-facture a small business computer. Ahlbecame interested in the project andbegan to eagerly investigate themarketing side whilst the engineeringchaps worked on perfecting two proto-types, which were eventually persuadedinto working order in early 1974. Detailsof these prototypes remain sketchy, butone was a 'modified computer terminal',the circuitry being constructed fromdiscrete logic and memory chips; nomicroprocessors were involved in itsconstruction. The second prototype,however, was quite a different prop-osition. More radical and daring in itsdesign philosophy, this machine was aportable self-contained computer, aboutthe size of a thick attache case, compris-ing a monitor, keyboard, floppy discdrive and the main processor itself.Microprocessors were incorporated inthe design of this second machine. InMay 1974 a management committeeconvened at Digital's headquarters todiscuss the future of the project. Thetechnical half of the committee were,understandably, enthusiastic. Themachines worked well (aside fromteething troubles with the floppy discdrive) and could be manufactured econ-omically. The sales department, makingup the other half of the committee, werefar less enthusiastic. Why, it wasreasoned, should educational depart-ments buy the machines? A time-sharingcomputer would be much more cost-effective. Why should the ordinaryhouseholder buy them? There were noconceivable 'home' applications. In theend the salesmen won the day and theproject was dropped. The computer in-dustry, it seemed, was indifferent to theprospect of a personal computer. It mat-tered not that such machines weretechnically feasible and, indeed, couldbe manufactured and sold on a cost-effective basis: no market for suchdevices could be seen. The early develop-ment of the microcomputer thus restedsquarely on the shoulders of the hob -
Fig. 4. A stimulating application of themicrocomputer: Mailbox Chess, a BritishTelecom (Prestel) service.
EE
January 1988byists - people whose primary motiva-tion was technical rather than financial.The introduction of the Intel 8008 mi-croprocessor, the 8 bit successor to the4004, stimulated the interest of oneJonathan A. Titus, an electronics hob-byist. Studying the specifications of the8008, Titus realized that the chip waspowerful enough to run a microcom-puter and set about designing his ownsuch machine. By Autumn 1973 Titushad a working prototype and, wishing toshare the design with other members ofthe hobbyist fraternity, contactedvarious amateur electronics periodicals,enquiring whether they would care topublish his design. The offer was finallytaken up by the (American) 'Radio-Electronics' magazine-a publicationfirmly aimed at the hobbyist. The July1974 edition carried a constructionalarticle on the Mark -8 (as it had beenchristened) together with a parts sourceguide and approximate costing. TheMark -8 was a strictly limited machine.Its innards contained 256 bytes of RAMexpandable up to 16K and no ROM:Titus would have had to pay significantamounts to Intel to produce ROMs tohis specification. Input/output con-sisted of lamp and switch technology.Despite its limitations, interest in theMark -8, and subsequent sales of thebare circuit boards, far exceeded expec-tations. Yet, in spite of this, Titus did noteven consider forming a computercompany, regarding the Mark -8 as moreof an 'educational' project than a com-mercial proposition.
The interest stimulated by the introduc-tion of the Mark -8, coupled with Intel'snewly released 8080 microprocessor,prompted a small electronics companycalled MITS to introduce the Altair8800. The 8800 was designed for theAmerican hobbyist electronics publi-cation 'Popular Electronics'. The pro-ject was intented to be printed as a seriesof constructional articles in the maga-zine and, like the Mark -8, was aimedfirmly at the hobbyist market. The basicmachine was designed with expand-ability very much in mind. The 256 bytememory supplied with the basic kitcould be expanded right up to the maxi-mum 64k bytes possible with the 8080processor by means of slot -in memoryboards. Other peripherals, such as aCRT terminal, printer, alphanumerickeyboard and papertape reader were alsoon the drawing board. Combiningperipherals, memory expansion boardsand the 8800 itself could produce, forthe first time, a really useful, relativelylow cost system. Such a system formedthe first - the very first - fully fledgedpersonal computer on the market. The8800 made its first appearance in theJanuary 1975 edition of Popular Elec-tronics and was an instant sensation.The machine was offered to readers ofthe magazine at a cost of S650 fully
48 EE
January 1988assembled and 5395 in kit form. Suchprices for a machine of such high speci-fication were unheard of and orderspoured into MITS, who had great diffi-culty in fulfilling customers orders.Customers experienced delays of up to 6months (sounds familiar!) beforedelivery of their computers, and thepromised peripherals did not materializeuntil early 1976: one year later (soundseven more familiar!). The popularity ofthe hardware stimulated an 8800 basedsoftware market. A BASIC interpreterwas written for the machine andmarketed, with success, by MITS. The8800 can, justifiably, be said to havebeen the first 'real' personal computer,and its success helped fuel the belief thata significant market for personal com-puters might exist after all.As interest in the Altair 8800 grew, thefirst 'computer clubs', run by and foramateur enthusiasts, were being formedall over America. It was at one such clubin California's Silicon Valley thatStephen \Vozniak, a young self-taughtcomputer engineer, became interested inthe possibility of fabricating a'homebrew' computer. Wozniak exam-ined the specifications of availablemicroprocessors and concluded that thecomprehensive instruction set of thenewly -introduced 6502 would serve hispurposes best. Wozniak set to work,writing a BASIC interpreter before goingon to design and construct the hardware.The finished article was a single boardcomputer with 4K of onboard RAM andcircuitry to enable direct connection to amonitor. Wozniaks friend, StephenJobs, saw a market for the computer andtried to persuade Wozniak to enter intoa business partnership with him. Woz-
niak, meanwhile, had demonstrated theboard to a gathering of other homebrewenthusiasts and the reception had beenso enthusiastic that he had approachedHewlett-Packard, his employer, and triedto interest them in manufacturing hiscomputer. Hewlett-Packard refused,however, doubting the existence of a suf-ficiently large market. Jobs thought dif-ferently. He approached several potentialbuyers and eventually signed a contractfor 100 boards at $500 each. Jobs and\Vozniak went into partnership and theApple Computer Company was born.The Apple I (as it has subsequently be-come known) had no keyboard, ter-minals, disc drives etc. and was clearlytargeted at the hobbyist 'tinkerers'market. In total, Apple sold around 175boards at $500 apiece, leading Jobs andWozniak to consider the project a greatsuccess. So much of a success, in fact,that the pair went to work on a secondmachine, Wozniak taking care of techni-cal development and Jobs looking afterthe business side of Apple. In october1976 Jobs received significant help froma venture capitalist who decided that thenewly -developed Apple II was just rightfor the mass market. With a firmbusiness plan and significant financialbacking, the Apple II went on sale in1977. Sales of the machine rapidly grew,boosted by a hard advertising campaign,and by the end of 1977 the Apple Com-puter Company's annual sales wereestimated to be in the region ofS775 000. Next year's sales were evenbetter and Apple were named as thefastest -growing company in Americanhistory. The software base for themachine grew rapidly, helping to fuelsales to further heights. The personal
computer had arrived.The establishment of a mass -market forthe personal computer shook othermanufacturers out of their complacencyand, in time-honoured fashion, began tojump onto the bandwagon. From hereon, market forces begin to take controland the story of further developments inthe field of personal computing becomesless concerned with technical innovationand more concerned with hardeconomics. One further development,however, merits a brief glance. In 1981IBM entered the fray with its PC, themachine becoming an instant success inits target area (the so-called middle -business market). With IBM sales of thePC well established, the familiarscenario of 'me -too' PC clone manufac-turers, introducing machines in directcompetition with IBM appears again.The resulting economic morass is astartlingly familiar cocktail of marketforces.
ConclusionWith a well established trichotomy ofmainframe/mini/micro the future maywell see significant technical develop-ments, but in a capitalistic economy,where market forces reign supreme, itwill be the businessmen, and not thescientist, who will decide what sees thelight of day. With the benefit of hind-sight it is difficult to imagine that in thefuture technical constraints, rather thaneconomic ones, will form the sword ofDamocles over continued development.Time alone will tell.
EUROPEAN EDUCATIONSOFTWARE: A NEW APPROACH
TO EFFECTIVE LEARNING
Considering the growing importance ofcomputers in modern education, it isironical that schoolchildren all overEurope are currently missing out on thevast potential for effective learning nowmade possible by microprocessor tech-nology.The reasons for this are commercial.Despite the millions of young people inneed of educational computer materials,the European market is seen as too smallto attract the interest of those who might
by Christopher Dunn
put matters right.Fundamentally, the problem is that thereare so many different types of computerwith no standard operating system.Modifying software to suit each typeputs too heavy a cost on publishing.Now all that is changing.European Educational Software (E2S), abright young British company based inCambridge, has brought together theresources needed to overcome the prob-lems. It is already well on the way to its
objective of originating and distributingrelevant computer based learningmaterials for every level of education,from primary schools to in-service in-dustrial training.The company has identified the marketin Europe as about 300 million youngpeople in need of computer software tohelp them get an education that willequip them for living in the 21st century,not forgetting the 60 million adultsworking in industrial and commercial
companies who have urgent need of in-service training materials as well.
The virtual machineThe first task for E2S was to create theenabling technology that would stan-dardize microcomputer operation. Theresult of its development work is aunique capability, at the heart of whichare two key products.First is the Virtual Machine, a softwaresystem that creates a common interfacebetween most makes of micro. Machineindependence means a single version ofa program can now be run on virtuallyany microcomputer.Secondly, there is the Author's Toolbox,a suite of utility programs designed tohelp authors design educational soft-ware to run on the Virtual Machine. TheToolbox provides a framework for stan-dardizing software and supportive toolswhich allow users who have limited com-puting skills to generate their own pro-grams.With this capability, E2S is now in a pos-ition to generate a library of educationalapplication programs suitable for eachof the principal countries of Europe. In-itial activities are concentrating on seventerritories: the United Kingdom, France,West Germany, the Netherlands, Italy,Scandinavia and Spain.
Innovation and co-operationIn plain business terms, E2S is a perfectexample of a company identifying a gapin the market, then setting out with pur-pose and dedication to serve that need.What separates it from the more conven-tional business approach, however, is theunique physical structure it has createdas the means to achieve its business ob-jectives. It aims at breaking totally newground in productive co-operation be-tween industry and education-and be-tween nations."We are opening up channels betweenindustry, commerce and education on apan-European scale", says ChristopherCurry, former managing director ofAcorn Computers and a co-founder ofE2S."We have involved representatives of allprofessional sectors which have an in-terest in education and placed themalongside our own technical skills andbusiness resources. As a result, we arerapidly overcoming those obstacles that,in the past, have discouraged effectivecreation of educational software."
Joint development projectsAround its central executive body, it hasassembled a structure of specialist ad-
visers who assist in shaping policies andin defining the world's requirements ofeducation at all levels.The executive is advised by a board thatincludes British and other European in-dustrialists and investors, and a panelbringing together key people from allsectors with an interest in promotingeducational advancement. This includeseducation authority advisers, poli-ticians, industrial training specialists,and representatives of governmentagencies.Where appropriate, the company de-velops products in association with com-mercial and industrial sponsors. Thisarea of co-operation provides obviouspromotional attractions for sponsorsand, in turn, enhances the relevance ofits software to contemporary issues in in-dustry and commerce.It also collaborates with academic,teaching and training institutions to de-velop innovative computer based train-ing materials.E2S also works in partnership withleading software publishers in Britainand continental Europe, providing twoway channels through which software isboth acquired for development anddistributed for marketing. Most of thesepartnerships include joint developmentprojects supported under the Eurekascheme, the European government in-itiative set up to foster the developmentand marketing of new technologicalproducts.
Franchise agreementThe company draws in software fromEureka partners and directly fromauthors, while new programs are also de-signed by its own team of softwaredevelopers. A franchise agreement givespartners access to the Virtual Machineand Author's Toolbox, enabling them toconvert existing software and to developnew programs for use on any computerwhich has the Virtual Machine interface.Whether acquired or developed, allproducts are subjected to the same rigor-ous standardization and approval beforerelease through its partners for
Schoolchildren learning with the aid of com-puter technology.
EE
January 1988European distribution. Languagetranslation and the adjustment ofspecific components to suit individualcountries, where necessary, are carriedout in the relevant country.The copying and distribution of soft-ware to schools within a local educationauthority is governed by a self -policinglicensing system. The education auth-ority buys a master copy, labelled withits own unique code, which it thenduplicates as necessary. The code allowsthe authority to keep a check on anyunauthorized copying of the software.In tune with contemporary thinking ineducation, many of the company's newapplications programs are designed to belargely open-ended or content -free. Theymake creative use of simulation andgames techniques, designed to bringstudents to conclusions and solutions byreason and not by rote.Now that E2S has bridged the gap ineducational software, millions ofchildren all over Europe can look for-ward to the benefits of a wider avail-ability of computer aided learning.
49
European Educational Software PLC,8/9 Bridge Street, Cambridge CB2 1UA.Tel: (0223) 462200.
European Educational Software PLC,La Santoline, Chemin de Bibemus,13100 Aix en Provence, France. Tel: + 42961554.
50 EE
January 1988
LETTERS LETTERS LETTERSLetters of a general nature, or expressing anopinion, or concerning a matter of commoninterest in the fields of electronics, telecom-munications, computers, and relateddisciplines, should be addressed to TheEditor. Their publication in Elektor Elec-tronics is at the discretion of the Editor.
Sir-I am writing to amend the informationgiven on p.48 of the November 1987 issue ofElektor Electronics concerning BritishStandards.The concluding paragraph, which states thatBritish Standards are available from BSI inLondon, is incorrect. The BSI Head Office isin London, but the Sales Office is in LinfordWood, Milton Keynes MK14 6LE.Finally, it is not a well-known fact that eachcounty in the UK has at least one or two largelibraries that keep complete reference setsof British Standards for general consultation.
Christine Fowler (Mrs), BSc, ALALibrarian, Plessey Defence Systems Ltd
Sir-Reports such as your Translating speechby computer (EE, November 1987) fill meand, no doubt, many of my fellow translatorsthe world over with dismay as to the wayclaims of computer translation capabilitiesare presented to the public. No professionaltranslating agency or organization can poss-ibly accept or endorse the claims made incertain promotional literature or adver-tisements.It is, of course, true that many organizations inEurope, Japan, and the USA, working on thedevelopment of speech translating softwarehave met some measure of success, but onlyinsofar the basics of a language are concern-ed. The translating of one or more wordsfrom one language into another is simple,and this is probably behind the systemdeveloped by British Telecom.It is, however, quite a different matter tomachine -translate any language to thehighest possible standards that humantranslators can achieve. English idiom (Gk."A manifestation of the peculiar") is taxingenough for the human brain, and since I con-sider the human brain to remain always
superior to any computer, I cannot believethat computers will be able to take over high -quality translation of complex language for avery long time to come. They will, of course,be suitable for translating simple sentences.Having said that, it is, of course, agreed thatsystems which enable us to use multilingualfonts, check for consistent use of terms, andcompile glossaries are more than welcome.
Chris WaltersMunich
As a translator and linguist, I largely agreewith you, but I look forward with interest tothe Fist reports from the Translating and theComputer Conference held in London lastNovember. Ed.
PEOPLE PEOPLE PEOPLE PEOPLE BEAMA's Deputy Director -General, MrHarold Bradshaw, MBE, has retiredafter 48 years in the industry. He will actas an advisor until July this year andprobably for some time thereafter.
Mr Geoffrey Wilson, Chairman of theDelta Group PLC, has been elected the1987/88 President of BEAMA, in suc-cession to Sir William Barlow.
Mr Michael Parkinson, Chairman andChief Executive of Crompton ParkinsonLtd, Mr T.W.B. Sallit, a director of theHawker Siddeley Group PLC, and MrE.J. Sims, an associate director of theGeneral Electric Company PLC, havebeen reappointed BEAMA counsellorsfor 1987/88.
Mr W.J. Wordingham has been ap-pointed Director of three of the associ-ations federated in BEAMA: the Elec-trical and Electronic Insulation Associ-ation (EEIA), the Membrane Switch
Manufacturers' Association (\ISMA),and the Power Generation Association(PGA).
Mr Gordon Gaddes, Director -General ofBEAMA, has been elected Deputy Presi-dent of CENELEC, representing theEEC countries. CENELEC is theEuropean Committee for Elec-trotechnical Standardization in westernEurope and is representative of all EECand EFTA countries.
Mr Roy Gibson, the former Director -General of the European Space Agency,has joined INMARSAT (InternationalMaritime Satellite Organization) asspecial adviser to Director -General, OlafLundberg.
The Rt Hon. Norman Tebbit, MP, hasbeen appointed a non -executive directorof British Telecom.
Peter H. Rose, who is returning from
medical leave of absence, has been ap-pointed to the newly -created position ofSenior Director of Eaton SemiconductorTechnology.
Highland Electronics has appointedPatricia Hunt as Regional SalesManager for the South East of England.
HHB Europe have appointed MikeWilliams, BSc as Major AccountManager.
Grundig International has appointedGordon Mackay as National AccountSales Manager.
David Palser is the new Head of Test andMeasurement Product Sales for Elec-tronic Brokers.
TEST & MEASURING EQUIPMENTJulian Nolan's discourse on dual -trace oscilloscopes is continued this month with reviews of the Gould
0S300 and the Grundig M020.
Gould 0S300Gould have a high reputation for thequality and robustness of theiroscilloscopes and the OS300 follows inthis trend, in spite of it being thecheapest scope manufactured by Gould.The Gould range of oscilloscopes com-prises real-time and digital storage unitsat prices well over £18,000 for a completedigital acquisition system. Gould alsomanufacture a wide range of otherspecialized electronic products such asdigital chart recorders, logic analysersand emulators, etc. Gould also haveavailable a wide range of accesories forits oscilloscopes, such as protective car-rying cases, rack mounting kits and of,course, probes.The 0S300 is delivered in an easily ident-ifiable blue/white box and is well pro-tected by the standard polystyrene orsimilar cutouts which surround it. Thescope is supplied with a comprehensivemanual and, I believe, a mains lead (thereview model was not). Since the mainsconnection is made via a standard IECstyle socket, there is no problem shouldthe lead supplied be lost or too short.The scope itself is quite small as far asthe height and the width are concerned,although the depth is a relatively long460 mm. It weighs only 5.8 kg. TheOS300 is equipped with a multipositionaluminium stand (with plastic handgripat centre). However, a price is paid forthe multiple positions of the handle inthat the sides have to be pulled out tofacilitate movement. This is not as easyas it sounds when the stand needs to berotated by 90° or more, owing to the in-flexible nature of the aluminium.Voltage selection can be made for a100 V, 120 V, 220 V or 240 V line by 2slider switches provided on the backpanel, on which Z modulation and,unusually, ramp -out sockets as well asground are provided.The front panel is clearly laid out. Alltrigger functions are controlled by sevenpush-button switches, though the factthat two switches have to be latched sim-ultaneously to enable Ext or TV trigger-ing could be initially inconvenient.Alternate or chopped modes and TV lineor frame triggering is automaticallyselected by the timebase switch, beingdependent upon the sweep speed selec-ted. Although bringing about a slightdecrease in versatility when the scope isused in these modes, this arrangement is,however, justified by the resulting in-
Part 1: dual -trace oscilloscopes (B)
Fig. 7. Gould 0S300 oscilloscope
crease in ease of use of the scope.Curiously, the on/off switch is com-bined with the intensity control, which isslightly inconvenient as the intensitycontrol is reset during each on/off oper-ation. Due to the quick heat cathode ofthe CRT, the intensity control can be setany time after the 10 seconds or sowarm-up time of the CRT, which limitsthe inconvenience. The CRT bezel is notequipped with camera mounting facility,but Gould point out in the manual thatthis problem can be solved by holding asuitable camera against the tube face.As can be seen from the specification,the maximum Y amplifier sensitivity is2 mV/div, which is effective across the20 MHz bandwidth ( -3 dB). This ex-tends upto 10 V/div calibrated or25 V/div uncalibrated. The wide at-tenuation range allows a good range ofinput signals to be accurately measured.The good sensitivity permits a x 10probe to be used with low voltage highimpedance sources for the minimumminimum loading. On the whole, the Yamplifiers performed well, having agood response up their specified band-width and risetime but it was noticeablethat the response did dip sharply after25 MHz. As on most modern scopes inthis price range, the input stage of thepre -preamplifiers is formed by FETs,here in a source follower configuration.The use of FETs obviously helps providethe high input impedance which is a vitalquality of any oscilloscope. In commonwith those on some oiher oscilloscopesin this range, the Y amplifiers exhibit asmall amount of drift (approximately1/2 cm), during the 'warm-up' periodthus making readjustment of thehorizontal trace position necessary, afterthe initial 10 minutes of operation. Anaccuarate 1 V peak to peak (± 2cro),1 kHz square wave for x 10 probe cali-
bration is provided.The trigger performance of the 0S300 isgood, with triggering possible on a verylarge range of signals without major ad-justment of the trigger threshold. Com-plex signal patterns are also handledwithout too many problems, although adigitized sine wave with its third MSB bitmissing did require some fine adjust-ment of the triggering level to obtain astable trace. High frequency triggeringwas also good with triggering on wave-forms with frequencies very considerablyhigher then the 20 MHz Y amplifierbandwidth. The triggering selectors con-sist of a bank of 6 push-button switches,some of which have dual functions, e.g.,two being depressed for one function.This leads to a slight decrease in flexi-bilty in some modes such as externaltriggering or TV sync, although it has tobe said that this is minimal. Line orframe sync. is selected in the TV modeby the timebase switch and, although intheory this may appear again to besomewhat inflexible, in practice this isnot so, as the automatic timebasc selec-tion is quicker and easier than manualswitching. This also applies to choppedor alternate switching, which is alsoselected by the timebase speed. Thechopping frequency is a notable500 kHz, enabling relatively high fre-quency signals to be measured more ac-curately in this mode rather than in thealternate mode where, because of itsnature, phase comparisons of waveformscan be inaccurate.Sensitivity is good across the entirebandwidth ranging from about 1.5 mmat 2 MHz to 4 mm at 20 MHz. TheOS300 still maintained a reasonable sen-sitivity at frequencies above 20 MHz.Alternate channel triggering of thetimebase is not available and because ofthis, synchronization of the two inputwaveforms is necessary in dual tracemode in order to obtain a stable trace.Trigger coupling is also limited by theabsence of low frequency or high fre-quency filters which are usually providedin scopes in this price range. Where thesewould normally be necessary, typicallywhere the required trigger signal has avery high content of LF for an HF waveor HF for an LF wave modulation, theproblem can usually be got around bycritical adjustment of the triggeringthreshold. This is, however, not alwaysthe case and consequently necessitatesthe use of the external trigger facility.
111 EE
January 1988
The remaining trigger functions arefairly standard ones such as AC or DCcoupling etc.The timebase speed selection switch is tothe right of the scope and has a total of18 speeds ranging from 0.2 s/div to0.5 ;is/div. This can be expanded to50 ns/div by a x 10 switch, makingviewing of fast risetime waveforms easy.My main criticism of the 0S300 is itsbelow average focusing, which is evidentat most time base speeds, and results ina lack of sharpness and definition thatsome other scopes with 2 kV tubespossess. This is naturally mostnoticeable on the x 10 timebase speeds.The 0S300's lack of automatic focusingdoes not help in the matter, so that aslight readjustment of the focusing con-trol is necessary when changing over awide range of timebase speeds. Thebrightness on the scope is admitedly verygood for a 2 kV accelerating potentialtube, but even at low intensity levels thetrace still insists on appearing slightlydefocused-both the focus andastigmatism controls level and certainlythe brightness of the Mullard quick -heat -cathode CRT is very good. Thisquick heat cathode, as used in manymodern TV's, enables the scope to be-come operational very much quicker(under 10 secs) than other instruments inits class (typically 30 secs).The Gould OS300 is also fitted with Zmodulation and, unusually, a ramp out-put. This output, although being only3.5 V in amplitude (peak) can easily beamplified if necessary and used to drivesuch things as, for example, a VCOwhich in conjunction with a swept LOdetector could be used to provide a spec-trum analyser type display. This perhapsslightly ambitious application is one ofmany for which the ramp output can beused, as it ensures the synchronizationof any external device with the scopethus producing a locked display. It is sur-prising that this helpful feature is not in-cluded in more scopes.Internal construction is centred around asingle large epoxy glass PCB whichhouses the vast majority of the circuitry,while a smaller vertical PCB contains theY amplifiers and some timebase compo-nents. The Y amplifiers themselves arefully screened. Parts of these amplifiersare constructed from IC's which arehoused in TO88 metal packages forfurther noise immunization. Overall in-ternal construction is very neat: there arevery few interconnecting wires, and,despite the fact that both PCBs aresingle -sided, also very few wire links.The PCBs and other large componentssuch as the tube and the high -qualitymains transformer are all mounted on arobust steel subframe onto which thesheet metal outer housing is fitted. Alarge part of the CRT is shrouded toguard against X-ray radiation etc. Mostof the components used in the 0S300 are
Fig. 8. Close-up of 0S300 controls
of a high standard, but I have my doubtsabout the potentiometers used for someof the continuously variable front panelcontrols, which have a somewhat unevenmovement, and upon inspection prove tobe little more than presets. There is,however, no reason why these shouldprove to be unreliable. On the subject ofpresets, allure clearly labelled on the silkscreened PCB and all are easily access-ible. Components used in the scopecome from a wide range of manufac-turers ranging from National Semicon-ductor for some of the ICs to MagneticShields Ltd for the CRT shield.The manual for the Gould is particularlygood, totalling 26 pages plus the A3 sizecircuit diagrams. It covers the 0S300 insome detail including sections on oper-ation, maintenance and calibration.There is also a detailed circuit descrip-tion so fault finding, etc., should presentno problems. In addition, there are alarge number of diagrams, both circuitand mechanical, which should be of helpin many circumstances.
ConclusionThe Gould 0S300 has its good and badpoints. The good points include the ex-cellent quality of construction, its rug-gedness, the quick -heat cathode of theCRT, ease of operation, and the severaltime saving features. It is also worthbearing in mind that the instrumentundergoes a large number of qualitycontrol procedures during and after con-struction such as the 36 -hour soak testwhich is carried out on the completed in-strument. While these are in no wayunique to Gould, they do appear to be
Fig. 9. Internal view of 0S3110
Table 5. Specification
ELECTRICAL CHARACTERISTICSDesigned for IEC 348 Cat. 1.Line voltage: - 100,120,220,240 VAC
± 10%; externally adjustable. Power50 Watts. Line frequency 45...440 Hz.
MECHANICAL CONSTRUCTIONDimensions: -W 305 mm, H 140 mm,D 460 mm
Housing: - Sheet steelWeight: - approx. 5.8 kg
Y AMPLIFIER ETC.Coupling AC, Gnd or DC on bothchannels.
Operating modes: -CH 1 aloneCH 2 alone or invertedCH 2 4- CH 1Alternate or chopped (500 kHz)CH 1/CH 2, switching automatic.Frequency range (full deflection)0...20 MHz ( -3 dBi (DC coupled)
Risetime < 17.5 nsec.Deflection factor 12 steps;2 mVidiv...10 V/div ± 3% (Min25 Vidiv, fine control fully anti cw).
Input coupling AC, DC or Gnd.Input impedance 1 MQ/28 pF; Max inputvoltage 400 V DC or pk AC. Inputprotected.
Input impedance 1 MQ/28 pF; Max inputvoltage 400 V DC or pk AC. Inputprotected.
X -Y MODECH 1 X-axis, CH 2 Y-axis. Bandwidth DC -
1 MHz ( -3 dB). Less than r phase shiftat 50 kHz.
TIMEBASEDeflection factor 18 steps:0.5 psec . .0.2 sec/div = 3% in1/2/5 sequence. Min speed 0.5 sec/div(fine control fully anti cw).
Expansion x 10, extends max. timebasespeed to 50 nsec/div. Expansion error:s ± 2% extra.
TRIGGERINGTrigger modes: - Auto (bright line),
Normal, TV (active line or frame sync.automatically selected from timebasespeed.)
Trigger coupling: - AC, DC.Trigger sources: - CH 1, CH 2, Ext.Triggering slope: - positive or negative.switchable.
Trigger sensitivity: - Internal (DC) 5 mmto 20 MHz. External (DC) 400 mV to20 MHz; All modes.
MISCELLANEOUSCRT-make Mullard, measuring screen
100 x 80 mm, accelerating potential2 kV, quick -heat cathode. Protectivescreen built into bezel.
Compensation signal for divider probe,amplitude approx. 1 V ± 2%; frequency1 kHz.
Z modulation-input by 4 mm socket: 2 Vvisible mod. + 40 V complete blanking.
Ramp out... ± 3.5 V peak from 5 kQ.Covered by 2 year warranty.
EE
January 1988particularly stringent in this case, beingbacked up by the instrument's two yearguarantee. As to the bad points, mymain criticisms are the focusing of theCRT and the lack of alternate triggering.Summing up, the Gould 0S300 oscillo-scope is probably best suited to environ-ments where its high grade of construc-tion will be valued, such as educationalestablishments or servicing departments,and its few shortcomings will not be no-ticed.
The Gould 0S300 was supplied byGould Electronics Ltd., InstrumentSystems, Roebuck Road, Hainault, Il-ford Essex IG6 3UE. It retails at £342 +VAT.
No other oscilloscopes under £1,000 aremanufactured by Gould.
Table 6.
1
CATEGORYUnsatis-factory
Satis-factory Good
VeryGood Excellent
TRIGGER FACILITIESTRIGGER PERFORMANCECRT BRIGHTNESSCRT FOCUSING1' AMP PERFORMANCEINTERNAL CONSTRUCTIONEXTERNAL CONSTRUCTIONOVERALL SPECIFICATIONEASE OF USEMANUALX!Y PERFORMANCE
x
x
x
xx
x
x
x
x
x
x
Grundig M020The German company of Grundig haslong been renowned for its high qualityconsumer products, and, perhaps notsurprisingly, the Grundig M020 largelykeeps to this mould. The M020 is one of3 oscilloscopes manufactured by Grun-dig aimed at the 'under £1000 market':the others being the M022 and theM053. The M020 is the cheapest in thisrange retailing at £365 + VAT. Thisprice, in common with many otherforeign products, has been adversly af-fected by the exchange rates: it was £66pounds lower at £299 in August of 1986.The Grundig M020 arrived well packedin a cardboard box, substantially largerthan the instrument itself, which was en-cased in a number of polystyrenecutouts. On removal, the Grundigturned out to be fitted with a two pincontinental plug, which entails eitherusing an adaptor or, more preferably,refitting with a 13 amp plug. The leadfeeds straight into the scope and is notfitted with a socket. This is unfortunatebecause it is of only average length andin some situations a longer lead may berequired. The stand is moulded in atough plastic and is well up to sup-porting the heavier than average(81/2 kg) M020, but it has only one pos-t ition. The front panel is clearly laid out,although the vertical mode switches areinitially confusing. However, the methodof using two switches for the verticalmode pays dividends when in the X -Ymode, which due to the design is ex-tremely versatile. Upon inspection of themanual, it would be all too easy to de-scribe the Grundig as a run-of-the-milloscilloscope, with perhaps the notablefeature in this price range of havingautomatic peak value triggering, but thisis not the case. A summary of thespecifications is provided in Table 7.As can be seen, the maximum calibrated
Fig. 10. The Grundig M020 oscilloscope
Y amplifier sensitivity is 5 mV/cmalthough, unusually, the fine adjustmentcontrol calibrated to give a maximumgain of x 2.5 actually increases the sensi-tivity, resulting in a sensitivity of 2 mV.I found this to be accurately calibrated,although the system of using the finecontrol to increase sensitivity was at firstoff-putting as on most scopes itdecreases sensitivity. The Y amps per-formed well handling an almost fullheight (6 cm) sine wave with littledegradation in height over the full20 MHz bandwidth of the instrument.When fed with a fast rise time pulse, theY amps responded within the specifiedlimit of 17.5 ns. It was pleasing to notethat the range extends to 20 V/cm,which permits the measurement of rela-tively high voltages in the dual tracemode without any overlapping of traces,
11
e
ala Past OuPLIKI wirrim. -MOW.
COPP
Onaaa
'ma .0a 76 -
L I Nip
,1101. 11.0aim ga.
CY*
C111
11.1t
Fig. It Close-up of \1020 controls
while using a x 10 probe. Both channelsare invertable, making for easier subtrac-ting, as no swapping of connectors is re-quired for changing the subtractionwaveform. One minor but annoyingpoint was that both Y amplifiers on thereview model exhibited a small amountof drift (about 1/2 cm) over the fist 10minutes of operation, necessitating anadjustment in their trace position. Thisdoes not, however, affect normalmeasurements outside the 'warm up'time during which I found both channelsvery stable. A 1 V peak -to -peak 1 kHzprobe calibration waveform is providedhaving a rise time of 5 /IS.The M020 boasts an automatic peakvalue trigger, which enables the scope tolock on to virtually any repetitive wave-form of above 7 mm in amplitude, with-out adjustment of the triggeringthreshold. This has advantages in thatalteration of the manual trigger value isnot necessary for variations in waveformamplitude etc. thus making operationeasier. Triggering on the M020 is com-prehensive: auto (peak triggering notbright line); normal, i.e. no bright line;or auto trigger and TV frame and linemodes. On top of this, it also featuresAC, DC, LF (fs:_-_-.8 kHz) and HF(fo -10 kHz) coupling. The source forthese functions can be selected fromeither CHI, CH2, LINE or an externalsource. A notable exception here is thatin common with most otheroscilloscopes in this price range, alter-nate triggering from CH.1 and CH.2 isnot available. This means that whenboth channels are being used both theinput wavforms must be synchronized toa single source to enable both trces to bestable.Selection of the trigger mode is by anumber of lever operated switched.These are not only easy and convenientto operate, but also provide a clear indi-
54 EE
January 1988
cation of which function has been selec-ted; they are also used for vertical modeselection. I found the triggering facilitiesof the Grundig very good, although aslightly more sensitive auto trigger func-tion would have saved adjustment of theY amps in a few cases. The scope trig-gered successfully on a large variety ofwaveforms ranging from NRZ pulses toa heavily modulated sine wave at20 MHz. In some cases, it was necessaryto switch into normal mode to obtain afully stable trace, but this was relativelyrare. The auto trigger function doeshowever take a few tenths of a second tolock onto a signal, and during this timethe display is blanked, producing arather disconcerting flickering if the Yamplifiers range is changed or the trig-ger signal falls below the triggerthreshold. Despite this, the auto triggerfunction performed very well, y itsusefulness extended by the inclusion of aLED indicator to show the trigger stateof the scope.Time base speed selection is by means ofan 18 -position switch and ranges from0.2 sec/div to 0.5 ,usec/div, a x 10 switchincreasing this to 50 ns/div. A fine ad-justment control is capable of slowingthe trace down by a factor of up to 21/2.The focusing and brightness of theVALVO CRT were very good even atmaximum sweep speeds, although therewas a small amount of defocusing whenthe x 10 control was brought into oper-ation, the intensity control beingsuitably advanced to compensate for theloss in brightness. Defocusing was alsoobserved when the intensity control wasat maximum. These problems are reallyto be expected with a 2 kV tube as fittedto virtually every scope under £500. Themaximum sweep speed ( x 10) proved tobe fast enough for observing signals atthe full 20 MHz bandwidth, the over-shoot on a 10 MHz square wave beingclearly visible. The CRT is clearlymarked with the appropriate gradua-tions for rise time measurement, whichis made easy by the comprehensive trig-gering facilities. There is no filter infront of the CRT so that the colour ofthe CRT appears true: greyish white witha red graticule. Although Z modulationis not fitted as standard I was surprisedto read in the manual that it can easilybe fitted by the addition of one BNCsocket connected to a clearly markedpoint on the PCB. The bright level isspecified as X0.8 V and the dark level as
2.0 V.Overall the construction of the GrundigM020 appears to be excellent for an os-cilloscope in its price range. The case issolidly constructed from relatively heavygauge steel and, since the instrumentonly consumes 35 Watts of power, noventilation slots are necessary. The frontand rear surrounds are cast metal: mostof the front panel is plastic, and the rearis of sheet steel. The use of steel does, of
Fig. 12. Internal iew of M020
course, have its drawbacks in terms ofweight over the more frequently usedaluminium, but in my view the extrastrenght obtained compensates for this.On removal of the top cover the internallayout was found to be very neat, with aminimum of interconnecting wires. Themajority of the components aremounted on two fibreglass PCBs: onelarge board houses the power supplies, Yamplifiers, blanking circuit etc, and asmaller board houses the ramp gener-ator, triggering filters etc. Both boardsare single sided, the larger of the twohaving a large number of wire links.Connections between the boards aremade by a thick form of ribbon cable.Both boards are silk screened, and arefitted with numerous test pins, all ofwhich are clearly labelled as to theirfunction and, where appropriate, ex-pected voltage. The majority of the inte-grated circuits are manufactured byTexas Instruments, although several, in-cluding the input amplifiers, are from.other manufacturers. The inputamplifiers are soundly constructed andfully shrouded with sheet metal, as is theCRT. The attenuation range switches ap-pear to be of a high quality construc-tion, and have a positive action. Oneminor point is that both the attenuationswitches and the timebase switch have noend stops, so that it is all too easy to ac-cidentally switch from the maximumrange to the minimum or vice versa. Per-sonally, I didn't like this because of thereason outlined above, but this a purelypersonal view. The timebase switch,which is based around a small verticallymounted PCB, did not appear to be ofsuch quite good quality as the attenuatorswitches, but was still acceptable. Allother components appeared to be of avery high quality.Servicing or calibration of the scopeshould be no problem, as most of thecomponents are fairly standard,although there are several thick film re-sistor networks. The large number ofmarked test points greatly eases fault-finding and calibration. Unfortunately,the manual only gives a brief list of theinternal presets and suitable calibrationprocedures. None the less, these arequite helpful and should be sufficientfor most users requirements. The
Table 7. Specification
ELECTRICAL CHARACTERISTICS: -Protection class 1.
Line voltage: - 110,220,240 VAC± 10%; internally adjustable. Power35 Watts. Line frequency 45... 65 Hz.
MECHANICAL CONSTRUCTIONDimensions: -W 375 mm, H 160 mm.
D 430 mmHousing: - sheet steelWeight: - approx. 8.5 kg
Y AMPLIFIER ETC.Operating modes: -CH 1 alone or invertedCH 2 alone or invertedCH 1 ÷ CH 2alternate or chopped (250 kHz) CH 1/CH 2
Frequency range (6 cm deflection)0...20 MHz (-3 dB).
Risetime s 17.5 nsec.Deflection factor 12 steps:
5 mV/div ... 20 V/div ± 3%(Max. 2 mV; fine control full cw).
Input coupling AC. DC or Gnd.Input impedance 1 MQ/25 pF, Max inputvoltage 400 V (peak including DCvoltage).
X -Y MODECH 1 X-axis, CH 2 Y-axis. BandwidthDC -1 MHz (- 3 dB). Less than 3° phaseshift at 50 kHz.
TIMEBASEDeflection factor 0.5 psec/div...0.2 secidiv + 3% with1/2/5 divisions.
Expansion x 10; extends max. timebasespeed to 50 nsec/div; expansion error
± 2% extra.
TRIGGERINGTrigger modes: - Auto with peak value
triggering from f>10 Hz; Normal; ActiveTV frame and line sync.
Trigger coupling: - AC, DC,LF (f8=8 kHz), HF (fg=10 kHz).
Trigger sources: - CH 1, CH 2. Line, Ext.Triggering slope: - positive or negative,
sl.vitchable.Triggering sensitivity: - Internal 5_ 1 cmat 20 MHz, External -500 mV at20 MHz, Normal mode.
Trigger signal indicator: - green LED.
MISCELLANEOUSCRT -make VALVO, measuring screen100 x 80 mm; accelerating voltage 2 kV;beam rotation by front panel adjustment.
Compensation signal for divider probe,amplitude aprox. 1 VP, frequency 1 kHz.
Z modulation -possible by addition of BNCsocket, bright level .s0.8 V, dark levela 2.0 V.
Covered by 1 year warranty.
EE
January 1988manual itself is quite good, covering atotal of 16 pages (plus block and circuitdiagrams), of which 8 pages is inGerman, the remainder being theEnglish translation. Overall, the A4 sizemanual provided a good, if short, sum-mary of the functions, set-up pro-cedures, and applications of the M020.In addition, details on fitting the Z-modulation socket, test characteristicsand detailed specifications were also in-cluded. The circuit diagrams themselvesare very clearly laid out and easy tofollow, as is the block diagram. Theseare provided on fairly large pieces ofpaper which makes reference easy.
ConclusionThe Grundig M020 is certainly worthconsidering, its particular strengths ly-ing in its construction and advancedtriggering facilities. The construction isvery good for an oscilloscope in thisprice range and the two-year guaranteeoffered with the scope reinforces this.The triggering facilities are good, withthe particular bonus of automatic peakvalue triggering, as well as comprehen-sive filtering. It is a pity, however, thatalternate triggering is not available. TheCRT and drive circuitry are also very
Table 8.
CATEGORYUnsatis-factory
Satis-factory Good
VeryGood Excellent
TRIGGER FACIUTIESTRIGGER PERFORMANCECRT BRIGHTNESSCRT FOCUSINGY AMP PERFORMANCEINTERNAL CONSTRUCTIONEXTERNAL CONSTRUCTIONOVERALL SPECIFICATIONEASE OF USEMANUALX/Y PERFORMANCE
x
x
x
x
xx
x
x
x
x
x
good, producing a clear and bright trace,even at the maximum deflection speed.To sum up, the Grundig M020 is cer-tainly worth buying if you require a well-built oscilloscope with a good range offacilities.The Grundig M020 oscilloscope wassupplied by Electronic Brokers andretails at £365 plus VAT. ElectronicBrokers are at 140-146 Camden Street,London NW1 OPB; telephone 01-2677070.
Other Grundig scopes under£1000M022-As the M020 plus automatictimebase selection, triggerable secondtimebase, hold off control, Z mod. Cur-rent price £499 + VAT.
M053-As the M022 plus alternatingsecond timebase, digital timebase dis-play, 50 MHz bandwidth, delay timemultiplier. Current price £750 + VAT.
FRONT-END FOR SW RECEIVERThere are many conflicting technical re-quirements for a good -quality front-endin an SW receiver. The noise figure andthe intermodulation level should be low,the RF insulation between ports LO, RFand IF should be high, and some ampli-fication is desirable. The Type SL6440high level RF mixer from Plessey ensuresa noise figure of around 10 dB, and of-fers sufficient suppression of the LOsignal. The signal applied to the RF in-put (B) of the front-end is passedthrough a low-pass filter with a cut-offfrequency of 32 MHz and an output im-pedance of 500 Q. The open collectoroutput of mixer IC, has a relatively highimpedance, which necessitates the use ofTr, and R5 for correct matching to48 MHz crystal filter FL,. The fixed im-pedance of this filter for signals outsideits pass -band helps to keep the inter-modulation distortion low. TrimmersC13 and Cla are aligned for a maximumflat pass -band at minimum loss. Themixer's intermodulation characteristicscan be optimized by careful dimension-ing of R, and R2, provided the ampli-tude of the local oscillator signal isstable. A third -order intercept point of33 dBm was achieved in a prototype.The mixer IC gets fairly warm, andshould be cooled with a heat -sink.
The RF transformers are wound asfollows (use 30SWG enamelled wire):Tr,: the primary winding is' 10 +10bifilar turns, the secondary is 10 turns,on a Type T50-12 ferrite core.
Tr2: the primary winding is 2 turns, thesecondary 18 turns, on a Type T50-12ferrite core.L6: 6 turns through a ferrite bead.
TelecomTelecom is the quadrennial communi-cations exposition organized by the In-ternational Telecommunication Union(ITU). It is the world's largest, mostauthoritative and comprehensive tele-communications event, attracting exhibi-tors and visitors from all over the world.In the 4 years since Telecom 83, greatstrides have been made by the telecom-munication industry. This could nothave been reflected better than by themain theme of Telecom 87: "The Com-munications age: networks and servicesfor a world of nations". The ITU, aspart of the United Nations, has a co-ordinating, advisory and regulatingfunction as regards worldwide telecom-munication. But "a world of nations" isindicative of incompatibility, or, quiteliterally, a world of difference, betweennations' standards and preferences forexpanding existing telecommunicationsnetworks. In spite of the modernmeansavailable for global communication,technology in each of the ITU's 162member countries is developing at itsown pace, often dictated by political andeconomical factors. The ITU organizesTelecom to enable national PTTs andtelecommunication companies from allover the world to see the latest technicalachievements. This, hopefully, leads to
on the ways in which thesecan be integrated into existing telecom-munication structures. Again, there isthe risk of incompatibility between exist-ing and new systems, and this is exactlywhat the ITU strives to eradicate or pre-vent with the aid of a comprehensive ex-position. In this respect, it is interestingto quote the Secretary General of theITU, R. E. Butler: "The successiveTelecom exhibitions owe their success tothe fact that the ITU was in a position tooffer, within a neutral framework im-mune to external influence, facilities formeeting and interchange which weresoon recognized as a valuable servicerendered to our member countries aswell as to the operating organizationsand the telecommunications industry"
Telecom 87 was held in Geneva, theheadquarters of the ITU, from 19 to 27October 1987. The venue was the Palaisdes Expositions (Palexpo), which iswithin walking distance of the Genevaairport. The total number of exhibitorswas close to 900, and some 50,000visitors were received representing200,000 entries. The total net exhibitionsurface was 53,500 m' inside, and 9,000m' outside Palexpo. These figures markthe growth and importance of the tele-communications industry when com-pared to the net surface of 10,000 m'used for the first Telecom exhibition in1971. Asociated events during Telecom87 were:
87: a preliminary reportIII 5 Forums, in which press represen-
tatives, experts and officials, andother Telecom 87 attendants from theITU member countries were given achance to discuss openly various themesrelated to telecommunication;
the 3rd Book and Audiovisual Fair ontelecommunication, electronics and
associated disciplines;
the 5th International Film Festivalculminating in the award of
the"Golden Antenna";
the 5th Youth in the Electronic Agecompetition.
The first day, 19 October, was certainlythe most interesting for the numerouspress representatives, since Telecom wasnot yet opened for the general public.Although it was announced that ac-credited press members would have aunique opportunity of arrangingmeetings and interviews with VIPs andITU officials, the day (and much of theevening) saw installation personnel andmany engineers working frantically toget their company's booth, display, orstand ready in time. All this business of-fered a unique chance to study brandnew equipment and connection tech-niques from close by before it was care-fully tucked away behind attractive look-ing panels with letters and lighting invarious colours. Painting, openingcrates, carpet laying as well as connect-ing terminals to mainframes and digitalexhanges was carried out as "last mi-nute" work. Outside the Palexpobuilding, on a specially reserved site, 30or so dish aerials of widely varying sizewere being brought into service to enablepermanent and "live" demonstations ofsatellite communication for the comingexhibition days. The signals to and fromthe transportable dish stations were car-ried to the various stands via cables, orshort-range microwave links via the roofof the Palexpo building.
Telecom is not an exposition where onehas to press through masses of visitors toget a glimpse of the material on display.The various commercial and technicalrepresentatives of exhibiting companieswere eager to demonstrate new equip-ment to any interested visitor, althoughsome of the questions asked were sodeeply involved with technical details asto require noting separately and for-warding to an expert colleague in the rel-evant department "at home". Press re-leases were not scarce either, making itvery difficult, if not impossible, to leavePalexpo without bags of docunientationand souvenirs for the occasion. Thepress room was hectic, and cluttered with
paper. A number of companies used thepress notice board to criticize com-petitors' products by means of hurriedlyissued information bulletins. Cocktails,lunches and important speeches werescheduled and again postponed formaximum impact on the press represen-tatives.
The main theme of Telecom 87 wasexcellently reflected by the Hall ofNations, in which individual countrieshad set up "national pavilions" accom-modating the stands of many smaller,and often highly specialized, companies.The Italian, French, NorthernAmerican, Scandinavian and WestGerman pavilions were remarkable forthe impressive number of companies ac-commodated. Many companies werepresent with their corporate stand, andin addition as part of a national pav-ilion. Examples were Siemens, Motorolaand Philips/AT&T.
Companies and institutions with relatedproducts and services were located closeto one another in the halls. Inmarsat's"Great Maritime & Land MobileShow", and the 1:4 scaled model ofAriane 4 were successful eye-catcherscalling visitors in the direction of anumber of important representatives inthe communications satellite field:EuroSatellite, ESA, Inmarsat, HughesAircraft, Intelsat, ArianeSpace, GeneralDynamics and EutelSat.
Telecom 87 focused heavily on integrateddigital networks (ISDN) and satellitecommunications. NTT (Nippon Tele-phone & Telegraph Company), Mat-sushita, NEC, GEC/Plessey andAT&T/Philips attracted many visitorswith live demonstrations of ISDN. In anISDN system, telephone calls, telex, fac-simile, slow -scan images, and LAN -likedigital services are all "packed together"for high-speed transmission via fibre op-tic links or geosynchronous communi-cation satellites. System X fromGEC/Plessey is generally expected togovern the new technical outlook of all -digital, and ISDN compatible, data ex-change systems. In fact, System X equip-ment has been in use for a number ofyears in all British Telecom trunk ex-changes, but the latest enhancements tothe system as regards the transmissionspeed achievable over satellite links hasaroused the interest of many nationalPTTs looking for ways to extend existingtelephone networks. ISDN and satellitecommunication are closely related, andthe relevant products and services ofmany leading telecommunicationcompanies will be discussed in nextmonth's issue of Elektor Electronics.
EE
January 1988
STEREO LIMITERA quality limiter for use in tape recorders, transmitters, public address systems, and discotheques.
A limiter is an electronic volume adjust-ment circuit in which AF signals areamplified up to a predefined level of theinput amplitude. When this level isreached, the gain of the amplifier is re-duced to ensure that a fixed, maximum,output level is not exceeded. In otherwords, the output amplitude remainsconstant irrespective of fluctuations ofthe input signal above the limitingthreshold. Limiting is, therefore, oftenreferred to as dynamic range compres-sion. Figure 1 shows the dynamicresponse-U. as a function of LA-ofthe proposed limiter.The design described here is based on apair of standard gain controlledamplifiers which ensure a dynamic rangecompression of about 46 dB. Thelimiting threshold is reached at an inputvoltage of about 50 mV: the outputvoltage is then about 670 mV.
Circuit descriptionWith reference to the circuit diagram ofthe stereo limiter in Fig. 2, opamp AIsums the signals applied to the L and Rinputs, and provides the gain controlsignal for the limiter chip Type NE572 inposition ICs. Although it is economicalto provide a gain control signal commonto both channels, the result is, of course,the likelihood of mutual and inap-propriate gain reduction on the stereooutputs. Fortunately, this effect does notraise problems for programme materialplayed at average to loud levels, and thedifferences in output volume on thechannels are certainly tolerable at lessthan 5 dB.Both channels in the Type NE572 dualprogrammable analogue compander(compressor -expander) from ValvoiMullard comprise a full -wave rectifier, a
-40
-70-A -40 -SO -A -30 o 40 .20
47164-,
111111MMIMIIIIIMINMIIMINIIIIIIM111111111111111111IM1111111111111111n1111 tRIPIRTM.TINRIIMIN
UMMIIMEll41111111111111WIll
..JEMIN11111111111ff
1111MM11111111111111111ii,iiIIIIM111111111111MIMEN
31111111111111=111111111MM11111111111111111MIIIIMMIE1111111111M1111101111111MINI i
1111111MMI1111111111111111111111111111111111111111111111111111
buffer and a linearized, temperaturecompensated gain cell. All these operateindependently from the correspondingsection in the other channel. The recti-fier translates the AF signal from Aiinto a direct control current for thebuffer, which in turn controls the outputcurrent provided by the associated gaincell, marked AG in the- circuit diagram.The attack and recovery constants of thegain controlled buffers are determinedwith the aid of external electrolyticcapacitors Cs -C6 (L) and C12 -C13 (R).The outputs of the current controlledgain cells AG are connected to the feed-back resistors of opamps As (L; Rs) andAG (R; R12). Hence, the output current
provided by the gain cells controls the at-tenuation introduced by AS and A6. Inthe present application, the operation ofthe gain cells is, therefore, comparable tothat of a current controlled electronicpotentiometer. Output opamps A2 (L)and A_s (R) are dimensioned for an am-plification of about 4.7. The oscillo-grams of Fie. 3 show the dynamicresponse of the limiter.It is evident that the technical character-istics of the proposed limiter are a com-promise between what is useful on theone hand, and practical for most appli-cations on the other. This means that theinput threshold, the output level, thedynamic range and the tracking(gain dis-
2
L0,0
MEI
RIG
a
M R4CI
= ul252
0
9
-EC N I
EMI
Al
10540V
-6V2 -1V5 -6V2011, 0v
241144148
It
ii2142
*Ste teat
C3
252
212
_G
IC 3
9
C6111
221.
1_07vNE572
------ C
31
.1G
C's
isic D=icIC 2
0 ci C21
0 0 220n 220n
0
C C21
T "r" oN
10440V
R14
At-A4 = IC 1= TL074; 0P470AS, A6 = IC 2 = LF353; TL072
37163-2
Fig. 1. Dynamic response of the stereolimiter. Fig. 2. Circuit diagram of the stereo limiter.
58 EE
January 1988
tribution) of the channels are dimen-sioned such that the circuit is suitable fora wide variety of applications. In somecases, the technical characteristics mayneed altering, however.Resistor Rs (R12) sets the maximum am-plification for an optimum signal tonoise ratio in the absence of an inputsignal. The maximum usable resistanceis about 680K. The gain cells operate ata bias potential of about -5 V, whilethe + input of the associated oper-ational amplifier (pin 5; 3) is connectedto ground. This means that the maxi-mum drive for As (A6) is about 1.4 Vniis.Both gain controlled opamps functionas an alternating voltage amplifier, anddo not, therefore, need a coupling ca-pacitor to the associated output driver.The attack constant is determined withCu; Cs (R; L), the release constant withCu; C6 (R; L).The main point in the dimensioning ofthe control circuit concerns the selectionof the control voltage for the gain cells.In practice, it was found that the :,drivemargin can not be set much higher than- 25 dB, corresponding to the alreadystated 50 mV (0 d132--' 1 m\V in 600 Q).The input voltage should, therefore, notexceed 130 mVinis to avoid overdrivingthe limiter, since this would then operatelinearly again, amplifying the inputsignal. To avoid any risk of this happen-
Parts list
Resistors t=5%):
lit;R3=39KR2=4K7R4;R1 1 = 33K
Rs;R12=330KRa;1113=4K7R7;1114=22K
Re;Rts;RicRii=100KR9 = 2K7Rio=3K3Pi = 1K0 preset H
Capacitors:
Ci;C3;C4;C9;Cio;C1i =2p2; 25 VC2;Ce;C s;Cie= 10p; 16 VC5;C12= lo; 25 VCs;C 13 = 22p; 25 VC7;C14;C2d;C24=10p; 40 V; bipolar'C17 ...C22 incl.= 220nC25;C26 = 47p
e.g. Maplin order no. F806G, or Cirkit stockno. 04-10613
Semiconductors:
Di;D2= 1N4148ICI =T1074 or OP -470IC2=LF353 or TL072IC3=NE572. (ValvoiPhilips!Mullardi
Available from Universal SemiconductorDevices Limited.
Miscellaneous:
PCB Type 87168 tsee Readers Services page)
,,111111,P1111,1111
b
Fig. 3. Automatic level control obtained with t to limiter. Small signal response Iht and largesignal response tat. Upper channel: output: timer channel: input.
ing, it is recommended to fitpresets v.itha value of, say, 100 K2 at both limiter in-puts.The tracking (gain balance) of the chan-nels is optimized with the aid of Pi. Thecorrect adjustment is reached afterchecking, noting and comparing thedynamic response curves of the L and Rchannel with the aid of a calibrated sine-wave generator, an oscilloscope and atrue-rms meter.In the absence of these instruments, ac-ceptable results are obtained when Pt isset to the centre of its travel.
Construction and useThe ready-made printed circuit boardfor the stereo limiter is shown in Fig. 4.
Construction follows the usual patternof fitting the components as per theparts list and the white overlay on thePCB. Fit the ICs in sockets, and do notforget the 2 short wire links between C20
and C21. The capacitors in the cornersof the PCB arc bipolar (non -polarized)types.
Attention: pin 5 of IC2 is erroneouslyleft unconnected on the PCB. This isreadily amended by running a shortlength of light insulated wire from pin 5to the ground connection of C20.
The supply voltages for the limiter canbe obtained by stepping down ±10, ±12or -±15 V rails available in the equip-ment to incorporate the stereo limiter.
Fig. 4. Track layout and component mounting plan for the printed circuit board. PLEASEREFER TO THE TEXT FOR THE CONNECTION OF IC2, PIN 5.
EE
January 1988Zener diodes and discrete regulators areequally suitable for providing theregulated ± 7 V supply voltage.The limiter is best connected perma-nently between the outputs of a linedriver or mixer, and the inputs of thepower amplifier. After establishing thedrive margin of the system, the outputand input level presets (if used) aresealed to avoid overdriving the poweramplifier and the limiter, respectively.Gb
59
SCIENCE MOBILISES TO BEATMURDER I[N THE AL -1
by Bill Pressdee, BSc, CEng, ivilEE
The problems confronting airportsecurity are basically the same as thoseinvolved in the custody of any major in-dustrial complex of national import-ance. These include theft, ranging frompetty larcency to bullion robbery, illicitincursion, ranging from unauthorizedentry to military takeover, and specifi-cally terrorist attack, either in the air-port or in the air.Combatting these problems calls for ad-equate surveillance by man or machineto discover illegal acts, and the appro-priate detection of illicit devices ormaterials in sufficient time to applyremedial action.Incidents at airports-such as bullionrobbery, the smuggling of drugs, or thediscovery of explosives in hand lug-gage-are generally reported in iso-lation. However, to be effective, an air-port system must be comprehensive tocover every aspect of security. For eachairport, the security system must firsttake account of the particular site prob-lems.There are many security devices availablefor use around the airfield, and theseshould be deployed to monitor variouszones of increasing risk, starting at theperimeter fence: microphonic cable todetect break in; closed circuit television(CCTV) cameras to scan various sectorsof the airfield (possibly connected to
motion detectors); and infrared, micro-wave and underground pressure detec-tors to discover intruders and vehicles inunauthorized areas.
Searching the publicChubb Alarms is a major British secur-ity company marketing a comprehensiverange of such devices, and has con-siderable expertise to advise how an areacan best be protected.Of more critical concern at present,however, are the airport areas to whichthe public have access-in particular theinterfaces between the public areas andthose restricted to passengers and air-port staff. Through these pass the
Luggage inspected for explosives using theA.I. Security Type 97.
passengers, their baggage and their handluggage, each piece of which may beconcealing weapons or explosives, or themeans for making or assembling them.It is at these interfaces that, as thecriminal and would-be terrorist becomemore ingenious, the detectors deployedagainst them need to become more effec-tive.CCTV is an important general means ofmonitoring the concourse of the airportand noting irregularities. The recent de-velopment of charge coupled device(CCD) cameras using solid state imagesensors is a major step towards improvedCCTV surveillance. The units are ex-tremely small, allowing covert oper-ation; they have a long life, are robust,need negligible maintenance and work atlow voltage with power consumption ofjust a few watts.
Finding metalCoupled via a fibre optic taper to amicrochannel plate image intensifier,they are capable of operation over allranges of ambient illumination frombright sunlight to starlight. The EnglishElectric Valve Company Ltd has recentlyannounced a comprehensive range ofCCD cameras and sensors manufacturedin its new factory at Chelmsford, eastern
60 EE
January 1988England, the most advanced CCD fa-cility in Europe.Firearms and most other weapons willincorporate a substantial amount ofmetal, which may be detected by X-raymachines or metal detectors. Passengers,on entering the airport's departure area,and possibly also before embarking,may be required to pass through an arch-way incorporating a metal detector (andperhaps including an explosives detectoras well, as in the A.I. Security EntryScan Type 85).The threshold sensitivity of the detectorwill be set to discriminate between, say,a small pistol and loose coins in thepassengers' pockets: warnings of signifi-cant metal detection may then promptfurther investigations by means of aphysical body search or hand held metaldetector such as the GN,I2 made byGraseby Dynamics.Baggage and hand luggage is normallyinspected via an X-ray machine, tendedby an operator trained to identify sus-picious opaque profiles. Recent productsfrom Astrophysics Research, which hassupplied over 2000 such machines world-wide, include a combined check -in deskand X-ray screening system and mobilesystems for spot checks.
Explosives threatDetection of illegal objects depends atpresent on the operator's alertness andexperience, but the advent of micro-processors operating at several millioninstructions per second heralds the de-velopment of expert detection systems inwhich the X-ray responses will be com-pared automatically with a multitude ofthose from known weapon types.Explosives represent the most deadly ofthe armaments available to the terroristand also, even when made into impro-vised bombs, the most difficult to detect.The minimal amount of metal in thedetonator or triggering device is unlikelyto reach the alarm thresholds for arch-
way or hand held metal detectors.Accordingly, over the last two decadesseveral types of explosive detector havebeen developed. Explosive compounds,their additives and decomposition prod-ucts emit minute quantities of a charac-teristic vapour, which is possible tosample and identify-although withsome modern military, explosives this isfar from easy.The simplest sniffer devices availablerely on direct ionization of the vapourfrom the explosives in air. These includetypically the Graseby Dynamics PD4Cand the A.I. Security Model 35, whichare light, compact and easy to use.Although they perform a useful func-tion, their sensitivity is limited, theirdiscrimination medial, and they areunlikely to respond to certain militaryexplosives.
Finer samplingA more sensitive and selective range ofinstruments is available, based on gaschromatography. It includes the A.I.Security Model 97. These devices rely ona constant and very pure supply of inertgas, and the means for introduction ofthe atmospheric sample into the gasstream. The penalties for increasedsophistication, however, appear in termsof increased size, weight, warm-up time,response time, and cost.The only other detectors in being are thevery complex and accurate instrumentsmostly confined by their size and lack ofportability to laboratories, except for arecent product of Graseby Dynamics,the Ion Mobility Spectroscope (ISIS),Model PD5 which shows considerablepromise.The EMS operates by first drawing an airsample through a probe and over a mem-brane, which excludes dust and moisture,but permits the diffusion of the vapourmolecules. The molecules are then ion-ized by a weak Nickel -63 beta emitterand subjected to a 1000 V DC field, con-
trolled by a gating grid which allows thepassage of the ions in discrete samples.The drifting ions become rangedspatially in order of their mobilities,and, on reaching the collector electrode,present a current waveform character-istic of the ions in the sample. Theinternal air stream is circulated by apump and dried. Then certain dopantchemicals are added in minute quantitiesto enhance the sensitivity.The waveform received by the collector isdigitized and fed to a microprocessor, inwhich its characteristics are assessedagainst patterns for various explosives,while vapours derived from othersubstances are disregarded. The PD5 hasa hand-held unit with digital readoutconnected by an umbilical to a briefcase,making it ideally portable.In many aspects the means for ensuringgood airport security are becoming bet-ter and more sophisticated. It remainsonly for airport authorities to developsecurity systems that use these means ef-fectively.
A.I. Security (Division of Analytical In-struments Ltd), Pampisford, CambridgeCB2 4EF.
Graseby Dynamics Ltd, 459 ParkAvenue, Bushey, 'Watford WD2 2BW.
EEV Solid State Devices, (English Elec-tric Valve Company Ltd), WaterhouseLane, Chelmsford, Essex CM 1 2QU.
Chubb Alarms Ltd, 42-50 HershamRoad, Walton -on -Thames, SurreyKTI2 1RY.
Astrophysics Research Ltd, 100 ValeRoad, Windsor, Berkshire SL4 SJP.
3
EE
January 198861
NEW PRODUCTS e NEW PRODUCTS NEW
Designed to charge both sealedl NiCd,and lead -acid cells and batteries, the newKOMBI from Bartec Compit also oper-ates as a switchable stabilized powersupply. The NiCd charger can charge upto 10 cells of any size at a maximum out-put current of 500 mA. The lead -acidcharger is a 3 -level constant voltagesource for 2.3, 6.9, or 13.8 V. The PSUhas the same output voltages, and sup-plies up to 500 mA.Bartec Compit UK Station Road Facit Rochdale OL12 8LJ. Tele-phone: (0706 85) 2224. Telex: 635511BARTEC G.
Single -chip colour video DACAn advanced video graphics digital -to -analogue converter, Type IM2110, isclaimed by Intersil as the first to fully in-tegrate all the functions needed for a dis-play system interface.
The 1M2110 CMOS AVLSI chip includesthree 4 -bit DACs, a 256 x 12 dual -portedcolour palette, a general purpose micro-processor interface, a temperature -compensated voltage reference and allthe associated sync and control circuits.Although designed for use in analogueRGB systems, the IM2110 has functionalcapabilities that make it suitable for a
whole range of other applications in-cluding Heads Up Displays, Low -endCAD stations, and display systems forradar and sonar.RCA International Limited BeechHouse 373-399 London RoadCAMBERLEY GUIS 3HR. Telephone:(0276) 685911.
DSO features comprehensivebuilt-in signal analysisfacilitiesNew from ITT Instruments is theOX750B, a compact digital storage os-cilloscope which offers a digital per-formance based on two 8 -bit 2 MHzA/D converters and an analogue per-formance of a 20 MHz dual -trace os-cilloscope.Ideally suited to industrial applicationsor field service, the OX750B is housed ina rugged case weighing only 10kg andmeasuring just 450 x 310 x 160 mm. Theinstrument is suitable for users with littleoscilloscope experience - having anergonomically designed front panel andcontrols with analogue and digital sec-tions as Well as signal acquisition andanalysis functions clearly segregated.
A major feature of the OX750B is itscomprehensive range of built-in signalanalysis facilities. The memory can holdup to 2048 samples per channel, 2000 ofwhich may be displayed on the screenwhile the remaining 48 are used for thereference position. To facilitate analysis,the OX750B incorporates a horizontaldigital expansion of up to x 32 (in sixsteps) and an interactive cursor whichallows the user to select that part of thestored signal required for analysis.Luminous intensity of the trace is con-stant and remains independent of the ex-pansion factor. Also provided are ver-tical digital trace shift and digital expan-sion capabilities.The whole memory contents, or the sec-tion of waveform selected using thesignal analysis facilities can be output to
an X -Y recorder. An optional auto -plotmode transfers the data at each comple-tion of the acquisition cycle.A battery -backed memory facility is in-corporated in the OX750B for storingthe captured signal, as well as the modeand function settings, in the event of apower failure. This facility can also beused to acquire waveforms in the fieldfor subsequent analysis and plotting -outback at base. Alternatively a referencewaveform can be transported in memoryfor several years without refreshing.ITT Instruments 346 EdinburghAvenue SLOUGH SLI 4TU. Tele-phone: (0753) 824131. Telex: 849808ITTCOM G
Digital storage unitThandar Electronics are pleased to an-nounce the introduction of a truly port-able low power digital storage unit.The TD201 offers sensitivity down to5 mV and the real time bandwidth isgreater than 200 kHz. Operating modesare real time, refresh, roll and single shotwith selectable pre -trigger of 0%, 50%or 100% internal and external triggering,pen plot and hold facilities are also pro-vided.The maximum sampling rate of 200 kHzpermits fast transients to be capturedwhilst the minimum sampling rateenables events lasting more than 1 hour
to be acquired. Data is stored in a 1 Kmemory and can be retained for up to 4years when batteries are fitted.The TD201 will operate from disposableor rechargeable cells or from an optionalAC adaptor which also serves as acharge when rechareable cells are used.The TD201 is priced at £195.00 + V.A.T.Thandar Electronics Limited LondonRoad St. Ives HUNTINGDONPE17 4HJ. Telephone: (0480) 64646.Telex: 32250 Test G
62 EE
January 1988
correctly configured for the majority ofSMT packages currently available.Ten different types of component can betested and the board will carry up to 30items. The unit has been manufacturedusing SMA PCB production techniques,including dry film masking between leadcentres of 0.813 mm. Price of the PCB27-0127 is £4.98 (ex VAT & delivery) andthe component kit costs. £29.28.OK Industries UK Ltd. Barton FarmIndustrial Estate Chickenhall Lane EASTLEIGH SO5 5RR. Telephone:(0703) 619841.
In -field RF powermeasurementNew power sensor heads introduced byCirkit provide an extremely cost-effec-tive and rugged way of measuring RFpowers in the range 0.5 Watt to 75 Wattsand DC to 2 GHz. The only additionalequipment required is a standard200 mV digital voltmeter (DVM) andleads.The new products have been designedspecifically for the service engineer orradio amateur who needs to make quan-titative measurements of multi-fre-
NEW PRODUCTS NEW PRODUCTS NEW: ii
FA. . r II W-411IV111111111111101111111111-111%11111111
am Ur MIIIIMIJIl11111111101111111'NNWWIIIII MI M1111111111NEWERWINNER11 111111The new, increased frame frequency of100 Hz puts an end to flickering pic-tures: The upper picture (50 Hz) with anexposure of 1/60 second clearly showsthe shadow of the blanking interval inwhich the line -by-line TV picture syn-thesis is restarted each time. The missingbar on the lower picture is the (in)visiblesign of this progress (also for videotext)achieved with nine DRAMs (256 kbits)and the digital. VLSI logic circuits fromSiemens. The TV concept is suitable forPAL, SECAM and NTSC.Siemens AG Zentralstelle fiir Infor-mation Postfach 103 D-8000MUNCHEN 1 Federal Republic ofGermany.
SMT trials kitOK's latest SMT fibre-glas trials boardhas been designed in conjunction withthe manufacturing expertise of BritishAerospace and is available with a com-ponent kit which includes large gull wingand PLCC in dummy form to save costs.The board was originally designed toresearch and develop OK's own SMTproduction and rework systems and is
quency and power transmitter instal-lations where the use of expensivelaboratory equipment would not befeasible. The new power heads simplyconvert a conventional DVM into abroadband absorption wattmeter.In essence the device is a ruggedbolometer. Power is fed to the unit usinga co -axial connector where it is dissi-pated in a precision 50 Ohm termina-tion.Cirkit Holdings PLC Park Lane BROXBOURNE E N10 7NQ. Tele-phone: (0992) 444111. Telex: 22478.
Need a BNC connector?A comprehensive range of BNC connec-tors is available from Watts for appli-cations up to 4 GHz.The Lynics Corporation plugs, recep-tacles, jacks, and adaptors can be sup-plied with an impedance of 50 or75 ohms. Over 37 different types of con-nector feature in the range with vari-ations such as crimp/solder or screw -lock wiring, straight or right-angledbody, and priel or PCB -mounting.Adaptors offered include in -line,through -panel, and Tee. Body and con-tact platings can be chosen to suit re-quirements.
Using standard coaxial cables areas ofemployment include instrumentationand test equipment, communicationsapparatus, computers/peripherals, andvideo systems.Watts International ComponentsLimited Suite 6 Wyvern House BOGNOR REGIS West Sussex. Tele-phone: (0243) 868322.
EE
January 198863
NOISE BLANKERA noise blanker is indispensable for im-proving the reception of very weaksignals on the SW bands. In most com-munication receivers, the selectivity ofintermediate frequency (IF) filters causeinterfering pulses to be widened, blot-ting out the wanted signal. It is useful,therefore, to suppress interference beforethis can wreak havoc in the IF sectionsof the receiver.The 455 kHz IF signal is first buffered inT2, and then processed separately in twocircuits.The lower section of the circuit is aTCA440 based receiver for the interfer-ing pulses. The TCA440 is in itself a vir-tually complete receiver, since it com-prises an RF amplifier, a mixer, and anIF amplifier. All stages in the latter areused since pin 4 is grounded here. Thepulse receiver has its own AGC (auto-
matic gain control) to ensure effectivesuppression of relatively weak inter-ference also. Preset Pi and poten-tiometer P2 enable precise adjustmentof the noise blanker for various levels ofinterference. The circuit can be con-trolled digitally via R23; a logic highlevel renders the noise blanker ineffec-tive. The interfering pOlses are madelogic compatible with the aid of opampIC2. LED D3 lights when noise isdetected.In the upper section of the circuit, the IFsignal is first delayed in FLI to compen-sate for the processing time in the pulsereceiver. ES1 is opened when a suf-ficienly strong interfering pulse is recoe-nized, so that the IF sienal is no longerapplied to output buffer T2. Also, thegate of this FET is then grounded for RFsignals via ES3-C4, while ES2 is closed
to maintain correct termination of FL!.Properly constructed, this circuitachieves noise suppression of the orderof 85 dB. Alterations to suit operation atan IF other than 455 kHz involve Liand FLI, although due account shouldbe taken of the parasitic capacitance ofthe electronic switches at relatively highfrequencies. (B)
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64 EE
January 1988
LIGHT POWEREDTHERMOMETER
An accurate, automatically operating electronic thermometer that indicates temperature on a digitalreadout without the need for batteries or a mains supply.
The thermometer described here is pow-ered by an amorphous solar cell. In con-trast to other types of solar cell, this usesa non -crystalline silicon layer. Amorph-ous solar cells are produced by con-trolled deposition of silicon on a glasssurface, which forms the top of the cell.The production method is relativelysimple and cost-effective, but has thedisadvantage of yielding cells with arelatively low efficiency. The basic struc-ture of an amorphous solar cell is shownin the diagram of Fig. 1. The eleTent iscomposed of 3 series connected cellssecured on a glass plate. Each photonthat enters a cell causes the release of anelectron from a silicon atom. The releasegenerates electric energy, which can beused for powering the thermometer cir-cuit-provided, of course, there is suf-ficient incident light on the solar cell.
Circuit descriptionWith reference to the circuit diagram ofFig. 2, the temperature sensor is formedby IC_. This is the well-known precisioncentigrade temperature sensor TypeLNI35CZ from National Semiconductor.Housed in a plastic TO92 enclosure, thisdevice gives a linear output voltage of
1glasssubstrate
transparantelectrode
amorphoussilicon
electrode
encapsulation
Fig. 1. Basic structure of an amorphous solar cell.
+ 10.0 mV/°C. It does not require anyexternal calibration or trimming, and yetprovides an accuracy of ± 0.25 °C atroom temperature, and ± 0.75 °C overthe full -40 to +110 °C temperaturerange. The IC is internally calibratedsuch that 0 °C corresponds to an outputvoltage of 0 V. The remaining functionsof the thermometer circuit are a volt-meter, a read-out, and a decimal pointshifter. All these are combined in a singleintegrated circuit Type ICL7136 (ICI),and a 31/2 digit liquid crystal display(LCD). The oscillator internal to ICI isoperated at the lowest possible clockspeed to ensure minimum power con-
sumption of the circuit whilst avoidingdisplay flicker. The thermometer read-out is calibrated with the aid of Pi.Components Di and R II enable thesensor to provide a negative outputpotential when the temperature fallsbelow 0 °C. LEDs Di and 132 do notfunction as'., light sources, but asreasonably stable 1.6 V references thatrequire a forward current of only a fewmicro -amps. Standard zener diodes givebetter regulation, but are not suitablehere in view of the relatively high for-ward current required for the stabiliz-ation effect.The circuit around IC3 is a voltage
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EE
January 198865
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Fig. 3. Track layout and component mountingbe fitted in a transparent Heddic enclosure.
monitor that switches the thermometeroff via T2 when the potential suppliedby the solar cell falls below 7.0 V. Thisprotective measure effectively preventserroneous read-outs: for accurate oper-ation sensor IC2 requires a minimumsupply voltage of 5.5 V, while the refer-ence source internal to ICI should befed with 7.0 V or more. Schmitt -triggerIC3 in the voltage monitor switches T2on again at an input voltage of 8 V, i.e.,the circuit is dimensioned for a hysteresisof 1 V. The switch -on threshold is set at7.0 V with the aid of preset Pa. The cur-rent consumption of the thermometer inthe de -activated and activated state isabout 10 and 200 pA, respectively.When the circuit is in the de -activatedstate, and there is moderate incidentlight, the solar cell can only supplyabout 100 pA, so that C6 is charged to8 V. The thermometer is switched on,and draws more current than can be sup-plied by the solar cell. This means thatC6 is discharged: the supply voltagedrops below 7.0 V, and the thermometeris switched off again after a few seconds.This automatic on -off arrangementenables taking temperature readings evenin less favourable weather conditions.The hysteresis of 1C3 can be increasedby reducing the value of R7, and re-adjusting Pa. It is possible to use asmaller capacitor for C6, so that thethermometer is switched on rapidlywhen the light intensity increases. Fi-nally, the function of D7 is to limit the
plan. The completed printed circuit hoard can
supply voltage to 12 V when there is in-tense sunlight on the solar cell.
Construction and setting upThe printed circuit board for the lightpowered thermometer is shown in Fig. 3.The completion of the board should notpresent difficulty, but care should betaken handling and mounting the fragileLC display. Do not overlook the 2 wirelinks on the board.Do not yet fit IC2, and apply +1.000 Vto the points intended for the V.it andGND terminals of the sensor. Adjust Ptfor a display reading of 100 °C. Removethe voltage source connections, and fitIC2. The completed PCB and the solarcell are made to fit in a transparent Hed-dic enclosure. The space is quite tight,and the drop of sealing resin on the LCDmay have to be flattened by careful fil-ing. One side of the enclosure of ICI istreated likewise. Use wire -wrap terminalstrips so that the face of the LCD ispressed against the inside of the lid. Drilla few holes in the enclosure to preventheat building up inside, The response ofthe sensor to rapid temperature changescan be improved somewhat by glueing asmall piece of thin metal sheet onto theflat side of the 1092 enclosure.Some spare room is available in theenclosure for an optional 9 V (PP3) ba.tery. A switch can be fitted to select be-tween the battery or the soL..:cil as the Fig. 4. Promo. pes
power supply for the thermometer. Tii- mometer.
Parts list
Resistors (±5%):
Fli;Rz;Ra=1M0Re = 220KR5 = 270KRe=1M8R7= 10MRs = 1M5Re =470KRto=680KRI 1=33KPI =200K or 220K multiturn presetP2 = 'IMO preset H
Capacitors:
C i;C2;Ca =100nC4 =82nCs=47pC6 = 470p; 16 VserniCanciuctors:
DI:D2=LED: 3 mm; redDa=AA119Da= zenerdiade 12 V; 0.4 WTi=BS170÷T2 =8C5478ICt =ICL7136CPL"IC2=LM35CZ (Maplin order no. UF51F)IC3=TIC271-
available from Cricklewood ElectronicsLimited.
"available from Universal SemiconductorDevices Limited.
Miscellaneous:
LCD= the following types may be used:LTD221-001 (Multard/Videlec; for distributorsrefer to InfoCard 507 in the April 1987 issueof EEl;
43D5R03 (Data ModulIXD; 2D Electronics Wellington House 2 Kentwood HillReading. Tel. (0734) 420440);
3901 or 3902 (Hamlin; Hamlin Electronic EuropeLimited Park Road Diss Norfolk (P223AY).
Solar Cell= Lk 8- 12 V, size: 48 x 96 mm. e.g.Solems Type J0887J801
Enclosure Heddic Type 222-G'.PCB Type 87188 (refer to the Readers Services
pane).
PP3 battery (optional). Heiland Electronic Design & DevelopmentHermann Loens Strasse 11 D-4410Warendorf 3 West Germany. Telephone:+49 (2582) 7550.
Availability in the UK: Chartland ElectronicsLimited Chartland House Twinoaks Cobham Surrey Kill 2041. Telephone:(037 284) 2553.
For further details on distribution: Baorne.sNewman International Limit:: o Off,ca Sate
The Square, Forest Rc.. East Sussex
RH18 5ES. ielepho- 04 282) 270& T
95637.
of the light pLIv.erol
66 EE
Jinuar 1988
WIDEBAND AERIAL BOOSTERAND SPLITTER
A single transistor amplifier and a matched RF signal distributor ensure that the signal provided by theaerial or cable network can be fed to several radio or TV sets without loss of quality.
Many people buy a second TV set foruse in a location other than the livingroom. After experiencing the disap-pointing reception obtained by the useof the built-in or set -top aerial, it is oftendecided to connect the new TV to thesame antenna input as the main set.However, the assumption that the signalstrength is high enough to feed 2 TV setsis immediately proved false by ghost ef-fects and considerably increased noiseon...both sets!
Aerials and coaxA good quality directional aerial is thebest RF amplifier. It is often frequencyselective, consumes no power, introducesno noise, and gives considerable amplifi-cation. A typical multi -element Yagiaerial for UHF TV reception has a halfpower opening angle of about 15*, anda power gain of 12 to 16 dBi. Since theaerial is usually mounted in the highestpossible location on the roof, its outputsignal needs to be fed down to the re-ceiver via a cable that ensures minimumsignal loss, freedom of induced inter-ference, and correct matching at bothends. The loss introduced by a cable ofany type (coax, twin -feed) is directlyrelated to its length, and the frequencyof the signal it carries. For coax, the lossis generally lower with increasing cablediameter. At 100 MHz, for instance,Type RG213/U cable has an attenuationof about 5.7 dB per 100 m, whileRG58/U is specified at 14 dB. RG2I3/U(A, = 50 Q) and RG58/U (Zo = 53.5 Q)have an outside diameter of 10.3 and5 mm, respectively. The commonlyused, general purpose, white coax foruse in the home is certainly not betterthan RG58/U.Although it is assumed here that con-structors are familiar with the generalrule that an RF amplifier should be fit-ted as close as possible to the aerial, thefollowing example may prove helpful toillustrate the practical consequences ifthis is not the case.Any electronic amplifier produces noise.Assuming that the circuit in questionreceives an input signal of 10 pV, andamplifies this, say, 10 times while addingI pV noise, it is readily seen that its out-put signal is composed of 100 pV
Fig. 1. Circuit diagram of the widebandaerial booster.
"signal" and I µV noise, i.e., the signalto noise (S/N) ratio is 100:1. When thedownlead coax has an attenuation of 4,the TV set receives 25 pV "signal" and0.25 pV noise. Thus, the S/N ratio is notaffected by the coax cable.When the aerial amplifier is fitted at thelow end of the downlead coax, i.e., closeto the TV set, it receives a signal of2.5 yV, which it amplifies to 25 pV. Thenoise level at the output is, again, 1µV,however, so that the resultant S/N ratiois only 25:1. The signal amplitude is still25 ,uV, but the noise level is quadrupledfrom 0.25 yV to I pV. The conclusion isobvious: the amplifier should be fittedas close as possible to the aerial, andthe connection between them should bemade in high quality (low loss) cable. Ingeneral, the amplification of the aerialbooster ensures that the available S/Nratio is not ,.affected by the downleadcable, even if, this has considerable at-tenuation.
Wideband aerial boosterThe amplifier described here is a wide-band design with a frequency range ofabout 80-800 MHz. Its advantages aremainly the ease of construction, and theabsence of tuned circuits. Its inherentdisadvantages, are, however, equally im-portant to note. The absence of anyform of selective filters in the circuit maygive rise to cross -modulation andblocking in the vicinity of powerfultransmitters (mobile radios, TVtransmitters, cellular radio repeaters,etc.).With reference to the circuit diagram ofFig. 1, the amplifier is based on lownoise RF transistor Type BFG65 fromMullard. Components Pi-Ri-L3-Co arefitted close to a mains adaptor that pro-vides a regulated output of 12 V. Theamplifier is fed via the core of thedownlead coax cable. Choke L3 preventsthe RF signals being short-circuited inthe supply, while C6 keeps the ampli-fier's supply voltage away from the TVinput. The RF signal provided by Ti is,therefore, superimposed on the supplyvoltage.Zenerdiode Di keeps the base of Ti at4.7 V below the collector potential. In-ductors Li and L2 prevent RF feedback
EE
January 198867
Fig. 2. The printed circuit board for the amplifier and its downlead power supply.
3
Fig. 3. The completed amplifier and supply boards connected to the coax cables.
between the collector and the base whilstpassing current through Di. The combi-nation of electrolytic and SMDcapacitors (Cs -Ca and C4 -C3) ensuresoptimum decoupling for the entire fre-quency range of the amplifier.
The aerial booster plus supply section isconstructed on the PC board shown inFig. 2. All parts are fitted at the copperside. The PCB is cut to separate theamplifier and the supply section. Drill a5 mm hole to receive Ti, whose leadsare cut to size, and soldered flat onto therelevant copper areas. Ascertain the pin-nine before fitting the BFG65! SMDcapacitors CI, C2 and Ca are carefully
glued into position before soldering. In-ductors Lt and L2 are wound as 6 turnsof 00.2 mm (36SWG) enamelled copperwire through miniature (3 mm) ferritebeads. The enamel coating is carefullyscratched off the connecting wires, theseare tinned, pushed through the respec-tive holes, soldered at the copper side,and cut off at the other side of theboard. The fitting of the zenerdiode andthe 2 electrolytic capacitors should notpresent difficulties. Mount a small tin orbrass screen across the transistor asshown on the component overlay. Figure3 shows the completed aerial 'boosterplus supply. Note that the coax cablesare clamped onto the boards to ensure
Parts list
Resistors (±5%):
R1= 270RP1 =2K5 H
Capacitors:
Ci;C2;Ca = 100; SMDC4=24,2; 16 VCs=47p;16 VCs=1n0; ceramic
Semiconductors:
Di = zenerdiode 4V7; 400 mWTi=BFG65
Inductors:
1_1;1_2;1.3= see text.
Miscellaneous:
PCB Type 87700X (not available through theReaders Services).
Mains adaptor, 12 VDC; 100 mA.
effective grounding, and the shortestpossible connection of the centre core.The amplifier is fitted in a waterproofABS enclosure for fixing onto the aerialmast. Drill 2 or 3 small holes in theunderside of the enclosure to preventwater gathering inside. The supply sec-tion is fitted iti,a small enclosure, locatedon the attic, 'or behind the TV set,together with the mains adaptor.Turn the wiper of Pi for maximum re-sistance. Measure the current drain ofthe completed amplifier by connectingan ammeter between the adaptor outputand the + 12 V input on the supplyboard. Pi is carefully advanced until aweak station is sufficently amplified,without running into cross -modulationcaused by stronger signals. Do not ex-ceed 25 mA on penalty of damaging T.When the amplifier is used fordistributing sienals on the cable networkas discussed above, it is recommended toreplace Ti by a Type BFG96, operatedat a collector current of 75 mA (this mayrequire adapting RI).
Signal dividerThe previously described amplifier hassufficient gain to enable dividing its out-put signal between a number of TV setsin the home. All the signal dividers to bedescribed should obtain their inputsignal from C6, i.e., they must not befitted between the amplifier output andthe supply.The signal dividers are assumed to beterminated in 75 Q. Figure 4 shows themost elementary set-up of a coax signaldivider. Although the input signal is cor-
68 EE
January 1988
Fig. 4. This signal divider is too simple togive optimum results.
rectly terminated in 75 Q, both TV setsat the outputs see a source impedance of
75 + (75//75) =112.5 Q.
A better circuit is shown in Fig. 5a. Inthis, there are three 25 Q resistors and 3termination resistors for the input andthe 2 outputs. Each .signal path has a25 Q resistor and a parallel combinationwith an equivalent resistance of
Fig. 5. Signal dividers that maintain the correct termination and source impedance in 75 Qcable networks.
(25+75)/2=50 Q
so that the characteristic impedance is50 + 25 = 75 Q. In the circuit of Fig. 5b,the signal amplitude on each of the 3outputs is one third of that at the input.For an n -way divider, the value of R iscalculated from
R -n -1n +1
x 75[Q].
The resistor values obtained from thisequation can be approximated with thenearest E12 or E96 value; for the 3 -wayand 4 -way dividers of Figs. 5b and 5c,the respective values of 39 Q and 47 Qcan be used with impunity.It is possible to further subdivide thesignal with the aid of the circuit shownin Fig. 6. This forms an alternative tothe circuit in Fig. 5c, and enableseconomizing on coax cable, since thedistribution point need no be central toall 4 connections. It is important to notethat all outputs on the dividers describedhere require termination in 75 Q, eitherby a TV or radio set, or, if this is notconnected, by a 75 Q resistor. Finally,Fig. 7 shows a practical version of a 2 -way divider fitted in a metal enclosure toprevent stray radiation. B;D
7
Fig. 6. An alternative 4 -way signal divider.Fig. 7. Suggested construction of a 2 -waysignal divider in a metal enclosure.
69
FRONT-END FOR FM RECEIVER
Among the most important technicalcharacteristics of a VHF preamplifierare the noise figure, and the large signalhandling capability. Although these arein principle conflicting requirements, acompromise can be found in the use ofhigh -quality RF components. The re-ceiver's ability to withstand high inputlevels can be enhanced by providing suf-ficient selectivity ahead of the active el-ement(s). This is especially importantfor the mixer, since it generates most in-termodulation products.In this FM tunerhead, the aerial signal isfirst passed through a slightly over -critically coupled band filter, amplifiedwith the aid of low noise UHF transistorTi, and again filtered. The overall gainbetween the aerial input and the mixerinput is about 12 dB at 87 MHz, and17 dB at 108 MHz. The difference iscaused by the adopted method of filtercoupling. A wideband Schottky DBM(double balanced mixer) is used for themixer in this design. The Type SBL-1(LO = + 7 dBm) is probably the best
available of the 3 DBMs stated. Tuneablelocal oscillator T2 produces very littlephase noise, and DG MOSFET T3 pro-vides a LO power of.50 to 100 mW at adrain current of about 25 mA. FET T4enables driving a prescaler or a syn-thesizer with the LO signal. Series net-work R9 -C20 is fitted at the input of theIF amplifier because any passive DBMshould be correctly terminated on atleast two of its ports. To compensate forthe 6 dB conversion loss in the DBM,and to ensure some spare IF gain,medium power RF J-FET Ts is dimen-sioned to provide a gain of about 12 dBat a drain current of 25 mA.The proposed front-end gives fairly goodresults: its third -order intercept point isbetter than 0 dB when a mixer is usedwith IP = +20 dBm, while the noisefigure is about 4 dB. This sort of per-formance should enable the reception ofquite weak transmissions even with apowerful transmitter within a few milesfrom the receiver.Finally, due account should be taken of
the fact that the IF output easily delivers10 mW, which may well give problems ifthe IF amplifier is not properly dimen-sioned.
Inductor data for this project:Li ...Ls incl. =E526HNA10014 (Toko).L6 =E526HNA10013 (Toko).
. . L9;L14 = 6 turns 36SWG(0 0.2 mm) enamelled copper wirethrough a ferrite bead.
= 9 turns 24SWG (0 0.6 mm) en-amelled copper wire on a T25-12 ferritecore; tap at 3 turns from C35-Ri5-Ri6.
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70 EE
January 1988
ktEADERS SERVICES READERS SERVICEPARTS & BOOKS
All orders must be sent BY POST toour Brentford office using the appropriate form opposite. Please note thatwe can not deal with PERSONALCALLERS, as no stock is carried at theeditorial offices. The postal address isgiven at the back of the form.All prices shown are net and customersin the UK should add VAT whereshown. ALL customers must addpostage and packing charges for ordersup to £15.00 as follows: UK, £1.00;Europe, E1.50; other countries, £2.00(surface mail) or E3.00 lairmaill. Fororders over E15.00, but not exceeding£50.00, these p&p charges should bedoubled. For orders over £50.00 invalue, p&p charges will be advised.Software is also available fromTECHNOMATIC LIMITED (for address,see inside front coved.In Sweden. printed -circuit boardsshould be ordered fromELECTRONIC PRESSBox 63S182 11 DanderydTelephone: 08.753 03 05
SUBSCRIPTIONSSubscriptions can be providedanywhere in the world: they may beordered on the appropriate form op-posite
LETTERS
Letters of a general nature, or express-ing an opinion, or concerning a matterof common interest in the field of elec-tronics, should be addressed to TheEditor. Their publication in Elektor Elec-tronics is at the discretion of the Editor.
PAST ARTICLES
A limited number of past issues can besupplied at the current cover price pluspostage & packing as detailed above. Ifpast issues are no longer available,photo copies of the relevant article canalways be provided at a price of £1.00per article plus postage and packing asdetailed abov
TECHNICAL QUERIES
Although we are always prepared toassist readers in solving difficulties theymay experience with projects that haveappeared in Elektor Electronics duringthe PAST THREE YEARS ONLY, weregret that these can not in any cir-cumstances be dealt with by telephone.
COMPONENTS
Components for projeca, aring inElektor Electronics are usually availablefrom appropriate advertisers. If difficult-ies in supply of components are en-visaged, a source will normally beadvised in the article
BOOKS
The following books are currentlyavailable: these may bre orderedfrom certain electronics retailersor bookshops; or direct from ourBrentford office
301 Circuits E6.25302 Circuits E6.25
BINDERS
Elektor Electronics binder E2.95
FRONT PANELS
Indoor unit for sate!.
No. Price1E1
VAT(El
lire TV reception 86082-F 3.50 0.53Topof-the.range 86111.F1 5.60 0.84
preamplifier 86111-F2 4.45 0.67Digital sine -wavegenerator 87001-F 5.45 0.82
Autoranging DADA 87099-F 2.80 0.42Frequency meter 87286.F 10.75 1.61
SOFTWARE
Software in IEIPROMs
pP-controlled frequency
No. Price10
VAT1E1
meter 1 x 2732 531 9.00 1.35X -Y plotter1 x 2732programmable timer
532 9.00 1.35
1 r 2732 535 9.00 1.35GHz pre -scaler1 r 2732automate yourmodel railway
536N 9.00 1.35
1 2716marine computer
537 7.30 1.10
1 x2716 538 7.30 1.10Jumbo clock2 v 2716 539 14.60 2.20Graphics card2 82S123printer buffer
543 9.60 1.44
1 x 2716 545 7.30 1.10MSX EPROMmer1 r 27128 552UK 7.30 1.10EPROM emulator1 8748H 588-AI5.00 2 25
PRINTED CIRCUITS
Readers who wish to make their ownPCBs Hof private and personal use only)may In many. but not all. cases receivethe relevant drawings free of charge byordering these on the order form oppositeand enclosing a stamped addressedenvelope foreferably 9 <6 in or230x 150 men.
FEBRUARY 1987
No. Price(El
VAT
Pitobite studio unit 86047 21.00 3 15Electron ROM card 86059 5.70 0.85VLF add-on unit foroscilloscopes 86135 5.05 0.76
Dioilal sine -wavegenerator 87001 7_50 1.13
9968-5 2.05 0.31
MARCH 1987hASX EFROLtme.rValve preamplifier 1
Stereo VU meterBiphaser
APRIL 1987Valve preamplifier -2Facsimile interfaceLirkwitz filters
MAY 1987Capacitance meterMetal detectorMIDI signal castributionSpot save waveceneratoc
JUNE 1987Intercom for motorcyclists
Spot sine wavegenerator 2
AutorangSng OMNI
JULY/AUGUST 1987Wien bridge lascallalialDuty factor analyserDigitd voltageCurrentdieP4Y
32 K pseudo ROMHeadphone amplifiesHalogen tame dimmer7_ get cc -de 'C.47.31
SEPTEMBER 19873..irface-rnoi:nt stereoFM recenier
16 Kbyte CMOS RAMfor C64
Active phase linearfilter
EPROM emulator
OCTOBER 1987)5E8 -t-daceSS3 adapter14 -bit D.A converterRecording Playback
amp-4fterLow noise microphone
amplifier
NOVEMBER 1987SSB Receiver for 80 marid 20 m
BASIC computerDimmer for inductive
toads 87181 6.00 0.90IR Transceiver 87179 Not available
No. Price VATIn lE1
37002 9.5087006-1 8.5086111.3a 6.9087022 1.7587026 8.20
1.431.281.040.26t.23
87006-2 12.52 1.8887038 8.83 1.3284071 7.26 1.09
860428606987012
5.154.257_40
0.560.641.11
87036.1 not avalehae
87021 6.85 1.03
87036-2 rat aysiefe87099 6.55 0.98
87441 2.15 0.3287448 5.85 0.88
8746887500875128745267463
6.50 0.984.00 0.609.00 1.35
rise asseabilerot ay -4L;
87023 3.20 0.46
87062 .1.10 0.62
87109 15.00 2.2587136 17.50 2.63
870548714587168
Not availatieNot avaaatr.e
7.25 1.09
87486 Not available
37058 3.45 0.52
87051 14.75 2.2187192 20.25 3.04
DECEMBER 1987Digital motor driver for
models 87098 4.50 0.66Frequency meter 87286-A 12.50 1.8ELCD VU meter 87505 6.75 1.01
87520 6_75 1.01
JANUARY 1988DCF77 Receiver andFrequency Standard
Stereo limiterLight -powered
themorroterSwitch -mode PSU
86124-A8710587168
8.70 1.31Not avalable7.25 1.09
87188 6.75 1.01580001 5.00 0.75
"ADVERTISEMENTSEicklar Etectrofpcs is pualisried on the thirdThursday of the month preceding coverdate. Closing date for copy is five weeksbefore publication date for both colour andntanotofne-The Publishers will not be liable for anyloss occasioned by the failure of anyadvertisement to appear from any causewhatev; nor do they accept liability forprinters' errors, although every care istaken to avoid mistakes. Advertisers' prop-erty. artwork, etc, is held at owners' risk.and should be insured by them against fireor other damage.Copy arid illustrations are in all cases sub-ject to the Publishers' approval and mustcomply with the code of advertising prac-tice in force in the country or countries ofpublication. The advertiser will indemnifythe Publishers against arty contravention ofany Trade Act in force in the country orcoutries of publication. The Publishersreserve the right to refuse. suspend, orcancel any advertisement or series ofadvernsements. In all cases, thePublishers' Standard Terms of Businessapply (see reverse of Parts & Books OrderForm opposite/. The placing of space reser-vations by the advertisers or their agents isdeemed by the Publishers to imply accept.once of, and agreement to be bound by.these conditions.
Advertisement sizesTrim size : 297mm 210mmFull page : 265mm x 185mm
page : 130mm x 185mm Moral265mm x 90rrim (vest)
1.1 page : 63mm x 185mm Ihorizl130mm x 90mm (weft)
Ye page : 63mm x 90mmClassified & semi -display column width:60mmFull pagebieed sae: 303mm x 215mm
Production detailsPrinting : offsetScreen : 13W 40.'cm 1100inchl
colour 60:cm (150inch)Required material : litho artwork or
same sire wrongreading negatives(mono)colour separatedfilm positives andprogressivesicolourt
Agency commission: 10%
Advertisement ratesFull page E440.00Half pace £245.00Quarter page £145.00Eighth page £95.00Special positionor facing matter r 15%Cover position 25%Bleed + 10%Additional colour £200.00Classified ads 45 p per word
(min 12 words)Semi display ads E10.00 per single
column cm (mill 2.5 cm)Series discounts are available on appli-cation.All prices are subject to VAT at the stan-dard rate.
EDITORIAL CALENDARIssue
Publication Copy deadline Main themedate Advertisements* Articles
January 1988February 1988March 1988April 1988May 1988June 1988JulyiAugust 1988September 1988October 1988November 1988December 1988January 1989February 1989March 1989April 1989May 1989
17 Dec. 198714 Jan. 198818 Feb. 198817 Mar. 198814 Apr. 198812 May 198816 June 198818 Aug. 198815 Sep. 198820 Oct. 198817 Nov. 198815 Dec. 198819 Jan. 198916 Feb. 198916 Mar. 198920 Apr. 1989
9 Nov. 19874 Dec. 1987
15 Jan. 198812 Feb. 198811 Mar. 19888 Apr. 1988
13 May 198815 July 198812 Aug. 198816 Sep. 198814 Oct. 198811 Nov. 19885 Dec. 1988
13 Jan. 198910 Feb. 198917 Mar. 1989
26 Oct. 198720 Nov. 198728 Dec. 198729 Jan. 198826 Feb. 198825 -Mar. 198829 Apr. 1988
1 July 198829 July 19882 Sep. 1988
30 Sep. 198528 Oct 198821 Nov. 198530 Dec. 198827 Jan. 19893 Mar. 1989 .
HF & VHF TechniquesTelecommunicationsSensorsEtectrophonicsArtificial IntelligenceElectronics & ArtAmateur Radio & TVCom:.,.:e.s u MicroprocessorsPow-. - - :
Optce c_...." :s-- ---. _._ _Corr: cect test & measurement
Aud . .i HA,TV & ,.aeoKnowledge -based systemsTelecommunicationsRobotics
One week later for camera-ready copy.
EE
January 1988
NEW THIS MONTHSB6 AUDIO £6.00
OSCILLATORTunable from 500 to 5000HzSwitch (al tone aloneselection Ibl light alone
(c) tone and lightFor use with morse keys.Dims 160 x 95 x 55mmPower 9V batterySB1 CAR LIGHT £1.00Automatic tilt -sensitive lamp for per-manent attachment to bonnet or bootlid. Internal mercury switch detects tiltand switches light on when openedand off when closed. 5W bulb givesgood overall illumination. Mountinghardware and instructions supplied.Dims 59 x38 x 27mm (body)
SB2 Video/Audio dubbing kit £2.501 twin co -axial lead - 2 phonoplugs to 2 phono plugs 2m2 adaptors - phono socket to3.5mm jack plug
2 adaptors - phono socket to BNCplug (male)
' 2 adaptors - phono socket toPL259 (UHF) plug
2 adaptors - phono socket to "F"type plug
SB10 BNC LEADS £2.504 x BNC plugs to 4 x BNC plugs pro-fessional RGB hook-up. Colour black.Length 1 2m
Z810 KEYBOARD Really smart alphanumeric standard qwerty keyboardwith separate numeric keypad, fromICL's 'One Per Desk'. Nicely laid outkeys with good tactile feel. Not en-coded - matrix output from PCB takento 20 way ribbon cable. Made by Alps.Size 333 106mm 73 keys £8.95
BARGAIN Of THE
Z004 Skeleton Joystick, switchtype. Good quality, made by AB.Brass spindle has 44mm longblack plastic handle attached.Body has 1 mounting holes. Thesereally are a fantastic bargain!!
ONLY E 1.00
Z811. Cumana Touch Pad for the BBCcomputer. This remarkable add-onenables you to draw on the screenusing a stylus with the touch sensitivepad. Supplied with 2 stylli, power/dataconnecting lead & demo tape with 4progs. Contains state of the art elec-tronics. Originally being sold at£79.95. later reduced to £49.95 -but we can offer a limited quantity ofthese brand new and boxed for just
£19.95
1988 CATALOGUEOUT NOW - 88 pages of bargains frontresistors to disco mixers. Price in-cludes latest bargain fist, discountvouchers, order form. Don't be with-out your copy - send £1.00 now!!SWITCHED MODE PSUAstec type AA7271. PCB 50 x 50mmhas 6 transistor cct providing currentoverload protection, thermal cut-outand excellent filtering. Input 8-24VDC. Output 5V 2A. Regulation 0.2%.£5.00SPEECH CHIP2733 SP0256A ÷ index chip ÷ ULAchip as used in Currah microspeech.Cct and info for using SP0256 withSpectrum, ZX81, BBC, VIC & C64. Noinfo on other 2 chips. All 3 for £3.00AUTO DIALLERSloping front case 240 x 145 x 90/50contains 2 PCB's: One has 4 keypads(total 54 switches) + 14 digit LED dis-play. 2 x ULN2004. ULN2033 & 4067:the other has 12 chips + 4 powerdevices etc. Case contains speaker. 8core cable 2m long with plug. FT' usewith PABX 00
Z652 Coin acceptor mechanism. Madeby Coin Controls, this will acceptvarious size coins by simple adjust-ment of 4 screws. Incorporates varioussecurity features - magnet, bent coinrejector etc. Microswitch rated 5A240V_ Front panel 115 x 64. Depth130mm. Cost £10.85.Our price £4.00SOLAR CELLSGiant size. 90mm dia giving 0.45V1.1A output. £4 each; 10 4 £3.50.Mega size - 300 x 300mm. These in-:orporate a glass screen and backingPanel. with wires attached. 12V200mA output. Ideal for chargingnicads. £24.00
SOLDER500g reels resin cored. 18g £5.95500g reels resin cored 22g . £7.95
LOGIC PROBE!=or TTL. CMOS etc. LED and sound inaication. Pulse enlargement capabilityallows pulse direction down to25nsec. Max f = 20 MHz 4-16V. liPZ:1M £9.99
NEWBRAIN PANELSZ494 Motherboard microprocessoraanel 265 x 155rnm Complete. PCB forzamputer. Z80. char EPROM etc. 68_nips altogether - other associatedcomponents, plugs. skts etc_ _ £5.503OWATT AMPLIFIERZ806 Sturdy steel case 305 x 300 x120mm contains ILP HY6O ampmodule, control/pre-amp PCB. PSU,small monitor amp + speaker E12.50
+ £3 canZ807 As above but incorporatescassette deck built into top of case,also batt. back-up (3 x 6V 1.2AHsealed lead acid bans). Push buttonbank on front panel controls cassette,power etc. £22 + £3 cartFull details of these on BIL 33K568 GIANT PLASTIC PACKApprox 1000 pieces - standard andminiature PCB supports, self adhesiveribbon cable clips, straps, ties, cordclips. This lot would normally costaround £50!! Our special priceE12.00K563 Cable markers fident sleeving)Over 1,000 pieces, all with either letteror number. Assorted colours and sizesfrom 1-5mm dia. Over 50 different!
Pack of 1,000 f2.50
MM.GREENWELD
ELECTRONICCOMPONENTS
Ai prig ilidide VAT; just add £1.00 P&P.bran Access order £10 Ilis rarer. cwo). Ofkrsl.orders from et; vi -e -
come - rnin M.: 7: 7" f SO.Our 9104 has r . of CcerpOnantS and it corn
9-5. - a:. r_:bthe and see _s'"Serd SAE lor = ern Lst
443E Millbrook Road SouthamptonSO1 OHX Tel 107031 772501 783740
16111" AS.. AOil' clef
"IIIIIIIIIFI .1 .1%11:0111111111. 11101k iltli till it
ort5t
F (31 00)O 11iNSI1G
A etlikel SendOW0vS 50p* & SAE
for CATALOGUEORDERS. RING /011 567 8510 - 24 HRS.
NEW POWER STROBE KIT MICROPROCESSOR TIMER KIT
Designed to prod..ice ahigh Mtensitypar. at a variable fm-quency of 1 to 15Hr.,,,,,descircuivy to n c-_,.. the
Des',)1,-ind to men-trot 4 outputs in-aeaa'aSaa_._ aY'witching on andoff at preset tover a 7 -day cycle,
'f----)
''...L.ff B
ifl- .-re-....-
strobe ti., ,..e.haisource leg. a loot, -..--, .r -r) via a- ca:_ :tar,
'nstructions are ; , . supply. i ,1-112
tha unit far mar-,, : f ,a,,,,,
photryee.iii, a.. ___: _ i cr 35 a wernmgteem, in sem:Yr . -... .:,-. cra. The kit in-
5 2 ,O c,., 1. . at components. con-_ - =:.e . ..na and rut easenhiy
nst-c: ;re 51.s....,.. 240V as- Size:
75.50.45XK124 STROBOSCOPE KIT £12.50
LED display oftone and day. easy Programmed via 20 we,keyboard. [deal for central heating control M-ckecreig different switcl 'Xing tine for week=sids_Battery back-up circuit. Includes box. 18 tinePalts195-CT6000K £42.90Ye1114: Relay kit for CT6000, includes PMcont.extuie and one relay. V. accept up to 4Ways. 3A/240V clo contacts £4.30701 115: Adcfnional relays £1.80
VERSATILE REMOTEW41'/FL:181t/orti.'fi
One of the best deter.--.---- rents a burglar is a
n?_r_ .:_,,,,.. -- -.- gLordto
dog and this
i -- , new kit provides the-,g ._ sarking without the0,,k=-Zi- t, bite! The kit when
asserribIed. can bec:- -ec:.; to a rl....:-.ce. cre<s.... -_.:r any
Other totruder cfe:.:7= - - : .... - -= ,,, ear--
dam scler ofth ee.e- - ; :..- a - , -c thewe. :'= _. a --cruder tr.:, a :a-- ann try h< luckeL.e.,..e.e The kit is a_: complete withhigh gra cy pca trar,..-. . a i componentsend an...inactions. Al[ . :t.. reamssupply. intiuderdetact:_.,. The
kit even includes a horn ca., -- which isessential to produce the for; r- .-; required.The -deg- ran be ..criu, 5,, -....,, barks
froma Tattier to anA and con-tails circuitry to produce a r-- -_-:-, series esbarks giving a more realistic .. " -XKI25 Complete kit of pats £21.95
CONTROL KITThia kit "acia'aes -es comporienz - '! ..-
(-. transformer)
to mak: a sa°a4- --.
OW'" reae°e'with 16 logeoutputs 40-15V1 which vim ' ' ' t --CiTC,OITY (relays. Mess, etc a.la = = _ .. ,
can be used ta swath Le' ta 16 °' --. -meat on ae off ramatell.' The a'"°'''''-' a`
latched (to the last received codei or mornen-tary (on during transmission) by specifyirg thedecoder tC and a 15V stabiTned Sutpply iSa.sgable to paver external circuits_Si--,:c'i 2.20'.' AC or 15-24V DC at lli,4S.:, , -_- . , -; trensforrned 9 2 . ::-==
is rite .' ' , ... - . -
:am aTrue ::-: a - an transm
9V PP3ittercar.
. .. =.7operates f ..- . .e.range of LIP to 60ft T.,.= -.: .1,.my.fable f.11(9 (4 -way) and Y....1. E
.,21...arl,
c.-pencftig on the number of outputs to be user:MK12 IR Receiver arid_ transformer)
£14.85DISCO LIGHTING KITS MK18 Transmitter E7.50
DL1000K - Th.s vaUs-formcnei 4-0,..-ey
chaser features bi-croectiormi see.ence anddimming. 1kW per channel E17.50
MK9 4 -Way Keyboard E2.00MK10 16 -Way Keyboard £5.95601 133 Box for T-e.nann.tter £2.60
DL21000K -A )Owen cost uni-directional vet-sion of the above_ Zero switching to redu£9.8ce in -terference 5
PROPORTVOIAL TEMPERA -TURF e,NYIOLLER KIT
DL.Arl Ito, DL & 01110001(1 Optional opto in-put allowing auth-o lseat'ilight response 70pDL3000K - 3 -channel sound to Tight kit lea-trees Zero voltage muitching automatic levelcontrol and bielbin microphone. 1l4V perchannel. E1425
The DL8000K is an 13 -way sequencer kit Withbutt in opto-isolated sound to Tight input
. = = = 'burst fee":;.--- 4ott to men-tam temperature TOwithin 0.5°C. Idealfor photography.incubators, wine -making. etc. Max.
load 31cw(240V ad. Temp. range up to 90.C.Sue 7 x 4 .2.5 ems. MK4 E7.10
whecn comes complete with a OM'
OtOgraffirrt EPROM containing EIGHTY - HOME LIGHTING KITSYES 801 different sequences including sten-dard flashing arid drase routines_ The KIT in-dudes full instructions and all components!even the PCB connectors) and requires only aLm and a control knob to complete Otherfeatures include mania/ sequence speed ad-patmenL zero voltage switching, LED mimictamps and sound to fah[ LED and a 300 Woutput per channelArid the best din° about it is the c .,
4 it #_144,4o-Ly E 28 . 50If
i
.. __
These kits contain a/ necessary componentsand 6 -Winona -bans & are designed to replacea standard wee switch and control up to300w. of righting.TDR300K Remote ControlDimmer E16.45
MIC6 Transmitter for above£4.95
117300K Touchifenmer E8.50TS300K Toucltswitch E8.50
Th" Extension kit for 2 -wayswitching for 70300K . _ . _
/11:1I
_......1/---
%-'
e71 --JA--- _-
SEND 9"x6" SAE & 60p FORELECTRONICSnCATALOGUE OR CALL AT13 BOSTON R' SHOP Mon -Fri 9_5 pm
LONDON W7 3SJ Saturday 10-4 pmTEL. 01 567 8910
WM ORDERING INFORMATION:VAT AMALL PRICES EXCLUDE
FREE P&P on orders over £20 (UK only), otherwise add 75p + VAT.Overseas P&P. Europe £2.75. Elsewhere £6.50. Send cheque/PO/
Barclaycard/Access No. with order. Giro No. 529314002.LOCAL AUTHORITY AND EXPORT ORDERS WELCOME
GOODS BY RETURN SUBJECT TO AVAILABILITY
1988 BU
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Tel: (0272) 232014
