On October 6, 2023, the time period for filing comments and reply comments on a Notice of Proposed Rulemaking tied to the increase of FM digital power concluded. The proceeding, initiated two months earlier, would change the methodology used by digital FM stations to determine whether they can boost their HD Radio output. It would also allow asymmetric sideband operation.
Now, the Media Bureau has confirmed the filing earlier this month of a “Petition for Clarification,” submitted jointly by the NAB and HD Radio parent Xperi Inc. Why? They detected “an important ambiguity” that requires a clear-up.
In the Petition for Clarification, filed on February 2 but not publicly shared by the FCC until today (2/21), NAB and Xperi state that they have “identified an important ambiguity that requires clarification regarding the maximum allowable operating power of a digital FM signal.”
They note that the NPRM and the Commission’s past discussions of digital power levels 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 has considered the total integrated power level for all digital carriers used to transmit MP1 standard hybrid service. NAB and Xperi note, however, that the HD Radio system is not limited to the MP1 mode, and the Commission has authorized extended hybrid modes of operation, which increase the number of digital subcarriers.
In the view of the NAB and Xperi, 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, they argue.
As such, the NAB and Xperi seek 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 73.404(e) of the Commission’s rules.
In light of this requested clarification, and to provide a complete record on the issue, the Media Bureau is seeking public comment on the proposed clarifying language from the NAB and Xperi. In addition, the Bureau notes that NAB and Xperi ask the Commission to incorporate a reference in the rules to the NRSC-5 standard, which is subject to modification, as an appropriate means to implement the proposed change. “Because it is unusual for the Commission to incorporate outside standards into its rules, commenters should offer alternative means to incorporate the proposed clarification directly into the Commission’s rules,” the Media Bureau states.
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.
