Please Explain: PCM/FM/PPM
02-15-2007, 08:46 PM
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Please Explain: PCM/FM/PPM
I am sure a lot of people would like to know the difference betweek PCM, FM, PPM, G1-2-3, please explain! Thanks a ton in advance...
02-16-2007, 12:06 AM
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RE: Please Explain: PCM/FM/PPM
Hi,
PCM is Pulse Code Modulation and PPM is Pulse Position Modulation and FM is just frequency modulation. With Pulse Code Modulation, the pulses vary in length and I think the signal from the Txm to the receiver can be either PCM or PPM but only PPM from the receiver to the servos. Something like that. I'm sure others will have a better explanation.
Phil
PCM is Pulse Code Modulation and PPM is Pulse Position Modulation and FM is just frequency modulation. With Pulse Code Modulation, the pulses vary in length and I think the signal from the Txm to the receiver can be either PCM or PPM but only PPM from the receiver to the servos. Something like that. I'm sure others will have a better explanation.
Phil
02-16-2007, 03:09 PM
#3
RE: Please Explain: PCM/FM/PPM
FM is Freqency Modulation
PPM and PCM are ways to encode stick position but PCM is digital, they both use an FM signal to send the information to the reciever. Noise in a PCM signal is rejected as its not a 1 or zero, noise in a PPM signal is amplified and sent to the servos as position information and is whats seen as a "glitch" enough interference and PCM locks out, that is either does nothing or drives the servos to a pre determined fail safe postion (throttle to idle is the main one) until a good frame is recieved then you get control back. The downside is it costs more. Also to use PCM you must have a reciever from the transmitter manufacturer you cant use a generic Hitec reciever with a Futaba transmitter in PCM mode though you could switch it to PPM mode you loose the benefits of PCM
Also most PCM radios can be set on a per model basis to do either PPM or PCM.
PPM and PCM are ways to encode stick position but PCM is digital, they both use an FM signal to send the information to the reciever. Noise in a PCM signal is rejected as its not a 1 or zero, noise in a PPM signal is amplified and sent to the servos as position information and is whats seen as a "glitch" enough interference and PCM locks out, that is either does nothing or drives the servos to a pre determined fail safe postion (throttle to idle is the main one) until a good frame is recieved then you get control back. The downside is it costs more. Also to use PCM you must have a reciever from the transmitter manufacturer you cant use a generic Hitec reciever with a Futaba transmitter in PCM mode though you could switch it to PPM mode you loose the benefits of PCM
Also most PCM radios can be set on a per model basis to do either PPM or PCM.
