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Re: [Amps] Any designs for 4CX1000A on 2m

To: "" <>, "" <>
Subject: Re: [Amps] Any designs for 4CX1000A on 2m
From: "Fuqua, Bill L" <>
Date: Tue, 7 Jun 2011 20:05:55 -0400
List-post: <">>
These are really on 200 MHz and the tube is a variation of the 4CX5000A made by 
They were from a reasearch MRI used with small animals I believe. They were 
from the 
University of Kentucky Med. Center. The power supplies are rather heavy and 3 
No filter capacitors in either the amplifier cabinet or the power supply 
  Can take some pictures if you are interested. However, the tubes were 
They dropped the amplifier cabinets and tubes came out of the sockets. 
Have sliding hairpins for plate tuning as in many FM broadcast transmitters.
Bill wa4lav

From: [] On Behalf Of 
John Lyles []
Sent: Tuesday, June 07, 2011 7:12 PM
Subject: Re: [Amps] Any designs for 4CX1000A on 2m

That's impressive, I wonder how far they are derated the 4CX5000A at 220 MHz, 
in that amplifier. I tried using the 4CX5000A in a 5 kW FM broadcast amplifier 
in the early 1980s and found it difficult, switched to 4CX3000A and then Eimac 
introduced the 4CX3500A, which was a natural at 108 MHz.
I got the first tube for eval. from George Badger, and our product was 
introduced at NAB. Later, tetrode transmitter competitor still using the 5000A 
switched to the 3500A after we proved it could handle the power and the cathode 
was enough.
It had similar base but lower internal inductance than 5000A, I believe. I 
never touched a 4CX5000A again.


> That reminds me, I have a couple of 4CX5000A
> 220 MHZ amplifiers in the garage.
>   They are large and the power supplys extremely heavy.
> 73
> Bill wa4lav

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