Rich says:
>? A vhf suppressor partly de-Qs the anode-resonance by stagger-tuning
>it. This is accomplished by having two current paths of differing L, by
>aiming the two electromagnetic fields 90-degrees apart, and by causing
>roughly equal vhf current to flow in R-sup and L-sup. Naturally the
>differing L requirement depends on there being a substantial lack of
>inductance in R-sup.
Sorry, Rich, I totally disagree.
The parasitic suppressor works by increasing inductance in the plate circuit
until the plate parasitic resonant frequency is lower than the grid
parasitic resonant frequency. See Terman's 'Radio Engineering'. So
parasitics can be suppressed purely by adding inductance. It's often easier
however, to not pull the plate circuit that far LF, but to reduce the
dynamic impedance of the plate parasitic suppressor by adding resistance as
well tuning the plate parasitic resonance lower.
There is only one parasitic plate resonant circuit.
It does not get shocked into oscillation by switching the bias unless the
resonance is above or very close to above, the grid VHF parasitic resonance.
If it can be so easily shocked, why do you not see non-harmonically related
outputs from all amplifiers? After all, an amp or so of pulse plate current
every 71.43 nanoseconds (i.e. the fundamental plate current pulse when
operating on 14 MHz) should shock excite this VHF circuit much better than a
200mA pulse every 40 milliseconds or so from an el bug sending dits.
73
Peter G3RZP
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