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Re: [Amps] Replacing 811A with 572B

To: "Joe Subich, W4TV" <w4tv@subich.com>, Amps@contesting.com
Subject: Re: [Amps] Replacing 811A with 572B
From: Scott Manthe <n9aa@arrl.net>
Reply-to: n9aa@arrl.net
Date: Thu, 10 Apr 2008 00:22:54 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Joe,
The original question wasn't whether it's a good idea to replace 811As 
with 572Bs in general, it was whether it's OK to replace the 811A with 
the 572B in an AMERITRON amp, which most of us have concluded was one of 
the AL-811 series amps.

Most of us realize that the result will not be more power out, although 
reports of an extra 50 to 100 watts output are not uncommon, but VASTLY 
improved tube life.

Obviously, I, and many others on the list who've actually used the 572B 
in this application, don't consider it "not worthwhile."

73,
Scott, N9AA

Joe Subich, W4TV wrote:
>> The question was whether the 572B was a good replacement in this 
>> particular application. Given these parameters, the answer is yes. 
>>     
>
> I consider the question to be one of replacing 811A with 572B in 
> general.  Except for the unique case where the high voltage is 
> above the 811's ratings, the answer is still "not worthwhile."  
> The filament power is identical so the peak current capability 
> is the same ... the amplification factors are generally the same 
> so the 572B will not provide more power output unless the power 
> supply is modified for increased voltage.   
>
> 73, 
>
>    ... Joe, W4TV 
>  

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