OK, I see what you mean. I made the unwarrantable assumption that one
automatically drives the grid up to zero volts to get the most swing -
but you don't have to, although that seems to be the recommended design
procedure for maximum output from any particular tube in AB1.
Re 2 tone tests;
>The only problem with a two tone test is it does NOT change power
>supply loading, except at a VERY fast rate (the rate is F1 minus F2,
>or 3 KHz in this case.
I've come across commercial specs which wanted the IMD's maintained down
to a tone spacing of 30Hz - that really canes the PSU - I'm sure that
the three tone test that you suggest, with, I presume, two of the tones
very close together, is a much more delicate and elegant method of test.
The noise loading of course, does have components down to low
frequencies. Noise testing with a notch in the noise band (and looking
at the IM noise folded into the notch) was written up by Marconi
Instruments some years back as a more delicate test for MCVFT signals
over an ISB tx.
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