Richard Clark wrote:
"Demanding that "new frequencies" must exist AND then saying that they
must be of such-and-such a magnitude to qualify is a hoot."

Glad you got a kick out of that. It is not original.

In analog microwave systems, often an baseband intermod monitor is used
to alarm the operator that nonlinearity has arrived in his system. New
frequencies have appeared and have reached a preset arbitrary amplitude
sufficient to trigger an alarm. Nothing is perfect so there will always
be some intermod. This requires setting a level of these intermod
products which will trigger the alarm. This is a standard procedure.

Best regards, Richard Harrison, KB5WZI