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Re: [Amps] 5CX1500A

To: <>
Subject: Re: [Amps] 5CX1500A
From: "DF3KV" <>
Date: Thu, 6 May 2010 22:45:23 +0200
List-post: <">>
The Penta data sheets shows IM3 figures in AB1 as follows:

2.5KV, 1090 out, -38db
3KV, 1330 out, -36db
4KV, 1785 out, -33db

If someone needs a copy I will send the pdf


-----Original Message-----
From: [] On
Behalf Of Jim Barber
Sent: Donnerstag, 6. Mai 2010 22:21
Subject: Re: [Amps] 5CX1500A

A text-searchable DVD set returns:

"Notes on the Eimac 5CX1500A power pentode"
Arthur Reis, K9XI
Ham Radio, August 1980, pp61,62
Text-only article, mostly anecdotal notes

- article describes some early production problems with tubes made 
between 1975 and 1979 (check your date code)

- author recommends loading tube as heavily as possible (!?) and not 
exceeding 6000 ohms plate impedance

- typical cautions on *not* bumping filament voltage to try to increase 
emission. (note the author claims 0.25V over-voltage will reduce life by 

- author claims Henry used the tube in their 4K model

- overall, author was rather lukewarm about using the tube in amateur 
service. Nothing stated about IMD performance.
"The 5CX1500A may not be the best of all possible worlds for linear 
amplification in the Amateur service"

Jim, N7CXI

Chris Pedder wrote:
> While I cannot pretend that my search was comprehensive, the only 
> 'similar' thing I could find was a 4CX1500B amplifier described by 
> W6HHN on page 56 of the April 1971 issue. I could find nothing on the
> Perhaps somebody else can do better.
> Best wishes,
> Chris G3VBL
> At 18:39 06/05/2010, Patrick Barthelow wrote:
>> If you can find someone's digital files copies of HAM RADIO 
>> MAGAZINE, they did a feature article about the 5 CX-1500A sometime I 
>> think in the Mid 80s.
>> Best Regards,
>> 73, de Pat Barthelow AA6EG
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