RESEARCH CONCEPTS RC2000C Manual page 41

RC2000C Polar Tracking Antenna Controller
The elevation region over which the measurements are made should correspond to the range of elevation
angles which will be encountered in operation (i.e. the elevation values over which the satellites will be
found).
4. Use the following formula to calculate the Elev Constant:
( (CNT_2 - CNT_1) / (DEG_2 - DEG_1) ) * 57.29
CNT2 - CNT1 = _______ / DEG2 - DEG1 = _______ * 57.29 = ________
If the result is negative, change the sign to positive.
Here is an example:
Place the inclinometer on one of the back support struts of the antenna. The antenna is located near
Kansas City, Kansas, USA (latitude 39 N, longitude 94 W). A satellite located longitude 94 W has an
elevation look angle of 44 degrees relative to the horizon. The normal range of elevation movement is 20
to 45 degrees.
Positioning the antenna at an elevation angle of 21 degrees, the count is 435. Record CNT_1 as 435 and
DEG_1 as 21 degrees. Move the antenna up in elevation to an angle of 43 degrees where the count is
1272. Record CNT_2 as 1272 and DEG_2 as 43. Perform the calculation:
( (1272 - 435) / (43 - 21) ) * 57.29
simplify to obtain...
Round this up to 2180 and enter this value at the Elev Constant CONFIG mode prompt.
Elev Scale Factor from Manufacturer's Specifications
If the antenna manufacturer gives an elevation position pulses per degree specification for the antenna,
simply multiply the value by 2 to obtain 'elevation position counts per degree' (because the RC2000
counts both the rising and falling edges of the position pulses). Multiply this 'position counts per degree'
value by 57.29 to obtain 'position counts per radian'. Round to the nearest whole number value to obtain
the Elev Constant CONFIG mode item.
Elev position pulses per degree _______ * 2 * 57.29 = _______ (position counts per radian)
Azimuth Scale Factor
The user has the option of providing the controller with a value for the azimuth scale factor via the Azim
Constant CONFIG mode item. If the user does not provide a value for the Azim Constant item, the
controller will determine one based on the locations of geostationary satellites (with sufficient separation)
in the vicinity of an inclined orbit satellite which the user wishes to track.
Normally, the user should let the controller determine the scale factor. The user must specify an azimuth
scale factor if it is impossible to program a pair of geostationary satellites into the controller's memory.
The Azim Constant CONFIG mode item should be set to 0 to specify to the controller that it should
calculate the scale factor. If the Azim Constant is set to a non-zero value, that value is used as the
azimuth scale factor.
If is necessary for the user to specify the azimuth scale factor, there are a couple of methods available to
determine the proper value. The most straightforward method is to obtain the azimuth axis 'degrees per
position pulse' value from the antenna manufacturer. Please refer to the discussion above on
determining the elevation scale factor based on antenna manufacturer's specifications. The procedure
for obtaining the azimuth scale factor from the manufacturer's data is identical to the procedure outlined
for the elevation axis.
An instance of when it is not possible to program a pair of geostationary satellites (and the appropriate
information may not be available from the manufacturer) may occur for a weather satellite where there
are not 2 geostationary satellites available at the weather satellite frequency. It is still possible to
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(837 / 22) * 57.29 = 2179.62.
Chapter 4 Inclined Orbit Satellites
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