H
ere’s a fresh twist regarding the proposal that would allow more U.S. FM stations to increase HD Radio digital power levels.
The FCC Media Bureau is asking for public comments about a late-breaking request from the National Association of Broadcasters and Xperi, two of the proponents of the change.
On Feb. 2, NAB and Xperi filed a petition saying they had “identified an important ambiguity that requires clarification regarding the maximum allowable operating power of a digital FM signal.”
The NPRM and the commission’s past discussions have considered only the power level for the digital FM carriers of the primary HD Radio MP1 hybrid service mode of operation. In particular, the commission said, it has considered the total integrated power level for all digital carriers used to transmit MP1 standard hybrid service.
NAB and Xperi pointed out that HD Radio is not limited to the MP1 mode and that the commission has authorized extended hybrid modes of operation, which increase the number of digital subcarriers.
They told the FCC that the optimal operation of the extended hybrid modes requires an increase in the total integrated power above that of the MP1 mode so that all the digital carriers individually operate at the intended power.
“Otherwise, individual carriers would have to operate with less than the intended power level to keep the total integrated power at the intended level,” according to the FCC’s summary of the filing.
NAB and Xperi asked the commission to clarify the maximum digital FM power levels permitted for hybrid and extended hybrid service modes, including adding clarifying text to the NPRM and textual changes to the proposed new section of the rules. (You can read their petition here in PDF form.)
In response the Media Bureau has asked for comments on those suggestions.
The NAB and Xperi also would like the commission to incorporate a reference in the rules to the NRSC-5 standard, but the FCC says this would be unusual and asked for feedback.
“Commenters also should consider whether the additional digital power necessitated by use of extended digital modes would increase potential interference to first adjacent channel analog FM stations, to the host analog station, or to other users of the FM broadcast spectrum or adjacent to that spectrum,” the FCC continued.
It noted that the petition does not reference any technical studies of the impact of extended hybrid modes with a total integrated digital power level more than –10 dBc. “Are such studies needed to determine whether or not to adopt this proposal?”
Also, if the commission adopts this proposed change for stations operating with less than –10 dBc, should the FCC limit the total overall digital power for any station operating in extended hybrid mode to a maximum of –10 dBc? It noted that doing so would require stations that convert from MP1 to an extended hybrid mode to reduce the power of the individual subcarriers in the primary digital sidebands, in order to accommodate the power added by the extended digital sideband partitions.
“Commenters have an opportunity to suggest modifications to petitioners’ clarifying suggestions, as appropriate.” The FCC encouraged people to provide input regarding the number of stations operating in the various extended hybrid modes, including whether those stations operate at a power level with more than –14 dBc.
Comments on this new issue can be filed in the FCC’s online system. In the Proceeding field, use MB Docket No. 22-405.
