ORIGINAL: hardtop351
yes both pcm and ppm use an fm signal as a carrier.
pcm....Pulse Code Modulation
ppm....Pulse Position Modulation
pcm is said to be more tollerant to interferrence. pcm is usually preferred over ppm in spark ignition models due to their tollerance to radiated noise from the ignition system.
cheers
craig
And the new 2.4 GHz system is better yet because it operates above all of the generated noise and never hears ANY of it. Spark ignition-OK, metal to metal connections-OK