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Re: [Amps] Super Cathode Driven Tetrodes

To: Jim Thomson <>, "" <>
Subject: Re: [Amps] Super Cathode Driven Tetrodes
From: "Fuqua, William" <>
Date: Wed, 31 Oct 2018 23:22:21 +0000
List-post: <>
  Do you know anyone that has had first hand experience in running 4CX5000 
tubes in conventional grounded grid configuration? I have some that I would 
like to try perhaps. They have 75Watt control grid dissipation and 250 Watt 
screen grid dissipation.


Bill wa4lav

From: Amps <> on behalf of Jim Thomson 
Sent: Tuesday, October 30, 2018 12:27 PM
Subject: [Amps] Super Cathode Driven Tetrodes

Date: Sun, 28 Oct 2018 23:46:21 +0000
From: "Fuqua, William" <>
To: Carl <>, Jim Thomson <>,
"" <>
Subject: Re: [Amps] Super Cathode Driven Tetrodes


  <  Now that this discussion has gone on for some time, and everyone has had a 
opportunity to read various articles, here is the question.

<Can anyone give me a reason why a cathode driven tetrode with the control grid 
connected directly to

<the cathode be unstable. The screen grid is connected directly to ground. Low 
mu grounded grid configuration.


<Bill wa4lav

##  Its  rock stable, based on data  from the 70s, from nearby hams who used 
that config.    But that was a 4CX-1000
in both cases.   160 w of drive for  1200 w pep out on ssb / cw..... =  power 
gain of just  7.5..... =  8.75 db.
The  super cathode driven config  was only used on tubes that had virtually no 
control grid dissipation, like 4CX-1000, and  4CX-1500B  etc.
Tubes like  4CX-5000, and bigger, can have both their control grid and screen  
grid bonded to chassis.. and run like a high mu triode.... just like a 4-400,
or  4-1000.

Jim   VE7RF

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