Sec.  74.937   Antennas.

   

   (a) In order to minimize the hazard of harmful cochannel and adjacent
   channel interference from other stations, directive receiving antennas
   should be used at all receiving locations other than response station
   hubs and response stations operating with an EIRP no greater than -6
   dBW per 6 MHz channel. The choice of receiving antennas is left to the
   discretion of the licensee. However, for the purpose of interference
   calculations, except as set forth in Sec. 74.939, the general
   characteristics of the reference receiving antenna shown in Figure 1
   of this section (i.e., a 0.6 meter (2 foot) parabolic reflector
   antenna, are assumed to be used in accordance with the provisions of
   Sec. 74.903(a)(3) unless pertinent data is submitted of the actual antenna
   in use for reception. Licensees may install receiving antennas with
   general characteristics superior to those of the reference antenna.
   Should interference occur and it can be demonstrated that the existing
   receiving antenna is inadequate, a more suitable antenna should be
   installed. In such cases, installation of the new receiving antenna
   will be the responsibility of the system operator serving the receive
   site. A response station operating with an EIRP no greater than -6 dBW
   per 6 MHz channel may use an omnidirectional receiving antenna.
   However, for the purpose of interference protection, such response
   stations will be treated as if utilizing a receive antenna meeting the
   requirements of the reference receiving antenna shown in Figure 1 of
   this section.
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   (b) Except as set forth in Sec. 74.931(c)(4) and (d)(3), directive
   transmitting antennas shall be used whenever feasible so as to
   minimize interference to other licensees. The radiation pattern shall
   be designed to minimize radiation in directions where no reception is
   intended. When an ITFS station is used for point-to-point service, an
   appropriate directional antenna must be used. Notwithstanding these
   provisions, response stations operating with an EIRP no greater than
   -6 dBW per 6 MHz channel may utilize omnidirectional transmitting
   antennas.

   (c) The use of elevated receiving antennas is preferable to the use of
   elevated transmitting antennas or greater power to provide the desired
   service.

   (d) The use of vertical or horizontal plane polarization or right-hand
   or left-hand rotating (circular) polarization may be used to minimize
   the hazard of harmful interference between systems. The Commission
   reserves the right to specify the polarization to be used.

   (e) The power gain compared to an isotropic antenna and the directive
   properties of the transmitting and receiving antennas proposed to be
   employed, as well as the geometric distribution of the transmitting
   and receiving points, shall be supplied with each application for a
   new ITFS fixed station or for changes in the antenna facilities of an
   existing station.

   [ 28 FR 13731 , Dec. 14, 1963, as amended at  48 FR 9012 , Mar. 3, 1983;
    49 FR 32596 , Aug. 15, 1984;  50 FR 26761 , June 28, 1985;  52 FR 3806 ,
   Feb. 6, 1987;  58 FR 44951 , Aug. 25, 1993;  63 FR 65118 , Nov. 25, 1998;
    65 FR 46622 , July 31, 2000]