§  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
   § 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, as revised in the Media Bureau's subsequent Order in MM Docket
   No. 99-325. FM stations are permitted to operate with hybrid digital
   effective radiated power equal to one percent ( -20 decibels below
   carrier (dBc)) of authorized analog effective radiated power and may
   operate with up to ten percent ( -10 dBc) of authorized analog
   effective radiated power in accordance with the procedures set forth in
   the Media Bureau's Order in MM Docket No. 99-325. 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, 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) FM digital effective radiated power used and certification that the
   FM 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 § 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 § 1.1310 of this chapter and is therefore categorically
   excluded from environmental processing pursuant to § 1.1306(b) of this
   chapter. Any station that cannot certify compliance must submit an
   environmental assessment ("EA") pursuant to § 1.1311 of this chapter
   and may not commence IBOC operation until such EA is ruled upon by the
   Commission.

   [ 72 FR 45692 , Aug. 15, 2007, as amended at  75 FR 17877 , Apr. 8, 2010]

Subpart D--Noncommercial Educational FM Broadcast Stations

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