The 509 used audio filtering the agc in the rig is derived from the
audio stage. There was an optional filter that plugged into the round
black socket in the back of the rig and it works very very well. One of
the nice things about it is it filters before the agc so that when the
filter is in, the agc only responds to what you hear which keeps the
sensitivity from being affected by stong adjacent signals. If you dont
hear the signal it will not affect the sensitivity. Now you probably
can't find them any more at least I couldn't so I duplicated the
circuitry from the Omni series which used the same method and built it
in an external case. If you are a builder I can probably find the board
layout and circuitry and email you a copy.
Regards
Jim
W8IT
mikkelsens wrote:
> From OZ4XF HenningI have bought an old argonaut 509 recently and it's
> fun to rediscover cw, but I have a problem aboutreceiver
> performance.So can anybody help with an article from ARCI journal
> about adding a crystal filter to the argonaut 509 ?and perhaps other
> articles on improving receiver selectivity.My email is
> mikkelsens@mail.tele.dk
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