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[Amps] re: CTI screen regulator, tubes vs solid state

To: <amps@contesting.com>
Subject: [Amps] re: CTI screen regulator, tubes vs solid state
From: W8JI@contesting.com (Tom Rauch)
Date: Sun, 23 Jun 2002 21:34:01 -0400
The URL worked today, must have been a network problem.

Look at this text........

Triodes are Good, Tetrodes are Better.... 
Unlike triode amplifiers, the PLA800 uses tetrode tubes, which have a 
control screen grid. The screen grid not only adds to the 
amplification factor of the tube, but also controls the electron flow 
to the plate. When voltage regulation is used for the screen grid and 
with the plate overload circuit, as with the PLA800, plate and screen 
currents are limited to their maximum value. As a result you will not 
overdrive the PLA800 creating sideband distortion or splatter. 
Increasing the drive power beyond 50 watts, does not increase the 
power output. Because of this self-limiting feature, an ALC circuit 
is not needed. The amplified audio, as in SSB service, is clear and 
clean, void of sibilance and distortion. 

xxxx

What an unusual technical explanation about screen current limiting 
and distortion!!!

The schematic shows a cathode driven PA with no tuned input and no 
swamping resistance, just straight from the driver into the cathode.

A totally non-regulated control gid bias system without a control 
grid current indicator.

He uses the center tap of the HV transformer to supply screen 
voltage, and that is a good system.


   

73, Tom W8JI
W8JI@contesting.com 


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