One practice I have learned from others in the gas engines forum, is when setting up a new plane, use a PPM receiver and do extensive range checking at all throttle settings and 360 degrees around the plane. When satisfied that the installation is clean in that there is no signifigant loss in range when the engine is running as opposed to when it is off, now you install your PCM receiver knowing that it isn't just masking a noise problem. Of course this situation can possibly change over time as tolerances change of certain components in the ignition system and new frequencies or higher amplitudes may start to be generated.

Marty