[Amps] Why does power output increase?

[Victor Rosenthal 4X6GP]

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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