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Old 08-15-2006, 12:43 PM
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Join Date: Jul 2003
Location: Jacksonville, FL
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Default RE: mid price level radio to purchase

FM = Freqency Modulation, all 3 of the above use FM

PCM Pulse Coded Modulation, a digital way of encoding the stick position and transmit that data to the reciever. Benefits better noise rejection and interference tollerence but its more expensive.

PPM Pulse Position Modulaton, a analog way of encoding stick position and transmitting it. Cheaper but more suseptable to noise but thats mitigated somewhat by the use of dual conversion recievers.

Its important to know that both PPM and PCM use an FM signal, you will often incorrectly see PPM refered to as FM.

Synthesized = you can change to any channel in the band by manipulating either software or rotary wheels. Advantage is you can fly on other channels if the one you use is in use. Of course you either need a crystal for crystal controlled recievers for the channel you intend to use or a synthesized reciever. Disadvantage=cost.

Synthesized can be used for either ppm or pcm, it sets the channel and doesn't know or care how the information on the carrier is encoded.

Synth sets are nice but you usually need access to the reciever to change the dials or crystal, your best bet is to goto the field you plan on flying at and find out what the popular channels are and get your transmitter on something different.

PCM is probably better for helicopters but many of us fly them on PPM w/o any issues. As for other arguments about interference versus lockout, if the interference is bad enough to drive a pcm reciever into lockout its bad enough to knock a ppm receiver out of the air.

Heres some comprehensive reading on the subject.