Satellite television
[1] The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter.
These systems received weaker analog signals transmitted in the C-band (4–8 GHz) from FSS type satellites, requiring the use of large 2–3-meter dishes.
[12] The feedhorn is a section of waveguide with a flared front-end that gathers the signals at or near the focal point and conducts them to a probe or pickup connected to a low-noise block downconverter (LNB).
[13] The original C-band satellite television systems used a low-noise amplifier (LNA) connected to the feedhorn at the focal point of the dish.
[16] This shift allowed the satellite television DTH industry to change from being a largely hobbyist one where only small numbers of systems costing thousands of US dollars were built, to a far more commercial one of mass production.
[16] In the United States, service providers use the intermediate frequency ranges of 950–2150 MHz to carry the signal from the LNBF at the dish down to the receiver.
[citation needed] The satellite receiver or set-top box demodulates and converts the signals to the desired form (outputs for television, audio, data, etc.).
[13] RG-59 is not recommended for this application as it is not technically designed to carry frequencies above 950 MHz, but may work in some circumstances, depending on the quality of the coaxial wire, signal levels, cable length, etc.
Set up properly the motorized dish when turned will sweep across all possible positions for satellites lined up along the geostationary orbit directly above the equator.
[20] Uplink facilities transmit the signal to the satellite over a narrow beam of microwaves, typically in the C-band frequency range due to its resistance to rain fade.
[20] The transponder then converts the signals to Ku band, a process known as "translation," and transmits them back to earth to be received by home satellite stations.
To transport the signal into the house at its original Ku band microwave frequency would require an expensive waveguide, a metal pipe to carry the radio waves.
[22] RG-59 is not recommended for this application as it is not technically designed to carry frequencies above 950 MHz, but will work in many circumstances, depending on the quality of the coaxial wire.
In general, digital television, including that transmitted via satellites, is based on open standards such as MPEG and DVB-S/DVB-S2 or ISDB-S.[citation needed] The conditional access encryption/scrambling methods include NDS, BISS, Conax, Digicipher, Irdeto, Cryptoworks, DG Crypt, Beta digital, SECA Mediaguard, Logiways, Nagravision, PowerVu, Viaccess, Videocipher, and VideoGuard.
[24] Signals are transmitted using Ku band (12 to 18 GHz) and are completely digital which means it has high picture and stereo sound quality.
India's national broadcaster, Doordarshan, promotes a free-to-air DBS package as "DD Free Dish", which is provided as in-fill for the country's terrestrial transmission network.
While originally launched as backhaul for their digital terrestrial television service, a large number of French channels are free-to-air on satellites at 5°W, and have recently been announced as being official in-fill for the DTT network.
In North America (United States, Canada and Mexico) there are over 80 FTA digital channels available on Galaxy 19 (with the majority being ethnic or religious in nature).
These early TVRO systems operated mainly on the C-band frequencies and the dishes required were large; typically over 3 meters (10 ft) in diameter.
[39] In 1945 British science fiction writer Arthur C. Clarke proposed a worldwide communications system which would function by means of three satellites equally spaced apart in Earth orbit.
[47] The subsequent first geostationary Syncom 3, orbiting near the International Date Line, was used to telecast the 1964 Olympic Games from Tokyo to the United States.
[48][49] The world's first commercial communications satellite, called Intelsat I and nicknamed "Early Bird", was launched into geosynchronous orbit on April 6, 1965.
The transmissions were focused on the Indian subcontinent but experimenters were able to receive the signal in Western Europe using home constructed equipment that drew on UHF television design techniques already in use.
[66] The Society for Private and Commercial Earth Stations (SPACE), an organisation which represented consumers and satellite TV system owners, was established in 1980.
[68] The satellite television dishes of the systems in the late 1970s and early 1980s were 10 to 16 feet (3.0 to 4.9 m) in diameter,[69] made of fibreglass or solid aluminum or steel,[70] and in the United States cost more than $5,000, sometimes as much as $10,000.
[76] People in areas without local broadcast stations or cable television service could obtain good-quality reception with no monthly fees.
Commercial satellite broadcasts have existed in Japan since 1992 led by NHK which is influential in the development of regulations and has access to government funding for research.
Their entry into the market was protected by the Ministry of Posts and Telecommunications (MPT) resulting in the WOWOW channel that is encrypted and can be accessed from NHK dishes with a decoder.
[86] In addition to encryption, the widespread availability, in the US, of DBS services such as PrimeStar and DirecTV had been reducing the popularity of TVRO systems since the early 1990s.
Signals from DBS satellites (operating in the more recent Ku band) are higher in both frequency and power (due to improvements in the solar panels and energy efficiency of modern satellites) and therefore require much smaller dishes than C-band, and the digital modulation methods now used require less signal strength at the receiver than analog modulation methods.
