§  73.404   IBOC DAB operation.

   (a) The licensee of an AM or FM station, or the permittee of a new AM
   or FM station which has commenced program test operation pursuant to
   § 73.1620, may commence hybrid IBOC DAB operation with digital
   facilities which conform to the technical specifications specified for
   hybrid DAB operation in the (2002) First Report and Order in MM Docket
   No. 99-325, as revised in the Media Bureau's subsequent Order in MM
   Docket No. 99-325. In addition, the licensee of an AM station, or the
   permittee of a new AM station that has commenced program test authority
   pursuant to § 73.1620, may, with reasonable notice to listeners,
   commence all-digital IBOC operation with digital facilities that
   conform to the requirements set out in the (2020) Report and Order in
   MB Docket No. 19-311 and MB Docket No. 13-249. An AM or FM station may
   transmit IBOC signals during all hours for which the station is
   licensed to broadcast.

   (b) In situations where interference to other stations is anticipated
   or actually occurs, hybrid AM licensees may, upon notification to the
   Commission, reduce the power of the primary DAB sidebands by up to 6
   dB. All-digital AM licensees, may, upon notification to the Commission,
   reduce the power of the secondary and tertiary sidebands by up to 6 dB,
   even if doing so results in non-compliance with § 73.1560(a)(1). Any
   greater reduction of sideband power requires prior authority from the
   Commission via the filing of a request for special temporary authority
   or an informal letter request for modification of license.

   (c) Hybrid IBOC AM stations must use the same licensed main or
   auxiliary antenna to transmit the analog and digital signals.

   (d) FM stations may transmit hybrid IBOC signals in combined mode;
   i.e., using the same antenna for the analog and digital signals; or may
   employ separate analog and digital antennas. Where separate antennas
   are used, the digital antenna:

   (1) Must be a licensed auxiliary antenna of the station;

   (2) Must be located within 3 seconds latitude and longitude from the
   analog antenna;

   (3) Must have a radiation center height above average terrain between
   70 and 100 percent of the height above average terrain of the analog
   antenna.

   [ 72 FR 45692 , Aug. 15, 2007, as amended at  75 FR 17877 , Apr. 8, 2010;
    85 FR 18151 , Apr. 1, 2020;  85 FR 78027 , Dec. 3, 2020]