Not all wireless microphone systems are created equal. Start off first witha "ture diversity" system. This has two antennas on slightly diffent frequencies always sampoling the signal. if one drops out, the other picks it up seamlessly. And yes, selectable frequencies are amust for any situation. Other things to consider are bui8ld quality, and of course " battery management" Most major touring musical acts have a person that does nothing else other than babysitting the wireless microphones and managing the batteries.