Let see. RF plate voltage is proportional to RF plate current,,,,RF cathode
current is proportional to plate current....RF voltage across the cathode drive
impedance is proportional to RF cathode current and the cathode drive impedance
which is equal in magnitude to the tubes input impedance, if everything is
matched. The RF cathode to grid voltage is in phase with the RF plate voltage
The grid-cathode RF voltage is 180 degrees out of phase with the RF plate
voltage.
Sounds like negative feedback to me.
And it is. That is why a small additional resistance in series with the cathode
improves IMD and decreases the gain.
73
Bill wa4lav
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
Gary Schafer [garyschafer@comcast.net]
Sent: Thursday, July 30, 2009 12:09 AM
To: dezrat1242@yahoo.com; amps@contesting.com
Subject: Re: [Amps] grounding grids
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Bill, W6WRT
> Sent: Wednesday, July 29, 2009 10:29 PM
> To: amps@contesting.com
> Subject: Re: [Amps] grounding grids
>
> ORIGINAL MESSAGE:
>
> On Wed, 29 Jul 2009 21:35:47 -0400, "Joe Subich, W4TV" <lists@subich.com>
> wrote:
>
> >
> >Unfortunately, as shown by others this is not accurate and since
> >the negative feedback varies significantly from band to band the
> >floating/bypassed grids simply can't work as Heath claimed.
>
> REPLY:
>
> Also, that isn't true negative feedback anyway. It is just gain reduction.
> True
> negative feedback means taking a sample of the output, inverting the phase
> (if
> needed), and feeding it back to the input.
>
> 73, Bill W6WRT
How then would you account for the reduced IM products of a tube operated in
GG verses the same tube operated in a standard grid driven configuration?
73
Gary K4FMX
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