1. (a) Except as provided in paragraph (f) of this section, the co-polarization gain of any earth station antenna operating in the FSS and transmitting to a GSO satellite, including earth stations providing feeder links for satellite services other than FSS, may not exceed the following limits:

   1. (1) In the plane tangent to the GSO arc, as defined in § 25.103, for earth stations not operating in the conventional Ku-band, the 24.75-25.25 GHz band, or the 27.5-30 GHz band:

      29-25log10θ	dBi	for 1.5° ≤ θ ≤ 7°.
      8	dBi	for 7° < θ ≤ 9.2°.
      32-25log10θ	dBi	for 9.2° < θ ≤ 48°.
      −10	dBi	for 48° < θ ≤ 180°.

      Where θ is the angle in degrees from a line from the earth station antenna to the assigned orbital location of the target satellite, and dBi refers to dB relative to an isotropic radiator. This envelope may be exceeded by up to 3 dB in 10% of the range of θ angles from ±7-180°, and by up to 6 dB in the region of main reflector spillover energy.

   2. (2) In the plane tangent to the GSO arc, for earth stations operating in the conventional Ku-band:

      29-25log10θ	dBi	for 1.5° ≤ θ ≤ 7°.
      8	dBi	for 7° < θ ≤ 9.2°.
      32-25log10θ	dBi	for 9.2° < θ ≤ 19.1°.
      0	dBi	for 19.1° < θ ≤ 180°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 3 dB in 10% of the range of θ angles from ±7-180°, and by up to 6 dB in the region of main reflector spillover energy.

   3. (3) In the plane tangent to the GSO arc, for earth stations operating in the 24.75-25.25 GHz or 27.5-30 GHz bands:

      29-25log10θ	dBi	for 2° ≤ θ ≤ 7°.
      8	dBi	for 7° < θ ≤ 9.2°.
      32-25log10θ	dBi	for 9.2° < θ ≤ 19.1°.
      0	dBi	for 19.1° < θ ≤ 180°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 3 dB in 10% of the range of θ angles from ±7-180°, and by up to 6 dB in the region of main reflector spillover energy.

   4. (4) In the plane perpendicular to the GSO arc, as defined in § 25.103, for earth stations not operating in the conventional Ku-band, the 24.75-25.25 GHz band, or the 27.5-30 GHz band:

      32-25log10θ	dBi	for 3° < θ ≤ 48°.
      −10	dBi	for 48° < θ ≤ 180°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 6 dB in 10% of the range of θ angles from ±3-180°, and by up to 6 dB in the region of main reflector spillover energy.

   5. (5) In the plane perpendicular to the GSO arc, for earth stations operating in the conventional Ku-band:

      Outside the main beam, the gain of the antenna shall lie below the envelope defined by:

      32-25log10θ	dBi	for 3° < θ ≤ 19.1°.
      0	dBi	for 19.1° < θ ≤ 180°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 6 dB in 10% of the range of θ angles from ±3-180°, and by up to 6 dB in the region of main reflector spillover energy.

   6. (6) In the plane perpendicular to the GSO arc, for earth stations operating in the 24.75-25.25 GHz or 27.5-30 GHz bands:

      32-25log10θ	dBi	for 3.5° < θ ≤ 7°.
      10.9	dBi	for 7° < θ ≤ 9.2°.
      35-25log10θ	dBi	for 9.2° < θ ≤ 19.1°.
      3	dBi	for 19.1° < θ ≤ 180°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 6 dB in 10% of the range of θ angles from ±3-180°, and by up to 6 dB in the region of main reflector spillover energy.

2. (b) Except as provided in paragraph (f) of this section, the off-axis cross-polarization gain of any antenna used for transmission from an FSS earth station to a GSO satellite, including earth stations providing feeder links for satellite services other than FSS, may not exceed the following limits:

   1. (1) In the plane tangent to the GSO arc, for earth stations not operating in the 24.75-25.25 GHz or 27.5-30 GHz bands:

      19-25log10θ

      dBi

      for 1.8° < θ ≤ 7°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section.

   2. (2) In the plane perpendicular to the GSO arc, for earth stations not operating in the 24.75-25.25 GHz or 27.5-30 GHz bands:

      19-25log10θ

      dBi

      for 3° < θ ≤ 7°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section.

   3. (3) In the plane tangent to the GSO arc or in the plane perpendicular to the GSO arc, for earth stations operating in the 24.75-25.25 GHz or 27.5-30 GHz bands:

      19-25log10θ

      dBi

      for 2° < θ ≤ 7°.

      Where θ and dBi are as defined in paragraph (a)(1) of this section.

3. (c)

   1. (1) An earth station licensed for operation with a GSO FSS space station or registered for reception of transmissions from such a space station pursuant to § 25.115(b)(1) and (b)(3) is not entitled to protection from interference from authorized operation of other stations that would not cause harmful interference to that earth station if it were using an antenna with receive-band gain patterns conforming to the levels specified in paragraphs (a) and (b) of this section.
   2. (2) A 17/24 GHz BSS telemetry earth station is not entitled to protection from harmful interference from authorized space station operation that would not cause harmful interference to that earth station if it were using an antenna with receive-band gain patterns conforming to the levels specified in paragraphs (a) and (b) of this section. Receive-only earth stations in the 17/24 GHz BSS are entitled to protection from harmful interference caused by other space stations to the extent indicated in § 25.224.
4. (d) [Reserved]
5. (e) An earth station using asymmetrical antennas without skew angle adjustment capability must comply with the gain values specified in paragraph (a)(1) of this section, in the plane orthogonal to the to the main plane of the antenna, or, alternatively, in the plane corresponding to the maximum skew angle experienced at any location at which the earth station may be located.
6. (f) A GSO FSS earth station with an antenna that does not conform to the applicable standards in paragraphs (a) and (b) of this section will be authorized only if the applicant demonstrates that the antenna will not cause unacceptable interference. This demonstration must show that the transmissions of the earth station comport with the requirements in § 25.218 or the applicant must demonstrate that the operations of the earth station have been coordinated under § 25.220.
7. (g) [Reserved]

8. (h) The gain of any transmitting antenna in a gateway earth station communicating with NGSO FSS satellites in the 10.7-11.7 GHz, 12.75-13.15 GHz, 13.2125-13.25 GHz, 13.8-14.0 GHz, and/or 14.4-14.5 GHz bands must lie below the envelope defined as follows:

   29-25log10 (θ)	dBi	for 1° ≤ θ ≤ 36°.
   −10	dBi	for 36° ≤ θ ≤ 180°.

   Where θ and dBi are as defined in paragraph (a)(1) of this section. This envelope may be exceeded by up to 3 dB in 10% of the range of θ angles from ±7-180°.

[48 FR 40255, Sept. 6, 1983, as amended at 50 FR 2675, Jan. 18, 1985; 50 FR 39004, Sept. 26, 1985; 58 FR 13420, Mar. 11, 1993; 66 FR 10630, Feb. 16, 2001; 70 FR 32255, June 2, 2005; 72 FR 50029, Aug. 29, 2007; 73 FR 70901, Nov. 24, 2008; 74 FR 57099, Nov. 4, 2009; 78 FR 8427, Feb. 6, 2013; 78 FR 14927, Mar. 8, 2013; 79 FR 8322, Feb. 12, 2014; 81 FR 55336, Aug. 18, 2016; 83 FR 34491, July 20, 2018; 84 FR 53655, Oct. 8, 2019; 85 FR 44787, July 24, 2020; 87 FR 72406, Nov. 25, 2022]