RE: What does PCM mean on a transmitter?
And to top it off, there was at least one AM/PCM system made years ago. In many ways AM/PCM could be made more interference-proof than our FM and FM/PCM systems, but AM got a bad name years ago due to the wideband AM systems of the time. In theory, you can make an AM set more narrow band and more selective than you can with FM.
Oh, and "FM" is actually a slight misnomer for our sets as well. There's another term that is more correct (that I've forgotten, it might be FSK?). But basically our FM transmitters don't actually modulate the frequency the way FM music radio stations do. Instead, they only use 2 frequencies, and hop back and forth between them. It's the amount of time spent at the center frequency compared to the amount of time spent at the shifted frequency (5khz off, if I recall correctly) that encodes the servo position. So, if you're transmitting on channel 12, which is 72.030Mhz, and you have a positive shift FM TX, then you're actually broadcasting on 72.030Mhz part of the time, and 72.035 part of the time.