[Code of Federal Regulations] [Title 47, Volume 4] [Revised as of October 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 47CFR73.160] [Page 42-46] TITLE 47--TELECOMMUNICATION COMMISSION (CONTINUED) PART 73_RADIO BROADCAST SERVICES--Table of Contents Subpart A_AM Broadcast Stations Sec. 73.160 Vertical plane radiation characteristics, f([thetas]). (a) The vertical plane radiation characteristics show the relative field being radiated at a given vertical angle, with respect to the horizontal plane. The vertical angle, represented as [thetas], is 0 degrees in the horizontal plane, and 90 degrees when perpendicular to the horizontal plane. The vertical plane radiation characteristic is referred to as f([thetas]). The generic formula for f([thetas]) is: f([thetas])=E([thetas])/E(O) where: E([thetas]) is the radiation from the tower at angle [thetas]. E(O) is the radiation from the tower in the horizontal plane. (b) Listed below are formulas for f([thetas]) for several common towers. (1) For a typical tower, which is not top-loaded or sectionalized, the following formula shall be used: [GRAPHIC] [TIFF OMITTED] TC13NO91.015 where: G is the electrical height of the tower, not including the base insulator and pier. (In the case of a folded unipole tower, the entire radiating structure's electrical height is used.) (2) For a top-loaded tower, the following formula shall be used: [GRAPHIC] [TIFF OMITTED] TC13NO91.016 where: A is the physical height of the tower, in electrical degrees, and B is the difference, in electrical degrees, between the apparent electrical height (G, based on current distribution) and the actual physical height. G is the apparent electrical height: the sum of A and B; A+B. See Figure 1 of this section. [[Page 43]] [GRAPHIC] [TIFF OMITTED] TC01MR91.066 (3) For a sectionalized tower, the following formula shall be used: [[Page 44]] [GRAPHIC] [TIFF OMITTED] TC13NO91.017 where: A is the physical height, in electrical degrees, of the lower section of the tower. B is the difference between the apparent electrical height (based on current distribution) of the lower section of the tower and the physical height of the lower section of the tower. C is the physical height of the entire tower, in electrical degrees. D is the difference between the apparent electrical height of the tower (based on current distribution of the upper section) and the physical height of the entire tower. D will be zero if the sectionalized tower is not top-loaded. G is the sum of A and B; A+B. H is the sum of C and D; C+D. [Delta] is the difference between H and A; H-A. See Figure 2 of this section. [[Page 45]] [GRAPHIC] [TIFF OMITTED] TC01MR91.067 (c) One of the above f([thetas]) formulas must be used in computing radiation in the vertical plane, unless the applicant submits a special formula for a particular type of antenna. If a special formula is submitted, it must be accompanied by a complete derivation and [[Page 46]] sample calculations. Submission of values for f([thetas]) only in a tabular or graphical format (i.e., without a formula) is not acceptable. (d) Following are sample calculations. (The number of significant figures shown here should not be interpreted as a limitation on the number of significant figures used in actual calculations.) (1) For a typical tower, as described in paragraph (b)(1) of this section, assume that G=120 electrical degrees: ------------------------------------------------------------------------ [thetas] f([thetas]) ------------------------------------------------------------------------ 0.......................................................... 1.0000 30......................................................... 0.7698 60......................................................... 0.3458 ------------------------------------------------------------------------ (2) For a top-loaded tower, as described in paragraph (b)(2) of this section, assume A=120 electrical degrees, B=20 electrical degrees, and G=140 electrical degrees, (120+20): ------------------------------------------------------------------------ [thetas] f([thetas]) ------------------------------------------------------------------------ 0.......................................................... 1.0000 30......................................................... 0.7364 60......................................................... 0.2960 ------------------------------------------------------------------------ (3) For a sectionalized tower, as described in paragraph (b)(3) of this section, assume A=120 electrical degrees, B=20 electrical degrees, C=220 electrical degrees, D=15 electrical degrees, G=140 electrical degrees (120+20), H=235 electrical degrees (220+15), and [Delta]=115 electrical degrees (235-120): ------------------------------------------------------------------------ [thetas] f([thetas]) ------------------------------------------------------------------------ 0.......................................................... 1.0000 30......................................................... 0.5930 60......................................................... 0.1423 ------------------------------------------------------------------------ [46 FR 11993, Feb. 12, 1981]