Radio Page. _ .. . _ _ . . . . . _ . . . _ _ . _
Amateur Radio - often called Ham Radio - is one of those 'technical' hobbies and attracts people from all walks of life, technical and not. My Ham Radio interest started when we visited my great Uncle Fred in Dorking back in the 60's. He had his equipment set up in a room at the top of the house. The garden was full of antennas - as far as I can remember, it was owned by the Admiralty, and he had the top two floors of this massive house. He spoke Italian, German and French fluently and would speak to amateurs from various countries. His gear consisted of a KW Vanguard, running 50 Watts of Amplitude Modulation on 80m (3.5MHz) through 10m (30MHz). The Vanguard was built like a battleship and was designed around the Geloso VFO. His station receiver was an Eddystone 730/1A.
On one visit he gave me a 'kit' of bits to make a crystal set and one day, Dad and I set about assembling the beast. Simple, but effective - well, it picked up the BBC world service from DWS Crowborough about eight miles away. I canibalised various bits and pieces and built a second receiver for my brother Philip. We would lay in bed at night listening through headphones to programs in Serbo-Croat, French and various other languages and knew the various Signature tunes and channel keepers by heart - Lily Bolero, the Drums, the Trumpet Fanfare and various others.
My father had, some years before, bought another Kit - a TRF receiver for medium wave using 2 miniature 'battery' valves. We built this on the kitchen table over a few evenings and it worked well, picking up a few other stations across medium wave - as well as the world service from Crowborough!
As time went on and SSB became more widely used, Uncle Fred bought a KW2000A. This beastie ran 180W PEP on 80m through 10m with reduced power on 160m where the limit was 10W. This popular rig was really state of the art, consisting of a 455kHz DSB generator and a mechanical filter, the output from which was mixed with the VFO at about 2.5MHz and after bandpass filtering, mixed with an appropriate HF oscillator to bring it onto the desired band. Using common oscillators, the receiver was effectively the reverse of the TX section. The upshot of all this is that I was lent the Eddystone and became a Short Wave Listener, joining the RSGB (for the QSL bureau) and being allocated the number A7573. Dad and I fixed an antenna up in the back garden and I was away, logging various communications.
Day release from school to West Kent College in 1970 introduced me to electronic theory and to some friends that were licensed! Mike Hayes (G8EPD) and Steve Ireland, (G3ZZD). I joined the Tunbridge Wells ARS and in 1972 or '73, learnt Morse code, brilliantly taught by Bob Smith, G6TQ. I'd been lent the Vanguard by now and was happily pirating on CW using Mike's (by now class A) Call. Eventually, at Christmas 1975, I took the RAE and passing, had to sit the Morse exam again - I was quite out of practice but scraped through. My licence arrived on 5th Feb and I phoned Mum from work to switch the rig on. The rig was a KW2000 I'd bought from a local amateur! This beast gave me 90W of SSB and 75W of CW, 160-10m.
I bought my first Bug key around this time - a McElroy mechanical. I paid £5 for it at a junk sale as nobody else wanted it! I still thoroughly enjoy using it today. It's action is excellent, the operator having to produce the dashes whilst dots are made by a sprung loaded bob weight.
I experimented with various bugs and electronic bugs from simple transistor multivibrator circuits through 7400 series logic and 4000 series logic to up to date microcontrollers. All have their good and bad points but I think my favourite electronic key is an Iambic mode made in CMOS logic.
In 1985 with college over, I moved out to Lancing in West Sussex. Here, I had more room to experiment and became fascinated with home construction of mainly QRP equipment. I firstly joined the G-QRP club and bought their excellent circuits book, in which I found plenty of ideas and soon formulated plans for a rig.
RAF Straight Key
Mc Elroy Mechanical Bug
The junk box was raided
and an Eddystone slide-rule dial in a box that once contained an oscillator
was used to house a 1Watt transistorised transmitter
on 80m. I went straight for VFO control and used the oscillator to drive a mixer and an audio amplifier giving me a transceiver!! After various trials and modifications, including the addition of independent receiver tuning, I had a worthwhile rig and, using the G5RV, worked many stations around Europe. (see the 'Homebrew Rigs' page).
There were new circuits every quarter from 'Sprat' - the G-QRP Club's magazine and various rigs were built for 40m, 160m and 30m - all CW.
There were also kits for sale - with various levels of expertise required to complete them. One kit was for a 20m/80m band imaging receiver using a 9MHz crystal filter. This was marketed by Kanga and designed by Ian Keyser G3ROO. Again, the junk box was raided and money spent on an IQD crystal filter but I ended up with a very respectable dual band receiver for both CW and ... SSB. It wasn't long before I added another mixer (using a Plessey SL6440 IC) and a small driver to get a CW transmitter working. This produced about 20mW and I managed to work a couple of stations on 80m. Adding a mic amp, RF mixer and eventually a 20W power amplifier gave me a very respectable transceiver. The rig went through several modifications and I learned so much from it. I used it both at home and mobile and can vividly remember being on a caving trip to Wales and taking the rig out in the car up on top of Treherbert mountain at the head of the Rhondda valley. I called an American station and he came straight back with a 5-9 report. We chatted for 20 minutes or so and it left me with a terrific sense of achievement.
I built various other rigs from 'Sprat' including the CSP, a 3-Watt 20m SSB/CW rig based around the NE602 IC, (designed for use in the old analogue mobile phones!). This IC was at the heart of various rigs for both CW and SSB and remains popular amongst constructors.
In 1991, Ian designed an all band transceiver based around a frequency synthesizer. This was serialised in 'Sprat' and although it left a fair bit to the individual constructor, gave fairly well explained guidelines for a modular rig. It was similar in principle to the 'Cheriton', so the circuitry was somewhat familiar but I added various circuits of my own, spending about two years building the rig and ending up with a useable all bands HF transceiver, working many stations (by my standards!) using it on both SSB and CW. Ian called the rig the Kitten II - he'd obviously built a Kitten earlier! See them all on the Homebrew Rigs' page.
Another favourite rig, built from a design in Sprat was the Malta 40. Designed by Steve Hunt, G3TXQ, the design proved justifiably popular. It is a CW only rig and designed for 40m giving 4-5W output and having a strong receiver front end. This rig is the one I take on holidays and I've had many contacts using this from odd locations - camped in the New Forest, whilst on a climbing trip to Snowdonia, and annually on the family cottage holiday. Antennas are always lengths of wire thrown over tree branches and loaded against ground or a counterpoise. I should really be more adventurous but as I never know what (if any) antenna supports will be available, the wire always goes in.
Other gear I tried included an Eddystone 888A receiver. This receiver was built for Amateur bands only and had great bandspread and sensitivity. A fine addition to any station, I found I only really used it when trying out a new QRP transmitter. It's limited frequency range meant it had few other uses in the shack and as space was limited, I sold it - fortunately, to a collector, so it went to a good home.
The old KW2000A's were sold in 2004. I came to the conclusion that there were others who would get more out of them than I was. I still retain an interest in these rigs and follow the day to day postings of the KW electronics group on Yahoo!
I've written a short article on my experiences with the Kokusai mechanical filters used in these (and many other) rigs. They age badly and the foam that originally supported the filter element changes consistency and becomes an orange gunge which changes the characteristics of the filter, increasing its insertion loss to a point where the transmitter loses drive and the receiver becomes deaf. You can read the article on line here or download it as a .PDF file here.