The frequencies used for wireless mics happen to be the same as those used for standard TV signals. Sometimes you can use inexpensive TV distribution equipment with decent results. Many times, it works OK, but remember it is very broad banded. If you are in a congested RF area (like a major market) it may cause more problems than it solves.
Understood-we rented 4 crappy lavs, and I ended up setting up for the next day at 3AM. I realized when I started getting that familiar raster hum that one of the mics was set to the frequency near or on LPTV channel 7 (170 mHz) here in Philly. The were off the air at setup, but on during show time. We got a refund for that one.
The only concern now is the Wi-Max annexing the former upper UHF channels.