WASHINGTON—Wireless microphones are teed up for a regulatory update by the Federal Communications Commission at its July open meeting. The document circulated for consideration mainly addresses technical clarifications and post-incentive auction operations for licensed and unlicensed wireless mics across multiple spectrum bands.
"At a high level—what’s important—the items in this order are universally important for the manufacturers and the industry. The manufacturers were united in their request for clarification,” said Mark Brunner, vice president of corporate and government relations for Shure.
The draft Order on Reconsideration would eliminate a problematic out-of-band emission standard for wireless mics, according to Catherine Wang of Morgan, Lewis & Bockius LLP, who filed comments [PDF] with the FCC on behalf of Shure.
OUT-OF-BAND EMISSION MASK
“First, the draft order will eliminate the -90 dBc out-of-band emission level,” she told TV Technology. “This promises to be a big win for wireless mics as that technical requirement, if retained, would have been difficult for anyone to meet!”
The -90 dBc OOBE would be replaced by the standard established by the European Telecommunications Standards Institute. Joe Ciaudelli, director of Spectrum Affairs for Sennheiser, parsed the wherefore of these OOBE metrics. The -90 dBc is a relative measurement based on transmitter power output, he said. This makes it more difficult for a low-power transmitter to comply even if it posed less danger of causing interference than a higher powered one. The ETSI OOBE, which is used across Europe, is an “absolute measurement” that will subject all wireless mics to the same limit, ultimately making it easier for microphone manufacturers to manufacture microphones.
“Bottom line, the new licensees actually get better protection and wireless mics can be built in the real world,” Ciaudelli said.
The draft also addresses wireless mic power output levels for the 600 MHz TV and guard bands, and the duplex gap between wireless up- and downlink transmissions. The draft would allow power to be measured as effective isotropic radiating power—EIRP—or conducted, i.e., output at the antenna terminal, Ciaudelli said.
“This provides design flexibility, especially for equipment with internal antennas and/or in lower frequencies such as VHF that require larger antennas,” he said.
A 2015 rulemaking (p. 3) limited the type of antenna allowed on unlicensed wireless mics to those allowed under Part 15 rules. Specifically, Part 15 prohibits antenna swapping to avert potential interference. (Part 15 rules apply to unlicensed wireless mics, while Part 74 rules apply to licensed wireless mic operations that regularly use at least 50 microphones.)
Audio-Technica, Sennheiser and Shure requested that the general restriction on standard antenna connectors implied by Part 15 “do not apply to wireless microphones that are authorized to operate on an unlicensed basis under… Part 15 rules.” The draft would allow standard antenna connectors on unlicensed wireless mics, which Ciaudelli called “a
vital feature for engineers in the field.”
“The FCC also has some helpful discussion of how legacy equipment can be transitioned to compliance with the new technical rules after the transition period,” Wang said.
The draft clarifies that unlicensed wireless mics can continue operating in the 600 MHz band under Part 74 rules until the end of the 39-month repack deadline in mid-2020. Afterward, they must abide by Part 15 rules, which set forth a lower allowable power level and don’t provide the same interference protections as Part 74. Nonetheless, this means legacy equipment can be modified for continued use.
“This will avoid pre-mature obsolescence of many existing wireless systems,” Ciaudelli said.
Unlicensed wireless mic users will still have to check the white-space databases for open TV frequencies during the repack, the draft rules said.
“This is vitally important for many regional performing arts organizations who stage highly professional productions but don’t qualify for a FCC Part 74 license under current rules,” Ciaudelli said.
WIRELESS MIC FREQUENCIES
The draft further refines wireless microphone operation across several spectrum bands. First off, the draft denies petitions to allow Part 15 unlicensed mics to reserve TV channels—something Part 74 licensed mic operations are allowed to do. However, the commission recognized the need for flexibility on this rule and proposed allowing Part 15 operations to apply for vacant TV channels on a case-by-base, venue-specific basis.
Operational rules also were refined for three other spectrum bands: 169-172 MHz; 1,435-1,525 MHz and 941.5-944 MHz.
Currently, 169-172 MHz is a public service band used historically by state and local governments—e.g., forest fire-fighting channels—commercial entities, hospitals and the like. The commission previously opened it up for licensed wireless mics to operate on a secondary basis to incumbents. The draft adopts a revised band plan that “eliminates intermodulation effects and thereby enables full use of the 54 and 200 kHz—narrowband and broadband—channels throughout the band.”
“The specified frequencies for mic use are now optimally coordinated to allow more mics to operate in this band,” Ciaudelli said.
According to Mark Brunner of Shure, the commission recognized less UHF spectrum would be available for wireless mics after the repack and opened up 90 MHz in the 1,435-1,525 MHz band, now used for Aeronautical Mobile Telemetry. Although 90 MHz total was made available, individual users would be capped at 30 MHz, to be coordinated through the Aerospace & Flight Test Radio Coordinating Council.
Finally, Part 74 wireless mics have “long” been allowed to operate at 941.5-944 MHz, secondary to incumbents—primarily fixed microwave and aural broadcast auxiliary services. The draft lays out specific procedures for coordination through local Society of Broadcast Engineers designees, and licensing through the FCC for coordination with incumbent federal primary users, e.g., the National Telecommunications and Information Administration.
“This band can be useful for fixed venues, as a casinos, who need ‘house mics’ on distinct frequencies from travel acts.” Ciaudelli said. “Broadway theaters are another example.”
The commission will vote on the draft July 13.
“The issues addressed this Order On Reconsideration may seem like minor details to many but they have significant impact,” Ciaudelli said.