I am having trouble with my radio's range. At about 30-50 feet with the antenna down the servos shake. Even with the antenna up it is the same but at about 500-700 feet. I have a Futaba 9c radio on channel 38 with a r127df receiver, the stock futaba switch harness, 5 3003 servos, and a 2000 mah nimh battery. I Just bought the 9c so I thought that it might be the problem, but it also did the same thing with my Tower Hobbies 4fm transmitter. I have changed out the receiver, switch, and made sure the battery was charged well, but the same problem persisted. The next day, another flyer put his crystal which was 47 in my receiver and I used his transmitter with no trouble, so I think that the airborne pack is okay. The only thing left to suspect is my transmitters. Both of them do the exact same thing. I have been using the 4fm for about 4 years at this same sight and It has always worked fine. The only other thing I can think to blame is somthing is making interference on my channel. It is not just another transmitter because It has been at several different times of the day on several days. Tonight I took the whole system out a long ways in the country away from town and in a valley between 2 mountains with town several miles on the other side of one mountain. I got about 600 feet with the antenna all the way up before the servos started jumping. Does anyone have any idea about what could be causing this problem? Any suggestions of other things to try?

I am really frusterated. The people I fly with can't figure this out. I would appreciate an suggestions.
Thanks, Ryan