"Only use a wireless microphone when there is no other choice". I've said this for years and no one ever listens to me. But the problem is getting worse. The FCC in 2017 sold off a big chunk of frequencies that were popular with wireless mic users (the 600MHz band) to T-Mobile. As soon as T-Mobile starts using the band in your area it becomes illegal to use your expensive wireless mics.
This is not the first time this sort of has happened.
A big part of the problem is that many wireless systems are not 'frequency agile' that is they work on one fixed frequency and cannot be changed this is especially true of VHF band mics. Even systems that can be set to multiple channels only work in a narrow range of frequencies so if the band you're using get sold off or over run you can't tune it to a different band.
There are several bands where unlicensed wireless mics can be used but these bands are becoming more and more crowded as other users of various wireless devices (not just microphones) get condensed into a smaller and smaller piece of the airwaves. Most unlicensed wireless mics are in either the TV band or in the same bands that are used for WiFi.
Anything in the 2.4GHZ or 5GHz bands are subject to interference by WiFi signals. Keep in mind that most cell phones can be setup as a WiFi hotspot. Pop up a list of available WiFi networks in any crowded area and you will see dozens of them, every single one of which could clobber your wireless mic signal.
It gets worse. The TV band looks safe because TV stations don't move around from one frequency to another; they are at fixed, well known spots in the band. Choose a wireless mic system that avoids those frequencies and you'd think you were good to go. But wait, the FCC has mandated a 'repack' of the TV bands.
The transition to digital TV caused a big shuffle of channel assignments to make room for both analog and digital versions of TV stations. Now that the analog channels have been shut down they are going to re-shuffle the existing digital stations to final locations in the band. Most of the repack takes place this year. So your carefully chosen wireless mic frequencies may or may not work after the repack.
So to bottom line it either take your best shot and buy a good, frequency agile wireless mic system that you think will work now and hope for the future or buy something cheap and replace it as necessary as the situation changes.
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