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Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.
A satellite receiver then decodes the desired television programme for viewing on a television set. Receivers can be external set-top boxes , or a built-in television tuner. Satellite television provides a wide range of channels and services. It is usually the only television available in many remote geographic areas without terrestrial television or cable television service. Consequently, these systems were nicknamed "big dish" systems, and were more expensive and less popular.
Early systems used analog signals , but modern ones use digital signals which allow transmission of the modern television standard high-definition television , due to the significantly improved spectral efficiency of digital broadcasting.
Different receivers are required for the two types. Some transmissions and channels are unencrypted and therefore free-to-air or free-to-view , while many other channels are transmitted with encryption pay television , requiring the viewer to subscribe and pay a monthly fee to receive the programming. The advantage of this orbit is that the satellite's orbital period equals the rotation rate of the Earth, so the satellite appears at a fixed position in the sky.
Thus the satellite dish antenna which receives the signal can be aimed permanently at the location of the satellite, and does not have to track a moving satellite. Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility.
On occasion, sun outage will occur when the sun lines up directly behind the geostationary satellite to which the receiving antenna is pointed.
The original C-band satellite television systems used a low-noise amplifier LNA connected to the feedhorn at the focal point of the dish. The advantages of using an LNB are that cheaper cable can be used to connect the indoor receiver to the satellite television dish and LNB, and that the technology for handling the signal at L-band and UHF was far cheaper than that for handling the signal at C-band frequencies. This allows for transmission of UHF signals along the same span of coaxial wire at the same time.
The satellite receiver or set-top box demodulates and converts the signals to the desired form outputs for television, audio, data, etc. RG-6 , RG , etc. A practical problem relating to home satellite reception is that an LNB can basically only handle a single receiver.
A common solution for consumers wanting to access multiple satellites is to deploy a single dish with a single LNB and to rotate the dish using an electric motor. The axis of rotation has to be set up in the north-south direction and, depending on the geographical location of the dish, have a specific vertical tilt. 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.
The disk will then be capable of receiving any geostationary satellite that is visible at the specific location, i. The DiSEqC protocol has been extended to encompass commands for steering dish rotors.
There are five major components in a satellite system: Thus satellite dishes can be aimed permanently at that point, and don't need a tracking system to turn to follow a moving satellite. The downlinked satellite signal, weaker after traveling the great distance see inverse-square law , is collected by using a rooftop parabolic receiving dish " satellite dish " , which reflects the weak signal to the dish's focal point.
The reason for using the LNB to do the frequency translation at the dish is so that the signal can be carried into the residence using cheap coaxial cable. To transport the signal into the house at its original K u band microwave frequency would require an expensive waveguide , a metal pipe to carry the radio waves.
An LNB can only handle a single receiver. The set-top box selects the channel desired by the user by filtering that channel from the multiple channels received from the satellite, converts the signal to a lower intermediate frequency , decrypts the encrypted signal, demodulates the radio signal and sends the resulting video signal to the television through a cable.
If the customer fails to pay his monthly bill the box is "deactivated" by a signal from the company, and the system will not work until the company reactivates it.
Some receivers are capable of decrypting the received signal itself. The analog signal is frequency modulated and is converted from an FM signal to what is referred to as baseband. This baseband comprises the video signal and the audio subcarrier s.
The audio subcarrier is further demodulated to provide a raw audio signal. Later signals were digitized television signal or multiplex of signals, typically QPSK. Many conditional access systems have been compromised. An event called sun outage occurs when the sun lines up directly behind the satellite in the field of view of the receiving satellite dish.
During this period, the sun is within the main lobe of the dish's reception pattern, so the strong microwave noise emitted by the sun on the same frequencies used by the satellite's transponders drowns out reception.
Direct-To-Home can either refer to the communications satellites themselves that deliver service or the actual television service. Programming for satellite television channels comes from multiple sources and may include live studio feeds. The signal is then sent to the uplink  where it is transmitted to the satellite.
With some broadcast centers, the studios, administration and up-link are all part of the same campus. Most systems use the DVB-S standard for transmission. While the underlying reception technology is similar, the pay television technology is proprietary, often consisting of a conditional-access module and smart card.
This measure assures satellite television providers that only authorized, paying subscribers have access to pay television content but at the same time can allow free-to-air channels to be viewed even by the people with standard equipment available in the market.
Some countries operate satellite television services which can be received for free, without paying a subscription fee. This is called free-to-air satellite television. Germany is likely the leader in free-to-air with approximately digital channels including 83 HDTV channels and various regional channels broadcast from the Astra All German analogue satellite broadcasts ceased on 30 April The United Kingdom has approximately digital channels including the regional variations of BBC channels, ITV channels, Channel 4 and Channel 5 that are broadcast without encryption from the Astra 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.
It is broadcast from GSAT at The term Television receive-only , or TVRO, arose during the early days of satellite television reception to differentiate it from commercial satellite television uplink and downlink operations transmit and receive. This was the primary method of satellite television transmissions before the satellite television industry shifted, with the launch of higher powered DBS satellites in the early s which transmitted their signals on the K u band frequencies.
TVRO systems were designed to receive analog and digital satellite feeds of both television or audio from both C-band and K u -band transponders on FSS -type satellites. TVRO systems tend to use larger rather than smaller satellite dish antennas, since it is more likely that the owner of a TVRO system would have a C-band-only setup rather than a K u band-only setup.
The narrow beam width of a normal parabolic satellite antenna means it can only receive signals from a single satellite at a time. In 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.
The first public satellite television signals from Europe to North America were relayed via the Telstar satellite over the Atlantic ocean on 23 July , although a test broadcast had taken place almost two weeks earlier on 11 July. The world's first commercial communications satellite, called Intelsat I and nicknamed "Early Bird", was launched into geosynchronous orbit on April 6, 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.
The first in a series of Soviet geostationary satellites to carry direct-to-home television, Ekran 1, was launched on 26 October The satellite television industry developed first in the US from the cable television industry as communication satellites were being used to distribute television programming to remote cable television headends.
Taylor Howard of San Andreas , California became the first person to receive C-band satellite signals with his home-built system in In the US, PBS , a non-profit public broadcasting service, began to distribute its television programming by satellite in In Soviet engineers developed the Moskva or Moscow system of broadcasting and delivering of TV signals via satellites. They launched the Gorizont communication satellites later that same year. These satellites used geostationary orbits.
Early satellite television systems were not very popular due to their expense and large dish size. By , satellite television was well established in the USA and Europe. Advances in receiver technology and the use of gallium arsenide FET technology enabled the use of smaller dishes. Originally, all channels were broadcast in the clear ITC because the equipment necessary to receive the programming was too expensive for consumers. With the growing number of TVRO systems, the program providers and broadcasters had to scramble their signal and develop subscription systems.
In October , the U. Congress passed the Cable Communications Policy Act of , which gave those using TVRO systems the right to receive signals for free unless they were scrambled, and required those who did scramble to make their signals available for a reasonable fee.
The scrambling of HBO was met with much protest from owners of big-dish systems, most of which had no other option at the time for receiving such channels, claiming that clear signals from cable channels would be difficult to receive.
MacDougall in April Videocipher II used analog scrambling on its video signal and Data Encryption Standard —based encryption on its audio signal. VideoCipher II was defeated, and there was a black market for descrambler devices which were initially sold as "test" devices. The necessity for better satellite television programming than TVRO arose in the s. Satellite television services, first in Europe, began transmitting K u band signals in the late s. On 11 December Luxembourg launched Astra 1A , the first satellite to provide medium power satellite coverage to Western Europe.
By , nine channels were scrambled, but 99 others were available free-to-air. Satellite television had also developed in Europe but it initially used low power communication satellites and it required dish sizes of over 1. In the US in the early s, four large cable companies launched PrimeStar , a direct broadcasting company using medium power satellites.
This greatly reduced the popularity of TVRO systems. In the mids, channels began moving their broadcasts to digital television transmission using the DigiCipher conditional access system. Signals from DBS satellites operating in the more recent K u 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.
C-band satellite television signals are less prone to rain fade. In a return to the older but proven technologies of satellite communication, the current DBS-based satellite providers in the USA Dish Network and DirecTV are now utilizing additional capacity on the K u -band transponders of existing FSS-class satellites, in addition to the capacity on their own existing fleets of DBS satellites in orbit. This was done in order to provide more channel capacity for their systems, as required by the increasing number of High-Definition and simulcast local station channels.
It began broadcasting signals using the AsiaSat 1 satellite on 1 January Media related to Satellite television at Wikimedia Commons. From Wikipedia, the free encyclopedia. Radio Stations and Systems — Article 1.
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