Goto Section: 73.151 | 73.153 | Table of Contents
FCC 73.152
Revised as of October 1, 2011
Goto Year:2010 |
2012
§ 73.152 Modification of directional antenna data.
(a) If, after construction and final adjustment of a directional
antenna, a measured inverse distance field in any direction exceeds the
field shown on the standard radiation pattern for the pertinent mode of
directional operation, an application shall be filed, specifying a
modified standard radiation pattern and/or such changes as may be
required in operating parameters so that all measured effective fields
will be contained within the modified standard radiation pattern.
Permittees may also file an application specifying a modified standard
radiation pattern, even when measured radiation has not exceeded the
standard pattern, in order to allow additional tolerance for monitoring
point limits.
(b) If, following a partial proof of performance, a licensee discovers
that radiation exceeds the standard pattern on one or more radials
because of circumstances beyond the licensee's control, a modified
standard pattern may be requested. The licensee shall submit,
concurrently, Forms 301-AM and 302-AM. Form 301-AM shall include an
exhibit demonstrating that no interference would result from the
augmentation. Form 302-AM shall include the results of the partial
proof, along with full directional and nondirectional measurements on
the radial(s) to be augmented, including close-in points and a
determination of the inverse distance field in accordance with
§ 73.186.
(c) Normally, a modified standard pattern is not acceptable at the
initial construction permit stage, before a proof-of-performance has
been completed. However, in certain cases, where it can be shown that
modification is necessary, a modified standard pattern will be
acceptable at the initial construction permit stage. Following is a
non-inclusive list of items to be considered in determining whether a
modification is acceptable at the initial construction permit stage:
(1) When the proposed pattern is essentially the same as an existing
pattern at the same antenna site. (e.g., A DA-D station proposing to
become a DA-1 station.)
(2) Excessive reradiating structures, which should be shown on a plat
of the antenna site and surrounding area.
(3) Other environmental factors; they should be fully described.
(4) Judgment and experience of the engineer preparing the engineering
portion of the application. This must be supported with a full
discussion of the pertinent factors.
(d) The following general principles shall govern the situations in
paragraphs (a), (b), and (c) in this section:
(1) Where a measured field in any direction will exceed the authorized
standard pattern, the license application may specify the level at
which the input power to the antenna shall be limited to maintain the
measured field at a value not in excess of that shown on the standard
pattern, and shall specify the common point current corresponding to
this power level. This value of common point current will be specified
on the license for that station.
(2) Where any excessive field does not result in objectionable
interference to another station, a modification of construction permit
application may be submitted with a modified standard pattern
encompassing all augmented fields. The modified standard pattern shall
supersede the previously submitted standard radiation pattern for that
station in the pertinent mode of directional operation. Following are
the possible methods of creating a modified standard pattern:
(i) The modified pattern may be computed by making the entire pattern
larger than the original pattern ( i.e. , have a higher RMS value) if
the measured fields systematically exceed the confines of the original
pattern. The larger pattern shall be computed by using a larger
multiplying constant, k, in the theoretical pattern equation (Eq. 1) in
§ 73.150(b)(1).
(ii) Where the measured field exceeds the pattern in discrete
directions, but objectionable interference does not result, the pattern
may be expanded over sectors including these directions. When this
"augmentation" is desired, it shall be achieved by application of the
following equation:
E(f,TH)aug= SQRT { E(f,TH)std}^2 +A{ g (TH) cos (180 D A /S }^2
where:
E(f,TH)stdis the standard pattern field at some particular azimuth and
elevation angle, before augmentation, computed pursuant to Eq. 2,
§ 73.150(b)(1)(i).
E(f,TH)aug. is the field in the direction specified above, after
augmentation.
A=E(f,O)^2 aug -E(f,O)^2 stdin whichfis the central azimuth of
augmentation. E(f,O)augand E(f,O)stdare the fields in the horizontal
plane at the central azimuth of augmentation.
Note: "A" must be positive, except during the process of converting
non-standard patterns to standard patterns pursuant to the Report and
Order in Docket No. 21473, and in making minor changes to stations with
patterns developed during the conversion. However, even when "A" is
negative, "A" cannot be so negative that E(f,a)augis less than
E(f,TH)that any azimuth or vertical elevation angle.
g(TH) is defined in § 73.150(b)(1)(i).
S is the angular range, or "span", over which augmentation is applied.
The span is centered on the central azimuth of augmentation. At the
limits of the span, the augmented pattern merges into the unaugmented
pattern. Spans may overlap.
D[A]is the absolute horizontal angle between the azimuth at which the
augmented pattern value is being computed and the central azimuth of
augmentation. (D[A]cannot exceed 1/2 S.)
In the case where there are spans which overlap, the above formula
shall be applied repeatedly, once for each augmentation, in ascending
order of central azimuth of augmentation, beginning with zero degrees
representing true North. Note that, when spans overlap, there will be,
in effect, an augmentation of an augmentation. And, if the span of an
earlier augmentation overlaps the central azimuth of a later
augmentation, the value of "A" for the later augmentation will be
different than the value of "A" without the overlap of the earlier
span.
(iii) A combination of paragraphs (d)(2)(i) and (d)(2)(ii), of this
section, with (d)(2)(i) being applied before (d)(2)(ii) is applied.
(iv) Where augmentation is allowable under the terms of this section,
the requested amount of augmentation shall be centered upon the
measured radial and shall not exceed the following:
(A) The actual measured inverse distance field value, where the radial
does not involve a required monitoring point.
(B) 120% of the actual measured inverse field value, where the radial
has a monitoring point required by the instrument of authorization.
Whereas some pattern smoothing can be accommodated, the extent of the
requested span(s) shall be minimized and in no case shall a requested
augmentation span extend to a radial azimuth for which the analyzed
measurement data does not show a need for augmentation.
(3) A Modified Standard Pattern shall be specifically labeled as such,
and shall be plotted in accordance with the requirements of paragraph
(b)(2) of § 73.150. The effective (RMS) field strength in the
horizontal plane of E(f,a)std,E(f,a)th,and the root sum square (RSS)
value of the inverse fields of the array elements (derived from the
equation for E(f,a)th), shall be tabulated on the page on which the
horizontal plane pattern is plotted. Where sector augmentation has been
employed in designing the modified pattern, the direction of maximum
augmentation ( i.e. , the central azimuth of augmentation) shall be
indicated on the horizontal plane pattern for each augmented sector,
and the limits of each sector shall also be shown. Field values within
an augmented sector, computed prior to augmentation, shall be depicted
by a broken line.
(4) There shall be submitted, for each modified standard pattern,
complete tabulations of final computed data used in plotting the
pattern. In addition, for each augmented sector, the central azimuth of
augmentation, span, and radiation at the central azimuth of
augmentation (E(f,a)aug) shall be tabulated.
(5) The parameters used in computing the modified standard pattern
shall be specified with realistic precision. Following is a list of the
maximum acceptable precision:
(i) Central Azimuth of Augmentation: to the nearest 0.1 degree.
(ii) Span: to the nearest 0.1 degree.
(iii) Radiation at Central Azimuth of Augmentation: 4 significant
figures.
(e) Sample calculations for a modified standard pattern follow. First,
assume the existing standard pattern in § 73.150(c). Then, assume the
following augmentation parameters:
Augmentation number Central azimuth Span Radiation at central azimuth
1 110 40 1,300
2 240 50 52
3 250 10 130
Following is a tabulation of part of the modified standard pattern:
Azimuth 0 30 60 Vertical angle
0 28.86 68.05 72.06
105 1,299.42 872.14 254.21
235 39.00 35.74 38.71
247 100.47 66.69 32.78
[ 46 FR 11992 , Feb. 12, 1981, as amended at 56 FR 64862 , Dec. 12, 1991;
66 FR 20756 , Apr. 25, 2001]
Goto Section: 73.151 | 73.153
Goto Year: 2010 |
2012
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