As previously discussed in RF Report, the FCC has made it clear it doesn't want wireless microphones and other licensed low power broadcast auxiliary service (BAS) in the 700 MHz spectrum above Channel 51 after the analog TV shutoff.
With the loss of the 700 MHz spectrum and most TV stations crowded into Channels 7 through 51, wireless microphone users and manufacturers are looking at the 944-952 MHz aural BAS band spectrum. The Society of Broadcast Engineers issued a Statement of Policy essentially saying "Not so fast!"
The 944-952 MHz spectrum is already being used by radio stations to transmit their programming from the studio to the transmitter. Interference from a wireless microphone would make these links unreliable and subject listeners to noise or, in the worst case, complete loss of audio.
While cable television operators, motion picture producers, and television program producers are allowed to use licensed wireless microphones on unused TV channels, the SBE reminded wireless microphone users that 26 MHz, 162 MHz, 450/455 MHz, and 944-952 MHz Aural BAS band frequencies can be licensed to and legally used only by broadcast licensees and networks. The statement also pointed out that wireless microphones with 100 to 250 mW outputs have field strengths too high to operate as unlicensed Part 15 devices.
SBE said, "Contrary to false and misleading allegations by some vendors of wireless microphones, the 944-952 MHz Aural BAS band is heavily occupied in most areas of the United States. The band offers very little capacity for the operation of wireless microphones by eligible LPA licensees, and there are normally no options for unlicensed or ineligible licensees to use this spectrum at all."
Broadcasters or broadcast networks wanting to license wireless microphones in this spectrum must coordinate their use of the frequencies in advance with local SBE frequency coordinators. Frequencies will not be coordinated if there are nearby existing studio to transmitter or intercity relay links using these frequencies and interference to them is predicted.
The policy statement notes, "SBE will actively monitor this situation and will continue to pursue equivalent replacement spectrum for that lost in the 698-806 MHz band due to relocation, in bands other than 944-952 MHz, to facilitate licensed LPA operation."
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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