I don't think that this system using two diode detectors into a scope
would be a good replacement for actual IMD measurement. My reasons:
Even if both diode detectors have the same response curve, this system
would of course only detect amplitude distorsion, and that only if it is
strong enough to visibly bend the line on the screen. Smaller amplitude
distorsion would go undetected, and what's more important, all phase
distortion would go undetected!
In solid state amplifiers, phase distortion can be a prime cause of IMD
products.
So I think that genuine IMD measurement is the better route.
Also it's easier to do. Hams are more likely to own two or more radios
and a computer, than an oscilloscope!
Manfred
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