Jim Brown wrote:
> Any ideas what's going on? The fixed capacitors in the tuner high
> voltage types, but with significant temperature coefficient. Are they
> heating and changing value?
I'm not familiar with these tuners, but if they use the doorknob
capacitors with N750 temp. coefficients, I am sure that is the problem.
I tried to use these capacitors at only 800 watts in a homebrew 80/160m
tuner and the SWR would start to rise almost as soon as I pressed the
key. I replaced them with large bathtub micas and the problem went away.
I also had a trap in my inverted L which used four parallel 68 pf 5 KV
doorknobs. At 1.3 KW, boom! I replaced them with another large bathtub
mica, which has worked fine ever since. I think the doorknobs are for
bypass service only.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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