The input network is a possibility.
Wattmeters are a possibility, though I've noticed this with two
different ones.
No lowpass filter.
There are no traps or inductors/capacitors in the transmission line and
antenna. Transmission line is open-wire and the tuner is a Johnson KW
Matchbox.
It seems to happen on all bands. This makes me think it's the bias
circuit rather than the input network.
73,
Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
https://www.qsl.net/k2vco/
On 04/06/2022 13:43, Rob Atkinson wrote:
Could be one or more things. Component in input network of amp
heating and changing value. Component in output (fixed value loading
padder cap) heating up and changing value. Something in the antenna
system heating up and changing value. This includes: Low pass
filter, watt meter, traps, baluns, ununs, anything with a capacitor
other than air or vacuum dielectric or inductor with an iron or
ferrite core. A tuned circuit is changing somewhere over
transmission time. Any cheap ham gear in the RF path is suspect. The
Matchbox is probably okay unless it has been modified with some part
not up to the job. Does this happen on one particular band or all
bands. Run the amp into a DL that is a decent DL like a Bird
capable of handling over 1 KW for a 30 minute xmission and see if it
still increases power. Just the exciter right into the amp and from
that to the DL. Depending on what happens that should eliminate some
suspects.
73
Rob
K5UJ
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