Henning and Glen,
Thanks you for the feedback. All interesting questions.
I sincerely hope someone with the test equipment can duplicate and fill in the blanks.
The only test I can think of performing is the 1dB compression point. Since I would use an RF probe with a diode I need a high enough input voltage to make the test meaningful even after correction for the diode's threshold.
So if the gain compression is most likely to be in the final can I measure the output of the driver's stage and the output of the finals while I sweep the RV1 pot for an analysis of the 1dB compression? Also should I measure before or after the LPFs?
All the best,
73, John (VK2ETA)