Sec.  27.1221   Interference protection.

   (a)  Interference  protection  will  be  afforded  to BRS and EBS on a
   station-by-station basis based on the heights of the stations in the LBS and
   UBS  and also on height benchmarking, although the heights of antennas
   utilized are not restricted.

   (b) Height Benchmarking. Height benchmarking is defined for pairs of base
   stations, one in each of two proximate geographic service areas (GSAs). The
   height benchmark, which is defined in meters (hbm) for a particular base
   station relative to a base station in another GSA, is equal to the distance,
   in kilometers, from the base station along a radial to the nearest point on
   the GSA boundary of the other base station squared (Dkm^2 ) and then divided
   by  17.  That  is,  hb (m) = Dkm^2 /17. A base station antenna will be
   considered to be within its applicable height benchmark relative to another
   base station if the height in meters of its centerline of radiation above
   average elevation (HAAE) calculated along the straight line between the two
   base stations in accordance with  Sec.  Sec. 24.53(b) and (c) of this chapter does not
   exceed the height benchmark (hbm). A base station antenna will be considered
   to exceed its applicable height benchmark relative to another base station
   if the HAAE of its centerline of radiation calculated along the straight
   line between the two base stations in accordance with  Sec.  Sec. 24.53(b) and (c) of
   this chapter exceeds the height benchmark (hb[m]).

   (c) Protection for Receiving Antennas not Exceeding the Height Benchmark.
   Absent  agreement  between  the  two  licensees  to the contrary, if a
   transmitting antenna of one BRS/EBS licensee's base station exceeds its
   applicable height benchmark and such licensee is notified by another BRS/EBS
   licensee that it is generating an undesired signal level in excess of −107
   dBm/5.5 megahertz at the receiver of a co-channel base station that is
   within  its applicable height benchmark, then the licensee of the base
   station that exceeds its applicable height benchmark shall either limit the
   undesired  signal  at  the  receiver  of the protected base station to
   −107dBm/5.5 megahertz or less or reduce the height of its transmission
   antenna  to no more than the height benchmark. If the interfering base
   station has been modified to increase the EIRP transmitted in the direction
   of  the  protected  base station, it shall be deemed to have commenced
   operations on the date of such modification. Such corrective action shall be
   completed no later than:

   (i) 24 hours after receiving such notification, if the base station that
   exceeds its height benchmark commenced operations after the station that is
   within its applicable height benchmark; or

   (ii) 90 days after receiving such notification, if the base station that
   exceeds its height commenced operations prior to the station that is within
   its  applicable height benchmark. For purposes of this section, if the
   interfering base station has been modified to increase the EIRP transmitted
   in the direction of the victim base station, it shall be deemed to have
   commenced operations on the date of such modification.

   (d) No Protection from a Transmitting Antenna not Exceeding the Height
   Benchmark. The licensee of a base station transmitting antenna less than or
   equal to its applicable height benchmark shall not be required pursuant to
   paragraph (c) of this section to limit that antennas undesired signal level
   to −107dBm/5.5 megahertz or less at the receiver of any co-channel base
   station.

   (e) No Protection for a Receiving-Antenna Exceeding the Height Benchmark.
   The licensee of a base station receive antenna that exceeds its applicable
   height benchmark shall not be entitled pursuant to paragraph (c) of this
   section to insist that any co-channel base station limit its undesired
   signal level to −107dBm/5.5 megahertz or less at the receiver.

   (f) Information Exchange. A BRS/EBS licensee shall provide the geographic
   coordinates, the height above ground level of the center of radiation for
   each transmit and receive antenna, and the date transmissions commenced for
   each of the base stations in its GSA within 30 days of receipt of a request
   from a co-channel BRS/EBS licensee with an operational base station located
   in a proximate GSA. Information shared pursuant to this section shall not be
   disclosed to other parties except as required to ensure compliance with this
   section.

   [ 69 FR 72034 , Dec. 10, 2004, as amended at  70 FR 1190 , Jan. 6, 2005;  71 FR 35191 , June 19, 2006;  73 FR 26041 , May 8, 2008]