[Amps] Super Cathode Driven Tetrodes

[Jim Thomson]

Date: Sun, 28 Oct 2018 23:46:21 +0000
From: "Fuqua, William" <wlfuqu00 at uky.edu>
To: Carl <km1h at jeremy.qozzy.com>, Jim Thomson <jim.thom at telus.net>,
"amps at contesting.com" <amps at contesting.com>
Subject: Re: [Amps] Super Cathode Driven Tetrodes

<Ok,

  <  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.


<73

<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