Well, the first thing is to find if it is the amp or the guitar. Plug in a guitar cable WITHOUT being in the guitar... is the interference there? If not, the pickup of the interference is in the guitar electronics. In either case, bypass caps need to be instaalled in the offending unit near the input to bypass the interference to ground. You will need to seek someone familiar with electronics to fix this. There is a chance that the only cure will be to distance yourself from the radio transmitter. The transmitter has to be an AM radio type as FM would not generate audio in your system.