In a message dated 2/23/05 11:23:15 AM Central Standard Time,
wlfuqu00@uky.edu writes:
For those that have tried the amplifier resonance test, the apparent
shift in resonance most likely due to the change of input impedance shift
of the input of the amplifier as you change the tune capacitance. You may
notice a change in the grid current or exciter to amplifier SWR as you
change plate tuning capacitor.
Bill,
When I was doing my testing, I ignored input SWR and grid current and just
tuned for maximum power output, and I still had the 'apparent' shift in
resonance. And in at least one case, the amplifier was a grid driven
amplifier,
which also 'negates' the effects you refer to.
Many amplifiers have apparent changes in input SWR as you tune the output
tank off peak.
I have a number of theories about why that happens that have nothing at all
to do with the tube itself, but rather due to the chassis layout and the
'shared' ground paths and changes in phase relationships between voltage and
current between input and output circuits; but that would open up a whole new
bag of worms, and I don't want to cloud the issues of the existing topic.
Regards,
Dennis O.
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