A little more troubleshooting on the sound card interface moved the problem from the radio settings (which I think I have set properly…blog post about my radio settings to follow) to the interface board.
If I use fldigi to transmit, nothing happens on the radio. PTT was being triggered, but I think that was flrig triggering the PTT over the serial port, and the radio would have been listening on the mic jack instead of the data port.
If I ground the collector lead of the transistor on the board to trigger PTT on the data port and then tell fldigi to transmit, then I hear transmitted sounds on the radio and there’s activity on the signal meter.
For some reason, the audio signal going out into the PTT part of the circuit isn’t enough to make the transistor switch and ground the collector pin.
I’ll have to go through that part of the circuit to make sure i have all the components right and wired up properly. Worst case scenario I’ll just wire in a button switch to manually ground the collector pin for manual PTT.