Myself and 3 of my closest flying buddys all have cellphones on us at all times and we have never had a single problem. Phones ring on the flightline all the time with planes in the air and in the pits, turned on and running, no problems. I have always felt some of the clubs around that have rules against cell phones on the flightline were to keep people from being distracted, not interferred with, but who knows. By the way, we have JR, Futaba and Hi-tec systems with and without synthesized modules.