On 1/17/2026 6:28 PM, Jim Lux wrote:
IM3 is a popular, and straightforward to measure, number - but not
necessarily directly relatable to performance with complex waveforms or
with amplifiers with transfer functions that aren't nicely represented
by a low order polynomial function.
Exactly. It's another thing we learned from Dick Heyser -- the effect
can be much easier to measure (and often is more meaningful) than the
that simple number. For IMD at RF, I look at the sidebands from the
transmitted signal -- how many dB down at various spacings from the
signal. This pdf is work I did about ten years ago in coordination with
ARRL Labs tests. It's another example of plotting data for multiple
measurements of the same quantity for different test subjects.
http://k9yc.com/TXNoise.pdf
This pdf documents measurements I was able to do with the Spectrum
display that Elecraft sold for the K3 transceiver.
http://k9yc.com/P3_Spectrum_Measurements.pdf
73, Jim K9YC
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