Rich says:
> Rp was 101-ohms for a resistance-wire suppresor vs. 166-ohms for a
>copper-wire suppressor.
Something puzzles me here. If the suppressor provided the whole plate load
impedance at the parasitic frequency, then the gain would be reduced by only
4.3dB by lowering the parallel resistance from 160 to 101 ohms. This may be
enough to just stop the parasitic, but doesn't appear to my mind to give enough
margin to ensure stability.
But in reality, the suppressor is only part of the plate load impedance. As a
result, the change (percentage reduction) in the load that the plate sees is
even smaller, so the gain margin between oscillation and stable operation
becomes even less.
This suggests that the phase shift is also part of the game: in that case, it
could well be that a higher Q on a smaller inductance could provide better
stability by giving a larger phase margin. ( I prefer phase margins and Bode
plots to Nyquist diagrams - I find them easier!)
And I won't repeat the joke about the plane crash and Polish couple.....
73
Peter G3RZP
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