> Wouldn't a VHF oscillation also cause a large low frequency current
> pulse the same as an arc would?
Why would it cause a pulse Gary???
Think about where the current comes from. The current all comes from
cathode emission. Current is limited by emission unless the tube has enough
gas or some other defect (like a misaligned element or debris) that allows
an actual arc inside the tube.
The entire circuit is designed to pass and optimize "pulses" or energy on or
near the operating frequency.
Not only that, even if there is an oscillation on VHF it would appear as a
series of at least half-cycle waves with a period far too short to make it
through lowpass filter (or bandpass) HF filter.
If an HF amplifier would freely pass VHF energy in and out through ports, or
allow extreme VHF voltages to build in the tank, it would be a TVI and
harmonic nightmare!
I sure can't think of any way any type of oscillation would cause an arc in
a healthy tube. Can you?
73 Tom
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