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Re: [Amps] Old Moto RF Decks

To: Carl <>, John Kinney <>, "" <>
Subject: Re: [Amps] Old Moto RF Decks
From: Glen Zook via Amps <>
Reply-to: Glen Zook <>
Date: Mon, 1 Dec 2014 22:08:32 +0000 (UTC)
List-post: <">>
The 8560A is basically a conduction cooled 4CX250B.  The Eimac specification 
sheet on the 8560A states that the characteristics are similar to, but not 
exactly the same, as the 4CX250B.  The differences are that the 8560A has a Cin 
of 16.5 pf whereas the 4CX250B had a Cin of 15.7 pf and the 8560A has a Cout of 
4.6 pf and the 4CX250B has a Cout of 4.5 pf.
Otherwise, the "typical" operating conditions are the same for both tubes.
The main thing with the 8560A is that the heatsink plays a VERY important part 
as to how much power can be run.
I have a fair number of 8560A tubes left over from my two-way radio days.  I 
just don't have the heatsinks!
Glen, K9STH

      From: Carl <>
 To: John Kinney <>; 
 Sent: Monday, December 1, 2014 2:43 PM
 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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