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Asymmetric IBOC Permission Process Could Be Eased

Move suggests intention to permit the technology to be used much more widely

As we first reported, the FCC could ease the permission process for FMs that want to use HD asymmetrical sideband transmission. The move suggests an intention by the commission to permit the technology to be used much more widely than it has been to date.

The commission says in a notice today that “a significant number of FMs” can’t increase HD power levels by a full 10 dB because of potential interference to nearby stations on first-adjacent channels. “If asymmetric digital sideband operation is permitted, such stations presumably could increase their digital power on the sideband away from the limiting station,” states the FCC.

IBiquity Digital and NPR had asked for the change and in October they submitted data from field trials; they say data show FM HD asymmetrical sideband transmission can improve a station’s digital coverage without causing interference.

Right now, stations that want to use asymmetrical sideband transmission need special permission. The agency tentatively has decided to modify Form FCC 335-FM, currently used for Digital Notifications, to accommodate requests for increased digital power and/or operation with asymmetric digital sideband power.

The iBiquity and NPR technical reports are available electronically from the FCC’s Electronic Comment Filing System under MM Docket No. 99-325, at, respectively.

The commission is asking for public comments on both reports, the process by which stations would notify the commission and how the notifications would be maintained in the FCC’s database.

Comments to MM Docket 99-325 are due 21 days after DA 11-1832 is published in the Federal Register.