47 CFR §73.160

1. (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 θ, 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(θ). The generic formula for f(θ) is:
2. (b)Listed below are formulas for f(θ) for several common towers.
   1. (1)For a typical tower, which is not top-loaded or sectionalized, the following formula shall be used:
   2. (2)For a top-loaded tower, the following formula shall be used:
   3. (3)For a sectionalized tower, the following formula shall be used:
3. (c)One of the above f(θ) 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 sample calculations. Submission of values for f(θ) only in a tabular or graphical format (i.e., without a formula) is not acceptable.
4. (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. (1)For a typical tower, as described in paragraph (b)(1) of this section, assume that G = 120 electrical degrees:
   2. (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):
   3. (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 Δ = 115 electrical degrees (235−120):