The problem is not the TV broadcast stations.

But, as part of the reorganization of the electromagnetic spectrum, the FCC auctioned the 700 band to the highest bidders (including Qualcomm and AT&T) to facilitate the development of wireless broadband Internet service throughout the United States (and to make some money for the US government - more than $19 billion). While some UHF frequencies are fine, if your UHF wireless microphone operates in the 698-806 mHz bandwidth you may be subject to severe interference and possibly be in violation of the law.

Ironically the TV stations which currently broadcast in the VHF range will be vacating that bandwidth when they go digital (using cable connections). That means that the much maligned VHF microphones will get improved performance.

If you go for a VHF wireless mic, you should have no problems with cross-channel interference even if you have a large number of digital TV stations broadcasting in your area.

Again, let me clarify that the digital TV switchover will affect some, but by no means all, UHF wireless mics currently in use.  The UHF mics being made and sold now are not in the bandwidth that will be affected come June.  And in fact many makers of UHF mics are offering trade-ins on older wireless microphones for new wireless microphones that comply with the new FCC regulations. 

Wireless mics that operate on the UHF bandwidth generally provide somewhat better sound and clearer transmission – at a higher price – than VHF mics.  If you’re using your microphone for spoken word applications or even for karaoke, the sonic difference won’t really matter.  If you’re a musician using your mics in a studio or onstage, however, the new UHF mics may be advisable.