[Amps] Clipperton-L parasitic suppressors

[Carl]

----- Original Message ----- 
From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
To: <amps at contesting.com>
Sent: Sunday, March 14, 2010 11:47 PM
Subject: Re: [Amps] Clipperton-L parasitic suppressors


> ORIGINAL MESSAGE:
>
> On Sun, 14 Mar 2010 21:23:39 -0400, "Carl" <km1h at jeremy.mv.com> wrote:
>
>>Which then isnt changable [grid-cathode impedance] and is out of 
>>contention for parasitics.
>
> REPLY:
>
> What makes you think the grid-cathode impedance is not changeable?
>
> For example, in a typical legal limit GG amplifier with no input
> matching circuit, the input impedance is around 50 ohms on a wide
> range of frequencies. If you add a simple parallel resonant tank
> circuit from cathode to ground (DC isolated of course), it is still
> around 50 ohms but only on the resonant frequency of the tank and
> drops down as you move above or below resonance. The higher the Q, the
> faster it drops. Make the Q high enough and the VHF impedance will
> drop low enough that the tube will not oscillate at VHF despite a very
> high Q parasitic resonant circuit in the anode circuit.
>
> That's just one example. You can also change the impedance using
> transformers, various other kinds of L-C networks, etc.
>
> 73, Bill W6WRT


Now youre drifting away from the basic discussion.

Carl