HD Radio’s power ceiling is back in front of the FCC. After meeting with Media Bureau staff, NAB and Xperi are pressing the agency to clarify whether FM stations may run stronger digital signals, a question with consequences for coverage area and analog dropouts.
In a November 2 ex parte filing, NAB said it, Xperi, and the National Radio Systems Committee met with FCC Media Bureau staff on October 29. The group asked the FCC to clarify the rule so it matches earlier FCC letters that let stations use more digital power.
Under the rule, stations may use up to -14 dBc of digital power, and no station may go above -10 dBc. NAB says FCC letters in 2014 and 2021 relied on NRSC power tables that let some stations go higher. A February 3, 2025 letter to KBSU instead capped the station at 1.75 kW (-10 dBc).
NAB and Xperi say stations using certain HD Radio modes are now held below the power they need, which means a smaller digital coverage area and more times when the radio switches back to analog. They also say running above -10 dBc under the NRSC table does not meaningfully harm stations on the next channel over and has no effect two channels over.
In August 2023, the FCC advanced two proposals to change how FM stations calculate maximum digital power and to let stations run their digital sidebands at different power levels. RBR+TVBR reported in September 2024 that the FCC put off acting on a proposal about maximum FM digital power when it issued its First Report and Order on digital FM.
NAB VP of Advanced Engineering David Layer also gave the FCC an update on talks with aviation groups studying how HD Radio signals affect aviation navigation radio spectrum. NAB said those groups have finished compatibility testing and expects to meet with them again within a month to discuss their findings.
NAB Associate General Counsel Larry Walke wrote in the filing that the group described “a seeming change in 2025 that limits the ability of certain digital radio stations to optimize operations.”
