Hi Pieter,
I have been following along, and I even wrote draft reply but did not send.? IMO, you are further along on the diagnostic of the problem and may not truly be at a best solution. ?Since not stated, I infer that your not monitoring supply current and voltage at the uBITX nor RF power out.??Is your power supply up to the task?? Not just for what it was once rated.? Dropping input from 13.8V to 11.6V via 3 diodes reduces the current demand, changes transistor biasing.
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On the digital side, nothing that I am aware, will draw more power in TX than in RX while spinning the encoder to change frequencies.? ?To diagnose the reset, you need to capture voltage levels and reset signal.? Easiest with a digital scope triggering on a level dip of supply domains: (13.8V/12V-in, 5V, 3.3V) and the reset pin on the Nano / DTR from the CH340.??
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Just a few ponderings on my end with the goal of fostering other ideas and you reaching your best solution.?
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Regards,
Gary
