Again, be wary of sources of information, there is much misinformation out there.

"Atmospheric conditions fouling up 1s and zeros" is not a science I'm familiar with. The simple fact is "ones and zeros" are much easier to detect than discrete positional shifts in the same PPM modulation used to send both signals ... hence the improved signal to noise ratio of PCM.

This link may provide you with a better understanding of PCM. [link=http://en.wikipedia.org/wiki/Pulse-code_modulation]Wikipedia - PCM[/link]. Keep in mind that modern PCM radios have surpassed the resolution of standard servos....