Agree with Mark, 2.4Ghz will get you and those around you peace of mind. It's designed to ensure that you only get one frequency, and others can't interfere with it by accidentally using the same one. Most also have fail safe if you lose the signal.
I would take the opportunity to go to 2,4Ghz from any crystal set (AM or FM) if I had the chance just to be sure that I minimised the chances of interference, and inadvertently being on the same frequency as someone else. HTH
