You have probably heard about satellite dishes, maybe even seen them. But do you know what a satellite dish does or can do? If not, let us tell you all about satellite dishes, the receivers that are used with the dishes, and low noise blocks or LNBs that are an important component of this arrangement.
A satellite dish is shaped like a parabola and works like an antenna. This dish is designed to capture signals on the microwave frequency from communication satellites in orbit around the world. A satellite dish can be used for both, sending out signals (Satellite TV) as well as work as data transmitters. The parabolic shape of these satellite dishes help to absorb signals to their core or center. The feedhorn or the center-point of the dish is designed to collect and conduct signals to, what is known as, a block down converter. This converter is commonly known as a low noise block or LNB.
LNBs are instrumental in converting the many signals emitted at the various frequencies like radio, electromagnetic etc. The reason for conversion is to make these signals more readable, recognizable. A LNB can also shift signals from low-band frequencies like C, Ku up to L band. If you observe carefully, most of the satellite dish antennas that broadcast directly have a LNBF. A LNBF plays the dual role of a LNB and a feedhorn.
The design of satellite dishes are based on many important principles of physics. One such is that with increase in frequency, the directive gain also increases. Nevertheless, the actual gain depends on several other important factors as well include the material of the dish, its surface finish, the level of accuracy while manufacturing the dish, and the feedhorn. However, some other satellite dishes like those that function on low-band frequencies like C, allow for more flexibility with regards the design and material used. It's safe to say that such dishes are more versatile and offer better performance. Engineers are currently experimenting with the material used to build the large satellite dishes and an outcome of this effort is the use of metal mesh in an all metal frame. Unfortunately, as the frequencies increase, metal mesh becomes redundant.
The satellite dishes used nowadays, especially for DishTV, have a fixed diameter that ranges from 43cm (18 in) - 80cm (31 in). Unidirectional in direction, these dishes communicate with other satellites in orbit on the Ku-bandwidth. Satellite dishes that have 60cm diameter with a gain value of 37.50dB at 11.75 GHz are the most commonly employed commercial purpose antennas.
Another important component of a satellite TV system is the receiver. Satellite receivers are used to do the following:
1. Descramble encrypted signals2. Convert digital formats like MPEG-2 or MPEG-4 signals into readable or analog formats that can be read by your TV3. Pull out channels, one at a time from larger orbiting satellites and 4. Send billing, pay-per-view information etc on a timely basis from the customers to the central command.
With technology, all these components will change and improve, but they will always remain a sound investment.
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