Comments have been invited on an NAB/SBE proposal aimed at (slightly) improving the audio quality on the TIS without interfering with AM stations.

Last July we blogged about changes the Commission had adopted to improve Travelers’ Information Stations (TIS). At that time, the FCC proposed another fairly drastic change – the elimination of certain filtering requirements – that might potentially improve the service. The proposal went farther than some commenters thought advisable, which prompted them to propose a more moderate approach and, in response, the Public Safety and Homeland Security Bureau has now issued a Public Notice seeking further comment. (The Bureau probably could have skipped this step, but this writer thinks it’s a good thing they didn’t.)

TIS are low-power AM stations broadcasting information of interest to motorists, including traffic and road conditions, travel advisories, hazards, directions and the like. Each station covers only a small geographic area, most commonly along major highways and near tourist destinations.

AM service is notoriously interference-prone, with TIS as a potential source. The interference occurs because of the “sideband” portion of the TIS-transmitted AM signal. Excessively wide sidebands can cross over into another station’s channel, causing interference to that station. With AM stations – whose signals, particularly at night, can extend for hundreds of miles – this can cause big problems.

To reduce interference, the rules have historically required the filtering of TIS audio frequencies above 3 kHz. TIS are uniquely suited to filtering because they (theoretically) carry only voice transmissions, not music or other sounds. With the currently required filtering, music sounds awful, but voice is generally comprehensible (if not mellifluous) – roughly the same quality as wireline telephones. For TIS stations, on which non-voice transmissions are generally barred, that’s all you really need: the goal is to have listeners understand the words, not be entertained.

But at night and in areas of difficult terrain, “generally comprehensible” sometimes isn’t really. To improve the TIS, the FCC proposed eliminating the filtering requirement altogether.

That proposal got multiple positive responses, but not everyone was on board. The National Association of Broadcasters (NAB) and the Society of Broadcast Engineers (SBE), in particular, pushed back, proposing instead that the filter requirement be preserved but relaxed from 3 kHz to 5 kHz. A bump to 5 kHz would make the voice sound better, NAB/SBE argued, while still providing reasonable protection to nearby AM services.  And since TIS are deemed a secondary service, preventing interference is supposed to be paramount.

It seems like a good solution: the (objectively) poor audio quality on TIS gets better, but it doesn’t substantially increase the risk of interference. Win-win. Even the American Association of Information Radio Operators, whose petition initiated the original rulemaking to improve the TIS, supports the NAB/SBE proposal (although the AAIRO did propose a couple of additional tweaks to the NAB/SBE approach).

There is also the issue of the “steepness” of the filters. No filter is perfect: a 5 kHz filter will cull out only part of the signal below 5 kHz and leave some above it. The FCC proposed one profile, but it’s possible that another might be better, or cheaper, since steeper filters tend to be more expensive to implement. We’ll see what the comments say.

There are implementation questions on the table. Where exactly should the filters be installed in the TIS transmission system? If the filtering requirement is modified, or eliminated, would TIS licensees be required to recertify their transmitters? Since any relaxation of the 3 kHz rule would presumably be intended to benefit TIS, could a TIS licensee decline to make the change if the station were to determine, for example, that the change would be too expensive?

Since it has already solicited comments on changing the filtering, the Commission might have been able simply to issue an order straightaway adopting the NAB/SBE proposal. Instead, they have given the public another opportunity to comment on the possible new direction proposed by NAB/SBE.

Good for them. This is the way the system is supposed to work: the FCC should be sure to afford plenty of opportunity for input on what they’re considering. Here, in response to a suggestion made by commenters in a rulemaking, the Commission tentatively embraced the suggestion and solicited  comment on it, only to receive an alternate suggestion on which it has now sought further comments. It’s difficult to imagine anyone accusing the FCC of making some backroom deal with one or another established player in a way that might undermine a public safety service: the FCC has given the users and operators of the TIS a chance to weigh in on this new 5 kHz proposal, and if it turns out the 5 kHz Great Compromise isn’t so Great, ideally that determination will keep the Commission from taking an ill-advised turn. Sure, it might delay things by a few months, but in this case, doing it right is worth the delay.

Comments in response to the Bureau’s public notice are due by May 16, 2014; reply comments are due by June 2. Comments may be uploaded through the FCC’s ECFS online filing system here; enter them in Proceeding Number 09-19.