The Federal Communications Commission (“FCC”) has invited comments on whether it should allow AM radio broadcast stations to abandon their analog signals in favor of an all-digital signal format. Preliminary tests have shown that all-digital signals provide improved audio quality and immunity from interference. While the FCC does not propose to require any AM station to convert to all-digital operation, it has asked whether it should allow digital conversion on a voluntary basis.

We are not talking about the hybrid type of operation that digital FM and AM stations currently have, where they transmit both analog and digital signals, and the type of signal used by each listener is determined by that person’s receiver, which processes a digital signal if that signal is strong enough but otherwise defaults to analog reception. The proposal is to allow AM stations to eliminate their analog signal altogether and to broadcast only a digital signal. The proposal does not extend to FM broadcast stations, which would remain restricted to all-analog or hybrid signal formats.

All-digital AM transmission has been tested extensively by station WWFD in Frederick, Maryland. The results have been appealing, although there are still a few kinks to work out with respect to the reliability of metadata that enable a receiver to display song and artist names and other short digital messages. However, the FCC’s main concerns are controlling interference, maintaining the Emergency Alert System (“EAS”) and not depriving listeners of service they are accustomed to receiving. Since adoption of an all-digital format would be voluntary, it would be up to each station to decide when digital technology is really ready for prime time.

While it appears that all-digital AM radio will cause less adjacent-channel interference than analog, co-channel interference may be another story. The FCC asks for comments on what digital power levels it should authorize, what impact directional antennas will have on digital signal propagation, what will happen to skywave signals that travel long distances at night, and whether converted analog transmitters will be able to confine their signals within the rather stringent emissions mask specified in the digital standard. Spectrum efficiency is also an issue and may be improved if the overall bandwidth of an AM signal can be reduced from the present 20 kHz to only 10 kHz. To get benefits without detriments, the FCC suggests a carrier frequency tolerance of only 1 Hz (yes, that is one Hertz), which seems much more precise than any broadcaster has had to achieve in the past.

Converting AM stations to all-digital operation could raise problems with EAS, which relies on a small number of strong AM stations to serve as primary entry points into the national message distribution system. What will happen if those signals become digital and no longer activate EAS receivers? Will there be more interference to Travelers’ Information Stations, those little localized AM signals used on highways and at places like airports and national parks to inform drivers of conditions they are approaching? And are there listeners who depend on analog AM radio and will lose important services if they do not have digital receivers, or are the days of AM dependency essentially over because more than half of the nation’s AM stations now rebroadcast their programming through FM translators?

Finally, there are cost issues. While the digital AM standard has some flexibility, the FCC wants all digital signals to be receivable by all digital receivers. In the end, that means that stations wishing to convert to digital operation will have to deal with licensing costs on top of equipment costs. The only currently available digital system is proprietary and charges fees that start at $10,000 for one channel and include additional revenue-based amounts for stations operating more than one channel. The system was originally developed by iBiquity Digital Corporation. iBiquity was acquired by DTS, Inc. in 2015, and DTS, Inc. was acquired by Xperi Corporation acquired DTS in 2016; so Xperi is now the licensing entity. Licensing fees have discouraged some FM stations from adding a digital component to their signal. The FCC asks whether the fees will be a barrier that will prevent smaller stations from converting to digital and will ultimately leave those stations less able to compete with large station owners.

You can read the full text of the FCC’s proposals here. Comments will be due 60 days after publication of the Notice of Proposed Rulemaking (NPRM) in the Federal Register. Check back with to find out when the deadline is announced.