pr maybe Gordon,
I have not seen others post this type of problem.? Even my DE has compliance with all bands.? I would suggest a component issue with one of the mixers that does not provide a symmetrical response that increases the 2nd harmonic.? Or maybe it is an issue with the driver.? Have you looked at the spectrum of the driver feeding the PA?? The driver is also a push-pull class AB amp.? An imbalance there would cause a signal to be amplified as if it is part of the base signal.??
73
Evan
AC9TU