What reciever should one use on a gasser with a 72MHz radio.
Are PCM recievers an absolute MUST?
Avijit

PCM would be strongly advisable for couple of reasons.

1.  It is less susceptible to glitches than regular FM (PPM).  A glitch during landing would not be pretty.

2.  PCM provides "failsafe" capability.

Not much personal experience on gassers, but PCM versus PPM was one of the first ever issues I had to learn in RC (while troubleshooting glitches on a Trex 450 heli).

It should be noted that both PPM and PCM uses frequency modulation (FM). So, whatever be the source of interference would affect both PPM and PCM equally. However, PCM is a more resilient as it transmits the stick information as digital data (with CRC) rather than just pulse duration (PPM). So, PCM is better than PPM.

As pointed out by Anwar bai, in event of continuous interference or loss of signal PCM has an advantage of failsafe settings which PPM does not offer.