1. Field of the Invention
This invention relates generally to antenna mounts, and more particularly to mounts for aiming a parabolic antenna towards communication satellites in geosynchronous orbit.
2. Description of the Prior Art
There are a great number of communication satellites parked in geosynchronous orbit 22,300 miles above the equator of the earth. Highly directional parabolic antennas are used to receive the signals transmitted from these geosynchronous satellites.
To receive an adequate signal, the parabolic antenna must be accurately aimed at a geosynchronous satellite. To accomplish this task, a number of designs for adjustable antenna mounts have been devised.
Since all of the geosynchronous satellites lie along a plane through the earth's equator, any parabolic antenna in the Northern hemisphere should be pointed south. The angle of elevation of the antenna depends upon the latitude at which it is being used, where the angle of elevation decreases with increasing latitude. The antenna should also be able to sweep along the satellite belt so that it may be aimed at the desired geosynchronous satellite.
A great many antenna mounts have been devised which are used to aim a parabolic antenna towards a geosynchronous satellite. Most fall into two main categories. A first category of antenna mount utilizes a number of legs to support the antenna, where two or more of the legs are adjustable to provide the proper elevation of the antenna and to align the axis rotation of the antenna with a vertical plane.
A problem with this type of antenna mount is that it is very difficult to set the mounts accurately, and any error in setting the mount will make proper tracking with the antenna impossible. The difficulty of setting up the first type of mount is compounded by the fact that adjustment of one of the legs will often cause the other adjustable leg(s) to become unadjusted.
The other major type of antenna mount utilizes a single support pole having a head which permits rotation for North/South orientation, and for the proper elevation. If, however, the post is not set exactly vertical, tracking becomes once again impossible.
Examples of tripodal mounts for parabolic dishes can be found in U.S. Pat. No. 3,945,015 of Guegeun, and U.S. Pat. No. 4,086,599 of VanderLinden, Jr. et al. The Gueouen patent describes a support structure for an antenna mounted at three points on a steering mounting resting on the ground. One of the points is situated at the apex of the support frame and is provided with a bi-directional joint which allows the antenna to pivot around an azimuthal and elevational axes. The bi-directional joint is mounted to pivot on the base mounting around an axis which is perpendicular to the azimuthal and elevational axes. The VanderLinden, Jr. et al. patent describes a composite antenna which is secured to a foundation by a multi-element truss-like pedestal. The pedestal provides elevation and azimuth rotational axes for selecting and adjusting the reflector point orientation.