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Re: [Amps] Class C amp for RTTY contesting...

To: Robert Chudek - KØRC <k0rc@pclink.com>,<amps@contesting.com>
Subject: Re: [Amps] Class C amp for RTTY contesting...
From: "Tom W8JI" <w8ji@w8ji.com>
Date: Thu, 2 Nov 2006 19:39:02 -0500
List-post: <mailto:amps@contesting.com>
I have a few questions about this idea:
What would be needed to convert a "traditional" linear 
(AL-1200, AL-1500, L-4B, TL-922, etc) to strictly Class C 
operation?>>

Too much work.

Is there a specific tube (or tube series) that would be more 
efficient when run in this class?>>

Yes, a low mu grid driven triode with very high peak 
emission current.
You want a tube that can produce very high current pulses 
(very low anode to cathode "on" resistance) without damaging 
the tube. You want a switch, not a linear tube.

What efficiency could be expected?>>

If you play your cards right, about 90% or more. The 
theoretical limit is right at 100%. RCA made a BC 
transmitter that ran in the lower 90% range. It was a low mu 
triode with third harmonic resonators in the anode and grid. 
We had one at WSPD that had a very slight metering error in 
three of the meters, and it calculated to be 102% 
efficiency. :-)

Class AB at the edge of B can be over 70% in theory. As I 
recall about 75%.

Does Class C provide more/less gain (drive power) to obtain 
1500 Watts output?>>

Generally speaking less gain.

Don't try to run CW through it though!

73 Tom 


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