While current FCC rules prohibit selling wireless microphones, intercoms or other low-power auxiliary Part 74 devices that operate above channel 51, it is still legal to operate these devices on channels 52-69 as long as they do not interfere with newly licensed services in this spectrum.
In August 2008 the FCC issued a Notice of Proposed Rule Making (FCC 08-188)[PDF] proposing a deadline for moving Part 74 devices out of channels 52-69; however, other than the ban on selling Part 74 devices using this band, no deadline was set for clearing out existing devices.
An item in the agenda for the Jan. 20, 2010 open commission meeting [PDF] indicates that the deadline may be set next week.
According to the proposed agenda, an Order and Further Notice of Proposed Rulemaking will be considered, as a requirement to complete "an important component of the DTV transition by prohibiting the further distribution and sale of devices that operate in the 700 MHz frequency [region]." The Commission's agenda also calls for establishing a date for existing devices to clear the spectrum and allow public safety services and next generation wireless networks to move in.
One of the issues the FCC will need to address is the large number of unlicensed wireless microphones operating within this spectrum. While use of such frequencies is supposed to be limited to licensed use by broadcasters and production companies, wireless mics have been readily available without purchasers showing proof of license and are in use by many churches, theaters and most likely local governments as well. These non-broadcast users probably don't realize that their microphones will soon become unusable.
Most of the 700 MHz wireless units operate at very low power and interference from them is likely to be limited, unless they're used near a cell phone site. However, it is likely the mics will stop working when Verizon, EchoStar, FLO and other 700 MHz auction winners fire up their high-power transmitters on these channels.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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