Chris' experience is what I would expect. If you move the esc closer to the noise generator (i.e. motor) then it will couple more onto the signal line coming from the rx. It might have been made worse by contacting carbon fiber. Even though the lines from the rx are opto isolated (assuming there is no other noise path from the motor connection) in the HV85 you can still couple onto the input lines if you are close enough to the motor. I don't think it would make much difference what RF band your rx is working on, but it probably has a lot more to do with how it is designed in the first place. The motor isn't throwing off much energy in the 72 or 35mhz range (some distant harmonic of the switching frequency) so I think what we experience is noise on the signal and voltage line to the esc which cause problems at the rx. Most of the rx's out there seem to share a common power bus across all the servos so if noise gets onto the power line and signal line then it can affect the rx and all servos connected to it. So, to be safe, I decided to hook up the filter. I guess an opto isolated interface to the esc would achieve the same result as long as the isolator where far enough away so that the noise wouldn't couple onto the rx lines. That is basically how the optoisolated ignition kill switches work on large aircraft. The noisy ignition line is connected to the isolator. It does not allow the ignition noise to ride to the rx on the leads. It has the added benefit of being a kill switch. Too bad it is just an on/off. A real optoisolated throttle control would be neat. Run a fiber optic line to the esc from a sending unit that is located near the rx......