This is a follow up to my prior posting about the AGC cutting power back to
less than a watt in continuous modes like PSK31.
Thanks, folks, for the advice several of you sent. No, I don't believe it's
RF--for one thing, I rather doubt a few watts can louse up the system, when
100 watts on the Yaesu (switched in and out by two simple changes to the
Rigblaster connections) are RF "cold" in the system. I can't tell what starts
the AGC aggressively knocking down the power, except I think I can induce the
problem by overdriving. Then, I can't fix it until the K2 is off for a while
or I fiddle with it in an unrepeatable pattern. Perhaps, still, it is a heat
problem.
At full steam, when the K2 is running right, it idles in PSK31 at about 3
watts. Text transmission kicks it to 5 watts, and the steady tone at the end
of transmission kicks it momentarily to 7 watts. This seems to be the norm
for proper 5 watt operation, and IMD is minimal, according to reports. And, I
think the K2 will run this way without the annoying cut back so long as I
make sure the AGC light remains off entirely (i.e. no bar even flickers in AGC
meter mode). However, there is something in the AGC which, once "set" by
slight overdrive, won't return to normal unless the rig is off, or the radio is
played with by making band/power/freq/input changes of various kinds. It is
puzzling. Note, I only do digital modes on 20 meters, where the beam is
either very low SWR or the LDG automatic antenna tuner kicks in and brings the SWR
down to 1:1 as seen by the K2.
Anyway, I have rediscovered the hardiness of the old Yaesu 757 GX, whose
specs allowed for continuous operation in high duty cycle modes. And these
days, with sunspots in the zero range, PSK31 is much more fun at 75 watts than at
5 watts--and this from a confirmed QRPer. So, I reconnected the desk mike
to the K2 (and the keyer, of course).
Thanks again for the suggestions--anybody else experiencing something
similar?
Preston Douglas WJ2V
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