Hi Dr. John,
Have you looked into the Miller effect? The plate to grid
capacitance is low in the pF's, but as the tubes are usually
triodes?? Probably still far to small to make a big difference on
the primary, however, it seems it would effect maybe some drift in
the tubes frequency response and the tube would vary differently
depending on secondary characteristics (int/ext C). I guess what I'm
trying to say is that maybe the slight changes in for example the
top terminal C is mainly affecting the frequency response of the
tube. I would think spark loading impedance is a major factor when
tuning and it would appear although resonance is important of
course, in a VTTC, the tubes frequency response is affected by the
those sparks and slight other changes in C, and tuning is a means of
really getting the tube itself to respond well.
Just thoughts, no experience here.
Take care,
Bart
Dr. John W. Gudenas wrote:
Every tube has a set of characteristics that are defined by the
maker usually referred as the "characteristic curves". Fortunately
for our common transmitting triodes this operating data is all
readily available. Output impedance is an important issue for
optimal performance. For example, consider an audio amp that
matches to 8 ohm speakers. If you use 16 ohm speakers you will
still hear sound but loose a lot of power.
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