Several aviation groups have recently expressed concern about the potential for interference on navigation systems if a proposal to increase power for digital FM stations in the United States is adopted. Now, HD Radio developer Xperi said it is working to address those concerns.
In comments filed with the FCC (MB Docket 22-405), the Aerospace Industries Association (AIA) and the Air Line Pilots Association International (ALPA) raised the possibility of interference between HD Radio stations at 107.9 MHz and the adjacent Aeronautical Radio Navigation Service (ARNS) band operating from 108.0 – 117.975 MHz.
The ARNS band is occupied by safety critical navigation and landing systems essential for safety of flight, according to the groups. They include Instrument Flight Rules (IFR) needed for landing during low visibility conditions at night and during inclement weather.
[Related: “Airline Pilots Worry About HD Radio Power Proposal“]
The FCC has proposed a change to the methodology for determining a digital FM station’s allowable power to allow additional stations to increase FM digital power levels. The NPRM also would authorize asymmetric sideband power levels without the need for experimental authorization.
In new comments filed late last week, Xperi said it and the National Association of Broadcasters are engaged in “constructive dialogue” with aviation and aerospace industry stakeholders to address whether the HD Radio proposal would be compatible with aviation navigation services.
Xperi also said it “will continue to provide the FCC and all stakeholders with the technical support necessary to ensure that the proposed rule changes laid out in the NPRM will, as the commission tentatively concluded, ‘advance the commission’s ongoing commitment to developing terrestrial digital broadcasting with minimal to no adverse effects, including any harmful interference, on existing service.’”
The proposed rules, if adopted, would rely on the FCC’s existing interference mitigation and remediation processes and notification procedures. Xperi has said implementation of the proposals will allow broadcasters to take full advantage of the flexibility provided by HD Radio technology and increase the reach of the digital signals.
AIA, in comments to the FCC, said while the NPRM references testing and analysis performed within the FM band to justify the rule changes, “there is no mention of any testing or analysis performed to ensure compatibility with adjacent protected ARNS spectrum.” The group has identified a number of locations across the country where licensed FM broadcast towers operating near the 108 MHz band edge are in proximity of airports with active aviation navigation aids.
However, AIA expressed confidence in its most recent comments referring to its engagement with the broadcast industry. “Efforts with the NAB will be focused on constructive dialogue to determine whether there are, in fact, material concerns for coexistence between FM digital stations operating at higher powers under the proposed rules and important aeronautical systems adjacent to the FM bands,” AIA said.
The pilots union, or ALPA, which represents the safety interests of over 75,000 pilots flying for 43 airlines in the United States and Canada, said in comments that “it is unsure if existing rules governing FM broadcast in conjunction with the rules proposed are sufficient to protect aviation use of the adjacent ARNS band.” The group said it filed its comments only after consulting aviation experts, including those at the Federal Aviation Administration, about the digital power increase proposal.
NAB in its most recent comments confirms it is in talks with AIA and the General Aviation Manufacturers Association.
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Broadcasters “take seriously preliminary analyses suggesting sufficient potential threat of harmful interference to aeronautical systems,” the NAB said in reply comments to the FCC. However, NAB told the agency it is not aware of any reports of interference to navigational aid receivers from FM digital radio transmissions during the 12-year period [since FM stations were first permitted to operate digital facilities].
Broadcast groups, including iHeartMedia, Cumulus Media, Beasley Media Group and Audacy, have given their full backing to the commission’s proposal to give more digital FM stations the ability to increase their power. Comments on the FCC’s “Modifying Rules for FM Terrestrial Digital Audio Broadcasting Systems” can be read online at the FCC’s website.
