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Re: [Amps] Biasing a Class C modulated final

To: amps@contesting.com
Subject: Re: [Amps] Biasing a Class C modulated final
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Tue, 17 Feb 2015 21:13:31 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Not sure the 6L6 would be a good choice due to price, unless you have some, or a good source. The price on them is astronomical. My guitar amp uses 6 of them. I could purchase a nice, new amp for less than replacing those tubes.

 73

Roger (K8RI)

On 2/17/2015 5:14 PM, KA4INM wrote:
  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.


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