oldboldpilot
Key Veteran
Location: Southern California
| Swashplate,
The advantage of PCM is that brief moments of interference can't cause your heli to react in some violent fashion.
If the problem persists, well, oh, dear.  But you had a crash no matter what under those circumstances.
In my experience, I have seen the advantage of PCM over FM or PPM. I was flying my Logo 14, and, twice in five minutes, she went into "fail-safe" for just a second. My failsafe set-up is idle throttle, everything else stay where you were..
So I heard the throttle drop, but the heli kept going, and then the throttle came back up.
This happened in exactly the same spot in the sky.
At my field, helis fly here, fixed-wingers there. Turns out a fixed-winger's XMTR was "on," and, of course, we were sharing the channel. At the point where my RC set went into fail-safe, the heli was 1/2 the distance from his XMTR than from mine. This means his XMTR had 4 times the signal strength at the heli RCVR than did mine.
But using digital "words" versus analog signals is a big advantage. Had I been using FM, my heli would have been in the dirt. As it was, all his 4X signal strength could do is to cause a brief loss of communication in my RC set.
By the way, all digital communications uses a "PCM" kinda approach, although a bit more sophistocated. Your computer would never boot up otherwise.. 
Helis are Man's Defiance of the Laws of Nature - OCHC |
