FM IBOC Power Increase Compromise Reached

by Leslie Stimson, 11.06.2009

email print rss

There’s breaking news on the HD Radio digital power front.

NPR and iBiquity Digital confirm to me that they’ve now reached a compromise on the voluntary FM IBOC power increase, something that has been on-again/off-again in the past month. The goal is to “significantly improve indoor and portable reception of HD signals,” they said.

And though I hear that staff at the Federal Communications Commission already know about the deal, the public radio network and the technology developer hope formally to discuss their recommendations with the FCC Media Bureau today (Thursday).

This news is seen as important because observers believe the commission wants to hear a unified industry recommendation. As Radio World has reported in depth, NPR has been studying the potential impact of a power hike at various levels and had voiced concerns about the effects in some circumstances. IBiquity and a group of “Joint Parties” — organizations including broadcasters, transmission manufacturers as well as NAB — also have been studying it and have been advocating a 10 dB power hike — 10 times current power — as soon as possible.

Now NPR and iBiquity will recommend that the FCC adopt a plan in which most stations — commercial and non-commercial — that want to increase FM digital power be allowed to adopt a 6 dB increase, from the current level of –20 dB to a power level of – 14 dB, as soon as authorized. So-called “Super Bs” would be treated differently.

NPR and iBiquity crafted the compromise with input from the “Joint Parties.” The latter support the agreement but don’t appear to be among the presenters to the FCC today.

To go beyond 6 dB to a 10 dB increase, stations would use spacing calculations developed by NPR Labs for stations on reserved and non-reserved FM band allocations. NPR previously had filed, and I reported on, its interim spacing calculations based on initial results of its elevated power tests conducted over the summer. NPR has now completed the study and updated those calculations. It submitted those to the FCC, along with all the recommendations, as an ex parte filing to Docket 99-325 late Wednesday. This is a simplified, less technical, version of its results; NPR intends to file the full results later this month.

How fast stations that want to go up to a full 10 dB increase could so is unclear and really up to the commission. It may feel the need to submit the issue of what to do beyond 6 dB for comment, so says Mike Starling, NPR’s vice president, chief technology officer and executive director of NPR Labs. “At that point, assuming they move forward to endorse the proposal, they will define how the notification or request process might work.”

The plan includes elements of what Starling calls a “managed power increase strategy.” The recommendations include a path for technical upgrades for items NPR really wanted, such as the development of digital FM boosters for single-frequency networks, new transmission software to enable stations to transmit the digital signal using asymetrical sidebands and a variable bit-rate coder including conditional access for stations that air radio reading services.

Concrete steps to resolve analog interference complaints regarding the 6 dB increase are included in the proposal. The parties say these steps would remediate harmful interference from any stations increasing power above the existing –20 dBc power level. I hear the compromise talks got serious right after the NAB Radio Show. During the elevated power session I covered there, Media Bureau Chief Peter Doyle told attendees it was time to give the agency recommendations because “the train is leaving the station.” It was apparent that something was going to be adopted because it was clear to the agency that more IBOC juice was needed to help reduce signal penetration issues.

What’s next?
With news of an IBOC power compromise recommendation to the FCC, IBiquity President/CEO Bob Struble and others reminded me that if the FCC does give stations the authority to increase their digital power, it will not happen overnight and certainly the technical changes associated with the rise on the transmit side need to be completed.

A timeframe for completion of technology to enable the technical changes I outlined is not set as yet, however we would probably see “major advances” on those fronts in 2010.

The software to enable a station to transmit IBOC using a different power level on each sideband, or the asymmetrical sideband method, is for the exciter, according to Struble. NPR and iBiquity would give the FCC regular updates on the proposed technology developments related to the power increase.

Also, the proposal treats Super B stations differently by limiting them to IBOC facilities based on the maximum for their class.

The actual language says: For grandfathered super-power Class B stations, the digital power levels should be limited to the higher of: (i) –20 dB relative to their analog carrier as is permitted by the current rules, or (ii) at least 10 dB below the maximum analog power authorized for this class of station as adjusted for height, absent any grandfathered super power.

Power compromise seen as ‘milestone’
NPR and iBiquity hope the FCC quickly adopts their recommendations with few if any changes.

They believe a compromise helps to show portable receiver and other device manufacturers there is a clear path to increased and more reliable digital signal coverage.

Bob Struble told me, “The Media Bureau has been patient with the industry in working through each party’s concerns. A compromise has to help move things along because the issue is not contentious anymore.”

IBiquity and the Joint Parties originally had proposed an immediate 10 dB increase. This summer, it proposed a 6 dB step in the interim as a compromise. NPR’s initial calculations would have allowed fewer stations to effect an increase and it wanted the FCC to wait until it completed its elevated power studies before the agency made a decision on the issue.

Initial NPR study results seemed to predict that short-spaced stations at the low end of the dial that are programming lightly processed music or talk would take interference hits to their analog signal, especially in a car radio, if the digital power were increased.

Mike Starling of NPR said with their new, final data, NPR Labs completed new power calculations for the spacing recommendations that would allow more stations to raise their power, especially if new methods such as asymmetrical sideband transmission, are used.

Milford Smith, vice president of radio engineering for Greater Media, one of the broadcasters that supported the increase, said the compromise is “enough to make a real difference and large enough to significantly improve the coverage of digital radio as opposed to analog.” Both Smith and Struble called the compromise a milestone.

NPR surveyed member station managers to get a handle on how many facilities might increase their digital power. Of 183 responses, 70% indicated they’d raise the IBOC power “the maximum they would be allowed to over the next year,” Starling told me.