§  101.115   Directional antennas.

   (a) Unless otherwise authorized upon specific request by the applicant,
   each station authorized under the rules of this part must employ a
   directional antenna adjusted with the center of the major lobe of
   radiation in the horizontal plane directed toward the receiving station
   with which it communicates: provided, however, where a station
   communicates with more than one point, a multi- or omni-directional
   antenna may be authorized if necessary. New Periscope antenna systems
   will not, under ordinary circumstances, be authorized.

   (b) Fixed stations (other than temporary fixed stations and DEMS nodal
   stations) operating at 932.5 MHz or higher must employ transmitting and
   receiving antennas (excluding second receiving antennas for operations
   such as space diversity) meeting the appropriate performance Standard A
   indicated below, except that in areas not subject to frequency
   congestion, antennas meeting performance Standard B may be used,
   subject to the requirements set forth in paragraph (d) of this section.
   Licensees shall comply with the antenna standards table shown in this
   paragraph in the following manner:

   (1) With either the maximum beamwidth to 3 dB points requirement or
   with the minimum antenna gain requirement; and

   (2) With the minimum radiation suppression to angle requirement.

   Antenna Standards
   Frequency (MHz) Category Maximum beamwidth to 3 dB points^1(included
   angle in degrees) Minimum antenna gain (dbi) Minimum radiation
   suppression to angle in degrees from centerline of main beam in
   decibels
   5° to10° 10° to 15° 15° to 20° 20° to 30° 30° to 100° 100° to 140° 140°
   to 180°
   932.5 to 935 A 14.0 n/a n/a 6 11 14 17 20 24
      B 20.0 n/a n/a n/a 6 10 13 15 20
   941.5 to 944 A 14.0 n/a n/a 6 11 14 17 20 24
      B 20.0 n/a n/a n/a 6 10 13 15 20
   952 to 960^2,3 A 14.0 n/a n/a 6 11 14 17 20 24
      B 20.0 n/a n/a n/a 6 10 13 15 20
   1,850 to 2,500^4 A 5.0 n/a 12 18 22 25 29 33 39
      B 8.0 n/a 5 18 20 20 25 28 36
   3,700 to 4,200 A 2.7 36 23 29 33 36 42 55 55
      B 2.7 36 20 24 28 32 32 32 32
   5,925 to 6,425^5 A 2.2 38 25 29 33 36 42 55 55
      B 2.2 38 21 25 29 32 35 39 45
   5,925 to 6,425^6 A 2.2 38 25 29 33 36 42 55 55
      B 2.2 38 20 24 28 32 35 36 36
   6,525 to 6,875^5 A 2.2 38 25 29 33 36 42 55 55
      B 2.2 38 21 25 29 32 35 39 45
   6,525 to 6,875^6 A 1.5 n/a 26 29 32 34 38 41 49
      B 2.0 n/a 21 25 29 32 35 39 45
   10,550 to 10,680^7 A 3.5 33.5 18 24 28 32 35 55 55
      B 3.5 33.5 17 24 28 32 35 40 45
   10,565 to 10,615 n/a 360 n/a n/a n/a n/a n/a n/a n/a n/a
   10,630 to 10,680^8 n/a 3.5 34 20 24 28 32 35 36 36
   10,700–11,700^5 A 2.2 38 25 29 33 36 42 55 55
   B 3.5 33.5 17 24 28 32 35 40 45
   12,200 to 13,250^9 A 1.0 n/a 23 28 35 39 41 42 50
      B 2.0 n/a 20 25 28 30 32 37 47
   17,700 to 18,820 A 2.2 38 25 29 33 36 42 55 55
      B 2.2 38 20 24 28 32 35 36 36
   18,920 to 19,700^10 A 2.2 38 25 29 33 36 42 55 55
      B 2.2 38 20 24 28 32 35 36 36
   21,200 to 23,600^7,11 A 3.3 33.5 18 26 26 33 33 55 55
      B 3.3 33.5 17 24 24 29 29 40 50
   24,250 to 25,250^10 A 2.8 38 25 29 33 36 42 55 60
      B 2.8 38 20 24 28 32 35 36 45
   31,000 to 31,300^12,13 n/a 4.0 38 n/a n/a n/a n/a n/a n/a n/a
   38,600 to 40,000^14 A n/a 38 25 29 33 36 42 55 55
      B n/a 38 20 24 28 32 35 36 36
   71,000 to 76,000 (co-polar)^15 N/A 1.2 43 35 40 45 50 50 55 55
   71,000 to 76,000 (cross-polar)^15 N/A 1.2 43 45 50 50 55 55 55 55
   81,000 to 86,000 (co-polar)^15 N/A 1.2 43 35 40 45 50 50 55 55
   81,000 to 86,000 (cross-polar)^15 N/A 1.2 43 45 50 50 55 55 55 55
   92,000 to 95,000 N/A 0.6 50.0 36 40 45 50 55 55 55

   ^1If a licensee chooses to show compliance using maximum beamwidth to 3
   dB points, the beamwidth limit shall apply in both the azimuth and the
   elevation planes.

   ^2Except for Multiple Address System frequencies listed in
   § § 101.147(b)(1) through (b)(4), where omnidirectional antennas may be
   used.

   ^3Antennas used at outlying stations as part of a central protection
   alarm system need conform to only the following 2 standards:

   (i) The minimum on-beam forward gain must be at least 10 dBi, and

   (ii) The minimum front-to-back ratio must be at least 20 dB.

   ^4Omnidirectional antennas may be authorized in the band 2150–2160 MHz.

   ^5These antenna standards apply to all point-to-point stations
   authorized after June 1, 1997. Existing licensees and pending
   applicants on that date are grandfathered and need not comply with
   these standards.

   ^6These antenna standards apply to all point-to-point stations
   authorized on or before June 1, 1997.

   ^7Except for antennas between 140° and 180° authorized or pending on
   January 1, 1989, in the band 10,550 to 10,565 MHz for which minimum
   radiation suppression to angle (in degrees) from centerline of main
   beam is 36 decibels.

   ^8These antenna standards apply only to DEMS User Stations licensed, in
   operation, or applied for prior to July 15, 1993.

   ^9Except for Temporary-fixed operations in the band 13200–13250 MHz
   with output powers less than 250 mW and as provided in § 101.147(q), and
   except for antennas in the MVDDS service in the band 12.2–12.7 GHz.

   ^10DEMS User Station antennas in this band must meet performance
   Standard B and have a minimum antenna gain of 34 dBi. The maximum
   beamwidth requirement does not apply to DEMS User Stations. DEMS Nodal
   Stations need not comply with these standards. Stations authorized to
   operate in the 24,250–25,250 MHz band do not have to meet these
   standards, however, the Commission may require the use of higher
   performance antennas where interference problems can be resolved by the
   use of such antennas.

   ^11Except as provided in § 101.147(s).

   ^12The minimum front-to-back ratio shall be 38 dBi.

   ^13Mobile, except aeronautical mobile, stations need not comply with
   these standards.

   ^14Stations authorized to operate in the 38,600–40,000 MHz band may use
   antennas other than those meeting the Category A standard. However, the
   Commission may require the use of higher performance antennas where
   interference problems can be resolved by the use of such antennas.

   ^15Antenna gain less than 50 dBi (but greater than or equal to 43 dBi)
   is permitted only with a proportional reduction in maximum authorized
   EIRP in a ratio of 2 dB of power per 1 dB of gain, so that the maximum
   allowable EIRP (in dBW) for antennas of less than 50 dBi gain becomes
   +55−2(50–G), where G is the antenna gain in dBi. In addition, antennas
   in these bands must meet two additional standards for minimum radiation
   suppression: At angles between 1.2 and 5 degrees from the centerline of
   the main beam, co-polar discrimination must be G−28, where G is the
   antenna gain in dBi; and at angles of less than 5 degrees from the
   centerline of main beam, cross-polar discrimination must be at least 25
   dB.

   (c) The Commission shall require the replacement of any antenna or
   periscope antenna system of a permanent fixed station operating at
   932.5 MHz or higher that does not meet performance Standard A specified
   in paragraph (c) of this section, at the expense of the licensee
   operating such antenna, upon a showing that said antenna causes or is
   likely to cause interference to (or receive interference from) any
   other authorized or applied for station whereas a higher performance
   antenna is not likely to involve such interference. Antenna performance
   is expected to meet the standards of paragraph (c) of this section for
   parallel polarization. For cases of potential interference, an antenna
   will not be considered to meet Standard A unless the parallel
   polarization performance for the discrimination angle involved meets
   the requirements, even if the cross-polarization performance controls
   the interference.

   (d) In cases where passive reflectors are employed in conjunction with
   transmitting antenna systems, the foregoing paragraphs of this section
   also will be applicable. However, in such instances, the center of the
   major lobe of radiation from the antenna normally must be directed at
   the passive reflector, and the center of the major lobe of radiation
   from the passive reflector directed toward the receiving station with
   which it communicates.

   (e) Periscope antennas used at an electric power facility plant area
   will be excluded from the requirements of paragraph (c) of this section
   on a case-by-case basis where technical considerations or safety
   preclude the use of other types of antenna systems.

   (f) In the 10,700–11,700 MHz band, a fixed station may employ
   transmitting and receiving antennas meeting performance standard B in
   any area. If a Fixed Service or Fixed Satellite Service licensee or
   applicant makes a showing that it is likely to receive interference
   from such fixed station and that such interference would not exist if
   the fixed station used an antenna meeting performance standard A, the
   fixed station licensee must modify its use. Specifically, the fixed
   station licensee must either substitute an antenna meeting performance
   standard A or operate its system with an EIRP reduced so as not to
   radiate, in the direction of the other licensee, an EIRP in excess of
   that which would be radiated by a station using a Category A antenna
   and operating with the maximum EIRP allowed by the rules. A licensee or
   prior applicant using an antenna that does not meet performance
   Standard A may object to a prior coordination notice based on
   interference only if such interference would be predicted to exist if
   the licensee or prior applicant used an antenna meeting performance
   standard A.

   (g) In the event harmful interference is caused to the operation of
   other stations, the Commission may, after notice and opportunity for
   hearing, order changes to be made in the height, orientation, gain and
   radiation pattern of the antenna system.

   [ 61 FR 26677 , May 28, 1996, as amended at  62 FR 4924 , Feb. 3, 1997;  62 FR 24582 , May 6, 1997;  63 FR 6105 , Feb. 6, 1998;  65 FR 38329 , June 20,
   2000;  65 FR 59358 , Oct. 5, 2000;  67 FR 43038 , June 26, 2002;  68 FR 4957 , Jan. 31, 2003;  69 FR 3267 , Jan. 23, 2004;  70 FR 29997 , May 25,
   2005;  72 FR 55677 , Oct. 1, 2007;  73 FR 55775 , Sept. 26, 2008]