Research Concepts RC2000A User Manual

Page 110

110

RC2000A Dual Axis Antenna Controller

Appendix I

2.6x Addendum

3.5.3 Determining The Antenna Azimuth and Elevation Count per Degree
Characteristic

To calculate the optimal step sizes for a given antenna it is necessary to know the antenna mount’s
azimuth and elevation count per degree characteristic. Note that for an antenna powered by a linear
actuator the antenna’s azimuth and elevation count per degree characteristic is not a single value, it is
described by the law of cosines, and varies depending on actuator extension/retraction. For
determining peakup step sizes, assuming that the antenna azimuth and elevation count per degree
characteristics are constant does not introduce a large error.

The easiest way to determine the count per degree characteristic of a given antenna is to derive it from
antenna pointing data using a satellite antenna pointing calculator. An antenna pointing calculator,
ANTENNA.EXE, is included on the diskette in the back of the antenna controller manual.
ANTENNA.EXE can also be downloaded from the Research Concepts web site,

www.researchconcepts.com

An example will demonstrate the technique. This example is based on an EASi 4.5 meter antenna
employing a ViaSat reflector and a Baird mount powered by 90 volt DC motors. The antenna is located
in Seattle, latitude 47

° 40’, longitude 122° 30’. In the following table, each row represents a unique

satellite.

Satellite Location
(longitude)

Azimuth
Position
Count

Elevation
Position
Count

Antenna True
Heading
(degrees
from true
north)

Antenna
Elevation
Heading
(degrees)

° West

1455

1639

136.0

25.4

West

2110 2167 149.5 30.7

The columns labeled ‘azimuth position count’ and ‘elevation position count’ represent the position of the
satellite in the controller’s non-volatile memory. The data in the columns labeled ‘Antenna True
Heading’ and ‘Antenna Elevation Heading’ is obtained from the ANTENNA.EXE program.

Here is a screen shot of the ANTENNA.EXE program for the satellite located at 87

° West. Note that for

geostationary satellites, the Inclination field in ANTENNA.EXE should be set to 0.0.

Antenna Location

Latitude: 47.40

Longitude: -122.30

Mag Variation: -18.73

Satellite Data

Longitude: -87.00

Inclination: 0.00

Pointing Solution (in degrees)

Elevation: 25.4

True Heading: 136.0

Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com