§ 101.115 - Directional antennas.  


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  • § 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. For frequencies with a Standard B1 and a Standard B2, in order to comply with Standard B an antenna must fully meet either Standard B1 or Standard B2. 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 points1 (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 935A14.0n/an/a61114172024
    B20.0n/an/an/a610131520
    941.5 to 944A14.0n/an/a61114172024
    B20.0n/an/an/a610131520
    952 to 9602 3 A14.0n/an/a61114172024
    B20.0n/an/an/a610131520
    1,850 to 2,5004 A5.0n/a12182225293339
    B8.0n/a5182020252836
    3,700 to 4,200A2.73623293336425555
    B2.73620242832323232
    B2.23821252932353945
    5,925 to 6,4255 A2.23825293336425555
    B12.23821252932353945
    B24.13215202328296060
    6,525 to 6,8755 A2.23825293336425555
    B12.23821252932353945
    B24.13215202328296060
    6,875 to 7,125A2.23825293336425555
    B12.23821252932353945
    B24.13215202328296060
    10,550 to 10,6807 A3.533.518242832355555
    B3.533.517242832354045
    10,565 to 10,615n/a360n/an/an/an/an/an/an/an/a
    10,630 to 10,6808 n/a3.53420242832353636
    10,700-11,7005 A2.23825293336425555
    B3.533.517242832354045
    12,200 to 13,2509 A1.0n/a23283539414250
    B2.0n/a20252830323747
    17,700 to 18,820A2.23825293336425555
    B12.23820242832353636
    B23.333.518222931355555
    18,920 to 19,70010 A2.23825293336425555
    B12.23820242832353636
    B23.333.518222931355555
    21,200 to 23,6007 11 A3.333.518262633335555
    B13.333.517242429294050
    B24.530.514192224295252
    24,250 to 25,25010 A2.83825293336425560
    B2.83820242832353645
    31,000 to 31,30012 13 n/a4.038n/an/an/an/an/an/an/a
    Bn/a3820242832353636
    71,000 to 76,000 (co-polar)14 N/A12.24335404550503822283235375555
    71,000 to 76,000 (cross-polar)14 N/A12.2434550503835354042475555 5555
    81,000 to 86,000 (co-polar)14 N/A12.24335404550503822283235375555
    81,000 to 86,000 (cross-polar)14 N/A12.2434550503835354042475555 5555
    92,000 to 95,000N/A0.650.036404550555555

    (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]