Sec.  73.404   Interim hybrid 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  Sec. 73.1620, may
   commence interim hybrid IBOC DAB operation with digital facilities which
   conform to the technical specifications specified for hybrid DAB operation
   in the First Report and Order in MM Docket No. 99–325. AM and FM stations
   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, AM licensees may, upon notification to the Commission,
   reduce the power of the primary DAB sidebands by up to 6 dB. 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.

   (e) Licensees must provide notification to the Commission in Washington, DC,
   within 10 days of commencing IBOC digital operation. The notification must
   include the following information:

   (1) Call sign and facility identification number of the station;

   (2) Date on which IBOC operation commenced;

   (3) Certification that the IBOC DAB facilities conform to permissible hybrid
   specifications;

   (4) Name and telephone number of a technical representative the Commission
   can call in the event of interference;

   (5)  Certification that the analog effective radiated power remains as
   authorized;

   (6) Transmitter power output; if separate analog and digital transmitters
   are used, the power output for each transmitter;

   (7)  If  applicable,  any reduction in an AM station's primary digital
   carriers;

   (8) If applicable, the geographic coordinates, elevation data, and license
   file number of the auxiliary antenna employed by an FM station as a separate
   digital antenna;

   (9) If applicable, for FM systems employing interleaved antenna bays, a
   certification that adequate filtering and/or isolation equipment has been
   installed to prevent spurious emissions in excess of the limits specified in
    Sec. 73.317;

   (10) A certification that the operation will not cause human exposure to
   levels of radio frequency radiation in excess of the limits specified in
    Sec. 1.1310  of  this chapter and is therefore categorically excluded from
   environmental processing pursuant to  Sec. 1.1306(b) of this chapter. Any station
   that cannot certify compliance must submit an environmental assessment
   (“EA”)  pursuant  to  Sec. 1.1311 of this chapter and may not commence IBOC
   operation until such EA is ruled upon by the Commission.

Subpart D—Noncommercial Educational FM Broadcast Stations

   Source:    28 FR 13651 , Dec. 14, 1963. Redesignated at  72 FR 45692 , Aug. 15,
   2007.