As an experiment.
HDSDR and SoftRock Ensemble RXTX at 7.1MHz LO, USB transmission at 7.1MHz with two tones, 300Hz and 2.5kHz
Using an RPS1 to verify the amount of intermodulation products
First with less then -50dBc first intermodulation products
With -40dBc first intermodulation product
with -30dBc intermodulation
and with -20dBc intermodulation
Its not possible to do a quantitative analysis but at least you see when it gets really bad.
If you offset the transmission frequency 4kHz from the LO (easy to do in HDSDR you can see the intermodulation product much better as they appear at the other side of the LO
