Satellite dish

A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish used by consumers to receive direct-broadcast satellite television from a direct broadcast satellite in geostationary orbit.

The parabolic shape of a dish reflects the signal to the dish’s focal point. Mounted on brackets at the dish's focal point is a device called a feedhorn. This feedhorn is essentially the front-end of a waveguide that gathers the signals at or near the focal point and 'conducts' them to a low-noise block downconverter or LNB. The LNB converts the signals from electromagnetic or radio waves to electrical signals and shifts the signals from the downlinked C-band and/or K u -band to the L-band range. Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB. A new form of omnidirectional satellite antenna, which does not use a directed parabolic dish and can be used on a mobile platform such as a vehicle was announced by the University of Waterloo in 2004. The theoretical gain (directive gain) of a dish increases as the frequency increases. The actual gain depends on many factors including surface finish, accuracy of shape, feedhorn matching.

In Europe, the frequencies used by DBS services are 10.7–12.75 GHz on two polarisations H (Horizontal) and V (Vertical). This range is divided into a "low band" with 10.7–11.7 GHz, and a "high band" with 11.7–12.75 GHz. This results in two frequency bands, each with a bandwidth of about 1 GHz, each with two possible polarizations. In the LNB they become down converted to 950–2150 MHz, which is the frequency range allocated for the satellite service on the coaxial cable between LNBF and receiver. Lower frequencies are allocated to cable and terrestrial TV, FM radio, etc. Only one of these frequency bands fits on the coaxial cable, so each of these bands needs a separate cable from the LNBF to a switching matrix or the receiver needs to select one of the 4 possibilities at a time. citation needed

In a single receiver residential installation there is a single coaxial cable running from the receiver set-top box in the building to the LNB on the dish. The DC electric power for the LNB is provided through the same coaxial cable conductors that carry the signal to the receiver. In addition, control signals are also transmitted from the receiver to the LNB through the cable. The receiver uses different power supply voltages (13 / 18 V) to select vertical / horizontal antenna polarization, and an on/off pilot tone (22 kHz) to instruct the LNB to select one of the two frequency bands. In larger installations each band and polarization is given its own cable, so there are 4 cables from the LNB to a 'multiswitch' switching matrix, which allows the connection of multiple receivers to the multiswitch in a star topology using the same signalling method as in a single receiver installation. citation needed A satellite finder may aid in aiming the satellite dish. Professional sa

Motor-driven dish edit A dish that is mounted on a pole and driven by a stepper motor or a servo can be controlled and rotated to face any satellite position in the sky. There are three competing standards: DiSEqC, USALS, and 36 V positioners. Many receivers support all of these standards. Motor-driven dishes are popular with enthusiasts. Although there is no problem with equipment pricing, only price for space required for installation. And making the installation wind proof for big size dish. Even standard or small size dishes can be used, however enthusiasts tend to prefer the largest possible sizes (at least 120cm) in order to receive signals from remote weak satellite positions. The cheapest sizes for K u band are up to 120cm. Sizes above 120cm have rapid sharp price increase in comparison to ordinary commercial application for end consumer (ordinary viewer). Although pricing is different for countries where there is no freedom for K u band, and end consumer (ordinary viewer) i

Parabolic antennas referred to as "dish" antennas had been in use long before satellite television. The term "satellite dish" was coined in 1978 during the beginning of the satellite television industry, and came to refer to dish antennas that send and/or receive signals from communications satellites. Taylor Howard of San Andreas, California adapted an ex-military dish in 1976 and became the first person to receive satellite television signals using it. The first satellite television dishes were built to receive signals on the C-band analog, and were very large. The front cover of the 1979 Neiman-Marcus Christmas catalog featured the first home satellite TV stations on sale. The dishes were nearly 20 feet (6.1 m) in diameter. The satellite dishes of the early 1980s were 10 to 16 feet (3.0 to 4.9 m) in diameter and made of fiberglass with an embedded layer of wire mesh or aluminum foil, or solid aluminum or steel. Satellite dishes made of wire mesh first came out in