Section 73.160 - Vertical plane radiation characteristics, f(&b.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 [THETA], 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([THETA]). The generic formula for f([THETA]) is: f([THETA])=E([THETA])/E(O)
where:
E([THETA]) is the radiation from the tower at angle [THETA].
E(O) is the radiation from the tower in the horizontal plane.
(b) Listed below are formulas for f([THETA]) for several common towers. (1) For a typical tower, which is not top-loaded or sectionalized, the following formula shall be used: View Image
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: View Image
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.
View Image
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(3) For a sectionalized tower, the following formula shall be used: View Image
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.
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(c) One of the above f([THETA]) 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([THETA]) 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: | [THETA] | f([THETA]) |
| 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): | [THETA] | f([THETA]) |
| 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): | [THETA] | f([THETA]) |
| 0 | 1.0000 |
| 30 | 0.5930 |
| 60 | 0.1423 |