10 feet! - wow that's really really poor. There is something going on here.

First change out the receiver and better - use a PCM receiver on gas engines. (They are somewhat less susceptible to interference.) Second, check for anything loose that could be metal on metal. Third, reroute the antenna outside the fuselage (at least temporarily) well away from servos and their wires. (I have had poor luck with internal antennas close to servos, particularly digital servos) Check for engine grounding as suggested. Check range again.

Let us know what happens.

Gerry Rosebery
Melbourne, FL