Actually, the clamp tube was used when a fixed bias was not available.
The grid bias would drop to zero and the clamp tube would turn on and draw the
screen current down enough to prevent excessive plate current when no input
was applied.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of KA4INM [ka4inm@gmail.com]
Sent: Tuesday, February 17, 2015 5:14 PM
To: amps
Subject: Re: [Amps] Biasing a Class C modulated final
On 02/17/2015 03:11 PM, Paul KW7Y Baldock wrote:
> I am building a 2x813 class C final modulated by 2x813.
> The typical way to bias the class C final is with a combination of fixed
> bias applied to the control grid and bias derived from the rf drive
> through a grid resistor.
> Rather than fixed bias applied to the grid it seems that I could achieve
> the same effect by using a pseudo zener in series with the cathode,
> similar to what is used in cathode driven linears.
> Any thoughts on this approach?
I am guessing common cathode RF amplifier, a more standard way to do
it would be an adjustable bias supply and a clamp tube on the screen
grid. (6L6 or similar) look into any pre-1960 ARRL hand book.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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