Concept

Satellite dish

Résumé

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 which receives direct-broadcast satellite television from a direct broadcast satellite in geostationary orbit. 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 in diameter. The satellite dishes of the early 1980s were in diameter and made of fiberglass with an embedded layer of wire mesh or aluminium foil, or solid aluminium or steel. Satellite dishes made of wire mesh first came out in the early 1980s, and were at first in diameter. As the front-end technology improved and the noise figure of the LNBs fell, the size shrank to a few years later, and continued to get smaller reducing to feet by the late 1980s and by the early 1990s. Larger dishes continued to be used, however. In December 1988, Luxembourg's Astra 1A satellite began transmitting analog television signals on the Ku band for the European market. This allowed small dishes (90 cm) to be used reliably for the first time. In the early 1990s, four large American cable companies founded PrimeStar, a direct broadcasting company using medium power satellites. The relatively strong Ku band transmissions allowed the use of dishes as small as 90 cm for the first time. On 4 March 1996, EchoStar introduced Digital Sky Highway (Dish Network).

Source officielle

https://en.wikipedia.org/wiki/Satellite_dish

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Satellite dish

Ion temperature spectroscopic measurements in high rotation discharges by means of X-ray diagnostic at JET

Sun-synchronous repeat ground tracks and other useful orbits for future space missions

Ion temperature spectroscopic measurements in high rotation discharges by means of X-ray diagnostic at JET

Sun-synchronous repeat ground tracks and other useful orbits for future space missions