Peter,
If your antenna end insulators are covered with ice and snow, it is
entirely possible that the ice/snow covering will not show conductivity
with low power, but will become conductive at high power. That will
make whatever material you are using to support the antenna ends a part
of the antenna radiator - effectively lengthening the antenna.
Shake the snow and ice from the end insulators and/or use longer end
insulators and there is a good chance your problem will go away.
73,
Don W3FPR
On 3/9/2019 10:17 PM, Peter Dougherty wrote:
John, I know there were some issues with my old tube amp, but it did load
enough to get me 275-odd DXCC entities with 1500W on 80 CW. The KPA has
never been used in the past on 80 since I was having antenna trouble (one
end was down all winter and it just got fixed today).
Everything's snow covered out the back so I don't want to play around at the
coax switch at the moment. I'll try bypassing the switch when it's a bit
warmer and the snow is gone.
Of note, last year with the weird SWR, the "old antenna" (same physical
space and height, just all different materials) was cut to 3750 and I used a
tuner for the bottom end. I found the tuner kept giving me "unable to find a
match" when I tried tuning with high power from my tube amp. I figured
replacing every factor in that chain would fix the issue; the only thing
that's the same is the antenna switch and the physical orientation of the
wires themselves. New amp, new coax, new balun, new wire, insulators and
even the support ropes were changed out.
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