[Amps] Parasitic suppressor resistor

[R.Measures]

On Jan 2, 2006, at 7:53 AM, Steve Thompson wrote:

>
>
> R. Measures wrote:
>
>> According to a Ham who telephoned me during the grate parasite debate,
>> who uses a computer program to design commercial amplifiers, the 8877
>> (C-fb = 0.1pF) does not need a parasitic suppressor if the anode
>> resonance can moved comfortably above 110MHz.  In practical terms, 
>> using
>> 150MHz as a comfort target, this means that the total L between the
>> anode and the Tune-C needs to be under 110nH.   In other words, if an
>> 8877 amplifier has an anode resonance of under 150MHz and it does not
>> use a VHF suppressor, it may be on the ragged edge.
>
> Did he (or she)

it was a dude.  Wimmen is too dam stuped to know much about RF.

> indicate whether the grid grounding and/or cathode
> impedance made any difference?

I don't think there was an entry field for grid grounding L.    Cathode 
Z is fixed at c. 54-ohms, however, the Z of the cathode-ground path at 
the parasite frequency would make a difference in how much feedback 
arrived from the anode to the cathode through C-fb.

cheers, Steve
>
> Steve
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org