Hello All,
Several month ago, after I finished my KPA100, I found that when
transmitting SSB on the higher bands (20, 17 & 15), the computer
speakers across the room, when turned on, would screech - adjusting the
speaker volume had no effect (but turning off the speakers quieted
them). During a QSO a few weeks ago, it was commented that it sounded
like I was getting RF into my audio.
To make a short story long, I don't have a very good ground
system, so there's a high level of RF in the shack - the shack is on the
2nd floor, about 18 ft above the ground rod. My primary antenna is a 100
ft multiband horizontal dipole feed with ladder line into a 9:1 balun,
which is connected to my KAT100 via 6' of RG8. While the antenna works
great on all bands (the KAT100 has no trouble tuning it), there's a
fairly high SWR on the feedline on the higher bands. I have two
different length wires connected the ground rod to the KAT100, and
adding counterpoises for 20, 17 & 15 meters hasn't change the high level
of RF in the shack on these bands.
A week or two ago, I put up a second antenna, a vertical
parallel dipole for 20, 17 & 15 meters, fed with RG8 - this antenna has
very low SWR on these bands. When using this antenna, I have no problems
with the computer speakers screeching, so there's apparently not much RF
in the shack. This weekend, during the NA QSO party, when using the
ladder line fed dipole on the higher bands, several times, I was told
that my audio was distorted, and switching to the vertical coax fed
dipole immediately cured the problem.
So, the question is, what can be done to fix the distorted audio
when there a high level of RF in the shack (besides getting a better
ground system - I plan to put in one or two more ground rods, but I
won't be able to do that until after the ground defrosts in the spring).
The mic I'm using is a RadioShack Electret replacement element in an old
mobile mic case - the case is plastic and not shielded, but the cable is
shielded, and I have grounded the mike jack in my K2.
All suggestions about how I can eliminate the distortion will be
greatly welcomed, as well as suggestions about how I can reduce the
high level of RF in the shack besides adding more ground rods.
Thanks
Bob W1SRB
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