Goto Section: 73.315 | 73.317 | Table of Contents
FCC 73.316
Revised as of October 2, 2015
Goto Year:2014 |
2016
§ 73.316 FM antenna systems.
(a) It shall be standard to employ horizontal polarization; however,
circular or elliptical polarization may be employed if desired. Clockwise or
counterclockwise rotation may be used. The supplemental vertically polarized
effective radiated power required for circular or elliptical polarization
shall in no event exceed the effective radiated power authorized.
(b) Directional antennas. A directional antenna is an antenna that is
designed or altered for the purpose of obtaining a non-circular radiation
pattern.
(1) Applications for the use of directional antennas that propose a ratio of
maximum to minimum radiation in the horizontal plane of more than 15 dB will
not be accepted.
(2) Directional antennas used to protect short-spaced stations pursuant to
§ 73.213 or § 73.215 of the rules, that have a radiation pattern which varies
more than 2 dB per 10 degrees of azimuth will not be authorized.
(c) Applications for directional antennas. (1) Applications for construction
permit proposing the use of directional antenna systems must include a
tabulation of the composite antenna pattern for the proposed directional
antenna. A value of 1.0 must be used to correspond to the direction of
maximum radiation. The pattern must be tabulated such that 0° corresponds to
the direction of maximum radiation or alternatively, in the case of an
asymmetrical antenna pattern, the pattern must be tabulated such that 0°
corresponds to the actual azimuth with respect to true North. In the case of
a composite antenna composed of two or more individual antennas, the pattern
required is that for the composite antenna, not the patterns for each of the
individual antennas. Applications must include valuations tabulated at
intervals of not greater than ten (10) degrees. In addition, tabulated
values of all maximas and minimas, with their corresponding azimuths, must
be submitted.
(2) Applications for license upon completion of antenna construction must
include the following:
(i) A complete description of the antenna system, including the manufacturer
and model number of the directional antenna. It is not sufficient to label
the antenna with only a generic term such as “dipole.” In the case of
individually designed antennas with no model number, or in the case of a
composite antenna composed of two or more individual antennas, the antenna
must be described as a “custom” or “composite” antenna, as appropriate. A
full description of the design of the antenna must also be submitted.
(ii) A plot of the composite pattern of the directional antenna. A value of
1.0 must be used to correspond to the direction of maximum radiation. The
plot of the pattern must be oriented such that 0° corresponds to the
direction of maximum radiation or alternatively, in the case of an
asymmetrical antenna pattern, the plot must be oriented such that 0°
corresponds to the actual azimuth with respect to true North. The horizontal
plane pattern must be plotted to the largest scale possible on unglazed
letter-size polar coordinate paper (main engraving approximately 18 cm × 25
cm (7 inches × 10 inches)) using only scale divisions and subdivisions of 1,
2, 2.5, or 5 times 10-nth. Values of field strength less than 10% of the
maximum field strength plotted on that pattern must be shown on an enlarged
scale. In the case of a composite antenna composed of two or more individual
antennas, the composite antenna pattern should be provided, and not the
pattern for each of the individual antennas.
(iii) A tabulation of the measured relative field pattern required in
paragraph (c)(1) of this section. The tabulation must use the same zero
degree reference as the plotted pattern, and must contain values for at
least every 10 degrees. Sufficient vertical patterns to indicate clearly the
radiation characteristics of the antenna above and below the horizontal
plane. Complete information and patterns must be provided for angles of −10
deg. from the horizontal plane and sufficient additional information must be
included on that portion of the pattern lying between + 10 deg. and the
zenith and −10 deg. and the nadir, to conclusively demonstrate the absence
of undesirable lobes in these areas. The vertical plane pattern must be
plotted on rectangular coordinate paper with reference to the horizontal
plane. In the case of a composite antenna composed of two or more individual
antennas, the composite antenna pattern should be used, and not the pattern
for each of the individual antennas.
(iv) A statement that the antenna is mounted on the top of an antenna tower
recommended by the antenna manufacturer, or is side-mounted on a particular
type of antenna tower in accordance with specific instructions provided by
the antenna manufacturer.
(v) A statement that the directional antenna is not mounted on the top of an
antenna tower which includes a top-mounted platform larger than the nominal
cross-sectional area of the tower in the horizontal plane.
(vi) A statement that no other antenna of any type is mounted on the same
tower level as a directional antenna, and that no antenna of any type is
mounted within any horizontal or vertical distance specified by the antenna
manufacturer as being necessary for proper directional operation.
(vii) A statement from an engineer listing such individual engineer's
qualifications and certifying that the antenna has been installed pursuant
to the manufacturer's instructions.
(viii) A statement from a licensed surveyor that the installed antenna is
properly oriented.
(ix)(A) For a station authorized pursuant to § 73.215 or Sec. § 73.509, a
showing that the root mean square (RMS) of the measured composite antenna
pattern (encompassing both the horizontally and vertically polarized
radiation components (in relative field)) is at least 85 percent of the RMS
of the authorized composite directional antenna pattern (in relative field).
The RMS value, for a composite antenna pattern specified in relative field
values, may be determined from the following formula:
RMS = the square root of:
[(relative field value 1)2 + (relative field value 2)2 + .... + (last
relative field value)2]
total number of relative field values
(B) where the relative field values are taken from at least 36 evenly spaced
radials for the entire 360 degrees of azimuth. The application for license
must also demonstrate that coverage of the community of license by the 70
dBu contour is maintained for stations authorized pursuant to § 73.215 on
Channels 221 through 300, as required by § 73.315(a), while noncommercial
educational stations operating on Channels 201 through 220 must show that
the 60 dBu contour covers at least a portion of the community of license.
(d) Applications proposing the use of FM transmitting antennas in the
immediate vicinity (i.e. 60 meters or less) of other FM or TV broadcast
antennas must include a showing as to the expected effect, if any, of such
approximate operation.
(e) Where an FM licensee or permittee proposes to mount its antenna on or
near an AM tower, as defined in § 1.30002, the FM licensee or permittee must
comply with § 1.30003 or § 1.30002, depending on whether the antenna is
proposed to be mounted on an AM tower (§ 1.30003) or near an AM tower
(§ 1.30002).
[ 28 FR 13623 , Dec. 14, 1963, as amended at 34 FR 14222 , Sept. 10, 1969; 37 FR 25841 , Dec. 5, 1972; 43 FR 53738 , Nov. 17, 1978; 48 FR 29508 , June 27,
1983; 51 FR 17028 , May 8, 1986; 54 FR 9804 , Mar. 8, 1989; 56 FR 57294 , Nov.
8, 1991; 62 FR 51058 , Sept. 30, 1997; 63 FR 70047 , Dec. 18, 1998; 78 FR 66298 , Nov. 5, 2013]
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Goto Section: 73.315 | 73.317
Goto Year: 2014 |
2016
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