Actually Pcm and PPm (FM) signals are sent the same way through the air. The major difference with PCM is that a code is modulated along with the rest of the information unique to the receiver. The receiver looks for that code and when or if it is absent the receiver can go into a preprogrammed mode set-up by the modeler. Pcm radios do cost more than ppm (FM) radios but some swear by them while others don't want nothing to do with them. It basically comes down to affordability for the modeler, and their preferences.