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Broadcasters Voice Support for FM Digital Power Increase

Petition calls for first power boost in more than a decade

Several large radio broadcast companies have voiced support for a proposal that would amend FCC rules governing in-band/on-channel (IBOC) digital radio broadcasting in the United States to allow at least some HD Radio stations to operate at higher power levels.

A petition from the National Association of Broadcasters and Xperi asks the FCC to adopt an updated formula to determine maximum power levels. The move would allow more HD Radio stations to increase digital power over the currently authorized digital ERP of -14 dBc, without need for separate FCC authorization.

Currently, FCC rules allow digital stations that meet certain guidelines to operate at ten percent of analog power. 

Xperi and the NAB believe that higher power will improve digital FM coverage and digital FM signal penetration of buildings while minimizing interference to adjacent-channel stations.

The commission combined the NAB and Xperi petition with a second filed in 2019 by them along with NPR — to permanently authorize FM stations to use HD Radio with asymmetric sideband power levels without FCC experimental authorization.

Beasley Media Group says it supports both petitions and believes adoption of the proposals would benefit consumers, broadcasters and the commission itself. The radio broadcaster told the FCC it sees no downside to adjusting the formula for digital power levels while also permitting blanket authorization of asymmetric sideband operation.

“Since 2011, numerous additional studies have examined the potential of asymmetric sideband operation to help digital signals better replicate analog contours and penetrate better into buildings,” Beasley commented. “These studies have consistently concluded that authorizing asymmetric sidebands on a blanket basis would significantly increase the number of stations eligible to boost power and improve their coverage without causing new host analog or adjacent channel interference.”

The broadcaster also told the FCC it has operated WCSX(FM) in Birmingham, Mich., with asymmetric levels in digital sidebands on an experimental basis since 2015. “The results have been uniformly positive. Asymmetric digital operation has noticeably improved the stability and robustness of WCSX’s digital signal. At no point during this lengthy period of operation has WCSX received a single report of interference to any co- and/or adjacent- channel FM station.”

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Cox Media Group (CMG), which owns and operates 52 radio stations across the U.S., told the FCC it supports “swift grant of both petitions as the next step in the technological advancement of the radio industry.”

“A consensus has developed in the radio industry that existing rules on digital FM power levels overstate the amount of protection adjacent analog stations require,” CMG commented. “The logical conclusion from this review is that many stations could increase digital power on at least one sideband without creating harmful interference to adjacent analog stations.”

National Public Radio told the FCC it still supports the 2019 proposal, which asks for new rules to give stations blanket authorization to originate digital transmissions at different power levels on a station’s upper and lower digital sideband. While NPR does support the most recent petition from NAB and Xperi, it asks the FCC to include assurances that any new rules adopted protect existing operations of incumbent stations.

NPR told the FCC: “The commission should require the licensee of any station increasing its FM digital sideband power levels to notify the licensees of adjacent stations at least 30 days before the power increase. A notification requirement will make adjacent stations aware of a source of potential new interference, thus protecting stations operating at lower power levels.”

However, the pubcaster says it is not asking that adjacent neighbors be provided a mechanism for objecting to the power increase, but a “pre-notification would help a station be prepared to identify interference once the change is made.”   

LPFM advocate REC Networks in general supports HD Radio technology, but does cite instances of LPFM stations and other facilities reporting “HD noise” related interference received on first-adjacent stations carrying HD in its FCC comments.

“We are also cognizant to reports of what we call HD Hijack where a distant full-service FM station is operating HD Radio cause a more local signal not operating HD Radio, such as LPFM stations, to have their main analog stream be completely interrupted by the distant FM station on HD radio receivers that detect the digital carrier operating from the distant FM station,” REC told the FCC. “We note though that HD Hijack appears to be isolated to a few small situations.”

Michele Bradley, founder of REC Networks, concedes in her letter to the FCC the two proposals “are a step in the right direction.”

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The commission originally authorized FM stations to operate with digital ERP equal to 1 percent of analog power or –20 dBc. In 2010 it allowed stations to operate at –14 dBc but to allow stations that meet certain guidelines to increase to –10 dBc, or 10 percent of analog power.

In some cases, to operate above –14 dBc, stations must submit a request with an analysis of its potential to cause interference to adjacent-channel analog signals. Stations must use technical formula developed by National Public Radio and supported by Xperi predecessor iBiquity Digital.

Xperi and NAB say this approach was intentionally conservative and can be loosened based on field experience. 

In its petition, NAB and Xperi cited field tests using pubcaster WNYC(FM), and Audacy stations WZMX(FM) and WIP(FM), which were conducted with FCC experimental authority to determine if the Audacy stations could operate at the proposed higher power without creating interference to first-adjacent channel WNYC.

Separate tests in Connecticut and New Jersey determined “there was no significant change or degradation of the desired WNYC signal” as the Audacy stations raised power.

There are approximately 2,600 FM stations using HD Radio in the United States, according to Xperi.

Reply comments in Docket 22-405 are due Feb. 13. Comments can be filed in the FCC’s Electronic Comment Filing System.