To answer your question: I have not looked at the earlier stages. However this radio passes on some bands but fails on others. ?
I don’t have a good way to look at earlier stages that is flat across frequency. About the best I can do is a scope probe with some series resistance and that will be seriously “non-flat”. ?I could look at scope waveforms and I could measure a mirror DC voltages and I could use an infrared thermometer to look at the driver transistors.
Those might be things to do when I get back from the next trip.?
Thanks for the ideas!
Gordon
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On Oct 19, 2023, at 18:54, Evan Hand <elhandjr@...> wrote:
?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
