§ 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 § 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 § 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.

EC01MR91.112

(b) Except as set forth in § 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.