The Federal Communications Commission likes the idea of giving U.S. stations on the AM band an option to turn off their analog transmissions and instead use only HD Radio. It recently said it would consider a Notice of Proposed Rulemaking recommending that change. Now the commission has officially done so.

The vote was unanimous, though at least one commissioner expressed concerns over the details of technical standards.

While the decision to issue the NPRM is not surprising, given the announcement of a couple of weeks ago, the vote seems to mark a significant advance toward an outcome where AM owners would have the digital choice. Only one U.S. radio station, owned by Hubbard Radio, operates full-time in all-digital, and does so under special temporary authority.

Advocates think having an all-digital option would be a boon to AM stations, many of which are troubled by economic challenges, band noise and lack of listener interest. Some see it as a logical addition to the AM revitalization effort, bringing benefits like metadata displays that most AM stations currently don’t have, in addition to better sound quality. And some observers, if fewer in number, wonder whether widespread migration to all-digital could substantially revitalize the AM band someday, making it prime spectrum real estate again.

Anecdotally, some critics have worried that a change that would make most existing receivers unable to hear a given radio station is premature, and/or they have voiced worries over the interference implications. That’s a touchy subject, given HD Radio’s less than stellar reputation among AM engineers, dating to the early days of putting hybrid digital on AM. The NPRM process should give more insight into what opposition may exist, if any, and from whom. It should tell us more about how AM owners themselves, big and small, come down on the idea.

“Many AM stations experience interference from electronic devices and other sources that affects audio quality,” the FCC stated in its announcement. “All-digital broadcasting offers AM broadcasters the potential to improve their signal quality and area of listenable coverage, as well as offer additional services that FM broadcasters currently offer, such as song and artist identification. It also holds the potential to allow AM stations to increase their programming options to include music formats.”

In the NPRM the FCC also proposes establishing operating parameters for all-digital stations, to minimize risk of interference; and it proposed adopting what it called the “industry-approved standard” for hybrid and all-digital broadcasting, meaning HD Radio.

[Read: Downs Hails FCC Announcement on All-Digital]

The National Association of Broadcasters applauded the move and said in its statement that “many” AM broadcasters are exploring the potential benefits.

Commissioner Michael O’Rielly has been particularly involved in issues involving the radio industry. Reacting to the vote, O’Rielly noted that he’d participated in a Texas Association of Broadcasters event with Bryan Broadcasting Corp.’s Ben Downs, an ardent supporter of AM revitalization and the person who petitioned the FCC to get going on this topic earlier this year.

“Assuming this item goes to final order, it remains to be seen whether digital AM signals will ever catch on with manufacturers, and more importantly, listeners, or serve as a significant factor in the band’s revitalization,” O’Rielly wrote after the vote.

“But our record clearly demonstrates that many in the industry would very much like to at least have a chance to test this approach, without having to obtain an experimental license. We need to give them that opportunity.”

O’Rielly did sound a note of caution. “When it comes to adopting specific technical standards, I do continue to have serious reservations regarding this approach, as the commission also adopted specific standards in the early 2000s. That said, on this and other questions, I will follow the comments received closely and look forward to seeing whether the option to transition to all-digital modes does, in fact, allow stations to have a greater and more effective reach among the listening public.”

Radio World explored the possible implications of this last March; read the ebook here.