[Amps] Measuring IMD

[Peter Voelpel]

That probably is just a phase detector to check for correct anode tuning
state between cathode and anode (in phase) or grid and anode (180°).

73
Peter 

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Colin Lamb
Sent: Sonntag, 3. November 2013 15:53
To: audioguy at q.com; Karl-Arne Markström; g8on at fsmail.net;
amps at contesting.com
Subject: Re: [Amps] Measuring IMD


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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