Section 73.625 - TV antenna system(c)Antenna system.(1) The antenna system shall be designed so that the effective radiated power at any angle above the horizontal shall be as low as the state of the art permits, and in the same vertical plane may not exceed the effective radiated power in either the horizontal direction or below the horizontal, whichever is greater.(2) An antenna designed or altered to produce a noncircular radiation pattern in the horizontal plane is considered to be a directional antenna. Antennas purposely installed in such a manner as to result in the mechanical beam tilting of the major vertical radiation lobe are included in this category.(3) Applications proposing the use of directional antenna systems must be accompanied by the following:(i) Complete description of the proposed antenna system, including the manufacturer and model number of the proposed directional antenna.(ii) Relative field azimuth plane pattern (patterns for both horizontal and vertical polarization should be included if elliptical or circular polarization is used consistent with paragraph (d) of this section) of the proposed directional antenna. A value of 1.0 should be used for the maximum radiation in the horizontal polarization. The plot of the pattern should be oriented so that 0 degrees corresponds to true North. Where mechanical beam tilt is intended, the amount of tilt in degrees of the antenna vertical axis and the orientation of the downward tilt with respect to true North must be specified, and a tabulation of the elevation pattern included consistent with paragraph (c)(3)(vii) of this section. A horizontal plane pattern reflecting the use of mechanical beam tilt may be requested if required to facilitate international coordination.(iii) A tabulation of the relative field pattern required in paragraph (c)(3)(ii) of this section. The tabulation should use the same zero degree reference as the plotted pattern, and be tabulated at least every 10 degrees. In addition, tabulated values of all maxima and minima, with their corresponding azimuths, should be submitted.(iv) Horizontal and vertical plane radiation patterns showing the effective radiated power, in dBk, for each direction. Sufficient vertical plane patterns must be included to indicate clearly the radiation characteristics of the antenna above and below the horizontal plane. In cases where the angles at which the maximum vertical radiation varies with azimuth, a separate vertical radiation pattern must be provided for each pertinent radial direction.(v) All azimuth plane patterns must be plotted in a PDF attachment to the application in a size sufficient to be easily viewed.(vi) The horizontal and vertical plane patterns that are required are the patterns for the complete directional antenna system. In the case of a composite antenna composed of two or more individual antennas, this means that the patterns for the composite antenna, not the patterns for each of the individual antennas, must be submitted.(vii) If an elevation pattern is submitted in the application form, similar tabulations and PDF attachments shall be provided for the elevation pattern.(viii) If a matrix pattern is submitted in the application form, similar tabulations shall be provided as necessary in the form of a spreadsheet to accurately represent the pattern.(4) Where simultaneous use of antennas or antenna structures is proposed, the following provisions shall apply: (i) In cases where it is proposed to use a tower of an AM broadcast station as a supporting structure for a TV broadcast antenna, an appropriate application for changes in the radiating system of the AM broadcast station must be filed by the licensee thereof. A formal application (FCC Form 301, or FCC Form 340 for a noncommercial educational station) will be required if the proposal involves substantial change in the physical height or radiation characteristics of the AM broadcast antennas; otherwise an informal application will be acceptable. (In case of doubt, an informal application (letter) together with complete engineering data should be submitted.) An application may be required for other classes of stations when the tower is to be used in connection with a TV station.(ii) When the proposed TV antenna is to be mounted on a tower in the vicinity of an AM station directional antenna system and it appears that the operation of the directional antenna system may be affected, an engineering study must be filed with the TV application concerning the effect of the TV antenna on the AM directional radiation pattern. Field measurements of the AM stations may be required prior to and following construction of the TV station antenna, and readjustments made as necessary.(iii) In any case, where the TV licensee or permittee proposes to mount its antenna on or near an AM tower, as defined in § 1.30002 , the TV licensee or permittee must comply with § 1.30002 or § 1.30003 , as applicable.(5) Applications proposing the use of electrical beam tilt must be accompanied by the following: (i) Complete description of the proposed antenna system, including the manufacturer and model number. Vertical plane radiation patterns conforming with paragraphs (c)(3)(iv), (c)(3)(v) and (c)(3)(vi) of this section.(ii) For at least 36 evenly spaced radials, including 0 degrees corresponding to true North, a determination of the depression angle between the transmitting antenna center of radiation and the radio horizon using the formula in paragraph (b)(2) of this section.(iii) For each such radial direction, the ERP at the depression angle, taking into account the effect of the electrical beam tilt, mechanical beam tilt, if used, and directional antenna pattern if a directional antenna is specified.(iv) The maximum ERP toward the radio horizon determined by this process must be clearly indicated. In addition, a tabulation of the relative fields representing the effective radiation pattern toward the radio horizon in the 36 radial directions must be submitted. A value of 1.0 should be used for the maximum radiation.(d) It shall be standard to employ horizontal polarization. However, circular or elliptical polarization may be employed if desired, in which case clockwise (right hand) rotation, as defined in the IEEE Standard Definition 42A65-3E2, and transmission of the horizontal and vertical components in time and space quadrature shall be used. For either omnidirectional or directional antennas the licensed effective radiated power of the vertically polarized component may not exceed the licensed effective radiated power of the horizontally polarized component. For directional antennas, the maximum effective radiated power of the vertically polarized component shall not exceed the maximum effective radiated power of the horizontally polarized component in any specified horizontal or vertical direction.62 FR 26990, May 16, 1997, as amended at 63 FR 13562, Mar. 20, 1998; 66 FR 9985, Feb. 13, 2001; 66 FR 65135, Dec. 18, 2001; 83 FR 5544, Feb. 8, 2018; 86 FR 66209, Nov. 22, 2021 83 FR 5544, 2/8/2018; 86 FR 66193, 12/22/2021; 89 FR 7250, 3/4/2024