Setting Limits; Slow Speed Adjustment - RESEARCH CONCEPTS RC2000C Manual

18 RC2000C Polar Tracking Antenna Controller
The graphs of figure 3.5 show this effect. Each graph plots satellite orbital inclination versus the
maximum elevation angular movement (about the nominal position) required to track a satellite at that
inclination with a polar mount with motorized latitude angle adjustment. An example will illustrate the use
of the graphs.
Example: The satellite antenna is located in New York City (latitude 40 N, longitude 75 W). The satellite
of interest is located at 40 degrees West longitude and has an inclination of 5.5 degrees. How many
degrees of movement is required for the motorized latitude angle adjustment about the nominal position?
i. Identify the proper graph in the figure to use. For this example, choose the
latitude = 45 degree graph. This is closest to the actual latitude value for New
York City (40 degrees North).
ii. Determine the longitude difference between the antenna and the satellite.
For this example the longitude difference is 35 degrees (75 - 40 equals 35).
iii. For the graph selected in step (i), choose the curve on the graph based on
the longitude difference calculated in step (ii). See the legend at the bottom of
figure 3.6. Each curve on a given graph corresponds to a difference in longitude
between the antenna and the satellite. For this example, choose the curve which
corresponds to a longitude difference of 30 degrees, as this is closest to the actual
longitude difference of 35 degrees. The 30 degree longitude difference curve
is the second curve up from the bottom of each graph and is delineated with the
' + ' mark.
iv. For the graph selected in step (i), locate the 5.5 degree satellite inclination
value on the horizontal axis of the graph. Move up vertically until the curve
selected in step (iii) is intercepted, then move left horizontally until the vertical
axis labeled Elevation is reached. Read the required elevation movement off
the vertical axis. For this example, 8 degrees of elevation latitude angle
movement above and below the nominal position is required to track the
satellite.
3.4.3

Setting Limits

The east and/or down limits are set first. The bottom row of the display prompts the user to set the limits
for each axis. To set a limit, position the antenna at the desired limit, and hit either the 7 key to set an
azimuth limit or the 9 key to set an elevation limit. When the east azimuth limit or down elevation limit is
set, the position count for the axis is reset to 30. The limits should be specified so that there is adequate
clearance between the antenna and any obstacles when the antenna is positioned at any
azimuth/elevation combination within the limits. If the actuators are equipped with limit switches, those
switches should be adjusted so that the antenna cannot move outside of the logical limits specified
above.
3.5

Slow Speed Adjustment

The Adapti-Drive slow speed control system allows the user to specify a desired slow speed. When the
antenna is moving at slow speed the controller will vary the voltage to the drive to maintain the actual
antenna slow speed at the value specified by the user. Other slow speed drive systems in use reduce
the voltage to the drive to a constant value whenever slow speed movements occur. This results in poor
speed regulation as the load on the motor varies or as friction in the drive system changes with
temperature.
For the RC2000C the user sets the slow speed for each axis independently by entering a slow speed
code via the appropriate CONFIG mode prompt. This section outlines the procedure for selecting the
appropriate slow speed code. When the system memory is reset the azimuth and elevation slow speed
codes are initialized to 254 (maximum). If the speed code for a given axis is set to 254, the slow speed
system for that axis is disabled, and full voltage is applied to the axis whenever slow speed is selected. If
the speed code is set to 254 and slow speed is selected, the slow banner and a voltage code will be
displayed, but the drive will move at fast speed and the voltage code will not change.
When slow speed movement occurs, the RC2000C determines the speed at which the actuator is moving
by measuring the rate at which position feedback pulses are received for the axis which is being moved.
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas 66218-9680 • USA www.researchconcepts.com
Chapter 3
Figure 3.6
Installation/Setup