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Re: [Amps] IM distortion and such

To: <>, <>
Subject: Re: [Amps] IM distortion and such
From: "Tom W8JI" <>
Date: Mon, 26 Jun 2006 06:03:14 -0400
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> It gives a manufacturer the chance to weasel out of 
> honouring the warranty.........

Not when they approve the operating conditions.

> There is another reason, however, and that is that a 
> manufacturer can have a subtle (or sometimes not so 
> subtle!) change in manufacturing technique that produces a 
> major performance change.

I think the problem here is this thread, like many on this 
reflector, has had a major performance change.

The original subject was the manual of the AL80 says to load 
to 550mA and then as a final step back off drive to obtain 
400mA. This ensures the loading is heavy enough and grid 
current is proper to handle ALC overshoots common with 
exciters. That horrified a couple people, although 
technically it is significantly better for all the 
components in the tank circuit to do that, better for IM3 
and IM5 performance, and it doesn't hurt the tube the 
tiniest amount to do that.

The second issue was someone claimed a curve in a constant 
current curve at one plate current value caused distortion. 
That statement is clearly in conflict with the actual cause 
of IM. Eimac's design handbook actually repeats what I 
posted, as would any reliable source. The final authority is 
the manufacturer and real world results, not subjective 
personal opinions or comparisons to cars falling from 

73 Tom 

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