47 C.F.R. § 73.160

Current through October 31, 2024
Section 73.160 - Vertical plane radiation characteristics, f([THETA])
(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

(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.

View Image

(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])
01.0000
300.7698
600.3458

(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])
01.0000
300.7364
600.2960

(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])
01.0000
300.5930
600.1423

47 C.F.R. §73.160

46 FR 11993, Feb. 12, 1981