Research Concepts RC2000A - Manual (Page 111)

RC2000A Dual Axis Antenna Controller Appendix I 2.6x Addendum 111
Mag Heading: 117.3
Here are the calculations for the antenna azimuth and elevation count per degree characteristics for the
data in the table above.
Azimuth Counts per Degree =
[2110 – 1455] / [149.5 – 136.0] = 375 / 13.3 = 48.5 counts per degree
Elevation Counts per Degree =
[2167 – 1639] / [30.7 – 25.4] = 355 / 5.3 = 99.6 counts per degree
Here are some count per degree characteristics that have been tabulated for
3.5.4 Azimuth Step Size Correction Factor (for Elevation over Azimuth Antenna
Mounts)
The azimuth step size calculation requires a Correction Factor that relates antenna movement about the
azimuth axis to the change in antenna pointing angle. The azimuth step size should correspond to a
change in the antenna pointing angle that will reduce the received signal strength by 0.5 or 1.0 dB. In
section 3.5.1, pointing angle change required to produce a 0.5 and 1.0 dB drop in signal strength is
calculated. The Correction Factor is required because when the antenna is not at zero degrees
elevation (pointing at the horizon) a one degree change in azimuth angle changes the antenna pointing
angle by an amount less than one degree.
The Correction Factor is the number of degrees of azimuth movement required to produce one degree
of antenna pointing angle change. The Correction Factor is a function of elevation angle. The
Correction Factor is larger for higher elevation angles.
Correction Factor vs. Elevation Angle
Antenna
Elevation
Angle 10 deg 20 deg 30 deg 40 deg 50 deg 60 deg 70 deg 80 deg
Correction
Factor 1.02 1.05 1.15 1.31 1.46 2.00 2.92 5.78
An antenna with an elevation over azimuth mount works over a range of elevation values. The exact
range is a function of earth station latitude and the difference in longitude between the earth station and
the satellite.
The following table lists elevation look angles vs. antenna latitude for i) satellites located at the same
longitude as the antenna, and ii) satellites whose longitude is 50 degrees away from that of the antenna.
The table also includes a recommended value for the Correction Factor used for antennas located at
that antenna latitude.
Antenna Latitude 25
° 30° 35° 40° 45° 50°
Elevation Angle for satellite
whose longitude value is the
same antenna. 60.8
° 55.0° 49.4° 43.7° 38.2° 32.7°
Elevation Angle for satellites
separated from the antenna by
50 degrees longitude. 28.0
° 26.0° 23.8° 21.4° 18.8° 16.1°
Recommended Correction
Factor 1.75 1.50 1.40 1.30 1.25 1.10
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