There is grid current. That is how negative bias is generated when using a
"grid leak resistor". It is bias by grid rectification.
Two types of clamp circuits were used. One use the DC bias generated by the
grid rectification of the amplifier it self to turn off the clamp tube and the
other rectified the RF in the clamp circuit.
73
Bill wa4lav
-----Original Message-----
From: "DF3KV" <df3kv@aol.com>
To: "Vic Rosenthal" <vic@rakefet.com>, <wlfuqu00@uky.edu>
Date: Sat, 9 Oct 2004 22:37:45 +0200
Subject: Re: [Amps] Need for input tuning circuit
----- Original Message -----
From: "Vic Rosenthal" <vic@rakefet.com>
To: <wlfuqu00@uky.edu>
Cc: <amps@contesting.com>; <philk5pc@tyler.net>
Sent: Saturday, October 09, 2004 8:10 PM
Subject: Re: [Amps] Need for input tuning circuit
> Years ago I built some 813 amplifiers for CW work. I used the
standard
> clamp-tube circuit in which class-C bias is generated by the grid
current flow
> through a resistor (i.e., the bias is in effect rectified driving
voltage) and
> the clamp tube protects the tube by removing screen voltage when the
key is up.
> This had the advantage of preserving the keying waveshape while
running the
> tubes in full class-C for efficiency.
Hi Vic,
How was full class-C maintained on the opposite cycle, when no grid
current flows?
For full class-C the 813 has to be biased with -155V at 2250V EHT
73
Peter
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