APPENDIX ‘A’
This section contains the formulas for determining the point- ing capabilities of the modular mount earth station antenna.
Formulas for calculating true azimuth (AZ), true elevation (EL), relative angle between true azimuth and mount point- ing angle (dAZ) and strut lengths of the earth station are given below:
Given the earth station latitude, longitude, azimuth set- ting of mount (AZm) and satellite longitude (over the equa- tor), the following calculations can be made:
For earth stations north of the equator:
AZ = 180° + arc tan (tan θ/sin α )
For earth stations south of the equator:
AZ = 360° - arc tan (tan θ/sin α )
Where:
AZ = true azimuth to view satellite, in degrees East (clock- wise) of True North.
α= earth station latitude in degrees.
θ= satellite longitude minus earth station longitude, in degrees.
NOTE: Earth station latitude values are positive for sites located north of the equator and negative for sites south of the equator. Longitude values are positive for earth station sites or satellite positions west of Greenwich and negative east of Greenwich.
dAZ = relative angle between true azimuth angle looking at satellite and mount pointing direction in degrees.
EL = 90° - T - R
Where:
EL = true elevation angle to view satellite in degrees.
R = arc cos (cos θ cos α)
T = arc tan [sin R/(6.6166 - cos R)]
Pin to pin length of elevation strut in inches:
Equation (1):XEL = √26259.7740 - 14970.1377 [cos(27.0362° + EL)]
For the -90° to +30° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (2): LAZ = √7571.2865 - 6181.928 [cos(105° + dAZ)]
For the -60° to +60° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (3): LAZ = √7571.2865 - 6181.928 [cos(75° - dAZ)]
For the -30° to +90° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (4): LAZ = √7571.2865 - 6181.928 [cos(105° - dAZ)]
dAZ = AZ - AZm
Where:
AZm = azimuth at which mount is set in degrees East (clockwise) of True North.
NOTE: Azimuth strut
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