Goto Section: 73.189 | 73.201 | Table of Contents
FCC 73.190
Revised as of October 1, 2014
Goto Year:2013 |
2015
§ 73.190 Engineering charts and related formulas.
(a) This section consists of the following Figures: 2, r3, 5, 6a, 7, 8,
9, 10, 11, 12, and 13. Additionally, formulas that are directly related
to graphs are included.
(b) Formula 1 is used for calculation of 50% skywave field strength
values.
Formula 1. Skywave field strength, 50% of the time (at SS+6):
The skywave field strength, Fc(50), for a characteristic field strength
of 100 mV/m at 1 km is given by:
eCFR graphic ec01mr91.068.gif
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The slant distance, D, is given by:
eCFR graphic ec13no91.020.gif
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The geomagnetic latitude of the midpoint of the path, FM, is given by:
FM =arcsin[sin aM sin 78.5DEG + cos aM cos 78.5DEG cos(69 +
bM)]degrees (Eq. 3)
The short great-circle path distance, d, is given by:
eCFR graphic ec13no91.021.gif
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Where:
dDEG = arccos[sin aT sin aR + cos aT cos aR cos(bR -
bT)]degrees (Eq.5)
Where:
aT is the geographic latitude of the transmitting terminal (degrees)
aR is the geographic latitude of the receiving terminal (degrees)
bT is the geographic longitude of the transmitting terminal (degrees)
bR is the geographic longitude of the receiving terminal (degrees)
aM is the geographic latitude of the midpoint of the great-circle path
(degrees) and is given by:
bM is the geographic longitude of the midpoint of the great-circle path
(degrees) and is given by:
eCFR graphic ec01mr91.069.gif
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eCFR graphic ec01mr91.070.gif
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Note (1): If |FM| is greater than 60 degrees, equation (1) is evaluated
for | FM| = 60 degrees.
Note (2): North and east are considered positive; south and west
negative.
Note (3): In equation (7), k = -1 for west to east paths (i.e., bR
>bT), otherwise k = 1.
(c) Formula 2 is used for calculation of 10% skywave field strength
values.
Formula 2. Skywave field strength, 10% of the time (at SS+6):
The skywave field strength, Fc(10), is given by:
Fc(10) = Fc(50) + D dB(uV/m)
Where:
D = 6 when | FM| <40
D = 0.2 | FM| - 2 when 40 <=| FM| <=60
D = 10 when | FM| >60
(d) Figure 6a depicts angles of departure versus transmission range.
These angles may also be computed using the following formulas:
eCFR graphic ec01mr91.071.gif
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Where:
d=distance in kilometers
n=1 for 50% field strength values
n=2 or 3 for 10% field strength values
and where
K1=0.00752
K2=0.00938
K3=0.00565
Note: Computations using these formulas should not be carried beyond
0.1 degree.
(e) In the event of disagreement between computed values using the
formulas shown above and values obtained directly from the figures, the
computed values will control.
eCFR graphic ec01mr91.072.gif
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eCFR graphic ec01mr91.073.gif
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eCFR graphic ec01mr91.074.gif
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eCFR graphic ec01mr91.075.gif
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eCFR graphic ec01mr91.076.gif
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eCFR graphic ec01mr91.077.gif
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eCFR graphic ec01mr91.078.gif
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eCFR graphic ec01mr91.079.gif
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eCFR graphic ec01mr91.080.gif
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eCFR graphic ec01mr91.082.gif
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eCFR graphic ec01mr91.083.gif
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eCFR graphic ec01mr91.084.gif
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[ 28 FR 13574 , Dec. 14, 1963, as amended at 30 FR 12720 , Oct. 6, 1965;
33 FR 15420 , Oct. 17, 1968; 48 FR 42959 , Sept. 20, 1983; 49 FR 43963 ,
Nov. 1, 1984; 50 FR 18844 , May 2, 1985; 51 FR 4753 , Feb. 7, 1986; 52 FR 36879 , Oct. 1, 1987; 56 FR 64869 , Dec. 12, 1991]
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Subpart B--FM Broadcast Stations
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Goto Section: 73.189 | 73.201
Goto Year: 2013 |
2015
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