[CQ-Contest] Re: Choice of Narrow filters

spa spa at tri.net
Tue Apr 20 13:01:13 EDT 1999

>  You should be able to operate with a couple
> hundred Hz of any but the most overpowering stations.
> If you can't (or they can't) someone needs a new radio.

As an occasional contester, but a committed builder, I ran into this 20 years
ago.  When living in Wichita, I built a Martin style 160 only/CW only RX/TX
using:  A MCL 23 dbm mixer couple to the antenna with a double tuned coupler, a
one watt LO at 10.8-11.0 fashioned from the Gumm circuit in Hayward's book and
with the output capacitively tapped down for the appropriate drive, this followed
with a diplexer and a MOS VMP-4 post mixer amp running 28 v. at 400 ma. and then
into one of the KVG 500 Hz filters followed by the series of Plessey (now
discontinued) chips.  Never was satisfied with the AF AGC and the thing drew
enough power to be a transmitter, but worked.

To the point of this thread.  The first time I used it in one of the 160 contest,
as I'm not much of a CW op, just started at the bottom of the band, picked a call,
worked it, moved up, etc.  That way I had the call and number sequence before I
called the station.  Noticed that as I got close to a local across town there
would be some CW noise and would just skip across and continue....up and down.
Got a call on the phone a couple of hours into the contest....irate...."How can
you QSO right on my calling frequency?"  for that and a couple of later contests,
never knew he was there until too late.

Tough, I guess.

Next cycle may resurect the box and see how it holds up.


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