[AMRadio] 4-400 first made when?

cemilton at aol.com cemilton at aol.com
Fri Mar 23 12:13:06 EST 2007

I've not researched the 4-400, but I can say for sure we replaced the 
4-125's with 4-400's when we upgraded our broadcast transmitter from 
.25kw to 1kw around 1961.  The transmitter was a Collins, 20J and the 
upgrade made it a 20V-2.

73 de W4MIL

-----Original Message-----
From: jpl15 at panix.com
To: amradio at mailman.qth.net
Sent: Fri, 23 Mar 2007 11:16 AM
Subject: [AMRadio] 4-400 first made when?

  In doing some research - I notice that the 4-400 seems to be a fairly 
late arrival, at least as far as RCA is concerned. It's in none of my 
HB-3s, not in my 1962 TT5, but is in the 1975 TT5 manual. Since my 
transmitting tube library has this 12-year gap, I'm assuming RCA began 
to produce the device sometime after 1964... does anyone have better 
info on the history and development of this very 'popular' power tube?

 Thanks in advance for any enlightenment!

 Okay - over and out...


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