I am picking up RF interference while doing a ground range check, at less than a 100' with antenna down and engine off, the servos are chattering. After over 3 weeks of flying with absolutely no problems, now I have interference, the radio is a Futaba 9CAP with fully charged tx and rx batteries. No changes to radio or aircraft have been made. I did change receivers when I got home to eliminate a possible receiver problem, no change. Are there any ideas out there?