RE: FM or PCM Whats the diff
Both PPM and PCM use frequency shift keying which is in effect a form of FM. Both are sending a signal which is either one frequency or another, i.e. both digital in nature. The difference is in the manner in which this signal frequency change is handled versus time. There are many more transitions in a frame of PCM than in PPM but both are of a digital nature. The PCM signal is much more complex and requires more circuitry to properly decode. In either case, the signal to the servos are identical, a variable pulse width.