Two Tone Question
 

I am confused over the "ideal" frequencies to use for a two tone test of a
SSB transmitter. Art Collins' book states that using two tones with a 3 to
5 relationship will make it easier to identify intermod products and
harmonics and in fact Collins used 3 and 5 KHz as the two tones. Modern SSB
rigs only have about 2.7 to 3 KHZ audio passbands so 3 and 5 are not much
help. I see articles using evrything from 400 & 1900 Hz to 1.1 & 2.2 KHz..
Is there a "best" pair for testing modern rigs, or is this all a lot of hype
and any two tones inside the passband wil work?

Ron H.