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Re: [Amps] Old Moto RF Decks

To: Carl <>, "" <>
Subject: Re: [Amps] Old Moto RF Decks
From: John Kinney <>
Date: Mon, 1 Dec 2014 23:17:23 +0000
List-post: <">>
Hi Carl,

You are correct.  I saw very poor IMDs on the two tube version at anything over 
about 400 Watts.  I friend of mine helped me build a filter, 5 poles as I 
recall, for use on the output.  It brought the 2nd and 3rd harmonics down quite 
nicely, using two tone 1 kHz spacing.  We used an Anritsu Spectrum Analyzer for 
monitoring into a 2KW dummy load and the 2nd and 3rd harmonics were down about 
50 and 70 db as I recall.

It was a lot of fun playing with those old amps.


John Kinney
RF Solutions Team
Freescale Semiconductor
Tempe, Arizona
(480) 413-4290

-----Original Message-----
From: Carl [] 
Sent: Monday, December 01, 2014 1:43 PM
To: Kinney John-R17512;
Subject: Re: [Amps] Old Moto RF Decks

SSB IMD goes up rapidly above 300W per tube even with simplistic screen 
regulation. Be a good neighbor on the bands with those rather aged and obsolete 
designs (1947) that predate widespread SSB use.

Collins rated their 1960 AN/URC-32 at 500W with a pair of lower IMD 4CX250R's 
at 2000V while Eimac rated them to 2500V with poor IMD specs. 
Those transceivers, at 6' tall, ran fine without clobbering other close channel 
USN users.

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