You can have IMD without any second harmonic.
All you need is the third order polynomial term of the Vout/Vin curve.
Simply have two Cosines of different frequency, summed together raised to the
power of 3 you get fundamental, third harmonic and the IMD products we see with
a two tone test.
I sent out a paper on IMD and Cross cross modulation some years ago to
this group. On vacation now and don't have it on this computer. Maybe one
of you can locate it. All the math is there. No rocket science. Just some
algebra and trig.
Peaking the plate tune cap last for max output does not mean that you have
matched impedance. It just makes the net result resistive and not reactive.
That is to say Resonant. Rather than off resonance.
73
Bill wa4lav
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