§  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 § § 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
   § § 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]