Hello good friends:
Very basic question here, but if you've never had
experience, how do you know? -
What are "typical" symptoms of RF feedback in the
shack? What does it look like, sound like, feel like?
I think I have a problem, but not sure. Remember last
week, I mentioned on 30 meters only, even at 5 watts,
after abt 15 minutes of keying (20wpm), my FT-840's
heatsink is warm (not burning hot, but warm) and the
cooling fan comes on. Well, if I turn the power up to
>10 watts, I notice a "buzzing" noise in my headphones
when the rig is keyed. It's very faint, but there. Sort
of hard to describe, but it doesn't seem right. Fuzzy audio
might describe it better.
Here's my set-up for those who think they might be able to
help:
FT-840 to tuner to 300 ohm twin-lead fed dipole up abt 30'.
Everything in the shack is tied to a copper pipe on my desk
via <2" copper straps. The pipe is then straped to an 8'
ground rod out the window via a 1' long piece of strap. The
shack is on the ground floor and ground rod is within 3' of
the desk. No computer equipment is being used.
I thought that maybe it was the 300 ohm feed line, but I
don't get this buzz sound using my 300 ohm fed 40 meter
dipole. Nor do I get this using the coax fed R5 vertical
on 20-10. This only happens on 30 meters.
One more clue: I get the "buzz" on 30m when using the 40m
dipole with the tuner. So, the common theme is "something
is amiss on 30m". Pity, too, as I like this band a lot.
The problem doesn't affect my operating on 30, I'm just
worried about hurting the rig.
Somebody here mentioned that I might have a parasitic
problem on 30m. Could this be causing the heating and
buzzing?
Sorry for the long ramble. Hopefully others might learn
what to look for in RF feedback as well.
Many thanks, gang!
73 de Dave NR3E/5
nr Dallas, TX
qrp-l #25, ARRL
WIMPS: Qs=002 30m=02 17m=00 12m=00 States=02/00/00
DX=00/00/00
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