>
>> The resonance of SB220/TL922 grid-ground circuit is given by the parallel
>> of few mH and few hundred pF, actually that circuit is never really "open"
>> at any frequency because of the low Q caused by the consistent Ohmic
>> resistance of the long inductor (litz) wire.
>
>The chokes were various types through the life of the amplifier, but
>none I'm aware of were ever Litz wire. Even if they were, the grid
>impedance would still have been very high.
>
>> understand why a Gg mounted triode with some series resistance between
>> grid and ground should have a bigger tendency to oscillate at VLF (or any
>> other frequency) than when the grid is straightly grounded and gain
>> increased.
>
>1.) The Pi network is a lowpass that looks almost transparent at
>low frequencies.
>
Mr. Rauch conveniently ignores the 50uH hv-rfc and 2000pF B+ bypass cap.
>2.) The blocking capacitor can be made to present a wide range of
>impedances at the anode with an inductive load (which is
>independent of the SWR on the operating frequency) at the output.
>
[chortle]
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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