Sec. 74.937  Antennas.

    (a) In order to minimize the hazard of harmful interference from 
other stations, directive receiving antennas should be used at all 
receiving locations. The choice of receiving antennas is left to the 
discretion of the licensee. However, for the purpose of interference 
calculations, 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 at the receive site. Licensees may install 
receiving antennas with general characteristics superior to those of the 
reference receive antenna. Nevertheless, should interference occur and 
it can be demonstrated by an applicant that the existing antenna at the 
receive site is inappropriate, a more suitable yet practical receiving 
antenna should be installed. In such cases, the modification of the 
receive site will be in the discretion, and will be the responsibility, 
of the licensee serving the site.

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    (b) 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.
    (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]