Topband: Inverted L SWR Jumps ???
HAROLD SMITH JR
w0rihps at sbcglobal.net
Wed Nov 28 11:51:46 EST 2012
The sloper loads fine all the way up to 1500 watts. The inverted L loads just
fine to about 700 watts and then causes the Alpha amp to fault out. I think I am
getting a sudden change in antenna impedance. The antenna is fed through a 5 KW
rated choke balun. The feed line exits the base between radials. I've tried
various feed line lengths, I've replaced every component in the system except
for the antenna wire. The antenna does climb along the branches of a tall pine
before L-ing outward at about 55 feet. I think the problem is worse at night
time when things are cold (and perhaps more humid).
I'll be trying everything I can think of tomorrow afternoon, starting by trying
to minimize contact with the tree branches. All suggestions welcome.
Are you using any variable capacitors in your matching network? If so the plates
could be warping at high power. I had this happen and
went to vacuum variable capacitors. This cured the problem.
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