Ok, This is going to be a brute force hack. For the moment the game plan is to replace the microcontroller with one that is running special software. If I remember right that thing had 200 channels, spaced 5kHz.
So we will need a look-up table to translate the channels to the frequencies. 222.10 -222.15 would have space for 10 channels with 5kHz spacing. According to the band plan I found they are ment for CW and SSB and it looks like 223.7 to 223.75 is clear as well. Some research will have to be done as well to determine if ACSSB uses upper or lower side band and how much bandwidth it will take to fine tune that plan, 10 channels may become 8 or 9. Then the rest would be dedicated into the normal 223.76 to 224.98 20kHz band plan. For conversion to NBFM I will know more once I see some prints, but at the moment I am thinking to run a Repeater-Builder (tm) AP-50 or some thing else with the audio AC coupled into the transmit VCO. That will leave some debate over what to do with the difference oscillator. Either shut it down and run the VCO in the 222-225 range, or leave it run but with no modulation. Probably the latter which would failitate flipping a switch to go between FM and ACSSB. Receiver is going to be a bit more complex and I will know more when I see a schematic, but if nothing else I will design an IF strip based on the SA-604 to go in there. So it will become a single conversion receiver. I will also need to determine the IF frequency the receiver is using. Hopefully we can tap RF somewhere to make use of off shelf crystal lattice filters.
