It's the electronic ignition that's creating the interference. I have first hand experience with this problem. I have seen this in both C&H electronic ignition and worse with the Fuji ignition. I was adjusting a brand new Fuji engine for a guy at my club and I noticed that the radio got glitches even when the transmitter was close by. I then asked the guy to range check his radio with the engine running and he couldn't even get 10 feet. Upon investigation, I noticed that the ground wire was hooked up to the engine at the engine mount. This is really bad grounding because the current has to travel from the sparkplug all the way through the engine and to the ground wire. If you ground it this way, the engine becomes the radiator. What you really want is the shortest distance to ground by means of connecting the ground wire directly to the base of the sparkplug. Study the brison engine and you'll see what I'm talking about. Even so, I doubt that you will completely rid of the problem. The main problem is that the electronic ignition is not properly filtered inside in the circuitry or they used a bad coil. My friend just recenly bought a C&H electronics ignition module and he was having the same problem. We tried to improve the grounding but without success. It did improve the range a bit but still not air worthy. He finally sent the ignition back to C&H for a replacement.
My advice is look for another ignition brand. The Fuji ignition is a lemon.