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FCC prepares for test of unlicensed TV band devices
1/19/2007

Today may ultimately prove to be an important day for the future of electronic newsgathering — particularly with respect to wireless mic operation.

That’s because the FCC Office of Engineering and Technology has asked parties interested in operating low-power devices on unused TV frequencies to notify it by today of their intentions to submit a prototype for upcoming testing.

While the process is of keen interest to those devoted to protecting DTV transmission from harmful interference, such as the Association for Maximum Television (MSTV), the devices to be tested and the way they are evaluated are also pertinent to those responsible for ENG wireless mic operation. The most commonly used wireless mic VHF frequencies fall within 174MHz to 216MHz, and in the UHF band from 470MHz to 806MHz.

According to MSTV president David Donovan, there’s already a shortage of spectrum for wireless mic use. As a result, frequency coordination for large news events, such as political conventions, can take months to coordinate, he said. Inserting unlicensed devices into the mix could exacerbate the already bad situation to the point where it may be nearly impossible to use a wireless mic without interruption from interference.

The high-tech industry has expressed a strong interest in using white spaces between occupied TV channels for new devices. The government, and FCC chairman Kevin Martin in particular, are proponents of expanding broadband Internet access nationwide. Using portions of the TV spectrum between occupied channels is seen as a possible solution for delivering wireless broadband service to rural areas of the country where running coax or fiber is too expensive or impractical.

Proponents of using unlicensed devices in the TV band envision products with built-in cognitive or smart technology to detect the presence of TV transmissions and prevent the device from transmitting signals that could interfere with TV.

Detection of wireless mic transmitters on TV frequencies, however, is a problem. The scope of the problem is potentially significant. While the range of out-of-band interference that could impact digital television reception may be about 75ft, first-adjacent channel interference can have an impact up to 2500ft and co-channel interference can disrupt reception for miles, particularly in areas with low signal strength, Donovan said.

The FCC test being set up to evaluate these prototype devices aims to examine how well these proposed unlicensed devices protect against interfering with TV signals.

According to Donovan, there’s no assurance that interference to wireless mics will be tested, which could endanger ENG. "I think you are going to have real problems (from unlicensed wireless devices)," he said. "You will never be sure that the wireless mics will work at the right time."

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