Hi David,
thanks for posting your schematic. Looks very easy. The most work
is to programm the PIC. I am not able to do this.
Congratulationes
Please look at the basis of the PNP audio emitterfollower.
The input resistance is ca. 100K Ohms, so a 0,1uF cer. cap
is better than the 10uF electrolytic. The leak current of this cap
can change the bias! (picture thread 8)
It is better to place the electrolytic from the bias pot to ground
to block noise from the 5V.
The bias poti is not a level adjust.
I am sure your PIC will work in the axing modulator too.
Did you switch off the audio carrier or not?
Please note that the audio carrier level should be 7dB under peack
white of the vision carrier.
Kind regards
Darius