Don Wilhelm wrote:
Vic,
The K3 uses only a single wire to connect to the SO-239 jacks. The
return path is through the chassis metal. If one adds a direct return
path from the SO-239, that eliminates the potential for a haphazard path
for the return current. While a chassis return may be good enough in
one situation, let's suppose that the builder did not tighten the SO-239
mounting screws adequately, or the mounting hardware has begun to
oxidize, then the return path becomes more 'iffy'. Attaching a return
wire from a lug on the SO-239 to the board ground provides a fixed
return path that is not dependent on the chassis. Note that the return
currents for the two antenna connections can possibly interfere with
each other if there is any small voltage differential on the chassis
(there always is a differential, the question is just how small a
differential is tolerable).
That's certainly part of the problem. But just adding a ground wire
might create a ground loop. I guess the best way to do it would be to
insulate the SO239's from the chassis, and use hoods on them with coax!
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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