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THE INTERNATIONAL ELECTRONICS MAGAZINE

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surround-soundsubwoofer

CONTENTSIR March 1996 Volume 22

Number 242 ISSN 0268/4519

AUDIO/VIDEO

62 PROJECT:surround -sound subwooferDesign by T. Giesberts part l

CONIPUTERS & MICROPROCESSORS

32 PROJECT.PIC RDS decoderDesign by U. Nagel

40 PROJECT.PC soundcardas AF analyserDesign by M. Ohsmann

FOCUS ON

18 PC memory chipsBy our Editorial Staff

GENERAL INTEREST

di 14 PROJECT:111 houseplant buzzer

Design by P Kersemakers

focus on:PC memory chips

RADIO, TV & CONINIUNICATIONS

52 PROJECT:satellite finderDesign by C. Denolle

TrisT & MEASUREMENT

24 PROJECT:switched -capacitoraudio filterDesign by F. Hueber

MISCELLANEOUS INFORNIATIOIi

69 constructionguidelines

57 datasheets82 index of advertisers49 new books48 new products9 news from the world

of electronics82 next month in

Elektor Electronics73 overview of

EMC guidelines68 reader's letters70 readers's services81 switchboard46 the INTERNET page

sr IDIJIL1 ffilillOWNie ElairtiOrElw(ritressateso L.litlitsy, gem willreceive alasehatelig FREEcopy of the bestffirselling

3111 rfrcuits801 r0Qd9Q

Complete the subscription order card at theback of this issue and send it to the addressshown: there is NO postage to pay. As soon asthe card and your payment are received,Elektor Electronics will be delivered to yourhomeaddress for a year (11 issues).

Eurofighter engineer is1995 Young Woman

Engineer of the YearA twenty-nine year -old senioravionics systems engineer withBritish Aerospace. Pamela Wil-son, was chosen as the YoungWoman Engineer of the Year ata ceremony held in London inJanuary.

Pamela, who already regu-larly visits schools and collegesto explain her interesting job,told Elektor Electronics at theaward presentation: 1 wentinto electronics because I wasinterested in how thingsworked."

A graduate member of theIEEIE, Pamela was runner-upfor the 1992 Young Woman En-gineer of the Year Award andthis time she was voted by thejudging panel top of the six fi-nalists and was presented thecoveted award for 1995. acheque for £ 750 and a silverrose bowl.

Pamela joined the MilitaryAircraft Division of British Aero-space Defence at WhartonAerodrome, Preston. Her two-year graduate training involvedplacement in equipment engi-neering, research and develop-ment and system design. As aresult of her final training place-ment, she stayed with the Eu-rofighter 2000 cockpit groupwhere she was promoted toAvionics Systems Engineer.Her work is primarily definingthe man -machine interface re-quirements for the sensorscontrol within the EF2000 cock-pit.

Pamela is the eighteenth re-cipient of the Award, which isjointly sponsored by the Institu-tion of Electronics and Electri-cal Incorporated Engineers(IEEIE) and the CarolineHaslett Memorial Trust (CHMT).The aim of the Award is tohighlight electronic and electri-cal engineering as a rewardingand worthwhile career forwomen. Previous winners andcontenders for the Award havemore than proved that womenmake extremely competentelectronic and electrical engi-neers at Incorporated Engineerlevel -a career once almostexclusively male -dominated.

Prior to the winner beingannounced, a video of all sixaward finalists at work wasshown to representatives fromindustry, commerce, academia

and media who attended theceremony whose organizersstill see a crying need for theevent in years to come.

Runner-up for the 1995Award and winner of the WISEprize was Audra Gittens, a 28 -year -old test engineer withRobinson Instruments, Run-corn. Cheshire. Audra_ a gradu-ate member of the IEEIE. waspresented with a cheque for£ 500.

Third -prize winner. Rose-marie Haycroft, received acheque for £ 250. Rosemarie,27, is a switch maintenance en-

gineer with Cellnet MobileCommunications and is basedat the Manchester Switch Cen-tre in Salford.

Twenty -two -year -old YvonneMorris. an electrical engineerP4 Grade with British Aero-space (Dynamics) Defence inStevenage received the MaryGeorge Memorial Prize-an ad-ditional award given to a youngentrant showing particularpromise as an IncorporatedEngineer. Yvonne received acheque for £ 250 and a silversalver.

Electronics a keyBritish industry

Britain's electronics business istoday the fourth largest in theworld after the USA. Japan andGermany. and by the year 2000electronics will be the world'slargest industry accounting forsome ten per cent of mankind'sGDP. The alliance of telecom-munications. information tech-nology. new digital electronicstechniques. and multimediacommunications networks al-lows a wide range of previouslydisparate industries to con-verge. The affiliation of of con-sumer electronics, cable TVand broadcasting. mediagroups. information services,publishing, software, banking.and retailing among others has

been the result.At the same time, the

rapidly growing use of elec-tronics in Britain and elsewheregives the industry the status ofa key industrial sector. Addi-tionally. electronics is an es-sential enabling technologythat drives competitiveness,and even wealth creation, in therest of UK industry, too. Be-tween 1985 and 1990. the UK'sshare of electronics exports bythe (G7) major industrializedcountries increased from nineper cent to 11 per cent, thelargest recorded rise.

Electronics has become asignificant force and, with elec-trical engineering, is now the

second largest industry in theUK. The industry's sales areworth £ 30 billion. and yearlyinvestment runs at some£ 1 billion, alongside R&D's£ 2 billion. The workforceamounts to some 330,000.

As each year passes, elec-tronics assumes more promi-nence in UK manufacturing.Value added increased byeight per cent yearly in the1980s. and the industry in-creased its share of manufac-turing output from five per centin 1981 to seven per cent in1990. Electronics in the UKis becoming less concentrated.Large enterprises employingmore than 1000 now represent55% of the sector from around70% in 1980. Nearly 50% ofelectronics employment lies inthe southeast. although Scot-land and the West Midlandsgenerate the highest valueadded per employee.

Capital equipmentBritain is particularly strong intelecommunications, data pro-cessing and software, along-side the provision of capitalequipment for civil and defencepurposes. Heavy investment inR&D demonstrates the indus-try's commitment to innovationwith funding averaging six percent of turnover.

Electronics' internationalnature is behind the UK'ssteady trend towards the devel-opment of international stan-dards, which in turn creates theopportunities for the UK indus-try to exploit new markets.Hardware and software manu-facturers are also meeting in-creasingly stringent securitystandards.

The UK industry knows itseconomic future depends uponits continuously improving itsposition in the global market-place. The Federation of Elec-tronics Industry (FEI) repre-sents the industry where mem-ber companies are developingtheir response to the challengeand are pursuing policies tomaintain their position amongthe world's electronics front-runners. FEI, formed in January1994 from the sector's two pre-vious trade associations, bringsUK -based telecommunications,information technology, com-puter services, defence elec-tronics and office products, aswell as electronic componentsunder the same banner.Federation of Electronics In-dustry. Russell Square House.10.12 Russell Square, London,United Kingdom WC1B 5EE.Phone +44 171 331 2000. Fax+44 171 331 2040.

ELEKTOR ELECTRONICS MARCH 1996

Differential GPSfor land use with RDS

By M. Ohsmann

The Global Positioning System,GPS. originally developed by theAmerican Defence Departmentas a world-wide satellite -supportedpin -point navigation system, isnow widely used for civilian pur-poses. Receivers for civil pur-poses have been available andin use sincethe mid 1980s. Thesereceivers are useful for a varietyof purposes, for example. yacht-ing, in -shore fishing fleet man-agement of road transport, andsurveying.

The system is based on aGPS station receiving the signalsfrom several satellites. Assumingthat the exact time (uTC-uni-versai time co-ordinated) is known,the time of receipt of the varioussignals enables the distance tothe different satellites to be com-puted (the satellite transmits ITCalso). Since the positions of thesatellites are contained in thetransmitted signal, the position ofthe receiver can be establishedfairly accurately if signals fromat least three satellites were re-ceived. The exact time can be cal-culated at the receiving stationif the signal of a fourth satelliteis also available. The position ofthe satellites is transmitted by thesatellite. The position accuracyis less than a metre. More than20 satellites ensure that at leastsix satellites can be received atany point on earth-see Fig.. 1.

Degraded accuracyAlthough the accuracy mentioned

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earlier is available to the militaryand special services user, it is notto the civilian user. This is calledthe standard positioning servicewith selective availability. It meansthat the civilian user cannot reckonan accuracy of better than 30-100metres. This degradation arisesfrom the fact that the satellitesignals do not tell the civilianuser its exact position, Luta slightlydifferent one. This causes a po-sition error at the GPS receiver.Moreover, the generated errorslowly changes.

Improved accuracyThe artificial degradation of theaccuracy is countered as follows.A GPS receiver in an exactly knownposition serves as a reference .This reference receiver can de-

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termine with a fair degree of ac-curacy which satellite 'lies' towhat extent. If itthen makes thesedata known to other GPS receivemthese can improve the accuracyof their own estimated positiongreatly, since they know to whatextenttheirposition was degraded.This system of operation is knownas Differential Global PositioningSystem-DGPS*. The data com-puted at the reference stationare called the DGPS correctiondata. These have to be commu-nicated to the GPS station by radio.A typical setup of this is shownin Fig. 2. There are various waysof doing this and these are de-scribed below.

Local auxiliarytransmitterIf the area in which the GPS ac-curacy is to be improved hasnarrow limits, such as an airfieldor the lands of a farmer, a small,low -power local data transmit-ter can be used. Such a setupmight cost a couple of thousandpounds, which makes it afford-able only for professional appli-cations. A number of airports areevaluating such system for futureGPS supported blind landingprocedures. The accuracy of DGPSin association with local auxil-iary transmitters may be betterthan one metre.

Shortwave broadcastswith RDSDuring the pastten years,the RDSsystem has come into wide usefor the transmission of additionaldigital information on the broad-cast signal. This system may alsobe used to transmit DGPS data(see 'PIC RDS decoder' in this

Events in 1996

March26-28: The Nepcon Elec-tronics Exhibition at theNEC, Birmingham. UK.28: A Mobile Communica-tions Workshop at GatwickAirport

AprilThe Sixth InternationalConference on AC and DCtransmission will be held atthe Institution of ElectricalEngineers (IEE) in Londonfrom 29 April to 3 May 1996.

May8-9: The ElectronicsScotland Exhibition atGleneagles. Scotland.21-23: The Internet WorldExhibition in London.

June4-5: The ICET 96 confer-ence on electronics tech-nologies in Brighton, UK.

July16-18: The SemiconiWest96 exhibition and confer- -ence in San Francisco.

AugustThe CeBIT Home Trade Fairwill take place at Hanover,Germany on 28 August to 1September.

September2-8: The FarnboroughAirshow at Farnborough,UK.

October8-10: The Euro-EMC exhibi-tion at Sandown. UK.18-27: The Connect 96 con-sumer electronics show atthe NEC, Birmingham.

November12-15: The Electronics 96exhibition in Munich.Germany.26-28: The ManufacturingWeek Exhibition at the NEC.Birmingham.

December8-11: The InternationalElectronic DevicesMeeting in San Francisco.

issue). Several European sta-tion do so already. A typical arrange-ment is shown in Fig. 3. Figure. 2shows that the position computedby a standard GPS station overa peexl of 24 hours drift by ±30 me-tres from the true position. Witha DGPS station, the drift is lirn-


In brief

International confer-ence on Public Trans-

port Electronic SystemsElectronics. computing andcommunications systems arebeing employed in evergreater degrees of sopltstica-lion. This international confer-ence to be held at the Institu-tion of Electrical Engineers inLondon on 21-22 May ad-dresses the application ofthese system in all areas ofpassenger transport, either ason -board units or as part of thefixed transport infrastructure.

Embedded C51 StarterSystems from Equinox

Equinox Technologies haslaunched a range of Embed-ded C51 Starter Systems forthe 8051 microcontroller fam-ily. These systems allow theuser to develop embedded8051 applications in C. usingan integrated programmer/edi-tor/compiler/source level de-bugger environment_See page

Teletest 16 Emulatorfrom Hitex

While much attention has beenfocused on the arrival of em-bedded versions of the 386processor, chip manufacturersIntel, AMD and NEC continueto enhance the 16 -bit mem-bers of the x86 family byadding embeddable-friendlyfeatures to the popular186!188 and V -series proces-sors. thus ensuring their con-tinued use in control appli-cations.To support these devices,Hitex has introduced a rangeof emulation pods and cablesfor the popular T16 in -circuitemulator, offering existingusers with an upgrade path intheir designs.See page

Microelectronicsin Business

Under a new Euro-Practice Ini-tiative. five MIB Support Cen-tres have been appointed asTechnology Transfer Nodes(rrNs). They are sited at theUniversities of Paisley, Glamor-gan, Hertfordshire andBournemouth. and at theBolton Institute. The nodes willprovide a UK delivery mecha-nism to companies seekingsupport under the Euro-Prac-tice 'First User Action' scheme(Fuse), designed to comple-ment existing an programmessuch as 'Microelectronics inBusiness'.

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ited to ±4 metres. This meansthat a DGPS station can determinethe true position fairly accurately.This system can be used with rea-sonably priced receivers (DIY?);it does not need many transmit -

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veloped for long -wave broad-casts on to which digital data(200 bitis) inaudibly are super-imposed. Its structure is similarto RDS and may also be used forthe distribution of DGPS correc-tion data. A number of Europeanstations transmit these broad-casts on an experimental basis.Since the distances spanned bylong -wave signals are very large,such stations can serve a verysubstantial area. The distance be-tween the reference station andthe local receiver may be as muchas 1000 km (600 miles). but thismay limit the achievable im-provement in accuracy. In otherwords, the correction data losesome of their usefulness overlong distances.

Long -wave servicesApart from long -wave broadcastingstations, there are private orga-nizations that distribute DGPS overlong -wave radio networks. InEurope, the German and DutchTelecommunications Authoritiesare using the system at a num-ber of sites and are evaluatingits use at other locations.

In conclusion, it may be said thatthe DGPS, already in usefor sometime in the uK and uSA, is nowbeginning to find widespreaduse in mainland Europe in a num-ber of areas as well.

* Editor's note. This system hasbeen in maritime use since thelate 1980s.

Physics World -

High Technology in actionThousands of scientists fromthe Uk and overseas will be inTelford in April for the annualPhysics World Exhibition, themost important UK event forphysics related technologies.

Run in conjunction with theInstitute of Physics AnnualCongress, the exhibition(Telford International Centre,23-25 April, 1996) enables sci-entists to evaluate, compareand place orders for the prod-ucts and allied services dis-played and demonstrated byover a hundred leading scien-tific suppliers. Exhibitors will

show a wide ranae of hightechnology solutions, relatingparticularly to vacuum andsemiconductor processing, nu-clear technology, environmen-tal physics, spectometry, mi-croscopy, optics and lasers.

The Institute of Physics An-nual Congress. alongsidewhich the exhibition runs, aimsto increase recognition of theimportance and relevance ofphysics in all aspects of ourdaily, personal and profes-sional lives and as such is of in-terest not only to physicists,but scientists and engineers in

a wide N.ariety of sectors anddisciplines. The programme ofscientific conferences will covertopics as wide-ranging as re-cent developments in siliconsensors, the physics of musicalinstruments and the latestphysics R&D.

Full information on all as-pects of Physics World Exhibi-tion is available from The Insti-tute of Physics, 47 BelgraveSquare. London SW1X 80X.Telephone +44 171 235 6111.Fax +44 171 259 6002.e-mail [email protected].


In passing ...

We have reached the stagewhere it is difficult to thinkof something that can workwithout electronics. Even asimple and straightforwardmachine like a bicycle hasnot been able to stem thetide.

Many people on citybikes, mountain bikes andstandard bikes pedalaround without paying theslightest attention to theenvironment, but lookingintently at a little box ofelectronics fitted to thehandlebars. This bicyclecomputer faithfully regis-ters distance travelled.time, speed, pedalling rate.and, if so desired, yourheartbeat. A true exampleof modern technical inge-nuity!

I used to have one onmy bike-used to. but notany more; I could notstand it. The problem withthese cipher machines isthat they are ruthless.

You are cycling alonghappily and see that youhave done so many milesalready; this pleases you.Press the button and yousee the time elapsed sinceyou started. Fine! Pressthe button once again andyou see what your speedis: pedal a bit harder andthe speed goes up to18 MPH. But then: trou-ble-you press the buttononce more and see to yourhorror that your averagespeed is only 14.5 MPH.How is that possible. whenyou have been pedallingmuch faster than that?

Gone is the exhilara-tion. The remainder of yourtrip is spent in looking infrustration at the display tomake sure that your aver-age speed goes up. Andso you come home ex-hausted-at an averagespeed of 15 MPH!

When my unequalstruggle with the competeihad reached the stagewhere my well-being andappetite began to suffer,my wife took me aside andspoke to me firmly. Theoutcome of it was that I re-moved the computer frommy bike and now cycleabout again happily un-aware of things like aver-age speed and distancecovered.

What's more, I feel bet-ter and my appetite isback!

UK telecoms pointingthe way to the future

The liberalization of the tele-communications in the UKhas been a spur to both tech-nical and commercial devel-opments. Furthermore. thecountry is moving from aduopoly to an environmentwhere are many operators.

However, while virtuallyeveryone in Britain has bene-fited from reduced chargesand the rapid introduction ofadvanced services, the mostvisible changes have oc-curred in mobile communica-tions. One of the results hasbeen that the battle, originallyfor the phone on the desk orin the home, is equally for thephone -in -the -hand. In fact,fixed and mobile are con-verging with the result that.ultimately, users may havethe universal personal phone.

With six networks fromfour rival operators, competi-tion in mobile communica-tions in the UK is exceedinglystrong. The two cellular oper-ators. Vodafone and Cellnet.which both launched theiranalogue networks in 1985.now also offer GSM-thepan-European digital service.In addition, there are twoPCN networks.

Even before the PCN net-works were launched. thecellular operators introducedlow -user tariffs where, in re-turn for lower monthlyrentals, users paid a highercharge per minute usage.This, coupled with the factthat subsidized handsetscould be bought for less than£ 5, opened the market to theconsumer in addition to thebusiness user. While the lowinitial charge is attractive, theoperators are faced with ahigh level of 'chum' as cus-tomers cancel their contractsas soon as possible oncethey realize the true level ofongoing costs. Hence, it isimportant for operators to in-crease the number of newcustomers signing on while,at the same time. containingthe number of cancellations.

Attractive propositionWith the cellular networks al-ready covering 98% of thepopulation, the emergentPCNs needed and attractivesales proposition-especiallyin view of the fact that theirhandsets were not being

heavily subsidized and thuscost a minimum of £ 150-tocounter their lack of geo-graphic coverage. Whenone -2 -one launched its ser-vice in the Greater Londonarea (roughly 20% of the UKpopulation), it targeted theconsumer market by offeringfree evenings and weekendlocal calls. At the launch,Lord Young. chairman ofMercury' s parent companyCable & Wireless. stated thatthe service was not intendedto compete with the existingmobile networks. but with thefixed telephone network. Thisis obviously an ambitiousgoal.

However, while one -2 -oneconcentrated its efforts in theLondon area. Hutchison Tele-com's Orange is aiming todevelop a national networkas rapidly as possible ad al-ready claims to be availableto 70% of the population.

Thus, it can be seen thatthere are already real choicesfor UK users.

Furthermore, asone -2 -one offers free eveningand weekend local calls tocustomers of its residential(as distinct from business)tariff, the effect is that theseusers tend to identify theirone -2 -one phone as meetingall their communicationsneeds both at home and onthe move. This position isstrengthened by its using theShort Message Service as ameans of indicating that avoice message is waiting.Voice messaging can beseen as providing the userwith a built-in answering ma-chine.

Business toolOn the other hand. Orange'sstrategy is to make its servicea more complete businesstool. Its SMS can be used tosend text messages betweenphones-just like a messagepager, but with a confirmationthat the message has beenreceived. However, one ser-vice that it has had on trial forsome months is a form ofcordless PABX, whereby Or-ange phones can be inte-grated within an organiza-tion's telephone system. Thiscan be seen as the ultimateform of cordless PABX in that'extensions' can be anywhere

within the Orange servicearea. This is getting close tothe ideal universal mobilephone.

While mobile communica-tions has enjoyed a high pro-file, there have also beenmajor changes in the UK'sfixed network stemming fromthe 1991 Duopoly Review.This opened the door for newoperators to provide fixedlink services. The most im-portant new entrant is Ener-gis, owned by a consortiumof the country's electricitydistribution companies. It hasthe benefit of being able toemploy the National Gridpower network to carry the fi-bres of its 2.54 Gbit s-1 Syn-chronous Digital Hierarchy(SDH) backbone optical fi-bres. thus reducing both thecost and time in network de-ployment. In Fact, GordonOwen. Energis's chairman.claims that this results incosts being only about aquarter of those incurred byMercury when it rolled out itsnetwork.

Energis is offering an indi-rect service, where residen-tial and tyasircess customersgain access via their existingBT lines. In addition, it worksin conjunction with regionaloperators. While Mercury, En-ergis and other new opera-tors offer competitive prices.their margins are currentlybeing eroded. This is be-cause, while there is low in-flation. BT is reducing its ownprices to remain within theoverall price formula set bythe Office of Telecommuni-cations (Oftel) of API (RetailPrice Index) -7.5% for thebasket of BTs main prices.

But this is not all. Withinthe European Union. tele-communications servicesand infrastructure are set tobe fully liberalized by 1 Janu-ary 1998. BT and the Germanindustrial group VIAG haveannounced that they haveformed a strategic alliance totake advantage of the newregime. Moreover, AT&T hasbeen granted a telecommuni-cations licence in the UK.Thus, as the world of tele-commnications gets smaller,the importance of the UKgets greater.

12 ELEKTOR ELECTRONICS MARCH 1996

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Unless they are trif-fids*, outdoor plants

are totally depen-dent for their welfare

(water, sun andchemicals) on

Mother Nature.Houseplants are not

that lucky: theydepend on man,

who is often forget-ful when it comes towatering or feedingthem. To help such

negligowners/caretakat least as

far aswater-ing is

concerned,a circuit isdescribed

that enablesthe moisture of

the soil ofhouseplants to

be monitoredelectronically.When the soil

gets too dry, themonitor emits a

series of squeaksto warn the owner

or caretaker to addwater.

by P Kersemakers

14

"Say it with flowers" is a well-known slogan and it is a fact that(most) people like flowers and

* The Day of the Triffids by JohnWyndham (1951) describes a raceof monstrous, stinging plants,mobile and rapidly multiplying,of invasive habit and malignintent. The book was made intoa successful film a few yearslater.

plants in general. Of course, plantsare of tremendous importance to ani-mal life in providing food and oxy-gen. But, where many outdoor plantshave great nutrimental or photosyn-thetic value, houseplants are normal-ly kept for their decorative effect.This decorative effect soon becomesblemished, however, when the plantis not watered regularly.

To help the many people who for-get to look after their houseplantsroutinely, the circuit described here

Elektor Electronics 3/96

will sound a warning when the plantLA. soil becomes too dry and will contin-

ue to do so until water has beenadded to the drying) soil. Owing tothe low current drain, the monitorcap operate from a single dry batteryforwy to a year.

PRINCIPLEThe operation of the monitor

epends on the property of water tonduct when it contains chemicals,ch as alkalines or acids (found in

abun e in good potplant soil andd ng water). This means that

t soil is a fairly good electric con-uctor. When the soil dries, it

becomes less and less conductive.Figure 1 shows the principle of

The electrical resistance,R, of the soil is measured by a pair ofsharp pointed probes, Ei and E,,which are pushed into the soil. Theresistance is continually monitored bya simple drcuit. When the soil gets(too) dry, this circuit actuates a piezo-electric buzzer, Bz. Since the requiredmoisture varies from plant to plant, apreset, P, is added to set the mini-mum allowable moisture.The reliability of thecircuit depends almostentirely on that of theprobes. Were these tocarry even only a tinydirect current, in themoist conditions inwhich they are used,

1 V5 +

°

Elektor Electronics

El

R

they would soon be subject to rapidoxidation or electrochemical destruc-tion. That is, depending on the direc-tion of the direct -current, one of theprobes would soon be enveloped in afilm of oxide, while the other wouldbe (partly) dissolved. This electrolysisis negated by the use of an alternat-ing current instead of a direct current.

Fig. 2. The circuit isbased on a rectangular -wave generator. Tl-T2,and current -sensitiveswitch T5 -T6. The gen-erator provides the cur-rent with which the con-ductivity of the soil ismeasured, and the cur-rent to actuate thebuzzer.

= UB = 1,5 V2, = 0,7 V

3196

DESIGNSince nobody wantsan unsightly piece ofelectronic hardwaresucking conspicuous-ly into their decora-tive houseplant pots

Fig. 1. The houseplantbuzzer is based on theproperty of moist soilbeing electrically con-ductive. The potentialdeveloped across thesoil resistance R ismeasured via probesEl and E2. If the soil isdry(ish) (R = high), abuzzer sounds.

titi

the design hasbeen aimed atmaking the mon-itor as tiny aspossible. Theresulting. printed -circuit board is onlyslightly larger than the HP7 dry bat-tery that powers it.

The low e.m.f. of an HP7 battery(1.5 V) puts certain restrictions on theelectrical design. pear in mind thatsilicon transistors need about 0.7 V toconduct, which leaves precious littleof the battery voltage for drivingthem. This is, by the way, the reasonthat the circuit -see Fig. 2- is basedon discrete transistors. integrated cir-cuits (Ics) normally :need a highersupply voltage.

1N4148 2xBC550C

Fig. 3. The printed -cir-cuit board for thehouseplant buzzer hasbeen kept as small asfeasible to ensure thatthe finished productdoes not detract fromthe decorativeness ofthe houseplant.

The circuitbased on tran-sistors T1 andT2 forms a rec-tangular -wavegenerator. Thevalues of resis-tors R, and R3and of capaci-tors C1 and C2

ensure that the generator produces arectangular voltage at a frequency ofabout 3 kHz.

The generator fulfils two func-tions: it provides the alternating cur-rent for the probes and the signal foractuating the buzzer.

Current amplifiers T3 and 14 forma load -compensating network for thegenerator.

When the moisture of the rele-vant soil is correct, the generator sig-nal, amplified by T3-14, is applied tothe probes, El and E2, via capacitorC4. This capacitor prevents anydirect voltage from reaching theprobes. The conducting soil betweenthe probes closes the measuring -cur-rent loop, so that this current reach-es electronic switch T5-16. Thisswitch is current -sensitive; when thecurrent is above a certain level, T6 iscut off, so that the buzzer can not beactuated.

When the soil becomes dry, themeasuring current becomes smaller,so that, depending on the setting ofP1, switch T5T6 is enabled. Thismeans that T6 conducts and thebuzzer is actuated to emit a 3 kHztone.

CONSTRUCTIONSince the printed -circuit board (seeFig. 3 ) is small, soldering has to becarried out with great care. The boardis available ready made (see p.70), but

it may also be made in-

the home workshop. lf -

This entails making a1:1 photocopy of thetrack layout on tofilm, transposing thefilm copy on to a (positive -sensitive) PC board, and etching thesuperfluous copper. This requirespatience (lots) and experience(some), but it is not beyond the kenof most electronics enthusiasts.

The ready-made board containssub -boards for four monitors, sincegenerally more than one houseplantneeds monitoring.

Populate the board in stages andcheck the work after completing eachstage.

The work is begun by solderingresistors R1-R3, followed by capaci-tom C1, C. and C6, and then transis-tors T1 and T, in their relevant posi-tions. Note that, to save space, theresistors are mounted upright. Next,solder the battery -holder leads to theboard.

Insert an HP7 battery into theholder. Use a multimeter, set to the2 V d.c. range, and check that thevoltages at the test points indicatedin Fig. 4 (with respect to earth, thatis, the -ye terminal of the battery)are: 0: battery voltage, lib; G., 0, 0:

Ub/2. Ifthe potentials at 2 and 3

(collectors of TI and T2 respectively)are about hall the battery voltage, itmay be assumed that the generatorfunctions correctly. If these potentialsare much smaller than Ub/2, the resis-tors are placed incorrectly or theirvalue is wrong. If the potential ismuch higher than Ub/2, there issomething awry with the transistors(wrongly connected or incorrecttype).

If the potentials are as stated,remove the battery from the holder,solder R5, R6, C3, T3 and 14 into place,

Squeaking crystalsThe piezo-electric effect occurs when certain materials (crystals) are subject-ed to mechanical stress. Electrical polarization is then set up in the crystal,whereupon the faces of the crystal become electrically charged. The polarityof the charge reverses if the compression is changed to tension. Conversely,an electric field applied across the material causes it to contract or expandaccording to the sign of the electric field.The effect is observed in all ferroelectric crystals and in all ferroelectric crys-tals that are asymmetric and have one or more polar axes.The effect is important because it couples electrical and mechanical energyand thus has many applications for electromechanical transducers.Piezoelectric crystals are used to provide frequency standards and in piezo-electric oscillators.Figure (a) shows the principle of a domestic application: a lighter for gas fires.The hammer represents the mechanical force acting on the piezoelectricmaterial. The voltage resulting from the distortion of the material is indicatedby the meter.Figure (b) shows the change of shape of a piezoelectric material when anelectric potential is applied to it. When the electric potential is an alternatingone, produced for instance by the rapid opening and closing of a switch as inFig. (c), the material will vibrate in rhythm with the rate of opening and closingof the switch. If this rate lies in the frequency range 20-20000 Hz. the air dis-placed by the vibrating material will be audible. This is the principle of opera-tion of the buzzer used in the houseplant moisture monitor.

16 Elekior Electronics 3 96

and reinsert thebattery into theholder. With themultimeter set asbefore, check thatthe potential at testpoint 4 (collectors13, T4) is U112.When the multime-ter is momentarilyreplaced by thebuzzer, this shouldemit a 3 kHz tone.If no tone is heard,it may be that itsfrequency is muchtoo low or too high;this may be causedby incorrect valuesof C1,

When all is cor-rect, remove thebattery from theholder, solder theremaining compo-nents into place andconnect the buzzerprovisionally. Setthe multimeter to the 1 mA d.c. rangeand connect it in series with one ofthe battery holder leads. Reinsert thebattery into the holder and check thatthe current drain is 0.1-0.2 mA. If it isappreciably different, check the value

4

"Or

(D=-43

00® 112 us

Fig. 4. Various testpoints on the pcb. Seetext for values at thesepoints.

V50118-14

of all resistors.When all is well,

fix the batters' holder onto the track side of theboard with double -sidedadhesive tape (availablefrom most stationery

and on shops). The advantage of thistape is that the holder can beremoved at a later date if necessary.Fix the back of the buzzer to the bat-tery holder (at the end opposite Ti,T,) with superglue.

The probes consist of 15 cmlengths of 1 mm thick insulated cop-per wire, from each of which 2-3 mminsulation is removed at one end and4 cm at the other end. The 2-3 mmbare ends are soldered to the board.The 4 cm bare ends are tinned to pre-vent any oxidation. Make sure thatthe probes are straight and equidis-tant (12 mm) from each other.

USAGEAfter the battery has been insertedinto the holder, push the monitorupright into the soil. Make sure thatthe bare probe ends are fully in thesoil, but take care that there is suffi-cient space between the board andthe soil to prevent the board gettingwet when the plant is being watered.Alternatively, bend the probes toallow the monitor to hang over therim of the pot on the outside.

Normally, the monitor is pushedinto the soil only near the time whenwatering of the plant is due (a mat-ter of experience). With the probes indry(ish) soil (as relevant to the plant),set P1 to a position where the buzzeris silent, and then adjust it till the

buzzer just operates. Sprinkle wateron to the soil (away from the moni-tor), wait a few minutes for it to getwell into the soil, and check that thebuzzer ceases to work. If necessary,readjust P1 with the probes insertedinto a different pot. el5otts)

Components list

Resistors:

Al. R4 = 221(11R2. R3 = 220 kOAS. R6, R8 = 100 K2R7 = 47R9 = 10 MO.

P1 = 100 kf) preset

Capacitors:C1, C2 = 820 pFC3 = 470 pFC4 = 1 pFC5 = 100 nFC6 = 10 pF, 63 V, radial

Semiconductors:D1 = 1N4148T1-1-3. T5, T6 = BC550CT4 = BC560C

Semiconductors:D1 = piezo-electric buzzer, 1.5 V1 off HP7 (AA, R6) dry battery1 off holder with leads for battery1 mm thick insulated copper wire to -probes (see text)

PCB Order no 950118-1 (p. 70).

Elektor Electronics 3/96 17

FOCUS ON:PC MEMORY CHIPS

By our editorial staff

Close on the heels ofthe processor (CPU),

the memory isone of

themostimpor-

tant corn-ponents in a PC.

Developments in thesoftware industry _-over the last cou-

ple of years havemade massive

amounts of memorynecessary to run an

operating system likeMS -Windows. Today,

there are so many dif-ferent types of mem-ory available that it is

no longer easy toknow exactly which

type to use for a par-ticular application. Anintroductory overviewis therefore presented

in this article.

megabyteson square

14'

SRAMs, DRAMs, EDO RAMS, SIMIVIs,SIPPs ..., there is a such bewilderingnumber of memory options for thecomputer that it is hard to keep themapart and, more importantly, to selectthe right type if you want to extendthe memory in your computer.

In principle, it is all very sim-ple. Currently, two types of memoryare available: static RAM (SRAM) anddynamic RAM (DRAM). RAM standsfor random access memory. In a staticRAM, each memory cell consists of aflipflop (comprising a few semicon-ductors) which is at one of two logicstates, and so capable orremembering'a value. The dynamic RAM has amuch simpler construction: a capacitoris charged or discharged by a field-ef-fect transistor (I -E1) or an ordinarytransistor. The major disadvantage ofthis type of memory is, however, thatthe memory contents has to be re-freshed frequently (every few mil-liseconds) because the charge con-tained in the capacitor disappearsslowly because of leakage. This leak -

18

age is significant because capacitors ina DRAM have a capacitance of lessthan 0.1 pE This problem calls for amore complex type of drive. Be-cause charging and discharging acapacitor takes more time than mak-ing a semiconductor switch on oroff, static memories are much fasterthan dynamic ones. The latestSRAMs boast access times of 10 to20 ns (nanoseconds), while values of60 to 70 ns are common with state-of-the-art DRAMs.

Because of the more com-plex structure of the SRAM, this de-vice is typically larger and more ex-pensive than its dynamic counter-part_ That's why the mass memoriesin today's computers consist mainlyof DRAM. SRAMs are only used forfast intermediate memories (cache).

SECOND -LEVEL CACHESince the introduction of the 80386processor, PC motherboards have acertain amount of fast cache memorythat forms a buffer between the fast

Elektor Electronics 3/96

processor and the much slower (butrelatively expensive) DRAM memory.Cache memory these days comes intwo variants: asynchronous and syn-chronous SRAM. With asynchronousSRAM, the processor has to wait for

- -the- associated data to appear at theoutputs after it applies an address.With synchronous SRAM, au addressis supplied, and then the data also ap-pears after some time. However, theSRAM then immediately sends thedata at the next three locations, with-out actually requiring new addresses.This trick results in faster timing.

The latest in cache memoryis the pipelined burst cache RAM, whichis based on the principle of the syn-chronous SRAM. The pipelined ver-sion however has an extra buffer("latch') at its outputs, which enablesa new address to be supplied whiledata are still being read from the out-puts. This allows access times of be-hveen 4 and 8 ns to be achieved, sothat even the fastest Pentiums canprocess cache memory data withoutwait loops.

SRAMs come in many dif-ferent physical shapes and sizes.Until recently, SRAMs used to behoused in ordinary D1L cases. Nowa-days they are often implemented as

surface -mounted devices (SMDs),and are soldered directly on to theboard. The latest development is thecache module, which is plugged intoa socket on the motherboard. Such amodule simplifies exchanging thecache memory considerablv.

-MILLIONSOF CAPACITORSAs already mentioned, the large usermemory in your PC consists of dy-namic RAMs. During the course ofcomputer history, the capacity ofDRAMs has grown steadily. Way backin 1970, the first 1-Kbit DRAM ap-peared on the market. Today, 256-Mbitchips are being developed and testedin semiconductor laboratories. WithDRAMs, too, the physical appearancehas changed considerably. Whereasthe first computers had lots of memo-ry chips in DIL (dual -in -line) plastic orceramic cases, today's computers con-tain almost exclusively SMDs.

To make changing the memory con-figuration on the motherboard a littleeasier for the user, modules have beendeveloped. These are small printed -cir-cuit boards which contain a number ofmemory chips. Initially, there weretwo types of module: the SIPP and the

SINMI. The difference is easy to see: aSIPP has connecting pins, while aSIMM has connecting copper pads(contact fingers) on the board. Mean-while, SIPPs seem to have died out,and today's PC motherboards allowonly SIMMs to be fitted. SIPP-to-SIMMadaptors are still available, however

Originally, SIPPs and SIMMswere invariably 30 -pin modules.Today, however, an increasing numberof SIMMs is of the 72 -pin type, whichis identified as the 'PS/2 SIMM'. The72 -pin SIMM and its 30 -pin prede-cessor have different memory struc-tures, as will be seen further on inthis article.

MEMORY ORGANISATIONINAPCSince the introduction of the Intel 8086CPU, the bus width of processors hasshown a steady increase. Limiting our-selves to the CPU generations whichare important in this day and age, it isseen that the 80386 and 80486 featurean external bus width of 32 bits, andthe Pentium, one of 64 bits. Add to

Fig. 1. Three differentpackages used formemory !Cs: the goodold DIL case as youprobably know it frommany other !Cs; the30 -pin SIMM and the72 -pin SIMM.

Elektor Electronics 3 96 19 11,,,

,E -bitDRAM

32-bil DRAM

nomillPentium

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311.111F 6EC3514 1t

that the fact that an ordinary SIMMhas a width of eight bits (sometimesnine if a parity bit is available), anda PS/2 SIMM, a width of 32 bits, and

you will have no problems under-standing why a PC motherboardmust contain a certain number ofmemory modules. Such a group of

Fig. 2. The processorbus width also deter-mines the logic width(in bits) of the memoryhanks. This is animportant fact to keepin mind when you startthinking about extend-ing the memory ofyour PC.

modules with a total width equal tothe CPU's external bus width iscalled a bank.

An 80386 or 80486 -basedcomputer has to be fitted with at leastfour SIIvIlvis to allow the full bus widthof 32 bits to be addressed in one oper-ation. If you want to increase thememory of such a PC, that is only pos-sible by adding at least four SIMMs.However, if PS/2 SIMMs are used, it ispossible to work with one module at atime, because the module has a widthof 32 bits. This is illustrated diagram-matically in Fig. 2. With a Pentium, thememory bus width should be 64 bits,so that you are forced to work withmultiples of two PS/2 SIMMs (Pentiummotherboards usually contain 72 -pinmemory slots only)

DRAM TYPESUntil recently, there was just one(generic) type of DRAM for computeruse. The only specification that mat-tered in the choice of this device wasthe access time. This specification is

Memory requirements for PCs have increased dramatical-ly since the arrival of MS -Windows 3.1. and even more sowhen Windows 95 was released. Eight megabytesseems to be the minimum amount of memory a PCshould have to be able to use these operating systemsat all. But memory is expensive, however. and somesoftware houses recognized the market potential of aproduct which enables the amount of memory to beincreased artificially These programs are generallyreferred to as RAM doublers.

How do they work?To begin with, a RAM doubler provides much betterresource management. Useful as that may be withWindows 3.1, it is not normally necessary withWindows 95. Secondly these programs do exactlywhat their (generic) name implies: they increase theamount of memory available. Use it made of the factthat Windows uses a swap file. Basically, that is a file

on the hard disk which is used to store data if it doesnot fit in the user memory any more. Because a harddisk is much slower than a memory, the use of a swapfile tends to slow the computer down. Most RAM dou-bler software compresses data before writing it to thehard disk, so that less space is taken up (the processis similar to the file compression techniques used bypack/unpack programs such as PKZ1P or ARJ). Good!On the down side, however. compressing and decom-pressing data is a software overhead which takes time,and requires a dedicated buffer area to be reserved inthe user memory The net profit is, well, marginal, if weare to believe the test results published in various com-puter magazines. Here, too, the rule is: nothing beatsreal RAMs. None the less, those of you struggling withWindows 3.1 or a small hard disk may like the results ofprograms such as SoftRAM. RAM Doubler orMagnaRAM. Most of these programs may be obtainedat prices of 25 -odd pounds.

20 Elektor Electronics 3 96

usually printed on the device as a suf-fix to the type number. For most 80386and 80486 based machines, 60 ns or70 ns is a good choice. With modernPCs, however, the external bus dockis so high that a couple of waitstates have to be 'thrown in', not foramusement, but to allow data to beprocessed reliably even 4f 60-nsDRAMs are used (which are cur-rently the fastest types around).

Because DRAMs faster than60 ns are still difficult to produce involume quantities, the manufactur-ers have come up with a couple oftricks to make their DRAMs faster, atleast as far as a number of tasks areconcerned. Today's magic word isEDO-RAM. The abbreviation standsfor extended data out. A special out-put register enables data to remainavailable longer at the output of theRAM. This allows a new address tobe supplied while the data with theprevious address is still being read.In practice, this approach offers aspeed increase of between 10 and20 per cent as far as data exchange iconcerned between the CPU andthe memory.

EDO-RAM is normally alittle more expensive than ordinary -DRAM. The price difference is, how-ever, expected to disappear beforelong. The control electronics on themotherboard must be capable of dri-ving EDO-RAM. Consequently, youcan't normally mix EDO-RAM andregular RAM on a PC motherboard.

In spite of its higher (appar-ent) speed, EDO-RAM is no real sub-stitute for a second -level cache. Thelatter remains essential for fast inter-mediate processing of memory data.Meanwhile, our highly esteemedmemory chip manufacturers havecome up with yet other variants likeburst -CAS DRAM, synchronous DRAM,RAMInts DRAM and multitunk DRAM.None of these is, however, ready forwide application in computers.

ABOUT THE PARITYBITSince the introduction of the first IBMPC -XT, all 'compatibles' (clones) haveused a memory which contains a par-ity bit The parity bit is an extra bit thatrepresents the checksum of the othereight bits. It allows the CPU to checkthe integrity of the data contained inthe.memory.

Unfortunately, memory ICscan develop so-called soft errors. Theseerrors are caused by alpha parts from

M1

M2

M37 M4

> BANKO

> BANK1

M1 ,M2(BANKO) M3,M4(BANK1) Total Size

im x 32 (4MB)1M x 32 (4MB)1M x 32 (4MB)1M x 32 (4MB)1M x 32 (4MB)2M x 32 (8MB)2M x 32 (8MB)2M x 32 (8MB)2M x 32 (8MB)2M x 32 (8MB)4M x 32 (16MB)4M x 32 (16MB)4M x 32 (16MB)4M x 32 (16MB)4M x 32 (16MB)8M x 32 (32MB)8M x 32 (32MB)8M x 32 (32MB)8M x 32 (32MB)8M x 32 (32MB)

Empty1M x 32 (4MB)2M x 32 (8MB)4M x 32 (16MB)8M x 32 (32MB)Empty1M x 32 (4MB)2M x 32 (8MB)4M x 32 (16MB)8M x 32 (32MB)Empty1M x 32 (4MB)2M x 32 (8MB)4M x 32 (16MB)8M x 32 (32MB)Empty1M x 32 (4MB)2M x 32 (8MB)4M x 32 (16MB)8M x 32 (32MB)

8MB16MB24MB40MB72MB16MB24MB32MB48MB80MB32MB40MB48MB64MB96MB64MB72MB80MB96MB128MB

Fig. 3. Example of thepossible memoryoptions for a modernPentium -based moth-erboard with four 72 -pin memory connec-tors. The smallestmemory size that canbe fitted is 8 MB, thelargest, 128 MB.

radioactive Kaliumm which is presentinside the IC enclosure. In the meantime, the production of the relevantmaterials is under much stricter con-trol, and the density of the chips hasincreased appreciably. These two factshave reduced the occurrence of a softerror to about once in ten years, as-suming that a modern system is usedin a normal way. The risk of a softerror occurring is considered so smallthat you may reasonably question theneed for a parity bit. Moderns SIMMs,whether 30 or 72 -pin types, may bepurchased with or without a parity bit,or with a simulated one. Incidentally,there are many PC motherboardsaround these days that do not use theparity bit at all. If that is the case, it

960014.12

makes no sense to fit memory mod-ules with a parity hit. In any case, buy-ing memory modules with a parity bitseems unnecessary if you have a fair-ly recent motherboard.

FINALE: SOME PRAC-TICAL THOUGHTSMemories for modern computerscome in many shapes and sizes, giv-ing the user a hard time to select theproper type when it comes to ex-tending the computer's memory.Among the many questions you mayhave to ask yourself are: which typeof module is already fitted in thecomputer? Is it ordinary DRAM orEDO-RAiM? What is the current ca-pacity per module, and how manyconnector locations do i have avail-able? What is the processor buswidth? How many modules must Iinstall at a time? Is a parity bit re-quired?

By taking a few logic deci-sions it should not he too difficult tofind the right memory extension foryour computer


Ato 4iroJw 01 MN A POE

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C Netlist, Parts List & ERC reports.O Hierarchical Design.

C Extensive component/model libraries. Advanced Property Management.O Seamless integration with simulation and

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Non -Linear & Linear Analogue Simulation.

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Multi -Layer and SMT support.

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Shape based gridless power planes.

Output to printers. plotters. Postscript.

Gerber. DXF and clipboard.

Gerber and DXF Import capability.

Write, phone or fax for your free demodisk, or ask about our full evaluation kit.Tel: 01756 753440. Fax: 01756 752857.

53-55 Main St, Grassington. BD23 5AA.

Proteus runs as a 32 bit application under both DOS and Windows (3.1. 95 and NT).Prices start from £470 ex VAT: full system costs £1645 for DOS. £1875 for Windows. Call for upgrade pricingardor information about our budget and educational products. All manufacturers' trademarks acknowledged.


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10.13£0.10£0.10£0.100110

606508D707B07081306177BOX32

(03303.42£140MU)£1.38

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Electrolytic Radial Capacitors16% 25% 63% lath 4501

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2_2 - - 0105 £0.06 £031 22 - - £0.10 £0.10 1.0224.7 - - £0.05 LOOS £039 4.7 -- - £0.10 £11.10 -10 03.05 £0,05 £0.05 £0.05 £0.44 10 - - £0.12 £0.12 £0.5722 £005 £0.05 £0.09 - IRIS 22 - 03.12 £0.13 £0.17 f1.0647 £0.06 £0.06 £111 - £0.98 47 ER10 £0.11 10.16 £0.20 -113D £0.06 £0.09 £011 - - 100 £0.10 110.14 L011 - -220 MIN 03.12 £0.31 - - 220 £0.13 £018 £0.42 - -470 £015 £0.19 £1157- 470 £1521 £024 £0.69 - -!MO 1022 £0_2 -- - - 1000 £033 D140 £1.05 - -IVO £037 £1157 - - - 2.NC° 0352 D164 - - -4701 - £1.11 - - - 4700 10..90 - - -ResistorstIW Carbon film 5% El2 Sevin 10-1014 1010 Exh,10.60 10014W Carbon Film 511 612 Snits 10-10M 1002 Each. £0.95 per 100 'UW Metal "EI% 4 Series 1011-181 LOW Each. £1.72 yet 100 LbEnclosed Presets. Hoa Ven_ IWO - 17.100.15W 1015 EachBaletun /tuna Harz / Vat 1101 - IMO 0.IW £0.11 EdithPOTS kr Shift 25mm Dia 47061-210 Lin or Log 10 42 Ea -13DIL Sockets8 Pin 10.07 It Pin 1111 16 Pin 0115 16146 £0.1520 Pin 1 24 P%-, £0.19 28 Pin 01.22 40 Pin £0.25

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switched -capacitorIn audio engineering

there is oftena require-

ment for a fil-ter that either

passes orblocks cer-

tain frequen-cies or fre-

quency ranges.This require-

ment is met by the fil-ter described in this

article: the type of filterresponse required is

available at the flick ofa switch.

The use of a special fil-ter IC from National

Semiconductor in con-junction with switched

capacitors make theconstruction and align-

ment, even for high-

order configurations,straightforward.

Although the filter isintended primarily for

test and measurement,it may also be used for

signal enhancementand noise suppressionin short-wave receivers

and for experimenta-tion in electronic

music.

Pagargr! by F. timptw

Filter responses:

AF pass band

Filter frequencyTransfer amplificationOutput voltage ripple

Input voltageInput impedanceOutput offsetPower requirement

240 V, 2 W

The filter fulfils th, same function inmeasurement technology as in short-wave receivers: it limits the desired fre-quency band and suppresses noiseoutside that band. It then operates asa band-pass filter. If, however, a bandbelow a certain frequency, say, 50 Hz,has to be suppressed, it functions as ahigh-pass filter. Where high -frequencynoise or whistles must be suppressed,the filter can be made to work as alow-pass type. If a frequency, say50 Hz or 100 Hz, within the pass bandhas to be suppressed, the filter can op-erate as a notch type. All these typesof filter function may prove useful inexperiments in electronic music.

THE FILTER ICThe filter is based on a special filterIC from National Semiconductor.This device contains two second -order filter sections, A and B, whichcan be used separately or in cascade.In either case, they provide a mul-tiplicity of filter configurations.

Oct.

In4 5149

BP LP HP Notch

Power UNIVE SAL LF FiLT

Technical databand-pass, high -Pass, low-pass (24 dB :octave).

octave band-pass (12 dfl'octave), notch

10 Hz - 25 kHz

20 Hz - 20 kHz

1

-0 to +3 dB maximum

5 Vpp (1.76 V rms sine wave) maximum

100 k5.2

250 mV maximum

Each section is designed as a state -variable filter that can function as high-pass, low-pass or band-pass. The greatadvantage of this setup compared witha discrete design is the simplicity of thecircuit and the ease with which the fre-quency can be reset, even at higher -order functions.

The pinout and circuit of the 20 -pinIC are shown in Fig. 1. Pin 4 (17) is theinput of the device. Pins 1 (20) and 2(19) are the low-pass and band-passoutputs respectively. Pin 3 (18) is a fur-ther output which, according to theswitching voltage, provides an all -pass,high-pass or notch characteristic atpins 5 (15-16) and 6 (16). In the presentcircuit it is arranged to provide a high-pass characteristic.

Pin 15 is the analogue -circuit earthto which the non -inverting terminalsof all internal op amps and the refer-ence points of the IC are strapped.

The power supply to analogue anddigital circuits is separate via pins 7,14and 8, 13 respectively.

AA 24 Elektor Electronics 3/96

STATE -VARIABLEFILTERA state -variable filter is based on twointegrators and an inverter If the inte-grator resistors are variable, the filtercan easily be tuned. Unfortunately, itis impossible to build a variable resis-tor into the present IC. Therefore, theswitched -capacitor principle,is used,which provides a variable filter fre-quency, fo, that is dependent on theexternal dock supplied to pin 10 (11).

The equivalence of a resistor andswitched capacitor is shown in Fig. 2.In case of a resistor, the current, I, isdetermined by the applied voltage, U,and the resistance, R. In rase of a ca-pacitor, the capacitance, Cc, fulfils thesame function as the resistance R.

When the switch connects Cs to theinput voltage, U, the capacitor is beingcharged. When the switch position ischanged, the capacitor provides (partof) its charge to the output. Thus, ineach switching period a certain chargeis transferred from input to output.

In this way, an average current, 1,flows that is determined by the inputvoltage, the capacitance of theswitched capacitor and the switchingfrequency, L. Thus, the higher theswitching frequency, the higher thecurrent. This means that a switched ca-pacitor can replace a variable resistor.The linear relation between the switch-ing frequency and the equivalent ad-mittance of the setup is noteworthy.

A small flaw in the setup is that atiny part of the switching signal is pre-sent in the output signal. In case of asinusoidal input signal, the output re-sembles a digitally regenerated sinewave, that is, it looks like a steppedwaveform. The amplitude of the stepsis proportional to the signal voltage.Fortunately, the frequency of the in-terfering voltage is much higher thanthat of the input signal. Thus, it will bevirtually undetectable over a widerange of filter frequencies.

In a practical circuit, integratedcoos switches are used.

Depending on the voltage at pin 12the clock for ICI must be 50-100 timeshigher than the wanted filter frequen-cy, ft,. With +5 V at pin 12, the multi-plication factor is x50. This arrange-ment ensures that the internally gen-erated noise of the filter is a minimum.Moreover, the dock at pin 10 (11) mustnot exceed 1.5 Mhz, which means thatwith a multiplication factor of x100,the upper frequency of the filterwould be limited to 15 kHz. Note thatthe factor x50 must not be taken tooliterally: it has a tolerance of ±-2%; inthe prototype, it was 49.4.

1

Package

Top View

THE FILTERPROPERWith the possible excep-tion of the switched -ca-pacitor principle, thefunction of of the circuitin Fig. 3 is straightforward.

Circuit IC, operates as a bipolarinput buffer that is provided with aninput protection network R1 -D1 -D2.

The voltage drop across R1 is com-pensated by the amplification of IC2,which is set to 1.5 by R3 and R4. Ca-pacitor C2 stabilizes the op amp, sincea 5534 is internally compensated onlyfor amplifications exceeding x3. Theoffset of IC2 is compensated with PI,while its output is taken directly to theinput, pin 4, of 1q.

The low-pass (Le), band-pass (Be)and high-pass (He) outputs of filtersection A of ICl are applied to gangedswitch array Si -S5, which can also se-lect notch filter N andioctave filter 0_With the switches in positions HP, 1..eand BP, the outputs of filter section Aare applied to the input of filter sectionB. That is, the two filter sections arecascaded (fourth order filter) to pro-vide a steeper slope of the responsecurves.

The outputs of filtersection B are applied tooutput buffer IC3b viathe switch array.

Output socket K3 ispreceded by low-passsection, R24 -C22, which,at least at higher val-ues off., suppressesany residual clock 2signal at the output

With the switcharray in position N, anotch filter is con-structed in summingamplifier IC3a from acombination of thehigh-pass and low-pass functions of fil-ter section A in ICI.

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Fig.1. Pinout and cir-cuit of the Type MF10special filter IC. The output of IC3a is

applied to the outputbuffer via the switcharray. The second sec-

tion of ICI is then not used: its inputresistor, R13, is grounded via the switcharray.

The band-pass characteristic of thefilter is relatively narrow. For cases inwhich a wider frequency band isneeded, an octave -filter has been pro-vided. When the switch array is in po-sition o, the high-pass output of filtersection A in ICI is applied to section Bvia the switch array, and then takenfrom the low-pass output (pin 20). Atthe saute time, S1c ensures that thedock to the first section is half that tothe second section. This arrangementprovides an upper limit of the HP char-acteristic which is an octave lower thanthat of the low-pass characteristic, sothat the frequency band between thesetwo points is available at all times.

REMAINDER OFCIRCUITThe output of IC1 has a small offset

voltage which nor-mally does not affectthe operation.

The larger part ofthe circuit enclosed bythe dotted lines is thedock generator, which

Fig. 2. Because of theshift of the chargethrough the frequen-cy -dependent switch,the setup functions asa variable resistor.

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is based onIC4. Althoughthe manufac-turers datasheet of thiscoos device

indicates that it can work up to500 kHz, it operates with reasonablysteep edges to well over 1 Mhz whenit is arranged as an astable. ResistorsR18 and R19, in conjunction with ID5and D6, provide a duty factor of 50%,which is required for optimum opera-tion of lc,. If necessary, the factor canbe trimmed to exactly 50% with P3.

Capacitors C7 -C9 and C74-C2o,which are switched with S6a, and P.,enable three overlapping frequencyranges to be set: 1-10 kHz,10-100 kHz, and 0.1-1 Mhz, corre-sponding to filter frequencies of 20 Hzto 20 kHz.

To ensure troublefree oscillating ofIC4 at high frequencies, the device isswitched between -5 V and +5 V Re-sistors R21 and Itm revert the oscillatorvoltage to rrt_ level referred to ground.

Ril

6 o 2=22 9 ra

K3

The clock is applied to pins 10 and11 of IC1 direct and via Sic.

Half the clock frequency requiredfor filter section A of IC1 when the oc-tave filter function is selected is pro-vided by ICs,,, a bistable connected asbinary counter.

Socket K, has two functions. Instandard operation a frequency metermay be connected to it to aid in settingthe filter frequency which is 1/ of themeasured dock.

In the fourth position of the rangeswitch, IC4 is disabled via the resetinput (SO and isolated from the re-mainder of the circuit by Sob. An ex-ternal dock with known frequency atTM level can then be connected to K2.If the signal is higher than rn., it willbe limited by network RirD3-D4.

The on/off indicator um, 1)7, and itsseries resistor, R23, are connected be-tween the -ve and +ve supply lines toensure symmetrical loading of thepower supply.

The power supply is a traditionaldesign. The specified transformer is

'S7

CLX

51/'

.-05v.

tcs = 74FICT74

short-circuit proof, so that no fuse is re-quired. Because of its small load (about38 mA for the oscillator and LED andaround 13 mA for the filter), it hasample reserves in spite of its low sec-ondary voltage.

The various filter capacitors in thesupply lines ensure that there is nocoupling between the clock and the fil-ter channel.

POPULATING THEBOARDSThe filter is built on three printed -cir-cuit boards that are fitted in a smallmetal enclosure. The filter circuit prop-er, in line with National Semiconduc-tor recommendations, is built on adouble -sided printed -circuit board-see Fig. 4. The upper side contains theanalogue ground plane and serves asscreen. The digital ground is at the un-derside. The upper side also containssome wire bridges made of insulatedcircuit wire. The tc sockets must be fit-ted so that its pins, like the terminals

A26 Elektor Electronics 3/96

of some other components, can be sol-dered at the top as well as at the un-derside of the board

Switches S1 -S5 are contained in aganged push-button array. If thisproves difficult or impossible to obtain,different switches may be used, aslong as they are ganged. Apart from St(octave function), the switches useonly two of the four change -over sec-tions; the other two are grounded tominimize any coupling between dockand filter.

Clock -carrying lines are not pro-: vided as tracks on the boards: they are

made from discrete, single -screencable. The screens should be ground-ed at only one side.

The supply lines are taken from the

power supply to the filter board, andfrom there to the dock generator.

The analogue and digital supplylines are interconnected dose to ICIand decoupled by C3 -C6.

Sockets K1 -K3 are linked to theboards via screened cable. It is advis-able to isolate K, and K3 from the en-closure: their ground is then connect-ed to the relevant earthing point viathe screen of the cable. Socket K1,however, is a normal BNC type whoseshell is connected directly to the en-closure: this is the only place wherethe circuit earth is connected to the en-closure.

Components R24 and are nothoused on the boar& they are sol-dered directly to the output socket.

Populate the board in the usualorder, starting with the wire bridges,followed by diodes and resistors, andthen the larger components. Makesure that none of the componentsmakes contact with the earth plane.

FITTING THE BOARDSThe filter board is fixed at the front onto the ganged switch array and at therear to the enclosure via two spacers.Figure 5 shows the layout of the pro-totype.

Fine clock frequency control P2 is a10 -turn potentiometer that is screwedon to the board and connected to therelevant tracks via two lengths of flex-ible. insulated circuit wire. A standard

Aliasing: cause and preventionWhen an analogue signal is being sampled, the the samplingfrequency, fcik, must be at least twice the signal frequency, fs.If this is not the case, Shannon's theorem predicts that infor-mation will get lost. If the sampling frequency is lower thanthe sional frequency a signal f5, is retrieved from the sam-pled information that differs from the original input signal(Nyquist criterion). The retrieved signal-the alias signal-has a frequency that corresponds to the harmonics of thehigh -frequency components of fs.In Fig. A, the upper sinusoidal signal is sampled correctlysince fcik = 81.The signal beneath it is sampled at 2f,. which meets theNyquist criterion, but falls foul of Shannon's theorem. Theoriginal signal is then sampled correctly only if this is done atamplitudes well above zero; if sampling takes place at thezero crossing. most. if not all, of the information would belost.The third signal is sampled at 1.3f,, so that. in accordancewith Nyquist's criterion, the data of the original signal arelost. The retrieved signal has a frequency that is lower thanfs/2.Even when the requirement fc!k?.. 2f, is met, aliasing compo-nents fell; f5 and fck -fs may cause problems as shown inFig. B. This is because. although the higher alias compo-nents are well away from the usable (Nyquist) bandwidth,0-icik12, the lower ones may come dangerously close. When1,10:12f,. they may even fall within the Nyquist bandwidth.The foregoing could lead to the assumption that there are noabasing problems when the MF10 is used, since the sam-pling frequency (clock) is 50f, or even 100f, (where is is thefilter frequency). However, if the input signal is not limited tothe Nyquist bandwidth, it is possible in applications with ahigh upper pass band-high-pass, notch, band-stop-thataliasing components are present in the output signal, eventhough the clock is much higher than the filter frequency.Aliasing effects are relatively easily prevented by limiting theinput signal to the Nyquist bandwidth with the aid of a suit-able low-pass filter before sampling is carried out (Fig. C).The limiting frequency should be as low as feasible. A suit-able value is fs, but if there are wanted signal componentsin the range fs fctki2, it must be appropriately higher. Thelower alias components then have a limiting frequency offcikThe slope is determined by the wanted attenuation of thealiasing components in the range 0-fs The attenuationresults from the dynamic range. D, of the output signal.

Elektor Electronics 3 96 27

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Fig. 4. The double -sided PCB must becut into three beforeany work is done on it.

Fig. 5. General view ofthe prototype filterwith top coverremoved.

potentiometer is less expensive, but, toensure that high frequencies can be setreadily within the relevant range, itshould have a negative logarithmiccharacteristic.

Parts listResistors:RI. R3 = 33 kll132, R4 = 68 kaR5 = 22 MIR64116 = 22.1 Mel, 1%R17, R23, Ra4 = 1 IcaR18, R19 = 470 1/R20= 100 1(0R21, R = 220 11P, = 100 id2 presetP2 = 10 ka 10 -turn potentiometerP3 = 20 10.2 mulliturn preset

Capacitors:C1 = 2.2 pF, polypropylene,

pitch 5 mmC2 = 22 pF, 160 V. polyesterC3. CS = 47 pF, 25 V. verticalC4, C6. Cl% C13, C17. C,8. C20, C2,

100 nF, ceramicC7 = 47 nFCa. Cn = 4.7 nFC9 = 470 pF. 160 V. polyesterC,0, Cl/ = 470 pF. 25 V. vertical

C23 = 10 pF. 63 V, verticalCi, = 10 nFC,.; = a3 nFC2.1 = 3.3 nFC26 = 100 pF trimmerC27. C38 = 100 pF, 10 V. vertical

Inductors:= 47 pF

Semiconductors.D. D6 = 1N41400- = LED, red, 3 mm or 5 mm

Integrated circuits:ICI = f.IF1OCCN (National Semicon-

ductor)IC2 = NE5534IC; = NE5532ICS = TLC555ICS = 74HCT74IC6 = 7805IC7 = 7905MiscellaneousK1 -K3 = socket for board

mountingK4 = 2 -way terminal block for board

mounting, pitch 7.5 mm5,-S5 = 5 -way ganged push-button

switch arrayS6 = rotary switch. 2 pole, 6 posi-

tion for boardmounting

8; = rectifier 880C1500. roundTr, = mains transformer. 2x9 V

secondary, 3.3 VA

Rotaryswitch S6 is sol-dered directlyon to the board.

The supplyboard is fittednext to the oscil-lator board onfour 10 mmlong spacers.The mainson/off switch isfitted on to therear panel.

ALIGNMENTWhen the boards have been populat-ed, do not yet insert the tcs into theirsockets. Set PI and P3 to the centre oftheir travel, switch on the mains (theon/off indicator LED forms the basicload for the power supply) and checkthat the supply voltages at variouspoints are correct Switch off the mainsand insert the tcs into their socket.

Check that the clock generatorfunctions correctly: ranges 1-10 kHzand 10-100 kHz should present no dif-ficulties. With an oscilloscope and 10:1probe, check the wave form and dutyfactor. If necessary, adjust P3 until thefactor is exactly 50%. This setting mustbe carried out before the final check ofthe end of the range, which is carriedout with a frequency meter connectedto K-).

Next, align the 0.1-1 Mhz range inthe same way as the other ranges,which, owing to the trimmer, shouldpresent no difficulties. The frequencyat pin 5 of IC5 should be half that at

Apart from compensating the offsetof IC2, there are no alignments on thefilter board. The offset voltage of 1C,,measured between pin 6 and ground,is set to zero with P1.

Input a signal of exactly 1 kHz andset the filter function to NOTCH. Set S6,to position 2, adjust P7 until the outputvoltage is a minimum, and measurethe dock at 1(,. The measured value isthe clock factor. Since finding the min-imum output voltage is tedious, it isadvisable to repeat the adjustment andmeasurement a couple of times to geta good average.

Figure 6 shows the frequency re -

St

sponse curves of the individual filtertypes. These curves have been nor-malized and are obtained with theminimum deviation from f0 in allcases. &cow!

Fig. 6. Normalizedtransfer functions ofthe MF10.

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P&P 35.00 (Eu). P&P 60.00 (Eton-Eu)Prig without PCB and 1751:___398.00Indetidual parts for this mum available.but Qty. 10+ only. Prices on request

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Megaprom II EPROM ProgrammerA low cost programmer that handles EPROMS, EEPROMS, Flash EPROMS andPC BUS (24LC65 etc)

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LM 31.55Micro Engine Board Ideal for MCS8031[51 & 87C751 software development.The board can be used as a stand alone controller. Supplied with EditorAssembler circuit and chip information LM 27.00

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The Radio DataSystem (RDS) is

now well estab-lished among VHF-

FM broadcastersaiming at providing

additional informationwith their radio pro-

grammes. In additionto up-to-date traffic

information, RDS alsobrings you, on an LCDscreen, alternative fre-

quencies, time infor-mation and a feature

compactdecoder

RadioData Systemreo radio

for any Ffiti ste

tlif iC°called Radiotext. The ;In P°Clatter in particular

is on the rise

"0110

days, withContinuous

displayof station

name,time

andradiotext

offeringlistenersregulator.hometionalthis

in-,,, i Alignment

-freedemodulator

their cars.A PIC16C84 micro -

controller allows asimple and pretty

compact RDS add-ondecoder to be builtbased on only twointegrated circuits.

Design by U. Nagel

Apartfrom the traffic -re-

lated functions aimed at the carradio market, other RDS functionssuch as transmitter identification, timeand radiotext are of great interest toowners of home based FM radios.The RDS decoder presented here wasdeveloped to function as a simple ex-tension to any (we hope) domesticFM stereo receiver. The circuit dis-plays the station name, time (withatomic accuracy from some transmit-ters) and radiotext on a 2x16 or 1 x40character liquid screen display (LCD).The printed circuit board for this

pro-ject is compact

at just &4x.4-4 mm, andmatches the size of a 2x16 -char-acter LCD unit.

THE CIRCUITRDS processor IC1 Contains' every-thing you need to demodulate theRDS data signal taken from an FM re-ceiver. We are talking about theTDA7330 from SGS-Thomson, a chipthat contains RDS subcarrier filters aswell as a dedicated demodulator. Thefilter is alignment -free thanks to aquartz -controlled switched -capacitornetwork. Obviously, the total absenceof adjustment points on the RDS de-modulator chip is a great help in keep-ing the construction of the RDS de -

A32 Elektor Electronicc, 3/96

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coder as simple as possible.A supply voltage of 5V is required

to power the RDS decoder The de-coder supplies the familiar set of RDSoutput signals: RDS CLOCK (pin 12),RDS DATA (pin 13), RDS QUALITY(pin 14) and ARI (Autofahrer Radio In-formation, for Germany only) (pin 15).The TDA7330 may be used with a4.332 -MHz or an 8.664 -MHz quartzcrystal. The first option is selected byleaving pin 18 open -circuited, the lat-ter, by strapping pin 18 to +5 V Here,an oscillator frequency of 4.332 -MHzis used, which doubles as the clock forthe PIC, allowing this device to workwithout its on -chip oscillator.Design information on the TDA7330is given on the Elektor ElectronicsDatasheet elsewhere in this issue.The input of the demodulator chipis supplied with the multiplex(MPX) signal, which is 'stolen' fromthe input of the stereo decoder inthe FM receiver. Only two of thepreviously mentioned RDS outputsare used here, namely the RDS datasignal (RDDA, pin 13) and the asso-ciated clock (RDCL, pin 12). Theclock frequency equals 57,000/28 Hz,i.e., 1187.5 Hz. It is used to producean interrupt at processor pin RBO. Inthe interrupt routine, the processorreads the data signal at its RTTC pin(pin 3 of the PIC).The liquid crystal display (LCD) isoperated in four -bit mode, in which

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only D4 through D7 areused. Data lines DO, DI, D2and D3 are, therefore, notused. RB1, RB2 and RB3 are the con-trol signals for the display.Jumper JP1 selects the 1CD type used:JP1 open = 2 x16 characters; JP1dosed = 1 x40 -characters. The contraston the LCD is adjusted with preset Pl.Voltage regulator IC3 allows the de-coder to be powered from a supplyvoltage higher than 5 V, which may beavailable in the FM receiver. Currentconsumption of the decoder is small-er than 15 mA. Diode Dl acts as asupply reversal protection, and atthe same time creates a an auxiliarybias of -11.7 V which is applied tothe lower terminal of preset P1. Theuse of a (small) negative voltage en-sures that older LCDs, too, can bemade to produce sufficient contrast.Because the PIC processor combineseverything that belongs in a com-puter on a single chip, it emits onlylow interference levels, reducing themain sources of noise to the LCDconnections, which should be keptas short as possible. Actually, that iswhy the LCD is fitted directly on tothe decoder board.

0CC

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IC socket. The display is se-cured at the solder side of theboard with the aid of shortwires or header/socket con-nections, so that the soldersides face one another. Al-though the noise emission ofthe decoder/display unit willbe low, it does no harm to fitthe project in a screenedmetal enclosure. In mostcases, however, an all -plasticcase will be equally suitable.The board has a cinch socketvia which the multiplex signalis applied. Before taking theRDS decoder into use, youshould make sure the board iscorrectly populated. Alsocheck the use of the jumper(see above). For an initial test,power the decoder from a di-

rect voltagesource supplyinganything be-tween 9 andabout 12 V forexample, yourbenchtop regu-lated d.c. powersupply. You will

a1,0 need a properly working FMradio with 'line' outputs. This may bean FM stereo tuner or a mono radiowith a tape recorder output. Withmost high -end FM stereo tuners, themultiplex signal is suppressed to theextent that the RDS decoder will notbe able to detect even the smallesttrace of it at the receiver's line out-puts. On most down-market FM ra-dios, however, as well as on manymono receivers with a line (taperecorder) output, it is definitelyworth trying the audio outputs! Withstereo tuners, it makes no differencewhether you use the left or right lineoutput. It is, however, essential tohave the receiver tuned to a strongsignal from a station of which you arecertain it transmits RDS.

On being switched on, th% RDSdecoder produces an identificationwhich remains on the LCD until avalid RDS signal is detected andprocessed. The identification may beused to adjust the LCD contrast.

Once a valid multiplex signal is re-ceived at the input of the decoder, thedisplay shows the station name, forexample, BBC R1, almost immediatelyafter the power -on ident has disap-peared. After a further minute or so,the time also appears on the display,next to the station ident. When you

Forgetting about thevoltage regulator forthe moment, an RDSdecoder can be builtfrom just a demodula-tor IC, a programmedPIC and a standardLCD module

CONSTRUCTION ANDCONNECTIONThe single -sided printed circuit boardis simple to populate. If you go forminimum cost, give at least the PIC an


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Track layout and com-ponent overlay of thesingle -sided printedcircuit board (avail-able ready-made, seepage 70).

Components List

Resistors:RI = 2Mt-22R2 = 1 k.Q.R3 =22k0R4 = 41427P1 = 10k.O. preset

Capacitors:C1.C2.C3,C10 = 100nFC4 = 47nFC5 = 10uF 25VC7.C8 = 27pFC9 = 100uF 25VC6 = lOnF

Inductor:LI = 100uH choke

Semiconductors:D1 = 1N4002ICI = TDA7330 (SOS -Thomson)IC2 = PIC16C84 (programmed.

order code 966505-1)IC3 = 78L05

Miscellaneous:K1 = PCB -mount cinch socketK2 = LCD. 2x16 or 1x40 characters.

Preferred type: Sharp LM16A21(2x16)

K3 = 2 -way PCB terminal block.5mm raster.

X1 = 4.332 -MHz quartz crystalPrinted circuit board and pro-

grammed PIC for this project: ordercode 960050-C (see page 70)

are receiving a traffic information sta-tion, the display shows a (dash) atthe far right. This changes to a '' whentraffic information is transmitted.

The lower display line shows theradiotext (if available), which scrolls.Up to two messages of 64 charactersmay be transmitted. These arejoined to give one 128 -character text,which is displayed sequentially.

If you are unable to achieve us-able results from the receiver's lineoutput(s), there is no alternative butto locate the MPX signal inside thetuner, at the input of the stereo de-coder. As shown by the block dia-gram of a typical FM tuner, Fig. 5,this point is found near the FM de-modulator, where the demodulatedFM multiplex signal 'before de -em-phasis' is available. The actual pointto tap is easily found using the re-ceiver's service documentationand/or your oscilloscope. If haveneither of these, it is also possible tofind the MPX signal by trial anderror. Starting from the receiver'scinch output sockets, trace the wiresor PCB tracks that lead to the stereodecoder IC. Once you have locatedthis IC, the first thing to do is makesure your are tuned to a station ofwhich you are certain it transmitsRDS. Next, carefully touch each ofthe decoder IC pins with a probeconnected to the RDS decoderinput. Because of the processingtime needed by the RDS demodula-tor, you may have to keep the probe

connected at least 30 seconds toeach pin before data starts to appearon the display. Once the right pin isfound, the station name is displayedafter a short while, followed by ra-diotext (if transmitted).

Having found the proper signalfor the decoder's MPX input, theunit may be installed and wired per-manently, either inside the receiver,or as a set -top extension. If youchoose to fit the decoder in the re-ceiver case, you will need to locate asuitable take -off point for the 9-Vsupply voltage. Hopefully, that is nottoo difficult to find in the receiver.The signal connection between thetuner and the decoder is best madein thin screened cable. If the supplyvoltage is also taken from the receiv-er, the cable screening may be con-nected to ground at one side only:the receiver side! This is necessarybecause of the polarity reversal pro-tection diode, DI, which would oth-erwise be shorted out, causing lowercontrast on the display.

TEST VALUES ANDTROUBLESHOOTINGThe circuit diagram, Fig. 1, gives youa number of d.c. test values as wellas points at which active signals canbe measured. The relevant signals,measured on our prototype, areshown in Fig. 3.

While measuring the direct volt-ages in the circuit, you should notethat pin marked '0' on K3 does notrepresent ground. This is actuallyat - 0.7 V because of diode Dl(whose anode is at ground poten-tial). For measurement purposes,ground may be taken from, for ex-ample, the negative terminal of C9,or the cable screening terminal ofthe cinch socket. In addition to theoperating voltage (5 V) and the ref-erence voltage (approx. 2.2 V atpin 2) you may also want to mea-sure the logic levels at pins 14(RDQ) and 15 (ARI) using a digitalmultimeter. RDQ (designated QUALin the datasheets) indicates the qual-ity of the received RDS signal. Thispin supplies a logic high level whenan RDS signal of sufficient quality isreceived. RDQ is low when the RDSinput signal is too small, or missing.The ARI pin goes high when an ARIsignal is being received, and lowwhen only an RDS signal is avail-able. The level of the ARI pin in un-determined when neither RDS norARI is being received. In the UK, the

A34Elektor Electronics 3/96

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Signals at the measuringpoints indicated in the circuitdiagram:(a) stereo multiplex signal;(b) filtered 57 -kHz signal;(c) ADS data signal (uppertrace) and recovered 1187.5 -Hzbit clock signal (lower trace);(d) 4.332 -MHz oscillator signal.

AM system is not used.The signals at the other measuring

points, A through D, are shown inFig. 3: the multiplex signal (Fig. 3a),the filtered 57 -kHz signal with RDSand ARI (Fig. 3b), the recovered bitclock and data signals (Fig 3c) and, fi-nally, the oscillator signal (Fig. 3d).The levels supplied by pin 14(RDQ/QUAL) and pin 15 (ARI) areeasily evaluated with a multimeterto give a go/no-go verdict on the op-eration of the RDS demodulatorchip. If the levels measured do notmake sense, you may have hit upona station that does not transmit RDS.If you are sure, however, that youare tuned to the right station, then alow level at the RDS output (andpossibly at ARI also) indicates thatthe tuner either does not supply anMPX signal (wrong internal connec-tion), or the MPX signal is too small.The latter is unlikely, however, be-cause the TDA7330 boasts a sensitiv-ity of 1 mV for RDS signals and 3 mVfor ARI signals (see datasheet ex-

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Fully populated proto-type board. The LCdisplay may beplugged in at the sol-der side of thedecoder board. Thatresults in a compactRDS decoder modulewhich is eminentlysuited to installing inan existing FM tuner.

tracts elsewhere in this issue). With-out the help of an oscilloscope, youmay have to solve this problem bytrying out another receiver, or find-ing another point in the receiver to

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tap the unfiltered MPX signal.When 1C1 reports an RDS signal

(pin 14 goes high), the LC displayshould at least indicate the stationname after a few seconds. If thepower -on message does not appearat all, the first thing to check is theLCD contrast setting. If another dis-play is used than the one mentionedin the parts list, it could just be thatthe connections are turned 180 de-grees (this is the case particularlywith older LCD models). When thedisplay does not show a dark line at

Elektor Electronics 3/96 35L

any setting of P1, and with all ICsremoved from the decoder, youshould simply try to reverse all con-nections by 180'.

When the display works all right,and the TDA7330 reports RDS re-ception at pin 14, the only remain-ing source of troublo.is really the os-cillator. The oscillator signal at pin 16may be checked with an oscillo-scope, just like the signals at pin 3(RDS data) and pin 6 (RDS bitclock). Assuming that these signalsare okay, and the display is workingand connected the right wayaround, it is time for a thoroughcheck on all solder joints and I'CBtracks around the PIC on the board.If you can't find an error, the PIC

RADIO DATA SYSTEM

/AntennaStereo

decoder

FM tuner FM ewe!(front end) amplifierI-,IF demodulator .-MPI

RDSdemodulator

Like any stereo decoder, the RDSdemodulatoridecoder has to he sup-plied with the stereo MPX (multiplex)signal, which is available at the outputof the receiver's FM demodulator.

may be damaged electrically, whichmay be ascertained by exchangingthe device_ Although it rarely hap-pens in practice, it can not be ruledout that the CMOS controller hasbecome the victim of a static dis-charge or overheating. mom)

Radio Data System (RDS) infor-mation has been transmitted bymany VHF -FM radio stationssince 1988. RDS signals areconveyed at a subcarrier fre-quency of 57 kHz This fre-

furdtenirnies

quency is phase -locked to the pilot carrier of 19 kHz(3x 19 kHz = 57 kHz). Figure 1 shows the theoretical fre-quency spectrum of the multiplex signal as transmitted bya VHF -FM radio station broadcasting RDS. RDS data ismodulated using a technique known as double-sidebandsuppressed carrier (DSSC), which results in two clearlyvisible sidebands whose bandwidth is roughly equal tothe binary RDS data rate of 1187.5 bits per second(baud). The bit clock is recovered from the subcarrier bydividing it by 48. That also explains why a frequency of1187.5 Hz is available at the clock output (RDCL, pin 12)of the RDS demodulator IC TDA7330. provided, ofcourse, a valid RDS signal is being received.

Basically, the RDS signal consists of binary data whichare transmitted serially. This data is organized inblocks of 26 bits each. Each block contains a 16 -bitdataword and a 10 -bit checkword (Fig. 2a). The highredundancy of the checkword affords security of thedata even under very adverse receiving conditionssuch as in a moving car. Four 26 -bit blocks togetherform a 104 -bit group. In a group, the blocks are sim-ply identified by their order, i.e., Block 1 throughBlock 4 (Fig. 2b). Blocks and groups are transmittedcontinuously, so that the transmission time per groupequals 87.5 ms at the above mentioned baudrate.Each RDS group is of a certain type. RDS supports 15group types. The following information is contained inall groups: programme identification (PI), programmetype (PTY) and traffic (TP). The rest of the informationconveyed in the group is variable, and depends on thegroup type.The information type list is long, and extends fromdata/clock info (Type 4 Group), through internal infor-mation on the radio station (Type 6 Group), right up toa transparent data channel (TDC, Type 5 Group)which is intended to convey small computer pro -

91007J -12a

For further reading:Radio Data System (RDS) decoder.'Fickler Elaironics May 1989.

Radio Data Systems, Valor Elearnnics'July -August 1991.Radio Data System (RDS) decoder, ElektorElectronics February 1991.RDS demodulator with integrated filter,Elekior Electronics October 1991Radio Data System (RDS) decoder. EielaitrElectronics May 1993. -

Radio Data System (RDS) decoder, EteidorEta -ironies January 1994.

grams or even GPS correction data.The Radiotext (RT) as displayed by the present decoderis contained in type -2 groups, and consists of up to64 characters which supply any information the broad-casters feel free to throw at you, usually related to thecurrently transmitted programme. RT supports spaces,enabling the text to be easily read from a 2x32 display.In principle, it is also possible to transmit texts of any lengthin successive lines (64 -character chunks). In practice,however, that is rarely done. Apart from the low transmis-sion rate that can be achieved (no more than about20 characters per second, provided every alternategroup contains RT), the main objection against usinglong texts is probably that the broadcasters are painfullyaware of the relatively low number of people who arewilling and able to receive and read radiotext. Hopefully,that situation changes for the better following the publi-cation of this article.

Bt

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36 Elektor Electronics 3/96

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/pi/ rr r,` :-.\\V

pART 1

PC soundcaas

An ordinary PC with a16 -bit sound card is

turned into an excellentaudio -frequency mea-

suring system, at a verysmall outlay, just by

running some cleversoftware. Applications

of the PC -controlled AFanalyser include mea-suring frequency and

phase response ofamplifiers, filters and, inparticular, loudspeakercross-overs. But that's

not all because theanalyser also enablesyou to determine the

impedance of loud-speakers, the induc-tance of coils, or the

capacitance of capaci-tors. A noticeable fea-ture of the analyser is

its wide measuringrange, for instance,

from 50/tH to 100pHfor inductors, and

100 EDF to 100,000pFfor capacitors.

Software by Dr. M. Ohsmann

arentar3 1171211T

Dora- Sc.)A: <al na

Ct> .143v

<,a = sD.00 =um4..s1

flayts C.r)

3.0 1.0 2.0 3.0 1.0 2.0

PHILIPS

CitratiPititaiisoftware

1E0 . 00

133 .120 -

9J.00

check out those

amplifiersand filters

Justthink of it: a state-of-the-

art sound card like the Soundblaster16 VE will set you back less than70 pounds, yet it contains, amongothers, a stereo 16 -bit analogue -to -digital converter (ADC) for -1-1-kFlzsampling, as well as an FM synthe-sizer chip capable of generatingcomplex waveforms. No wonderyou may want to make all this high-tech stuff do a bit more than pro-duce PC game noises of the whi=-bang class. One such 'serious' appli-cation which is of special interest toelectronics engineers and hobbyistsalike is the versatile AF analyser sta-

Liondescribed in this two-

part article. This first part deals withthe main possibilities of the mea-surement system, while nextmonth's second and final part tack-les the operation of the software de-veloped for the project. It will alsodiscuss a small add-on box for mea-surements. The box contains a cou-ple of resistors and switches, andturns the PC in a multi -purpose im-pedance measuring station.

FOR EXAMPLETo begin with, the main technical fea-tures of the analyser system will bediscussed by means of a couple of ex-amples.

Frequency response of an amplifierThe graph in Fig. 1 is the result of ameasurement performed on theaudio power amplifier in a low-costcar radio. A non -reactive load wadriven. The frequency response wasrecorded over a range from 20 Hz to20 kHz. It is seen that frequenciesaround 100 Hz get an extra 'boost'The 'bass' control was turned up forthis measurement. Clearly, the fre-quency response starts to drop atabout 5 kHz. The phase response isnot very linear either.

Impedance graph of a loudspeakerThe results of an impedance mea-surement on a loudspeaker systemare shown by the graphs in Fig. 2.The measurement was performedon a co -axial drive unit (i.e., onewith the tweeter located centrally inthe woofer/midrange speaker)which was claimed to have a nomi-nal impedance of 4 Q over the fre-quency range from 20 Hz to 20 kHz.The graph shows the real part (re-sistance) and the imaginary part (re-actance) of the loudspeaker's com-plex impedance. The marker is set at122 Hz, where the first self -reso-nance of the drive unit occurs.Where the real part goes through amaximum of about 20 Q, the imagi-nary part shows a zero crossing. Thesecond self -resonance point occursat about 5 kHz, where the imped-ance rises to nearly 7 O. As you cansee, the measurement system is ca-pable of capturing all essential de-tails of an impedance response.

Inductance measurement on an RFchokeFigure 3 shows that the value of anRF choke rated at 40 pH can still bemeasured with confidence. Obvious-ly, such a measurement calls for thehighest frequencies the analyser is ca.pable of producing. In the example,the measurement was carried outover a frequency range from 5 kHz to20 kHz. The measured inductance(approx. 40pH) is shown in the toppart of the illustration. The lower partshows the resistance of the choke.which amounts to about 1 Q (atmeasurement error of about 100 mil).You guessed it the AF analyser is anexcellent help when you have towind RF coils yourself. But low -fre-quency coils, too, can be measuredwithout problems, for example, thosein loudspeaker filters which have val-ues in the milli -henry range.

2

frahuaneu STMT <r> 20.00 111 SOOP tpl 20.00210Config to> .1 Sueeo -.Log Points <1>. 20.0 Zrof C27. 10.00 OhnA: <s> -u Mln <n> -so.00dn Max (A) . 0.004B Auto 

<t> .PMIu Min .-180.00 0 Max <8> .1260.00 . Auto Cu>

(h) : disallow he10-oh8e C.> : exit orosran

0.170:721

-6.25d911,1.44-

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-10.7sen

-23.0010

-21.2520

-37.5023

-43.72eS

-50.00,13

2 0

Marker 123.17 XX

5.0 1.0 2 0

II

1260.00 .

1030.00 .

900.00

720.00 .

540-00 .

360.00 .

100.00 .

0.00 .

-120.00

3.0 1.0 20 5.0 10 20

suu -1.0140 B:PHIv --140.43

Fig. 1. Results of a phase frequen-cy response measurement on alow-cost car radio AF amplifier.

fresuencs ItPAT Cr) 20.00 1.2 :TO Co) 20.COML.Cenflp Cc) .1 Sweep Cu) .Los Points (1). 100.0 Zref <x>. 10.00 ChnA: <s> .2 Min <a> - -20.00 Ohn Max (A) a 20.00 Ohn Auto 

<t> .M Min . -20.00 Ohn Max <0> . 20.00 Chn Auto <y>

Ch) d1nnlahi halo -peso <.> :

20.00 On.,

15.00 Ohs

10.00 Chn

5.00 0214

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-10.00 Ohn

-15.00 On

-20.00 Ohm

exit orosran

1:17.1

3.0 5.0 1 0 2.0 5.0 1.0 2 0 5 0 1 0 2.0

Marker 122.72 HZ A:R - 19.82 Ohn B:X

20.00 Ohn

15.00 Ohn

10.00 Chn

5.00 Chn

0.00003.0

-10.00 Ohn

-15.00 Ohn

-20.00 Oh,

1.45 Of..

Fig. 2. Measured impedanceresponse of a loudspeaker driveunit.

frestueney STMT <r> 100.00 MX :TOP (F) 20.00210Conti:5 (a> .1 SLOOP <u) 'Lag Points (t). 20.0 Zref <2>. 10.00 01-44A: <s> .Ls Min (al 0.00014 Max <A) - 100.00,4) Auto 0: <t> -Rs Min 0.130001.4 Max 10.00 Chh Auto <o>

<h> 01solos help -ease

100.00.3)

87.50.0

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1' 311

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10.00 Ohn

2.75 Ohn

7.50 Ohm

6.25 Ohn

3.00 Clot

3.75 Chn

2.00 On.,

1.25 Choi

0.000Dhn

A:Ls - 45.31o1i a:Ft - 953 .57nOhn

Fig. 3. Even a 40 -pH RF chokecan be checked out.

Dokter Electronics

MEASUREMENTOPTIONS OFAF ANALYSE!?Frequency response (level and phase) of

.. amplifiers-*: filters- - loudspeaker cross -over filters

control loops

Impedance measurement on two -poles-A- loudspeaker parameters

filter inductors(electrolytic) capacitorsresistorsinput/output impedance of filters

- inductors, even smaller than 5011H

1111111111411114 PCREQUIREMENTSFORAF ANALYSERPC:

Sound card:

Software:

486DX-80 with VGA colourgraphics16 -bit SoundBlaster VE(Creative Labs)AF -Analyser program (DOS).published by ElektorElectronics

MAIM TECHNICALDATA1-:-7 Frequency range 15 Hz to 20 kHz

Freely selectable start/stop frequencySweep: logarithmic or linear, up to 1,000measurement pointsMarker function for accurate indicationof measured valuesOn-line help functionReadout in dB. degrees, F, H (auto -ranging)16 bit theoretical resolution

- - Measures gain, phase and frequencyresponse

- ImpedanceR: 1 U. to 1 MUC: 100 pF to 0.1 FL: 50 to 0.1 H

- - Measures equivalents of two -polesRI IC, RI IL. R+L and R+C

SOUNDBLASTER.CO NIP _1 TIBLE & CO.The measurement software was writ-

ten for a SoundBlaster 16 VE from

Creative Labs. This card features 44 -

kHz I6 -bit stereo sound sampling.The software should also run on100% SoundBlaster compatiblecards, preferably those with the Cre-

ative Labs chip set. Regrettably,many low-cost clones use a differentchip set, so you are well advised tobuy the original SoundBlaster. At acurrent street price of 70 -oddpounds, the SoundBlaster 16 VE is agood investment, and should not`blast' too large a hole in your hobbybudget!

The sofhvare, called AF -ANALYSER,

is available on diskette through ourReaders Service (see page 70). AF -ANALYSER (AFA.EXE) is simple toinstall. Once you have verified thatthe diskette you received from us isokay, you start by copying all files

on the diskette into a suitably namedsubdirectory on the hard disk. Next,make sure that the SoundBlastercard is properly configured (address,DMA channel and interrupt - seethe READNIE.TX'T file).

Start the program from hard diskby typing AFA. It will first attemptto address the sound card. If thatfails, an error report is produced.Very likely, your sound card is thenimproperly configured. Next, theprogram attempts to secure addi-tional DMA compatible memory of-fered by the operating system. Ifthat fails as well, another error re-port is produced. In some cases, youmay have to modify your memoryset-up. The author uses the analysersystem without problems on an 80-MHz 486DX with 4 Ivlbvtes RAM.

Once the initialisation is finished, apicture appears on the monitor, andyou are ready to start your firstmeasurement. Incidentally, the soft-ware alters the settings of the mixerparameters used on the sound card.The next important point to con-centrate on is the wiring betweenthe SoundBlaster card and the mea-sured circuit. The connector pinoutsand signal functions are shown inFig. 4. For an initial test, connect theSIGN. -OUT (signal output) socket toa loudspeaker, and start a sweep bypressing the 'x' key on the key-board. The loudspeaker will pro-duce a signal whose frequency rises.

The measurement system generatesits test signals with the aid of theFM sound synthesizer chip on thesound card. The audio power am-plifier, which is also contained onthe card, allows a peak -to -peak sig-nal level of about 750 mV' to beachieved across a load impedance of8 Q. In other words, the system issuitable for running checks on loud-speakers at low power levels. Thefact that you do not know the ab-solute level of the signal applieddoes not distract from the useful-ness of the measurement because itmakes no difference for the mea-surement principle used (Fig. 5).

The sound card having a stereoA -to -D converter, one channel isused as a reference channel whichreceives the generator signal direct-ly. The reference channel enables thesoftware to accurately measure thelevel and the phase of the generatorsignal. The generator signal is fedthrough the measured object, for in-stance, an amplifier or a filter, whoseoutput signal is applied to the otherchannel on the sound card.

The software uses the signals onthe reference channel and the mea-surement channel to compute thegain or attenuation caused by themeasured object, as well as thephase shift. The measurementmakes clever use of the A -to -D con-verter and a phase -sensitive rectifi-er. A series of individual measure-ments is performed in the selectedfrequency' range, and the result isdisplayed on the computer screen inthe form of a plotted graph.

The user may view two graphs at atime on the monitor. The parametersshown by the individual graphs areselected via the keyboard. Withmeasurements on amplifiers, for ex-ample, it is possible to view the ac-tual value and the phase shift of themeasured gain. Similarly, with im-pedance measurements the real andthe imaginary parts may be dis-played separately, or the discretevalues of an equivalent RL combi-nation.

The measurement parameters areeasily changed via the keyboard.Likewise, the complete bundle ofsettings is readily stored on the harddisk. Finally, an on-line help functionis available, and may be called up atany time to obtain a short descrip-tion of each available command.

442 Elektor Electronics 3196

REF. INP.

MEAS. INP.

.1.

SIGNAL GEN. 0

Fig. 4. Pinouts and 111

connecting diagram ofthe SoundBlaster VE16 sound card.

Y OLItFIRSTFREQLENCY RESPONSEMEASUREMENTAs your first measurement object wesuggest using an RC bandpass filter asshown in Fig. 6, connected to the rel-evant sockets on the SoundBlastercard (Fig. 4). The default parametersused by the measurement softwareare okay for this initial test All youhave to do is press the x key (for ex-ecute). That launches the frequency

t.

FM synthesischip

amplifier

Soundblasterspeaker output

3.5 -mmjack plug

LINE IN

rD C

I

SPEAKER OUT --s -

EL

16 -bit soundcard

111141

MP

10-

and phase response measurements,the results of which appear on thescreen after a while.

After the measurement, the dis-play shows two graphs as illustrat-ed in Fig. 7. To enable individualvalues to be read off accurately, youuse the + and - keys to manoeuvrethe marker. In this way you capture,for example, fr at 1,950 Hz, or an at-tenuation of - 9.77 dB at the reso-nance point. Both values come veryclose to the theoretical ones.

By pressing the keys correspond-ing to the letters enclosed in square

960053-14

brackets, it is possible to modify therelevant parameter in the software.That may be necessary at times toimprove the way new measure-ments are matched to given circum-stances.

At this point you are ready to doany AF gain and/or phase shift mea-surement you like. It should be clearby now how the measured object isconnected to the sound card. If nec-essary, an attenuator should be usedto prevent overdriving the mea-sured object or the sound card. Cir-cuits with a low -impedance output

AF analysersoftware

A -D converterreferencechannel

measuredobject

Soundblasterline input

A -D convertermeasurement

channel

graphicsII I

1111iifl

11 6

Fig. 5. Schematic rep-resentation of themeasuring principle.


LIMITS OF THEFREQUENCY RESPONSEMEASUREMENTNo measurement result makes sense if you neglect, or do notknow, the limits of the measurement system used. With fre-quency response measurements, the practical limits of the AFanalyser are determined by .0 number of external conditions,each of which has an effect on the accuracy of the measure-ment.Although sudden irregularities like off -scale peaks in thegraphical representation of a frequency response curve aresufficient warning that a serious measurement fault exists, it isstill useful to be aware of the main problems you mayencounter.

- The first source of trouble may be the FM synthesizer oscilla-tor on the sound card. From about 15 kHz, this oscillatorsupplies a triangular waveform instead of a sine -wave.This is owing to the fact that the oscillator is of the 'sam-pling' type. To keep the resulting error as small as possi-ble, certain measures are taken by the software so thatonly the relevant basic frequency of the signal, not any ofthe harmonics, is employed for the measurement. Nonethe less, results of measurements above 15 kHz should betaken with a pinch of salt.

- Second problem: the A -to -D converters must not be over-driven. Many measurements on amplifiers will thereforerequire an attenuator pad to be inserted in the measure -

Fig. 6. This simple RCbandpass is great foryour first measure-ment with theanalyser.

(less than about IOW) can be mea-sured directly. When a high -imped-ance output is used (more than10 kg.), impedance matching shouldbe provided by a small preamplifi-er with a high -impedance input.

NEXT MONTHNext month's second and last instal-ment of this article will guide youthrough the operation of the AFanalyser software. We also present asmall add-on box for measurements.Don't worry, the box contains only ahandful of resistors and a switch. To-gether with the AF analyser hardwareand software, this gives you a fairlyadvanced impedance measuring in-strument.

1 1

Fig. 7. Results of afrequencysweep phase measure-ment on the bandpassshown in Fig. 6.

6

0.004B

-6.25d0

-12.50dB

-18.75dB

-25.00dB

-31.254113

-37.50dB

-43.75d8

-50.00dB

ment channel. If you look at the attenuation graph abovethe frequency response, it is safe to say that the A -D con-verter is probably overdriven when levels greater than 0 dBoccur, i.e., when the signal level in the measurement chan-nel exceeds that in the reference channel.

Special attention should also be given to the input imped-ance of the SoundBlaster card. The fact that this inputdoes not have a particularly high impedance should betaken into account when measuring on high -impedancesignal sources. If necessary, insert a preamplifier with ahigh input impedance in the measurement channel.Obviously, the frequency response of this preamplifier mayalso be checked using the system.

A further limitation to keep in mind is caused by two con-tending factors: one the one hand, the 16 -bit resolution ofthe sound card, and on the other, the high (electrical)noise level which exists in a PC. Theoretically, a 16 -bitconverter achieves a signal-to-noise ratio of 95 dB at fulldrive. In a very 'noisy' environment such as a PC, howev-er, the present analyser system can measure attenuationsdown to about 70 dB. Not a bad value, mind you, consid-ering that better results are almost impossible to obtainfrom simple sound cards.

The final sources of interference which must be mentionedhere are stray capacitance and resistance, whose effect isespecially noticeable with impedance measurement on RFcomponents. More about this phenomenon in nextmonth's concluding instalment.

SIGNAL GEN.0 REF. NP.

Cl RI MEAS. INP.

V 90.00 .

6/.50 .

45.00 .

22.50 0

0.00 .

-22.50 0

-45.00 0

-67.50 0

-90.00

44

2.0 5.0 1.0 2.0 5.0 1.0 2.0 5.0 1.0 2.0

Elektor Electronics 3 96

Please mention ELEKTOR ELECTRONICS wizen contacting advertisers 45

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MTX Micro-mlnisture Room TransmitterBest-selling micro -miniature Room TransmitterJust 17mm x 17mm including mic. 3-12V operation. 1000m range £13.45

STX High-performance Room TransmitterHr performance transmitter with a buffered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation. 1500m range £15.45

VT500 High -power Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand delay with LED indicator. Size 20mm x 67mm. 9V operation 1000m range £19.45

HVX400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long -lean monitoring. Size 30mm x 35mm.500m range -_----...._119.45...

SCRX Sobcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCUM decoderconnected to the receiver Size 20mm x 67mm. 9V operation. 1000m range £22_95SCLX Subcarrier Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCUM connected to receiver. Size 32mm x 37mm. 1000m range £23.95

SCOM Sobcarrier Decoder Unit for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V »»_. 122.95

ATR2 Micro Size Telephone Recording InterfaceConnects between telephone line (anywhere) and cassette recorder Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £1345

*** Specials ***DLTX/DLRX Radio Control SwitchRemote control anything around your home or garden, outside lights, alarms. pagingsystem etc. System consists of a small VHF transmitter with digital encoder and receiverunit with decoder and relay output, momentary or alternate. 8 -way di switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200m.Complete System (2 kits). .......... ..... .... ............. £50.95Individual Transmitter OLTX £19.95Individual Receiver DLRX ................ .............. ....... ....... 137.95

MBX-1 Micro BroadcasterNot techntaily a surveillance device but a great idea! Connects to the headphone outputof your Hi-Fi tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavuunte music anywhere around the house, garden, in the bath or in the garage andyou don't have to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250rn range E20.95

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UTLX Ultra -miniature Telephone TransmitterSmallest telephone transmitter kit available. incredible size of 10mm x 20mm!Connects to line (anywhere) and switches on and oft with phone use.All conversation transmitted. Powered from line. 500m range £15.95

TLX700 Micro -miniature Telephone TransmitterBest-selling telephone transmitter. Being 20mm a 20mm it is easier to assemble thantJTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range

STLX High-performance Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone use.All conversations transmitted. Powered from tine. Size 22mm x 22mm.1500m range 116.45

TKX900 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes High power output giving range up to 3000m. Size25mm x 63mm. 9V operation_...».._..__....._...........__...._....»_.._ £22.95

C0400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm a 54mm. 9Voperation £30.95

C0600 Professional Bug lletector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers, cellular, taxis etc. Size 70mm x 100mm. 9V operation £50.95

QTX180 Crystal Controlled Roam Transmitterflarro.... band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our QRX180 kit (see catiogue). Size 20mm x67mm. 9V operatinn. 1000m range £40.95

QLX180 Crystal Cointrolled Telephone TransmitterAs per OTX180 hut connects to telephone line to monitor both sides of conversations.20mm x 67mm. 9V operation. 1000m range £40.95

IISX180 Line Powered Crystal Controlled Phone Transmitter.s per OLX180 but dra.ss power requirements from line. No batteries required. Size32mm a 37mm_ Range 500m £35.95

QRX180 Crystal Controlled FM ReceiverFor monitoring any of the '0' range transmitters. High sensitivity unit_ All RF sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation 160.95

A build-up service is available on all our kits if required.UK customers please send cheques, POs or registered cash. Please add£1.50 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.

SUNIADESIGNS

DEPT. EETHE WORKSHOPS, 95 MAIN ROAD,

BAXTERLEY. NEAR ATHERSTONE,WARWICKSHIRE CV9 2LE

VISITORS STRICTLY BY APPOINTMENT ONLY

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Anyone who is actively involvedin electronics and with access to

the Internet may use his or herPC to gather information about

components, technical softwareand other interesting products.

Via the PC you have almostinstant access to informationsource which are 'hot', up to

date and of a staggering size.From time to time. however, the

average Internet user has aproblem finding exactly those'sites' which have interesting

information. This page in ElektorElectronics is a new regular fea-

ture in the magazine, intended toinform you about Internet sites

that hold on-line informationwhich is of interest to electronics

enthusiasts like you.

This month we kick off by presentingthe www (world-wide web) pages fromthe USA -based semiconductor manu-facturer Harris Semiconductor. The ad-dress http://www.serni.h a rris.comstocks a wealth of technical literature inthe form of extensive datasheets oncomponents. It is also possible to down-load related software, and the site con-tains information about recently re-leased and about -to -be -released Harriscomponents. In practice, this informa-tion is much more up-to-date than theordinary databooks published by Har-ris. Furthermore, the www site allowsyou to submit technical queries to the

nicsdesign engineers at HarrisSemiconductor.A totally different Internet siteis the one from HiTools Inc.,who are also based in theUSA. HiTools are suppliersand manufacturers of micro-processor development sys-tems. The www pages foundat http://www.hitex.com bringyou, among others, lots ofdemo software like an 8051and an 80166 simulator. Ahighly interesting option of-fered by these pages is thelink to the so-called Chip Di-rectory, which enables you totrace the function and originsof unknown components.The actual search operation isquite simple Is all you have todo is enter the type numberof an unknown IC, and theprogram does the rest. Ifavailable in the database, theinformation appears on yourscreen after a short while.

A summary of the informationat this www site may befound on the DevelopmentTools CD-ROM. This CD-ROMcontains a number of HTML(HyperText Mark-up Lan-guage) files which give theuser information on4,000 chips and 150 manufac-turers. The CD-ROM also con-tains an 8051 and an 80166simulator, an 80166 debuggerand text versions of compilers.A list of Frequently Asked Ques-tions (FAQs) about the 8051,68HC11 and 68k families mayhelp to reduce the complexi-ty of developing applicationsfor these processors. As a mat-ter of course, the Chip Directo-ry is also included on the CD-ROM. Although the CD con-tains an HTML browser, manyusers will prefer their ownweb browser like Netscape,Mosaic or Internet Explorer.Fortunately, that is possible!

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The author of Chip Directory is Jaap vanGanstvijk who can be contacted at In-novative Design, P.O. Box 3215, NL-2601 DE Delft, The Netherlands, tel.(+31) 15 2132638, fax (+31) 152140244.

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Found a web site which other readers of Elek-tor Electronics should know about? Let usknow the name and URL by telephone, fir or

(elektuurgeunmet.440. If the site is in-deed useful and intensting, well put it in thelimelight using this column.

46 Elektor Electronics 3196

SURVEILLANCE TELESCOPE Russian zoom'&.escope adjusratie from 15: e E2rl complee era meta/ tripodmoos/de to use without the on the higher settings) 66min lase.eather carrying ease £149 ref HARMRADIATION DETECTOR SYSTEM Designed to be wetmowed andoonnededintaaPC,ktealfixremdemon.toring wholeo -ken!) coverage ex Complete with eetecer. cable arc softwarei_19 95 re BAR75

WIRELESS VIDEO BUG KIT Transmits video and audiotg- s from a la ratwe CCTV camera (inducted) to any standard steaSoni AI the component including a PP3 battery *9 ft iris a

;area packet with the lens regaling a hereabout 3mrn diameterE r." ed CI telescopic aerie but a piece of wire above 4' tong rift

ea range of up to 100 metres. A single PP3 in probably giveesstnan 1 torus use E99 REF EP79 (probealy notecersabfar)CCTV CAMERA MODULES 46X70X291Ttn. 30 grams. 12e'0071A cum ebecuorsc srudier. lErnm F2 lens. COR 5121492pates video oup trite Iv p -p (75 ohm). Works ctrecty into a scan orvideo input on ate or video IR secretive E79 95 ref EF137.IR LAMP KIT Sutstaefolhe acre camera erades the camera

be used in total darkness' 65.99 -ref EF138

TANDATA T D1400 VIEWDATA Complete system ccreonsing-radars. infra red remote keyboard. psu. UHF and ROB ottpUtc none lead. R5232 *MA ate ouVut E9.95 ref EARS?MAGNETIC CARD READERS (Swipes) £995 Cased wantytewels_ designed to read standard crelt cattle they rare? wiresconing out of the head so they may write as weir complete withcontrol eicUoracs PCB just £995 re BAR31PANORAMIC CAMERA OFFER Takes double widthphotographs using standard 35mun fen Use in horizontal or venommode Corr-Vete with strap £7.99 re BARICOIN OPERATED TIMER KIT Complete with coinstotmechanism. a e 1-e :slay. relay output. pin a consiotany:ring you -. 5 1. fridges. drinks cupboards. HIFItakes 5Epsana £1 c: s DCoperate2. pnce lustE7 S9 re ErAfa7ZENITH 900 X MAGNIFICATION MICROSCOPE Zoommete constructor. buil in ight. shrimp farm. group viewing screenPots d accessories. E29 re MAYO',LUSIT EL 166U Twin lens Russian 2 1fie sq rear camerasipped) with two free rots of colour Ern. fig up miasmata:. 3 elementf 45 tens: EIS 93 ref BAR36.AA NICAD PACK Parr d4 tagged AA reads £2.99 ref BAR34PLASMA SCREENS 2221110mm. no data hence E4.99 refBMWNIG HTSIG NTS Model TZS4 with infra red Kurninator. views id to75 meresin ful darkness in i nfrafed mode. 15:rn range 49nm tens13 deg angle of new. focussing range 1.5m to i flinty_ 2 AAbaneriesreclined 350g weight E.210 ref BARBI 1 years warrantyFILIN-1 ificrn range 15 deg angle el view. focusing Mr. -Meaty.£179 ref EARS? A separate infra red eight a amiable at 00 ref

WHITE NIG HT SIGHTS exceSertproles rig sight. erne.nand held with camotaged carrying case £325 1 years warranty.MEGA AIR MOVERS 375 cubic feet per rrint 240s 200 wan.2_830 rpm. reversabie, rxr UK rrad.e. new. Alumni an. current estprice about £180 ours? E29 95 ref BOGS.LIQUID CRYSTAL DISPLAYS Bargain prices.16 character 2 line. 65x14mm £1.99 ref SM1612A16 character 2 line. 99x24mm £299 ref SM1623A20 character 2 tine, 83x19mm £399 ref SM2020A16 character 4 line, 62x25mm £5.99 ref SMC1640ATAL-1 1101AM NEWTONIAN REFLECTOR TELESCOPERussan Superb astronorriciesccipe, everythingyou needforscmesent:ruse-dr gazing! ith to 169x magielvativm. Send or fax fix furthercleats £249 ref TAL-1GOT AN EXPENSIVE BIKE? You need one of ourbode a-4ms.they sock eke a standard water tone. but open the top, insert a keyto actuate a mcdon sensor alarm bifttinside Fit as standard bodecanters. supped with two keys SALE PRICE £7.99 REF SA -32GOT AN EXPENSIVE ANYTHING? You need one of ourcased %Seaton Warms. key:switch operated. hey cased pat St it toanything from videos to caravans. provides a years protecsco from1 PP3 teary. UK made SALE PRICE £4.99 REF SA33DAMAGED ANSWER PHONES These are probably beicnarepel so just £499 each BT response 2E0 rnacNnes REEF SA30COMMODORE GAMES CONSOLES Just a few citreseto dear at £5 ref SA3I. Condit on unknownCOMPUTER DISC CLEAROUTWearelertrnthatototsotteratepacks di at need deanng soave are sdsng ediscvalueony 5.0 dissfor E4. thats pat ep eachli(out deice G ct as) EA ret EPEEIBM P82 MODEL 160Z CASE AND POWER SUPPLYComplete with tan etc and 203 watt power supply. E9.95 ref EP67DELL PC POWER SUPPLIES 145 watt.150x159x85rrim complete with wen tryleads and iec socketSALE PRICE E9.99 ref EPod1.44 DISC DRIVES Standard FC 3.5* dines Out ref urns so theywa need Stanton SALE PRICE £4.99 ref EP6131.2 DISC DRIVES Standard 525' dies but returns so they tailneed anenton SALE PRICE £4.99 ref EF69PP3 NICADS Unused but sane storage marks. £4 99 ref EPS2DELL PC POWER SUPPLIES (Customer returns) SUnclardPC pets compete *An lily leads. case and fan pads of two psusSALE PRICE ES FOR TWO!! ref UsEllGAS HOBS AN D OVE NS Brand new gas appliances, perfect fc rsmal Out etc Basic Sooner hob SALE PRICE E24.99 ref EP72Basic sm al bun in over, SALE PRICE E79 ref EP73BITS AND BOBS We have a quantly of cased modems!nu:totems etc ?recent specs but dee stovers E4 eath ref EP63RED EYE SECURITY PROTECTOR 1.003 *art outdoor FIRscen SALE PRICE E9.99 ref a.'"ENERGY BANK KIT iO3 6"-x6' 6v 10CmA pariers. 100 diodes.cotheciton details etc £69 95 ref U112.PASTEL ACCOUNTS SOFTWARE. does ederyning for alsizes of businesses includes wordprocessor. report writerwindowing. networeade up to 10 strides multiple ash books etc200 page.comprehensrve menial. 90 days free techril support(0345-326009 try Deere you buy!) Current retail price is £129.SALE PRICE £995 ref SA t2 SAVE £120"

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12V2AMP LAPTOP psus 1112x55x43mm (ulci urfes =rhiarct IECsocket) aria 2rn lead with plug 100-240r IP BAG REF SA15.PC CONTROLLED 4 CHAPINEL Thl ER cmtra (onion driesetc) to toe rterns(BA240veach)warithiselConplete. erth Sorra we.relays. PC8 etc £2599 Ref 95/26COMPLETE PC 300 WATT UPS SYSTEM lop of the rangeUPS system providing protection for your compeer system andvaluable software against mans power fluduabons and cuts Newand boxed. UK made Promcles up to 5 rninsrunning mein tf>z eientof complete power failure to Mow you to run your wean clowncorrecty. SALE PRICE just E89.00.SOLAR PATH LIGHTS Low energy waertiglits powered by thesurf buninPIRsotheyworkwnenyouwalkpast.Indudessciarpand& rethargeable bat SALE PRICE E19.95 REF EF62B IG BROTHER PS U Cased PSU.6v 2Aoubut. 2m ep lead. 1.5minput'_-. UK made 2,00 SALE PRICE E4.99 REF EP7

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FtACALMOD EM BONANZA! I Race MPS1223 123/1175mo:o':eephone ead. mans lead, manual and corms software mecheapest w ay ono the nee Wins for tint E13 ref fLEC13.4.6mw LASER POINTER. BRAND N EVA MODEL NOW INSTOCK!, supplied in fully built form (looks like a nicepen) complete with handy pocket onp (which also actsas the on/off switch.) About 60 metres range! Runs on2 AAA batteries. Produces thin red beam ideal forlevels, gun sights, experiments etc. just 638.96 refD EC49 TRADE PRICE 628 MIN 10 PIECESBULL TENS UNIT Fuel bud and tested TENS (Trar=udneousElectrical there StrrnAaton) end, ccoNolete with electrodes and fillinstrtrawns TENS Is used for the reef of pan et= in up to 70% ofsuffeers DI:ghee pan retie. sale arid easy to use can be used incorium -ton with analgen £49 Ref TEWICOMPUTER RS232 TERMINALS. (LIBERTY)Excesentquaky modern ur4s,(1Ae wyse 50.$) 3,R5232 20 fine:bon keys 50treoto 38.403sautt rnenuamren port screen. cursor. and keyboardsetup menus (18 merits). FEE NOvaRUSSIAN MONOCULARS amazing 20 bras rragridealon.coated ter.ses. came rig case and srputinerstrap E29 95 REF BAR73PC PAL VGA TO TV CONVERTER Converts a criourTV idoa OasicVGAspreen Compledwitnbuninpsu teadandstrate lavafor Laptops or a cheap upgrade Suppled m kit form for homeassembly. SALE PRICE F25 REF SA34EMERGENCY LIGHTING UNIT Complete urit watt 2 double

fioxagrils. Malin charger arid auto switch Futycased. 6v 8AHlead and retrd_ (secondhand) £4 ref litAG$P11.

SWINGFIRE GUIDED MISSILE WIRE. 4_203 metre reel ofultra Min 4 coreinsudted cad e. 2Gbs breaking strain less than 117711ttidcr WSW alarms. maercorns. dolls houses at £13.99 refEP51ELECTRIC CAR WINDOW DE-ICERS Cerreited with cobfeplug etc SALE PRICE JUST EA.99 REF SA23ASTEC SWITCHED MODE P811 B la41012 Gves +5 (a 3.75A..126 1.5A. -120 4A 230/110. eased.81X11012 E5 93 refAUGEF3AUTO SUNCHARG ER 155x83Crnm scrarpanei orswadeand 3metre lead tried with a cigar plug. 12r E9.99 REF S4T5

TOP QUALRY CENTRIFUGAL MAINS MOTORS SALEPRICE2 FOR JUST E2.60 REF SA38ECLAT RON FLASH TUBE As used ,n po.ce car fae-ing lightse:c.fu.stet s_11 eel 83-103 tastes a MA if 03.99 REF SA1524v AC 96WATT Cased poeer suppy. New. £9 99 REF SA40M ILMARYSPEC G EIG ER COUNTEFtS unused anstsontrfa'nHer me-ty's razes SALE PRICE E44 REF SA16MICRODRIVE STRIPPERS woad cased tape drives idea forsi-:: lots of useut goodies indudrtlg a smart case, and Ids ofcorrcomerits SALE PRICE JUST £4.99 FOR FIVE REF SA26SOLAR POWER LAB SPECIAL YousetTWO6'xir eu 130mAsolar ces. 4 LEDs. wile buzzer so itch plus 1 relay emote( Superb.due Ni SALE PRICE JUST E4.99 REF SA27RGB/CGAfEGAJTTL COLOUR MONITORS 12' in good

Bath anodised metal case. SALE PRICE 649 REF SA16PLUG IN ACORN PSU 19v AC 14w. 6299 REF MAG3P10POWER SUPPLY fifty cased %EV') mans and op leads 17n DC3)SnAo Bargain pace £599 ref MAWP3ACORN ARCH hIEDES PSU c5v (a 4.4A. on sw uncased.

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seevi e mans input 145x10045rnm £3.99 REF MAG7P213.8V 1.9A PSU cased enn leads. Just E9 99 REF MAG10P3200 WATT INVERTER Cexwerts 10-15v DC into either 1100 or240, AC Fuly cased 115:365156mmi. complete earn heavyclutyperwe lead. cigarpg. AC otaesev-kw aienoverloadshueowauto shod erCut sluA (Irma. 500 input Over v Wage sh Litho. , a

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U NIVERSAL SPEED CO NT ROLLER KIT Designed by us lc:the 06 =woo Da for any I2vmdor up to 304. Complete am Fc6etc A feat ask may be re aired £1700 REF: MAG17COMPUTER COMMUNICATIONS PACK Ka =deem 100rCl 6 core carte 100 cable ceps. 2 kne rimers with RS232 interfacesarid at connectors etc Ideal low cast method of commuricathobetween PC's aver a long distance Complete Ni £899VIEWDATA SYSTEMS mace by Flakes. complete s

1200075 modern. keyboard. psu etc ROB and corrposte car_menu driven. authliader etc SALE PRICE £1299 REF 5A18AIR RIFLES.22As used byreCranese armyratrainingpupc..sessalters is airs: abodlE3395 Re EF7B 503 pees E450 re E=PLUG IN POWER SUPPLY SALE FROM E1.60 Flug.s13A socket wan °Wounded Wee Types avalante9vdc150rAit.53ref SA19, Svdc 200mA 00 ref S. 'A=0. 6 5mIc 500mA £2 ref SA21

VIDEO SENDER UNIT. rransros talc au,oartcl walsfrom ether a vsdeo camera. ',deo recorr. Computer e.--toanystandard TV set in a WC ranger (tune IV to a spare channei) 12v DCcp. Pnce tsE15 REF: MA015 124 ISSU is £5 extra REF: MAGSP2'FM CORDLESS MICROPHONE Smes nand tied unit with a50(7 rancftt 2transrrrt pow er !clefs Reps PP3 9v banery Tuneaeleto arty FM receiver Price is El5 REF: MIAGISP1' MINATURE RADIO TRANSCEIVERSApard wane takes*Ana ramie Lici ta 2 ion ince en =airy_ Urrismeasu re 22x 52x155menirks:rang cases arid earp'ces aPP3redd E30 CO pr REF: MAG30' FM TRANSMITTER KIT housed mi a standard working 13A.adaptell debug runs ri ret-ty off tre mans so lasM forever! why p a,£7070 or thee is E t5 REF. EF62 (pct) Transmits to any FM redo'FM BUG BUILT ANDTESTEDsuvericroregn blot Stc:to <tete:vie acerc,es. 9e battery rol'd £14 REF. 6tAG14TALKING COINBOX STRIPPER COMPLETE WITHCOINS LOT M EC HAN ISMS origir.aty rnsleto resat atE79eti. ---these on -'s are cesigned to convert an ordnary phone i :.payphione The units have thelocks mating and sometimes t - -

tinges However ttsey can be adapted kr I teironlizail use or us4 :scenetning Erse', SALE PRICE JUST E250 REF SA23GAT AIR PISTOL PACK corrowe with pistol. demand peee_s£1295 Ref E1-4.2.8' eida pedetS (500) £4.50 ref EF80

6'712- AMORPHOUS SOLAR PANEL 12r 15553 tan13CmA SALE PRICE E4.99 REF SA.24FIBRE OPTIC CABLE BUMPER PACK 10 metres lc; £4 9-,ref 'AMP 13 idea fa ea oefi.orrter.130 m for £12 99 ref MAGS3F

MIXED GOODIES BOX OFMIXED COMPONENTS WEIGHING 2 KILOS

YOURS FOR JUST £8.994X28 TELESCOPIC SIGHTS Sutst:e to -'es. Tour:fusel. good light gathering prwarties. £1995 re' -RATTLE BACKS irterestng things these 5.- deice of sopamper Ike rraserat triatnyou try to spin non Me arty sp,7sone via). in factdyou spin lithe Wrong' way it sops ct id awn ace" :and gas bade menthes way! Et 99 ref GUJOIGYROSCOPESRememtc-nnese?wes we haverrxind acompen,Plat sea manufactures these popular sdentic toys. paled Odereicluciaboral use etc £6 ref EP70

HYPOTHERMIA SPACE BLANKET 2.16,06(km eker..resecbiae-Xe.t. reects more iten 90% of body heat_ Also vxele extraconsinicton or two way 17 mos! each ref 04041LENSTATIC RANGER COMPASS Cs fled capsule. strongmetal case. large luminous pants. Sht Brie with magnifying viewer.5Ornm dma. 86gm. £1099 ref 0ltien4.

RECHARGE ORDINARY BATTERIES UP TO 10 T PAESIWin the Battery Wizard! Uses the lade purse wave charge systemto charge ad popidar brands of oranarybanerds MA An. C.D. foureadral Led system shows* henbateriesarecharged, athomattalyretests uneatable Ws, complete with mans adaptor. GS approvedPacers £21.95 ref EP31TALKING WATCH Yess_ itareintyters you Meat* atthepress ofa button_ Also features a voce Warm tnat wakes you up and Iola youwhat the tme is! Lathan ceilIndiated 67.99 ref EP26.

PHOTOGRAPHIC RADAR TRAPS CAN COST YOUYOUR LICENCE! The new mutesna 2000 radar detector ca -prererieven Ira most respoesbleof dmers Immersing theirtimme!A4 uststla aultie alarm with Sratirmig iectsgiresintant warring*,radar zones Detects X. K. and Ka bands 3 rrae range, 'wet the rrtaroundbends'anclreartraplacatearricrosaefust4 25'1Q 5txCan pay fa mush m lust one day £79.95 ref EP3SANYO NICAD PACKS 1.20mrmrl4rnm 4 Se 270 rnaH sutatrefa cordms pones sic PaDc CI 2 pat E5 ref EP783" DISCSAs used cn cider Amstrad machnes. Spednan plus?etc £3 earn ref BAR400STEREO MICROSOPES BACK IN STOCK Russan. 200'complete with lenses. sighs fiters etc et very compreheravemicroscope that iv nomnaly be around the E7C0 mark MT priceis iustE799 mid money back guarantee) full cetaisi/Icalak)gue Ref951300.

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ADVANCED STOCK CONTROL AND KITTING PROGRAM

For the first time in a marketdominated by large expensive ac-counts -oriented packages, Num-ber One Systems have launchedStockit, a simple uncomplicatedstock control program for the realworld.Drawing on the experience of en-gineering entrepreneurs and de-sign departments already usingNumber One Systems range ofelectronic CAD programs, Stock -it is designed to help smallermanufacturers and R&D depart-ments with the day-to-day prob-lems of managing stock.Stockit is specifically tailored fora small to medium sized produc-tion or development environ-ment- it is not an adaptation ofa program originally aimed atlarge-scale manufacturers, ac-countants or retailers.Stockit holds complete records ofparts lists, stock levels and com-ponent suppliers, automaticallyallocating stock when a new pro-duction batch is required. A valu-able trial kitting facility allowsdifferent production scenarios tobe evaluated before a definitive

production plan is adopted. Theability to handle fractional quan-tifies allows cable lengths, con-sumables and labour to be in-cluded in the calculations. Stock -it even prints enquiry sheets tobe sent to suppliers for quota-tions.The structure ofStockit enables newusers to migrate exist-ing systems gradually,one assembly at atime. The benefits ofStockit can be realisedquickly without wait-ing for every singlepart to be entered.By maintaining anup-to-date cost foreach part, Stockitmakes it simple to de-termine product man-ufacturing costs andorder values. Stockitcan calculate a cur-rent stock valuationin a matter of sec-onds.While designed withthe electronics indus-

try in mind, Stockit is equally ap-plicable to batch manufacture inmany other industries.Priced at just £145.00, Stockit isfar easier to use I s and cheapers than many accounts -based

stock control programs intendedfor large-scale manufacture.

Number One Systems,Harding Way, SomershamRoad. St. Ives, Huntingdon,Cambs PE17 4WR. Tel.(01480) 461778, fax (01480)494042.

Munimr One Systems STOCXIT

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BUILD 8.888 0.880 8.880EUX181-506S 17.880 17.888 8.808

CLB388GTP 17.860 17.888 8.8e8CL11308RTP 17.880 17.888 8.888C0148LACR 19.848 19.048 8.889C01411LUE 15.380 15.388 8.888C014BROW 13.600 13.688 8.898C014RED 13.948 13.948 8.886CX18U 17.008 17.886 8.888CX21X 17.088 17.088 8.998DCS-S08806-PCB 28.090 17.008 8.888EXAMPLE -PCB 17.008 17.888 8.996EXAMPLE -PRODUCT 0.008 8.888 8.888EXAMPLE -SUB' 17.888 17.008 8.888

EXAMPLE -SUEZ 17.888 17.000 8.888

ft :mil "..11411011V: I

DOUBLE -SPEED CD-ROM DOUBLES AS

Portable Add-ons recently intro-duced the launch of CD_Mobile,an external double -speed CD-ROM drive and Type -11 PC CardInterface designed for notebookcomputers. With four uniquepower options (computer, mains,standard, or rechargeable AA bat-teries) the CD Mobile gives totalflexibility of use. Since theCD_Mobile can be battery -pow-ered, it can be used anywhere,making it a truly portable solu-tion.At a retail price of £299, CD Mo-bile is an inexpensive way ofadding CD-ROM functionality toexisting notebooks. The few note-books with a CD ROM drivebuilt-in tend to be prohibitivelyexpensive for most users. Since aninternal drive always draws cur-rent, it will place a load on themachine's battery; in addition, abuilt-in CD-ROM drive adds to anotebook's bulk. As the CD Mo-bile is a separate unit, it can be un-plugged and the PC Card Inter-face removed when not in use, re-ducing both power consumptionand weight. The CD_Mobile can

PERSONAL AUDIO CD PLAYER

e,asily be shared amongst a groupof users. The IDE-based interfaceis, as with all good PC Cards, fullyhost-swappable.The CD Mobiles CD-ROM driveis fully MPC2 compliant. It alsosupports Video_CD and CD-i inaddition to CD-ROM modes _1and 2, audio CDs, multi -sessionPhoto CD, and CD-XA.The beautifully styled CD_Mo-bile has a full control panel and amulti -function LCD screen. Theunit can be used as a superb -quality personal CD player, al-lowing you to listen to yourfavourite album while compilinga spread -sheet on the train. TheCD -Mobile may also be usedwith recent in -car stereo systemsthat feature a line input, or anycassetteiradio if a commonlyavailable adaptor is used.

Portable Add-Ons (UK) Ltd.,Surrey Technology Centre,40 Occam Road, GuildfordGU2 5YH. Tel. (01483)440777, fax (01483) 452304,e-mail:cbrooksC:Dportable.co.uk.

A48 Elektor Electronics 3 96

New BooksBattery Reference Book2nd Editionby T.R. Crompton

ISBN 0 7506 2567 8Price £ 50.00

This second edition ohs very useful refer-ence book is now in paperback and costsless than half the original hardback issue.

As before. the book guides the readerthrough the subject in a logical sequenceand covers electrochemical theory as itapplies to batteries: battery selection:theory. design, electrical and perfor-mance characteristics: applications ofvarious types of battery; theory nd prac-tice of battery charging. The book pro-vides comprehensive information frombattery manufacturers about the perfor-mance characteristics of the batteriesthey supply. There are a number of usefulappendices. including a glossary, bibliog-raphy and details on battery standards.

Like its predecessor, batteryReference Book should prove a godsendfor designers of all types of battery -oper-ated equipment. battery manufacturers,and electrical and electronics engineersand technicians whose use batteries intheir work. It should also prove useful toresearch organizations.

Electronics for Student Engineersby Bruce NewbyISBN 0 7506 2144 3Price £ 12.99 paperbackFor many 'non -electric -al' engineering stu-

dents, electronics and electrical princi-ples can be difficult to grasp. Also, mostengineering students coming new to thesubject need a clear introduction to elec-tronics which will help them master thekey concepts at the outset of their stud-ies.

This book will provide an introductionto electronics and electrical principlessuited to a wide range of courses, includ-ing GNVO Engineering (Intermediate andAdvanced), BTEC National, HNC GeneralEngineering, and BTEC/City and Guildselectrical and electronic craft and techni-cian courses, including NVOs.

These Butterworth -Heinemann booksare available from Reed Book Ser-vices. P 0 Box 5, Rushden NN10 9YX.

Wireless for the Warrior - Volume 1by Louis MeulsteeISBN 1898 805 08 3Price £ 27-50 paperbackThis is the first volume in a projected

series of book - subtitled 'A technical his-tory of Radio Communication Equipmentin the British Army' - which it is plannedwill eventually cover transmitters andreceivers from the First World War up tothe 'Larkspur system.

Louis Meulstee is well known to col-lectors of historic military radio equipmentworld-wide, having written more than ahundred magazine articles. He is widelyrespected for the depth and thorough-ness of his research.

Volume 1 of Wireless for the Warrior isdevoted to Wireless Sets No. 1 to No. 88,and contains over 150 photographs. 320drawings and 130 tables. It is based onmore than fifteen years of research in anumber of official and private archives inthe UK and elsewhere.

An explanation of the Various TypeNomenclature systems used for armyradio equipment from WWI to the presentday is followed by descriptions of the setsthemselves. The aim in each case hasbeen to describe the history, technicaldetails and the aerials and accessories

used with each set, together with sparesschedules. Where the set was used inmore than one application - as mobile orground station. for example - details ofthe variations are described..

The descriptions of the sets are fol-lowed by a series of appendices:Glossary of Terms; Condensed Data ofEquipment: Accessories List; ArmyValves Designation and Equivalents;Table of Frequency coverage.

In his foreword to the book, Dr P JThwaites. Deputy Director of the RoyalSignals Museum at Blandford. Dorset,has welcomed it as forming a valuablereference source for all those interestedin historical military radios.

he book is published by G C ArnoldPartners. who also publish Bygones andMorsum Magnificat magazines, as well asa number of other books for the vintageradio and telegraphy enthusiasts.G C Arnold Partners, 9 Wetherby Close.Broadstone. Dorset. England BH18 8JB.Phone/fax 01202 658 474.

MathPlusThe natural equation solsing and graphing tool

MathPlus , a software program pro-duced by Waterloo Maple of Canadaand available from RobinsonMarshall, is a teaching and learningmathematical tool for secondaryschool, college and university educa-tion. It also has many extensive usesin the industrial arena and particularattention to engineering fields with itsgraphical capabilities and array ofmathematical functions.

MathPlus is available for Windowsand NT. and Macintosh and Power -Mac It will also soon be available onUnix systems and the CD ROM for-mat. It is an improved version ofTheorist, a computer -algebra pack-age that has been available for theMacintosh for several years. It differsfrom packages such as MathType inthat it is primarily a teaching aid.

MathPlus enables the user tomanipulate equations, perform sub-stitutions, expand expressions, andcarry out a number of other functions.In addition, there is a wealth ofgraphing options, including three-dimensional plotting and animation.which is very easy to set up.

All expressions are displayed

mathematically in standard mathnotation. All results are indented inthe MathPlus built-in outliner in sucha way that the succession of ideas isimmediately apparent to the user. Italso allows the user to select sec-tions of an equation, clicking anddragging only desired sections forfurther manipulation. Intermediateanswers are displayed as expres-sions which can subsequently beused again in later derivations.

There are no programming lan-guages to learn and no syntax errorsto puzzle with. MathPlus is intuitivefrom the beginning.

If you are looking for a softwarepackage for teaching or learningmathematics. MathPlus is for you.

MathPlus is available fromRobinson Marshall (Europe) PLC, at asingle user price of £ 199 excl. VATand ux postage at £ 5-99. Thisincludes free unlimited technical sup-port. There is a secondary schoolunlimited site licence at £ 995.Nadella Building. Progress Close,Leofric Business Park, Coventry,Great Britain CV3 2TF.

ELEKTOR ELECTRONICS MARCH 1996 49

50 Please attention ELEKTOR ELECTRONICS when contacting advertisers

POWER AMPLIFIER MODULES -TURNTABLES -0 MERS-LOUDSPEAKERS-19 INCH STEREO RACK AMPLIFIERS

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Affianced 3 -Way Stereo Active Cross-Oret housed in a 19' a 1U case. Each channel has three level maim:,bass_ and & top. The remorabte front fascia allows access to the programmable OIL switches lit adjust P.cross -over frequency: Sass -Mid 250:S.O.i60040.. Mid -Top 1 talf.KHz. all at 24dB per octese. Bass mien rancheson each bass channel Nominal 77SrnV inputloutput Fully compatible with OMP rack amplifier and modules.

Price £117.44 - £5.00 P&P-1-4-717111- h -T .-11-11- TY:

STEREO DISCO MIXER . 1 7 C2-.1I. S R vagLo ec.iri.sus e...!LED meuirs MANY OUTSTANDINGFEATURES:- inelochng Echo with repeal &speed control, DJ UM with talk -overswitch, 6 Channels with individual fadersplus cross lade, Cue Headphone Monitor. 8Sound Effects. Useful combination of thefollowing inputs, 3 turntables (mag), 3mice, S Line for CD, Tape. Video etc.

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'pelf110.-ssAcisl.id.r.11.181j14.8,,tortiill.. SUPPLIED READY BUILT AND TESTED.Masa nod -0 s Ave ertal a ante -.d rap-ta£401 Ica e.iarer. ant inerroarce as a rea-rcc arc. -vraSess m awastatte to soot ea needs site Brafrar..-41.0-4 Ad*, (Ames. c led-vdi 1-4et. Wben conwaRn; pet., NOTE Mat Al maPa:s power swept, ("Accra) - sr s -I zi PC a 0-,drive oredif so poser a L.L.--RALaa V. nuts An coo err are wan 0-4 550.1 cavil Weer

THOUSANDS OF MODULES PURCHASED BY PROFESSIONAL USERSOMP/MF 100 Mos-Fes Output power 110 wattsR.M.S. into 4 ohms. Irequency response 1Hz - 100K H z-3dB. Damping Factor -300, Slew Rale 45V/uST.H.D. typical 0.002%. Input Sensitivity 500mV. S.N.R.-110 dB. Size 300 x 123 x 60mm.PRICE 040.85 - £3.50 PAP

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-loftyOMP/1AF 200 Mos-Fett Output power 200 wallsR.M.S. into 4 ohms. frequency response 1Hz - 100K Hz-3413. Damping Factor 300, Slew Rate 50V/uS.T.H.D. typical 0.001%. Input Sensitivity 500mV. S.N.R.-110 dB. Size 300 x 155 x 100mm.PRICE C64.35 - C4.00 PEP

OMP/MF 300 Mos-Fes Output power 300 wattsR.M.S. into 4 ohms. frequency response 1Hz - 100KHz-3dB, Damping Factor 300. Slew Rate 60V1uS.T.H.D. typical 0.001%. Input Sensitivity 500mV.-110 dB. Size 330 x 175 :100mm.PRICE £81.75 - £5.00 PAP

OMP/MF 450 Mos-Fet Output power 450 wattsR.M.S. into 4 ohms. frequency response 1Hz -100KHz-3dB, Damping Factor >300. Slew Rate 751/1uS.7.11D. typical 0.001%. Input Sensitivity SOOmV. S.N.R.-110 dB. Fan Cooled. D.C. Loudspeaker Protection, 2Second Anti -Thump Delay. Size 385 x 210 x 105mm.PRICE C132.85 - C5.00 PAP

OMP/61F 1000 Mos-Fes Output power 1000 wattsR.M.S. into 2 ohms. 725 watts R.M.S. into 4 ohms.frequency response 1Hz - 100KHz DampingFactor 300, Slew Rate 75VIuS, T.H.D. typical0.002%. Input Sensitivity 500mV. S.N.R. -110 dB. FanCooled. D.C. Loudspeaker Protection, 2 SecondAnti -Thump Delay. Size 422 x 300 x 125mm.PRICE C259.00 - C12.00 PAP

NOTE 1.105.FET MODULES ARE AVAILABLE IN TWO VERSIONS.STANDARD - INPUT SENS SOOrnif. BAND WIDTH 1005104.PEC (PROFESSIONAL EOUIPMENT COMPATIBLE) - INPUT SENS775-Y. BAND WIDTH BOKHA ORDER STANDARD OR DEC.

1110:141.Join the Piezo moluttont TM low dynamic mass Ino voice cont or a Psezo tweeter produces an improvedtransient response with a lower distortion level than ordinary dynamic tweeters_ As a crossover is not requiredthese units can be added to esisbng speaker systems of up to IN watts (more if two are put in series FREEEXPLANATORY LEAFLETS ARE SUPPUED WITH EACH TWEETER.

TYPE 'A' (KSN1036A) 3' round with protective wire mesh. Ideal forbookshelf and medium sized Hi.Fi apeakers. Price C4.90 - 50p PAP.TYPE 'B' (KSN1005A) super horn for general purpose speakers.disco and P.A. systems etc. Price C5.99 - 50p PAP.TYPE 'C' (KSN1016A) 2'W wide dispersion horn for quality Hi-Fi sys-terns and quality discos etc. Price C6.99 - 50p PAP.TYPE '1:1' (KSN1025A) x6" wide dispersion horn. Upper frequencyresponse retained extending down to mid -range (MHz). Suitable Tor highquality Hi -Fs systems and quality discos. Price £9.99 - 50p PAP.TYPEE' (KSN1038A) 35." horn tweeter with attractive silver finish trim.Suitable for Hi -Fs monitor systems etc. Price 05.99 - 50p PAP.LEVEL CONTROL Combines, on a recessed mounting plate. level controland cabinet input jack sockeL 65:85n m. Price 04.10 - 50p PAP.

\ter

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z I c....rone-2 to take advaidagiw et Cite istsitt- *NJ' mule actn roDIMS istliteShoho= _ _CSdisiteere enti e....Vedey !iced plies vv.w dm-pert:on- . - estrixted ZS -nor -ism caner vwCflion aril Peer

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POWER RATINGS QUOTED IN WATTS RMS FOR EACH CABINETFREQUENCY RESPONSE FULL RANGE 4514z - 20KNz

Lb I FC 12100WATTS (100dB) PRICE 0159.00 PER PAIR1121FC 12-200WATTS (100dB) PRICE C175.00 PER PAIR

SPECIALIST CARRIER DEL E1250 PER PAIR

OPTIONAL STANDS PRICE PER PAIR C49.00Delivery 05.00 per pair

kopuipla 41.4 4 ; Si" LARGE SELECTION OF SPECIALIST LOUDSPEAKERSAVAILABLE, INCLUDING CABINET FITTINGS, SPEAKERGRILLES, CROSS-OVERS AND HIGH POWER, HIGHFREQUENCY BULLETS AND HORNS, LARGE (A4) S.A.E.(60p STAMPED) FOR COMPLETE LIST.

McKenzie and Fane Loudspeakers are also available.

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AU. EMINENCE UNITS 8 OHMS IMPEDANCE8 -100 WATT R.M.S. ME8-100 GEN. PURPOSE, LEAD GUITAR. EXCELLENT MID. DISCO.RES. FREO. 72Hz. FREQ. RESP. TO 4/(Hz. SENS 97d8. PRICE C32.71 - C2.00 PEP10- 100 WATT ELMS. ME10,1 00 GUITAR. VOCAL KEYBOARD, DISCO. EXCELLENT MID_RES. FREO. 71Hz. FREO. RESP. TO 7/(tiz.SENS97dB. PRICE 033.74 - C2.50 P&P10- 200 WATT R.M.S. MEIO.200 GUITAR, KEYB'D, DISCO. VOCAL EXCELLENT HIGH POWER MID.RES. FRE0.65Hz. FREO. REST.. TO 35KHz. SENS 99dB. PRICE C43.47 - C2.50 PEP12' 100 WATT R.MS. ME12.100LE GEN. PURPOSE. LEAD GUITAR. DISCO, STAGE MONITOR.RES.FREO. attz. FREQ. RESP. TO 6KHz. SENS 100dB. PRICE C35.64 - C3.50 PAP12" 100 WATT R.M.S. ME12-100LT (TWIN CONE) WIDE RESPONSE. P.A.. VOCAL STAGEMONITOR. RES. FRED 4214._ FREO. RESP. TO 10KHz. SENS 94dB. PRICE 036.67 - C3.50 PAP12- 200 WATT R.MS. MET 2.200 GEN. PURPOSE. GUITAR. DISCO. VOCAL EXCELLENT MID.RES. FRED. 55Hz. FREO_ SEEP. TO 6KHz. SENS 96dB. PRICE C46.71 - C3.60 PAP12" 300 WATT R.MS ME i 2-300GP NIGH POWER BASS. LEAD GUITAR. KEYBOARD. DISCO ETC.RES. FRE0.471M. FRED- BEEP. TO SK Hz. SENS 103dB. PRICE 070.19 - C3.50 PEP15' 200 WATT R.IgS.111E1 5-200 GEN. PURPOSE BASS. INCLUDING BASS GUITAR.RES. FREO. 46Hz_ FREO. RESP. TO SKI42, SENS 99d13. PRICE 050.72 - C4.00 PIP15" 300 WATT R.M.S. IA El 5-300 HIGH POWER BASS. INCLUDING BASS GUITAR_RES. FREO. 39Hz. FREQ. PEW. TO 3KHz. SENS 1034111. PRICEC73.34 - E4.00 PIP

r:FrEriTliri7PSRIZMIUT raliNgirgYNWro:ALL EARBENDER UNITS 8 OHMS (EAApl EBAS) A Eat 5.50 cancan. Ara 005 owes:A-co tax - 4 & 6 WAN)BASS, SINGLE CONE, HIGH COMPLIANCE, ROLLED SURROUND8" 50watt EBB -50 DUAL IMPEDENCE. TAPPED 4/11 OHM BASS. HI -Fl. IN -CAR.RES. FREO. 411Hz. FREO. RESP. TO 7KHz SENS 97dB. PRICE 08.90 - C2.00 P&P

50WATT EB10-50 DUAL IMPEDENCE. TAPPED CB OHM BASS, HI -Ft. I fl -C ARRES. FRED. 40Hz. FREO. BEEP. TO 5/(Hz. SENS. 99dB. PRICE t13.65 - C2.50 PIP

100WATT EB10-100 BASS. HI -Ft STUDIO.RES. FREO. 35Hz. FREO. RE SP. TO 3KHz. SENS 96dB. PRICE C10.39 - E3.50 PEP12" 100WATT EB12.100 BASS. STUDIO. EXCELLENT DISCO.RES. FREO. 26Hz. FREO RE SP. TO 3 KHz. SENS 93dB. PRICE [42.12 - C3.50 PAPFULL RANGE TWIN CONE, HIGH COMPLIANCE, ROLLED SURROUND

60WATT EB5-60TC (TWIN COHE)141*-1. MULTI -ARRAY DISCO ETC.RES. FREQ. 63Hz. FREO. RESP. TO 20KHz, SENS 92d8. PRICE 09.99 - CI.50 PAP6'.' 60WATT E116-60TC (TWIN CONE) HI -Fl. MULTI -ARRAY DISCO ETC.RES. FRE0.3511z, FREO. RESP. TO 20KHz. SENS SadB. PRICE C10.99 - 1.50 PAP8" 60WATT E88-80TC (TWIN CONE) HI -Fl. MILTI-ARRAY DISCO ETC.RES. FREO. 40Hz. FRED. RESP. TO 18101z, SENS 69d B_ PRICE C12.94 - C1.50 PAP10' 60WATT EB10-60TC (TWIN CONE) HI-FI. MULTI ARRAY DISCO ETCRES. FREO. 15Hz.FREO. RESP. TO 12Kfriz. SENS 55dB. PRICE 016.49 - C2.00 P&P

PRICES: 150W C49.99 250W C99.99400W C109.95 PEP C2.00 EACH

THREE SUPERB HIGH POWERCAR STEREO BOOSTER AMPLIFIERS150 WATTS gs 75) Stereo. 150WBridged Mono250 WATTS (125 - 125) Stereo. 250WBridged Mono400 WATTS (200 - 200) Stereo. 400WBridged MonoALL POWERS INTO 4 OHMSFeatures:* Stereo. bridgable mono Choice ofhigh A low level inputs a L 3 R levelcontrols 7 Remote on-ot1 w Speaker 3thermal orotettio

1E3POSTAL CHARGES PER ORDER E1.00 MINIMUM. OFFICIALORDERS FROM SCHOOLS, COLLEGES, GOVT. BODIES, PLC. ETC.PRICES INCLUSIVE OF V.A.T. SALES COUNTER. VISA AND

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Please mention ELEKTOR ELECTRONICS when contacting advertisers. 51

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ELECTRONIC HYPNOSIS PLANS & DATA Ttusilaia she. sseveral ways to put sutted under your control Included is a fuvcrurne reference text and several =rain/ Mich plans that whenassembled can produce Mg My effecave status Tres material mos:be used cautousty his for use as enternmlrt at panes Sootyby those emerlenced in its use. E15/set Ref F/EM2GRAVITY GENERATOR PLANS This unique plan

a single etecOlcal prieriome-na [hate reduces an art -g ref ty effect You can actuaay bolds small modrspacesho out clsimple matehaa and without any v;Stle m ears cause rt to tentathEt Wset Ref F,CFLAt

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Adjusting a satellite TVdish is often com-pared to finding a

needle in a haystack.Although the coarsesetting of the dish isfairly easy to find bylooking at the direc-

tion of nearby dishesin the street, you mayneed a lot of patience,

mechanical twid-dling and shouting

to and from theTV room beforethe first pictures

appear. The prob-lems are often

aggravated by thefact that you are

standing on a ladderor 'dangling' from abalcony. The instru-

ment described hereis simply connected to

the LNC output, anddoes away with the

need to actually seethe received picture.All you have to do is

watch the needle of amoving -coil meter,and peak the dish

adjustments for thehighest reading.

Battery -powered andportable!

Design by Christian Denolle, F1FAU

satellitefinder

DISMAAJUSTMENT

DE gAsy

Despite the ad-vice given by dish installers to

seek professional help when it comesto mounting and adjusting the 'out-door parts' of your newly purchasedsatellite TV kit, it is great fun, and in-structive, too, to tackle the matteryourself. The dishes for today's mostpopular TV satellites, Eutelsat andAstra, have a diameter between 50 and80 cm, and are relatively easy to in-stall yourself. In the past, disheswere much larger and, consequent-ly, much more difficult to erect andpoint at the satellite. The techno-logical advances made in LNC de-

signand construction have

brought satellite TV reception to themasses because they have alloweddished to become smaller for thesame quality of reception.

THE VARIABLESGetting tuned to those exciting satel-lite TV channels is all a matter of elim-inating unknown variables. To provethe general concept that 0.1% infor-mation is 'somewhere', hidden in99.9% noise, let's draw up a (worst -case) list of things we do not knowwhen we unpack the box.

Q/. Receiver tuning: you may be at'any' frequency between 950 MHz

A52 Elektor Electronics 3/96

and 2,000 MHz, or at 'any' of up to250 channels.Q2. INC polarization: this may hor-izontal, vertical, left-hand or right-hand circular.Q3. INC band selection: you don Iknow in which band you are (Eu-telsat/Astra/Astra-1D/DBS/Telecom).Q4. Re -modulator tuning:' vhat areyou actually receiving on your TVset? Note: this is not a problem ifyou are using a SC_ART link betweenthe receiver and the TVQ5. Dish position, horizontal plane('azimuth'): the theoretical range is180°!

Q6. Dish position, vertical ('eleva-tion'): the theoretical range is 90°!

Now, that looks pretty daunting. So,let's eliminate the variables one by-one. The first three points are easilysolved by consulting satellite chan-nel overviews which are publishedmonthly by specialized magazinessuch as What Satellite, and matchingthe information given with that pre-sented in -the -user manual that camewith your receiver.

Al. Most receivers these days comepre -:tuned- to- Astra, Eutelsat andHotBird channels. If not, make sureyou understand the tuning system,and calculate the receiver tuningfrequency.A2. Make sure you know the polar-ization of the station ('transponder')you wish to receive.A3. The same for the LNC band se-lection.A4. Switch the satellite TV receiveroff and on to make sure you havethe receiver's output signal (noise,probably) on your TV screen. Notethat FM noise (as supplied by the re-ceiver) is a little coarser or 'grainier'than AM noise which is normallyproduced by your TV set.A5 and A6. These two variables arepart and parcel of the outdoor unit, atleast, if you have a fixed -dish system.Adjusting a motorized dish with apolar -mount actuator is best left to theprofessional installer. Like the LNCband selection, the tuning frequencyand the polarization, the angles forazimuth and elevation for your loca-tion (Fig.1) may be found in pub-lished tallies. In the UK, the elevationwill be between 22' in the far Northand about 30' in the South. There arealso excellent computer programsaround which do perfect az/el calcu-lations for any location on the globe.

Fig. 1. A satel-lite TV dish hastwo angles toset: azimuth(horizontalplane) and ele-vation (verticalplane).

1

WEST,zr""

HITTINGTHE BEAMAssuming that yourreceiver and TV areset properly, a bigproblem still existsin the fact that you can't see the TVscreen from where you are on theroof or balcony. So you need a helperand/or a pair of walkie-talkies. If nei-ther is available, the only solution isto drag the TV screen within sight.Apart from the obvious problemsand perils caused by hauling even aportable TV set and a compact sat re-ceiver on to the roof, this solutionwill not necessarily give the best re-sults.

When you first hit upon the beamtransmitted by the satellite, the effecton the TV screen is very sudden andswitch -like, quite unlike the moregradual effect you may be accustomedto from tuning to terrestrial televisionstations. The suddenness is caused bytwo factors: (1) the use of FM modula-tion and (2) the small pointing angle ofthe dish. Once the signal strength ex-ceeds the so-called FM detectionthreshold, the TV signal changes sud-denly from almost invisible to crispand clear. The same with the dishangle: change it a little and you losethe picture almost instantly, althoughsome 'sparklies may appear if the sig-nal strength is just above the threshold(7 to 9 dB S N). Unfortunately, the factthat the picture is free from sparkliesdoes not mean that you have hit uponthe right dish position. You may be-come painfully aware of this duringheavy rain or snowfall, when sparkliesappeat and it's not Star Trek or the lat-est computer animation on the screen!

SIGNAL STRENGTHAlthough the quality of the receivedpicture is fine for an initial adjustmentof the dish, you should not miss outon those few extra dBs which are nec-essary to prevent sparklies under ad-verse weather conditions. The onlyway to squeeze out these dBs from the

.

AZIMUTH(A) 960041-14

system is to judge the signal strengthwith a dedicated meter rather than theTV set or monitor Peaking the dish ad-justments for the highest signalstrength as indicated by a meter willgive you the best possible reception,and some headroom in case of adverseweather conditions. Some satellite TVreceivers do offer a signal strengthmeter function, but it is difficult to usein most cases, being aimed at the pro-fessional installer. Alternatively, the sig-nal strength may be indicated by anon -screen horizontal bar, accessiblethrough the setup menu. Unfortu-nately, that's fancy stuff, and not muchuse either if you can't see the TVscreen from the roof!

ALL IN HANDThe present instrument consists basi-cally of a two -stage high -gain amplifi-er and a signal rectifier. The input ofthe amplifier is connected to the LNCvia a short length of coax cable. Thesignal strength is indicated on a claccicmoving coil meter.

The circuit diagram of the Satel-lite Finder is shown in Fig.1. Let'sfirst look at the power supply. Thecircuit and the LNC are powered bya pack of four series -connected 4.5 -volt batteries. The IS -V battery volt-age is fed to the LNC via switchesSi, S2 and choke Ll. Most, if not all,currently available LNCs are capa-ble of operating at 18V. Whetherthat voltage selects horizontal, ver-tical, right-hand or left-hand circu-lar polarization in the LNC is large-ly immaterial because most satellitestransmit enough signals in one po-larisation plane for the tester to de-tect and respond to. Do make sure,however, that the LNC receives thedesired band at 18V. Note thatswitch S1 must remain closed in the

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(rare) case of an LNB which is notpowered via its coax output.

The battery pack voltage also ar-rives at the input of a voltage regu-lator, IC3, which supplies a stable12-V rail for the amplifier blocks, IC1and 1C2, and the logarithmic meterdriver, T1. Current consumption ofthe circuit is only about 75 mA. De-pending on its make, the LNC maydraw anything between 100 mA and500 mA. An LED, D2, is used as anon/off indicator on the instrument.

The output spectrum of mostLNCs extends from 800 MHz toabout 2,000 MHz. The signal levelsare generally high, given that mostLNCs have a conversion gain in ex-cess of 60 dB. That is still notenough, however, to enable a simple(passive) rectifier to be used in com-bination with a moving -coil meter.Hence, more gain is required, forwhich IC1 and 1C2 are responsible.Each of the type MAR8 monolithicdrop -in amplifiers supplies a solid 15to 20 dB of gain. The MARs are cas-caded, and operated at their typicalsupply voltage of about 7 V, which isapplied via series resistors R5 andR6. Note that the supply voltage ofIC1 is adjustable with pot P1. That isdone to enable the gain of the first

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amplifier to be reduced within a rea-sonable range to prevent overload-ing of the meter circuit.

It should be noted that the MAR -8,unlike its family members, has aninput and output impedance whichis higher than 502 The actual valuedepends on the frequency. Fortu-nately, that is not a problem here be-cause of the high signal levels, andbecause the there is plenty of gainto compensate small mismatches.Low noise is not a point, either!More on MAR amplifiers may befound in the inset and in the Refer-ence at the end of this article.

The rectifier is formed by a Schot-tky diode, Dl. If difficult to obtain,the H P2800 may be replaced by alower -spec type such as the BAT82.

The meter driver is conventionaland based on a HT (T1) which en-sures a partly logarithmic meter re-sponse. The meter is nulled with potP2. Absolute readings are not inorder, so a scale is not really neces-sary on the meter. All we are after isa well-defined peak in the meterreading, and that's exactly what thecircuit will give you, provided youare able to point the dish at the satel-lite.

Fig. 2. Circuit diagramof the Satellite Finder.The crucial elementsare two MAR8 drop -ingigahertz amplifier ICsfrom MCL.

L

ILDING ITThe Satellite Finder is best built on asmall printed circuit board of whichthe design is shown in Fig. 3. Becausethe board is not available ready-made through the Readers services,you will have to make it yourself, orhave it made. The board is double -sided, but not through -plated. Thetop side of the board acts as aground plane.

It's a wonderful fact that this cir-cuit has no adjustable inductors oresoteric parts to contend with, al-though it operates in the gigahertzfrequency range. The only inductorin the circuit is a small choke, Ll,which consists of three turns of 0.3 -mm dia (30SWG) enamelled copperwire (e.c.w) through a 3 -mm longferrite bead - see Fig. 4. The only'problem' with the MARS is thatthey are, well, tiny!

The NLkRs are fitted at the under-side of the board. Check the orienta-tion: the dot on the device marks theRF input. The two electrolytic capac-itors, CI and C15, are mounted about2 mm above the board surface to en-able their negative terminals to besoldered to the copper ground planeat the top side of the board.

For proper screening, the com-pleted board must be fitted in asmall metal case. The case is bestmade from a 30 -mm wide strip of tinplate which is bent around the boardedges (see photographs). Do not sol-der the seam before you have deter-mined the position of thefeedthrough capacitors which are fit-ted in one of the side panels. Thesolder eye of the feedthrough ca-pacitor should be at the outside ofthe case. The collar is soldered allaround to the side panel using amedium -power sodlering iron. De-pending on what you have avail-able, the RF input socket, Kl, is ei-ther a 'BNC' (flange) type or an 'F'socket. Although the latter is cheap-er, it may be more difficult to gethold of. It is also less suitable for fre-quent connection and disconnection,so we really recommend using aBNC socket. You will also need tomake a short coax cable to connect


the tester to the LNC. This cable ha=an F plug at the LNC side, andBNC plug at the side of the tester.The flange of the BNC socket is ei-ther soldered or screwed to the tin-plate panel, and the centre pin issoldered directly on to the RF inputpad on the board. If necessary, re-move the PTFE collar around thecentre pin with a sharp knife.

The completed tin-plate case isbuilt into a diecast enclosure (whichmay also contain the battery pack).The front panel holds the moving -

coil meter, the two LEDs and thecontrols (two pots and two switch-es). The controls are connected tothe respective feedthrough capaci-tors via short wires. If an externalbattery pack is used, it is connectedto the tester via a low -voltage d.c.adaptor plug and socket.

PRACTICAL USEEasy, as far as the tester is con-cerned! Connect the tester to theLNC with the home-made cable.Flick the two switches, the LEDshould light. The meter may showsome indication already. Check thatthe indication varies if you turn potPl. Null the meter by turning pot P2with the LNC switched off (51).

The meter needle will show amarked peak if you hit upon thesatellite beam. Once you have foundthe initial dish position, reduce the

I R3 I

WEE

0

rl2-00

gain by turning P2, and then adjustthe dish again. In this way, you willbe able to obtain the best possible re-sults from your outdoor unit. (96ottin

Reference:'Using the MAR -x series of very wide-band monolithic microwave integrat-ed circuits (MMICs)', by Joseph CarrElektor Electronics October 1992.

Fig. 4. A close look atthe prototype of thesatellite finder. Noticethe feedthroughcapacitors and thesmall ferrite bead.

ru

0 0

0

" 2

0

0--0--0 0 00

0

I 000 00° Ct) -

0 iN0 0(' pittO

"x;00000

000CC) 0 X'. 0

>>00

oo 441008

Z-_5()°)

Fig. 3. Printed circuitboard design (boardnot available ready-made through theReaders Services).

COMPONENTS LIST

Resistors:R1,R5,R6 = 1509R2 = 109R3.R4 = 3309R7 = 4k9.7R8 = 1MQR9 = 4709R10 = 1kR11 = 2k92R12 = 8209P1 = 4709 potentiometerP2 = 1k9 potentiometer

Capacitors:C1 = 100pF 25V radialC2-C6,C16,C17 = feedthrough

capacitor 1nFC11,C12,C18 = 1nFC7 = 10pFC8,C9,C10 = 3pF3C13 = 100nFC14 = 10nFC15 = 22nF 25V radialC19 = 2pF2

Inductor:L1 = 3 turns 0.3mm dia. e.c.w. on

3mm ferrite beadSemiconductors:D1 = HP2800 or other RF Schottky

diode (e.g. BAT82)D2 = LEDT1 = BF245BIC1 .IC2 = MAR8 (Mini Circuits

Laboratories)IC3 = 7812

Miscellaneous:Ki = antenna socket (with flange)

(see text)S1,S2 = on off switch.BT1 = four 4.5V batteriesMl = moving coil meter. -ImA f.s.a.

Elektor Electronics 3'96 55

reMARkable wideband RF amplifiersMAR devices from Mini Circuit Laboratories are remark-able because they make RF amplifier design accessibleto anyone. MARs are cheap, easy to use and pretty fault -tolerant. These wonderful four -pin devices match 50-Qinput and output impedances without external impedancetransformation circuitry (which is normally a nightmare tobeginners). They are basically silicon bipolar monolithicICs in a two -transistor Darlington configuration, internallylaid out for ultra -low stray inductance and capacitance.Depending on the exact type, the overall gain of thesedevices is typically 13 to 33 dB between d.c. and about2 GHz (yes!). Some types are optimized for low noise,others, like the MARE, for very high gain.

RF RF

n4

RF

960041 - 1213

RF R

Internal schematic of MARamplifier, circuit symbol anddevice package.

In the basic circuit for a wideband amplifier based on aMARx device, the RF IN and RF OUT terminals are pro-tected against d.c. by coupling capacitors Cl and C2.Also traditional is the supply decoupling consisting of atantalum electrolytic capacitor (C4) and a ceramic 100-nF type (C3). The amplifier is powered via a seriesresistor which determines the operating voltage, asshown by the formula. The operating current for thedevice used may be found in the datasheets, and willbe of the order of 40 to 80 mA.

v+

SWO4i - 13

Generic MAR -x circuit.


RD

S D

emod

ulat

or +

Filt

erT

DA

7330

RF

and

Vid

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LgE

igff

ugav

zoro

voz

KT

DA

TA

SH

EE

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/96

Man

ufac

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r: S

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-Tho

mso

n

The

TD

A73

30 is

an

RD

S (

Rad

io D

ata

Sys

tem

)de

mod

ulat

or. T

he IC

incl

udes

a 5

7 -k

Hz

switc

hed

capa

cito

r in

put b

and

pass

filte

r, a

bit

rate

clo

ckre

cove

ry c

ircui

t, D

SB

dem

odul

ator

circ

uit.

bi-

phas

e P

SK

dec

oder

, diff

eren

tial d

ecod

ing

cir-

cuits

, AR

I ide

ntifi

catio

n an

d si

gnal

qua

lity

out-

puts

. The

dat

a an

d cl

ock

outp

ut s

igna

ls (

RD

DA

,R

DC

L) c

an b

e pr

oces

sed

furt

her

by a

sui

tabl

e

mic

ropr

oces

sor.

Abs

olut

e m

axim

um r

atin

gs:

Sup

ply

Vol

tage

:

Ope

ratin

g T

empe

ratu

re R

ange

:

7V-4

0 to

+85

'85

°C

Fea

ture

s:

A: H

igh-

perf

orm

ance

, sta

ble

57 -

kHz

filte

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t -fr

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dem

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nw

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c? A

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outp

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4.3

32 -

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w -

nois

e m

ixed

bip

olar

/CM

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tech

nolo

gy

Blo

ck D

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am

Pin

Con

nect

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nuxr

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MP

MO

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T3

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T

OS

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70 151

10 17 16 15 11 13 12 11

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T

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CA

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CL

157

Pin

Nam

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RD

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put s

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l

2V

RE

rR

efer

ence

vol

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3C

OM

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on -

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g co

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(sm

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Fill

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5G

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und

0T

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est o

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t (no

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Tes

t out

put M

at u

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9O

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scill

ator

out

put

10O

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INO

scill

ator

inpu

t11

T57

Tes

t out

put (

not u

sed)

12R

DC

LR

DS

clo

ck o

utpu

t

13R

DD

AR

DS

dat

a ou

tput

14()

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LS

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l qua

lity

outp

ut (

high

= g

ood)

Out

put f

or A

RI i

ndic

atio

n15

AR

I(h

igh

- R

DS

+ A

RI o

r A

RI o

nly,

low

= R

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only

, und

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ed w

hen

no s

igna

l pre

sent

)

18V

ccS

uppl

y V

olta

ge

17T

2T

est o

utpu

t (no

t use

d)18

FS

EL

Fre

quen

cy s

elec

tor

pin

19T

MT

est m

ode

pin

(ope

n =

nor

mal

run

,cl

osed

to V

CC

= T

est m

ode)

20P

OR

Res

et In

put M

r te

stin

g (a

ctiv

e hi

gh)

Ire

IRE

Am

plifi

ers

MA

R -

x

RF

and

Vid

eoL

IN

CIr

LE

C)

ffi L

100

DA

TA

SH

EE

T03

/96

RF

Am

plifi

ers

Man

ufac

ture

r: Min

i -C

ircui

tsT

he M

AR

-cas

cada

ble

ampl

ifier

ser

ies

is a

fam

ilyof

sili

con

bipo

lar

mon

olith

ic In

tegr

ated

circ

uits

fabr

icat

ed w

ith n

itrid

e se

lf -a

lignm

ent,

ion

impl

an-

tatio

n fo

r pr

ecis

e co

ntro

l of d

opin

g an

d pa

ssiv

i-sa

tion

to a

chie

ve h

igh

relia

bilit

y. T

hese

dev

ices

,pr

iced

from

bel

ow o

ne d

olla

r in

vol

ume

quan

tity,

exhi

bit e

xcel

lent

uni

t -to

-un

it un

iform

ity a

nd a

reid

eally

sui

ted

as 5

0 -o

hm a

mpl

ifier

bui

ldin

gbl

ocks

. The

MA

R d

evic

es a

re s

impl

e to

use

if

the

prop

er b

oard

layo

ut Is

use

d, a

long

with

prop

er g

roun

ding

, bia

sing

and

ste

ps to

min

imiz

epa

rasi

tics.

Min

i Circ

uits

, P.O

. Box

350

166,

Bro

okly

n, N

ewY

ork

1123

5-00

3.

App

licat

ions

: L

ow -

pow

er tr

ansm

itter

A. B

oost

sig

nal f

or Im

prov

ed d

etec

tor

effic

ienc

yM

ulti

-sta

ge a

mpl

ifier

cha

inB

uffe

r am

plifi

er fo

r os

cilla

tors

Isol

ator

Fea

ture

s:

Eas

y to

use

, 50-

a. in

put/o

utpu

tS

moo

th r

espo

nse

over

the

band

, no

exte

rnal

reso

nanc

es

.7 E

asy

for

prin

ted

-circ

uit d

esig

ns, o

ne In

put

and

one

outp

utC

an o

pera

te a

s lo

w a

s 5

Vdc

-7 L

ow Im

peda

nce,

less

sus

cept

ible

to E

MI

Cas

e:

VV

1 05

nee

15 Pin

Fun

ctio

ns:

Nam

e

HO

T n

tuN

i.t55

am

t./m

ine

siT

C01

501

In1

k010

0005

Aim

2T

oLill

Aw

Crn

7:

!Ai! -

Ij

eIe Ile

-

IN

GN

D

3R

F O

UT

GN

D

Fun

ctio

n

RF

Inpu

t

Gro

und

RF

out

put a

nd b

ias

Gro

und

hilu

rnal

Sch

emat

ic:

0

RF

Am

plifiersM

AR

-x

RF

and Video

11ffraffLt'itreO

ttD

AT

AS

HE

ET

03/96E

lectrical Characteristics:

mum

No.

Max.

Freq.

1611r111)11

Typ. G

ain KIB

I

Max. P

ower, dB

m

Color D

elO

utput (1d0)C

ompression

Input(nu dam

age)1000

2000M

in

MA

R -1

tll OV

VII

15.5III II

1111

MA

R -2

rod2

1312.5

118.5

4.3+

15

MA

R -3

orange2

1312.5

10.58.0

+8

+15

MA

R -4

yellow1

8.28.2

8,07.0

+11

+15

MA

R -6

while

220

1916

119

+15

MA

R -7

vlolet2

3,513,1

12.510.5

8.5+

4+

15

MA

R -8

blue1

3326

2310

+10

+15

Dynam

ic Range

Intercept pt. IdBinj

V8W

RM

ax. Rating

1125 °CD

C pow

er at Pin 3

NF

[dBJ

typ.

3rd order

typ.In

Out

I [mA

]P

Im1N

1IIm

AJ

U 1111

MA

R 1

5.015

1,5:11.5:1

4060

10017

5

MA

R -2

6.518

1.3:1

1.6:1325

25

MA

R -3

6.023

1,6:11,6:1

70400

355

MA

R -4

7.027

1.9:12:1

85500

505

MA

R -6

2.815

2:11.8:1

50200

163.5

MA

R -7

5,02:1

1,5:1275

224

MA

R -8

3.53:1

3,1500

367.5

Am

plifierB

ias Current

Bias V

e tapeItc (approx.)

le InlAl

+110

+5V

+9V

+12V

+15V

MA

R -1

17-5

-235

412588

MA

R -2

25-6

-160

280400

MA

R -3

35-5

-114

200286

MA

R -4

50-6

-60

120180

MA

R6

16-3.5

98344

531719

MA

R -7

22-4

45364

500

194M

AR

-836

-8___227

111

Cairulahun 01

Rc =

(Vrr -

au itzlw

hine

Vce:

Supply voltage applied to R

C IV

)

v,,V

oltage at the supply terminal of the M

MIC

IV)

1,1:O

ulescent bias current (Al

The dissipation of H

e Is given by

Palm

= Id2. R

C K

2 I

Typical C

ircuit Arrangem

ent:

color dot

IN

Nrc

TV

I KU

Juem

oomaior -t- P

urerT

DA

7330Lgi LiglE

-UC

NL

Efft1--,ffaV

IEC

i-i1A,.:L

ic.fi:::R

F and V

ideoD

AT

AS

HE

ET

03/96E

lectrical characteristics :-

(Vcc

- 5 V, T

ow,

, 25 "C, lute -- 4.332 M

ilt, V1N

= 20 m

Vut. unless otherw

ise sPec111011)

Sym

bol Param

eterT

hat Cotillion

Min.

1y p.M

ax.U

nit

Supply

vccS

upply Voltage

4.55

5.5V

IsS

upply Current

9m

A

Filler

Fc

Centre F

requency56,5

5757,5

kHz

2.53

3.5kH

zB

W3 -dB

Bandw

Ilh

1 c 57 kHz

1820

22dB

GG

ala

Attenuation

At =

.:t 4 kHz

I in 38 kHz, V

1 w 500 nitirm

.4

I = 87 kH

z, Vi .. 250 m

Vnor,

18

5035

228050

dBAA

Ph

Phase non -linearity

A"

IPC*

0,512

.

57.510

DE

G

Input Impedance

100160

200K

U111

S/N

Signal to N

oise Ratio

vi ., 3 mV

om,

3040

dB

VI

Input Signal

I = 19 kH

z. T3 s 40 dB

**1 =

57 kHz (R

DS

+ A

RI)

I50vm

,W

ens

RL

Load Impedance

Pin 4

100kit

Limiter

RA

Resistance P

In 3.415

2'128

kfa

Oscillator

roseO

scillator Frequency

FsE

1 = O

pen (Internal 40-kg-Pull-dow

n-Resislor.

with 4.332-M

Hz-D

uarz)

FsE

L w to V

ac (with 8.664-M

Hz-O

uarz)

4.332

8.664

MH

z

Dem

odulator

snos1R

DS

Detection S

ensitivity1

rriVrm

s

SA

RI

AR

I Detection S

ensitivity3

rTIV

rins

Track

RD

S Lock tim

e100

ms

Von

Output H

IGH

Voltage

IL .r. 0.5 mA

4T

.,

VO

LO

utput LOW

Voltage

IL = 0.5 m

A1

V

hipsD

ata Rate for R

DS

1187.5H

z

: The phase non -linearity Is defined as .A

Ph =

I-2'142 + 1141 +

+13 I

, where 414x is the output -Input phase

difference al the

frequency lx (x = 1

2.3).

--Measurem

ent11 (kH

z)12 (kH

z)13 (kH

z)A

Ph m

ax.

A56.5

5757.5

<5^

856

5758

<7.0"

C55,5

5758.5

<10"

' T

he 3rd harmonic (57 K

Hz) m

ust be less than -40 dB w

ith respect to Input

signal plus lain./

opLC

)

PCB DesignerFor Windows 3.1, '95 or N

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au- 46114 MA. 411.14 WO Zia-1,4,6,M112.1Iffee=11M1111=0ONION 4.1.

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0,411=1M

r

Most surround -

sound installationsuse loudspeakerboxes of modest

dimensions so as toavoid making them

too obtrusive for theusual living room.

The consequence ofthis is a limited bass

response, whereasespecially the low

frequencies can pro-vide impressive

effects with a goodsurround -sound sys-tem. To counter thisdrawback, the bass

response can beenhanced with the

subwooferdescribed in thisthree-part article.

Design by T. Giesbert'

Surround sound, the popular audiocraze of the past few years, can pro-vide an impressive combination ofsound and picture when it is used inconjunction with a Tv set. Good -qual-ity spatial sound is provided by anumber of loudspeakers (usually five)located in front of and behind the lis-tener(s). Five loudspeakers present aproblem, of course, in that they takeup a lot of space in the average livingroom. To keep the space occupied bythem to a minimum, the loudspeakersare often fairly small. Moreover, ineconomy -price systems, cost is impor-tant, too, and this also tends to keepthe boxes small.

Unfortunately, small loudspeakerboxes are detrimental to good bass re-production. On the surface, this maynot seem such a terrible thing in anaudio-visual system until it is realizedthat the low frequencies contain spa-tial information. Moreover, we per-

ms

part 1

ceive low frequencies not only via ourears, but also through our entire bodyand this causes good low -frequencyreproduction to give that added feel-ing of reality to the sound. All thismakes it clear that the importance oflow frequencies must not be underes-timated.

The reproduction of low frequen-cies requires the displacement of largevolumes of air. This in turn means thata large low -frequency drive unit(woofer) should be used. But such aunit must be contained in a large en-closure to enable it to reproduce lowfrequencies effectively. And this iswhere the crux of the nutter is: mostliving rooms just do not have thespace for such a large box.

In the subwoofer described in thisarticle an attempt has been made tofind a compromise between the con-tradictory requirements just outlined.It uses a large (300 mm) drive unit

Technical dataDrive unit

Dimensions of boxVolume of boxType of boxNominal impedanceEfficiencyFrequency rangeLoading

300 mm (8 in), e.g. Monacor (SPH-300TC); KEF;Radio Shack (40-1024); Parts Express (295-240)660x406x420 mm (26x 16x /6 "t46 in) incL legsabout 65 setbass reflex8 LI per channel88 dB W-1 rn-145-105 Hzmax 250 W per channel

Elektor Electronics 3.96

housed in a modestly -sized enclosureof 65 1 The enclosure is designed inthe form of a side table with the driveunit fitted between the legs so as tomake it (virtually) invisible. The vol-ume of the enclosure is not reallylarge enough for very low frequencyreproduction, but a solution for thiswill be published in next month's in-stalment. This consists of an active cor-rection network and associated am-plifier that bring the -3 dB pointdown to 20 Hz. This article describe,the passive version of the subwooferwhich can be used without any diffi-culties with existing apparatus. Its fre-quency range extends from about45 Hz to 105 Hz. The upper frequen-cy and the efficiency of the unit pro-vide a good match with the (smaller)front loudspeakers.

Although so far reference has beenmade only to a surround -sound sys-tem, the subwoofer may, of course,also be used with a standard stereosound system.

THE (PASSIVE)DESIGNThe design is based on a 300 mm (8 in)Monacor SPH-300TC drive unit, butother makes, such as KEF, Radio Shack(40-1024), or Parts Express (295-240)should give good performance as well.The .SPH-300TC is a relatively inex-pensive unit with a fairly large magnetthat displaces a volume of around 0.2 1Its parameters make it suitable for usein a bass reflex enclosure.

If the loudspeaker is to be usedwith a stereo system, it should haveconnections for both channels. Thismeans that either two drive units or adrive unit with dual voice coil shouldbe used. Each voice coil is connectedto one of the channels via a suitable fil-ter The present design uses the lattersolution, since the use of two driveunits would make the box unneces-sarily large.

The alignment of the enclosure isdetermined with the simulation pro-gram Boxcalc, and aims to arrive at acompromise between a (relatively)small volume and a low -3 dB point.This results in a 65 'box with the pipe(acoustical resonator) tuned to 23 Hz.The overall frequency response isshown in Fig. 1. The -3 dB point is at45 Hz, which, considering the smallbox volume, is pretty good. The -3 dBpoint is low enough to allow the sub -woofer to be used as a passive unitwith most existing systems.

1 Transfer Function Hag - an SPL,uolts (0.30 oct)

100.0 - --

95.0 17

90.0

85.0

80.0

75.0

70.0-

65.0-

60.0-55.0

50.0

auto

10.0

THE FILTERSince the design aimsat keeping the costs aslow as feasible, the(passive) filter has been kept as simpleas possible, which, in the case of a sub -woofer, is not as easy as it may seem.

The impedance characteristic of thedrive unit is shown in Fig. 2. The twovoice coils are connected in parallel toobtain a reliable curve (which meansthat for each coil double the imped-ance value must be taken). The curveshows two peaks. The lower one atabout 10 Hz results from the bass re-flex. augment (which.. by the way, is,exactly in line with the 23 Hz res-onator). The second peak, just above30 -Hz, is caused by the resonance fre-quency of the drive unit in the box.

Normally, filteringof a subwoofer starts ataround 100 Hz orslightly lower to ensuregood matching withthe standard stereo

100.0log Frequency - Hz

Fig. 1. The frequencyresponse curve of theSPH-300TC in a 65bass reflex enclosuretuned to 23 Hz.

22.0-

16.0-

14.0-

12.0,

10.0

8.0

4.0,

2.0

auto

11

A

1000.0

960038-11

loudspeakers. A passivefilter, however, has thedrawback that it func-tions properly only if it

is terminated into a pure resistance. Ifthe cut-off point were chosen at100 Hz, the 52 Hz peak would create aproblem: the resulting overall curve ofa theoretically computed filter wouldnot be usable. To solve this problem,the impedance curve of the drive unithas to be corrected. This is often ef-fected by connecting parallel across itsterminals (for each channel) an RLCnetwork with the same resonant fre-opon.quencies, the values of the necessaryinductors and capacitors are such thatthey result in physically large (and ex-pensive) components.

The solution in thepresent design consistssimply of shunting thevoice coil with a resistorThis does not totallyeradicate the peaks, but

Fig. 2. The impedancecurve when the twovoice coils are in par-allel. The high peakposes a problem forthe passive filter.

Inpedance Magnitude -

1.0.0 1 oi)p . o

log Frequency - Hz

1000.0

960036 - 12

Elektor Electkonlcs 3/96 63 6,

LI

flattens them suffi-ciently to enable a

simulation pro-gram-Calsod-correcting the fil-ter such that it -frequency re-sponse is close torequirements.

To keep the number of compiment-small, the filter is a second -order typeconsisting of conductor L1 and capac-itor C1 (see Fig. 3). The resistor in se-ries with the capacitor damps the LCcircuit to some extent. The effect of thefilter is shown in Fig. 4. Although thehigh cut-off point is about 105 Hz, theresponse will ensure a good match tomost small loudspeakers.

1360338 - 13

Fig. 3. The filter hasbeen kept simple.Resistor R2 corrects 1

the impedance curve.Inductor Ll andcapacitor C1 provide aslope of 12 dB peroctave and a high cut-off point at about105 Hz.

BUILDING THE BOXThe prototype box is made from28 mm thick medium -density chip-board (MDF), but, as in some cases itmay not be possi-ble to obtain this,22 mm thick chip-board may beused (note that thedimensions in Fig.5 must then be

Amu .0 -

v.0 -90.0 -

lS,.0 -

,0 .0

ru.06=1.0

60.0

-

adapted as appropriate).The box consists of six rec-tangular sheets and a stiff-ening crosspiece which arefirmly fixed together with asuitable heavy-duty glue.

At one side are theapertures for the drive unitand acoustical resonator.The resonator consists of a365 mm long piece of80 mm dia. PVC pipe avail-able from a builders mer-chant.

The four bananasockets for connecting thecables from the amplifier arefitted at the bottom of theone of the side panels.

The box is designedto rest on four 50 mm highlegs with the drive unit fit-

ted at the bottom facing the- floor ofthe living room.

After the glue has dried thorough-ly and the material has been sand -pa-pered, the box can be given a final coatto individual taste.

The box is half filled (up to thecross piece) with suitable loudspeakerwadding, but take care that the open-ing of the pipe remains reasonably freeof it

The filter components are availablefrom a specialist audicohi-fi retailer ora good electronics shop. The inductoris a 15 mH type with a 56 mm ferritecore, preferably an HQ56 from if The

capacitor is a bipolar typewith smooth terminals.

The filter compo-nenN may be glued to asmall sheet of wood,chip-board, or prototyping boardand then wired together.

Fig. 4. The frequencyresponse of the loud-speaker and filtercombination. Itensures correctmatching to mostsmaller stereo loud-speakers.

iranster function nag - On SYL/1101tS 111.3U OCtJ

Note that some retailers stock general-purpose filter boards.

Screw the completed filter into thebox and wire it up as shown. Take carenot to interchange the plus and minusconnections to the two channels. Thecables to the drive unit must be termi-nated into cable clips to avoid the ne-cessity of having to solder to the driveunit terminals.

Place the resonator in position,make the connections to the drive unit(make sure that the connections to the+ terminals match, otherwise thedrive unit does not work). Finally,place a strip of draught -excluding tapeunder the rim of the drive unit andscrew the unit to the box.

Some constructors (or their wives)may find it aesthetically pleasing toplace a sheet of glass, marble or simi-lar material on top of the box to give itthe look of a side table.

The passive subwoofer is thenready for use. It may be connected inparallel with the existing stereo speak-ers. It will work most satisfactorilywhen its efficiency of about88 dB W-1 m-1 corresponds roughly tothat of the existing loudspeakers andit is placed in dose proximity to these.Note that if you want the active ver-sion, which will be described nextmonth, you do not need the passivefilter; the box remains the same.

vea-.R4

SA

log irequency - Hz

64

960038 - 14

Elektor Electronics 3;96

Drive unit revisitedDuring the design of the loudspeaker, a thor-ough search was made for a 300 mm driveunit at a reasonable price (to keep total costsdown to not more than £ 80-90). Of course,such an economy -price unit cannot be expect-ed to be perfect. And, indeed, in the testing ofthe SPH-300TC unit, it appeared that the para-meters stated by the manufacturer did notagree with our own measurements.Fortunately, the deviations were beneficial tothe box dimensions. Also, there was a kind ofrustling noise at large cone movements. Thiswas suspected in the first instance to becaused by a loose cone or air leak, but a sec-ond example exhibited exactly the same noise.A detailed investigation showed that the dusthood in the cone (the convex cap that closesthe upper side of the cone) was the culprit. Itsmaterial is fairly soft, so that at large conemovements it begins to vibrate at its own(higher) frequency and thus causes therustling noise. This deficiency is easily negat-ed by spraying the dust hood a couple oftimes with a suitable plastic spray or applyinga few layers of a suitable cone impregnator.This makes the cap more rigid so that it is notset into vibration at large cone movements.The Parts Express unit appears to be rathermore rugged than the Radio Shack and israther cheaper.

A

Tri

Fig. 5. The enclosurehas been designedsuch that it may beused as a side table inwhich the drive unit isnot (or hardly) visible.

a_9

y.

14.

.940:111913

VINEASCAS

SCALE .


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ELEKTOR EI.ECTRONICS MARCH 1996

LettersComponent availability

Dear Editor-I recently decidedto build a decent hi-fi amplifierand chose a design by MrGiesberts (September 1995). Ihave several problems whichneed to be resolved which. Ifeel, should not have arisen ina magazine for the amateurconstructor who would have alimited number of sources forcomponents.1. 10000 pF, 50 V capacitors.The PCB layout requires a

30 mm dia. component (a35 mm dia. type will foul othercomponents on the PCB, but is

more commonly available.After much searching. I foundthree manufacturers: Etna,Dubilier and Rubycon. The dis-tributors for Elna seem to stockonly the 35 mm dia. size(although Elna do both 30 mmand 35 mm); the Dubilier itemrequires a £250 minimumorder. The Rubycon items arestocked by C&CD of Lane End.Bucks (01494 882848). partnos 50USP10000MC40

(40 mm long and 5.02 A ripple)and 50MXR10000MC50

(50 mm long and 4.05 A rip-ple). Note that the professionalMaplin catalogue advertises a30 mm item, but this is a typo:it should be 35 mm.2. IGBT output devices. Thesetransistors are single sourcefrom Toshiba and are not com-monly stocked by their fran-chised distributors. A non -fran-

chised distributor, Steatite(0121 643 6333. contact JennySkinner) is the only stockist inthe UK according to Toshiba.3. E96 resistors. Are some ofthe designs by Mr Giesberts socritical that only resistors fromthe E96 range can be used?May I refer to Lindsey -Hood,

Douglas Self. Bengt Olsen, et

al. whose state-of-the-art hi-fiamplifier design (EWW) seems

only to use the E24 range ofresistors.

4. Fischer SK84 heat sink.The parts list states that thethermal characteristic of theheat sink required is 0.6 KThe photograph in the Sept. 95article shows a heat sink where

the height is half the width ofabout 75 mm. In the Fischercatalogue No. 12, page A21,the graph clearly shows that fora stock length of 75 mm thethermal characteristic is about1.15 K W-1. Which is correct.0.6 K W-1 or 1.15 K W-1?

5. Screw terminals. Where,oh where, does one get the PC -B

mounted screw terminals onthe main amplifier Poa for thesupply and speaker leads inthe uic?

6. Single or twin powersupply? It is surprising thatconsideration has not beengiven to the power supply con-struction and ratings with asuitably rated Poe (twice the

current and twice the numberof reservoir capacitors?) for astereo unit.7. Terminal pin hole size.What size are the holes for theterminal pins which are usedfor connecting wires to andfrom the Pca? The holes usedare too large for commonlyavailable (Vero) pins which arenormally 1.04 mm. Where can I

source the correct size push -fitpin?

8. Tone controls. I recentlyenquired abut tone control cir-cuits for use with this amplifierand received the curt reply thattone controls are 'out' asthough they re some fashionaccessory and are no used in'real' hi-fi amplifiers. Firstly, I(an no doubt many otherreaders) still have older record-ings which need judiciousadjustment of the bass d trebleresponse to compensate forthe poor quality recording.Secondly, I do not have a spe-cially laid -out 'listening room',but a small living room in whichanything larger than my Ksp101

loudspeaker would be out ofplace. Thirdly, I am in my latefifties and in common witheveryone (younger hi-fi purists.please note), my hearingfrequency range has reducedas I have got older, so I dosometimes need to 'tweak' thetreble a little bit. Fourthly. thestatement that tone controlsare not part of the hi-fi scene isbased on the assumption thatthe recording engineer has car-ried out hisfher task to perfec-

tion and that the equipmentused in the studio is beyondreproach. Last, but not least, Iobject strongly to some hi-fi fol-lower of fashion telling me howI should listen to my(mostlyclassical and some R&B)muslc!

By the way, it would be a fal-

lacy to assume that reducedhearing frequency rangeequates to reduced sensitivityto distortion.

I feel that information on thesourcing of suitable compo-nents in the UK is sadly lacking.

The assumption by the conti-nentals that the hobbyist in theUK has access to instant knowl-

edge of where to get any com-ponent dreamt up by thedesigner seems not far short ofarrogance.

I feel that Elektor Elec-

tronics should set the standardhere by issuing guidelines tocontributors to use compo-nents that are commonly avail-able world-wide. The magazinecould suggest that designersonly choose components froma list of Elektor Electronicsdefined distributors that areavailable for the hobbyist bothon the Continent, in the uK and

in the LISA, and that specialist

components are source identi-fied by the contributor.

[Alan Beaman, Bracknell]

1 & 2. Many electronics retail-ers, including our own advertis-ers, are provided with a pre-view, incl. parts list, of the mag-azine content about threeweeks before the publishingdata of the magazine to enable

them to obtain stock of partsused. The preview states themanufacturer or other source ofany less common device.Mr Giesberts comments as fol-

lows:

3. 'When matched transistorsare used, 1% tolerance compo-nents are necessary. otherwisethe use of matched compo-nents would make no sense.The E24 range is, theoretically,

a 2% -tolerance series. In prac-

tice, however E96 will be sup-plied even if the same value is

found in the E72 series. It istrue that 1% resistors may befound in the E24 series. Unfor-

tunately, kits often contain 5%

types. obviously since theseare cheaper It is always possi-ble to use E24 types even ifE96 types are specified as longas one is prepared to accept aslight degradation of quality".4. in Fischer catalogues up to1993, a wrong graph wasprinted with the data for thesx85 heat sink. From the 1994

catalogues onwards, it is staledthat an sk85 heat sink is 75 mmhigh and has a thermal resist-

ance of about 1.2 K W-1. The

13u, value indicated in our parts

list should have correspondedto that value. In practice, a dou-bled thermal resistance dos noharm, because the design isbased on a worst -case situa-

tion. Nevertheless, it is recom-

mended to use a heat sink thatmeets the specified thermal

resistance rating".5. "A possible solution, better

than the original one, is to ter-

minate the cable into a cableeye and secure it with a screwdirectly at the copper side'.6. "To prevent earthing loops(which cause hum), a monosupply is recommended. Foranyone who is after quality, the

possible cross -effects that a

stereo supply may have on thetwo channels, the wiring (a'star' configuration is not ideal)and particularly the radiation of

the supply cables are goodreasons to make use of a monosupply. In fact, it is better tobuild two mono amplifiers".7. it is better to make use ofsoldering eyelets, which nor-mally have a wedge".

Finally, we apologize for the

curt reply you got to your queryon tone controls. We fully shareyour feelings that in manycases tone controls are notonly required, but are essential.

Nevertheless, some amplifierswe publish have no tone con-trol and these are aimed espe-cially at readers who do notfeel a tone control is necessary,

[Editor]

Electronic magazinesDear Editor-By all meansmake your publication avail-able 'electronically' for theanorak wearing minority ('Let-ters' -F R Fattori, Dec 1995).

A 68 ELEKTOR ELECTRONICS MARCH 1996

But please continue to presentit properly for those of us whostill live on the surface of theplanet.

It is one thing to read a let-ter on screen. Reading a tech-nical article, where it is necess-ary to frequently refer to differ-ent pages as one proCeeds isquite another. The only feasibleway to read an electronic ver-sion of a magazine such as

yours would be to first print outthe whole thing! In which caseit might as well be on the moreflexible medium in the firstplace.

I suspect that the demise ofglossy magazines is as far offas the long predicted paper -less office - which is still furtheroff than it was when paper was

the only possibility. Neverthe-less, I write (with word proces-sor, of course - but on paper)just in case you are tempted.A. Jaques. Manchester

We entirely agree with you thatthe 'electronic paper' and'electronic magazine' are along way off and even then theywill remain adjuncts to the 'realthing'. A pointer to this is that

paper usage, in spite of steeplyrising prices has more thanquadrupled over the pasttwenty years.

[Editor]

Mediocrity ...Dear Editor-Your new frontcover wilt not compensate foryour mediocrity in technology.Anonymus. Bradford

And excellence ...Dear Editor-Thank you for avery informative magazine. If itwere not for you, I would notbe a electromedical technician.I have gained a lot of knowl-edge from your excellent mag-azine.

Anton Carstens, Capetown

PIC ProgrammerDear Editor-Is there any inten-tion in future to provide a soft-ware/hardware upgrade for thePIC Programmer that I have

constructed from your March1994 issue.

The problem that I have isthat all my work so far hasbeen using 16C54s with whichI have no problems in pro-gramming (except that I initiallyreceived a 17C42 from one ofyour dodgy batches suppliedwith the na I ordered).

I still have not found anadvertisement for LTP, the com-

pany referred to in the articlewho supply the DB3 enclosure.J. Palmer, Burton -on -Trent

There are no plans (yet) for

upgrades of the PIC Program-

mer, but the one you built maybe modified to enablePIC16C71 devices to be pro-grammed by connecting a100 kil resistor between pin 18of U, and ground.

The address of LTP is

La Tolerie Plastique, Z.L Route

d'Etretat, F-76930, Octeville-

sur-Mer, France.

Telephone +33 35 449 292Fax +33 35 449 599.

[Editor]

SmartCardsDear Editor-I am a studenttaking a B.Eng (Hons) Com-bined Technologies (Microelec-tronics) course. I am engagedin a major project involving the(possible) use of SmartCards. Ishould be grateful if you wouldsupply me with informationrelating the card reader inFig. 7. p. 17, of your April 95issue.

S. Davey, Braintree

The SmartCard reader referred

to is produced by ITT Cannon.It should be available from thedistributor, Avnet Time, JubileeHouse, Jubilee Road. Letch-worth, Herts SG6 10H.Telephone 01462 484444.Fax 01462 488646.

[Editor]

Construction guidelines

Elektor Electronics (Publishing) does not provide parts andcomponents other than PCBS, front panel foils and software ondiskette or ti (not necessarily for all projects). Components areusually available from a number of retailers-see the adverts inthe magazine.

Large and small values of components are indicated bymeans of one of the following prefixes:E (exa) = 1018 a (atto) = 10-18P (pets) = 101 f (femto) = 10-16T (tera) = 1012 p (Ow) = 10-12G (giga) = 109 n (nano) = 10r9M (mega) = 106 p (micro) = 10-6k (kilo) = 103 m (mill) = 10-3h )hecto) = 102 c (centi) = 10-2da (deca) = 101 d (deci) = 10-1

In some circuit diagrams, to avoid confusion, but contrary toiec and as recommendations, the value of components is givenby substituting the relevant prefix for the decimal point. Forexample,3k9 = 3.9 142; 4p7 = 4.7 pF.

Unless otherwise indicated, the tolerance of resistors is ±5%and their rating is 1/3-1/2 watt. The working voltage of capacitorsis 50 V.

The value of a resistor "s indicated by a colour code as follows.colourblackbrownredorangeyellowgreenbluevioletgreywhitegoldsilvernone

1st digit 2nd digit0

1 1

2 23 34 45 56 67 78 89 9

mull factor tolerance

x1- 01

x 102x103x104x105 ±0.5%x1116

±1%-±-2%

x10-1 ±- 5%x10-2

Examples:brown -red -brown -gold = 12012, ±5%yellow -violet -orange -brown = 47 kf2. -±1%.

In populating a PCB, always start with the smallest passivecomponents, that is. wire bridges, resistors and small capaci-tors: and then the ic sockets, relays, electrolytic and other largecapacitors, and connectors. Vulnerable semiconductors and

should be done last.

Soldering. Use a 15-30 W soldering iron with a fine tip and tinwith a resin core (60/40). Insert the terminals of componentsinto the correct holes in the board, bend them slightly, cut themshort, and solder: wait 1-2 seconds for the tin to flow smoothlyand remove the iron. Do not overheat particularly when solder-ing ics and semiconductors. Unsoldering is best done with asuction iron or special unsoldering braid.

Faultfinding. If the circuit does not work. carefully compare thepopulated board with the published component layout andparts list. Are all components in the correct position? Has cor-rect polarity been observed? Have the power lines beenreversed? Are all solder joints sound? Have any wire bridgesbeen forgotten?

If voltage levels have been given on the circuit diagram. dothose measured on the board match them-note that devia-tions of up to ±10% from the specified values are acceptable.

Possible corrections to published projects are published fromtime to time in this magazine. Also. the readers letters columnoften contains useful comments/additions to the published pro-jects.

ELEKTOR ELECTRONICS MARCH 1996 69

READERSERVICESMARCH 1996

GENERAL

Ready-made printed -circuit boards (PCBs). selt-adrtesi a front pirrel foils. ROMs. EPROMs. ?A' s. akLa.wasocontsBais and diskettes for briliects iirkh Mot in Eking: Ektrdrarcs 0395 be a ft using its orderfoam brined ockosite_ Trelorm may a:no tn used to Ordid books Vivra =wren ady) Isms marked with a dot (a) fad -myna] LRe prodoct number are in Indent) supply ork)y, andtrez avalabrity an not se

g.3.3'rre...-1 rt.! 7'74 yOliT Order LS itCeNedItarnsont ! rt rot zradie_

- Tre art, ;-; PC135 yr,',k11 an eV areas:in read, -maena thraugo tni Reaters Serixes may be fatind in demaram

URDU". GALS . _ - - - too, we smoked raelkorogrannrd.Prices and item _ i:: I Tnt publishers reserve the NM to change pries without poornotdiaton. Pikes as. r indon nere v.sperx-de those in pretiam E OE

ORDERING INSTRUCTIONS, P&P CHARGES

ErM4 in Me LISkand orderr-_ erupt loo 5LZSCootc-14 ard / 71/.51 ba SaraBY POST to doe Da rcregn ttrrsa Oki) the Order form oceroan Please note Mat vie ca- PER-SOlitd.

CALLERS. as oci si>ct is cannot ai ire editions! and adrrn-asnatnn ornaReaders in We Maid Canada the. send advs. erupt for sobscr-Vions (fat wrixti see. Le. : Co'onySo.."4 Lab Peterbsec 167 hH onoU fun address is Om on Me ceder toms moan. Pisan rt.: .mf s' nc

i..iorriirg to toot order value: For surface debar, in We LtSk if order's less than $50, inWad-e 53. 550- . St. ForCanada surltEe. it less titan 115550. lock& US55: (155.50., 0557.50. For ak or otter ESK,aries. Mese 0...7.ire. Reamalai: 4-6 weeks fa darie.ly.All other CUIDEOSIS loira add {mg.]. dna packing charges for ordersup to 125.09 as fottriss: UK and am £1.55:wrist mar °auk UK OA&-$ tee seic7-zes) ass: oaf E.11Ope )airrrall £3.70. For atlas over £2503. but notsce.ebno £10360. these p&o charges seould be doubled. For orders.ova E10100 in value p&p cf1 r s Sri beOro

HOW TO PAY

Urdess )13t1 haw an appraisal credit actor.:, vertit Ls. at orders mat be accompanied Ill the tel bagmen:. ric4rdirnapassage and paling charges as .r.r.42.5me

ray be made by chreaut drams ea a Leaden clearing bank Out see pan. 4 Woe). Mal Order. V1SA-AcC=. as EuroCard lean paying tri aodst card. the order rr,rst go the can:Mon:es .14.44 Do not sendcash tniongn the mail. Crnocen and postal orders srto.'d be crossed and non 95)2510 to 'Elsktor Eitctronin

Paymert ;Tat also be made by direct transfer from a private Of taacess Giro account to our Giro account No.34 152 3131 try conker -0 and sending to We faboral Girt) Cann in a Itatkcal Eno csetge trakierwelope, a futst:...Goo i''.3f,er7;&406/4 Do no: sa-d Gird tnnsnrs crect to us asirts :kit( p.m: ads.It 'f2,15.,e outside tos UK. priment fray also De made by Banlers' Serial draft draws se a Looks Marie, het.Euoebegarn od Win pour.is Seam (with raters guarame card number ridden oil Ire We): or US or Cirettal

C1W4..e. tot sell cheques. =Med at tot ectki.-ce taae preezhwat 1110 time your ads is recency most beiscreassily the winks! M £15.00 p mar ace Unbars reoNialing tee_it 1tw pay by Rankers' sterling draft. make Cies to the issuing bank trial your fun dams and alstrrm MUST tebannr.us:-...V.ed to Me London during DankCra roarays are National Westminster Bank. 49 Garth Street. DORCHESTER. Donal 071 117W, Westnumber is 6966 3340

SUBSCRIPTIONS & PAST ISSUES&arsenous -re ac.:_::

-atee. srctiSO be Ordered iron" Worldwide Slascription Senn* LLS, Unit 4. Gibbs

Reed Farm. Plaits 710EHURST 7145 7HE. England. Far 11.,t-str v6ans. use soscinstrorn order formeiwnliere il this rhNlazina_Prices of pzU issues (enrept .vetax:avt ax Dy.eme..), for singa comes. are F.270 (UK and Erre):Q.02 (uptake Trial eve UK)- MO (ea road Engel: 065 (t.trnai bats Or EurCOO. Prim of past Jayilitrot. ertfDot nter issstM rack -tam postaze for sag* copies; are £375 (UK). t£4.00 (s.lritsae mare Oldsida UK): 423 (TrcaoEmpty and T500 (*mai tetseni Europe).

PAST ARTICLES

For urionnation on past orte...es. tease contact actoriri and ACrOcistrazwe Crifice rl Dorchester (telephone 01.3352a)995; to 013052512996)

COMPONENTS

Ca -wards for wrests appears inin Battu Esa.-tml.c.s are usual' avalable from appropriate Wariness inm.--Tiri-ire 11 didtaads Li ISO aro* of consconcra3 are errisawd a same nib rasWy be advised in Um ancle.

:8 311 1:. a- Tan is (are) not ottusim- te Mat to teM

TERMS OF BUSINESSDelia,' Atttice*tr every effort be made to 40.1.(li yv.{:: order Irbil 2-1 meets tram rebegA'N mar instruction.m an rot guarantee tine scale for al ordersRaisin 1--/), goods or pads sent bl error may be returned reger-rent or correcton, but MI Ware etWangsun Consent Al g...-tcls marred snudd be f.rs-.1 Sec4ray Weled bog C4 Mi. trolosiN a cony lefts 'OWN

rrtrtr (Ia camber It tS gno..5 se returned became pro thrstke cm urban_ we and refund tit team pcstaaGoods re -.red for refund most be in rewenle corenos zed wVt be si...itnect to a 10% Waco Surge Ninth a Fr it-auraSorge or o7 5.1O 111111111 dreele Mins tor cla-m.";a1 goods must to me -red al OW Dotchis otU.e *Sin NJ dies 11111). 14 dais(Eunape) or 21 tact. OttditGlIntegS) from the date on our 'FIF-orded Wk. try- sapCancelled enters 61 twxetrd-. orders ell to sutel to a 10% banding c....%2P votha maim nChar¢Of£2.50.Patents PatOn: O!rifoo nay emit. ar resent Of dew:e5. torroxnurts, ami so o.-1.ttescriMIL-i cis boo and

Eetiot EttctroOts (Purgs.tingl do na rs-ormilodity or /*bike far fears to ideitify such Ansa oratter pramnicn.Coyariaid Ai drawings. phstweam. stoles. printed circuit -bawds. progrwmied ri-ordedaarits C.4ii-v_msotreare carriers patashed in ea boots (other than in thirdimay adver5.swror%) are copyright rd:fey not be repmatzeil a trwaraned r arty form or ley any means. inotiadev ptsoirkwrg and recor&--4_ orm an. !Atoll -* prior permission at Earth' Electronics (Pubbstical) e1 untire,L-Can bermin must Moto

tokee wry tart of Vase limns is stand in a retrieval sfflern otarry rareItotnittannang 150 atom. priateacircuti boards may tee produced for private and persaml use *1100511 priorOtftr4s. SiOnManillas of lieldlity &Hot BecteorecS (Pubearins) shag rillbe SaNe br co7nad._ tort or falterers& bratty loss ordamage sutkred try Um poroNser Stratsceis ar rionsoriessiss-4 out of. or in conferion will, the supply of goods or:ereice$,by Seiner Bectrones (Publ.-sang) one man to WW1 goods as dMr1OFO Or, at it/ -4 CiptI'M of RoMorE4Srodits(Parststior9).10 rebind VeW r3rua *qtrwzi Ott in respect ot ire goals.Law Any T-:troole..4.4ng to Vest/colt of goon and services by atx Electronics tiltnalSigl Sao be dets=-ea

restricts by the laws of angrand. -by 19:4"

Article title Ordirs no. Price(E) (USE)

MARCH 19962 =-er

(4 Onbcti:z)PIC-CeintOrnd1105 Dewier.- + 05650Elf- 9,--Agsc-c- 16056" 9555351

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FEBRUARY 19952 9AP/tester KB 4 EPTI01.! tE60239-C-EPROM 566E031

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2015 40 501225 74.%1303 160]5.00 1000EEO 1203

JANUARY 1996W.." AM -to -PAL Cerruti! 25007E.2 2.903 531)3CW01 heater- PCS MACH.SAL 950104-C 44.07 am- MCNEAL 3525 70.51PnS'Ne. C0174ZO/W1 Tester

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DECEMBER 19953 3.15V Pew Surety 9501N-1 025 18.50Prazoca 1, -,es for rr,,,ra 9^.419-1 1725 3457SmartTansistor Tevar- PCS r PIC (3E6512-1) 950154-C 4125 83.50-Pit 16071 "M632-1 1550 71 0)

Vitro PLCPCB 87C75051 i-stsk 950093-C 44'30 590]

87C79331 956514-1 2430 4954- =trot wrinstaresk lM6016-1 100) 20'03

krim pan" t...,ris ar-1---risi-1 950 1920Elsc&r 95420-1 5.75 11.50Acth-0 probe 954T13-1 603 1603ino-way PC -Far 1-n_v E.4033 51 75 23_3350 -MHz 1612-bl. Logic Ario.-Wr system disk for Km' 958015-1 10311

SeAl nrit Oa:511016 or pLS11016 ICs (I visn.).Programnung chimes only. nn rndy-binned ICslICs* 9:6516-1 603 1203

- IC8* or ICI 5 E156516-2 603 1203 0.-irtkinAir tan software tin rail teed Mdad

Electro'nts (P,W,Oir4)

NOVEMBER 1995PIP Processor- PCB * 87C51(9556,535-1) 950.78-C

Erit51 956565-1RI nese sd_teen 955009.1PA 300 patterSV7irla LED 950112-1Ouse prescaler 933115-1

54_75 1015030.75 61.5010 75 21 5031975 393370) 1410

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OCTOBER 1995litaStEor 24.51C conic...Att.- PCS, 87651. disk Est

Oticic Ilefurnse cif* 00.3111-c 5225 118.50- 9317051 M6508.1 43 33 87 130

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t<6; Pic fitcro-condoTers 2441E6-1 17 75 35_50

SEPTEMBER 1995ifi.rt need:C.7e .17.:a-Fer 250:64-1Dangle sate_- PCB 9-50:51-1- GAL IC2 (20V8) 5;65/ 1.1-. GAL ICE (22V10) 956512-1HerFacerrer- amplfar FES 630102-sens-on 054055Copia! autunite': ;:pnce Ks W,ret I95e5134-1)-131811 IC 9E6504-1FIT tc-7e-rip incaScr 9M095 -I

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JULY/AUGUST 1995Acre mva suneoofer 2-4047 1225 24311AL.a ro...ecer 919249 8.00 1063&,tole Klu---ann g5wator950323-1 TM 15_06Arrailifainwine bassicnarw 950356-1 6 75 13.93

charger for U8d fab%rin,.-PCB Stotie0(E6 '6509 -119E0376 -C nis 45.50-nistr40 956503-1 1475 2250

Article mlo Orin, no. Fr:reICI (U65)

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6-t/ tncitnn toMery cria-ger 94E0E3-1 7_15 14.52

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Auto lift tenni WIC60-1VGA Onintestortmnpaer 950017.1

MAY 1995LODI arXtyser- PCB .r EPROM (V.6507 -1)34037B -C-EPROM 9E6507-1Ptevgrzrar for 87,139C51sar:es Hash compilers.- Pcs . EPROM (956644-1(55030-C- EPROM 905644-1Prngwr....aMe ezecen,ekfor.-PCB; MS:195E0:5-1) 950334-C-ce-toisArtere on ifsi 0.ANA-1Wed totteryloaNy fir. PCB r 5162715 trz6K.6-1)950751-C- 57E2715 25E605-1

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StKper robsoartror-PC -9 4 8751 dirk-8751

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A70 ELEKTOR ELECTRONICS 3/96

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