Satellite Tv Service

Everyone has seen them; the small, mostly round antennas pointing a central finger towards the sky. The small ones are found in yards and on rooftops, particularly out in the countryside. A few of the big ones are out there still as well, but most of the big ones are parked behind the local Cable Television office or television station. They are called dish antennas, or more properly parabolic reflector antennas. They are used to receive microwave transmissions from (or send the same to) satellites. The most commonly seen ones today are used to take television broadcasts from one point to many points on the earth's surface.

A dish antenna is used to receive direct broadcast satellite (DBS) signals because of the low relative strength of that signal at the earth's surface. The reflective portion of the antenna (the actual dish) reflects the signal back to the actual antenna and concentrates the signal at that antenna. The dish is a parabola so that the reflected signal waves are all in step at the antenna receiver so that there is maximum concentration of the signal. In older systems (particularly the C Band antennas) the parabolic dish had a wave guide antennal at the focal point to further ensure that the signal waves were all in step. The modern DBS dish antenna uses an LNB (Low-Noise Block downcoverter) to electronically ensure that the signal waves are in step. In either case a cable is then used to transmit the signal to the converter box where the signal is decrypted and converted to a signal that the television set can use.

The reflective portion of the dish needs to be made of metal, though not necessarily solid metal. The smaller antennas used for DBS home receivers appear to be plastic, but plastic is a poor reflector of microwave radiation. The plastic covers a wire mesh with a small enough distance between the wires that essentially no microwave radiation passes through the mesh. This plastic/wire mess system is structurally sound, reflects well and is very light. These combine to make it easy to install on rooftops or walls without affecting the structural integrity of the building it is mounted upon.

The new DBS satellite dishes have a fixed aim-point. They are pointed directly at the satellite servicing that system. The Dish Network has developed a dual-LNB system (Dish 500) that can use one dish to point at two different satellites at fairly large distance between the two satellites (110°W longitude and 119°W longitude) and a tri-LNB (Dish 1000) system that points at three separate satellites. This greatly increases the number of potential channels that can be received by these antennas. The Dish 500 and Dish 1000 antennas are still considered fixed aim-point antennas. The older C Band antennas, on the other hand, had motorized bases and controller systems that allowed them to be pointed at different satellites to receive different stations.

While various forms of electronic antennas are being developed for mobile applications it looks like the ubiquitous dish antenna will be around for satellite television reception for the foreseeable future. It is simple, effective and easy to maintain. Who could ask for more?