Aviation Groups Warn About Proposed Digital FM Boost

The aviation industry raised concerns about an NAB-supported FCC proposal to allow increased power for digital FM, in comments posted in docket 22-405 for Thursday’s deadline. Interference from FM digital broadcasting at the upper end of the 88-108 MHz band” could disrupt the operations of navigation and landing systems and “present a significant safety hazard," said the Air Line Pilots Association, International in comments echoed by the General Aviation Manufacturers Association (GAMA), the Aerospace Industries Association and others. GAMA is in talks with NAB about the matter, filings said. Though comments in the docket show wide support for the FCC proposals from broadcasters, NPR, Cumulus and REC Networks also raised concerns about interference and notifications.

The proposal to allow increased power levels for digital FM stems from petitions from NAB and Xperi, which went through their own round of comments before leading to a unanimously approved FCC NPRM in August (see 2308010060). The NPRM “references testing and analysis performed within the FM band to justify the rule changes,” but “there is no mention of any testing or analysis performed to ensure compatibility with adjacent protected Aeronautical Radionavigation Spectrum (ARNS) in the 108.00-117.95 MHz band,” said an ex parte letter from GAMA. In a footnote in their joint comment, NAB and Xperi said they “were very careful” in the proposal’s development that power increases comply “with all emissions limits and would not adversely impact any other spectrum users.” NAB and Xperi “have begun a constructive dialogue with GAMA to address and resolve their concerns.”

If an aircraft on approach to an airport “were to experience an undetected corruption in the guidance signal” from FM interference “it could result in the aircraft landing to one side of the runway or possibly even off of the runway, which could result in a fatal accident,” said the Airline Pilots Association. “We urge the Commission to re-analyze the compatibility of FM digital broadcasting with the ARNS band, in coordination with the National Telecommunications and Information Administration and FAA." Garmin made a similar request in its own comments.

The increase in power is intended to let broadcasters make digital FM a more widely used and successful service. A “significant contributor” to the complete adoption of digital FM technology was “the difficulty of replicating an FM station’s analog signal using currently allowable FM Digital power levels,” said iHeart Media. “A more robust HD Radio environment will promote free, over-the-air digital broadcasting as an alternative to fee-based digital services such as satellite radio and internet audio streaming,” said a joint filing from Beasley Media, Audacy, Galaxy, Spanish Broadcasting System and others. “There simply is no downside to adoption of these proposals,” said the radio companies. Digital radio has better audio quality, and allowing the power upgrade would dovetail with federal emergency alerting grants encouraging public radio stations to adopt digital technology, said a joint filing from nine noncommercial educational stations operated by schools and state education boards.

Cumulus and NPR endorsed the proposals to increase power levels but expressed concern about identifying sources of interference. New rules should give incumbent stations “means to quickly identify, and hopefully quickly resolve, any interruptions to their operations,” said NPR, asking the FCC to require notice to adjacent stations at least 30 days before a power increase. Cumulus said the agency should create a database of stations operating with increased power to let stations determine possible interference sources. “By its nature, digital FM does not provide audible clues that help listeners identify which station in particular is causing interference,” said Cumulus.

Numerous other commenters argued the FCC’s existing interference rules are already sufficient protection. ”Clearly, the current interference procedures have been effective” and “should continue to suffice,” said iHeart. iHeart said broadcasters should be required to provide notice within 10 days of increasing power, and no additional notifications “would be appropriate.” The FCC should protect LPFM stations from interference and consider proposals to allow low-power FMs to operate at higher power levels as well, said REC Networks.

Several commenters objected to FCC proposals to restrict the degree “super-powered” FM stations -- those that already operate with power levels in excess of their class, largely due to grandfathering -- can increase the power of their digital FM signal. “Limiting digital power increases by super-powered FM stations will disappoint digital listeners and undercut the incentive of these stations to promote digital listening,” said Mount Wilson FM, owner of KKGO Los Angeles. “While the number of super-powered stations like KKGO is low, they are located in major markets and serve important listening audiences.” The same interference rules that apply to other stations would also apply to super-powered stations, argued Mount Wilson and iHeart.