You first may be instructed to “Set East and West Limits”. This is referring to
the limits of travel for the actuator arm or horizon drive. Although the motor has
a slip clutch to prevent damage when the arm is extended or retracted
completely, it is best to set the receiver’s programmable limits at positions
before the arm reached these points. Many motors come with built-in limit
switches which will shut off the motor at designated points.
Setting the east and west programmable limits.
The receiver’s programmable
limits need to be set to stop the travel of the arm or horizon driver before the
built-in limit switched are engaged or before the drive’s physical limits are
reached. If the arm does reach its full length or is retracted completely the
motor’s slip clutch will start making loud “clicks”. Stop immediately. If the arm
become stuck in this position, take the motor off and insert the blade of heavy
screwdriver in the slot where the motor engages the arm. Turn the screw driver
just enough to loosen the arm, then put the motor back in place.
The idea here is to set the limits so they are just past the last satellite at either
end of the satellite arc but before the mechanical limits of the drive. You can
determine the elevation angles for the last satellite to the east and west.
Setting the polar axis elevation of the dish.
Extend the drive until the dish is
looking at the highest point in the sky. Set the inclinometer onto the polar axis
of the mount to the correct elevation angle for your location.
Setting the declination.
Declination is the offset angle between the polar axis of
the mount and the rim of the dish which permits the antenna to precisely track
the Clarke Orbit. The declination angle at any site is determined by the latitude
at that location. The declination setting must be adjusted to the figure supplied
by the manufacturer for your specific site. If you need to compute the
declination you can find out the approximate value by using the chart.
With a modified polar mount antenna, correct tracking of the total Clarke Orbit
is only possible when the declination has been properly set. Set the
inclinometer on the back plate of the antenna. Using the declination
adjustments on the mount, set the antenna for an elevation angle that is equal
to the polar axis angle plus the number of degrees of declination for your area.
The dish should be looking down slightly from the angle of the mount.
Tracking Procedures
Now is the time to begin tracking the satellites and programming their positions
into memory. This is not difficult now that you have everything set. When
moving the dish to the east or west, the dish’s look angle should now follow a
curve similar to that of the Clarke Orbit.
