Monday, April 01, 2013

Plessey SL600 Transceiver

Image of my transceiver along with my 144Mhz transmitter and Hallicrafters SX24 receiver.

Last week I read an interesting article in RADCOM about the SL600 series of chips back in the 1970's and 80's. The article concerned the SL641 or SL1641 VOGAD chip.
Back in the late 70's I built a complete SSB hybrid transceiver for 160m and 80m. It was based on the SL600 transceiver by G3ZVC. The SL600 chips were abundant at the time and I purchased mine from Birkett's. Most were 'untested', but all of them worked a treat and were very cheap! The SL600's came in metal TO5 cans and were supplied by Birkitts with data sheets. (Which I still have)
When I built my transceiver I remember making a PC board for the G3ZVC circuit, but I can't remember if I used it or made descrete boards??  I know that building this transceiver was the biggest construction project that I have ever made. I bought an XF-9B SSB filter and crystals which was the most expensive component and also a new Eddystone 898 dial for the front. (I just love the Eddystone 898 dial!) The transmitter used an EL84 valve in the PA giving about 20 watts PEP output on 160m and 80m. The MD108 diode mixer was a brilliant piece of kit, so easy to use and no tuning.

On reflection, this transceiver was pretty amazing, parts of it were my own designs or adapted from circuits in RADCOM or handbooks. Getting it working was frustrating and I had to re-build parts of it. The VFO caused some problems, as did the power supply which was built on-board the chassis. A lot of metalwork and construction, but the SL600's were great! If I remember right I used a couple of SL610's in the RF stage, but the front end was a bit 'deaf' with the SL610 and I ended up building a pre-selector to improve the reception.

My transceiver (left) with 144Mhz transmitter, SX24 receiver and (above) 432 Mhz tripler and transmitter.

What I don't understand is why I decided to take it all apart, I know I had lots of niggling problems, but the project was worthwhile. I think it was in 1980 when for the very first time I bought an HF transceiver - the Yaesu FT101E (which I still have) I took it apart to concentrate and make more room for my FT101E. What a silly thing to do...I would love to still have that transceiver now just to admire the work I put into it!  Also, why did I not take photos of it!