NPR has joined an effort to revive a FCC proceeding that it says would allow radio stations to expand their digital signals’ coverage while protecting broadcasts on nearby frequencies from interference.
In a petition for rulemaking filed Monday, NPR, the National Association of Broadcasters and Xperi Corp. asked the commission to allow stations to use a technology known as “asymmetric digital sidebands” on a routine basis. Xperi and NAB have been working together on new technologies for digital radio use in cars.
Stations broadcast their digital HD Radio streams on sidebands — portions of radio spectrum that sandwich their analog signals. Because these sidebands are on the edges of a station’s signal, they have the potential to interfere with stations broadcasting on neighboring frequencies.
The FCC now authorizes stations to boost their digital power on a temporary and experimental basis, according to the petition. But when it grants such permission, it uses a calculation that assumes the sidebands are symmetric, with each broadcasting at the same power. That’s what NPR and its co-petitioners want changed.
“The use of symmetric sidebands for all calculations eliminates a viable path for many stations to increase power on at least one sideband, which would improve digital coverage,” the petitioners said in their filing. They cited a 2017 study by NAB and Xperi that found more than 4,000 stations could boost power on one sideband if the FCC allowed it.
NPR, NAB and Xperi argue that allowing asymmetric sideband power on a routine basis would “strengthen the existing digital radio ecosystem and facilitate the continued growth of digital radio.” They point out that sales of HD Radi0–enabled receivers continue to grow as more car manufacturers include the devices in new models.
According to the petition, the FCC sought comment in 2011 on a request to permanently authorize asymmetric sideband power but took no action after comments closed in January 2012. There was “virtually no opposition” to the request, the petitioners said.