> From: Joe Fitzgerald <jfitz@albany.net>
> w8jitom@postoffice.worldnet.att.net wrote:
> Tom, what is your opinion of generating two audio tones say, 2 Khz apart
> and feeding them into the mike of an ssb transmitter?
>
> -Joe KM1P
Hi Joe,
I don't think much of that method, because the exciter always has
IMD distortion and less than perfect sideband and carrier
suppression. Most tube PA's will go far beyond what a modern solid
state rig will do in IMD performance.
A CW carrier is much cleaner (unless from my IC751A with a switching
supply inside!).
Distortion can add to or cancel distortion from the exciter, so that
really confuses things. The owner of an amateur radio amplifier
manufacturing operation was going to patent an amplifier he claimed
removed exciter distortion in the PA.
I suggested he test the magic PA with another exciter before
he filed his patent. He did, and he found with another exciter the
trick PA circuit INCREASED IMD!
So much for the patent. That reason sticks in my mind as a good
example why a mic jack two tone test is "iffy".
I wonder what Ian or W6FR think about your question, since they are
very experienced with IMD measurements.
73, Tom W8JI
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