To Mike Roberts
In your newer wiring diagram you have inserted a diode in the V+ line for power from PC to Tx.
Only for a custom made buddy box you say, because of the low voltage.
I have a Futaba 8UAPS with removable RF unit, if this unit is removed could it be run using the PC power supply through your revised interface.
I'm having trouble with the jitters and so making the newer interface.