ORIGINAL: ILIKE3D
Hey Guys
I was at my LHS the other day and a freind of myne told me he crashed his plane with a DA 50 in it. He said it was because of the hitec revievers he had. He said that you cant use hitec recievers with electronic ignition because there is too much interference. He said that you have to use PCM..
BUt this is odd because i was told not to use PCM because if there were interference the PCM would go to the preset position and you wouldnt know about it.
Soo im a little bit confused. Thanks again
---------------
No offense to your friend, but he doesn't know what he is talking about.
I use FM (PPM) receivers to help me get the bugs out of the model's electronics before switching to PCM. When the model has been made safe to fly with FM, then and only then will I use PCM.
What most folks do not understand is that the RF sections, the part of the receiver that does the listening, is essentially the same in both PCM and PPM (FM) systems. The PCM part of it all comes in when we get to the decoder. The decoder is the second part of the receiver. Its job is to tell which servo how far and when to move. FM utilizes an analog decoder (well - sort of), while PCM utilizes a digital decoder. The latter has the ability to ignore codes that it does not consider to be legitimate. The PPM decoder reacts to each and every pulse of significant amplitude and duration, thus driving the servos erroneously. The PCM system does not drive the servos at all during ignored pulses.
Most PCM systems have provisions for default servo positions if the codes are ignored for longer than a preset period. Some FM/PPM systems have similar provisions, depending upon the manufacturer of the system.
During the checkout period, it is better to "see" if your model is glitching itself with unintended emissions from the ignition system, or other noise creating systems onboard the model. One can't fix it if one can't see it.