Operating wireless mics

Regulatory framework for wireless mics is emerging.

The FCC is clearing the 700MHz band (TV Channels 52-69) of wireless microphones in order to make room for new uses. At the same time, it has grandfathered previously-illegal use of these Part 74 devices on Channels 51 and below subject to a power limitation of 50mW. None of this comes as a surprise. The FCC has been saying for more than a decade that Channels 52-69 must be vacated.

Wireless rules

Wireless microphones are used in live and televised musical presentations, and in most TV news and sports broadcasts. They are also used for live theater, opera, churches, lecture halls and anywhere else someone speaks to a crowd. Even the FCC's meeting room uses them.

Most professional wireless microphones use unoccupied channels in the TV bands. These do not cause interference to TV reception because the large users, and the companies that sell to small users, are careful about avoiding TV channels in use. Even organizations devoted to protecting broadcast spectrum have accepted wireless microphones.

Until now, the use of wireless microphones required an FCC license. Eligibility was strictly limited to radio, TV, cable, movie production and a few other groups. All other users have been operating illegally. Such users were supposed to occupy non-TV frequencies, but the TV band microphones work better and are the most popular. But, because the unlicensed use of wireless microphones caused no trouble, the FCC left things alone.

This changed due to the DTV transition, which involved the repacking of channels to free up the 700MHz band (the channels formerly known as TV Channels 52-69) for other uses. But some wireless microphones left over from before the transition still operate in that part of the band. These may cause problems for the new users of 700MHz, primarily public safety and commercial wireless users.

The FCC has now issued a Report and Order and Further Notice of Proposed Rulemaking that attempts both to clear the 700MHz band and, in the process, grandfather nonlicensed users. Under the R&O, as of June 12, 2010, and sooner in cases where there is a potential for interference, wireless microphones on Channels 52-69 may no longer be imported, manufactured, sold, leased or operated in the United States.

But until the FCC decides on permanent rules, both old and new users who are currently ineligible for Part 74 licenses may nonetheless operate legally on an unlicensed basis, at up to 50mW power, provided the frequencies used are below TV Channel 52. In its rulemaking, the FCC is likely to adopt final power limits for wireless microphones, decide whether new units must be digital-only, determine which TV channels should be available and determine the details of user registrations. The rules are likely to forbid data transmission, interconnection with the telephone network, wireless telephone headsets and after-market RF amplifiers.

Current licenses that authorize 700MHz band operation will automatically be modified to delete those frequencies effective June 12, 2010, but will remain valid for lower frequencies. A few licenses that are only for the 700MHz band will be voided.

Harry C. Martin is a member of Fletcher, Heald and Hildreth, PLC.


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Send questions and comments to:harry.martin@penton.com