Topband: Inverted L SWR Jumps ???

[HAROLD SMITH JR]

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.

73
KQ0C
Ash


Ash,

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.

73...Price W0RI
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