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Re: [Amps] Measuring IMD

To: audioguy@q.com, Karl-Arne Markström <sm0aom@telia.com>, g8on@fsmail.net, amps@contesting.com
Subject: Re: [Amps] Measuring IMD
From: Colin Lamb <k7fm@teleport.com>
Reply-to: Colin Lamb <k7fm@teleport.com>
Date: Sun, 3 Nov 2013 06:53:20 -0800 (GMT-08:00)
List-post: <amps@contesting.com">mailto:amps@contesting.com>
A similar linearity-detecting scheme was used in a 3-1000Z design from 
the 1970 ARRL Handbook. "The SS-70 2-KW Amplifier", pp 204-208.

It used diode RF detectors in the cathode and plate circuits, a 
"balance" pot and a 50-0-50 uA front-panel meter.

I have no idea how well it worked, but this thread rang a bell and I had 
to go look it up. It would be interesting to try it. If the mechanical 
meter turned out to be inadequate, a connector for an external scope 
could be added.

73,
Jim N7CXI

Instead of using a meter, an led array should work fine, since the led has much 
faster response.  If you rectified the input and output of an amp and fed to 
companion led arrays, you could do the same thing as the scope.  In fact, they 
have solid state scopes that would work well and occupy almost no space.  

73,  Colin  K7FM
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