Monthly Archives: September 2000

JAMBOREE-ON-THE-AIR and JAMBOREE-ON-THE-INTERNET. 21st/22nd OCTOBER 2000

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RADIO SCOUTING
by Dave Gemmell and the Broomstick Warriors

JAMBOREE-ON-THE-AIR and JAMBOREE-ON-THE-INTERNET.
21st/22nd OCTOBER 2000
Hopefully most of you, Dear Readers, will read this Column before the first JOTA of this new millenium. If you are helping a the Guides or Scouts to run a station please remember that this an event when the young should be doing most of the communicating so please set up each contact as soon as possible. Then get as many boys and girls to “talk on the air” as possible. I have said this before but it’s a bit irritating when you’ve listened to some station you want to contact going on for about 5 or 10 minutes about something or other only to have him repeat the same thing when you eventually do get hold of him. Be very careful as both JOTA and JOTI are important Public Relation events for both Hams and the Guiding and Scouting Movements.
Having said this please remember the age and ability of those with whom you will be dealing. The children are at the stage when they want to try everything for themselves so it is a good time to introduce them to morse. Now before you “scream blue murder” let me add that CW is simple and is an ideal way to introduce an interested person to modulation. When keying a transmitter you are actually moving from 0% to 100% modulation. Secondly anyone can try this for themselves using a whistle or a flash light. So you may have a situation where the learner moves from being slightly to very interested in Ham Radio. This would be a good time to get if the Scout Group you are helping to enter the JOTA Low Power Contest. Perhaps you could build a few QRP transmitters of the single transistor.
Answer any question or query regarding CW positively. Please don’t “condemn” or ridicule morse as this may, strangely enough, only have a negative effect and cause the “inquirer” to take his/her interest else where. You should, however, mention that CW is used to send short messages and is ideal for use in emergencies.
Everything I’ve said about the use of CW can also be applied to construction. Children seem to be interested in everything so show how easy it is to build a simple oscillator. Then have them determine the greatest distance that can be achieved between them and your commercial rig.
If I have repeated myself for the millionth time in this column I still make no apology as these days it seems that despite modern technology there many people, Hams, Guides and Scouts who still do not know the basic principles of their own movements and how to achieve maximum benefit from them.
Please send in your JOTA reports to your local Scout Area Commissioner or JOTA Co-ordinator before the end of November 2000 as the National Report for South Africa must be sent to Geneva before the end of the year. If you aren’t sure who these people are please send them to me at the address below.

If you can, I’m sure Ray Webber ZS6RSW won’t mind you using his e-mail address to send me your contributions to this Column or JOTA/JOTI reports.
My postal address is, as usual, P.O.BOX 77, IRENE 0062. Many Thanks.

THE QRP COLUMN OCTOBER 2000

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      QRP
THE ------- COLUMN OCTOBER 2000
     80/40

by Dave Gemmell and
the Low Power Bunch
This Column is being typed /compiled on a my daughter-in-law’s computer and e-mailed to our illustrious Editor Wolfy. Yes, occasionally I do make use of home labour-saving devices but what makes this task more pleasurable is that merely turning my head I can see a nice rural setting (horses and cows grazing the grass in Surrey) from the window of my son’ s computer room.
When planning this holiday some months ago I decided to “design/build” a QRP transceiver to take along. Now that SA is a member of CEPT I reckoned that it would be a “chinch” to get on the air! I built the transceiver but didn’t take it, mainly because it was built into a plastic sandwich box and might have looked, to those uneducated in matters electronic, like a bomb or what have you! It did occur to me that my XYL and I would be passing though at least four custom check points and trying to explain the joys of low power operation didn’t really appeal to me. Especially after spending an almost sleepless night with some 350 or so happy fellow travellers!
Now let’s look on the bright side!!! The next time I’m going to build a QRP rig to fit in the top pocket of my jacket!
There was quite a lot to be learnt from this exercise! Getting the parts together, building this rig and getting it to work, was fun in itself. The circuit I used is an old favourite of mine. Who knows, maybe I will be able to publish the circuit diagram in the next issue of RADIO-ZS! You should be able to draw your own circuit from the following description.
Choice of RF “power” transistor 2N1711 type as well which one operated the best. In fact, I used a socket for the “PA” power transistor this made it easier to select the best transistor for the job. It was amazing to find out the variation in the value of the power delivered by the thirty or so 2N1711’s in my “junk box”. Don’t forget to use a heatsink or you might burn out your entire stock of your transistors! A lot of similar transistors seem to be able to with-stand over heating for a short time but not so the 2N1711!
A 2N2222 was used for the oscillator to drive the power amplifier as well as the receiver’s diode mixer. The receiver RF amplifier was built around a BF115 which was followed by a double diode mixer the output of which is connected to a two stage directly coupled AF amplifier which gives enough gain and power to drive high impedance earphones. I tried to use the common collector circuit mentioned in a previous column be have no time to iron out some silly problem which cropped up.
Deciding what antenna to use was not without it’s “points of interest”. For the same customs and excise reasons plus the luggage weight limit set by the airline conpany, I wasn’t going to take a wire dipole and coax along so I was going to buy suitably priced copper wire at the nearest hardware shop and use ordinary table lamp “rip-cord” for the feeder line. I had been led to believe that this “rip-cord” had a characteristic impedance, Zo of 75 ohm but I thought I’d calculate it just the same using the formula Zo = 276 logD/d. After a few measurements and calculations, I ended up with the figure 230 ohms. Then I tried measuring the “rip-cord’s” Zo and obtained 120 ohms ???? If this type of cord was used irrespective of the value of Zo the output impedance of the transmitter could be adjusted to suit by varying the values of the capacitors in the Pi-coupler. The main problem is coupling to the antenna. I though of the windom fed with 300 ohm tape. So why not connect the feeder at a point where the impedance matched that of the “rip-cord”. This idea will definitely be investigated at the earliest opportunity.
Deciding what other accessories to take or not to take along was a very interesting exercise. The power requirements are 12 volt , receive cut about 30 mA and transmit current about 500 mA depending on the RF power transistor used. Normally a rechargable 12 volt battery, could be dry cells but these turned out to be a very expensive alternative if bought in the UK. Using a mains power supply seems to be the logical answer but its going to take a bit of experimenting to get something light in weight. Anyway I have a year or three to do something about this.
I have since learnt that if a South African Ham is staying in the UK for less than 3 months he/she may operate on the amateur bands without special permission or any payment. This situation changes when the stay is longer than 3 months when the SA Ham must apply in writing for a special licence which will be granted on payment of £15-00. (About R155-00 at the present current rate of exchange.)
How to call on the ham bands is laid out concisely in booklet BR 68, page 14, section 10(2):-
CEPT Amateurs shall transmit their home callsign after;
a)the United Kingdom callsign prefix “M”;
b)followed by the appropriate Regional Secondary Locator (if any); and
c)followed by the symbol “I”.
So if yours truly was operating from Scotland I would have to use MMI/ZS6AAW but from Wales it would be MWI/ZS6AAW or Northern Ireland MII/ZS6AAW. The regulations when operating anywhere in the UK seem to be almost the same as in SA but check first the Licence Requirements BR 68 which can be obtained from the UK Radio Communications Agency. It may be a good idea to check for any subtle changes before you start operating there. Secondly check with the relevant authorities about correct procedure to getting your equipment, home brew or commercial, through customs at each end of the route.

Here’s hoping the usual contributions from the QRP Bunch, the Radio Scouts (and Guides !) plus the Museum News have survived their trip down the digital tubes of
e-mail! But, seriously chaps, this Column (and others!) seriously need news and contributions from you the Reader. Please, please send in any item of low power news. It doesn’t matter how small. Even a sentence or two on the back of a post card can be a BIG help! The address is as usual – P.O.Box 77, Irene, 0062.

MUSEUM NEWS. October 2000 by a Staff Reporter.

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There’s not much to report in the radio side of the museum scene but Dave ZS6AAW visited a number of places on a recent visit to the UK . Unfortunately most of the visits to these places of interest were “rapid” and I wasn’t able to find anyone who could tell me if there were any hams associated with the various museums. So as time is few, please excuse me if I ramble on a bit about aircraft, factories and castles. Then they do give you ideas of where and how special event stations could be set up. There should be comparable places in South Africa something like those set up for the International Light House Event held not so long ago.

VISIT TO THE NORTH.
On trip to the north of Scotland, at the towns of Findhorn and Lossiemouth which are two RAF Air Bases , Nimrod recce planes are stationed at the former whilst Tornado fighters are at the latter. The fascinating thing about the Nimrods is that their wings seem to have been taken straight of the Comet airliner of the late 1950,s! No mistaking the two squarish/oval air intake “holes” on each wing close to the fuselage. These aircraft came flying over from time to time and it is quite fascinating to see 3 or 4 Nimrods doing “circuits and bumps” usually in SA we only see one large aircraft at a time! Being operational airbases I couldn’t arrange a visit at all so the nearest thing in the radio line to be seen were 3 large masts which were obviously the local long wave DF station or Non-Directional Beacon (NDB).

THE CASTLE ON DUMBARTON ROCK.
The reason why I mentioned the visit is that it is just another example of aviation history and places of interest which could pass unnoticed if one was #unobservant#
These occasions seem to occur at times in the most unlikely of places. On climbing to the top of the rock (about 200 metres high) one reaches a viewing platform which has notices giving the history of various places of interest below. The most interesting was the building which housed the factory where about 280 Sunderland flying boats built during WW2. It is now a ware house for the local whisky distillery. The last time this Rock was used “in anger” was also during WW2 when an anti-aircraft battery was stationed there but there is no trace of these installations. During the same war in May 1941 the Rock was struck by high-explosive bombs the first enemy attack on the castle in nearly 300 years.

AIRFIELD AT EAST FORTUNE.

If a friend had not mentioned its existence I would not have been able to visit this WW2 airfield right in the middle of the farming area. One of many airfields which dotted the English and Scottish country sides during WW2 and seem to be tucked away amongst the wheat and barley fields. This Museum is also the home of an Comet airliner and a Vulcan bomber. There were only two display hangars which were crambed with aircraft. There was a display of radio equipment but it was not in working condition.
One thing, apart from the many aircraft that were on display, was a piece of aircraft fuel pump and a R1155 receiver with a notice on top saying “Please Touch” obviously put there for those people, young or old who were just eager to put their hands on something! Quite a good idea I thought!
Then, this seems to be the general idea about most of the museums in the UK that there has to be something which can be “played with” or touched. In a lot of the cases it a sturdy model which illustrates a principle or two. Perhaps we can learn something from this and put it into practice.

 
MW, LW, AND VLW?
Yes! You have read correctly! Medium wave, long wave and very long wave. These terms haven’t been used in Ham circles for some time so what better place to mention them but here in the Museum Column.
Medium wave, 550 – 1600 kHz, is used in SA as well as the UK for broadcast purposes. I have counted about 12 stations this morning, mostly English but there were 4 French and 1 Chinese, which must be local in the London area. On the very long wave band, 150 – 250 kHz, there were 7 stations. I was unable to monitor the 250 – 450 kHz due to the lack of a suitable receiver but I strongly suspect that it should be the same as SA that is, the Aero Non-Directional Beacons (NDB’s).
The Sept. 2000 issue of Practical Wireless has an article Michael Mucklow G4FIA on building a converter so that the Amateur 73 kHz band can be received. Do any of the SA readers of Radio-ZS know of such a band for us ZS hams?