[Amps] Super Cathode Driven Tetrodes

Fuqua, William wlfuqu00 at uky.edu
Wed Oct 31 19:22:21 EDT 2018


  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.

  73

Bill wa4lav


________________________________
From: Amps <amps-bounces at contesting.com> on behalf of Jim Thomson <jim.thom at telus.net>
Sent: Tuesday, October 30, 2018 12:27 PM
To: amps at contesting.com
Subject: [Amps] Super Cathode Driven Tetrodes

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

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