8. Connecting an antenna system with a positioner
USALS type positioners manufactured by Stab will guarantee the correct operation of your
Ferguson receiver. In order to connect an antenna system to a USALS positioner, you should
connect the positioner out to the LNB IN of the Ferguson receiver. The role of the positioner
installed between the mast and the antenna is to turn the bowl in such a way as to ensure that
it is directed to various satellite positions. The positioner is built in such a way that its axis of
revolution is parallel to the direction towards the North Star. For this reason, its mounting is
frequently termed the Polar mount. In consequence, when the satellite changes position, it is
not necessary to adjust the azimuth and elevation independently. The antenna revolves only in
one axis. Using the introduced scale, the motor inclines in such a way as to ensure the
appropriate placement of the axis of revolution. The angle of inclination corresponds to the
latitude of the location where the antenna is installed. As in the case of a fixed antenna, the
angle of elevation of the bowl must first be set. For this purpose, use is made of a satellite
located as close as possible to the south of your location. Ideally, the position of the satellite
should not differ from that of the said direction by more than 5°. In other words, you should use
the satellite position closest to the longitude of the point of installation. For example, if your
longitude is 73° W, you should search for a satellite located at a position between 68° and 78°
W.
The USALS function considerably simplifies configuration of the antenna. The Ferguson receiver
requires that you enter the geographical coordinates of the antenna in order to automatically
calculate the angle of revolution of the motor for individual satellites. The receiver activates the
positioner automatically and turns the antenna to the selected satellite. When a signal is locked
on, you should precisely adjust the antenna's elevation and azimuth settings in order to
optimise signal reception. When correcting the azimuth, the entire antenna assembly and
positioner revolve with respect to the mast. If initially the antenna was not directed precisely
south, you can correct this now. When you have finished with the first satellite, all other
satellites will be remembered automatically, provided that you have introduced their satellite
position values correctly.
Without the USALS function, programming of the system is much more difficult. To this end you
should use the DiSEqC 1.2 function, which turns the antenna to the selected satellite in a nearly
identical manner. Since, however, it does not take into consideration the local geographical
coordinates, the movement is effected on the basis of the prime meridian and the equator.
Therefore it is necessary to introduce corrections separately for each satellite. Due to these
difficulties, manufacturers of DiSEqC 1.2 positioners frequently provide useful software on their
websites, using which you can easily calculate the location of the satellite.
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