About 4 years ago I picked up 2 bottom sections of what I think were 11
meter ground planes. The section looks like the bottom section for a
HyGain 18AVQ vertical or similar. The only difference is the mounting
flange has a plate that holds what looks like about ½" diameter ground
radials. The issue I am having is that I used that mounting section to
make a 20 meter vertical. Easy enough, right? WRONG. I used mating
tubes to make the ¼ wave 20 meter vertical but it resonated at...ready
for this.... 39mhz! Then I grabbed the second one and used it. Now it
resonates at 13.5mhz but shortening the vertical does not bring the
frequency up. I am wondering if perhaps someone (CBer maybe) ran way
too much power through them and broke down the dialectic of the plastic
(or whatever that is) insulator that isolates the vertical from the
mounting bracket and ground. That is the only explanation I can come up
with as to why it is so far off.
Does anyone have any suggestions as to how to fix the problem?
Thank you.
Jim Pruitt
WA7DUY
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