Hi,
In recent days much has been written about the G2DAF (linear?) amplifier
and although I have no wish to comment on that particular item I would,
particularly for the benefit of those outside the UK, like to offer a
little further information about Dick Thornley.
His designs, published in the R.S.G.B. Bulletin in the 1950s and 60s, for
SSB receivers and transmitters encouraged many readers of that magazine
(now known as RadCom) to build their own SSB equipment. His receivers,
which bore some resemblance to commercial equipment of the day, were well
ahead of their time employing a 5 - 5.5 Mhz tunable IF followed by a 455khz
mechanical filter (in the later versions).
The transmitter was more interesting and there was a number of ways of
generating SSB. Some used xtal filters in the 8 - 9 Mhz region while others
used 455Khz. (Being an impecunious chap in, or not long out of, short pants
I went the route of a 3 half lattice filter at 8400Khz using surplus FT243
xtals etched to frequency.) As I remember this was then converted to
1.6Mhz, at the same time doing the sideband switching, thence to a tunable
5 - 5.5Mhz (I think) and then up to the desired band 1.8Mhz to 30Mhz.
Balanced mixers abounded in both receiver and transmitter. I think my
version used a pair of 6146 in the final and I remember spending many hours
winding the coils for the rf section.
These were excellent designs and it seems a pity that this silent key's
reputation is being tarnished by this wretched amplifier. As a young boy I
was privileged to visit Dick in his shack and to see examples of his
workmanship which was first rate, both electrically and mechanically.
Dick was instrumental in the growth of the use of SSB in this country and
around Europe because, in those days, commercial equipment which came
almost exclusively from the States was beyond the means of most regular
amateurs.
Just a few thoughts on a great guy.
Chris G3VBL
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