> ORIGINAL MESSAGE:
>
> On Sun, 14 Mar 2010 00:16:41 +0100, Dave White
> <mausoptik@btinternet.com> wrote:
>
>>
>>Isn't the real cause that the tube and/or circuit has Q at VHF? So isn't
>>the 'cure' that we try to lower the Q at VHF whilst trying to keep Q at
>>the fundametal that we're interested in? It may be a moot point as to
>>whether we're treating cause or effect. Search me, mate. That's too deep
>>a question at this time on a Saturday night after a few glasses.
>
> REPLY:
>
> For a tube to oscillate, the circuit Q has to be high enough on both
> the anode and grid circuits, enough so the gain is one or more and the
> phase of the fed-back power is correct or nearly so.
>
> In other words, the problem can be attacked in either the anode or
> grid circuit, or both. I have built several amplifiers with no
> parasitic suppressor at all, but where the grid circuit was designed
> to have a very low impedance at VHF, and the amps were all perfectly
> stable.
>
> Basic oscillator theory.
>
> 73, Bill W6WRT
Id say that was a basic description of neutralization.
Carl
KM1H
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