Jim if I follow correctly then the PTO MUST be connected to the circuit in order to see the +10 volts on the +10 volt line of the PTO.
The zener in the circuit will make sure that the PTO is getting the +10 volts.
OK let me connect the PTO with a couple of alligator clips to the +10 volt and ground on that small board that feeds the PTO.
I'm guessing that I can leave RF output and RIT wires off?
I will then measure to see what voltage is fed to the +10 volt line of the PTO and see if I can pick up anything with my spectrum analyzer on the RF out line.
Mark
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Mark N2DMI