Goto Section: 73.189 | 73.201 | Table of Contents
FCC 73.190
Revised as of October 1, 2008
Goto Year:2007 |
2009
Sec. 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, F c(50), for a characteristic field strength of
100 mV/m at 1 km is given by:
[MATH:
:MATH]
The slant distance, D , is given by:
[MATH:
:MATH]
The geomagnetic latitude of the midpoint of the path, ΦM, is given by:
ΦM=arcsin[sin a Msin 78.5 ° + cos a Mcos 78.5 ° cos(69 + b
M)]degrees (Eq. 3)
The short great-circle path distance, d, is given by:
[MATH:
:MATH]
Where:
d ° = arccos[sin a Tsin a R+ cos a Tcos a Rcos( b R− b
[T])]degrees (Eq.5)
Where:
a Tis the geographic latitude of the transmitting terminal (degrees)
a Ris the geographic latitude of the receiving terminal (degrees)
b Tis the geographic longitude of the transmitting terminal (degrees)
b Ris the geographic longitude of the receiving terminal (degrees)
a Mis the geographic latitude of the midpoint of the great-circle path
(degrees) and is given by:
b Mis the geographic longitude of the midpoint of the great-circle path
(degrees) and is given by:
[MATH:
:MATH]
[MATH:
:MATH]
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. , b R> b T),
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, F c(10), is given by:
Fc(10) = Fc(50) + Δ dB( µV/m)
Where:
Δ = 6 when | F[M]| < 40
Δ = 0.2 | F[M]| − 2 when 40 ≤ | FM| ≤ 60
Δ = 10 when | FM| > 60
(d) Figure 6a depicts angles of departure versus transmission range. These
angles may also be computed using the following formulas:
[MATH:
:MATH]
Where:
d=distance in kilometers
n=1 for 50% field strength values
n=2 or 3 for 10% field strength values
and where
K[1]=0.00752
K[2]=0.00938
K[3]=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.
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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]
Subpart B—FM Broadcast Stations
Goto Section: 73.189 | 73.201
Goto Year: 2007 |
2009
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