FCC Clarifies RF Rules as the 600 MHz Transition Begins in Earnest

Order offers concessions on alternate-frequency access, tweaks Part 74 licensing, makes 1.4 GHz band easier to use

The FCC’s Order on Reconsideration and Further Notice of Proposed Rulemaking published on July 14 revises and clarifies technical and operational considerations for wireless microphones, responding to petitions from Audio-Technica, Sennheiser, Lectrosonics, and Shure. The revisions follow the FCC’s Incentive Auction, in which major wireless carriers — including T-Mobile, Dish, Comcast, and AT&T — obtained licenses for large chunks of the 600 MHz spectrum (617-652 MHz and 663-698 MHz) to deliver new services to consumers.

Working together, SVG, DTV Audio Group, manufacturers, RF coordinators, and other parties obtained some important concessions through discussions with the FCC to obtain access to alternate frequency spectrum, tweak the Part 74 licensing criteria, and make the 1.4 GHz band easier to use, according to Jackie Green, president/CTO, Alteros. “It was a great effort from SVG, the DTV Audio Group, and industry professionals that really made a difference.”

Joe Ciaudelli, director, spectrum affairs, Sennheiser USA, concurs: “It was a big victory for the wireless-microphone community. There were a lot of issues that were highly technical, but we truly got the support of the commission, the Office of Engineering and Technology, the Wireless Telecommunications Bureau, and the support of the commissioners and staff in general.”

Wireless-mic users may operate on a Part 74 licensed basis in the TV bands and the 600 MHz duplex gap and in several other frequency bands: specifically, the 941.5-944 MHz band, 944-952 MHz band, portions of the 952-960 MHz band, the 1435-1525 MHz band, and portions of the 6875-7125 MHz band. This new Order further clarifies coordination requirements and operational limitations for licensed wireless mics in the 941.5-944 MHz band and 1435-1525 MHz band.

The Order introduces a new channel plan specifying the frequencies for microphone use in the 169-172 MHz band, addressing intermodulation issues and enabling more wireless mics to operate in this spectrum.

The FCC has clarified the procedure for use of the 941.5-944 MHz band, in which there are federal fixed operations. After coordination of the proposed wireless-mic operations with incumbent non-federal users through the local Society of Broadcast Engineers (SBE) coordinator, the applicant will need to file an application for an LPAS license with the FCC. Each application should include basic technical information: the operator’s proposed frequencies and maximum power levels, description of the proposed location, area(s) of operation, and date and time of use.

Previously, authorized wireless-mic operators at large-scale events deploying 100 or more microphones at a specific location were authorized for limited use of the 1435-1525 MHz band for specified time periods when alternate frequency bands were insufficient to accommodate their demands. This new Order confirms that a single operator is limited to 30 MHz of spectrum within the band. It also clarifies that different users in the same general area can each access up to 30 MHz of the spectrum in the band for their respective wireless-microphone operations. A single operator requiring more than one-third of that 90 MHz of spectrum can still apply for a special temporary authorization (STA).

The FCC’s Order has adopted the established European Telecommunications Standards Institute (ETSI) out-of-band emissions standard, which is more stringent than the U.S. version. By harmonizing with other countries’ standards, with which mic manufacturers already comply, this ruling enables operators to use the same equipment at more locations around the world.

The Order modifies a previous provision requiring the exclusive use of permanently attached or proprietary connectors for Part 15 unlicensed wireless equipment with detachable antennas, allowing standard connectors to be used.

According to the new Order, output power of wireless devices is allowed to be measured as either effective isotropic radiated power (EIRP) or conducted power at the output at the antenna terminal. This will allow engineers greater latitude in designing equipment with internal antennas or the larger antennas demanded in lower frequencies.

The FCC confirmed that unlicensed wireless-microphone operations in the 600 MHz guard bands and in one portion of the duplex gap under specified technical rules, as well as licensed wireless microphone operations under the same technical rules in another portion of the duplex gap, must be limited to an output-power level of 20 mW EIRP.

The Order permits Part 74 licensed legacy equipment operating within the 600 MHz band to be field-modified for Part 15 unlicensed or Part 74 licensed operation in the TV bands and the 600 MHz guard band and duplex gap under prescribed rules, including compliance with the applicable output-power limits and ETSI emission mask. This “permissive change,” requiring recertification by the manufacturer for its new purpose, will prevent costly equipment from becoming prematurely obsolescent.

The Future Notice of Proposed Rulemaking proposes expansion of licensing eligibility for certain professional theater, music, performing-arts, or similar organizations that do not meet the current minimum Part 74 threshold of “routinely using” 50 or more wireless mics. Under new rules, these organizations would be able to obtain a license to operate and register in the White Spaces databases for protection against interference by White Spaces devices.

For more information, click here for the FCC Wireless Microphones Guide.

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