This PPM vs PCM thing may be it. I can't for the life of me find anything to change the mode, either on the radio itself, or the manual, so it may be PCM only and not be able to switch to PPM.

The receiver is the one for Futaba/Hitec, but if it's the PCM vs PPM issue, that won't matter.

I'll keep trying to figure out if there's a way to turn the PCM off.

Thanks!