The reference given to Pappenfus gives the equations for determining the level
of 3rd and 5th order products from the curvature of the line.
Noise testing is good, provided you are sure about the peak to average ratio:
to that end, noise with a notch in the middle of the AF passband leading to
measurement of the IMD power in that notch is good. The technique was used over
50 years ago in measuring FDM telephone systems, and was applied to
multichannel HF SSB tx's.
The question at the end of the day is 'How much use is the information about
more accurate levels of IMD measurement except as an academic exercise?' More
to the point is the IMD power in a SSB bandwidth at various offsets - as SM5BSZ
has measured. Plus the fact that the vast majority of amateurs neither
understand or care about how bad their tx is to the last few dB!
73
Peter G3RZP
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