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AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver on 20, I S and 10 metres with our new constructional add-on Full transmit and receive capability allows all the features of your 2m set on the HF bands Work the world with a VHF handitalkie Easy to make with a com lete kit of arts available AUGUST 83
Transcript
Page 1: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

AN ARGUS SPECIALIST PUBLICATION

VHF to HF transverter

Use your 2m multimea ottransceiver on 20, I Sand 10 metres with ournew constructionaladd-on

Full transmit and receivecapability allows allthe features of your2m set on theHF bands

Work the worldwith a VHF handitalkie

Easy to make witha com lete kit of arts available

AUGUST 83

Page 2: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

Buy Loritisnjby

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MADE IN ENGLAND by BANTEX, LONDON

Page 3: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

EditorFrank Ogden G4JST

Assistant EditorRichard Lamont G4DYA

Advertisement ManagerNeil Terry

Classified SalesJulie Bates

Managing EditorRon Harris

Managing DirectorT.J. Connell

Published by:Argus Specialist Publications Ltd.,145 Charing Cross Road,London WC2H OEE.Telephone: 01-437 1002.

Distributed by:SM Distribution Ltd.

Printed by:Q. B. Ltd.

Subscription Rate:UK £12.800/Seas Sur. £13.250/Seas Air f2-5.80Ham Radio Today,Sub Dept.,513 London Road,Thornton Heath,Surrey,CR4 6AR.

Ham Radio Today is normally published onthe first Friday in the month precedingcover date. The contents of this publicationincluding all articles, designs, plans, draw-ings and programs and all copyright andother intellectual property rights thereinbelong to Argus Specialist PublicationsLimited. All rights conferred by the Law ofCopyright and other intellectual propertyrights and by virtue of internationalcopyright conventions are specificallyreserved to Argus Specialist PublicationsLimited and any reproduction requires theprior written consent of the Company. ©.1983 Argus Specialist Publications Ltd. Allreasonable care is taken in the preparationof the magazine contents, but the publisherscannot be held legally responsible for er-rors. Where mistakes do occur, a correctionwill normally be published as soon as possi-ble afterwards. All prices and data contain-ed in advertisements are accepted by us ingood faith as correct at time of going topress. Neither the advertisers not thepublishers can be held responsible,however, for any variation affecting price oravailability which may occur after thepublication has closed for press.

VOLUME ONE NO. 8 AUGUST 1983

REGULAR COLUMNSLETTERS 4

RADIO TODAY 7

RADIO TOMORROW 32

TECHNICALITIES 34

PRACTICALITIES 40

NEWCOMERS FORUM 43

NEW PRODUCTS 69

CONSTRUCTIONVHF TO HF TRANSVERTER 9Work the world on your 2m handitalkie. The most interesting home project for ages

ELEVEN TO TEN Pt 2 31PCB layouts and other into to go with the CB to 10m article in our June issue

A COMPACT AERIAL SYSTEM FOR HF 51A new LI: band design by Steve Ireland G3ZZD

PROJECT OMEGA. notch filter and preselector 66Two more modules in our all band, all mode transceiver series

FEATURESRADIO MATHS FOR THE RAE STUDENT 17Part two of our series takes the pain out of swotting

TAKING APART THE FT -101 Pt 3 19More wisdom on this famous marque from Harry Leeming G3LLL

RIPPING YARNS 22We guarantee that these tales from G3OSS are not apocryphal

RTTY-THE LONG DISTANCE TYPEWRITER 25The second part of this fascinating series

CURRY ON HAMMING 45Amateur radio in India isn't the same as it is here

REVIEWSTEN-TEC ARGOSY HF TRANSCEIVER 55Run-of-the-mill it isn't. A famous name imported by a famous name. KW

AZDEN PCS-4000 63The editor's view on the latest in this breed of black box

Next month in Ham Radio Today 44

Corrections to the DSB80 project 54

Emporium Guide 70

Classified 72

Advertisers' index 74

HAM RADIO TODAY AUGUST 1983 3

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TTERSPlease address correspondenceto:

Frank Ogden G4JSTHam Radio Today,145 Charing Cross Rd,London WC2 OEE.

BOOMING

Sir, Amateur radio is booming; the G6series is, at the time I write, almostcompletely issued. There are long waitinglists for morse tests, the Home Office hasbeen berated for not being able to meet thedemand for A and B licences after eachexam time. Now someone wants a novicelicence I am truly amazed that anyonewould think there is a need for one.

I, like thousands of others who are nowlicenced, have no background inelectronics. The RAE studies were hard forme but I wanted a G ticket. When I metwith amateurs to learn as much as I couldfrom them, they all said "If you want thelicence enough, persevere and you will getit.".

CW next the same applies; only workingat it will get a pass.

Anyone who is really interested inamateur radio will be prepared to work toget the licence.

A recently licenced amateur in my areasat the RAE seven times before he passed.He told me he persevered because a Gticket was something he believed was worththe effort.

I would be interested to know how manyamateurs and SW Ls are against a novicelicence.

A B WHITTAM G6HAH

My personal feelings are that a novicelicence would serve no purpose other thanto devalue the hobby - Ed.

INAPPROPRIATE

Sir, Amateur radio is a means ofencouraging goodwill between people in allcountries of the World. It is therefore totallyinappropriate for the Patron of the RSGB todeclare publicly that he is in favour ofnuclear weaponry. He should take theearliest opportunity to retract his statement.

P THOMPSON

(The patron of the RSGB is the Duke ofEdinburgh, who made a speech in favour ofkeeping a minimal nuclear force - Ed.)

MYOPIA

OM, Regrettably, I find myself indisagreement with some of my fellow -countryman's comments regarding the"American Woodpecker" (June HRT). Torefute any kind of political bias in thematter, might I state that I am a holder of atemporary El call, and a frequent andwelcomed visitor to Des's 'neck of thewoods'.

I certainly would not consider hisopinions to postulate "undesirability", butthey do, unfortunately, indicate somedegree of myopia. My own opinions wouldbe the same if I held an F, DJ, OE, W, VEor whatever call.

If only all the world's governments -and peoples - were imbued with the 'HamSpirit' we could all, thankfully, happily andmultilaterally, dispense with the ghastlyparaphernalia of war - including'woodpeckers' and 'tacklers' - East andWest.

Unfortunately, realism tells us that we donot live in that kind of world. Withoutsounding 'trite', I suggest that freedom stilldemands the same sacrifices as those of40 -odd years ago.

Regarding this much -maligned world,might I direct Des's attention to page six ofthe same issue? I doubt if some of ourfellow -enthusiasts could demand the sameconsideration from their own 'powers -that -be' - if they did, I fear that many of themwould find themselves /A or 'silent keys' fortheir temerity!

JOE BEATTIE GI3NQH

Taking that last point a bit further, it'sinteresting to note the difference inattitudes between Western governments.When we ask questions of the UKgovernment - ie. the Home Office, or as inthis case the Ministry of Defence - theyusually try and fob us off with any oldrubbish. Sometimes they claim things areclassified, in spite of them having alreadybeen published. More usually they don'teven return our phone calls. Let me assureyou, Government bodies treat amateurradio topics in a manner little short ofcontempt.

Contrast this with American practiceafter the Freedom of Information Act. Forexample, when we asked the US Air Forceabout the Con us over -the -horizon radarsystem, not only did they answer all ourquestions willingly, but also sent usphotographs and technical data of theinstallation, without even being prompted.And this is a brand new system designed togive early warning of a nuclear attack.Imagine getting that sort of treatment if youasked the MoD about Fylingdales! - Ed.

SIMPLE HF AERIAL

Sir, With reference to the March issue, andthe article by Malcolm Healey G3TNOentitled A Simple HF Aerial, I haveinstalled this aerial in my loft and can vouchfor the author's comments about it, butcould you please tell me where I can get thenecessary six -way six -pole switch, and thetwo-way four -pole switch from? I havewritten numerous letters to advertisers in

this and other magazines but always get theanswer "Sorry Sir" not in stock and cannotadvise you where to get them.

Hoping you can solve my problem, sothat I can construct the switching unit andthus make a good antenna even better.

D STEPHENSON

You will need to assemble the switches outof ceramic switch wafers. These are a bitdifficult to get hold of - I suggest you keepyour eyes open for them at rallies - Ed.

RUBBER DUCKS

OM, regarding your article on VHF/UHFaerials, I cannpt fully agree with you onyour comments on the hand portableaerials. No doubt you can get someimprovement by using the aerial yousuggest but surely the whole obect of thehand set is to be small and easy to use. Ifyou are going to add large aerials to it youmay just as well use a mobile rig.

I use an FT209 which I find a superb rigon and receive, and using therubber duck aerial I have had QSOs fromthe centre of Petersfield to a fixed station inChichester, and a mobile station with whichI held a QSO all the way from Petersfield toHeadly Down.

My other hobby is walking, and I alwaystake the FTliti with me and get very goodresults with the rubber duck aerial.

I would also like to comment on the sillyarticle you have, to be an April fool joke, Icannot understand why you have to havethis and waste paper. As this was in theissue that I purchased on 30th March andwas dated May, I think the joke was on you.

Otherwise I consider your magazine tobe very good with plenty of interestingarticles, and the equipment performs ratherthan just being rows of performance figures.

I look forward to future issues with greatinterest.

G E R DENMAN G3MEW

What silly article? - Ed.

400W LINEAR AMP

Just a couple of quickies on that CO wattHF Linear Amplifier in the May edition.

By all means, use everything possiblefrom the junk box, and search the rallies foranything especially required, but be reallycareful about any component which mightbe at all doubtful - such as condensers(sorry, capacitors!).

If using normal valve -holders for the4CX250s, it would be advisable to drill themout as much as possible, as one of thereasons for using the standard (and very

4 HAM RADIO TODAY AUGUST 1983

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expensive) Eimac bases was to ensure that acooling blast of air was shot up the mainorifice of the valve, hitting the spots the restof the air couldn't reach .

And if you do decide to use thosediscarded 813 bottles, remember they take10 volts at 5 amps each on the filaments,and this must be kept dead on, otherwiseyou'll strip the coating!

DOUGLAS BYRNE G3KPO

A TALE OF TWO SYDs

Editor, My husband passed his RAE lastDecember and as his name is spelledSydney he reserved the callsign G6SYD forwhich he had to wait only an extra week toget.

He started to work for his morse exam inJanuary after realising if he worked hardmaybe he could get the G4SYD. On March16th '83 after only two months of very hardwork he'passed the morse test at Cullercoatsradio station, and sent the appropriatepapers away to the Home Office askingthem to reserve G4SYD. On 12th April1963, with only a few callsigns and a matterof hours to spare G4SYD came through ourdoor to a delighted Syd.

I would be most interested to know if thishas happened before.

JEAN COOK

PHASE COMPARATOR

Frank, I am following your seriesTechnicalities with interest, but a few thingsworried me in the May article.

In Fig. 11, the digital phase comparator,both output transistors can be switched onat once, albeit for only 50nS or so, as ittakes this finite time after the second D -typehas switched on before both are reset. Thiswill surely put spikes on the power (andearth!) rail if not actually damaging thetransistors in time. While fancy digitaltechniques could doubtless cure this glitcha simpler way I believe would be to limit themaximum current with emitter resistors of afew hundred ohms in both transistors. Asthe loop filter has a high input impedance,this shouldn't affect operation of the circuit.

Secondly, you do not seem veryimpressed with varicap diodes. Were theyconducting, I could understand if theygenerated noise, but they are reversebiased, so I don't! Perhaps you couldexplain please, and does not the diode on

the gate of the BF256 oscillator in Fig. 7have similar disadvantages?

Finally, and this is my fault not yours, Idon't understand how the crystal oscillatorsin Fig. 8 work. OK, the L (Sr C in the draincircuit resonate, and the Miller (?)capacitance drain -to -gate forms thefeedback so it will oscillate, and I couldeven believe it will be pulled by the crystal,but the signal at the gate will surely be lowlevel, and it is fed to a tapped coil whichmust also be low impedance, putting a highload on the oscillator contrary to normalrecommendations. Could you explain itsoperation please?

I am also wondering if a separatelyregulated supply to the switched oscillatorswould be advantageous, else any nasties onthe 12V line will add noise sidebands youare so desperately trying to avoid. I alsowonder whether the diode in the gate addsany noise, as per your comment onvaricaps?

P VINCE G8ZZR

Good point abut the glitches. I hadn'tthought of that. We have incorporated youridea in the Project Omega VFO. Manythanks. Re. varicaps, the noise generation

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HAM RADIO TODAY AUGUST 1983 5

Page 6: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

is FM. The effective noise voltage, which isproportional to the control line impedance,modulates the capacitance of the varicapjunction.

Lastly Miller effect. The drain to gatecapacitance forms the feedback pathbetween two high 'Q' oscillatory circuits.This is effectively about 10pF when the gainof the device is taken into account.

Oh yes, forward conducting diodescontribute very little noise because theireffective resistance is very low duringconduction; noise voltage is proportional tothe square root of resistance -- Ed.

ROLL ON HOME BREW

Sir, I read with interest Jack Hum'scomments in the May edition of HRT.

As a relatively new licence holder(G6NGR) I am as yet exploring 2m, andbeing skint, set about 'home brewing'. (I dohave the 'slight' advantage in working for alarge semiconductor manufacturer.)

One of my colleagues, who is also arecent G6, bought a 'black box' rig, and ina recent conversation was telling me how heheard one chap calling CQ, and beingfirmly ignored, because "he was 2 or 3kHzoff channel". On hearing this, I set aboutchecking our workshop signal generator,and other bits I had assembled en route tomy home -brewed TX/RX. The net result wasthat I hadn't a chance of holding thestability apparently required.

I say apparently; the trend amongstcolleagues here is more home brew, modsto Pye taxi mobiles etc., the black boxes arejust too expensive. I repaired one recently,and quite honestly, the hardest bit wasdriving it. More to the point, the gent whoasked me to fix it (no names, no packdrill)hadn't a clue; and had been quoted £40 or£50 to replace one resistor (a parasiticstopper, 22 ohm, 1/2W carbon) which tookme maybe half -an -hour to find (lucky!).

To sum up, there is a trend to simplercheaper gear around here; there is a 'QRP'feeling on 2m in the 'all -mode' slot, 144.5 to144.9MHz, where I am trying AM with threevalves, and a two -valve receiver (not readyyet).

Many thanks, Jack Hum, it's a goodcolumn, keep writing, and let's have more2m home brewing! We'll be listening (AM)in the all modes slot.

PETER THORNTON G6NGR

6 METRE LICENCES

Frank, First of all congratulations on a mostinteresting and refreshing new publication. Ihope you manage to keep up the quality ofthe articles and the down-to-earth approachto amateur radio.

I have been most interested (andamused) by the recent comments in all themagazines about the 6 metre licences saga.I was one of the 25 amateurs approached inMarch 1981 by the RSGB and naturallyexpressed my great enthusiasm to have apermit. As you know nothing came of thatparticular exercise. I have been active on '6'since 1979 and have worked 20 countriesand all continents except Australasia cross -band to 10 metres. When my applicationwas unsuccessful in the latest approach I

was not too disappointed until I saw some ofthe call -signs who had been grantedpermits. I have one simple question to ask- if the RSGB saw fit to ask me if I wanteda permit 2 years ago, then why was Iunsuccessful this time? Particularly whenpeople have received permits who did noteven possess a 6 metre receiver!

ROGER BARKER G4IDE

Ask the Home Office - Ed.

PUERILE MEANDERINGS

Frank, Look, I may not be the mostinspiring writer in the world, but at least Iwrite rationally and coherently. It thereforeburns me up to find you printing peurilemeanderings from the likes of that patheticwally "SSB CB User", while my commentson your little piece on the RSGB a coupleof months ago were totally ignored. Whatgoes on, do you only want to encourage thelunatic fringe, or are you the only onepermitted to criticise the RSGB in HRT? Isuppose the charitable alternative is that theletter failed to arrive.

With reference to the article on'planting' towers, p44 June, please note thatthe weight per cubic metre of concrete isnot 230kg but about 2400kg. A slightlycheaper mix would be 1 part of cement to 2parts of concreting sand to four parts of20nm graded gravel. Broken bricks shouldbe avoided for this application. The mixshould not be too wet, and should bethoroughly compacted by ramming with abillet of wood or repeatedly plunging theblade of a spade into it. To prevent frostdamage in cold weather no more than 2kgper cubic metre (less than 1% weight ofcement) of calcium chloride should bedissolved in the mix water, in which caseparticular care should be taken withcompaction to avoid corrosion of the foot ofthe tower.

BRIAN A CARTER G8ADD

SELF TRAINING

Sir, I feel that P. Short's letter in the May19033 edition of HRT sells amateur radiorather short. The purpose of obtaining anamateur licence is to further the training ofthe licensee in 'wireless telegraphy'. Incontrast CB merely allows citizens to talk toeach other.

This distinction allows the amateur to usewhatever equipment he or she may select.This freedom is one which we shouldprotect at all costs. It would appear that P.Short would rather abandon ourexperimental abilities in order to obviate theneed to buy (or build!) a wavemeter.Speaking as one of many amateurs whohave never been formally educated inelectronics, I have learned everything Iknow about radio through the "self trainingof the licensee". This knowledge is nowsufficient to tackle and successfullycomplete a 2 metre homebrew transceiver- not many CB operators will ever learnanything beyond toytown slang.

There is a school of opinion that DXmerely means long distance working. To meand to thousands of others it means using

the bands, rigs, antennas to the maximumwhich our individual skills will permit.Range as such does not have anyimportance. Anyone who has appliedhimself/herself enough to obtain a licenceneed have no fear of being closed down forlack of attention to interference prevention.HRT provides many useful circuits andideas which should keep everyone on thestraight and narrow.

Amateur radio is a superb hobby open toall who are prepared to put in the necessarygroundwork. It is not CB, and I hope itnever will be. Why should CB supportersnot remain in their own allocations (ie. noton 28MHz) and allow amateurs to continueto learn the rules of wireless telegraphy?Contrary to common belief there are stillsome experimenters and home brewersaround!

J S EDGAR GI4FVM

Yes. I'm one - Ed.

Sir, Having just read P. Short's letter in May83's Ham Radio Today I was surprised atthe attitude he/she has taken.

Obviously P. Short's knowledge ofamateur radio is poor; as the whole essenceof his letter is pointless. However to put himin the picture, amateur radio is differentfrom CB, PMR or any other use of radio asit is permitted for us to dive inside our blackboxes or home-brew gear and tweak to ourheart's content. Try to understand thatamateur radio is not just radio operation,but it is equivalent to a radio technician orengineer with regard to PMR etc. We arelicenced to run more power than CB, PMR,VHF marine radio etc. etc. on two metresand above, and this surely means other thanhaving regular checks by BT or HomeOffice officials (with the large proportion ofClass B licensees this is prohibitive expensewise) the amateur himself must thereforehave equipment and know-how to realiseand correct any faults in his station. Hencethe need for checking equipment.

As for the point that CB users cannot beclosed down I can recall at least fourstations which have been closed down forinterference. Also P. Short must be awarethat AM and SSB CBers are closed down ona regular basis.

Also I am unaware of G6NSU'scomments as I did not have this mag then,but if you really believe such a comment as"an is worse than 27MHz FM for workingrange" then I feel you're very unaware ofwhat an holds. It is about time you got apiece of equipment to receive on two assoon as possible because you're missing out.I can work further on lOGHz with 5mW ofwideband FM than I can on 27MHz FM withfour watts into a half -wave vertical. So goon, get your act together and find out whatamateur radio is about before criticisingsomething which you have no experience ofor about.

The amateur licence is always changingto meet new methods of operation.

K BRAZINGTON G4LZV

When amateur radio was mainly a scientifichobby, it had a lot of respect. If it is mainlya black box activity, it's not surprisingpeople see it as up-market CB - Ed.

6 HAM RADIO TODAY AUGUST 1983

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RADIOTOD

News about amateur radio compiled by Richard Lamont G4DYA

MAY RAEAccording to the City and Guilds ofthe London Institute, which sets theRadio Amateurs' Exam, about 7700people took the exam on May 16. Thisfigure is slightly down on the May 1982exam. The C&G says that results willbe issued in early August.

AMATEUR ELECTRONIC MAILRTTY enthusiast Roger Barker G4IDEis calling for the development of anautomatic, amateur electronic 'mailbox' system, to store and send RTTYmessages between amateur stations.He says that similar systems are alreadyoperational in several countries, andhe wants the RSGB to seek HomeOffice approval for the system in the

for a 432MHz repeater in the Wisbecharea to the RSGB Repeater WorkingGroup.

The North Cambridgeshire Groupsays 70cm activity is increasing, andthey hope that a repeater would coverthe gap between neighbouring repeaters'in an area which is of a low-lying naturein the heart of the Fens'.

AMSAT LATESTAt the time of writing, the Phase-IIIBsatellite is due to go up on June 16th.

HELP WANTEDThe organisers of the amateur radiodisplay at the National Town andCountry Festival are looking for peopleto help man it. The Festival, which will

2m special event stations using the call -sign GB4TCF, they hope to have dis-plays of home construction, amateurTV, RTTY and microwaves. Theorganisers say that assistance would begreatly appreciated from both licensedand unlicensed enthusiasts. Anyoneinterested should contact Roger HarrisG3ZFR, on Coventry 365117 beforethe event.

BROADCASTING COURSEBroadcasting - Marconi to Channel 4is the name of a weekend residentialcourse looking at the development ofbroadcasting from the early days to thepresent. The sessions will be enlivenedby using models and archive material,including 'fireworks' in the form of areplica of Marconi's spark transmitterand receiver, and a Baird 30 -line Tele-visor.

Other topics covered are: high powerequipment for short wave broadcasting;microphone technique and scripts; thetelevision camera and scenic design.

The course director is Ralph Barrett(at present with the BBC) who will leadthe sessions. The organisers' publicityblurb says that "Theobalds Park Collegeis 3 star accomodation, an amenablesocial atmosphere, 13 miles fromLondon, by train or car. Fees, for theweekend, inclusive of full board: 28pounds sharing (make up a party?);

'all mode' section of the 144MHz band. be held at the Royal Showground, 50 pounds single."Stoneleigh, Warwickshire on 27-29 Details from: Theobalds Park

CAMBRIDGE REPEATER August, will include an ambitious College, Bulls Cross Ride, WalthamThe North Cambridgeshire 70cm Rep- amateur radio display staged by several Cross, Herts. Tel. Waltham Crosseater Group has submitted a proposal clubs in the area. As well as HF and 37255.

If you must install a transmitter without a licence -- don't get caught!

SWL FINEDA shortwave listener has been prosec-uted for installing an amateur bandtransceiver under Section 1 (1) of theWireless Telegraphy Act 1949.

Michael John Craven, of 29 ChantryRoad, Disley, Cheshire pleaded guilty toinstalling an Icom 720A transceiver atMacclesfield Magistrates Court. He wasfined seventy five pounds with twentyfive pounds costs.

After the case, Mr Craven told HRTthat his equipment was in use purely forlistening purposes and had been disabledin the transmit mode 'by a local dealer'.

This case highlights the fact that it isillegal to install, let alone use, any formof transmitting equipment without theappropriate licence. Although no legalprecedents have been set, it underlinesthe problem faced by Class B amateurswho own HF transmitting gear, inanticipation of a Class A licence, whileat the same time using that equipmentpurely for listening purposes.

HAM RADIO TODAY AUGUST 1983 7

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Page 9: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

VHF to HFTransverterThe high performance VHF transceiver isfairly ubiquitous among the amateurpopulation, and it has always seemed tothe author such a waste to use suchperformance for one band only. Theauthor possesses an1C202S which over thepast 18 months has been constantlymodified to achieve the lowest possiblenoise figure in order to better realise theVHF DX potential of the system. Once thishad been achieved, a means of communi-cating on the 20 metre VHF net wasrequired in order to arrange schedules.The author's bank account, not being in aparticularly healthy state, ruled out one ofthose £500 plus HF transceivers describedin the glossy advertisements.

With this problem in mind, the down-transverter to be described was developedduring Winter 1982. Not only was itpossible to transvert from 2 metres to 20metres, but 15 metres and 10 metres werealso possible, due to the nature of themixer and preselector components. Theproblem with multi -band transceiverdesign, one of band switching (usuallyrequiring multi -way wafer switches andyards of coaxial cable) is largelyeliminated in this design. The unit is alsototally independent of the VHF prime -

By David JohnsonBA(Hons), G4DHF

mover. No modifications are necessary.Simply plug in your transceiver, select theband, peak the signal and you are on theHF bands for an outlay of around £70. Thisshould make it one of the most cost-effective systems available. Theperformance of this little unit exceeded allexpectations, and with a power output ofonly 3 watts, the first evening of operationprovided contacts throughout Europe,including SMO, EA, EA6, F, I, YU, DI,CT1, OH, OK and LA. This was even moresatisfying given the makeshift nature of theindoor antenna, erected in the loft -spaceonly minutes prior to testing! Theperformance of the receiver is excellent onall bands, and would certainly performbetter under strong -signal conditions thansome commercial transceivers due to thehigh-level mixing system. Conversiongain is such that, even on 10 metres, noisecan be peaked on a 50ohm resistor acrossthe input.

Fig. 1 shows the block diagram of thesystem. The design is based around a low-cost bi-directional mixer, the SBL1. Here.the VHF signal is mixed on both transmitand receive with a diode switched local

oscillator producing the required outputfrequency. During transmit it is importantthat the SBL1 is driven with the correctamount of power of 5mW, and is termi-nated into a 50ohm load. Powers much inexcess of this will cause saturation of themixing diodes resulting in numerousspurious products being generated duringconversion. Relays RLY1 and RLY2 switchin a resistive 'T' attenuator network toprovide around 28dB attenuation for a 3watt source. A 30dB pad was used in theprototype as the author's transceiver (asare most) is conservatively rated. Both the10202 and F7290 have performed wellusing this system. If other power levels areenvisaged, then the attenuator networkmust be adjusted accordingly. Furtherinformation can be found in the ARRLHandbook and the December 1982 editionof Radio Communication.

In order to reduce the amount ofunwanted products generated in themixing system, it is important to have astable, low -noise, low -harmonic oscillatorcapable of producing an output ofapproximately 0.7V RMS correctlyterminated at the input port of the mixer.Band switching is achieved by switchingHT between one of three identical oscil-

o Relay control for linear

o I1-°144MHz

transceiveRly

Switching

ht2+

Fig. 1. Block diagram. 144 MHz - 20/ 15/ 10metre transverter.

ht 1 +

VR1 vox delay

IAtten

30db -3W23db - 1W Rly

2

MIX

SBL1

Osc. X2BPF

Diode sw.

65 MHz 130 MHz 04

Osc X2BPF

Diode sw

61.5 MHz 123 MHz

Osc X2 X2

BPFDiode sw

58 MHz 116 MHz 111+

*-11..."Twin

BPF

I Allen /pre -amp Coax Imk

Rly3

20 2015 ° 15

1012V+

10

L

Tx

pre amp

Tx amp

2 X 2N4427Rly4

R ly 5

HAM RADIO TODAY AUGUST 1983 9

Page 10: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

Resistors Capacitors Semiconductors

R1, R2 47R 1W C1,C4, C31 to 36, C38 to 49 1nF TR1 BC238, BC239R3, 3R3 C2 2p2 (for 3W drive) TR2 BFY51R4 330k 8p2 (for 1/2W drive) TR3, 4 BC327, BC328R5, 14, 22, 23, 37 1k C3 10uF/15V tantatalum TR5 3N204 or 3SK45/51R6, 38 4k7 C5, 6, 7, 8, 10, 12, 13, 14, TR6, 10, 11 BSX20, 2N2369R11, 17, 33 10k 16, 17, 18, 20, 21, 22, 23 TR7 2N3553R9 56R 1 OnF TR8, 9 2N4427R10 100k C9, 15, 19, 24 2u2/15V tant D1, 2, 3, 4, 5, 7, 9, 10,R12 22k C25, C27 220p 11 1N4148 1N914R24 27R C26 330p D6 1N4001R7, 8,18,21,34 100R C28, 30 68p D8 10V1 Zener diodeR15, 29, 30 1k5 C29 150pR19R20

18R150R

CX 2p2TC1, 2 2 to 22p trimmer Miscellaneous

R26, 35, 220RR27, 28 4R7R31 330RR32 2k2R39, 40 1ORR13, 36 390R

VC1 250 or 500p variable

C37 6p865MHz (20m) HC18/u crystal61.5MHz (15m) HC18/ucrystal58MHz (10m) HC18/u crystalRLY1 to 6 1150-060-1 9VPCB mounting (J Birkett)

RX 22k (mounted underside T1 to 5 10mm block ferriteacross L4 RFchokes cores ( J Birkett)

RY (mountedundersidetext)

L5 -see4k7

RFC1 4u7RFC2, 3, 4, 6 ,7 5turns 30swg

6 off T50-6 Amidon toroidsTMP Electronics, AmbitSBL-1 balanced mixer

VR1 50k preset, verticalmounting

through ferrite beadRFC5 10u

SW1 2 pole 3 wayVeropins

NOTE: L3 and L4 may be replaced with TOKO pre -wound coils type 301 -KU -0800. There are extra holes andpads shown in the oscillator board PCB artwork to accomodate them.

The components of one oscillator section only have been included in this parts list. If operation on allthree bands is required then the extra components associated with two further oscillator strips will berequired.

lator circuits, differing only in thefundamental frequency of the crystals.Taking the 20 metre conversion system asan example; if we have an IF of 144MHz,and wish to tune 14MHz, a local oscillatorinjection of 130MHz is required at themixer. Here the sum (144 + 130 =274MHz) and the difference (144 - 130 =14MHz) frequencies are generated andsuitably filtered by the tuned circuits in thepreselector. It will be noted that theconversion crystals are within a few MHz ofeach other, which greatly simplifies theconstruction of the injection oscillators.The stabilised overtone circuit aroundTRIO, tuned by L3 produces a signal halfthat required at the output. The smallinductance L4 in series with the crystalallows precise frequency control. ResistorRX mounted underside across IA reducesany possibility of the stage sell -oscillating.This signal is lightly coupled into the nextstage TR11 operating in a grounded basemode which acts as a doubler. Theresultant frequency appears across L5,tuned by TC1. L6 and TC2 form the secondsection of the band-pass filter which issharply tuned at the output frequency. Theoutput from each oscillator is connected to

the same point via diode D9, thuseliminating manual switching at RF. As HTis applied to each oscillator, D9 conductsthrough R37 and R38, allowing lowimpedance injection into the mixer. At thesame time the other output diodes arereverse biased, and so effectively isolatethe signal from the other tuned circuits.

The required mixing product is 'selected by a twin -section torroidal filter.(active both on transmit and receive)tuned by a twin -section 250pF variablecapacitor. Low impedance transformationis achieved by the link -windings on theinput and output. Originally, inductivecoupling between the toroids was used,but later abandoned as the capacitivecoupling between the preselector com-ponents proved to give very satisfactoryperformance.

Transmit and receive signals aredirected through relay RLY3. On receivethe incoming signal passes through thelow-pass filter and appears at the receiveside of relay RLY4 (point 'A'). This must beconnected to RLY3 (point 'A') via a shortlength of coaxial cable. Depending on theVHF source in use, it is possible to add awide -band receive pre -amplifier at a later

stage, particularly if the unit is modifiedfor higher output frequencies. In theauthor's case, signals were so strong that aswitched attenuator was envisaged toprevent over -loading the prime -mover!On transmit, the low level signal isamplified by the broad -band class 'A'amplifiers producing an output of around3 watts into a 50ohm load. No originalitywhatsoever is claimed for the design. Theinformation is readily available to anyonewho has a copy of the 'constructors bible',Solid State Design for the Radio Amateur.

It appears that Frank, our illustriousEditor, and myself were thinking along thesame lines when he described the broad-band transmit pre -amplifier chain in anearlier edition of this magazine. In fact, Ithank him most sincerely for the inform-ation on the wide -band transformers whichare used at each stage. TR5 acts as animpedance matching device. Any attemptto self -oscillate is halted by R9 across theinput. To further reduce the possibilities ofsell -oscillation, the tantalum capacitorsprovide the necessary LF decoupling. Thehigh gain VHF devices used for TR6 andTR7 increase the signal sufficiently todrive the push-pull amplifier TR8 and TR9

10 HAM RADIO TODAY AUGUST 1983

Page 11: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

(suitably fitted with heatsinks). Variousgain compensation networks were triedduring development, but the simplicity ofthe final network proved to be quiteadequate.

The amplified signal passes throughthe LPF to further reduce harmonics andspurious products. Again in order tosimplify band -switching the signal isdiverted through one of two filters viarelays RLY5 and RLY6. In the author'scase, as 20 metres was the main conversionband in use, the unenergised filter passcontained the 20 metre section. During theswitching of the voltages to the oscillator,the filter relays become energised when 15metres and 10 metres are in use.

In order to make the unit totallyindependent of the transceiver, automaticswitching is employed. A small amount oftransmit power is sampled by C2 and isrectified by diodes D1 and D2. Thisvoltage switches TR1 'on', causing TR2 toconduct which energises the relay line.Transistors TR3 and TR4 are also switched,providing HT for the amplifier chain. Anadjustable delay time is provided via D3,C3 and VR1. Diode D3 allows C3 to bequickly charged when a voltage is present.Capacitor discharge is varied throughVR1, R5 and R4, which holds TR1 'on' foras long as a voltage is present. In practicethe unit is so sensitive that the initial burstof unbalanced carrier produced when thetransmitter is activated is detected,sending the transverter into transmitmode. If the F7290 is used, the voltagepresent during transmit can be used toactivate the switching circuit (Fig. 5)

providing full independent switching.Construction on the double -sided

circuit boards is straight forward andshould present little difficulty, although

O

O

Coil dataLI, L210 turns of 30swg wire woundon a T50-6 toroid.

LI a, L2aWound on the toroid cores nextto the main windings.Two turns 30swg

L3Eight turns of 30swg wire on 6mmformer fitted with tuning slug.

L4Seven turns of 30swg wire on 6mmformer fitted with tuning slug.

L5,16Six turns of 18swg wire wound on a7/32 inch mandrill, self supportingapproximately 1 cm long. Diode tapon L6 PA turn from earthy end.

TI to T5All wound on 1 cm square ferritecores using 30swg wire. The wireis passed through the holes in themanner of a conventional transform-er. Individual details as follows:Tl Eight turns centre tappedT2 Four turns primary, two turns

secondary.T3 Winding details as for T2T4 Four turns primary, four turns

secondary centre tappedT5 Four turns primary centre -tapped

Secondary four turnsFilter coilsL8, L912 turns of 22swg wire on T50-6ferrite toroid coreL10, L11Nine turns of 22swg wire on T50-6toroid core

the following points should be noted. Topquality, full spec. devices must be used ifthe high performance of this unit is to berealised. One of the prototypes used a'branded' BSX20 of unknown manu-facture. Although the unit did work, therequired output voltage from the oscillatorwas only a fraction of the desired amount,and it was noted that the stability of theoscillator was not as good as those inprevious units. A replacement BSX20totally eliminated those problems.Vertically mounted components in contact

R15, R17, R18,R25, R36, R37 and RFC5 should have thebody of the device directly in contact withthe signal line to prevent radiation throughthe component leads. The power outputfrom the oscillators is quite high and soadequate screening must be provided,

-12V VIA OSCSW1e OUTPUT

preferably using tin-plate, or failing thisdouble -sided PCB. An 18swg aluminiumscreen is positioned between the twocircuit boards, which also locates VC1.Screened wire should also be used tosupply HT to the individual oscillators.When the unit was housed in a die -casebox it was noted that the excellentspectrum output was made even cleanerdue to the increased screening betweenstages. Care should be taken whenwinding the broad -band transformers, asspace through the holes is rather limited.Keep neat and tight. VC1 isconnected to the main board with rigid18swg wire.

When testing the oscillator circuit,wire the unit as shown in Fig. 6, and attacha digital frequency meter via a 6.8pFcapacitor to the emitter of TR11. Applying

TO SIGNALPORT

C33

C31

14MHz R31

C

10

2

V

aC35 TR11

R36 R37

C40

TC2

Ole21MHz

28

42.0","") tiarsNoel"7-64-1

41414"4"3)°so-to°

SCREEN _J

off7..7)--BAs

14-°

mr0 0

Ertel 1[10A

Note The extra holes surrounding L3 and L4 on the PCB layout enable the use ofTO80 ready made coils type no 301 KN 0800 as direct substitutes for L3 and L4

Oscillator/low pass filter PCB la out/7t 1

HF ANTENNA

O

LPF-10. SWITCHING

VIA SW1b

O

HAM RADIO TODAY AUGUST 1983 11

Page 12: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

HT to one of the oscillators, adjust L3 untiloscillation occurs. Changing to the col-lector, tune the second harmonic byadjusting TC1. As TC2 and L6 areresonated the output signal will appearacross D9, and hence into the 50A -dummyload. The output voltage is rectified by thediode, and monitored by the meter. Ad-justments can be made until maximumvoltage is obtained. Switch off all supplies,and connect the boards as shown in Fig.4into the VHF transceiver via a powermeter. Connect a suitable antenna andtune the preselector via VC1 for maximumsignal strength. The peak setting is thesame in both transmit and receiveconditions. Activating the transmittershould cause a response from the relays.Check that power input is correct, and ifRF switching is used, adjust VR1 for asuitable delay time. Operation was foundto be quiet and effective. The author waspleasantly surprised to find that thetransverter still gave appreciable poweroutput when driven with '/2 watt, eventhough the 30dB pad was chosen foroptimised performance. As SSB/CW wasrequired at '4DHF, the relatively lowwattage of the attenuator resistors werefound to be quite adequate as the low dutycycle gives sufficient time between peaksignals to dissipate the heat. When 10metres FM is used it is best to keep theinput power as low as possible, as ratherlarger wattage resistors would be requiredin order to cope with the increaseddissipation.

KitsA complete set of parts including

the two PCB's (drilled), all com-ponents, switch, relays, cores, air -spaced capacitor, wire etc, excludingthe crystals and screens is available

L.F

from WPO Communications for£61.00 including VAT & p&p.

We suggest you purchase thecrystals as follows:

58MHz - ex Ambit International,200 North Service Road,BRENTWOOD, Essex. CM14 4SG,price £3.71 inc.

The 61.5 and 65MHz units can be orderedfrom QSL Ltd. PO Box 19, Erith, Kent.These cost £5.23 each with delivery in twoto three weeks. State HC -18U, 5th overtone,series resonance when ordering.

Acknowledgements

The author would like to thankG3UWD for initial testing of thetransverter; to G3RKL and TheUniversity of Sheffield for use of thetest equipment, and in particular toG8PNX and G4CYA who, in the true

Tx R. -12V OSCILLATOR

spirit of amateur radio, have freelyoffered advice and materialassistance - often at the mostunsociable hours in the earlymorning!

Additionalconstruction notesfor G4DHFtransverterby Tony Bailey G3WPO

There are a number of points worth notingwhich will aid construction as follows.

Main PA/input circuit PCB

Start the assembly of this board byinserting lmm PCB connection pins at thepoints marked on the drawing.

RELAYCONTROL

LINE

0 CONNECTION PIN

-LEAD SOLDEREDTO TOP FOIL

NOTECOAX LINK ON UNDERSIDEBETWEEN POINTS 'A" AND 'A'

Main PCB layout

12 HAM RADIO TODAY AUGUST 1983

Page 13: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

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Then assemble the componentslocated between RLY4 and RLY1, startingat the top edge of the board and workingdownwards as far as TR3/4 and the Incapicitors. All earth connections are madeto the top of the PCB foil, keeping leads asshort as possible. Transistors should sitwith their undersides about 4-5mm abovethe PCB surface - note that the emitter ofTR1 is soldered to the top foil.

The orientation of resistors mountedvertically must be observed with the bodyin the position shown to avoid signalradiation from the leads. Also watch out forcorrect polarity of the diodes and tantalumcapacitors.

The remainder of the components cannow be inserted, working round the board,orientating them in the positions shown.Pin 1 of the SBL1 is at the end of thepackage which has the letter "M" of the"MCL . . ." legend stamped on top.

When winding the five ferrite blocktransformers, one turn is taken as a wirepassed through one hole and back out theother - therefore one winding will have itswires at one end of the core, and the otherwinding at the opposite end. The tappedwindings are probably easier made byusing two lengths of wire twisted together,with the join as the tap. The space withinthe cores for the windings is fairly tight sotake care when winding, keeping thewinding neat and tight. The eight turnwinding requires two lengths of wire approx-imately 15cm long, the four turn windinglength around 15cm and the two turn length9cm.

The 5 turn ferrite bead chokes use10cm of wire for winding.

Both TR5 and TR6 have one leadearthed to the top foil, and in the case ofTR5, the same lead is also soldered on theunderside of the board. TR7/8/9 shouldeach be mounted so that the underside ofthe case is no more than 3mm above thePCB, to help stability. Each requires aheatsink, and some slight bending of theheatsink vanes may be required to avoidthe screen and block toroids, dependingon the types of heatsink used.

LI/L2 should be made next, followingthe detailed drawings. The cores are heldin place about 3mm above the PCB usingepoxy resin adhesive, with a separationbetween the cores of 5mm. The 10 turnwindings need 18cm of 30 swg wire each,and the 2 turn, 5cm.

The last item to be fitted is a tinplate,or double sided PCB, screen, 15mm high,to isolate the input and output signals fromeach other. Don't forget to solder the coaxlink between the points marked A and A,on the underside, using miniature coaxialcable, the braid earthed at both ends.

Oscillator/Low passfilter board

14.2MHz: worst spurious - 48dB wrt fundamental.

21.2MHz: worst spurious - 44dB wrt fundamental

28.2MHz: worst spurious - 44dB wrt fundamental

Spectrum analyser photos showing spurious outputs on each band atThis PCB is fairly simple to assemble. After nominal rated output power. Vertical deflection 10d13/ div; horizontalinserting the connection pins, carry on deflection 10MHzI div.

14 HAM RADIO TODAY AUGUST 1983

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L2a

Out

Solder to top and1 bottom4 plane

VC1

L2

L2a

Fig. 3. Assembly of LI and L2

To VC1

L1

L1a

Hold cores fast withepoxy resin adhesive

round the rest of the board, soldering upone oscillator section at a time. Again keepleads as short as possible, and orientatebodies of vertical mounting resistors in thepositions shown.

When winding the six coilscomprising L5 and L6 (two for eachoscillator), it is important that the correctwinding direction is used on the mandrel,as otherwise the diode tap cannot be madein the correct place. Each coil is wound bytaking a 15cm length of 18 swg (1.25mm)wire, and winding round a 7/32" mandrel(such as a drill) so that the windingprogresses anticlockwise from left to right.If you start the winding by having the wireunder the mandrel, and then bring it upover the back towards you, continuing towind to the right, you will get it correct.

Six of these coils are required, threeof them with the insulation scraped off at1.25 turns from the end nearest the 1nFdecoupling capacitors. Tin the exposedcopper before putting the coil into thePCB, then solder the diode into place, withthe banded end against the PCB. The otherend can then be clipped off just at the pointwhere it meets the tap made earlier, andthen be soldered.

The low pass filter inductors, woundon T50-6 (yellow) toroids, need 22cm of 22SWG (0.71mm) wire for the 12 turn ones,and 18cm for nine turns. Space thewindings out evenly over the cores, andinsert them so that the cores are restingagainst the PCB before soldering. Thecapacitors associated with these inductorscan be silver mica or ceramic types.

Although HC/18-U crystals (wireleads) are preferred, HC/25-U (pins) typescan be used providing care is taken whensoldering them into place.

Place screens in the positionsindicated by the dotted lines, of tinplate ordouble sided PCB material, again 15mmhigh.

An 18g aluminium screening plate isrequired cut to the same outline size as thePCBs. This is sandwiched between the twoassembled circut boards - the drawingshows how the boards are mounted. In theprototype shown, VC1 was alsoaccommodated on this screen, mountedon an additional side piece which hadbeen bent down. Whether this is done willdepend on the type of air -spacedcapacitor used, and whether the whole

Rly4

Tx/Rxht12V+

Rly1

DHF 2/HF A

Rly2

Rly3

r

Point for relaycontrol in linear

( Note sDHF A is mounted on topof DHF B with aluminium screen)

Fig. 4. Interconnection of main PCB

VC1

h t +12V

L /0

X1 65 MHz

X2 61.5MHz

X3 58 MHz

DHF 2/HF B

1 0 m

15m

20m

-

Rly 5

Rly 6

HF

Ant.

SW1(a) SW1(b)

HAM RADIO TODAY AUGUST 1983 15

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Totronceiverside of C1

R6

RFC

luH 100k

TR1

TR2

Fig. 5. Modification for full switching with the FT290Osc. output

Fig. 6. Oscillator alignment

assembly is going to be mounted inside acabinet (which is recommended as thealready excellent output spectrum will beeven better).

If the leads from the PCB to thesections of the capacitor are more than afew cm long, then a screen will need tobefitted so that the two leads cannot 'see' eachother and spoil the action of the filter.Rigid 18 or 20 swg wire should be used forthese connections.

When wiring the unit up, usescreened audio cable for each of the + 12Vconnections to the oscillators, and shortlengths of miniature coaxial cable for thePCB RF interconnections.

AlignmentYou can get away with aligning the unitusing received signals to peak theoscillator coils. A grid dip oscillator orwavemeter could be used instead of thefrequency counter to check that oscillatorchain operation is at the correct harmonic.If you can though, use the method given byG4DHF for best results.

Additional attenuatorpad details.For 100mW o/p VHF rig, RI, 2 = 33R,

R3 = 22R all 0.25 WattFor 300mW o/p VHF rig, RI, 2 = 39R,

R3 = 1OR all 0.50 WattFor a 10 watt o/p rig, use an additional

outboard attenuator pad of 5dB withR1,2 = 15R and R3 = 82R (use higherwattage resistors, or series/parallelconnection of 1 watt resistors), and feedthe output of this into the 30dB pad.

Fig. 7. (below) Assembly of PCBs.

6BA WASHER

20mm THREADLENGTH

6BA BOLT

PCB 2/H F-A

6.4mm 6BASPACER -1°''

2r.6BA WASHER

6BA FULL NUT

12mm THREADED6BA SPACER

PCB 2/H F -B

6.4mm THREADLENGTH

6BA BOLT

-11--1

6.4mm 6BASPACER

16 HAM RADIO TODAY AUGUST 1983

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41.11"1. 0011010110.Basic Maths for RAE Students by Bill Sparks G8FBX

Many years ago when AlexanderGraham Bell was first experi-menting with the telephone, hewanted a unit of sound measurementto indicate that one sound was justdiscernably louder than another. Hecalled this a bel. It was later foundthat the ear behaved in a logarith-mic way as a receiver of sound. Inorder to cover the wide range ofsounds the ear, at low levels, is verysensitive and the louder the sound,the lower the sensitivity of the ear.This variation in sensitivity was ex-actly as shown in our original tableof 10° to 106 and upwards, so from100 to 101 was taken as 1 bel, 101 to102 was a further bel so obviouslythe ratio of one sound strength toanother could be found by sub-tracting the indices or adding as re-quired.

For radio use the bel was toocoarse a relationship so 1' is th belswere used and these were calleddecibels (dB). Looking at thelogarithmic table we find that bymultiplying our decimal values ofindices by 10 we now have decibels.(10 decibels = 1 bel).

ie 10x1og 1 = 000010x1og 2 = 3.0110xlog 3 = 4.7710xlog 4 = 6.0210xlog 5 = 6.9810xlog 6 = 7.78lthclog 7 = 8.4510xlog 8 = 9.0310xlog 9 = 9.4510xlog 10 = 10

For instance, if a power level at 1 isincreased to 10, it represents 10 dBof gain. If we had a power level of 1and increased it to 2, we would have3 dB of gain; by increasing to 4 wewould have 6 dB, by increasing to 8we would have 9 dB and by increas-ing to 16 we would have 12 dB or

Part 2. Logarithms and dB

1012. Note that the value is greaterthan 1 and less than 2 so the valuemust be between 10 (10') and 100(102). It is actually 16.

NOTE: 102 = 100 so 20 dB = (2 X10) = a power gain of 100. Usingthis technique we can indicate theratio of any power level to another indecibels. Bear in mind that we sayratio since decibels are not absolutevalues but only ratios. They becomeabsolute values when they are refer-red to any starting point. For thepurpose of the RAE Part 1 paper re:power output indication, the refer-ence is 1 watt of power so 26 dBW is26 dB reference to 1 watt. Since 26= 2.6 in logarithms and 2 is 102 or

.100, and 0.6 is 4 on our logarithmicscale then 26 dBW = 100 X 4 (1026= 102 X 1026) = 100 X 4 (approx)in power gain and this is the same assaying CO watts output. Referring to1 watt as the start we write this as 26dBW.

Recapping it has been establi-shed that the index figure shows thenumber of '0's in the actual numberitself. Also that, in a decimal nota-tion, the decimal point acted as acount of 1 when counting thenumber of '0's in the fraction. Wecan show fractions of 10 by showingthe number of '0's in the denomi-nator of the fraction with an index inexactly the same way as for numbersgreater than 1. But now, in order toshow that we are dealing with adecimal fraction less than 1, weplace a negative sign in front of theindices.For example:

0.1 = = 10 1 X 1 Note one '0'in fraction

0.01 =- = 10-2 X 1 Note two '0'sin fraction

0.001 = = 10-3 X 1 Note three'0's in fraction

and so on.

There are figures down to 10-18 insome calculations so the usefulnessof this shorthand way of writing isself evident.

eg 1

1, 000, 000, 000, 000, 000,000

can be written as 10-18 X 1

Note that multiplication follows inexactly the same way:

=10 103 Ica)

so 0.1 x 0.01 = .001

and 10-1x10-2 = 10-1+ -2=

We simply add the negativestogether.

Roots

10 3

The only other arithmetical point ofconcern is the square root. If anumber is multiplied by itself we saythe number is 'squared'.

Example: 4 \ 4 = 16 so 42 = 16

Now, 16 consists of two equalnumbers multiplied together. 16 islike a tree with two equal roots, 4 X4. Thus 4 is called the square root of16. As you can see from Fig. 2,multiplying 3 X 3 gives 9 and if youlook at each of the small squares wehave 9 equal size squares made upfrom 3 X 1 one way and 3 X 1 theother way so 3 is called the squareroot of 9.

Other numbers with theirsquare roots (f means square rootof):

HAM RADIO TODAY AUGUST 1983 17

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4 = 2 X9 = 3 X

16= 4 X25 = 5 X36 = 6 X

23456

81 = 9 X 9144 = 12 X 12225= 15 X 15625 = 25 X 25

so f4 = 2so /9 = 3so f16= 4so f25= 5so /36 = 6so /81 = 9so "144 = 12so /225 = 15so /625 = 25

3

3

1 2 3

4 5 6

7 8 9

Fig.2.

3x3=9n- =9

4= 2 X 2 so f4= 29= 3X 3 so f9= 3

16= 4X 4 so f16= 425= 5X 5 so f25= 536= 6X 6 so f36= 681= 9X 9 so f81= 9

144 = 12 x 12 so /144 = 12225= 15 x 15 so f225 = 15625 = 25 X 25 so /625 = 25

and so on. Looking betweennumbers gives fractional squareroots. The square root of 20 wouldhave a value between /16 and /25so its value would be between 4 and5. Check it on your calculator.

In the case of indices we can ob-tain the square root very easily. If10, (X)0 = 100 X 100 then 101 = 102X 102 so by dividing the indexshown for 10,000 by 2 we have theindex of the square root.

Another example would be 1012,ie 1, 000, 000, 000, 000 which is 1

million X 1 million so the squareroot would be 1 million, 105 or 10122ie. the index divided by 2.

In the case of negative indices,an example of say V-10-18 would be= 10-9. Thus the answer would be10-9'

Nuts and boltsThis covers all the points necessaryfor the arithmetic side of the exam.The next stumbling block concernsthe correct understanding of thesimple algebraic notations used.Numbers can be manipulated justlike a mechanic uses his tools. Amechanic uses a spanner the sameway whether it is a 6mm open endedor a 45mm open ended spanner. Thesize of the spanner is not significantin the way he does the job. Thesignificance is in the way he doesthe job and the significant thing isthe method he uses. In our case thesize of the numbers are not impor-tant. It's what we do with them thatmatters. Looking at themanipulating techniques rather

than the numbers themselves, it's alot easier to understand algebra.Substituting one number for anotheryou can still use the same techniqueand get sensible answers.

Example: To say 3 X 3 = 9 isexactly the same technique as say-ing 5 X 5 = 25 so why not substititea letter for the number? In this casewe could say a = 3, b = 5

so 3 X 3 = 9would be a X a = a2

or 5 X 5 =- 25would be b X b = b2

We could multiply a X b and getanother group.

3X 5= 15a x b = ab where ab = 15

We could put any number we wantagainst any letter we want providingthat a record is kept of what hasbeen done so that at the end of thecalculation, conversion back tonumbers is possible. The main useof the technique on the RAE courseis to make up formulae: any lettercan be substituted for any number.

For instance:

ab = cthen a/ c = b

because if ax b=c then c- a= band c b= a so c/ a = band est= a

Next month: Ohm's Law

::1111111111111111112 !!!!!! '__1

"You may have got through theRAE, but you're not going on HFuntil you've passed the morsetest."

18 HAM RADIO TODAY AUGUST 1983

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Taking apart

igx

the FT 101Cross modulation

Prior to the crystal filter moststages in the receiver have to handleall the unwanted signals for a fewhundred kilohertz either side of thewanted station. Consider the 40metre band after dark. Hundreds ofpowerful stations in some cases run-ning Megawatts, are operating in-side and just outside the amateurband, and if a great deal ofamplification is used, these signalswill completely overload the frontend of the receiver and crossmodulate with each other producinga steady background mush. Reduc-ing the amount of amplification orswitching in an attenuater willreduce the overload but then theweaker amateur signals will tend tobecome lost in receiver noise. Overthe years Yaesu have altered com-ponent values and played with stagegain to try and strike the best possi-ble compromise, and from theFT101 Mk2onwards results - whilstnot perfect - have beenreasonable.

Part 3Improvements and

modificationsBy Harry Leeming

G3LLL

Some unofficial mods

The original FT101 Mark 1 waspretty bad for cross modulation, andin desperation many owners fittedthe 'VK blob'. This was a doublebalanced mixer made withminiature components and encap-sulated in a blob of resin about thesize of a sugar cube. If you purchasea second hand FT101 Mark 1 lookfor this item squeezed inside the se-cond mixer module PB1080. Theblob is no longer made but a similarcircuit on a small printed circuitboard is available from the FT -Clubin America. Fitting these units to theFT101 Mark 1 results in a con-siderable improvement, with anoticeable but less dramaticenhancement in later models.

A couple of years ago Plesseyintroduced a high signal level dou-ble balanced mixer integrated cir-cuit and I decided to have a go at us-ing this. The results obtained by fit-ting it in the second mixer, VK blobstyle, were disappointing; but aftersome experimenting a small circuitboard was made up fitting in placeof the first mixer. This noticeablyimproved the receiver of FT1O1sfrom the Mark 2 onwards, anddramatically improved the Mark 1.It was decided to market this unitand it is now available commercial-ly, and takes about ten minutes towire to an FT101. When this doublebalanced first mixer is installed, us-ing a double balanced mixer in thesecond stage does not seem to makemuch further improvement.

AGC system

Fig. 1 shows how the automaticgain control voltage is applied to thegate of Q1 in the RF unit. For max-imum gain Q1 has about four voltson its gate when no signal is being

HAM RADIO TODAY AUGUST 1983 19

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AGC LINEFALLS 2VPOINTFALLS 0.9V

AGC 9vLINE ZD

5.6 - 4.7V

01 x 4V 01 x 4V

82k.

IF ZENER IS POOR ATLOW CURRENTS REDUCE TO 10k

VOLTAGES SHOWN ARE APPROX WITH NO SIGNAL

AGC 9VLINE

(a)

Fig. 1. Original AGC circuit

AGC LINEFALLS 2VPOINT 'x'FALLS 2V

Modified circuit by VOHS

received. When a strong signal istuned in the AGC line voltage fallsreducing the gain of 01. Notehowever, that slightly less than halfthe voltage change arrives at thegate of Q2 - ie. if the AGC linedrops two volts the voltage on gate 2of Q1 only falls 0.9 volts due to thepotential divider action of the tworesistors. Most of the AGC action ofthe FT101 occurs in the later IFstages and under strong signal con-ditions the AGC applied to the firststage is not always sufficient to pre-vent front end overload. The follow-ing modification, which is an adap-tion of an idea by VK3NS, will befound to vastly improve the AGCaction.1) Remove the aerial, switch to 20

metres, check and note readingon S -meter at 14.2 Megahertzcalibration point.

2) De -tune pre -selector until Smeter falls to S3 and leave pre -selector in this position.

3) Remove the RF board and locateR5 which is the 100k resistorfeeding gate 2 of Q I, and removesame.

4) Fit 5.6 volt zener diode in placeof the resistor - the end withoutthe line on it going to the FETgate.

5) Refit RF board and check thatafter one minute or so that the Smeter still reads about S3. If it hasfallen below S2 replace zenerdiode first with 5.1 volt diode andtry again, and if the reading isstill below S2 replace with a 4.7volt zener diode.

6) Tune pre -selector to maximumand note that due to improvedAGC action the reading obtainedin step 1 will have fallen by aboutthree S units.

7) Reset S meter calibration controlso that reading originally obtain-ed in step 1 is once again shown.Note that the zener diodes must

be of a very low current type, or itmay be necessary to replace theresistor going from gate 2 tochassis with one of about 10k toget the modification to work cor-rectly.

Use with a 2m transverter

Several two metre transvertersand even repeater shift and FM unitsare available for those who wish touse their FT101 as a prime mover forVHF operation. The only real pro-blem is RF feedback into themicrophone amplifier stages caus-ing distortion or oscillation. Someham operators have rejectedperfectly good transverters as beingfaulty for no other reason than this.To make the FT101 suitable for usewith a VHF transverter locate theaudio board (PB1081, 1189, or 1315)and remove it. Locate the

microphone amplifier transistors Q2and Q3 and solder de -couplingcapacitors with ultra short leadsdirectly between the base and emit-ter of these transistors mounting thecapacitors on the solder side of theprinted circuit board. Thecapacitors must be low inductancedisc ceramic types and should havea value somewhere in the region of200 to 1000pF. Note that the baseand emitter connections of thesetransistors are the outer two pins,the centre pin being the collector.

Radio frequency speechprocessing and the FT101.

In the early 19701 several ar-ticles appeared in radio journals inpraise of radio frequency speechprocessing. RF speech processingor clipping is carried out after theaudio frequencies have been con-verted to a radio frequency, see Fig.2. As with any clipping process har-monic distortion is produced, but inthe case of RF speech clipping it isat multiples of the radio frequencyused. If the clipping is done at IFfrequency (3.18 Megahertz in thecase of the FT101) the distortionproducts at two, three and four timesthe IF frequency are easily remov-ed, leaving the signal clipped butfree of harmonic distortion.

Inspired by these articles I

decided to give the idea and try andwas so impressed by the results that

20 HAM RADIO TODAY AUGUST 1983

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MIC

AF

PRE AMP

AF BALANCEDMODULATOR

CARRIER

OSCILLATOR

SSB

FILTER

SSBSIGNAL

DOUBLE SIDE BANDSUPPRESSED CARRIER

OUTPUT L.

10-20dBOF GAIN

AMPLIFIEDSSB SIGNAL

CLIPPINGSTAGE

CLIPPEDSSB SIGNAL

SSB

FILTER

SIGNAL JUMPS THESE3 STAGES WHEN PROCESSORSWITCHED OUT

Fig. 2. RF speech clipping in the FT101, which will be described in a future article.

A FILTER ANDI CLIPPED SSB

ISIGNAL TO

IF'-I STAGES OF

TRANSMITTER

the idea was commercialised as theG3LLL FT101 speech processor.

And finally ...

Yaesu made the FT101 but inmany ways the FT101 also 'madeYaesu'. The Yaesu Musen companystarted operations in 1960 but it wasonly the advent of the FT101 at theend of the decade that brought thename to most hams' attention. TheF7'101 is by no means perfect but itis an extremely well made piece ofequipment that gives very great usersatisfaction. Some of its imperfec-tions even contributed to its suc-cess!

Its quirks and shortcomings aswell as its excellent points have alladded to owner interest and resultedin the formation of the Fox TangoClub in 1971* originally intendedfor FT101 owners, but this associa-tion was originally formed by N4MLwhen Milt wanted to find somethingto fill his time in after taking earlyretirement. The Club publishes anewsletter which is of great valueand interest to Yaesu owners, and towhich due acknowledgement isgiven for some of the ideas used inthis article.

Yaesu is now the largestspecialist amateur radio manufac-turing company in the world, and it

employs 750 people. Around 10% ofthem are qualified electronicsengineers. They are not too bighowever, and respond in goodEnglish to requests for advice andare extremely responsive to sugges-tions for improvements to their pro-ducts. One wonders who the unsunghero is who designed the F7'101, andif Yaesu would have become theforce it has if he hadn't!?

*FT Club, 248 Lake Dora DriveWest Palm Beach, Florida 33411,USA. A few enrolment forms areheld by the author and these can behad upon receipt of a stampedenvelope (ie. no SAE - no leaflet!)

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HAM RADIO TODAY AUGUST 1963 21

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RippingYarnsAnts in the Ant.You may wonder what on earth theheading actually means but in fact itbales the descriptions of one of thefunniest episodes experienced bythe writer in his enjoyment of theamateur radio hobby over the last 23years.

It was in 1962 that I had put upan enormous G3BXI tower in thegarden, a with a builder digging asix foot hole in the ground, in whichto put the mast's pedestal. At thetop, above a Ham M rotator, wasmounted a huge double -V beam,with three elements facing upwardsfor 20m, and three hangingdownwards for 15m. At the centre ofthe radiator, was a matching box ofmetal, on which were mounted twoS0239 sockets, one for each band,and two variable capacitor controls,the capacitors being mounted in -

By Angus McKenzie G3OSS

side. Two glass insulators inter-connected with matching arms,which fed the radiator a few feetaway from the centre which was ear-thed to the box and tower. So whatcould go wrong? The mast went upand down like a yoyo with aCroydon motor system supplied bythe manufacturer, so that I didn'thave to go out to the garden andcrank the tower up and down, butsimply press a button. The first pro-blem was the Council, for one or twoFinchley residents had grumbled.The planning oficer came roundand explained that I needed plann-ing permission to develop half asquare foot of land which was thearea of the mast. This seemed prettycrazy to me, but I had to admit that Ishould have asked for planning per-mission in the first place, despite theneighbours on both sides agreeingto the installation. Many peoplecame round to see the antenna, andeventually, permission was granted,the then Mayor of Finchley being akeen short wave listener! Afterabout two years or so, I started get-ting alarming television in-terference complaints. Everybodyin the road was moaning that theirscreens were flashing once every

22 HAM RADIO TODAY AUGUST 1983

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minute or two, when I was transmit-ting. I was totally flumoxed, and soalong came the Post Office to helpme investigate. We tried absolutelyeverything, and I had a totally cleanbill of health, the tests all being car-ried out in the evening. The follow-ing weekend, trouble again, butnothing had changed, so I thought.Along came the Post Office again,and finding no fault, stated that Iwould have to cut power down untilthe complaints ceased and then findout what the trouble was and cure it,a suggestion being made that itmight have something to do with theantenna.

Just imagine the picture in mygarden on a fine Saturday morninga few days later, in the middle ofsummer. A friend and I were pacingup and down the garden wonderingwhat was wrong. The standing waveratio was well nigh perfect on both Vbeams but my friend thought that hecould detect just occasionally aminute flicker of the needle on theSWR meter. So it came about that hewas staring at the top of the mastwhich had been lowered down toeleven feet above the grass with thetilt over facility, and he thought hesaw something strange. We found aladder, and up he went; a fewseconds later a guffaw of laughternearly made him fall off. One of thetwo coaxial cables rather resembleda traffic jam on the M4 with the roadup, for there was a line of ants on topof the coax slowly working their wayupwards and another line of them,

underneath the coax, on the waydown. On the side of the gammamatching box, was one tiny hole,about 2mm in diameter which hadnot been waterproofed, and just out-side this hole, was the ant sentrywith his little flag antler beckoningthe traffic in and out. But how aboutthe TVI? We opened up the box andthere inside was the most unbeliev-able sight, a ball of ants forming anest with the material that they hadbeen bringing up the coax forweeks, and the odd ant walkingacross the vanes of the capacitor. Alittle pile of bits of dead ant was atthe bottom of the box in a burnt coneshape, and it was quite obvious whathad been happening. The odd antinvestigating the variable capacitor,at the moment that my transmitterpeaked high power, was burnt topure carbon which then rectifiedthe speech transient, and in the pro-cess of course, generated a pulsewhich was then transmitted in theneighbourhood, causing a flash onall the TV screens. Thus every flashwas yet another ant hitting the dust.Needless to say after removing thenest, I was able to go back to highpower and for a while there were nomore TVI complaints, but just for awhile!

Last strawMy next story concerns an

amateur, who I cannot identify un-fortunately, some 25 years ago whohad saved up for months to buy anew Minimitter high power AM HF

rig and proudly staggered homewith it. His fingers were shaking ashe rapidly put on mains plug, con-nected a microphone, an aeriallead, turned on and joined hisregular 80m net just in time to catchmost of his friends. Everybodythought his modulation was superb,and his transmission was so muchstronger than it had been from hisprevious lOW rig! But after tenminutes or so, while he was transmit-ting, he was heard to should "OhGod, it's caught fire" QRT . . Oneof his friends immediately telephon-ed him and heard a rather sheepishamateur say "Well actually, I forgotto remove the straw packing aroundthe PA valve . . ."

Irate vicarAnother incident occurred at

around the same time, when anamateur took his AM rig with him tothe seaside, having asked thelandlady of a boarding housewhether he could put up a crudeaerial down the garden. She said itwas OK. He tuned up his rig on thefirst Sunday morning, on 80m, andjoined in his normal net and wasreally enjoying himself in his room,dressed just in his pyjamas with teaand toast at hand. He had not notic-ed that there was a large churchnext door and was just a little sur-prised when the landlady knockedon the door and told him the Vicarwanted to see him. In marched theVicar, who was obviously very irate,but wanting to be tactful. "Now,young man, are you transmitting?""Yes" said the amateur and askedwhat the problem was. The vicartold him that unforntunately theyhad a Compton electronic organand that some minutes earlier, theyhad been attempting the final hymnbefore the sermon when out came abooming voice from heaventhroughout the church saying "CQ,CQ, 80m G ---" The Vicar explainedthat this had been followed by lotsmore letters and mumbo jumbo fromheaven, together with a puzzledcongregation, with some veryscared, very elderly ladies. Thevicar had heard of amateur radioand realised it must have been so-meone very close by. And so after adelay of 25 minutes the church ser-vice resumed and everybody washappy, except the amateur, who hadto go to QRT and agreed to keep thepeace by not transmitting duringservices while he was on holiday.

HAM RADIO TODAY AUGUST 1983 23

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Go along to any amateur radio shopdisplaying the 'Hamcard Welcome' windowsticker. You will be given a sales voucher andbe sent a quarterly statement to show youhow your account stands.

HOW MUCH DOES ITCOST?

Each month an interest charge of 2%(APR 26.8%) will be added to the account.This interest rate may vary from time totime. Remember Hamcard allows you to buybefore prices increase, so significant savingscan be made.

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The choice is yours-you can spend up to25 times your monthly payment, which canbe as little as £5.00 or as much as £40.00.For example, if you decide to pay £10.00per month, then once your application isapproved, you can spend up to £250.Applications to increase the payment andlimit can be made at any time.

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Just complete the application form andstanding order and present a currentbanker's card and proof of identity Thiscredit can be increased to £800 if you show

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RTTY The LongDistance

TypewriterOne of the first requisites is tobecome a member of the BritishAmateur Radio Teleprinter Group,which is affiliated to the RadioSociety of Great Britain. By joiningBARTG, as it is familiarly known tomembers, one has the benefit oftechnical advice on all the manyproblems that beset the beginner, aspecial price for the purchase ofprinted circuits boards andspecialised components, a quarterlynewsletter containing technical ar-ticles, contest results, memberssales and wants etc. All names andaddresses which refer to BARTGwill be found at the end of the arti-cle.

There are five items which com-prise the minimum requirements forreceiving and transmitting RTTY.They are: -1) Receiver2) Transmitter3) Terminal unit (TU)4) FSK/AFSK circuits5) Teleprinter

By Ken Michaelson G3RDGPART 2

One of the firstquestions anybody askswhen taking up a newhobby is 'How muchdoes it cost?'. I can,

with all honesty, saythat RTTY is one of the

least expensive ofhobbies.

The receiver

It is possible that the first twoitems will already be part of yourstation either separately or togetheras a transceiver. But I must point outthat for reliable RTTY results thestability of the receiver, (and in-cidentally of the transmitter), shouldbe at least as good as that requiredfor the reception and transmission ofSSB. The only really necessaryfacility for an RTTY receiver is aBeat Frequency Oscillator (BFO).This is essential for FSK reception,

and therefore a must on the HFbands, but even on VHF whereAFSK may be in use, it is stronglyrecommended that a BFO isavailable so as to copy FSK, thechannel for which is 144.600 MHz.Without a BFO it is impossible to ap-preciate the great difference thatFSK makes to weak signals.

The terminal unit (TU)

Shown in Fig. 1 is a blockschematic of a straightforward ter-minal unit. Audio from the receiveris fed to a limiting amplifier whichconverts the signals into constantamplitude square waves. Thesquared off signals are then passedthrough a discriminator whichchanges the frequency of the tonesinto two DC voltages, typically -3volts for MARK and +3 volts forSPACE. The slicer stage, being ahigh gain DC amplifier merely hasto decide whether the discriminatoroutput is positive or negative and

Limiter Discriminator Slicer

Fig. 1. Block schematic

Driver Magnet

1C2 1N914

Fig. 2. TTL interfaceBC108 TTL inverter

HAM RADIO TODAY AUGUST 1983 25

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gives out a well defined signal level(+ 10 volts MARK, -10 voltsSPACE). And finally, the magnetdriver converts the slicer signalsinto suitable drive levels for theteleprinter magnet. If, however, youhave a visual display unit (VDU), itis necessary to convert thedemodulated signals into suitablelevels to operate the VDU, that is tosay, TTL levels, and a circuit forachieving this is shown in Fig. 2. Acomplete circuit for a terminal unitis given in Fig. 3. This is based onthe very successful STS design byIrvin Hoff W6FFC withacknowledgements to BARTG forthis particular version. It containsall the necessary features to getreliable copy from RTTY signals. Aprinted and drilled circuit boardcan be obtained from the Com-ponents Committee member ofBARTG for £7.65 with a reductionfor members. This price, incidental-ly, covers the additional boardwhich is required for producingFSK/AFSK signals for transmitting.(The price is correct at the time ofgoing to press).

FSK/ AFSK circuits

In order to transmit RTTYsignals it is necessary either to feeda varying audio signal into themicrophone socket of your trans-

mitter/transceiver or use circuitrywhich will give a frequency shift tothe oscillator of the transmitter. Thefirst method is termed AFSK and thesecond FSK. By far the simplermethod is AFSK, and, as mentionedabove, both the board for the TUand the board for FSK/AFSK areprovided at an inclusive price byBARTG. The second board containsall the necessary circuitry for bothAFSK and FSK and is shown inFig. 4. Assuming that numbers 1and 2 (receiver and transmitter) arealready in your possession, numbers3 and 4 are covered by the twoboards mentioned above. These canbe built for about £30 even if all thecomponents are purchased brandnew.

The teleprinter

As a machine to begin on, theCreed Model 7 and its variants arejust the job. They can take an awfullot of mishandling and, amazingly,still function as I know from per-sonal experience. The price of aModel 7 machine varies between £5and £25 according to age and con-dition. When looking for thesemachines you will often find a basicmodel number followed by a suffixwhich indicates a variation in thedesign or an additional feature. For

example, a 7E/RP is a Model 7machine with a tape reperforatingattachment. Therefore this addsrather than detracts from theusefulness of the machine.However, beware of the suffix 'RO'as this indicates that it is intendedfor receiving only and has nokeyboard. There are also othermachines of Creed manufacturesuch as the Model 54 and 75. TheModel 54 is a very fine machine,something like a de -luxe design ofthe 7E, but the Model 75is of a com-pletely different design andmechanically very complex - notone I would recommend to start on.In the case of both Model 54 and 75the advice of someone who knowsthe machine should be sought, as alarge number of these models werecoded for computer service. Themodification of a computer codedmachine is a long and difficult job,and not one to be tackled by the in-experienced. An additional facilityof which a member can avail himselfis the fact that a BARTG Committeemember holds an 'EquipmentAvailability' list through which it isusually possible to acquire ateleprinter in good working Order.

Having got all the variouspieces of gear back home and con-nected up, it may well be found thatwhen switching on the teleprintermotor, nothing but noise comes out

26 HAM RADIO TODAY AUGUST 1983

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of the headphone/extensionloudspeaker socket. Do not despair.This brings me to another facet ofRTTY:

Hash

This is a very individual prob-lem in that the amount of RF inter-ference varies greatly from motor tomotor and no two solutions are thesame. The first step to take is tolisten to all the bands that are goingto be used, while the motor is runn-ing, to see if there is a problem at all- a quiet motor is best left alone,but should RFI prove a problem,here are ten suggestions, some ofwhich may result in a remedy, or atleast an improvement.

1) Clean the governor contacts us-ing emery paper and reset the gapto .020-.025 inches. Only use a file ifthe contacts are badly pitted.2) Clean the governor slip rings -use Brasso, Brillo pad etc.3) Wire a disc capacitor (lOaF 1kV)across the governor brushes and fitsmall ferrite cored chokes (TV sup-pressor types) in the leads betweenthe brushes and the existing gover-nor filter.4) Clean the commutator using fineemery paper and thoroughly swillout with spirit. But do be careful notto overdo it as the insulation maysuffer.5) Replace the capacitors inside themotor with disc ceramics. Wire thenew capacitors across the brushesand between each brush and themotor chassis. At this point, if thereis enough room, fit small chokes (asper the governor) in the leads bet-ween the brushes and the field wind-ings.6) If the machine has any kind ofmetal silence cover or dust cover,make sure that the machine chassis,cover and base plate are all proper-ly earthed. Use short lengths of cop-per braid.7) For ground level stations, place alarge sheet of expanded metal or foilon the floor (under the carpet,linoleum etc) to form a capacitanceto earth. Connect this to theteleprinter chassis by as short a leadas possible - wide copper braid orstrip is most suitable. Don't forget toconnect the sheet to mains earth as asafety measure.8) If not already in use, use an isola-tion transformer between the mainsand the motor.

9) Use a screened cable between theterminal unit and the teleprinter,and include small decouplingcapacitors.10) Use coaxial cable to feed theantenna and site the antenna as faraway from the teleprinter as possi-ble.

All this may seem a great deal ofwork but, in my experience, I havenever found it necessary to use morethan two or at the most, three of thesuggestions. They are given to youas various alternatives.

Speed

Most Creed Model 7s aredesigned for a motor speed of 3000rpm which corresponds to ateleprinting rate of 50 bauds, as Idiscussed in the previous article.This is the speed of most commercialtransmissions, but is not of great usewhen copying amateurs, exceptperhaps on VHF where the practiceof using 50 bauds is spreading.However, this does not pose a greatproblem as the Creed Model 7governor can easily be adjusted forthe lower speed of 2727 rpmnecessary for copying amateurs us-ing 45.45 bauds. However,whichever baud rate is used, it isnecessary to arrange some schemefor measuring the motor speed. Anewly bought machine therefore,unless the seller was an amateurwho had used it on 45.45 bauds, (seemy comment above about the'Equipment Availability List'),

should first be checked to see that itis running properly at 50 bauds byusing the following method. Stick apiece of white adhesive tape about aquarter of an inch wide from thecentre of the governor face to therim so as to give the appearance of asingle 'Spoke'. Start the motor andwatch the face of the governor in adarkened room by the light of aneon lamp connected to the 50 Hzmains. A 2 bladed butterfly shapedfan will be seen. If the motor is runn-ing fast the fan will appear to rotatein the same direction as the motor,but if the motor is slow the fan willappear to rotate in the oppositedirection. Switch off the machineand adjust the screw seen throughthe hold in the rim of the cover untilthe fan appears stationary. This will,of course, mean that the motor willhave to be switched on and off a fewtimes to adjust the screw. When thefan appears stationary the motor isrunning at 3000 rpm. The governorscrew should now be turned sevenand a half turns in an anti -clockwisedirection to reduce the speed to2727 rpm for 45.45 bauds. An im-portant thing to remember is the factthe machine prints correctly onlocal copy is no evidence that thespeed is correct since the motor iscommon to both the transmitter andreceiver of the teleprinter.

Operating

Having got so far the time hascome to see the results of all yourwork and switch on . . . First tune

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HAM RADIO TODAY AUGUST 1983 27

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around 14090 kHz to try and find anamateur transmission. These can berecognised by the pauses betweencharacters because the operator atthe distant end is using the well-known 'hunt and peck' technique.While he looks for the next letter tosend the signal will remain in asteady mark state, and when the keyis pressed there is a short burst of'warble' followed by another periodof steady mark tone. Even with ex-perienced amateurs there will stillbe pauses which would signify thatthe transmission is of amateurorigin.

Assuming that your receiver hasa separate control for the BFO, tuneit for maximum signal strength andadjust the BFO to give a peak

reading on the tuning meter. Oncethis setting has been found the con-trol should be left well alone and allthe tuning done on the receivermain dial; this will apply also if noseparate BFO control is provided,such as in a receiver/transceiverdesigned for SSB.

Switch on the teleprinter motorand watch what is being printed. Ifthe machine produces garble andraces between characters it is con-nected upside down. A good indica-tion of this is when a string of'SYSYSYSY' is printed. Change the'Normal/Reverse' switch, S2 on thecircuit in Fig 3, and the printout willchange to 'RYRYRYRY' which is thestandard RTTY tuning signal. Butexpect a number of disappointments

to begin with .. . it takes a littlepractise to get results.

If no amateur signal can befound, or the receiver in use doesnot cover a convenient amateurband, it should be possible to findsome other narrow shift transmis-sions elsewhere in the HF spectrum,probably with a speed of 50 bauds.This will mean rotating the screwseen through the governor rimseven and a half turns clockwise,remembering to screw it back theother way when endeavouring tocopy amateur signals. However, youwill find that there are a lot of com-mercial signals which are incom-patible with the relatively simplereceiving equipment in use, so don'tbe too disappointed if you are

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28 HAM RADIO TODAY AUGUST 1983

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unable to get any sensible copy tostart with. Try the higher part of the14MHz band, or, if you possess ageneral coverage receiver, tunethrough the £3MHz band. I am quitesure that you will find some sort ofcopy there.

If by now you feel sufficientlyconfident, then switch on thetransmitter and have a go. I must tellyou at this point not to worry abouttyping speed . . . RTTY is not a rat -race, not even in contests. Most RT-TYer s are very tolerant ofnewcomers. The only thing is this:do keep you overs short. Fiveminutes is enough to start with in theearly days and never over tenminutes.

If joining a QSO or replying to aCQ call try and zero beat your markfrequency with that of the other sta-tion, and then start your transmis-sion with half a line of RYRYRYRY (ithelps the other operator to tune youin). Follow this with CarriageReturn (C/R) Linefeed (L/F) Letters(LTRS) G4XXX G4XXX de G4YYYG4YYY C/R L/F LTRS LTRS... andyou're off! (Its also a nice practice totype in the time in GMT, after thecallsigns; if nothing else it makeslog keeping much easier). At theend of every line send at least onesequence of C/R L/F LTRS LTRSand in conditions of weak signals,QRM etc, throw in a few more forgood measure. As with all modes, agood number of hours spent listen-ing/copying before actually turningon the 'Transmit' switch gives in-valuable operating instruction.Shown in Fig. 5 is a copy of an ac-tual RTTY QSO which I had withG3MEJ on 144.600 MHz FSK.

ro RUIOVI

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Fig. 6. Typical Creed 7 motor assembly

Activity

Most amateur activity will befound on the HF bands especiallyaround 14090 KHz, but there is astrong and growing interest in VHFprinting on 144.600 MHz (FSK) and145.300 (AFSK) with a little activityon 70cms. There is now an RTTYrepeater operating on 70cm. Underthe terms of the new licence(January 1977) British amateurs areallowed to transmit data on VHF andhigher frequencies so that from timeto time signals may be heard whichjust print garble. Under the latestlicence schedule (22nd March 1982)amateurs are now allowed totransmit RTTY on 160 meters bet-ween 1.810 and 1.850 MHz at thesame power input as that used forphone transmissions on this band.

On the HF bands amateur RTTY

CO CO CQ CQ CO CQ DE G3RDG G3RDG G3RDG G3RDG G3RDG G3RDGCO CO CO CQ CQ CQ DE G3RDG G3RDG G3RDG G3RDG G3RDG G3RDGCO CQ CQ CQ CQ CQ DE G3RDG G3RDS G3RDG G3RDGG PSE K K K

RYRYRYRYRYRYRYRYG3RDG G3RDG DE G3MEJ G3MEJ.... HALLO THERE KEN HOWS THINGS?G3RDG DE G3MEJ PSE K

RYRYRYRYR2133 GMTG3MEJ DE G3RDG....OK THERE PAUL. NICE TO WORK YOU AGAIN.I CALLED YOU THE OTHER EVENING BUT YOU MUST HAVE BEEN OUT.I GOT NO ANSWER. YOJ ARE 589 589 WITH ME THIS EVENINGSO BTJ.. G3MEJ DE G3RDG PSE K K

RYRYRYRYRG3RDG DE G3MEJ FINE KEN. WELL I HAVE JUST HAD A CALL FROMDOWNSTAIRS SO I WILL SIGN WITH YOU NOW. SEE YOU AGAIN SOONG3RDG DE G3MEJ AR SKG3MEJ DE G3RDG OK PAJL WELL IT IS A SHORT ONE BUT ALL THE BESTTILL NEXT TIME.G3MEJ G3MEJ DE G3RDG G3RDG AR 3K... TIME 2145 GMT

Fig. 5. RTTY contact on 144.600MHz FSK.

is transmitted as FSK in the upperpart of the CW sub -bands, for exam-ple in the 3.5 MHz band our slot isaround 3.590 MHz. The other RTTYfrequencies over the amateur spec-trum were given in my previous arti-cle. On VHF two modes are in use asmentioned above. AFSK on 145.300MHz is used for local 'ragchews'with a range of about the same asphone, and 144.600MHz FSK whichis used for greater distances.

Of all the bands, twenty metresis the most popular but Sunday mor-nings produce a high 'G' activity on80 metres before and after the BAR -TG mid -day news bulletins. Thereis also some activity on 40 metres(7040kHz), and the Continentalcountries are active most eveningsfor those who prefer to range furtherafield. VHF printing variesthroughout the country so I suggestthat you contact local RTTY en-thusiasts to check on the level of ac-tivity in your area. BARTG providesmembership lists to all its membersannually and to new members onjoining.

Each week there are severalnews bulletins transmitted, the mostwell established being that ofPAOAA (Fridays 2030 GMT on3.600MHz + or - QRM at a speed of50 bauds). PAOAA also transmitsthe bulletin at the same time on14090kHz at a speed of 45.45 bauds.There are several German newsbulletins transmitted at varioustimes on Sundays. There is also theBARTG news bulletin which istransmitted by various stationscovering most of England andWales, primarily on 2 metres, but

29HAM RADIO TODAY AUGUST 1983

Page 30: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

there are two stations transmittingon 80 metres, and another on14090kHz. At the time of going topress there are 18 different stationstransmitting the bulletin at varioustimes during the Sunday from 1130to 2030 local time. Most of thetransmissions take place, as men -honed above, at about mid -day. Fullparticulars of the BARTG newsbulletin schedules are given in thequarterly Newsletter.

Contests

Throughout the year a numberof RTTY contests are organised. Theresults of the HF contests contributeto a World-wide RTTY champion-ship. BARTG sponsors two of thesecontests, an HF one held in the Spr-ing and a VHF one held in theAutumn. There are also many othercontests organised by various na-tional societies, and for informationon these the BARTG Newsletter isinvaluable.

So all that I can wish you is goodluck in your efforts. The thrill ofyour first QSO using RTTY will besomething to remember.

Names and addresses: Secretary

Fig. 7. Creed seriesfield motor governor

General correspondence) E. Batts,G8LWY, 27, Cranmer Court, Rich-mond Road, Kingston-upon-Thames, Surrey KT2 SPY.

Membership and subscriptions.Mrs T. Crane, "Greta Woods",Bromley Road, Ardleight, Col-

chester, Essex C07 7SF.The annual subscription to

BARTG is £3.50 with a joining fee of50 pence. Acknowledgement ismade to the British Amateur RadioTeleprinter Group for certain sub-ject matter and circuitry used in thisarticle.

AYEPM COMPONENTS LTD. VALVE & COMPONENTS SPECIALISTS

SELECTRON HOUSE. WROTHAM ROAD, MEOPHAM GREEN, MEOPHAM, KENT

PHONE 0474 813225. TELEX 966371 PM COMPNEW BRANDED VALVES

A2087 11.50 CC807 2.50A2134 14.95 ECF80 0.72A2293 6.50 CF82 0.60A2900 11.50 CF86 1.70

011464 115.00 CF806 10.25DAF91 0.45 ECH3 2.50DAF96 0.65 CH35 1.60DET22 28.00 CH42 1.00DET24 35.00 CH81 0.58DF91 0.73 CH84 0.69DF92 of C LBO 0.60DF96 0.65 CL82 0.65DK9 1 0.90 CL84 0.74DK92 1.20 C186 0.74DK96 2.50 CLL800DL92 0.60 16.95DL96 2.50 F374 2.00DLS 1 0 8.00 F39 1.00OLS16 10.00 F42 3.50Dm160 2.75 F55 2.25DY86/87 0.65 F80 0.55DY802 0.72 "3 3.50

F85 0.5080CC 7.0080CF 13.5080F 13.5081CC 3.50B2CC 3.5083CC 3.5083F 3.5086C 9.5088C 6.0088CC 2.601301 19.95180F 6.501 82CC 9.00

18101 16.00ABC8O 0.65

F42 1.20B91 0.52BC81 0.85BC91 0.75BF80 0.50C80/0 6.00C90 0.70CC81 0.85CC82 0.55CC82 Philips

1.10CC83 0.65CC8b 0.60CC88 0.88

ECC91 2.00 p -o,N91CC804 0.60 N

F86 0.95F89 0.85F91 1.25F92 2.50F93 0.69

EF94 0.55EF183 0.65EF184 0.65EF804S 11.80EF806S 14.60EH90 0.72K90 0.72

EL34 P8,11,893.50

EL34 2.25L36 1.50L38 6.00L82 0.58184 0.69185 4.50L86 0.851,90 1.25L360 7.95L519 6.95M80 0.70M81 0.70M84 1.10

1.101.101.10450

E784 6.95EY86/ 87 0.50EY88 0.55EZ80 0.60EZ81 0.60EZ90 0.9601/3716

30.00055/16 9.00GS 1 OC 12.00GXU50 12.5007501 1.20GZ30 1.00GZ32 1.00G233 4.50GZ34 2.15GZ37 4.50KT61 3.50KT66 USA

6.95KT66 UK 9.95KT77 9.50KT88 USA

7.95KT88 UK

12.50KTW61 2.00M8079 6.00M8083 3.25M8100 2.85M8137 5.50M8162 5.50ME 1400 4.00N78 14.950A7 0.85082 0.85PC86 0.80PC88 0.75PC92 1.20PC97 1.10PC900 0.75PCF80 0.65PCF82 0.60PCF 86 1.20PCF200 1.80PCF201 1.80PCF801 1.35PCF802 0.60PCF805 1.25PCF808 1.25PCH200 1.10PCL82 0.80PCL83 2.50

PCL84 0.85PCL85 0.80PCL86 0.85PCL805 0.90PD500 3.50PFL200 1.25PL36 0.95PL81A 0.72P L84 0.65P1500 0.95PL504 0.95PL508 1.95PL509 4.85PL5I 9 4.9581,802 5.50P788 0.82PV500A 1.79P7800 0.79P7801 0.7900V02 6

12.7500V03 10

5.5000V03 20A

18.6000V06 40A

18.00C15150/45

7.00051200 3.950S1209 2.00051212 3.200W03-12 3.50U19 11.95UCH81 0.65

UF80 0.80UL84 0.86YL1020 29.00/759 19.85ZM1001 5.001X28 1.152 D21 0.957K25 24.954CX250B

37.504CX3504

71.504x1504 25.005U4G 1.005U4GB 2 505V4G 0.755240 0.856A87 0.606488 0.8664C7 2.00

64F44 2.5064G7 1.9564 H6 1.5064J7 2.0064 K6 2.0064L5 0.6264M4 3.256AM 5 6.0064N5 3.956405 1.206AS5 1.5064S7G 7.506AT6 0.7564U6 0.556AV6 0.7264W84 2 956846 0.696BA7 4.5068484 3.5068E6 0.7268D6 1.006BH6 1.956BJ6 1.206BN7 4.506BN8 2.756BR7 4.156BR84 2.156857 4.5068W6 5.3568Z6 2.006C4 0.806CH6 10.356CL6 3.506E48 2.506F6G 2.006F28 1.256GH8A 0.806GK6 2.006H6 1.356J5 1.956J5G 1.506J6 0.556J86 3.956JS6C 3.506K06 4.506L6GC 2.5061607 1.156U8 0.606V6GT 0.806X5GT 0.50787 1.407S7 3.0011E2 16.50124E6 0.85

12476 0.59

12AT7WA2.50

12AU6 1.5012AU7 0.55124V6 0.8012AX7 0.65I 24X7WA

12A77 1:8812A274 1.9512846 1.50128E6 1.05128H7 1.8012816 0.70128V7A 2.7512E1 17.9512GN7 3.9512HG7A 3.9530FL2 1.1040K06 4.5038HE 1 4.5075C1 1.70

8541 6.508542 2.009OCG 13.1592AG 11.8592AV 11.8515082 3.95150C4 2.15807 1.50811A 12.95813 18.50833A 115.005642 8.605651 3.205670 3.505687 3.505696 3.505749 2.505751 3.505814A 3.255842 8.505965 2.256060 1.506080 5.7561468 6.4568838 13.957025 2.507027A 4.657199 3.20

2.007.505.003.953.50

;3gl')74757591A866A

INTEGRATEDCIRCUITS

AN2140AN240LA4400LA4422LC7120LC7130LC7131LC7137MB37I2MC 1330PML231B519018519178SN 76003NSN 76013NSN76023NSN76033NSN76131NTAA66 I BTA7061 APTA7120TA7130TA7204TA7205APTA7222747310TBA120STBA 5200TBA 530TBA540TBA550O784641851TBA80003.48105TBA9200TDA10044TDA11700.141190TDA1327TDA1412TDA2020TDA2030TDA2532TDA2640T 042590TDA26114U PC566 HUPC575C2UPC100IHUPCI025

ILYk; ;ins'UPC1185HUPC2002H

2.502.804.152.503.253.505.505.502.000.761.754.858.851.951.951.951.951.301.203.951.651.502.151.501.801.800.701.101.101.251.453.000.891.351.652.201.952.151.700.852.452.801.951.252.951.952.952.752.502.502.752.953.951.95

SEMICONDUCTORS 8F199 0.14 TIP29C 0.42AC127 0.20 BC1708 0.15 BF200 0.40 TIP30C 0.43AC128 0.20 EIB C171 0.09 BF258 0.28 TIP31C 0.42AC141K 0.34 IIIBC172 0.10 BF259 0.28 TIP32C 0.42AC176 0.22 CI73B 0.10 BF336 0.34 TIP41C 0.45AC 1 76K 0.31 C182 0.10 BFX29 0.30 TIP42C 0.47AC187 0.25 C183 0.10 BF X84 0.26 TIP47 0.65AC187K 0.28 C1841,40.09 BFX85 0.32 TIP2955 0.80AC188 0.25 C212 0.09 BFX86 0.30 TIP3055 0.5540142 0.79 C2121 0.09 BFX88 0.25 TIS91 0.20AD149 0.70 C213 0.09 BFY50 0.21 2 N3054 0.59A0161 0.39 C213L 0.09 8 FY51 0.21 2N3055 0.5240161/20.90 = C237 0.10 El FY52 0.25 2N3702 0.1240162 0.39 C238 0.09 BFY90 0.77 2N3704 0.12AF 124 0.34 :C307 0.09 BT106 1.49 2N3705 0.12AF125 0.35 C327 0.10 BT108 1.49 2N3708 0.12AF 126 0.32 C461 0.35 BT116 1.10 2N5294 0.42AF127 0.32 C478 0.20 BU105 1.22 2N5296 0.48AF139 0.40 C547 0.10 BU108 1.69 2N5496 0.65AF239 0.42 C548 0.10 BU124 1.00 254715 0.95AU106 2.00 C5494 0.08 BU126 1.60 2SC495 0.80AUI07 1.75 C557 0.08 BU205 1.30 2SC496 0.80AU 1 10 2.00 C558 0.10 BU208 1.39 2SC10960.80AU113 2.95 D131 0.32 802084 1.52 2SC11731.15BC107 0.10 D132 0.35 BU326A 1.42 2SC13061.00BC108 0.10 D133 0.40 BU526 1.90 2SC13071.50BC1098 0.12 0135 0.30 MRF450A 2SC1449 0.80BC139 0.20 0136 0.30 11.50 2SC16781.25BC140 0.31 D137 0.32 MR F453 2SC1945 2.10BC141 0.25 D138 0.30 15.50 2SC19530.95BC142 0.21 D139 0.32 ARF454 2SC19570.80BC143 0.24 D140 0.30 23.50 2SC19691.95BC147 0.09 F179 0.34 MRF475 2.50 2SC20281.15BC148 0.09 F180 0.29 MRF477 10.00 2SC20291.95BC149 0.09 F183 0.29 0071 0.40 2SC20781.45BC157 0.12 F194 0.11 R2008B 1.70 2SC20910.858C158 0.09 F 196 0.11 R20108 1.70 2SC2166 1.95BC 159 0.09 F197 0.11 R2540 2.48 25C2314 0.80BC160 0.28 F 198 0.18 '111'29 0.40 2SD234 0.50

Many other items availablePlease phone send list for quote

Goods normally despatched within 24 hours

CALLERS WELCOME* Entrance on A227 50yds * HoursSouth of Meopham GreenExport enquiries welcome Mon. -Fri. 9.30-5.30

P. & P. 50p. Please add V.A.T. at 15%* 24 -HOUR ANSAPHONE SERVICE *

30 HAM RADIO TODAY AUGUST 1983

Page 31: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

ORE100111C2

C6

ELEVEN TO TEN - PCB artwork, component overlays and components list

Here is the supplementary material for our feature on converting your CB tranceiver to the 10m amateur band which appearedin the June issue of Ham Radio Today.

The PCB modules shown here enable the construction of an EPROM programming board and a combined FM modulator anddiscriminator board (for use with AM/SSB sets).

Teripticace

The PCB layout for the FM modulator/discriminator board.

VR1

1116iOMER

BB

micU ° .-1R211--

R22

QOMR20

110 IFO"

8

C5 13gr!'rf12811

TR .VR2 nc0 14

0E11021

UNVCO otC.J't F2

R23

TR4

0

TR®

LI

C15

C16

C)CI7

R28

18

T R line

Modulator/discriminatoroverlay

The PCB layout for the EPROM prog-ramming board.

VCO

C1

C 2

C3 CEI

CEI

TRI

C7

TR2

C5

EIJI]C=I

R8

o o o olock phasedetect ,

. 0

9

0 0Ink

0 o

RYST41

.0 1;

1C2 - 411

-4 71oT/R0

EPROM board overlay

COMPONENTS LIST R22Modulator/Discriminator board R23RIR2R3R4R5R6R7R8R9RIOR11R12R13R14R15RI6R17R18R19R20R2I

I k2 R24IM R25

47k R26IM1k2

100k10k

220k470k270k470k160k220k2M22M2

1M

820k100k100k680

100k

R27R28CIC2C3C4C5C6C7C8C9CIOCI IC12C13C14C15 -C16

4k7IOOx

6804k74k7

100k4k7

4u7/63V470p100n

In47n470

100n4u7/63V

47n47 n

100n22n47n

4u7/63V47n47n

C17C18TR1,2,3TR4DI, 2.3D4D5ICI1C2

VR IVR2

1/35VIn

BC239"2N39061N I 418

177210 varicap1N1418

3401S L6691

IM22k

LI 455kHz IF transformerCOMPONENTS LIST

EPROM boardRIR2R3R4R5R6R7

100470

lk820k

lkIk510k

R8 lkCI 22pC2 68nC3 82pC4 47nC5 47nC6 82pC7 6p8C8 lu/35VC9 47nTR1 BC239TR2 BC239ICI MC 145106P1C2 2516 EPROMDI 5V6 ZenerLI I I3CN2K159DZ

All enquiries relating to thisarticle should be sent to:

Bill Sparks G8FBX30 Withyoornbe Road

PenkethWarrington

HAM RADIO TODAY AUGUST 1983 31

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Radio Tomorrow is our new way of presenting all diary events inone place - contests, rallies, exhibitions, DXpeditions, clubmeetings, meteor showers (if you like that sort of thing) andanything else of amateur radio interest. The easiest way to use it isto read through the guide once, marking the events that you'reinterested in. Then you can check what's happening at a glance.

If you're an event organiser, then please send information inthe same format that it appears here to Richard Lamont G4DYA,Ham Radio Today, 145 Charing Cross Road, London WC2H OEE.

Because of the large number of meetings throughout thecountry it is necessary to keep details very brief. We would like toadd a list of contact names/phone numbers for each club, so thatreaders can ask for details direct from the club concerned. As thisis the first full Radio Tomorrow this list does not exist yet, but wewould be very grateful if organisers could supply us with namesand telephone numbers (preferably evening numbers, notdaytime ones) that we can publish in a 'contact' list.

1 July Cambridge & DARC: talk planned.2 July GB4WCR at Wellingborough Carnival, Bassetts

Park, Northants.Marconi Radio Society: uses callsign G2MT forfirst time.

2-3 July VHF National Field Day (rules in April Radcom).Leighton Linslade RC: special event station atStretley Village Fete.

3 July UK FM Group (Western): DF hunt.4 July Leighton Linslade RC: meeting.

Southdown & DARS: Butts Brow meeting: bangersand beer.Stourbridge & DARS: informal meeting.

5 July Bristol ARC: VHF NHF post mortem.Fylde ARS: An Introduction to Computers by LenImber G6HEA.Kidderminster & DARS: on air (HF).

6 July Denby Dale & DARS: visit to BBC Holme Moss.Nene Valley RC: natter night.

7 July Lincoln SWC: visit to Lincolnshire StandardPrinting Group works.Medway AR & TS: social evening (at home) toSouth EssPx ARS.Shefford & DARS: VHF NFD post mortem &contest slide show.

8 July Cambridge & DARC: informal meeting/morseclass/on air.RS of Harrow: talk on HF vertical aerials.Medway AR & TS: social evening at home toSouth Essex ARS.

8-9 July

9-15 July10 July12 July

13 July

14 July15 July

16 July16-17 July

17 July

18 July

19 July

20 July

20 July -18 Aug21 July22 July

23-30 July

24 July

GB2CHI at Chichester 908 at the Guildhall,Priory Park, Chichester.Nu Geminids meteor shower (max 12 July).Shefford & DARS:. treasure hunt.Biggin Hill ARC: talk on vintage radios.Bristol ARC: on air.Brighton & DARS: visit to Police comms. centre atLewes.Denby Dale & DARS: lecture by Louis VarneyG5RV.Lincoln SWC: lecture/display on electricitydistribution by EMEB.Nene Valley RC: WAB award scheme and 160moperating by G3ONTShefford & DARS: junk sale.Cambridge & DARC: talk planned.RS of Harrow: informal & practical evening.Leighton Linslade RC: family picnic.GB4CHG at the Corby Highland Gathering.3.5MHz Field Day.Cornish rally, Camborne Technical College.Sussex mobile rally at Brighton Racecourse:10.30am - 5pm, £1 admission (children & disabledfree), talk in S22 & 80m (Well worth going to -Ed).Biggin Hill ARC: visit to a power station.RS of Harrow: summer madness DF hunt and Bar -B -Q.Leighton Linslade RC: The Analysis of the CircuitDiagram by J Hart G8GIK.Stourbridge & DARS: main meeting.Bristol ARC: computer evening.Bury RS: surplus equipment sale.Fylde ARS: informal meeting.Kidderminster & DARS: on air (VHF).Denby Dale & DARS: visit to BBC Moorside Edge.Nene Valley RC: natter night.

Perseids meteor shower (max 12 Aug).Shefford & DARS: natter night.Cambridge & DARC: informal meeting/morseclass/on air.RS of Harrow: talk (TBA).Nene Valley RC: visit to Northants Police HQ.GB4FES & GB8FES at Festival 83 (Christianfestival) at County Showground, Staffs.Colchester rally.

32 HAM RADIO TODAY AUGUST 1983

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24 July(contd.)

26 July27 July

28 July

29 July

30 July

31 July

1 Aug2 Aug

3 Aug7 Aug

9 Aug

10 Aug

McMichael rally at McMichael Sports & SocialClub, Bells Hill, Stoke Poges, Bucks.Opens 11am. Includes fleamarket.Scarborough rally.GB4AC for Year of the Castles in Wales.Bristol ARC: QRP night.Brighton & DARS: Foxhunting by G3WMU.Denby Dale & DARS: visit by RSGB Region 2representative Dave Smith G4DAX.Lincoln SWC: Video by G6AIL.Nene Valley RC: Microcomputers - an Insight byG4NWH.Shefford (Sr DARS: planning for September's SSBNFD.Cambridge & DARC: external social event.RS of Harrow: equipment test evening.Medway AR & TS: films (of radio interest).GB2ABC at Abergavenny (Sr Border CountiesShow.Bamohiswick rally.432MHz Low Power Contest.Leighton Linslade RC: DF hunt.Southdown (Sr DARS: open meeting at Chaseley.Bristol ARC: discussion on new constructionprojects.Fylde ARS: visit to Blackpool Airport.Nene Valley RC: video from CEGB.RSGB National Mobile Rally, Woburn.UK FM Group (Western): DF hunt.Cambridge & DARC: dress rehearsal for contest.Bristol ARC: film evening (RSGB & Spielberg).Bury RS: DF hunt.Farnborough (Sr DARS: Basic Computers byG6HIT.Lincoln SWC: on air.

Tog&zuov boar D

.the weather here, of course, is wonderful)".

a

CD.

FORTOP LTD, FIRST AND BESTFOR FAST SCAN TV.

4.44 Al

INF

ik * 1

sor

The ITT 435/R 'TV transceiver allows transmission and recep-tion of 70cms Amateur TV signals. Features 15 watts mm PeakSynch RF output, Bandwidth limiting filter, switchable modulationsense, video inputs and carrier frequencies. High performanceRX converter built in Requires aerial, 12 volts power, videosource (camera etc) and stand UHF TV set to complete fast scanAmateur TV station. £169.50 plus £2.59 P&P.

For further details please write or ring to:

FORTOP LTD, 13 Cotehill Road, Warrington, Stoke on Trent, telAsh Bank (078 130) 2607

McMichaelAMATEUR RADIO SOCIETY

MOBILE RALLYTalk -in S22 (GB2MRS)

Free car park RefreshmentsSunday 24th July at 1 1 am

Sefton Park, Bells Hill,Stoke Poges, Slough.

miurmintCW/RTTY/AMTOR/ASCII Communications Terminal£540 (incl. VAT)'ADD-ON' OPTIONS: Built-in 2 colour 40 column printer (090) Battery back-up of memory (C30)STANDARD FEATURES* Green phosphor screen.* Conventional keyboard legended for all

functions.* 10 user memories for transmit text

preparation.* Transmit/receive CW (morse) and RTTY

(teleprinter).* Fixed text stores.* Char by char. and 'page' transmission modes.CONTACT US TODAY at POLEMARK Limited. Lower Gower Road. Royston, Herts. SG8 5EA. Tel: Royston (0763) 47874 or call at one of our dealers listedbelow:-

Northern Communications,299-303 Claremount Road.

Claremount. Halifax, West YorkshireTel: Halifax (0422) 40792

* AMTOR/ASCII modules (C28):-(Available Summer '83)

* FEC, ARO and 'listen' modes.* ASCII transmit and receive.* Automatic PTT line.

* Full duplex working.* Users callsign programmed.* Self check facility.* Printer port (parallel, centronics

compatible).* External video port.* PTT control.* Phase coherent AFSK generator.* Real-time clock. in the Autumn.

South Wales Communications Ltd.,Graig-y-Master.

Penycaemarw, Nr. Usk, Gwent.Tel: Wolvesnewton (02915) 552

* STOP PRESS: SSTV board to be available

Amateur Radio Exchange.373 Uxbridge Road,

Acton, London.Tel: 01-992 5765

HAM RADIO TODAY AUGUST 1983 33

Page 34: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

TechnicalitiesUltra cheap, highperformance PAs.

Super -regenerationre -visited for 23cm.

By Frank Ogden G4JST

Sitting here, bashing out thisregular column, I feel that I mustgive the impression that everythingI do works 100 per cent first time.This, I must assure you, is at leastten million miles from the truth.

In reality, it's hard slog withprojects seldom, if ever, springinginto life at switch -on. I must statethough that if logic (of the thoughtkind) has been applied in thedesign, most things work eventual-ly. Beyond the wiring of a main plug(99 per cent success rate) a new pro-ject will nearly always need someadjustment while I find that I amforever thinking of new ways to ad-just old ones. The topics for the col-umn this month are non workingproof of fallibility.

An HF power devicefor 88p

Our Project Omega all mode HFtransceiver system calls for thedesign of both a QRO and a QRPoutput stage. This translates to out-put power requirements of 100Wand 5W respectively. Furthermorethe linearity of the output stage mustbe flawless, deliver the rated powerover the range 1.8 to 30MHz, ifpossible produce little noise in theoutput spectrum and, last of all, notcost and arm and a leg to build.

The obvious thing to do wouldbe to press some of the 12V 2m FMtransistors into HF linear service.They are relatively cheap and ob-tainable and very efficient over theHF band. Unfortunately, devicessuch as the 2N6084 are ballastedsufficiently to avoid 'hot spotting' onthe silicon die but not enough forreally good linear service.

They are also relatively fragile.The collector base breakdownvoltage is low, and if exceeded for along enough time, will surely result

Output 5011

EVE

BOO° transmission Trifilor transmission Bill nr tran missionline transformer line transformer line transformer

Fig. 1. 100W broadband HF amplifier. The total cost is around £12 butthere are problems though. See text.

Ferrite core.10 x Neosid( 28-012-31

B

in device failure. Given the induc-tive transformer arrangementstypically used in HF linears, thechances of an energy bolt smashinga junction to bits is very real.

There are a number of HF SSBdevices on the market which arevery robust but just look at theprice. Quite ridiculous. My answeris to use gangs of cheap, plasticpackaged MOSFETs in conjunctionwith power splitters, etc, to bringthe total power up to the desiredlevel.

I have given a 'for instance' inFig. 1. Each transistor is a VN66AFpower MOSFET costing around 85peach. Manufactured by Siliconix,the same basic chip is used in thecompany's stripline package VMP4.Individually, the transistors willpass up to 2A of drain current, standoff up to 60V across the channel andshow similar RF characteristics to abipolar transistor with an Ft in the600MHz region. All in all, the basicchip RF specification is excellentalthough the device's plasticpackage does pose a few problemswhen you want it to do somethingmore interesting than drive a printhammer.

Here is, roughly speaking,where I came in. I haven't got theeight transistor £12 HF amplifier towork properly yet. No matter what I

do, the wretched thing takes offaround 70MHz and oscillates veryrobustly indeed.

This particular prototype hasbeen contructed with the main out-put transformer consisting of twostacks of five ferrite ring cores eachwith two transistors at each corner.The two single turn primary win-dings emerge at opposite ends of thecore stack to connect with theparalled drains.

I have had the design workingbriefly but the whole thing is undulyfussy about layout, and absolutesymmetry of design is quite critical.The transistors themselves needeither to be very carefully matched(you try getting eight the same!) orfitted out with individual bias potswhich is a hassle. However, thepossibility of a really good HF ampfor next to nothing will keep mymind applied to the project and Iwill let you know the secret of suc-cessful design when I have foundout myself. In the meantime, howabout someone at the SiliconixSwansea application labs taking upthe problem? Or anyone else forthat matter. One thing is sure. Oncethe design is cracked, it is in-conceivable that anyone would wantto build HF gear with anything otherthan plastic packaged powerMOSFETs.

34 HAM RADIO TODAY AUGUST 1983

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To ALCcircuitpoint A

Input80mV1.8 to30MHz

20t tapped at Lt Irom supply endon Neosid 28-002-31 core

320t tapped at St onNeosid 28-002-31 core

RFC

VB

2 x 10k pre-set

10n 16t on dust .=.core 0 8

See textIi ILL.

C a' SOp1I See text k /7777'

I Twisted pairi

Itransmissionline transtonner121 on 28 002 31Neosid core

VsPoint A

1N914

Fig. 2. QRP output stage (SW) of Project Omega. The basic responseis 1 to 120MHz but see text.

820

Tritilar transmission linetransformer.

I 10n

0 0 0

2 x1N914

a.100n100n T't I11°125

/47

+12V

i560 2k2

47/25100n 1k

/1771

Output

+12V

And some success

One reason that makes me presson with the system outlined above isthe unquestionable success that Ihave had with straightforward singleended and push-pull MOSFET out-put stages. They are great. They arealmost indestructible - SWR pro-tection is completely unnecessary -and they possess excellent linearitywith almost total frequency gainflatness. The Project Omega QRPoutput stage is shown in Fig. 2. To il-lustrate a point, the basic circuitwith its transmission linetransformers exhibits a 3dB point at120MHz. Voltage gain from the in-put of Q2 to the output, is flat to allintents and purposes from 1MHz to100MHz at + 26dB. Saturated out-put power is around 6W with a 12Vsupply.

The intended application calledfor a total voltage gain of around501B or perhaps slightly less. At thesame time, a voltage controlled gainelement was required for ALC anddrive control purposes. The dualgate MOSFET Q1 was added to pro-vide this. Although the broadbandstage gain is around 23dB on thelower HF bands there is some rolloffon 15 and 10 metres. This is due, inthe main, to the self capacitance ofthe 3SK45 device. Rather than add afurther transistor to the strip, I

decided to sacrifice the gain flatnessof the power MOSFET parts by put-

ting in a peaking network betweenthe driver and output stage. Thisputs a bump in the gain towards30MHz. The 'C' part of the peakingnetwork is made up of the capacitybetween the drain tab on Q2, the in-sulating washer and the heatsink. Ishould have said before. The stand-ing current of Q2 is in the region of200mA (Q3, Q4 total 100mA) to thatthings would get too hot without aheatsink used for these devices.

The design of the PA strip willbe covered in greater detail withinour Project Omega series, probablyin the October issue of themagazine.

23cm superregenerator

Once again, this project falls in-to the category of "in need of furtherdevelopment" but is interesting allthe same. What I have in mind isthis: a cross town chat box using23cm operating frequency, aroundsix transistors (cheap ones) an audioIC and not much else.

The people who are used to buy-ing their Japanese technology offthe shelf of their local 'emporium'will probably pour buckets of scornof the idea of an AM (yes, amplitudemodulated) superregenerative (SR)transceiver for the band. I say, stuffthem. It's great fun makingsomething simple once in a whileand it should be a quick way of fill-ing the 23cm amateur band with

signals before the Ministry ofDefence takes it over for good.

This type of circuit has got itselfa very bad name beacuse a) it tendsto radiate and b) has a selectivityabout as wide as a barn door. Whatmay not be appreciated is that thebasic circuit is highly sensitive andalso enjoys a commendable level ofautomatic gain control. What I pro-pose is the construction of aGigahertz SR set brought bang upto date with modern components.My aim in writing this is to prodsomeone else into a few experimentsso that I have got another station towork, preferably in the HaywardsHeath, West Sussex area! First, Iwill refresh a few memories abouthow SR detectors work.

The principle

The basics of an SR system isshown in Fig. 3. A high Q, low losstuned circuit is closely coupled tothe input of a low noise amplifier.Part of the output of the amplifier iscoupled back to the input tuned cir-cuit, the tank, in phase. The amountof coupling, in phase with the input,is adjusted to maintain the circuit inoscillation but no more. A third win-ding, this time closely coupled is us-ed to inject signal energy into thetank circuit.

There are two remainingelements to an SR system. The first isa low frequency ( 1MHz) quenching

HAM RADIO TODAY AUGUST 1983 35

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Fig. 3. The basics of a superregenerative DC supplyreceiver system

Electronic switch

RF input

AF output

oscillator and the second is a meansof detecting the presence of RFoscillations in the system. In prac-tice, the quenching may be done bya secondary oscillatory loopswitching on and off the first one.Similarly an RF oscillatory state maybe detected by the non -linearity ofthe oscillator transistor itself, ielooking for a change in collectorcurrent with oscillation.

This is how it works. The RFoscillator/amplifier is switchedregularly on and off by a low fre-quency source. At the moment im-mediately after switch -on there is noRF voltage present in L I save therandom voltages associated withthermal noise. This noise will beamplified by Al and the outputtransferred, in part, back to LI.Because L I is a selective tuned cir-cuit, only random noise voltagesvery close to resonance will findtheir way back to the input of A 1which are subsequently re -amplified and so on. Eventually,after a comparatively long build-upperiod, sustained oscillation willresult.

The time taken to reach sustain-ed oscillation is dependent on theloop gain (which should be as low aspossible but compatible withachieving oscillation) and the Q ofthe tank circuit. If an RF signal atthe resonant frequncy of the tank iscoupled in, then the build-up ofoscillation will occur much fasterthan when the cycle is initiatedpurely by thermal or device noise.The cycle is illustrated by the tracesof Fig. 4. The RF envelope, controll-ed by the switching of the quenchcircuit, gets bigger quicker when an

on frequency signal is present.The sensitivity of even a simple

circuit can be very high indeed. Tosome extent, it is dependent on thequench frequency which should beas high as possible, although theperiod should be of sufficient dura-tion to allow the RF oscillations todamp down to below thermal noisein the quenched state. Thus, themaximum useable quench frequen-cy depends on the Q of the tank cir-cuit.

In practice, it is better to build aseparate quench oscillator circuitwhich then provides direct swit-ching for the RF oscillator circuit.There is another point. Therecovered AF output from super -regenerative detectors is quite low,typically in the region of a couple ofmillivolts. This will be superimposed

on a quench waveform of more than500mV with a typical circuit. TheAF amplifier should be capable offiltering out the quench signal,otherwise it might block.

Fig. 5 shows the receiver systemtestbed with which I have been ex-perimenting. Obviously thisrepresents purely the receiver corebut it has to be right before pro-ceeding further. To date, I have gotthe thing running efficiently toaround 700MHz in the SR mode.The quench oscillator, Q I, providesa quench signal in the region of1MHz. It seems a bit reluctant toprovide SR detection at 1300MHzalthough it will oscillate up toaround 3GHz on carrier wave only.I will keep you posted on my work.To anyone with an interest in this,please keep me posted on yours.

Trace 1

Trace 3a

Trace 2b

Trace 3b

Rise and tall times due to 0 pot oscillatory circuit

Fig. 4. Typical super regenerative wave forms.

Averagelevel

TTAverageoq level

Quenching orswitchingwaveform.

Super regenerat ivetraces with nosignal present

Superregenerativetraces modifiedby presence ofsignal

36 HAM RADIO TODAY AUGUST 1983

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V 1-

Q1

4k7=100n

6k8

2k2

2SK55

47p47k 470p

1k .470p180

b. pH

Fig. 5. 23cm Super regenerative test circuit.

5cm of 2-5 sq in.WRFC `copper wire

0.5 to 5p

BFT95

0.5 to 5p

To oscilloscope

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We are now supplying crystals to most commercial and MIL specifications the range 1MHz to60MHz, ordered in small quantities, within 2; weeks AT NO EXTRA CHARGE. We also have aneven faster EXPRESS SERVICE for that very urgent order. We can also supply crystals forcommercial applications e.g. Microprocessor, TV etc at very competitive prices. Let us know yourneeds and we will send a quote by return, alternatively telephone or telex our Sales EngineerMr Norcliffe who is normally available in the office for technical enquiries between 4.30 and6.30 p.m.

DOUBLE BALANCED MIXERWe are now stocking two new double balanced mixers which are pin compatible with both theMD108 we used to stock and also the SBL 1. but have much superior specifications covering500kHz, to 500MHz. The M8 is hermetically sealed @ E7.83The M18 is non -hermetically sealed @ E6.09

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Please help me to get your favouriteRadio Amateur Magazine out on time bysubmitting your advertisement copy onthe dates shown below.

Remember setting is FREE if you meetthe setting dates.

Issues

September '83October '83November '83December '83January '84February '84

Setting Dates

July 5thJuly 29thAugust 26thSeptember 30thOctober 28thNovember 25th

CompleteArtwork

July 15thAugust 8thSeptember 5thOctober 10thNovember 7thDecember 5th

Phone me Lynn Collison

01 437 1002to discuss your copy details.

HAM RADIO TODAY AUGUST 1983 37

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11

38 HAM RADIO TODAY AUGUST 1983

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HAM RADIO TODAY AUGUST 1983 39

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PracticalitiesAn occasional series.

By Ian Poole G3YWXVery often in the field of amateur radio a few practical hints and tips can save a great deal of time wasted

in finding out why a particular circuit does not work or in experimenting in finding out the best way oftackling a problem. It is hoped that it will be possible here to pass on a few practical ideas to cut down this

time spent on wild goose chases and also to improve the overall results and appearance of the finishedprojects.

ATU coilsOne piece of equipment which almost any amateurstation will possess is an ATU to match the aerialsystem to the transmitter, reducing SWRs andincreasing the power transfer. SWRs below 2:1 caneasily be tolerated as the output stages will normallywithstand this sort of mismatch and it onlyrepresents a power loss of 0.5dB. However, as theSWR increases damage to the PA transistorsbecomes more likely if no protection is provided, or ifvalves are used excessive dissipation within the valvewill cause reduced life. In addition to the possibilityof PA damage, as the SWR increases so theefficiency falls, making some form of matching unitessential for most aerial systems. The availability ofthe parts for ATUs is becoming increasingly poor.While little can be done about such components asthe switch and the variable capacitor, it is possible tomake a very acceptable coil former which cannotonly operate well but can also look very professional.The actual former is constructed from a length of oneand a half inch plastic waste pipe about six incheslong which cna be obtained from almost any

100p

Widespaced

V

Fig. 1. Circuit diagramof A.T.U.

".'

plumber's or DIY shop. Next a helical groove about1 /10th of an inch deep should be cut with a pitch ofapproximately ten turns per inch to take the wirewhich should be 18 swg or thicker. This can be doneeither on a lathe if there is access to one or a friendlylathe operator, or by carefully using a file. For the coilto be incorporated in a circuit such as that shown inFig. 1 about 40 turns should be sufficient. Two holescan be made in either end to terminate the wire asshown in Fig. 2. Taps should be placed at intervals of

Fig. 2. Method of anchoring wire at eitherend of coil.

one turn for the first few turns and then slowlyincreased. The actual positions of the taps can bealtered if there are not sufficient positions on theswitch after the unit has been tested in order toobtain the best SWR.

A simple check for transistors

Most of us will have been in the situation of requiringa simple and quick check for a transistor. While thereare several transistor checkers on the market theywill tell us far more than we normally need to know,besides which they cost money! Several years ago Ilearnt a very simple check for the basic functioning ofa transistor which despite its simplicity has not yetlet me down. If one looks at the basic construction ofa transistor as shown in Fig. 3 it can be seen thatthere are two PN junctions which can be representedas shown in Fig. 4 for the purpose of this test. Whilethe example shows an NPN transistor the same willhold for a PNP device except that the polarities willbe reversed. It is now an easy matter to check the

40 HAM RADIO TODAY AUGUST 1983

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base -collector and base -emitter junctions with anordinary test meter on the ohms range. Each junctionshould be checked in both forward and reversedirections. The readings which should be obtainedwill vary dependent on the type of meter used andthe type of transistor. Normally one should expect tosee a reverse resistance of greater than 10M for asilicon device and about 1M for a germanium device.If the device is a power device then these values willbe less. In the forward direction one would normallyexpect to see a resistance of about 1K on a lowohms range on the meter but this is very dependenton the meter itself. Provided there is a largedifference between the forward and reversedirections then the junctions should be intact. Finallya check should be made between the collector andemitter to ensure that the base region has not been'burnt' through. The reading obtained in bothdirections should be of the same order as the valueobtained when measuring each junction in the reversedirection.

Fig. 3. Constructionof a transistor.

Collector

Base

VFig. 4. Diagramaticrepresentation of atransistor as measuredby a test meter.

Emitter

Front panel labelling

One of the problems of building one's own equipmentis that whilst it is possible to construct an excellentpiece of equipment from the electronics point of view

it will very often lack the professional finish becauseof the lack of mechanical facilities. One way in whichthis can be improved is by improving the front panellabelling. This can easily be accomplished by usingLetraset. The main draw -back with this is that it rubsoff fairly easily but this can be easily overcome bycovering the whole of the front panel with clearfablon to give a hard wearing and professionallooking finish.

Boards for prototyping

So many prototypes end up in dreadful messes, andprobably not working, or at least not as well as theymight because of this. I am a great believer in thefact that if you can see what you are doing then thechance of making a mistake is much less. Havingtried many methods, from stick -on -tracks on a PCB tothe proverbial rat's nest where a 'ball' of componentsgrows, the best one which I have yet found is plain0.1 inch matrix or veroboard and the correspondingpins. Using this one is not constrained by the tracksof the tracked versions, and it is possible to lay outthe components out in a manner which resembles thecircuit diagram, which I find reduces the number oferrors made and makes the job of tracing the circuitthrough later that much easier. In addition to this I

mount all the resistors, capacitors and other similarcomponents on pins which makes their replacementeasier and keeps all the intercomponent wiring to thereverse side of the board. Using this method ofconstruction it is possible to make a very neat,compact and reliable prototype.

Preventing moisture entering coax

Several years ago a friend of mine erected a superb40 metre dipole. No expense was spared - harddrawn copper wire was used together with glassinsulators at either end, a porcelain dipole centre, andthe coax was the semi -air spaced type with the airspace holes running the full length of the coax. Allwent well, DX was contacted on both 7MHz and21MHz until one day when it rained. The waterdroplets clung to the wire and ran down to thelowest point on the wire which was at the centrewhere the coax was connected, and entered the airspaces in the coax. It then proceeded to flow all theway down to the shack where it formed a pool onthe floor. The moral of the story is that one shouldalways seal the remote end of a length of coax if it isgoing to be exposed to any form of weather. Inpractice there are two ways of preventing moistureentering the feeder. The first is to seal the end withsome form of flexible sealant; I personally have foundthat something like Evostick applied generously roundthe whole of the exposed end of the cable worksvery well. It is worth emphasising that not onlyshould the dielectric spacing the two conductors beprotected but also where the outer insulation is cutback as water entering here also will work its wayback slowly. The precaution which should be taken isto run the cable as shown in Fig. 5in order to preventany water which does manage to enter the cablefrom passing down it any further. It is veryworthwhile taking precautions against letting

HAM RADIO TODAY AUGUST 1983 41

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Fig. 1. When connectingcoax to an externalaerial be sure to use asealant to avoidmoisture getting intothe cable. Additionally puta loop of wire in thefeeder at the aerial endto make it harder forwater to run downthe coax inner.

Aerial

Mast

Sealant

Feeder

Aerial element

Seal cut

Feeder

Aerial boom

Mast

moisture enter the feeder as comparatively smallamounts accumulating over the years will slowly butsteadily build up the losses to a point where the cablebecomes unuseable and has to be replaced which canbecome very expensive if some of the low loss typesof feeder are used. If these precautions are observedthen not only should events like those that I have justrecounted be avoided but also the life of the feedershould be extended.

Soldering TV connectors

Have you ever been caught soldering those TV stylecoax sockets and found that having made a good

soldered joint the plug would not fit because theplastic holding the centre pin had melted and the pinbecome displaced. It is not always easy to make agood joint by quickly dabbing the soldering iron ontothe wires to be soldered and therefore any way roundthe problem help. The problem can be overcome to alarge extent by connecting a plug into the socket.This has a twofold effect, firstly to increase thethermal capacity of the whole unit, and secondly tokeep the centre pin in place if the plastic does melt.One does have to be a little careful not to melt theplastic in both connectors. This does solve theproblem in most situations, or at least this is what Ihave found.

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42 HAM RADIO TODAY AUGUST 1983

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EINCOMERMORUM By Tony Bailey G3WPO

While not wishing to join the Class Avelsus Class B status controversy, Ireceived some interesting corres-pondence from Ian Abel G3ZHI,concerning his quest for theintroduction of a Novice Licence.Now, while not wishing to decry theseefforts, I would seriously question theneed for such a licence. Comparedwith t4ie RAE in its original form, theexisti g multiple choice papers arenot 'at all difficult to pass for anyonewith a medium to serious interest inthe hobby. You are not required topass any form of practical exam(which is a shame judging by some ofthe stations one hears), or take themorse test, so acquiring a Class Blicence is not particularly difficult.The fact that you then require themorse test to get on HF is somethingwe are stuck with I am afraid.

The Home Office does not seem tothink there is enough interest in aNovice Licence, reading the backcorrespondence, although the thenPost Postmaster General did, in 1968,promise to introduce a form of NoviceLicence very shortly. Taking intoaccount the current RSGB nego-tiations with the Home Officeregarding Class B licencees usingMorse code on one or all of theVHF/UHF bands (as a means of self -training) I personally can't see a lot ofbenefit in a Novice Licence.

The HF bands are alreadyextremely crowded and the positionwill not improve, so the addition offurther stations engaged in very basicsell -training will not help matters. Iknow we all have to start somewhere,but the overcrowded HF bands maybedeserve some consideration. At therisk of being labelled a spoil -sport etc.my own opinion is that in the interestsof sanity, for HF, the existing Class Arequirements should be the NoviceLicence exam, and that a much stiffertheoretical, together with a practicalexam of some sort should be intro-duced for the Full licence. Or in otherwords, a form of incentive licencing.

If a Novice Licence is introducedbecause of demand, then it should befor one or two bands only (say 80 and20 metres), limited to a small segmentof frequency bandwidth, and at apower not exceeding 25 watts input.

Whether or not the morse test isstill needed is another subject. As Ihave said before passing the morsetest does not demonstrate an inherentability to use the HF bands correctly.

The Class B licence is a separatesubject - everyone, when arguingabout the limits placed on Class Bsforgets that the whole purpose ofintroducing this licence in the firstplace was to encourage the use of, andexperimentation on, the VHF/UHFbands for those interested in thesefrequencies.

I agree that CW should be usablein some form under the Class BLicence, but please don't confuse theB licence with the A licence - theyare intended for totally separateapplications. If people rememberedthis then the arguments over the'lower status' of the Bs would neverhave started - this argument is basedon a totally erroneous interpretationof the purpose of the two Licences.Many G8/6s I know are far moretechnically competent than a lot ofG3s I have come across (includingmyself).

If you do want to support a NoviceLicence, then write to Ian at 52Hollytree Avenue, Maltby, SouthYorks. If you have any strong views onthe subject then write to me c/o HRT.

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CURRY ONHAMMING:

Amateur Radioin India By Thomas E King

VK2ATJ

In this small town in north westernIndia such an occurrence was a majormedia event and reporters came indroves. A spy story would have madeterrific headlines, but no storyappeared at all, as the man was ableto document that he was an amateurradio operator licensed by theWireless Planning and CoordinationWing of the Ministry of Communica-tions. Neither the police nor any ofthe reporters had previously heardabout amateur radio.

Today there is a training coursefor would-be amateurs in the Punjab!

This incident is not an isolatedevent as nearly all Indian govern-ment officials outside the WPC areunaware of amateur radio, or thattheir own government allows privatelicensing of radio equipment. Anormal response to a question posedabout amateur radio in India (and inmost other developing or third worldcountries) is "that sort of activity isn'tallowed in this country". Governmentofficials often look upon the privateuse of a transmitter in a developingcountry as an anti -social activity.

Fortunately, the Prime Ministerof India, Mrs. Indira Gandhi, is one ofthe better informed public officialson amateur radio as there are twoamateurs in her family. Her son Rajivis an amateur, VU2RG as is hisItalian -born wife, Sonia, VU2SON.

While the growth of amateurradio in India hasn't beenspectacular there are far moreamateurs in this country than in all ofits neighbours combined. The total

In June of 1980, anIndian working in Iranfled a rapidly changingcountry. He made hisway through Pakistan

and to his home inJulandar Punjab, wherehe set up his amateur

radio equipmentcomplete with aerial. Itwasn't long before the

police came to thehouse, and despite

providing evidence thathe was a licensed radio

amateur, the youngman was arrested as aspy and taken to gaol.

amateur population in Burma,Bangladesh, Bhutan, the Maldives,Nepal, Pakistan and Sri Lankanumbers well under 100.

January 1, 1923 is regarded asthe starting point for amateur radio inIndia. At that time there were 20British licence holders in the formercolony. The first licence issued to anIndian was in 1925 when LokendraBos VU2AG, was recommended foran experimenter's permit by Sir J.C.Bose, a Nobel Laureate. (It is said thatMarconi himself was enthusiastic

about this nomination). With thatlicence VU2AG became the first hamin Calcutta and the first OM in anIndian amateur world which is almostexclusively male. It's almostexclusively male - but not quite -because there are over 100 YLs inIndia, nearly a fifth of them are inNew Delhi, the country's capital offour million.

Delhi has a total amateurpopulation of about 80 hams of whichsome 30 are foreigners holdingreciprocal licenses, while Bombay'sham comminuty numbers about 100.Madras also has about 100 hams andIndia's largest city of Calcutta hasonly 20 hams for a metropolitanpopulation well over seven millionpeople. Bangalore, a pleasantindustrial city in the south and homeof many electronics companies, hasabout 150 amateurs and a veryprogressive radio club offeringtechnical assistance and trainingclasses.

Clubs

Many Indian amateurs areinvolved in clubs. They receive theirmorse and theory training thrughclubs and after passing the licenceexam often continue their clubinvolvement because of technicaland social benefits.

Members of the Delhi RadioClub, for example, can use the homebrew equipment licensed asVU2ARS. Sundays at the club havebecome a social session, as well, and

HAM RADIO TODAY AUGUST 1983 45

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members are welcome to drop in foran eyeball QSO and the exchange ofQSLs. It's also an ideal exchangetime as work continues on an allIndian-HF amateur kit, plus a locallydesigned VHF project. And RajivGandhi is no stranger to the Sundaygatherings.

Due to the assistance providedby the Delhi Radio Club a tract ofland near the Delhi Flying Club hasbeen donated by the Government ofIndia for a new Shack site. InHyderabad, capital of the cyclone -prone State of Andhra Pradesh, thelocal club had received land from theState Government. These are twopositive gestures from governmentswhich are slowly learning aboutamateur radio.

The electronic hobby is over 60years old in India. Yet is still has notbeen given the official recognition itdeserves nor has it flourished as itshould. As there is nothingspecifically written in the IndianCharter about amateur radio, it isneither encouraged nor discouraged.Admittedly, in a developing countrywhich is large enough to be called asubcontinent, there are manypriorities other than the development

Because of its size andexpanding population India is facedwith a number of critical problems:unemployment (and under-employment), clean drinking water,adult literacy, elementaryeducation, health care, rural roads,housing and electrification andnutrition for the undernourished.Many of these problems will remainalthough progress has and is beingmade to raise the cold statistics weoften see as front page headlines:average per capita income ofUS$200 per year, a 35 per centliteracy rate, male life expectancy of42 years and a natural increase ofnearly 2 per cent which means that15 million people, or the equivalentpopulation of Australia, is born everyyear.

The development of amateurradio in India is not a cure-all for, oreven a partial solution to, any of thecountry's chronic problems, exceptperhaps unemployment. However, abetter public and governmentunderstanding of how a group ofdevoted and enthusiastic,technically -minded individuals cancontribute to the nation is definitelyneeded. Most obvious, of course, ispublic service.

The vast majority of amateur radio stations in India use convertedmilitary receivers and homebuilt transmitters such as this setup inKodaikanal

Emergency links

Indian amateurs havedemonstrated the tangible benefits ofamateur radio to the country withvaluable public service activities onmore than one occasion. In thesouthern State of Andhra Pradeshhams provided vital communicationlinks when a storm wrecked all othercommunication facilities. During aPost and Telegraph strike in 1960,amateurs passed importantmessages for the Government andduring the 1965 Indo-Pakistan Warhams monitored ememyparatroopers.

But the most outstandingexample of amateur radio being usedfor the public good was in September1979 during the Morvi floods inGujarat State. On this occasion hamsof western India including JimmyVU21J, Vasant VU2RX, ChrisVU2KIT, Jai VU2ED, Jayu VU2JAU,Pradeep VU2PCD and JayantVU2JNT activated emergencystations to provide communications

Leela, VU2CP is one of the mostactive XYLs in India but operatingtime from the Madras QTH isshared with her husband, PanVU2FC

for the Home Guards, relief agencies,government officials and victims of

46 HAM RADIO TODAY AUGUST 1983

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the disaster. For nearly three weeksvolunteer field teams camped undermakeshift arrangements andoperated communicatons equipmenton a near round-the-clock scheduleusing only battery power. Morvi waslinked with the cities of Rajkot,Ahmedabad, Baroda and Bombay asmobile units accompanied the HomeGuards into the worst affect areas.Amateur radio in India came of agebecause of a major disaster. AfterMorvi there was no longer a need toconvince anyone that a specialisedtechnical hobby was a national assetlike the Red Cross or the HomeGuards.

A more recent demonstration ofthe benefits of amateur radio came inlate 1980 when volunteers set up acommunication network across6000km of rugged countryside innorthern India. The situation was notan emergency but the internationallypublicised Himalayan Car Rallyonce again proved the usefulness of

amateur radio in providing front linecommunication. The Himalayanrally is now an annual event and itprovides a much needed coordinatedrehearsal for dealing with acuteemergency communication needs inthe immense country.

With such press publicity andseemingly increased publicknowledge about amateur radioactivities and benefits, it would seemthat a ham ticket would at least berelatively easy to obtain in India.Such is not the case as adverseamateur legislation hasdemonstrated.

Red tape

The Amateur Service Rules1978, brought into effect on January1, 1979, have tended to restrict thegrowth of amateur activities ratherthan encourage them. Besides beingpoorly drafted, the rules have madethe obtaining of a licence moredifficult by making licensingprocedures cumbersome andexaminations more strict.(Apparently amateurs were notconsulted in any of the newlegislation).

The rules incorporate four gradesof license: advanced amateur, Grade1, Grade 2 and SWL Licence.

Allocations are 3500-3540 and3890- 3900k H z , 7000- 7100k H z ,

14000- 14350kHz , 21000-21450kHz28000-29700kHz and 144-146MHz.

The 10, 18 and 24MHz bands are notyet alloted in India.

Advanced licence

To obtain this licence acandidate is required to pass a severewritten test with 60 per cent or bettermarks and to have a morse speed of12 wpm. Additionally, the rules alsostate that in order to obtain thislicence an amateur must have eitherpossessed a Grade 1 licence for twoyears or a Grade 2 licence for threeyears.

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h I 'OUR lift

Commercially built amateurradio equipment is now availableto Indian operators under aspecial 'Open General Licence',although only about 10 per cent ofthe hams in India can afford suchluxuries.

Grade 1 licence

A Grade 1 licensee must pass atheory test with a 50 per cent orbetter score and have a morse speedof 12 wpm. The operator cannotoperate the satellites or use SSTV(except on the 2 metre band). Poweris limited to 150 watts input exceptfor the 2 metre band where the limit is10 watts.

Grade 2 licence

The 1979 rules affect thesenovice -like licence holders the most.Currently they are only allowedmorse operation on 80 and 40 metreswith a maximum input of 25 watts.Former telephony privileges on those

two bands have been revoked.However, the licensee can operatetelephony on the 2 metre band, with arestricted Grade 2 voice onlylicence, even if the five wpm morsetest is failed. Power allowed on the 2metre band is five watts but at leastthis regulation may create interest inVHF operation. (Some clubs havedesigned VHF kits.)

The only positive change madein the 1979 rules is that a Grade 2licence has been made permanent.Formally the Grade 2 licence holderhad to either pass the Grade 1 testafter three years or surrender thelicence.

SWL licence

This seemingly unenforcablelicence must be obtained in order topossess a communications receiver.After obtaining the Short WaveListeners' Amateur Licence theholder is permitted to listen to allbands allocated to the amateurservice.

Mobile Licence

In the past, mobile endorsementwas unrestricted. This importantfacet of amateur radio activity hasnow been highly restricted with theintroduction of mobile endorsementsvalid for only three months and issuedonly after paying an extra fee. Asendorsements are only for specificexperiments, and reports of theexperiments conducted are required,it appears that licensing authoritieshave forgotten that natural disastersand the the need for emergencymobile communications do not waitfor paper -pushing bureaucrats!

While the bureaucrats pushexcess paper, intending amateursfind there is a scarcity ofindigenously printed study material.The Federation of Amateur RadioSocieties of India (FARSI) hasproduced a publication Guide toAmateur Radio in India while aGovernment booklet InternationalRegulations and Indian AmateurRadio Service Rules is intended toguide candidates past some uniquely -Indian rules and regulations. Thesetwo publications are used in radioclasses and additionally manyinstructors make use of the ARRLpublications: Radio Amateur'sHandbook and UnderstandingAmateur Radio. RSGB publicationsare not well known in India.

HAM RADIO TODAY AUGUST 1983 47

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Theory and morse classes aremajor activities of many of the largerclubs in the country. But Indian clubscannot take any particular credit foreither publicising their own activitiesor informing the general public aboutupcoming radio classes. Indian radioclubs are just as bad as Western clubsabout publicity but somehowpotential amateurs find out aboutclasses anyway.

Many Indian clubs have found itconvenient to organise a crash 20 to30 day course for teaching radiotheory to an ideal class size of 20 to30 students. Students being trainedin a group can opt to be examined asa group if there are more than 20candidates. When exam time comes,one of the 19 regional wirelessmonitoring stations will send itsexamination officers to conduct theexam at a place convenient to thegroup - probably its college, schoolof meeting place. Officers travel tothe place of examination at theGovernment's expense; the travelcosts are not recovered from thecandidates.

The theory portion of the exam ismade up with questions from radiotheory, international and Indianregulations and operatingprocedures. The theory exam has aduration of one hour and the paper isdivided into two parts: one deals withtheory and the other coversregulations and procedures. A passmark must be obtained in eachsection.

The exam paper is often commonfor Grades 1 and 2 but Grade 2candidates are required to answeronly half of the questions while Grade1 candidates have to answer twothirds of the questions. TheAdvanced Grade paper has aduration of three hours with questionsof a significantly higher technicallevel. Candidates holding a degreein telecommunications can beexempted from section A for theAdvanced or any grade of license.(Oddly enough the exams are notstandarised as the Bombay exam isdifferent from the one used in Madrasetc.)

Apart from group exams amateurexaminations are held once a monthin Delhi, Bombay, Calcutta andMadras. Some other regionalwireless monitoring centres holdexams four to six times a year. Cost isRs40 for Advanced and Grade 1 andRs25 for Grade 2. Unless renewedevery two years the licence lapses

automatically.These rules and regulations are

straightforward enough but the needfor a simplified approach to amateurradio regulation in India, in general,is reflected in some of the rules.(1) At the time of renewal, an

amateur must show proof of 100contacts in the previous twoyears.

(2) The minimum age for applyingfor an amateur licence is 18 yearswhich is sometimes relaxed to 16years for Grade 1, and 14 yearsfor Grade 2 licences.

(3) Log books must be kept forinspection although somecountries have abolished thisregulation.

(4) Log book times must be kept inIST (Indian Standard Time)although the rest of the worlduses GMT.

(5) It is also required that a summaryof experiments conducted berecorded in an amateur's logbooks.

(6) A register of equipment has to bemaintained in India.

(7) It is no longer possible to have asecond station at a differentlocation; a change of address hasto be applied for instead.

(8) India has reciprocal licensingarrangements with severalcountries but foreigners arerequired to stay for a year in Indiabefore they can obtain a licence.(This is in violation of internat-ional reciprocal agreements!)

(9) Although emergencycommunications are nowpermitted, messages can only beofficially sent to and from districtmagistrates, deputy commission-ers of collectors. (Had thisregulation been followed to theletter during the Morvi disasterthere would have been no lifelinecommunication links betweenthe Home Guards, reliefagencies, refugees, police andgovernment officials.)

(10)Club stations cannot be operatedby members unless authorised inwriting by the centralGovernment.Even if all rules and regulations

are followed it can take up to a yearbetween taking the exam and the daywhen the ticket arrives. And even ifthe relevant code and theory exam ispassed an applicant may still fail thesecurity clearance. If there is anyevidence that the use of amateurradio may be used for anti -state

activities, no licence will ever begranted nor will any reason be givenby the licensing authorities.

Getting on the air

Assuming that all rules andregulations and exams andclearances are passed the obstaclesto actually getting on the air are notover! Obtaining suitable equipmenthas always been a block to thedevelopment of amateur radio inIndia.

AMATEUR RAOT:Theme

he Fast Developing Tech,

Tradition even plays a role inham conventions. A South Indianclassical dance opened the FifthAll India Amateur RadioConvention in Bombay.

Before World War 2 almost allequipment was homemade asnothing was either manufactured inthe country or allowed to beimported. After the war was overlarge quantities of surplus equipmentflooded the market. This period,lasting some 10 to 15 years, saw theclosest thing to 'off the shelf'equipment. It meant hams were ableto pick up gear at moderate pricesand convert or modify it to theirneeds.

The post war days were the daysof BC348s, 779s, AR88s and HROs.But equipment from then, whilevirtually gone from the disposalmarkets, hasn't disappeared entirelybecause such vintage machines stillform the receiving link in the averageham shack in India. Few amateurs inthe country have mastered receiver

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building so former military machinesare the only answer. However, thereare a few successful homebrewtransceivers on air and five homebuilt Oscar stations, so the problem isnot technical know-how butobtaining the latest components atmoderate cost. Particularly difficultto obtain are variable capacitors forVFOs, toroids, transmittingcapacitors, power transistors, crystalfilters and slow motion drives.

The scarcity of gear isheightened by the fact that what littlesurplus equipment does come on themarket from military disposals isgrabbed by scrap dealers. Thus,much needed equipment neverreaches an amateur who might use itto interest another person or even tosome day save a life.

Homebrew and military surplusequipment constitutes about 90 to 95per cent of all amateur stations in thecountry. The remaining 5 to 10 percent are commercially equippedstations with gear ranging fromHeathkit, Swan and Drake toHallicrafters, SBE and Hammerlund.There are even a few atypicalstations such as the Collins equippedshack of VU2BBJ, one of the mostactive hams in South India.

The commercial gear in mostshacks was either brought in byreciprocally licensed amateurs andlater sold or donated, brought in byIndian amateurs coming back homefrom overseas visits, or directlyimported, a practice which at onetime entailed major import licenceand customs duty problems.

The difficulties of importing havebeen dramatically eased sinceAugust 1980. As a result ofprolonged efforts the import policynow allows a licensed amateur toimport Rs10,000 worth of equipmentper year under the Open GeneralLicence. All radio equipment iscovered, as are kits, accessories,SWR bridges, antennas, rotators,feedlines, spares and components.Indian amateurs no longer need acomplicated import licence but theyare liable for 63 per cent duty!

Only a very few amateurs havebeen able to purchase the latestequipment from Kenwood, Yaesu,Ten Tec, Icom plus the odd SSTV unitor two. Getting equipment is still themain problem for the vast majority ofIndian amateurs and SWLs. Whilethey have the time and zeal (twoelements stressed in radio trainingclasses along with morse and theory)

to be involved in amateur radio, thelatest in solid state equipment isdefinitely too expensive.

Large sums of money for gear areimpossible, but this does not mean acomplete lack of money, asindividuals interested in getting intoamateur radio in India are generallybetter educated and on a muchhigher (but still low by Westernstandards) income level.Consequently most amateurs orwould-be amateurs have a bit ofmoney available to spend on thehobby. But this often doesn't helpbecause there simply isn't enoughgood used gear available and evenold commerical valve gear is highlydesired.

Used equipment

European amateurs may havegood used equipment which theymight like to make available to fellowhams in India at reasonable prices.The Federation of Amateur RadioSocities of India has agreed to act asa clearing house for equipmentdestined for this recycling. Amateursshould send a description andcondition report of gear for sale plusthe price and freight charges to: SaadAli VU2ST, Former President,Federation of Amateur Socities ofIndia, 4, Kurla Industrial Estate,Chatkopar, LBS Marg, Bombay,

India. 400086.FARSI has been an active voice

in the development of amateur radioin India. Since its formation nearly 15years ago it has continuouslynegotiated with Governmentauthorities for better conditions.

Government liaison is only one ofFARSI's roles as the organisation isalso involved in promoting localclubs (of which 50 are affiliated to theFederation), arranging radio classesand technical talks, designing andmaking suitable equipmentavailable including an Indiandesigned three -band transceiver kit(still in the design stage) andpublishing the monthly magazineRadio.

A major activity of FARSI isorganising the All India AmateurRadio Convention every two or threeyears. The last convention, the 5th,was held in Bombay, India's leadingport and most 'Westernised'metropolis. For three days delegatesfrom many parts of India assembledat the Nehru Science Centre to heardiscussions ranging fromCommunication Satellites andEconomical Transceiver Design toAmateur Radio in the Public Servicesand Amateur Radio, KeepingAbreast with the Latest Technology.They also come to see homebrew andcommercial displays; and to meetwith other hams.

Toroids, power transistors, crystal filters, slow motion drives andVFO-type variable capacitors are difficult to come by but VU2CCshowed what can be built at a homebrew corner at the All IndiaAmateur Radio Convention.

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Amateurs from around the worldwould have felt at home at the wellattended and organised conventioneven though there were severalpecularities which made the eventdistinctly Indian. Before theinaugural address by the then FARSIPresident, Saad Ali, there was aninvocation dance in typical SouthIndian style. While the delicatearoma of curry from the nearbykitchen filled the air a beautiful sari -clad lady performed a classicaldance routine.

The graceful movements whichoriginated countless centuries agogreatly contrasted with an adjoiningdisplay of the latest 20th centurysolid state VHF and HF transceivers.The display of Yaesu, Icom andKenwood gear was the first time thatcommercial equipment had everbeen on exhibition in India.Consequently the gear -laden standof solid state equipment drew largecrowds of 'prospective' purchasers.

There were other displays whereprospective purchasers wereactually making purchases, the mostnotable being the FARSI publicationstand which sold ARRL books, FARSIpublications and issues of Radio.

Displays of related electronicequipment also drew interest. TheJetking kit company sold a range ofhome electronic products rangingfrom a MW transistor radio kit forRs105 to a top of the line speaker kitfor Rs1200. The company also had aTV kit on display priced fromRs2500. (Bombay, along with sevenother cities in the country, has asingle channel of black and white TVtransmission.)

Homebrew equipment

The delegates eagerly visited thecommercial stands but were alsointerested in the display of homebrewequipment. Foremost in thehomebrew department was a lineupof 2 metre equipment built byVU2ASH, Ashok from Gwalior. Thisdedicated electronics engineerworks until 8pm, then comes home tospend another five or six hoursdeveloping VHF equipment. So farhe has prototypes of a 50mW FMtransmitter with VFO, an FMreceiver, an AM receiver and a 1 wattFM transmitter. The GwaliorAmateur Club has benefited from his

efforts and a few amateurs in thisNorth Indian city can be heard on145.50 FM homebrew simplex. In1982 VHF activity throughout Indiaexperienced a major boost whenYaesu supplied equipment atconcessional prices.

The homebrew and commercialdisplays and various technical talkscontributed to the Bombayconvention's theme of The Contribu-tion of Radio Amateurs to the FastDeveloping Technology of Com-munications. What's more it showedthat amateur radio in India is slowlybecoming recognised for its merits.Reasonable achievements have beenmade over the past few years butthere is more which can be done. Inhis concluding address former FARSIPresident Ali set down five goals thatthe amateur movement should striveto meet in the next few years: availa-bility of off -the -shelf equipment atreasonable prices; regular trainingclasses by every club; frequentregional meetings, mini conventionsand field days; an emergency netready to operate at a moment's noticefor every region; and 10,000amateurs ready, willing and able toserve the emerging Indian nation.

ntroducing a New Concept in HFcommunicationsA NEW SERIES WITH NEW FEATURES, NEW PERFORMANCE, AND ALL 9 HF BANDS.

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Come to KW for all your other amateur radio require-ments KW service and guarantee - KW maintains thetradition of service the company is renowned for.Output -transistors unconditionally guaranteed for 12months. The KW + TEN-TEC units offered above areintroduced as a prelude to fully UK assembledequipment.

* (A full range of accessories is available forKW + TEN - TEC equipment)Other KW units availableKW 107 Supermatch KW trap dipoleKW traps KW Balun KW antenna switch.

KW + TEN- TEC ARGOSY HF SSB/CW TRANSCEIVER10-80 metres, 100 watts (Switchable to 10 watts).Notch Filter. Full break-in on CW. Automaticnormal sideband selection plus reverse. 12 - 14v D.C.input. All solid-state. A WINNER AT LOW COST.

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50 HAM RADIO TODAY AUGUST 1983

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A CompactPERFORMANCEAerial System

By Steve Ireland G3ZZD

This article is the result of ten yearsoperation from a fairly typical semi-detached suburban location -where the plot the house stood inhad a length of some 21m and aback garden space of 8.5m square.From this apparently unpromising0TH all continents have been work-ed on 80m with 100W of SSB and on40m with 10W (DC input!) of CW.This was without scaring theneighbours to death with hugeaerial masts or digging up the backgarden to bury large quantites ofearth radials. The article, however,does not set out to offer a 'magic'recipe for LF success that must beslavishly followed, but to offer closetLF enthusiasts some encouragementand guidance in making the best oftheir locations. Fig. 1 shows a planview of the G3ZZD location.

Horizontal or vertical?

For a workable efficiency anantenna must be at least an elec-

For a radio amateurwho is interested in LF

operation a largegarden is usually taken

to be necessary,particularly if

intercontinental DXcontacts are desired.

Not true.trical quarter wavelength long at therequired operating frequency.Also, unless the height of the aerialapproaches a half wavelength aboveground at the operating frequencythe radiation from the aerial will bepredominantly at a high angle (ie.

greater than 30 degrees). This isfine for distances up to 10,030km,that is to say for UK and EuropeanQSOs, but fairly poor for DX. Thesignal from a low, horizontal anten-na will have to bounce off theionosphere and the Earth's surfacemany times before reaching the re-quired DX station and will thus beseverly attenuated, especially overa predominantly overland path suchas the 'short' or direct path to Japan.

In contrast, a quarterwavelength vertical, correctly fedagainst a reasonable earth, virtuallyguarantees a considerable amountof low angle radiation and DX. Thedisadvantage is in the height, par-ticularly on 160 and 80m. How manyamateurs in surburbia interested in80m DX could erect, let along dareerect, an aerial that is 66' high!

On obtaining my callsign andopting for LF operation, 160, 80 and40 metres being my favourite bandssince my earliest days as a shortwave listener, I considered the

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possibilities of the very limitedspace available for aerials. Aftersome thought I decided that themasts to support my putative aerialsystem would have to be self-supporting. Guyed masts, althougheasier to erect to a useful height,would severely reduce the span ofantenna possible between them, ow-ing to the need to allow space forsets of guys. Two self-supportingmasts could be placed tightly intothe far corners of the plot thus max-imising the possible antenna span.Guyed masts, I also surmised, tend-ed to be unsightly and might an-tagonise the neighbours.

Two larch poles, some 8m long,were purchased very cheaply from alocal woodyard. Plastic eyes, from alocal hardware store, were screwedto the tops of the masts in order thatnylon halyards could be threadedthrough, to allow easy erection ofantennas. The larch poles, after agood coating of wood preservative,were mounted in holes made by anauger drill, hired for the day from alocal garden centre, A halyard wasalso fitted to a vacant chimney -mounted TV aerial mast, conve-niently located halfway between the

masts and about 8.5m high.

The horizontal approach

Single band '80m' operation wasinitially opted for and a full size 1/2wave dipole was duly erected. Thecentre of the antenna was supportedby the chimney -mounted mast andthe legs of the dipole were stretchedbetween the two larch poles, withsome 21m of the aerial in a straightline. See Fig. 2. The remainder ofthe antenna at each end was slopedsemi -vertically downward andfastened to conveniently locatedgarden fencing. The antenna wasthen adjusted for minimum SWR at3.7MHz and had an SWR of under2.5:1 across the 80m band. Thedipole was fed with 75 ohm twinfeeder direct from the transmitteroutput. Even with only some 60% ofthe aerial in a straight line 5 and 9plus signal reports were obtainedfrom all around Europe and, withsome patience, all continents wereworked with 100W input of SSB. Ofcourse my signals were never thestrongest in the pile of stations com-peting for the DX but I usually gotthrough eventually and even theodd American station came back tomy CQ DX calls - at 6am on a

71MHztrap

1m-1

75R twinfeeder

Coil former =32mm dia x 7.5cm longCoil = 23 turns of 18 swg

wound over 6 cmCapacitor= 50p 2kV

Fig. 3. Trap dipole for 80m and 40m

71MHztrap

Fig. 4. Trap system for 160m, 80mand 40m

Length of wire between trapand top of vertical = 0.6m

9.5m

Earth and radial system(See text)

Winter's morning!After some time of operation on

80m it was decided to see how a lowdipole would work on 40m DX. As80m operation was still required aW3DZZ type trap dipole antennawas constructed from data (1) as inFig. 3. The coils were wound on off -cuts of plastic drainpipe, adjusted toresonance on 7.1MHz with a griddip oscillator and coated with var-nish for weather protection.

The parallel tuned circuits pre-sent a high impedance at 7.1MHz,effectively isolating the end sectionsof the aerial, allowing it to functionas a 1/2 wave dipole on both 80 and40m. On 80m the traps present a lowimpedance to the transmission andgive some inductive 'loading' to theantenna, effectively shortening thelength of aerial required forresonance. Thus a trap dipole aerial

is effectively shorter than a regular80m dipole, in this case about 12%.Similar results were obtained on80m as with the full size dipole.North America and New Zealandwere worked on 40m CW with 100 WDC input.

The vertical approach

Around this time I was lent acommercial trap vertical aerial by avisiting American amateur. Thisaerial, working on the principlepreviously described, covered 40through to 10m. The aerial, workingagainst a ground plane of two 1/4

wavelength radials per band stapledto the garden fencing and three lmx 4cm lengths of copper pipingdriven into the ground a few feetapart, was mounted on a 2m lengthof steel pipe attached to a garden

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swing. The DX performance ofG '17.7D on 40m was improveddrastically; DX stations could beworked on the vertical which werealmost inaudible on the horizontaldipole. Western America andAustralia were worked aroundsunrise with 10 watts of CW whiledaytime signals from the UK andEurope were only about 6dB downon the performance of the dipole.No deterioration was noticed in theomni-directional properties of thevertical antenna due to the bent andfar from assymetrical radial system.It should also be noted that the soilat G '127D, while being clay, ex-tends only to the depth of lm and ishardly the ideal 'earth'.

For those with a healthy bankbalance aerials of this kind may bepurchased for some £60-100 andgiving coverage of 80-10m for in-stance the popular Hygain 18AVT.I, however, had very little money atthe time and also harboured notionsof 160m operation. Could I not builda trap aerial myself to cover 160, 80and 40m - with as much vertical inthe high current portion (which

does most of the 'radiating') as possi-ble? After some thought the antennashown in Fig. 4 was constructed.

The resulting 'inverted L' aerialis an electrical quarter wave oneach band and was fed against anearth system consisting of three, lmlength earth stakes, two 1/4 waveradials for each 80 and 40m and asingle 1/4 wave radial for 160m.Figure 5 shows the trap should beadjusted for resonance at 3.7 MHzwith a grid dip oscillator beforeweatherproofing with varnish. Theradials were once again stapled toconvenient garden fencing.

The 9.5m vertical section of theaerial was constructed from lengthsof 2.5cm diameter copper -coatedsteel tubing, bought as a govern-ment surplus 'golf bag' verticalaerial. Aluminium T.V. mast typetubing could be used instead. Thesole support for the vertical sectionis one of the larch pole masts. Thehalyard from the larch pole was at-tached to the vertical section at apoint corresponding to the height ofthe larch pole. With the base of thevertical section held firmly in place

Larch pole

Vertical section

Universal mastcoupler

Fencing post

Jubilee clip forattaching feeder

Fig. 5. Base of vertical section oninsulated fencing post

3 7 MHz trap

Coil former=Coil =

Capacitor -

32mm x 15cm long44 turns of 18 swgwound over 13cm50p 2kV

Fig. 6. 3.7MHz trap

at the base of the larch pole, the vertical section of the aerial was walkedupright and the halyard pulled taut.The halyard was then wound inspiral fashion around the verticalsection and larch pole, alzout tentimes, and secured at the base of thelarch pole. This arrangement stoodthree seasons of spring gales beforebeing dismantled still intact.

A wooden fencing post wasdriven into the ground at the base ofthe vertical section. After the baseof the vertical section had been veryliberally wrapped in a layer ofplastic insulating tape (at least 3mmthick) it was attached to the pro-truding part of the fencing post witha universal mast coupler. Thereshould be a space of 5-7cm betweenthe vertical section and the larchpole. As the aerial is current fed in160, 80 and 40m the RF voltage atthe base of the vertical is low andthe plastic tape acts as an effectivebase insulator. The aerial is feddirectly with 50 ohm co -axial cable(RG 8/U), attached to the base of thevertical section with a 3cm jubileeclip (see Fig. 5).

The completed aerial was firstadjusted for minimum SWR in thecentre of the 40m band by alteringthe short length of wire between thetop of the vertical section and the7.1MHz trap. The section betweenthe 7.1MHz and 3.7MHz traps wasthen altered for minimum SWR inthe centre of the 80m band. Finally,the 13.5m section was altered forminimum SWR in the centre of the160m band. Alterations of this sec-tion may have some small effect onthe SWR on 80 and 40m, but thisshould not be serious enough towarrant any further alterations tothe antenna. An SWR of under 2:1was obtained across 160 and 40rnand most of 80m.

Results with this antenna wereexcellent - and it cost less than £12to build! The performance on 40mappeared slightly superior to that ofthe commercial trap vetical I hadbeen loaned. On 80m the DX perfor-mance was superior to the lowdipole by at least one to two 'S'points. Good reports were alsoreceived from Europe and the UK.On 160m signal reports of 5 & 8/9were received from all around theUK, using 25W pep of SSB.

References(1) P.69 A Guide to Amateur Radio 17th Ed.Pat Hawker G3VA RSGB Pubns 1978

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NOTES ANDCORRECTIONSTO THE DSB80

These notes cover all the errors that havecome to light since the article was writtenplus a few modifications.

1. PCB - there is an error in the layoutaround the microphone amplifier whichshort circuits the diode. This had been pre-sent since the prototypes, and explains whythe extra switch (TR6) was needed to pre-vent AF feedback when going from transmitto receive! As a result TR6 / R19/ R31 areno longer required. A small cut in the track isrequired - see drawing.2. R8 has been decreased to 47R as thezener may not have sufficient reference cur-rent when using a J310. Also, R10 has beendecreased to 1 5k to provide more CW driveand will give up to another watt of output.3. The unmarked capacitor on the originallayout plan adjacent to C39 is C40, and thatto the left of TR5 is C27. Also on the circuitdiagram, the capacitor marked "C39 10n"above TR4 is actually C40.

By Tony Bailey G3WPO

4. There are two C34s in the componentlist - delete the one in the 1 On group.5. The hole on the PCB for C39 is missing- instead connect one lead to the tap wireon T1, and the other lead direct to the topfoil, using short leads.6. It appears that the T68-2 cores havevarying permeabilities amongst batcheswhich result in the inductance of the coilsbeing different to the prototypes. It may benecessary to remove some turns from theVFO coil (use 40 turns anyway rather than41) if the frequency coverage is low loneturn at a time). Also, if the output filterstarts to resonate with the trimmers com-pletely unscrewed, first remove both C18and C22 1330p) and try to resonate. If thisthen provides insufficient capacitancereplace with 1 50p capacitors.

7. The +12V end of C17 does not havethe top side of the PCB cleared around thelead. This should be cleared with a smalldrill.8. On Fig. 3 IPCB layout) the TX/RX switchis shown wrongly wired - points 'B' 8 'E'should be on the same side of the switch,not 'B' 8 'D' as shown.9. If the receiver exhibits a tendency tomotorboat at low volume, change C30 to220,u.10. When wiring into a case, keep leadsaway from the immediate vicinity of theVFO - RF may be introduced which cancause CW chirp, or FMing of the DSB signal.Also, we advise decoupling the power supp-ly leads where they enter the cabinet, somesamples have had a tendency for the PA toself oscillate with long power supply ;cads.

The kit of parts (with all the abovemodifications incorporated) is still availablefrom WPO Communications at £37.45 in-clusive.

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54 HAM RADIO TODAY AUGUST 1983

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REVIEW:KW Ten-Tec Argosy

The view has often been expressedin these and other columns thatthere is a distinct lack in the newequipment market these days of rigsdesigned with the CW operator inmind. Usually CW seems to havebeen included as something of anafterthought, and to obtain atransceiver with anything more thanvery basic CW facilities from any ofthe Japanese manufacturers it isusually necessary to buy one of themore 'up market' models, thus pay-ing for features such as RF speechclipping, IF shift, variable selectivi-ty and so on, none of which are ofany great use to the amateur whooperates exclusively CW. It is arefreshing change, therefore, tocome across a rig like the KW Ten-Tec Argosy, which appears to havebeen designed with just such anoperator in mind. This is not to saythat it will not appeal to the SSB en-thusiast who is looking for a cheaprig, but it comes in the form of abasic, no -frills transceiver of goodperformance with a large number ofoptional extras, enabling the CWman to improve the rig's CW perfor-mance without having to pay for animproved SSB performance as well.

Review of the KW-TEN-TEC "Argosy"

By Richard DavisG3TDL

General descriptionThe Argosy is a small,

lightweight, well constructed, alltransistor rig covering all the HFbands with the exception of 1.8, 18and 24MHz, and produces 50 wattsoutput with a switchable powerreduction to 5 watts. In its basicform it provides all the features toget one on the air, and there is anextensive range of additionalmodules and accessories. These arelisted in Table 1, and it can be seenthat, by suitable selection, the rigcan be optimised for SSB or CW asdesired. All the additional modulesand filters can be fitted by the userand thus the rig can be bought in itsbasic form and upgraded later; auseful feature for anyone whosebank account is not too healthy.

The general appearance of theArgosy suggests that it has beendesigned with ease of operation in

mind. The front panel is neat anduncluttered with all unnecessarycontrols eliminated - indeed, thewriter was surprised to note theabsence of an RF gain control or at-tenuator, and more will be saidabout this later. Besides the maintuning and the band selector switch,the front panel controls are themode selector, (the modes beingSSB NORMAL, SSB REVERSE, CWand LOCK, the latter putting the riginto transmit with inserted carrierfor ATU adjustment), OFFSET(RIT), AUDIO NOTCH, DRIVE/MICGAIN, and AF GAIN. In addition,six pushbuttons select forward orreverse power metering, noiseblanker, calibrator, crystal filter,audio filter and wide or narrow set-tings for the latter. With the excep-tion of the SWR meter all thefacilities controlled by the pushbut-tons are optional extras, although allwiring for them is already fittedwhich means that, as mentionedearlier, the user can buy any ofthem at a later date and just plugthem in. The front panel layout iscompleted by a sliderule tuningdial, an illuminated meter which in-dicates forward or reverse power on

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transmit and signal strength onreceive, quarter inch jack socketsfor microphone and headphones,and an LED labelled ALC whichlights whenever the ALC circuitoperates. This is used in conjunctionwith the DRIVE control to set theoutput level, the control being ad-justed so that the LED just lights onspeech peaks (or when the key ispressed).

On the rear panel, besides agenerous heat sink, are the powerconnector (a four pole locking typewhich also carries mains to and fromthe ON/OFF switch), an S0239socket for the aerial, and six phonosockets, one for the key, two pro-viding a 12 volt DC power output foroperating accessories, and the otherthree being left unwired for possiblefuture modifications. In addition therear panel carries a screw terminalfor an earth connection, and theHIGH/LOW power switch, whichbypasses the PA and connects thedriver stage direct to the aerial, thusreducing the power output from 50watts to 5 watts. The internalloudspeaker is mounted in the baseof the rig, presumably with mobileoperation in mind. For base stationuse a fold -away stand (described asa "bail" in the handbook) is fitted atthe front of the rig, the effect beingto raise the front about two inchesabove the surface on which it is

standing so that the sound canescape. No provision is made for anexternal speaker, although it wouldbe possible to plug one into theheadphone jack.

Circuit description

The Argosy uses a single con-version system, the IF being 9 MHz;a block diagram is shown in Fig. 1.On receive, the signal from theaerial passes through the SWRbridge and then through a switchedlow pass filter for the selected band.PIN diode switches route it fromthere to a further filter, this time a.bandpass type, again switched tocover the selected band. The signalthen passes through a bipolar RFamplifier to a Schottky diode ringmixer, where it is mixed with thelocal oscillator signal to produce theIF of 9 MHz.

The local oscillator consists of aVFO tuning 5 to 5.5MHz (called the'PTO' by the manufacturers, due toits permeability tuning). The outputof the VFO is combined in a doubledouble balanced mixer with thesignal from a crystal oscillator, thecrystals being switched to selectbands. The output from this mixer ispassed through a bandpass filter,which is selected by the bandswitchto cover the required frequencyrange for the band in use, and then

amplified by a two transistor bufferamplifier before being fed to theRF/Mixer board. Here it feeds boththe receive mixer described above,and the transmit mixer, which willbe mentioned later.

Receive path

Returning to the receive signalpath, the IF signal from the receivemixer is amplified by a power tran-sistor buffer before being fed to theoptional noise blanker (Model 223);this unit is replaced by a link whennot fitted. From here it returns to theRF/Mixer board and passes throughthe main crystal filter before beingfed to the IF amplifier. The crystalfilter fitted as standard is a four poledevice, built on to a small plug-incircuit board which mounts on topof the RF/Mixer board. This can bereplaced by an optional 8 -pole filter(Model 220), giving better adjacentchannel rejection and sidebandsuppression; this improved filtersimply plugs in place of the stan-dard one. From the crystal filter thesignal passes to the IF/AF board,where it passes through a singletransistor buffer amplifier, and thento a socket which feeds an optionalnarrow crystal filter. This filtermounts on the IF/AF board and isselected by the XTAL push-buttonon the front panel of the transceiver.

WE'VE SIGNAL PATH

TORSI, IT SIGNAL PATH

XTAL

05C

OSCITDIXER

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FILTER

RF/MIXER

BL AKER Ch 110E470R

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CONTROL

56 HAM RADIO TODAY AUGUST 1983

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ModelNumber Description

21721821922022-3224226227

228645670700215214234

22211251126

500Hz IF crystal filter1.8kHz IF crystal filter250Hz IF crystal filter8 pole SSB filterNoise blankerCW audio filterCalibratorATU without SWRbridgeATU with SWR bridgeDual paddle keyerSingle paddle keyerHand mocrophoneDesk micorphoneDesk microphone andspeech processorMobile mountDC circuit breakerLinear amplifier swit-ching kit

Table 1 Optional modules andaccessories

Three types of filter are available,the Model 218, which is a 1.8kHzfilter for SSB reception, and themodels 217 and 219 for CW, thesebeing 500Hz and 250Hz widerespectively. The optional filter isfollowed by the main IF amplifier,an MC1350 IC, which then feeds adual gate MOSFET product detec-tor. The audio from this is fed via anactive notch filter to the optionalCW audio filter, model 224, whichis a separate board. This filter nar-rows the bandwidth to 450Hz or150Hz, selected by two push buttonson the front panel. If the filter is notfitted, a shorting plug is fitted in itssocket, from which the signal passesto the AF output stages. The AGC,which is audio derived, is fed fromthis point and controls the IFamplifier; no AGC is applied to theRF stage.

*The change from LSB on 3.5, 7 and10MHz to USB on the remainingbands is achieved by placing thelocal oscillator on the high side ofthe signal frequency on the lowerbands and on the low side on thehigher bands.

Transmit pathThe transmit signal is generated

at 9MHz by the SSB GEN board. Thecrystal in the carrier oscillator hasdifferent values of load capacitance,switched in by transistor switches, to

give the correct carrier frequenciesfor SSB normal, SSB reversed andCW. * The output of the carrieroscillator is fed to a CA3053 balanc-ed modulator, and also to thereceive product detector. Thetransmit audio signal from themicrophone is amplified by a twostage IC amplifier, the mic gaincontrol (labelled DRIVE on the frontpanel) being placed between thetwo stages, and is then applied tothe balanced modulator. In the CWmode a DC voltage is applied to oneport of the balanced modulator, un-balancing it and hence introducingcarrier. At the same time a variablevoltage from a second gang of theDRIVE control potentiometer is ap-plied to another pin of the balancedmodulator IC, varying its gain andhence controlling the amplitude ofthe CW signal.

The output from the balancedmodulator is fed to the RF/Mixerboard, where it pases through the-

main 9MHz crystal filter and is thenfed to the transmit mixer, anMC1496 double balanced mixer IC.Here the signal is mixed with thelocal oscillator signal to produce theoutput frequency. After passagethrough a buffer amplifier it is fed tothe main bandpass filter, and then tothe recceive RF amplifier, which isused as a buffer amplifier ontransmit. ALC, derived from thebuilt-in SWR bridge, is applied tothis stage. Following the RFamplifier is another stage, also ALCcontrolled, before the signal is fedto the final amp board. This boardhouses the driver and PA stages,both operating in class AB1 push-pull. The output of the driver stage isfed away from the board to thehigh/low power switch and thenback to the PA input. This allows thedriver to be routed direct to theaerial in the lower power position,bypassing the PA. The PA stage hasnegative feedback to improve its

HAM RADIO TODAY AUGUST 1983 57

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linearity, and its output is fed via thehigh/low power switch to the lowpass filter board, where it passesthrough the low pass filter and theSWR bridge before being fed to theaerial.

Keying for CW is full break-in,the key actually operating on thePTT line. The writer was surprised tohear a relay chattering away whilstoperating CW, since thesend/receive switching was said tobe all solid state. Careful examina-tion of the circuit diagram revealedthat a relay was indeed present,presumably to switch an externallinear since its contacts are simplywired to one of the spare phonosockets on the rear panel. It is puzzl-ing to find that this facility is notmentioned in the handbook.

In operationOnce the Argosy was safely in-

stalled on his workbench, thewriter's thoughts .burned to theabsence of an RF gain control. Sure-ly the lack of any form of gain con-trol on the RF stage (it is not evencontrolled by the AGC) was askingfor cross modulation problems to oc-cur in the mixer; this had to be in-vestigated. The band which pro-bably causes most problems in thisrespect is 40 metres, which at nightis occupied (illegally) by broadcaststations, leaving only a few kHz atthe bottom end free for amateur use.It will be obvious that trying toreceive weak CW signals within twoor three kHz of hundreds of kilowattsof broadcast transmission is a severetest of any receiver. As valve equip-ment has generally proved to berather better in this respect thantransistor equipment (hence the fit-ting of RF attenuators to mostmodern HF rigs) it was decided tocompare the receive performance ofthe writer's trusty old KW2000A(which has been modified asdescribed in this magazine's seriesto improve its overload perfor-mance) with that of the Argosy. Thetwo rigs were connected to the same

aerial via a changeover switch andthe KW2000A was tuned to various40m CW signals; the Argosy wasthen set to the same frequency andthe aerial switched over so that acomparison could be made. Theresults of this test were striking, butnot in the manner expected! Signalswhich were only just audible abovethe background hash on theKW2000A suddenly sprang intoclarity when received on theArgosy, and weak signals heard onthe Argosy were completely'inaudi-ble on the KW2000A! On the olderrig, the 'clear' spots in the bandwere filled with a continuous hashrunning at about S7, whereas withthe Ten-Tec they were completelynoise free. Once the rig was tunedoff a broadcast channel no trace ofthe signal occupying it remained. Itwas clear that the reason that noform of gain control had been usedon the RF amplifier was that nonewas necessary! This outstandingcross modulation performance wasundoubtedly due to the use of Schot-tky diode ring mixer, a devicewhich must represent one of themost significant advances inreceiver technology of recent years.

As may be gathered, thereviewer's first impressions of thereceiver performance werefavourable, and these impressionswere confirmed by subsequent ex-perience. The stability was good,very little drift occurring even fromcold, and none that could bedetected after the rig had been swit-ched on for a few minutes. The addi-tional filters worked well and wereuseful, the 500Hz crystal filter beingused for CW operation, with theaudio filter providing a furtherreduction in bandwidth. The nar-rower position of this filter (150Hz)was very useful, and was capable ofproviding true 'single -signal' recep-tion even on a crowded band, butthe wider 450Hz position providedlittle, if any, improvement over theperformance of the 500Hz cyrstalfilter, and in practice was never us-

ed by the reviewer. Perhaps it wouldhave been better if the 1.81cHzcrystal filter had been fitted, whichwould then have enables the band-width to be reduced progressivelyfrom 2.5kHz to 150Hz in four steps.Since the AGC is audio derived,and is taken out of the AF amplifierafter the audio filter, there is little tochoose between providing extraselectivity at AF or IF, especially inview of the receiver's excellentoverload performance.

Tuning dial

The analogue tuning dial prov-ed easy to use and was smooth in itsoperation. However, its calibrationaccuracy was not particularly good,the calibration varying not onlyfrom band to band but even betweendifferent ends of the same band.This is annoying since a little morecare in the setting up of the VFO,and the provision of trimmers to ad-just the frequency of the HFoscillator crystals, would have cor-rected this fault without any signifi-cant addition to the cost of the rig. Itis made the more annoying in thatthe system provided for calibrationadjustment, while simple, is ratherfiddly and the necessity of its fre-quent adjustment proved tiresomein practice. The adjustment is madeby moving the calibrated skirt of thetuning knob relative to the knobitself. The skirt is coupled to theslow motion drive by a frictionclutch arrangement, one revolutionof the skirt covering a frequencyrange of 100kHz. However, if theskirt is grasped it can be rotatedrelative to the slow motion drive. Itis the grasping of the skirt that is thedifficult part of this procedure,since not only is it only about 1/4"wide but it is mounted very close tothe panel and partially recessedbehind the tuning knob! Thereviewer's fingers are not very largebut he found some difficulty in thisoperation, and for anyone with largehands it would be very difficult in -

58 HAM RADIO TODAY AUGUST 1983

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deed. The calibrator, which is, in-cidentally, an optional extra, pro-vides signals at 25kHz intervals andis pulsed at a rate of two or threetimes a second to assist identifica-tion.

On SSB, the speech quality pro-vided by the Argosy when used withthe model 7W hand micropone wasgenerally liked by the stations work-ed. The model 700 is an electretmic, and is fitted with an internal 9volt battery. which, the manufac-turer's states, should last for about ayear in normal operation. It seemsstrange that the operating voltagewas not derived from the Argosyitself. However, it is not necessary touse the model 700 with the rig, andany high impedance microphonecan be used. In practice, the lack ofa speech processor was felt,especially in view of the corn-paritively low power of the Argosy,but again this is available as an op-tional extra. The notch filter was ef-fective and was useful in eliminatingheterodynes. Receive audio qualitywas good, despite the position of theinternal loudspeaker.

Power supply

The Argosy requires a supply of13.8 volts at 9 amps, and a mainspower supply, model 225, isavailable for base station use. Thetwo are obviously tailored to eachother, the connection between thembeing made via a four way ribboncable which carries not only the DCsupply but also the live side of themains to and from the ON/OFFswitch on the Argosy. The circuit isso wired that this switch is in serieswith the one on the power supply, sothat if the PSU switch is left in theON position the switch on theArgosy will turn the PSU on and off.It does not, however, control theDC, so that if the Argosy is usedwith any other power supply itsON/OFF switch will be inoperative.For mobile use the model 1125 cir-cuit breaker is inserted, into the DClead; this unit functions as bothON/OFF switch and overcurrentprotection.

There isabout the

very little else to saypower supply ar-

rangements, except that the model225 became very hot after the righad been switched on for somehours, when its thermal trip tendedto operate on peaks, despite the factthat the transceiver was operating

ARGOSY LAB TEST RESULTS

All tests were carried out using the equipmentin the upper sideband mode

RECEIVER SECTION

Receiver sensitivity for a measured receiverSINAD of 12dB. All voltages quoted as PD.

3.5MHz 0 22uV7MHz 0 22uV10MHz 0.9uV14MHz 0 25uV21MHz 0 25uV28MHz 0.4uV29MHz 0.4uV

Test for dynamic range of equipment. TheIntermodulation performance was measuredby connecting two signal generators througha 3dB hybrid combiner. Generator 1 wasset to 7.051MHz and generator 2 to 7.101MHz. The receiver section was tuned to7.000MHz and the generator levels wereincreased until an intermod product wasobserved equivalent to an S4 (1.4uV) rec-eived input signal.

The generator output levels required toinduce this condition were 4.5mV. This isequivalent to an uncorrected dynamic rangeof 70dB. The corrected figure, for a 12dBSINAD intermod level and with the hybridtaken into account, would be 77dB.Thenoise blanker circuitry on the review setdid not affect the intermodulation perf-ormance.

Susceptibility to internally generatedspurious signals.

With a 50ohm load connected to the aerialsocket, the receiver was tuned over theentire range. Birdies were noted at the foll-owing frequencies:

3.58MHz below AGC3.9MHz below AGC14.4MHz below AGC21 MHz S221.3MHz below AGC21.49MHz below AGC28.9MHz S430MHz S6

S meter characteristics

Meter input level dB change

S1 0 63uV 0S3 1.2uV 5 5S5 2uV 4.5S7 3 6uV 5

59 lOuV 9+20dB 90uV 19+40 2 5mV 29

The review set was loaned by KW Electronicsof Dartford , Kent.

TRANSMITTER SECTION

Unfortunately, the testing facility encount-ered difficulties when it came to thetesting of the TX portion of the equip-ment. The results of the two tone intermodtest indicated that there was a linearityfault causing IM products of only 8dBbelow a single tone.

A real signal at this level of IM productwould splatter all over the band causingcomplaints from other users several 10'sof kHz away. As it happened, the receivedsignal reports which we acheived in thepractical part of the review drew no crit-icism whatsoever.

The importers, KW Electronics alsotested the review sample for a TX faultand drew a blank. They said it wasworking fine. As it happens, we've alsoseen a full test report of the Argosy in theAmerican magazine Ham Radio whichshowed no design defect. We thereforeassume that something went wrong in theour test laboratory.When we tested the set, the two tonegenerator level was arrived at by look-ing at the peak microphone output on ascope (15mV) and using that as the base.In the event, it seemed to have been toohigh. Excessive test tone level at the micinput seems to be the only thing whichcan account for the shocking intermodfigures which we recorded. Since wethink that they are junk, we are notgoing to print them.

OUR CONCLUSIONS

The Ten-Tec Argosy feels very dif-ferent to the normal run of amateurradio gear. Perhaps this is because itoriginates in America rather thanthe Far East. Having used the reviewequipment for a day, I'm not surehow much I like the difference but...

Performance appears quite satis-factory although the dynamic rangeon receive is not outstanding. Againstthis, G3TDL reckons on the Argosyas being excellent in this area and Iwould rather trust him than a pairof signal generators.

Given the reasonable £399 pricetag, the Argosy appears to be goodvalue for money.

G4JST

HAM RADIO TODAY AUGUST 1983 59

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into an SWR close to 1: 1. However,shorter periods of operation did notproduce this effect.

Model 670 keyer

Most types of keyer can be usedwith the Argosy, and the handbookgives guidance as to suitable types.Ten-Tec themselves, of course, pro-duce two suitable keyers, the model645 dual paddle with dot and dashmemories, and the model 670 singlepaddle which is a basic 'elbug'. Bothtypes are designed to draw theirpower from the auxiliary sockets onthe back of the Argosy. The 670 wassupplied with the reviewtransceiver, and was used by thereviewer throughout his operationaltests. It operates satisfactorily, theonly criticism being that the feel ofthe paddle is rather spongey,resulting in some sending errorssince it was not obvious whether thepaddle had been pressed over farenough to make contact. Thewriter's CW speed is not very fast(about 12 wpm) and it was thoughtthat this problem would assume aneven greater significance at higherspeeds. The 670 is about the sameprice as other similar units on themarket. Side -tone, adjustable bothin volume and pitch, is provided bythe Argosy itself.

Model 228 ATU

Like most transistor transmittersthe Argosy is broadband tuned, sono PA tuning adjustments appear onthe front panel. The PA is designedto work into a 50 ohm load and thismeans that full output wil not be ob-tained into any other impedance; inpractice it will be necessary to usean ATU with the rig, unless one isable to use a separate dipole foreach band. Ten-Tec produce twosuitable units, models 227 and 228,the only difference being that the228 includes an SWR bridgewhereas the 227 does not. The unitsare well constructed and provide forthe matching of a variety of aerials,both balanced and unbalanced. Thetuner is in the form of a T -match, allthree elements being variable, andis very easy to use, the inductor firstbeing set for minimum reflectedpower and the match then beingtrimmed by varying the twocapacitors. The matching unit is un-

balanced and is obviously designedfor coax -to -coax matching, butfacilities are provided for the con-nection of a single wire aerial or abalanced line, the latter being con-verted to unbalanced by a built-inbalun. This feature, however, is oneof the two minor shortcomings of theunit, since the balun is unable tocope with lines having a high SWRwithout becoming lossy, and thissets a limit to the range of im-pedances which can be matched,particularly at low frequencies. Amaximum value of 500 ohms isquoted in the instruction leaflet, andthis strikes the writer as being ratherlow in terms of the impedances like-ly to be encountered on open wirefeeders; however, this limitationdoes not apply to the unbalancedconfiguration. A useful feature ofthe unit is the ability to select any ofthe three aerials plus a dummy load(not supplied) by the use of a frontpanel mounted switch. One positionbypasses the tuner and routes thetransceiver direct to Aerial 1. Con-nections to these three aerials, thedummy load and the transceiver areall made by S0239 connectors on theback of the ATU. Additional screwterminals are provided for the singlewire and balanced feeder for Aerial3 only. The writer would have likedto see the switch arranged to earththe aerials not in use, but this is aminor point. The only other minorcriticism is that the SWR bridge israther insensitive; it was necessaryto be radiating about 5 watts to ob-tain a full scale power reading,whereas the author likes to tune upat milliwatt levels.

Handbook

The Argosy handbook is verygood; whilst not as 'glossy' as thosefor some Japanese rigs it is well writ-ten (with no Japanese English) andcomprehensive, including circuitdiagrams, very good layoutphotographs, complete parts lists,voltage measurements and circuitdescriptions of all modules. There isalso a two page essay on the virtuesand vices of solid state poweramplifiers! The quality of the hand-book combined with the simplicityof design of the Argosy (due to theabsence of synthesisers,microprocessors and digitaldisplays), and the neat, unclutteredconstruction of the transceivermeans that the rig should be quite

Rear connections, except aerialsocket at other side

easy to service, a point to be bornein mind in these days when most rigsare so complex that they need to bereturned to the manufacturer in theevent of a breakdown.

Conclusions

To summarise, the Argosy per-forms well and is easy to operate.The receiver performance is par-ticularly impressive. As a generalpurpose rig it does not representbetter or worse value for money thanits Japanese competitors, althoughthe ability to buy the basic rig and toadd extra facilities at a later date isuseful, particularly for someonestarting in amateur radio for the firsttime. One point where the Argosydoes score over its competitors is asa CW rig, as it is possible tocustomise it for a top flight CW per-formance at a much lower price thanother rigs, since one does not haveto pay for improved SSB perfor-mance at the same time. A further,though hidden, cost saving featureis the ease of maintenance, since itis unlikely that a competent amateurwould ever need to return it to themanufacturers for repair. This sav-ing is further helped by the simplici-ty of design which will, of course,increase reliability; and by the veryconservative rating of the PA, whichcan operate into a considerablemismatch without damage. All inall, the writer has thoroughly en-joyed reviewing the Argosy; it was agreat wrench to have to give itback.

60 HAM RADIO TODAY AUGUST 1983

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ALL KEYBOARD FREQUENCY CONTROLLED.16 Memory Channels - Green L.E.D. - Size 50mm x 140mm x 172mm

RECEIVER TRANSMITTERReceiving System Double superheterodyne RF Output Power 25 watts minimum (high)Intermediate Frequency 16.90 MHz (first), 455 kHz (second) 5 watts adjustable (low)Sensitivity Better than 0.2 µV for 20 -dB NQ Modulation Method Variable reactance FM

Better than 0.15 µV for 12dB SINAD Frequency Deviation :5 kHz maximumSquelch Sensitivity Better than 0.15µV at threshold Spurious Radiation Better than -60 dBSelectivity .6 kHz or more at 6 dB down Offsets Simplex, :600 kHz, programmable±15 kHz or less at 60 dB down Autopatch System 16 -keyAudio Output 2 watts or more 18 ohms, 10% THDI PLO Tone Option U.S. Version only

1.750 Hz European version only (Built-in)Priority Channels TwoMicrophone Dynamic type, 500 -ohm

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AZDEN PCS4000user view

Two metres is a completelydevalued band. Frankly, I can't tellthe difference between FM on144MHz and FM on 27MHz. The vastmajority of QSOs are so banal andtedious that they are enough tomake anyone with a real interest inradio cringe in disgust.

Regretfully, although 2mrepresents the thick end of thewedge, the thin end is quite ap-parent both on 70cm and the HFbands. Having recognised thatthere is a problem (and you had bet-ter believe that there is one) youmust look for the cause. I perceivetwo reasons: 1) The multiple choiceRAE is now so easy to pass that thesum of knowledge is little more thanparrot fashion licence conditions,and the how and why of wiring amains plug; 2) All you need to haveto get on the air is an Access cardwith a credit limit of around £400.

Once there was a time when theonly way to get operational was tobuild your own equipment, and thefact that people don't do thisthreatens the very fabric of the hob-by itself. To support my view, I justask you to answer a single question:When was the last QSO where youdiscovered something useful to dowith radio? I can't remember either.Amateur radio seems more andmore to be one giant CB channelstretching from 1.8 to 440MHz and Idon't like it.

What has all this got to do withan Azden PCS4000 micro -computercontrolled 2m FM transceiver? I

have been reviewing this machineand I want everyone to be quite sureof the starting point of my own per-sonal prejudice. This way, it savespeople the bother of accusing me ofbias when I openly admit it.

What it is

The PCS4000 is a synthesisedFM mobile box offering either 12.5or 25kHz channel spacing over therange 144 to 146MHz. It produces25W (measured 30W) of RF and is at

By Frank Ogden G4JST,Editor Ham Radio Today

least as sensitive as any other com-parable box.

It also offers all the featureswhich mobile black box users havecome to expect; the scanningfacilities are possibly the most ad-vanced that I have yet come across.The equipment allows storage of upto 16 different frequencies (with orwithout 600kHz shift for repeateruse) and also has the facility foroperating with non standard fre-quency shifts.

The memory facilities are splitinto two banks of eight which can bescanned either as eight channelswithin a single bank or sequentiallyfor the full 16. In addition thetransceiver allows scanning bet-ween two frequencies (12.5 or25kHz steps) defined by memoryfrequencies stored in positions 7 &8. This feature is useful when look-ing for traffic in the 144MHz sector.

The set also includes the nowubiquitous scanning and steppingcontrols on the microphone which,in theory, makes mobile operation

rather easier. An additional buttonon top of the microphone PTT barrecalls the contents of 'memory one'on depression. You would normallystore 145.5MHz in the MI position sothat you can summon up the callingfrequency without taking your eyesoff the road. However this little extraisn't nearly as useful as it sounds.

The front panel

I wasn't the only person toremark that the front panel is themost distracting that has ever beenseen on a mobile R/T. It is not simplythat the thing lights up likeChristmas in Oxford Street, but thatit has more buttons than a scientificcalculator cum digital alarm clockradio with teasmaid thrown in.

Specifically, there are threeknobs: vol/on/off, squelch andmemory mode. So far so good. Thetrouble is that there are a further 19buttons and 23 indicator lamps. Thisdoesn't include the four digit LEDdisplay. The main programmingcontrol is a 16 button keypad.Although the buttons themselves aremarked numerically, these legendsare of no significance. In essence,the desired frequency, either for im-mediate use or for memory storage,is arrived at by sequential stepping.In theory it should be possible toQSY quicker via the keypad. Inpractice, it is so fiddly to use - im-possible when mobile - that themicrophone up/down buttons arethe main control.

The indicator lamps include astring of eight corresponding to thememory channel selected, plus anextra light to indicate whichmemory bank is in use. Redundantdecimal points in the LED main fre-quency display indicate functionssuch as 'M I select' 600kHz shift,reverse repeater, loop unlock, etc.Another string of lamps (five) give avisual representation of receivedsignal strength and transmit outputpower while a few more immediatelybelow them show such things as an

HAM RADIO TODAY AUGUST 198363

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unsquelched condition (I wouldhave thought that this state shouldbe obvious) low power operationand unit in transmit.

I don't propose to give a blow byblow account of what each controldoes. It is sufficient to say that thecomputerised PCS4000 offers everypermutation of the basictransmit/receive function that youcan imagine and then a few more ontop. I think that it is rather moreuseful to look at the basic radiosystem performance in a review.After all, that is what its all about .isn't it?

In use

Programming the memory hasquite a lot in common with computeroperating. It looks difficult at firstsight, but once you understand theprogramming language, it is nogreat task. Having said this, it isquestionable whether you need allthe memory facilities which this boxoffers. I personally think that theheight of evolution of the FM 2mmobile box was embodied in theIcom IC -240E. From then on,everything went downhill. Thatmachine had a good basic perfor-mance - not great but good - andit sported only those controls whichhad a direct bearing on the basicoperation of a radio telephone.

The IC -240 had a nice, big/clickstop knob to select the channel. Ithad a simplex/repeater switch. Ithad volume and squelch. It had allthe basics and no more. As a result,

you could reliably operate the setblindfold and with one arm behindyour back. I couldn't do this with thereview Azden set or any of the Icomsuccessors.

The microphone control buttonson the PCS4000 could provide allthe frequency setting functions but Ifound that you always had to checkthe result of an operation on thedigital display on the set's frontpanel. Get the operating sequencewrong - which is very easily done- and you would find youselftransmitting with a 600kHz shift foran intended simplex contact orworking on the wrong frequency alltogether. I often found myself step-ping through the memory channels- after inadvertent operation of theMI button - rather than the desired25kHz steps that I wanted.

The audio quality of the rig, inboth transmit and receive wasgenerally very good. The soundfrom the small internal speaker hada satisfactory tonal balance formobile use. Only one signal reportsuggested that the transmissionlacked slightly in top. The yellowdigital display was barely brightenough to read in high ambientdaylight conditions. The FM limitercircuitry rendered the unitreasonably insensitive to impulsetype interference such as ignitionnoise.

Faults

As delivered, the unit appearedto have a slight fault on transmis-sion. There was a regular tick...tick tick noise on the transmissionwhich, although not impairing in-telligibility, was annoying for sta-tions at the listening end. As of thetime of writing, I haven't spokenabout the problem with the im-porters, Waters and Stanton.However I imagine that this tickingnoise is a one off fault with thereview sample and would not nor-mally be encountered. Try beforeyou buy though. There is a poten-tially more intransigent problemwith the PCS4000 which appears tobe connected with the RF design.

The transceiver displays anumber of spurious responses. Inpractice, this means that you can belistening for example on 145.5MHzwith a police communicationssystem occasionally opening thesquelch. While the Home Officeshows little scruple in adoptingamateur frequencies for its own use,I seriously doubt whether it has ac-tually taken over the 2m calling fre-quency. I noted several cases ofhigh band breakthrough during thecourse of the review.

I must state that I live out in thecountry in an area of Sussex not par-ticularly noted for the RF conges-tion.

64 HAM RADIO TODAY AUGUST 1983

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Out of band interferenceamounted to a weak but copyablesignal at several places over theAzden's tuning range. The max-imum level of the interference wasin the S2 range. It was quite enoughto mask a weak wanted signal.

I explored the review unit'sresponse over the frequency range100 to 250MHz at a display setting of145.5MHz and found at least half adozen places where a difficultycould arise. I don't want to make toomuch of this problem though.Unless you were in an area of highinterference field strength, thespurious response would only haveminor significance.

Circuitry

Neglecting all the digitalhousekeeping and lightflashing cir-cuitry, the PCS4000 is a double con-version superhet with a first IF of16.9MHz and a second one of455kHz. A single loop mixer typefrequency synthesiser provdes thelocal oscillator injection. Intransmit, frequency modulation isachieved by pulling a 16.9MHzcrystal with an inductance loadedvaricap. The RF side of the box is inall respects downbeat and conven-tional. So why are there roughedges on the out of band rejection?

I think that it is down to moneycoupled with a bit of poor PCBdesign. For instance, the RX frontend circuit includes a three stagehelical filter assembly between theRF pre -amp (the inevitable dualgate MOSFET) and the mixer (anequally inevitable dual gateMOSFET). This alone should ensurethat the image response is excellent.It wasn't particularly good when

HAM RADIO TODAY AUGUST 1983

measured under test, a fact whichcan possibly be attributed to poorscreening or layout.

My conviction that there issomething a little bit untoward inthis department is re-inforced by thefollowing observation. I managed towork Tony Bailey G 3W PO - helives some eight miles down the road- using a dummy load screweddirectly into the aerial socket at theback of the set. He received mydummy load transmission in theregion of 5 by 3. I was able to givehim a similar report on receive! Thismeans that two way radiation wasoccuring from either themicrophone or power lead. Thiswould be quite enough to render theinherently excellent characteristicsof the helical filter useless.

I am also of the opinion thatAzden has saved a few bob, to thedetriment of RF performance, by us-ing a cheap first IF filter arrange-ment. Where a professional PMR setwould use an eight pole monolithiccrystal filter, the Azden uses a pairof cascaded two pole crystal roofingfilters. Without pulling out these two16.9MHz units and doing ameasurement - which you can't dowith someone else's equipment -you can only make a guess at thecombined response of the twofilters. I would wager the cost of therig that it is at least 30dB worse thana proper eight pole filter, correctlyinstalled.

The result of this is that adjacentchannel signals, amplified by the RFpre -amp, find their way at fairlyhigh level to the second mixer in-corporated in the MC"1-159 IF anddetector block. In practical termsthis means that strong 2m signalsfrom nearby stations can and do

cause some desensing; the MC3199was not intended for use without ahigh level of pre -filtering. Underlab test conditions, a 2541V signal800kHz out from a wanted signalcaused noticeable de -sensing.

Summary

I would cheerfully swop all thedigital gizmology, bells and whistlesof the PCS4000 for a decent crystalfilter unit. In fairness to everyoneconcerned, the Azden set isn't theonly one on the market today with afew problems. A leading brand bestseller is equally at fault, if notworse, yet no-one seems to notice.In a way, I feel that it all comes backto that tirade that I launched into atthe beginning of this review. Manyof today's amateurs are concernedmore with buttons and lights thandown-to-earth RF performance. TheAzden will undoubtedly suit a largesector of the hobby who will be verysatisfied with it. However, it is notfor me but then I'm biased . . .

AZDEN PCS4000 TEST RESULTS

RECEIVER SECTIONAll measurements carried out at 145.5MHz

Input level for 12dB SINAD: better than0.2uV PD (limit of test equipment)

Signal level and frequency for noticeabledesensing (15 to 12dB SINAD change):12mV 147.5MHz250uV 146.3MHz300uV 144.7MHz4mV 145MHz, 146MHz

Significant responses (12dB SINADor greater) were found at the followingfrequencies: 119, 172.5, 177.5, 185, 240MHz. The injected signal level was in theregion of 10 to 25mV.

TRANSMITTER SECTION

12V

5.5Win low power position

13.8V

6W

24W 30Win high power position

OUR OBSERVATIONS

The receiver sensitivity was excellent -

it was one of the best that we have comeacross in FM 2m boxes. However, thesusceptibility to both in and out of bandsignals spoils the picture rather more thansomewhat. The unit is compact, flashy andwill undoubtedly find wide appeal giventhe reasonably competitive price tag of£239. The technical wrinkles would notbe noticed for run of the mill operation.

G4JST

65

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ALL MODETRANSCEIVER

Part 2Notch filter and

pre selectorBy Frank Ogden G4JST and Tony Bailey G3WPO

PROJESII

THE NOTCH FILTERThe basic circuit for the IF notch filter was included withthe main central IF processing unit in the July issue and adescription of how it works in the April issue. The circuithas not changed, except for the addition of C73, inparallel with VC1. The original circuit called for a 60pFvariable capacitor, but as the commonly available unitsare 50pF max, some small additional capacity wasneeded. The air spaced variable used is a high qualityJackson Bros unit, to keep the Q high, and therefore thenotch deep and narrow.

The purpose of the filter is to remove the heterodyneswhich so often appear within the receiver's passband, andwith the notch depth obtainable from this unit (measuredat 50dB), all but the strongest interfering signals can be

reduced to negligible proportions. There is very littleeffect on the intelligibility of voice signals, due to thehigh Q, and therefore the narrow bandwidth of thenotch.

VC1 varies the frequency of the notch, and in themaximum capacity setting, the frequency is just outsidethe high side of the 2.2kHz SSB filter - the capacitor canbe left at this setting when the filter is not in use.

ConstructionThis module is constructed on a small PCB, designed

as a front panel control for the main transceiver. Thevariable capacitor is mounted on the front panel, with thePCB soldered to the two rear stator lugs of the capacitorso that it is self supporting. Connection to main CIFPU isvia miniature 50 ohm coaxial cable.

Construction is simple once the ferrite matchingtransformer is wound as follows.1. Take a length of 0.25mm enamelled copper wire 9cmlong, and strip one end for 5mm. Carefully wind fourcomplete turns through the core, with one turn countingas a wire inserted through one hole and then backthrough the other. This should leave both wiresprotruding from the same end of the core but fromopposite holes. Reduce the unstripped piece of wire to1cm in length and remove 5mm of insulation.2. Take two lengths of wire, each 5cm long, strip 5mm offone end of each, twist together and solder. Insert the freeends through the two holes, from the end opposite thatwhere the wires are currently protruding, until about1cm of the twisted end protrudes. Pass each wire backthrough the other hole, and repeat again, so that a centretapped four turn secondary is created. Reduce the wiresto about 1.5cm in length and strip and tin the ends.

The transformer and remainder of the componentsexcept VC1 are then inserted and soldered. X1 shouldhave its base against the PCB.

66 HAM RADIO TODAY AUGUST 1983

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Above: PCBartwork forpreselector unit.The large areaof copper is formounting thevariablecapacitor, VC1 Left: PCB

artwork fornotch filter. Theboard mountson the 50pFvariablecapacitor.

VC1 goes in last. The lugs at the rear of the statorplates are inserted through the large holes in the PCBuntil they just protrude from the underside, thensoldered, making sure that the capacitor is exactly atright angles to the board. A still piece of 18 or 20 swgwire then links the earth terminal on VC1 to the holeprovided on the PCB.

TestingTo test and align the unit, connect it up to the

CIFPU, using a short length of miniature 50 ohm coaxialcable. The filter ends of the cable are connected to theunderside of the PCB, and it is important that the inputand output are the correct way round.

Turn VC1 to maximum capacity and repeak IFT3 andIFTzl on the CIFPU for maximum signal strength. If aheterodyne is now found, it should be possible to reduceit to negligible levels (depending on its strength). Toadjust RV1, tune in a carrier so that the beat note is about1kHz. Adjust VC1 for best rejection, then adjust RV1 forany improvement (the effect may be small). Repeat theadjustments until no further improvement is possible.

This completes adjustment of the filter. When not inuse, VC1 should be left at maximum capacity. The IFtransformers on the CIFPU either side of the notch filtercircuitry will require slight adjustment after fitting thenotch unit.

PRESELECTOR MODULEThis module uses the same circuit as for the SynthesisedGeneral Coverage Transceiver design published in theJanuary, February and March issues. It is a bit of_adeparture from standard designs by being a tunable lowpass filter arrangement, rather than bandpass. However,it is very effective, and removes the need for banks ofswitched tuned circuits, leaving only one control to peakacross the whole coverage of the Transceiver. At higherfrequencies it does give a bandpass response. Inconjunction with an ATU, ultimate rejection will exceed100dB.

RFC1 simply removes any static voltages from theaerial by providing a DC bypass, and Cl/L1, and C2/L5are series tuned IF traps at 10.7MHz. The preselectorproper comprises L4, L5 and L6 plus VC1, a 500pF twingang air spaced capacitor. The inductors are wound onAmidon Dust -iron cores type T37-6.

The operation of the filter can be seen from thediagram - as the capacity reduces, the preselectorresponse transforms from lowpass, through anintermediate stage of wide bandpass to fairly narrowbandpass at minimum capacity.

ANTENNA L2 L3

Preselector circuit diagram

ConstructionThe preselector is built on a single sided PCB, with

VC1 also mounted on the board. As there are a largenumber of different ways in which the twin gangcapacitors can mount, depending on their make, avariety of holes have been provided. If none of these suityour capacitor, you will have to drill some more. Whichside of the board the capacitor spindle projects from isimmaterial, but the capacitor should be positioned so thatthe connections to the stators from the PCB pins are asshort as possible (use stiff wire). If long leads have to beused for this, then a screen will have to be placedbetween the wires so that they cannot 'see' each other.

The three inductors are wound using 0.4mmenamelled copper wire. L2 and L4 each require a lengthof 29cm to complete the winding. L3 requires 61 cm - inthe case of this coil it will not be possible to get all theturns on in one layer. Wind as many as possible as asingle neat layer until the core is full, then wind theremaining turns over the first layer, spaced round thecore.

When all the components are in place, the unit canbe tested.

AlignmentConnect up the preselector to the CIFPU using

miniature 50 ohm coaxial cable. When turned to a lowfrequency, the preselector response should be verybroad. At high frequencies the bandpass characteristicshould become apparent - on 21 or 28MHz, there

HAM RADIO TODAY AUGUST 1983 67

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should be a very slight double peak in the tuning of thepreselector. If the response is very sharp then a turn ortwo will need removing from L3. On the other hand, ifthe double peaking is very pronounced, then a turn ortwo should be added to L3.

The 10.7MHz traps are adjusted by feeding in a verystrong 10.7MHz signal to the input of the preselector,and adjusting the cores of LI and L5 for minimum signal.This quite difficult to do, as their rejection,combined with the IF rejection of the CIFPU, results invery little signal getting to the IF circuits once the coresnear resonance.

Once the unit is adjusted for an amateur band, itshould not need readjusting within the band, If it does,then it is likely that L3 requires some turns adjustment.

The preselector module will eventually be mountedon top of the main CIFPU diecast box, as another frontpanel control.

Preselector component layout

VC,

RFC'

EC=C3L2

CI

LI

INPUT50' COAXFROM ANTENNA

OUTPUTSO,' COAXTO CIFPU

5O COAXIALCONNECTIONS MADE

TO UNDERSIDEIN FROM

POINT H'ON CIFPU

Notch filtercomponentlayout

OUT TOPOINTON CIFPU

Notch filter

R16 15R 5% carbon film 0.25 wattRV1 100R 10mm carbon presetVC1 Jackson C808 50pF max variableC73 5p silver micaX1 10.7MHz HC -18/U

T3 4 turn primary and 4 turn CT secondary, woundusing 0.25mm en Cu wire, on Fair -Rite Baluncore type 28-43002402

Preselector

C1,2 47p ceramic plateVC1 500pF + 500pF air spaced variable

RFC1 TOKO 7BA RFC 1mHLI, 5 TOKO KANK 3334R

L2,4 22 turns 0.4mm en Cu wire, wound on AmidonT37-6 core.

L3 45 turns 0.4mm en Cu wire, wound on AmidonT37-6 core.

A complete set of parts for both modules includingthe air spaced variables for both is available from WPOCommunications.

The Notch Filter costs £11.20 and the Preselector£11.00, both inc VAT & p&p.

Printed circuit boards are available separatelypriced £2.60 for the pair inc.

Table 1 components list

Omega IF board: components listThe following components were missed from thetable of components for the IF board in the Julyissue:IFT I, 2, 3, 4, 5, 6, 8IFT5T1

T2T4RFC1,2

Toko KACS4520AToko KACS38946:1 wound on Fairite balum coretype 28-43002402 using 0.25mmenamelled copper wire2:6 wound as TiToko KACS6184AToko 7BA 100uH

68 HAM RADIO TODAY AUGUST 1983

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NEW PRODUCTSHF vertical aerialThe R3 half -wave end fed verticalaerial is a new addition to theCushcraft range, and it covers the14, 21 and 28MHz amateur bands.Resonance and matching isachieved by a combination oftraps and a motorised tuning unitat the base. Because of the highdriving point impedance there isno need for an elaborate system ofearthing and/or radials.

The R3 comes complete with aremote control box for the ATU,enabling a claimed VSWR of1.2:1 (or better) to be achieved atthe 50 ohm feed point at anyfrequency in any of the threebands.

The claimed specification is:gain 3dB (the catalogue does notsay what reference is used for gainmeasurement); horizontalradiation pattern -omnidirectional; power rating2000W PEP; height 29.9ft (9.13m);weight 11.51bs (5.2kg); voltagerequired 110/240V AC; controlline voltage 24VAC; terminationS0239; material - seamlessaluminium; control boxdimensions 6x4x4 inches(152x100x100mm); wind survival100mph (160.9km/h).

Further details from NorthernCommunications, 299-303Claremount Road, Claremount,Halifax, West Yorkshire HX36AW. Tel (0422) 40792.

Callsign badgeWisbech Amateur Radio hasbrought out a new callsign sticker.It is made of magnetic materialand will 'stick' to any reasonablyflat surface. The callsign is blackagainst a white background, withthe legend "amateur radio station"in red. The badge is 224x76mm insize and costs £4.50 (or £5.25 for areflecting version) from WisbechAmateur Radio, 20-21 NorfolkStreet, Wisbech, Cambs PE13 2LFTel 0945 581099.

(The Editor thanks the supplierfor the freebie, but points out thathis first name is Frank, not!Crank!)

AMTOR add-onThe ICS Electronics Amtor Mk. IIboard is designed to convert anexisting RTTY station to theAMTOR mode.

It connects between theterminal unit and thekeyboard/printer, as well as to thePTT line of the transceiver.

The interface to the Mk. IIboard is at TTL levels, and astabilised 5 volt 400mA supply isneeded. Nine externally mountedLED status indicators and sixexternally mounted switches mustbe connected to the board tomake it operational.

Designed by Peter Martinez

AMATEUR RADIO STATION

G4JST

el

'111"k. 112011 -

IC

1

:4

C.4

5.rTtk1;461 ti4

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si'l.R-11 - ocsc,,

AMMO Mk 11.1

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G3PLX, the Amtor Mk.LI board iscompatible with all AMTORstations currently on the air. It isavailable from ICS Electronics Ltdat £107 for a kit, or £135 built andtested. Details from ICSElectronics Ltd., PO Box 2,Arundel, West Sussex BN18 ONX.Tel. (024 365) 590.

Antenna switch

The Drae 3 way antenna switchhas a claimed insertion loss of lessthan 0.3dB at 145MHz, and lessthan 1dB at up to 500MHz. It hasS0239 connectors and is rated at250W RMS at 50 ohms.

Unused aerials are connected toa high value resistor to drain staticbuild-up. The switch, which hassilver-plated brass contacts, isconnected to the sockets by a PCBtransmission line.

The antenna switch is availablefrom either Drae stockists, ordirectly from the manufacturer:Davtrend Ltd., the SandersonCentre, Lees Lane, Gosport,Hants P012 3UL (Tel Gosport20141) at a cost of f15.40.

MoonbouncemagazineThe Lunar Letter Magazine is amonthly 44 -page Americanpublication designed forVHF/UHF enthusiasts, coveringall forms of weak signalpropagation, with a specialinterest in EME.

Regular columns includeseveral band reports of mainlyAmerican interest, includingTerrestrial Reports, and EMENews reports for each of the 144,220 and 432 MHz bands. There isa letters page, a DX report, Swapand Sell and constructionalarticles.

The magazine is now in itssecond year, and is imported intothe UK by: D Parker, 14 MoorsideCrescent, Drighlington, Bradford,West Yorkshire BD11 1HS. Ayear's subscription costs £11.

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HAM RADIO TODAY AUGUST 1983 69

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Radio CommunicationsAntatew P M R Mer.ne

AVON

6 GOLF CLUBLANE,

SALTFORD,BRISTOL

Tel: 02217 2402Open Turn Sat 9ant 9pe

Close Mondays

it NC

5773ea S'Ot

=1111=13IrCAMBRIDGESHIRE

WISBECH AMATEURRADIO IOIICOM

WisbechTel: 0945-581099. Open: Mon -Sat 9-6HP facilities. Part exchange welcome.

CHESHIRE

km= rtitabOrgandis C CO LTD

58-82 Lower HIllgate, StockportTel. 061-480 4872 Open: Mon & Wed 9-6lets nights Tullis & Fri 9-7pm. Set 9-5.30.

Closed ThursYaesu, Sommerkamp, Diawa, Jaybeam, Kenpro.

Weitz, Datong

HAMPSHIRE

FARNBOROUGHCOMMUNICATIONS97 Osborne Rd, North Comp,

Farnborough. Tel. 0252-518009Open: 8 days 10-8

Yaesu, Icom, FDKs, Mosley aerials, Jaybeams,G Whips

KENT

ThanetElectronics143 Recular Rd., Herne Bay

Tel. 02273-63859Open: Mon -Fri 9-5.30, Sat 9-12.30

(Closed for lunch 1-2)

Picots

E

FOR YOUR BUSINESS TO BEINCLUDED, CALL

SHEILA OR JAN ON01-437 1002

LANCASHIRE

231 Chorley Rd., Swinton,Greater Manchester.Tel: 061-793-1010

Open 7 days a week.TRIO. YAESU. ICOM, GWHIP.

YOUR RIG IN OUR

HANDS

tit

THE YAESU EXPERTS CONSULTG3LLLSales Dems & Repairs Mod Kits

HOLDINGS LTD

39-41 Mincing La. BlackburnTel: 102541 59595

CLOSED THURSDAYS

ISHERWOODSELECTRONICSHozier Street, Blackburn

Tel. 0254-57616Open: Mon -Fri 9.5, Sat 10-1

An Aladdin's Cave of Components

LEICESTERSHIREELLIOTTELECTRONICS

111.1.4,10 MI' USIA.

26-28 BRAUNSTON GATE,LEICESTER. TEL: 553293

Open: Mon -Sat 9.00am to 5.30pm

LONDON

THE CENTRE10 MERTON PARK PARADE,

KINGSTON ROAD, SW19Tel: 01-543 5150

Open: 6 days 9am-6pm date night Weds until 8pm)

DAVEMICK

G8SYGG6LHL

The Enfield EmporiumAMATEUR RADIO

Hours Mon to Sat 9-6. Late Friday 9-8. Sun morn 10-1

281 Hertford Road, Edmonton N9Tel: 01-804 0128

teeElectronksttd

400 Edgware Rd. W2Tel: 01-723 5521

Open: Mon -Fri 9.30-5.30.Sat 10-4.30Thurs 9.30 -fpm

THE MARINE ELECTRONIC CO LTD1-4 Swan Mead, SE1 4SY. Tel 01-237 3474

Open: Mon -Fri 10am-5pmCommunications Equipment for the

Professional and EnthusiastCallers by appointment only

W. MIDLANDS

DEWSBURY ELECTRONICS --®-

176 Lower High St, STOURBRIDGETel: 10384) 390063

Open: 9.30-5.15. Closed Thurs. & Sun.ACCESS/ BARCLAYCARD

HEWARD'S HOMESTORES LTD. (Est. 1983)822/4 KIngstanding Rd., Birmingham

B44 9RT. Tel. 021-354 2083G4RJM with 38 years in The Radio Trade

Ham Equipment urgently wanted!Open: Mon -Sat 9-8

NORFOLK

Please include my business details in the next available issue of Ham Radio Today

it 000stAddress:

SI1Tel. No.

Open Hrs:

Contact (Office Use Only):

Business Name:

Post to: Emporium Guide, Ham Radio Today, 145 Charing Cross Rd., London WC2H OEEL-.

70

- -IHAM RADIO TODAY AUGUST 1983

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D.P. HOBBS (Norwich) Ltd13 St. Benedicts Street, Norwich

Tel: 615786Open Mon -Sat 9-5.30

Closed ThursStockists of:

YAESU, FDK, ICOM, JAYBEAM& Electronic Component Specialists

NOTTINGHAMSHIRER.A.S. (NOTTINGHAM

P Owen GBUUS3 FARNDON GREEN. WOLLATON PARK

NOTTINGHAM: TEL 0602 280257open. Tues-Fri 10-530 Set 9 5

YAWL: MK: ICOM: 11104IMERKAIIM! TOONASUUJIAR: WELL ANTENNAS le OWN EIRW14.F.

SCOTLAND

AXDON32 Atholl Street, Perth

Tel. 0738-23753. Open: 6 daysICOM, TONA, TONO RSGB Books, Maps 8.

log books. Full range of componentsMa:l order aya,lable - send for once Its!

r -

JAYCEE ELECTRONICS rrogiair

JOHN GM3OPW20 Woodside Way. Glenrothes. Fife KY7 60F

Tel: 0682 766662Open Tues- Sat 9-5

Ouains secondhand equipment ,11 stock Full tangs of TRIOgoodies Jaybearr - Petcrowsve Nodules - LAR

SOMERSET

AVCOMM LTD25 Northload Street,

GlastonburyTel: 0458-33145

Open 9.30-5.30. Closed Wed

SUSSEXscxcx""Dc's 40 TERMINUS RD (opp.

EASTBOURNE RailwayTel: (03231 633361 Stn.)

Open: Mon -Sat 10-6 (Closed Toes)Stockists of: Yaesu, Trio, Tonna, FDK etc +secondhand and es -Government equipment In

stock

R13,0110

TYNE Et WEAR

PLYtTh0 bi ICSICOK. haat

129 Chillingham Rd, Newcastle-upon-TyneTel: 0632 761002

Open: Tues-Sat 10am-6pm

YORKSHIRE4 Cross Church St, Huddersfield Tel:

Open 6 days 9 5.30 04114 20774Closed Weds. Thurs 9arn-8om

G4MH Mini BeamAirways a good Alecto", of new 6 2nd nand equipment on stoat'

Amateur Radio Shop

DISCOVER THE WORLD 471714 AMATEUR RACI10 FROMI re S2 1(.

LEEDS 452657 Off M was- sarIA. MOriSSIOMALS. h see

TRIO ICOM YAESUI 5505 11.1 ON RC.) MAO OPDlp4LiRVN. I DIM OPEN MON -0,1bo !?4 40..1 Poti,,00L . 4.22. !loo. -5,.EIF1111111-1 MADE En- LAP PRODUCTS

- sees IMMO ilissis ems mos earns 1116110 - sum-

HAM RADIO TODAYCLASSIFIED ADVERTISEMENT - ORDER FORM

Rates of charge: 30p per word per issue (minimum of 15 words).and post to HAM RADIO TODAY, CLASSIFIED DEPT.,

Advertise nationally In these columns to over 60,000 readers foronly 30p per word (minimum charge 15 words). Simply print yourmessage in the coupon and send with your cheque or postal ordermade payable to Argus Specialist Publications Ltd. to:CLASSIFIED DEPT. HAM RADIO TODAY145 Charing Cross Rd, London WC2H OEE.Tel. 01437 1002Please indicate classification required.

NameAddress

Tel.No.IDay)IPlease place my advert In Ham Radio Today for 0 months. Please Indicate number of Insertions required.

OR Debit my Access/Barclaycard(Delete as necessary)

.11

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HAM RADIO TODAY AUGUST 1983 71

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HAM RADIO TODAY CLASSIFIEDLineage:30p per word (minimum 15 words)Semi Display: (minimum 2 cms)£5.50 per single column centimetreRing for information on series bookings/discountsAll advertisements in this section must be prepaid.Advertisements are accepted subject to the terms andconditions printed on the advertisement rate card (available on

EQUIPMENT

IK-1 CMOSNMOS Iambic keyer. An electronic morse keyer with sidetone andinternal PP3 battery. VMOS technology allows our keyer to key the rigs other

keyers cannot! Positive or negative versions.£19.95 & 50p P&P

MPA-2 144MHz Masthead preamplifier. Our advance design with selectivehelical filter can switch up to 500W pep.Ideal for DX or Contest WorkCmos morse practice oscillatorPiptone/Roger bleepK bleep £6.00 & 25p p&pOur CM1000 HF Transceiver is currently under development. Send SAE or phone

for information on this and our other products.Please note 1 2 months guarantee on all our products.

CHRIS MOULDING RADIO SERVICES, 276 HULTON LANE, BOLTON,BL3 4LE 0204-651348

£33.50 & 50p p&p£6.50 & 50p p&pE4.50 & 25p p&p

.N.O.S.

Manufacturers of PowerSupply Units and V.H.F

linear amplifiers.B.N.O.S. Electronics

Dept. HRTC, Greenarbour.Duton Hill Gt. Dunmow,

Essex CM6 3PTTel: (037 184)767

AMATEUR RADIO EQUIPMENTToggle switches, cables, test metersetc. Send s.a.e for price list to M.J.Seaward, 7 St. Olafs Road StrattonNr. Bude, Cornwall EX23 9AF Tel(0288 4179).

G40GP ELECTRONICS

116 Darlington Street East,Wigan.

Tel. 0695 27948Or 0942 497609

Antennas, G5RV's, HF & VHFAerials, Transceivers, Baluns,Antenna Tuning Units made toorder, and of course G40GP's300-600 ohm Feeder Spacer.Unique clip -on Feeder Spacer.

73'sTONY AND JACK

G40GP G3LRB

Special prices on surplus equipmentRacal RA17 Receivers High grade communications receivers 500KHz-30M1-12in 30 effective bands. From £175. Eddystone receiver 730/4 500K1-12-30MHz in 5bands £145. All in excellent condition. Can £15.

Avo valve testers £30 p&p £4. NEW 28 range digital multimetens £40.25.PCR Receivers LW/MW/SW Untested less PSU £20 p&p £5. 12' Whip aerials£4 p&p £1.50. Creed teleprinters £25 p&p tree. Various single and doublebeam oscilloscopes, signal generators, valve testers, output meters etc alwaysin stock.

Surplus circuits Book containing circuits and notes on many surplus receivers,transceivers etc. £6.50. Send 50p for illustrated catalogue includes £1voucher. Over 500 sets in stock. Avos amateur rigs WANTED for cash.

New shop open at 218 St Albans Road.Come and see the bargains

WEIRMEAD LIMITED, i?q St Albans Road. Watford Hells

elephone Watford 194ib Access Visa cards welcome.

TYRONE AMATEUR ELECTRONICS44 High St., Omagh, Co. Tyrone, N. Ireland

Day Telephone No. 0662-2043Evening Telephone No. 0662-2922

Full range of YAESU, ICOM, HIGH GAIN, CDR etc in stock.VERY KEEN PRICESExamples:ICOM IC720A £949 including FREE PS15.YAESU FT230R. Our price £199.00.HIGH GAIN TH3MKIII. Our price £225.00.CDR HAMIV £258. Special price £218.Call us and ask for Billy or Fereal for prices andavailability.Finance can be arranged.Also VISA accepted.

request)

01-437 1002EXT 204Send your requirements to:Julie Bates,ASP Ltd.,145 Charing Cross Road,London WC2H OEF

G.W.M. RADIO LTD. 40/42Portland Road. Worthing,Sussex. Stockists of ham radioequipment. Tel: Worthing(0903) 34897.

AERIAL PARTS14 swg Hard Drawn Copper AerialWire 20p per m (post 2'r p per m),Strong PVC covered stranded AerialWire 6p per m (post 21/2p per m);300 ohm Twin Ribbon Feeder 12pper m (post 2p per m); 75 ohm TwinFeeder 18p per m (post 2p per m);UR43 50 ohm COAX 20p per(post3p per m); UR70 50 ohm COAX 20pper m (post 3p per m); UR67 50 ohmLOW LOSS COAX 50p per m (post

5p per m)W.H.WEST LAKE, G8MWWClawton, Holsworthy, Devon.

TRANSMITTERS RECEIVERS ETC.All frequencies. weil known makes,ICOM, YAESU MUSEN, FDK, AZDEN,LOWE,STANDARD,etc. etc. Powersup-plies, wave -meters. test meters, fre-quency counters, Welz SWR and Powermeters. Microwave modules, linearamps, RTTY etc. Quality equipment foram-ateur, PMR and Marine use. Aerials,Co -ax cable, plugs. See our advertunder Emporium Guide. £1000 IN-STANT HP available and ACCESS -Booth Holdings Bath, 6 Golf Club Lane,Saltford, Bristol BS183AA. Tel (02217)2402. Staff includes G3N XW, G3XOD,G8DPH.

ALL AMATEUR AND CB NEEDSICOM, TRIO and YAESU. CYBERNET

HARBARD and UNIDEN.TAGRA,G.WHIP, HOXIN, MICRODOT

RTTY. SWR & power meters.Receivers & linears. Plus all other

accessoriesAerial Fitting Service

231 Chorley Rd.. Swinton,Greater Manchester.

Tel: 061-793-1010

READERS SEARCH OURCOLUMNS TO BUY YOUR

PRODUCTSPHONE

01 437 1002NOW!

SOFTWARE

ZX81 or SPECTRUM-G4RWTMorse Tutor +

Sattrack ProgramComplete morse course frombeginner to operator. Features 1000WORDS, random groups, punctua-tion and text input. 4-20 WPM.Detailed notes. Interface circuit dia-gram to Autokey your rig. Plus Satel-lite Tracking Oscar 8 and uosat.Amazing value £4.50 per cassette L.G4RWT Amateur Radio Software,68 Forest Road, Paddock Wood,Kent or tel. 089283-2590 withAccess/Barclaycard.Specify ZX81 or Spectrum. Also avail-able from Amtronics, CO Centre.Enfield Emporium, Lee Electronics.Waters & Stanton, etc. Trade en-quiries welcome.

BBC MICRO SOFTWARESophisticated morse -teacher slow morse broadcastsystem morse beacon RTTYtransceive system. Comingshortly. Morse QS° transmitand receive, meteor scatter at300 wpm, contest scoring pac-kage. Written by professional

Sendlarge SAE for detailed techni-cal specifications. GOC Soft-ware, 47 Cranberry Lane,Alsager, Stoke-on-Trent.

PUBLICATIONS

AVIATION FREQUENCIESThroughout Europe

As used by BA and other majorAirlines

284 Pages £6.25 inc p&pOrder by phone. Access and

Visa welcome.Other lists available.

AOS (HRT) West LondonBuilding,

White Waltham Aerodrome.Maidenhead SL6 3NJTel: (0628 82) 5362

AIRCRAFT COMMUNICATIONS HANDBOOK (UK/Europe) including spot MF, HF,VHF, UHF frequencies, military& civil airports, air traffic controlcentres, long range stations,meteorological broadcasts,broadcast times, navigationbeacons, co-ordinates, call -signs, maps, etc. £7.50. p/p £1.PLH Electronics, 70 Vallis Road,Frome, Somerset, BA1 1 3EJ.

FOR ALL YOUR CLASSIFIEDREQUIREMENTS PHONE

ASP LTD.01-437 1002

72 HAM RADIO TODAY AUGUST 1983

Page 73: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

ANTENNA

AMTROnICf ,TONBRIDOt

NEW AMATEUR RADIO SPECIALIST IN KENT

BUY BRITISH IN JULYJAYBEAM appointed dealer.H.F. 4m, 2 m, 70cm, 23 cm OMNI. Beams, lashings and domestic T.V. antennas. Full range in stock.B.N.O.S. appointed dealer6amp, 12 amp, 25 amp, 40 amp P.S.U.'s 1/100, 3/100, 10/100 linears.FORTOP appointed dealer70 cm TV -UP Convertor, Video Demodulator, TV TX, TV TX/TR, 3/20w linear. 300Mw/20w linear.DRAE appointed dealerV.H.F. wave meter, Morse tutor, 4 amp, 6 amp, 12 amp, 24 amp P.S.U.'s. DC convertor.ZENITHSpeech Processor. 29MHz LCL FM mobile 29.310 to 29.700 in 10kc steps with 100kc repeater shift. 5w output. £55.

APPOINTED AGENTS FORFDK., AZDEN, ICOM, DATONG, ADONIS, WELZ, R.S.G.B. BOOKS.

Come in and see what we have to offer. Open to 7 pm Friday Closed MondayFINANCE AVAILABLE WRITE FOR DETAILS

Spend £20 or more on British madegoods and get a FREE Station Log.--

Ng.

8 TOLLGATE BUILDINGS. HADLOW ROAD. TONBRIDGE. Telephone: Tonbridge (0732) 361850

RESTRICTED SPACE HF OTH's

A G2DYM UNI-POLEWILL BE YOUR ANSWER, TX

OR SWLDATA SHEETS LARGE SAE,

AERIAL GUIDE 75pCallers WelcomeTel: 03986-215

G2DYM,UPLOWMAN

TIVERTON, DEVON

FOR ALL YOURCLASSIFIED

REQUIREMENTSPHONE

ASP LTD01 437 1002 extn 204

30 FOOT STEEL and alloy maststillover £100 For details P.O. Box16, Redruth, Cornwall.

ANTENNES TONNA (F9FT)YOUR NUMBER ONE CHOICE FOR 8m, 2m, 70, 24 & 23cm ANTENNAS

50MHz5 element'144MHz4 element9 element fixed9 element portable9 element crossed'13 element portable'NEW 17 element fixed435MHz19 element19 element crossed'21 element 432MHz21 element All/144/436MHzOscar Special9 & 19 element

01.741.1

E13.011.1£15.441e)f17.461e)£28.521e)r27.21Ie)£36.19(a)

E18.141e)1:30.061a)I:26.001a)1:26.001e)

00.0151a)

1260MHz or 1295MHz23 element' 125.901b)4 x 23 element antennas - power splitter - stackingframe £140.001.1Telescopic Portable Masts4x 1m E15.984a) 3x 2m 019.151e14 x 2m E28.754a)ANDREW HEUAX LDF4-50 COAXIAL CABLEAttenuation per 100ft 144MHz - 0.8dB435MHz - 1.6013. 1296MHz - 2.9dBE320 per metretal 'N' type connectors for LDF4-50male or female (10.36

MICROWAVE MODULES - ROTATORS --COAXIAL CABLES ETC.POWER SPLITTERS AVAILABLE FOR 2' OR 4ANTENNAS

Denotes 500 ONLY - all others 500 OR 750PLEASE ADD CARRIAGE AS SHOWN le) E4.00; Ib) £1.80.

Terms:Cash with order, ACCESS - VISA - telephone your card number.ALL PRICESINCLUDE VAT AT 15%. For full specification of our range send 30p for Catalogue.

Callers welcome, but by telephone appointment only please.

RANDAM ELECTRONICS (H)12 CONDUIT ROAD, ABINGDON. OXON 0X14 1DB. Tel: 102351 23380 124 hours)

FOR SALE

LIST -A -RIGThe daily advertiser for all amateur radio enthusiasts.Foryourfree copy simply send two first class postagestamps to List -A -Rig (HR), 65 Cecil Avenue,Hornchurch, Essex.

G3 RCQ ELECTRONICSAmateur radio equipment bought, sold, exchanged.Tel: Hornchurch 55733, evenings 6/9 pm andweekends.

2 METER SSB Transceiversfrom £138. Full range includ-ing ICOM, TRIO, YAESU,ASDEN, ETC. Credit facilities.Guilford CB, 0483 574434

CREED 444 TELEPRINTERSwith tape reader and writers. Alltested and working order.Excellent condition from £45.A.J.H. Electronics, 20 BarbyLane, Hillmorton, Rugby, War-wickshire. (0788) 71066.

VALVES VALVES VALVESThe following valves in matched pairs 6JS6/C 6KD6, 6JB6/A6HF5 6146A 61468 YES the 6JS6/C is Japanese and works inthe FT101. Most amateur radio valves including difficult toobtain EX STOCK. Quotations without obligation. If we don'tstock yourtype we may be able to import for you. Please enquire.Remember, over 200 types EX STOCK. Phone for assistance retypes suitable for your equipment. USA and Jap manufacture ofpopular types available.Don't Delay Phone Today 045756114 G4A2M. Free Postagewith this advertisement.Wilson Peel Cottage, Lees Road, Mossley, Tameside, Man-chester.

Ant Products, All SaintsIndustrial Estate, Baghill Lane,

Pontefract, West Yorkshire.Telephone 0977 700949

AMATEUR ANTENNASilver 70-70 cms 16dbdGain Beam C31.95Tiger LYE 9 dbd2 Meter Beam C12.95Tiger LY8 11 dbd2 Meter Beam 019.50Tiger LY10 14 dbd2 Meter Beam C32.95

TWO YEAR GUARANTEE ON ABOVEZL12 Mk 2 13 dbdGain Beam Antenna £32.95ZL8 Mk'2 9 dbdGain 5* -7" Long Boom £19.95ALL ABOVE HAVE STAINLESS STEEL

PARASITIC ELEMENTSNorcone 512 Wide BandDiscone Antenna £25.95Securicor Delivery(Extra) C4.50Send cheque or money order today,made payable to Ant Products or write

enclosing SAE. for full details.

COMPON ENTS

FROM £1 EACH. Synchros,servo -motors, tachogenera-tors, shaft encoders, etc;unused ex. admiralty. S.A.E.Hartshurst Farm, Ockley,Surrey.

NEW COMPONENTSAT LOW PRICES

CONNECTORS D TYPEPlug 9W/75p: 15W/C1.00: 25 W/£1 .50Skt 9W/81.00; 15W/81 .45; 25W/E1.90Covers 9W/15/W/85p; 25W/90pCONNECTORS COAXIALPL259(RG581/45p, PL259(RG8)/40p;Reducer/10p; Coupler (F+F)/50p:Elbow/95p; S0239/40p:TEE (M -2F or 3F)/£1.10UN EARS709/35p; 747/35p; TDA2002V/E1 .25TRANSISTORS13E981/81.00: BFR91 (replacesBFR34A)/81.40; BC212/8p. BFY50/15p: 8F509/15p; BF274/15p; 2N5179(Low Noise 1GHz)/25p; 2N3055/50pCAPACITORS DISC100pf/750V; .01 of /250V; .05uf/101/,0.1u1/10V All 5p. 1000pf/750V/10p:.01u1/3kV/20p

P&P 50p (free over E8)SYON TRADING (Dept HR1)

18 The Ridgeway, Fetcham,Leatherhead, Surrey KT22 9AZ

Mail order address only

EXHIBITIONS

SUSSEX MOBILE RALLY. Aday by the sea with the familyfor £1. Brighton Raceground.17th July. 10.30 am - 5.00 pm.Free Car Parking. Good cater-ing undercover.

AERIAL WIRE Hard Drawn Cop-per 140ft 14SWG £6.90, 50 met-res 16 SWG £5.90 includingpostage. S.M. Tatham, 1 OrchardWay Fontwell, Arundel!, WestSussex.

SURPLUSEx M.O.D. radio, electronic, andelec. equip. etc. Send 2 x 16pstamps for list 31. A.H. Supplies(Dept 3), 122 Handsworth Road,Sheffield S9 4AE.

COPPER AERIAL WIRE 14 swghard drawn, 70' coils, £5.50, 140'£8.90 inc postage. T.M.P. Elec-tronic Supplies, Unit 27, PinfoldWorkshops, Pinfold Lane, Buc-kley, Clwyd, N. Wales SH7 3PLTelephone: Buckley (0244)549563

Whatever youare selling.Do it quicklyand cheaply

Phone ASPClassified01-437 1002

HAM RADIO TODAY AUGUST 1983 73

Page 74: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

KITS WANTED CLUBS

WOOD & DOUGLASNEW PRODUCTS for the new exhibition season

from our new factory facility

144LI N25B 25W VHF LINEAR -A single stage higher power ver-sion of our popular 144LIN1OB designed for the 2-3W output levelFM or SSB equipments. The board retains the straight through modein receive or when the power supply is disconnected and fits neatlyinto a small diecast box. Ideal for the FT290.Price details: £29.95 in kit : £40.25 as an assembled module.6RX2 6M CONVERTER - You may not be one of the privileged 40but you can at least listen on this compact high performance conver-ter for 6M. It allows reception on the 2M band. The board has optionsfor local oscillator output and r.f. gain adjustment.Price details: £19.95 in kit : £27.60 as an assembled module.MPA2 MICROPHONE PRE-AMLIFIER -A buffered output ver-sion of the MPA1. The board will now interface with low inputimpedence equipment without degrading the response.Price details: £3.45 in kit : £5.95 as an assembled module.TVMOD1 Ch 36 MODULATOR - An alternative imported UHFmodulators giving adjustable frequency over the range 400 to 600MHz. This enables system checks at 70 cms or directly into your TVset in Band IV. The board has video gain and modulation presetadjustable. The output oscillator runs at 200-300 MHz so it could beadapted to Band III.Price details: £6.95 In kit form : £10.15 as an assembled module.

When you purchase one of our products you are guaranteed successbecause we offer full back up and servicing on any item no matternow small. The confidence we have in the product is reflected in therange available and the low service return rate incurred.Why not try a kit today? We accept credit cards or written orders directto our industrial premises or at rallies and exhibitions throughout theseason. Enjoy your hobby more by building your next rig oraccessory.

UNIT 13YOUNG INDUSTRIAL ESTATEALDERMASTONREADING RG7 4130.TELEPHONE: (07356) 5324.

106321761002

ICOM

IC -720A

APPROVEDqt, DEALER

ONICSC v7

06321761002

YAESU

IC -251E

Approved 'TONNA' stockist -Licensed credit brokers- also -

Microwave Modules - I.C.S. - A.E.A. - Datong - Tasco -CDE - Daiwa - Hansen - TAL - Tono -G -whip HF antennas -

Dummy Loads - Coaxial switches - plugs - sockets

RF cables - H-100, URM67, URM43, URM76, 3000 ribbon,5 core, 6 core, and 8 core cable

129 Chillingham RoadNewcastle-upon-Tyne

Open Tues-Sat 10am to 6pm

BARCLAYCARD

WANTEDAll types of marine, electronic, radioand radar equipment. The MarineElectronic Co. Ltd., 1-4 Swan Mead.London SE1 4SY. Tel: 01-237-3474.Open Mon -Fri. 10am-5pm. Callers byappointment only.

HAM EQUIPMENT URGENT-LY WANTED! Heward's HomeStores Ltd (est. 1963). 822/4Kingstanding Rd., BirminghamB44 9RT. Tel: 021-354-2083.G4RJM.

FREE RADIOWhat has happened to Radio Caroline?What is the latest on the Irish piratestations? How did the Voice of Peace sur-vive the recent storms? Subscribe to ourmagazine to find out. Send £3 toCaroline Movement, Dept. B,BCM-BRFM, London, WC1.

RTTY TERMINALSRTTY TERMINAL BOARDS.TTL output for computer £35incl. and for teleprinter £39 incl.All boards come completelywired and tested with FSK andAFSK. S.A.E. for details toB. Brookes Electronics, 2Leicester Street, Norwich.Tel: (0603) 24573.

CARDS, STICKERS, BADGES

QSL CARDS printed at keenprices. Send stamp for sam-ples. Sigmaprint, 62 NewarkLane, Ripley, Surrey.

LISTENER & QSL CARDSQuality printing on Coloured andWhite Gloss Card at competitveprices. SAE for samples S.M.Tatham "Woodside", OrchardWay, Fontwell, Arundell, WestSussex.

CALL SIGN LABEL BADGESprofessionally engraved, by re-turn of post. £1.50 cash withorder (state name & call sign)Aylmer -Kelly - H, 2 PickwickRoad, CORSHAM, Wilts., SN139BJ.

COURSES

COURSES RADIO AMATEURSEXAMINATION City & Guilds.Pass this important examinationand obtain your licence, with anyRRC Home Study Course. Fordetails of this and other courses(GCE, professional examination,etc.) write or phone - THE RAPIDRESULTS COLLEGE, Dept. JX1,Tuition House, London SW1.9 4DS.Tel: 10-947 7272 (gam-5pm) oruse our 24 hr Recordacall Service:01-946 1102 quoting Dept. JX2.

MORSE CODE REPARATIONReceiving: Cassette A: 1-12wpm for amateur radio examina-tion. Cassette B: 12-25 wpm forprofessional examination pre-paration. Each cassette is typeC90. Price each cassette (in-cluding booklets) £4.75. Send-ing: Morse key with separatebattery (PP3) - driven solid-stateoscillator and sound transducerproduces clear tone for sendingpractice. Price of key with oscil-lator £10.50. Prices include pos-tage etc. Europe only. MH Elec-tronics (Dept. H), 12, LongshoreWay. Milton, Portsmouth PO48LS.

ENGRAVED LAPEL BADGESLepel badges with electrically weldedSafety clip, most colours available,Example: Club Badge, club name, per-sonal name, callsign, with or withoutRSGB logo - 1 to 10 badges 85peach. 10 and above 80p each inc P&P.Please use block capitals tor all orders,cash with order, orders dispatched byreturn first class post.Club Secretaries please send for sample

DARFIELD ENGRAVING SERVICES39 Cliff Road, Darfield, Barnsley,

S. Yorks S73 9HRTel: Barnsley (0226) 752106

QSL CARDS printed to yourown designs on white orcoloured gloss cards. Send forsamples, The Nutley Press, 21Holme Thorpe Avenue, Redhill,Surrey, RH1 2NB.

NEW!! Scientifically preparedfive-day courses to get youthrough the R.A.E. examina-tion: 01-346-8597.

Componentsto sell?

Phone ASPClassified

01-437-1002ext. 204

HAM RADIO TODAY -AUGUST 1983 ADVERTISERS INDEX

Allweld 42 Intermedial 44 P.M. Electronics 37Amcomm IBC KW Electronics 50 Polemark 33Arrow 8 McMichael Ltd 33 S.M.C. 38, 39BNRS 54 Meta lfayre 54 Walters & Stanton 61C.Q. Centre 21 021 IFC, 24, OBC Wescom 44Fortop 33 P.M. Components 30 W.P.O. 42

74 HAM RADIO TODAY AUGUST 1983

Page 75: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

airsmi//////////1/11111111 1111111111111111111111 11111111111111111M

MI/111111111111M 1111111111111111111111 1111111111111111111111111 Iiiiit1111111111111111-1111111111111111111

1111111111111111111111 11111111111111111;11

/Amcomm Peopleare at

the other end.

Who do you talk to when youcall Amcomm? Usually Jack G3LNC or _Alec G5VS. Whoever it is, you'll be speaking to pleasantand reliable people with years of operating experience on theamateur bands. People with an intense and active interest ineverything to do with Amateur Radio. People who actuallyoperate 365 days every year. People who quickly and efficientlyimpart the information you need to make your decisions.

Just listen or ask around the bands - the reputation we havegained was built by people like you. People who have triedAmcomm and stayed Amcomm.

You see, we understand Amateur Radio, we live it at work andplay - but most important of all - we understand Amateur RadioPeople.

Call us today and ask about our 70 major amateur names whichmake up over 500 different lines or send 50p. in stamps for ourBumper Literature Pack. (You'll find enough reading for days!)

You'll certainly like the peopleat the other end...

AUTHORISEDAmcomm People. ww.YAESU

Amcomm Services,194, Northolt Road, South Harrow,Middlesex HAO 2EN.Telephone: 01-422 9585 (3 lines).Telex: 24263.

Page 76: VHF to HF transverter - worldradiohistory.com › Archive-DX › Ham-Radio-Today › 80s › … · AN ARGUS SPECIALIST PUBLICATION VHF to HF transverter Use your 2m multimea ot transceiver

A new rano of antennas

mdyst

the best.

r those lithomu have

Ask for themat your localamateur radioshop


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