[Amps] 3CX1200 tubes

Jim Thomson jim.thom at telus.net
Thu Mar 26 02:59:36 EDT 2015

Date: Sat, 21 Mar 2015 07:30:20 -0700
From: "Randy" <hamradio at oz.net>
To: <amps at contesting.com>
Subject: [Amps] 3CX1200 tubes

Aside from the physical and filament differences is there much difference in
RF performance between the 3CX1200A7, D7, and Z7 tubes?  Is one more suited
for HF SSB service (lower IMD, etc.)?  If you had all three types available
and wanted to build an HF SSB amp project from scratch, which of these would
be the best choice?



Randy, W7HR

##  For a HB amp, go with the Z7  version.  No socket required... just a grid flange.
And WAY less C  from anode to cathode. That makes a huge difference to stability. 
A grid flange bonded to chassis provides the lowest inductive path  from grid to chassis
there is. 

##  Now if ameritron used a socket on their latest Z7 version, they have it wrong. 
The older ameritron amps with the  A7 version , neutralized the amp, cuz of the
inherent high C  from anode to cathode. 

##  You want to machine screw the grid flange of the Z7 directly to the chassis. 

Jim   VE7RF  

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