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Direct-broadcast satellite television

  (Redirected from Direct broadcast satellite)
A DTH dish antenna mounted on wall

Direct-broadcast satellite television (DBSTV) also known as Direct-to-home television (DTHTV) is a type of communications satellites which usually broadcasts satellite television signals for home reception using dish antennas, satellite ground stations transmit the signals.

All the major services including DirecTV, Dish Network, Bell TV, Shaw Direct, and Sky use direct-broadcast satellites. Signals are transmitted using Ku band and are completely digital which means they have high picture and stereo sound quality.

Prior to the arrival of DBS services in the early to mid-1990s signals were sent from fixed service satellites on the C-band analog and received with television receive-only systems, which had more disadvantages including the requirement of large satellite dishes.

DBS satellite dishes installed on an apartment complex.

In Europe, prior to the launch of Astra 1A in 1988, the term DBS was commonly used to describe the nationally commissioned satellites planned and launched to provide television broadcasts to the home within several European countries (such as BSB in the United Kingdom and TV-Sat in Germany). These services were to use the D-Mac and D2-Mac format and BSS frequencies with circular polarization from orbital positions allocated to each country. Before these DBS satellites, home satellite television in Europe was limited to a few channels, really intended for cable distribution, and requiring dishes typically of 1.7 m.

SES launched the Astra 1A satellite to provide services to homes across Europe receivable on dishes of just 90 cm and, although these mostly used PAL video format and FSS frequencies with linear polarization, the DBS name slowly came to be applied to all Astra satellites and services too.

Contents

TechnologyEdit

 
Rear view of a linear polarised LNB.
 
Corrugated feedhorn and LNB on a Hughes DirecWay satellite dish.

There are five major components in a DBS satellite system: the programming source, the broadcast center, the satellite, the satellite dish, and the receiver. "Direct broadcast" satellites used for transmission of satellite television signals are generally in geostationary orbit 37,000 km (23,000 mi) above the earth's equator.[1] The reason for using this orbit is that the satellite circles the Earth at the same rate as the Earth rotates, so the satellite appears at a fixed point in the sky. Thus satellite dishes can be aimed permanently at that point, and don't need a tracking system to turn to follow a moving satellite. A few satellite TV systems use satellites in a Molniya orbit, a highly elliptical orbit with inclination of +/-63.4 degrees and orbital period of about twelve hours.

Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility.[1] 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.[1] Uplink satellite dishes are very large, often as much as 9 to 12 metres (30 to 40 feet) in diameter[1] to achieve accurate aiming and increased signal strength at the satellite, to improve reliability.[1] The uplink dish is pointed toward a specific satellite and the uplinked signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range aboard that satellite.[1] 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.[1]

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.[2] Mounted on brackets at the dish's focal point is a feedhorn[2] which passes the signals through a waveguide to a device called a low-noise block converter (LNB) or low noise converter (LNC) attached to the horn.[2] The LNB amplifies the weak signals, filters the block of frequencies in which the satellite television signals are transmitted, and converts the block of frequencies to a lower frequency range in the L-band range.[2] The signal is then passed through a coaxial cable into the residence to the satellite television receiver, a set-top box next to the television.

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 Ku band microwave frequency would require an expensive waveguide, a metal pipe to carry the radio waves.[3] The cable connecting the receiver to the LNB are of the low loss type RG-6, quad shield RG-6, or RG-11.[4] 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.[4] The shift to more affordable technology from the 50 Ohm impedance cable and N-Connectors of the early C-Band systems to the cheaper 75 Ohm technology and F-Connectors allowed the early satellite television receivers to use, what were in reality, modified UHF television tuners which selected the satellite television channel for down conversion to another lower intermediate frequency centered on 70 MHz where it was demodulated.[3]

An LNB can only handle a single receiver.[5] This is due to the fact that the LNB is mapping two different circular polarisations – right hand and left hand – and in the case of the Ku-band two different reception bands – lower and upper – to one and the same frequency band on the cable, and is a practical problem for home satellite reception.[5] Depending on which frequency a transponder is transmitting at and on what polarisation it is using, the satellite receiver has to switch the LNB into one of four different modes in order to receive a specific desired program on a specific transponder.[5] The receiver uses the DiSEqC protocol to control the LNB mode, which handles this.[5] If several satellite receivers are to be attached to a single dish a so-called multiswitch must be used in conjunction with a special type of LNB.[5] There are also LNBs available with a multiswitch already integrated.[5] This problem becomes more complicated when several receivers use several dishes or several LNBs mounted in a single dish are aimed at different satellites.[5]

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.[4] To decrypt the signal the receiver box must be "activated" by the satellite company. 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. These receivers are called integrated receiver/decoders or IRDs.[4]

Sun outageEdit

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.[6] This happens for about a 10 minute period daily around midday, twice every year for a two-week period in the spring and fall around the equinox. 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.[6]

HistoryEdit

The necessity for better satellite television programming than TVRO arose in the 1980s. Satellite television services, first in Europe, began transmitting Ku band signals in the late 1980s. On 11 December 1988 Luxembourg launched Astra 1A, the first satellite to provide medium power satellite coverage to Western Europe.[7] This was one of the first medium-powered satellites, transmitting signals in Ku band and allowing reception with small(90 cm) dishes for the first time ever.[7] The launch of Astra beat the winner of the UK's state Direct Broadcast Satellite licence, British Satellite Broadcasting, to the market, and accelerated its demise.[7]

In the early 1990s, four large American cable companies launched PrimeStar, a direct broadcasting company using medium-power satellites.[8] The relatively strong transissions allowed the use of smaller (90 cm) dishes for the first time in North America.[8] Its popularity declined with the 1994 launch of Hughes' DirecTV.[9] DirecTV acquired USSB on 14 December 1998 for $1.3 billion and PrimeStar in 1999 for $1.83 billion.[10]

On 4 March 1996 EchoStar introduced Digital Sky Highway (Dish Network) using the EchoStar 1 satellite.[11] EchoStar launched a second satellite in September 1996 to increase the number of channels available on Dish Network to 170.[11] These systems provided better pictures and stereo sound on 150–200 video and audio channels, and also allowed small dishes to be used.[11] This, along with the widespread availability of DBS services and advances in noise reduction as a result of improved microwave technology and semiconductor materials ended the popularity of TVRO systems.[12] In the mid-1990s, channels began moving their broadcasts to digital television transmission using the DigiCipher conditional access system.[13]

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 analogue modulation methods.[14] Each satellite also can carry up to 32 transponders in the Ku band, but only 24 in the C band, and several digital subchannels can be multiplexed (MCPC) or carried separately (SCPC) on a single transponder.[12] Advances in noise reduction due to improved microwave technology and semiconductor materials also had an effect.[12] One consequence of the higher frequencies used for DBS services is rain fade. where viewers lose signal during a heavy downpour. Ku band signals are more vulnerable to rain fade than C-band signals.[15]

On 29 November 1999 US President Bill Clinton passed the Satellite Home Viewer Improvement Act (SHVIA).[16] The act allowed Americans to receive local broadcast signals via direct broadcast satellite systems for the first time.[16]

Satellite Television for the Asian Region (STAR), a service based in Hong Kong which now provides satellite TV coverage to Asia and Australia, introduced satellite TV to the Asian region in the early 1990s. It began broadcasting signals using the AsiaSat 1 satellite on 1 January 1991.[citation needed]

Commercial servicesEdit

 
Astro satellite dishes

The second commercial satellite television service, Sky Television plc (now BSkyB after its merger with British Satellite Broadcasting's five-channel network), was launched in 1989. Sky TV started as a four-channel free-to-air analogue service on the Astra 1A satellite, serving both Ireland and the United Kingdom.[17] By 1991, Sky had changed to a conditional access pay model, and it launched a digital service, Sky Digital, in 1998, with analogue transmission ceasing in 2001. Since the DBS nomenclature is rarely used in the UK or Ireland, the popularity of Sky's service has caused the terms "minidish" and "digibox" to be applied to products other than Sky's hardware. News Corporation has a 32% stake in BSkyB.

PrimeStar began transmitting an analog service to North America in 1991, and was joined by DirecTV (then owned by a division of General Motors, GM Hughes Electronics), in 1994. At the time, DirecTV's introduction was the most successful consumer electronics debut in American history. Although PrimeStar transitioned to a digital system in 1994, it was ultimately unable to compete with DirecTV, which required a smaller satellite dish and could deliver more programming. DirecTV purchased PrimeStar in 1999 and moved all of that provider's subscribers to DirecTV equipment. In a series of transactions consummated in 2003, Hughes Electronics was spun out of GM and the News Corporation purchased a controlling interest in the new company, which was renamed The DIRECTV Group. In 2008, Liberty Media Corporation purchased News Corporation's controlling interest in DirecTV.

In 1996, EchoStar's Dish Network went online in the United States and, as DirecTV's primary competitor, achieved similar success. AlphaStar also started but soon went under. Astro was also started, using a direct broadcast satellite system.

Dominion Video Satellite Inc.'s Sky Angel launched on a satellite platform in the United States in 1996, with its DBS service geared toward the faith and family market. It grew from six to 36 television and radio channels of family entertainment, Christian-inspirational programming, and 24-hour news services. Dominion, under its former corporate name Video Satellite Systems Inc., was actually the second from among the first nine companies to apply to the FCC for a high-power DBS license in 1981, and it was the sole surviving DBS company from the first round of applicants until the sale of their license to EchoStar Communications Corporation in 2007 and departure from satellite distribution in 2008. Sky Angel, although a separate and independent DBS service, used the same satellites, transmission facilities and receiving equipment used for Dish Network through an agreement with Echostar. Because of this, Sky Angel subscribers also had the option of subscribing to Dish Network's channels as well.

In 2003, EchoStar attempted to purchase DirecTV, but the FCC and U.S. Department of Justice denied the purchase based on anti-competitive concerns.

As of 2013, India has the most competitive direct-broadcast satellite market with seven operators (six private and one government-owned) vying for more than 110 million television homes. Subscribers to India's six private direct-to-home (DTH) satellite television providers have now reached 56.5 million, according to the latest figures issued by the Telecom Regulations Authority of India (TRAI)on 31 March 2013.[1]

Free-to-air satellite televisionEdit

 
Mahabir Pun hand-making a satellite dish in Nepal

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 250 digital channels (including 83 HDTV channels and various regional channels) broadcast from the Astra 19.2°E satellite constellation.[18] These are not marketed as a DBS service, but are received in approximately 18 million homes, as well as in any home using the Sky Deutschland commercial DBS system. All German analogue satellite broadcasts ceased on 30 April 2012.[19][20]

The United Kingdom has approximately 160 digital channels (including the regional variations of BBC channels, ITV channels, Channel 4 and Channel 5) are broadcast without encryption from the Astra 28.2°E satellite constellation, and receivable on any DVB-S receiver (a DVB-S2 receiver is required for certain high definition television services). Most of these channels are included within the Sky EPG, and an increasing number within the Freesat EPG.

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-15 at 93.5°E and contains about 80 FTA channels.

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). Other FTA satellites include AMC-4, AMC-6, Galaxy 18, and Satmex 5. A company called GloryStar promotes FTA religious broadcasters on Galaxy 19.

See alsoEdit

ReferencesEdit

  1. ^ a b c d e f g Pattan, Bruno (31 March 1993). Satellite Systems:Principles and Technologies. Berlin: Springer Science & Business Media. ISBN 9780442013578. Retrieved 29 July 2014. 
  2. ^ a b c d Minoli, Daniel (3 February 2009). Satellite Systems Engineering in an IPv6 Environment. Boca Raton, Florida: CRC Press. ISBN 978-1420078688. Retrieved 29 July 2014. 
  3. ^ a b "Microwave Journal International". Microwave Journal International. Horizon House. 43 (10–12): 26–28. 2000. Retrieved 28 July 2014. 
  4. ^ a b c d Dodd, Annabel Z. (2002). The Essential Guide to Telecommunications (5th ed.). Upper Saddle River, New Jersey: Prentice Hall. p. 307-10. ISBN 0130649074. Retrieved 29 July 2014. 
  5. ^ a b c d e f g Fox, Barry (1995). "Leaky dishes drown out terrestrial TV". New Scientist. Reed Business Information. 145: 19–22. Retrieved 28 July 2014. 
  6. ^ a b Tirró, S. (30 June 1993). Satellite Communication Systems Design. Berlin: Springer Science & Business Media. p. 279-80. ISBN 978-0306441479. Retrieved 29 July 2014. 
  7. ^ a b c "ASTRA 1A Satellite details 1988-109B NORAD 19688". N2YO. 9 July 2014. Retrieved 12 July 2014. 
  8. ^ a b Ray, Justin (7 May 2002). "DirecTV-5 broadcasting satellite launched by Proton". Spaceflightnow.com. Spaceflight Now, Inc. Retrieved 30 July 2014. 
  9. ^ Cory Grice (December 14, 1998). "Hughes buys satellite firm for $1.3 billion". CNET news. 
  10. ^ Joanna Glasner (January 22, 1999). "DirecTV Buys PrimeStar". Wired. Archived from the original on 2011-05-07. 
  11. ^ a b c Grant, August E. Communication Technology Update (10th ed.). Taylor & Francis. p. 87. ISBN 978-0-240-81475-9. 
  12. ^ a b c Khaplil, Vidya R.; Bhalachandra, Anjali R. (April 2008). Advances in Recent Trends in Communication and Networks. New Delhi: Allied Publishers. p. 119. ISBN 1466651709. Retrieved 16 July 2014. 
  13. ^ Bell-Jones, Robin; Berbner, Jochen; Chai, Jianfeng; Farstad, Thomas; Pham, Minh (June 2001). "High Technology Strategy and Entrepreneurship" (PDF). INSEAD journal. Fontainebleau: INSEAD. Archived from the original (PDF) on 2014-07-24. 
  14. ^ Mirabito, M.,& Morgenstern, B. (2004). Satellites: Operations and Applications. The New Communication Technologies (fifth edition). Burlington: Focal Press.
  15. ^ "Rain fade: satellite TV signal and adverse weather". Dish-cable.com. Dish-cable.com. 2010. Retrieved 16 July 2014. 
  16. ^ a b Satellite Home Viewer Improvement Act, Act No. 00-96 of 29 November 1999 (in english language). Retrieved on 30 July 2014.
  17. ^ "Chronomedia Index". 10 March 2011. 
  18. ^ "Satellitenfernsehen in Deutschland" [Satellite TV in Germany]. kabelfernsehen-kabelanschluss.de (in German). Retrieved 5 April 2016. 
  19. ^ "ZDFneo, 3sat, BR, NDR, SWR, WDR, Phoenix, KiKa starten HD Kanäle" [ZDFneo, 3sat, BR, NDR, SWR, WDR, Phoenix, KiKa launch HD channels]. kabel-internet-telefon.de (in German). 13 March 2012. Retrieved 8 April 2012. 
  20. ^ "HDTV: Neue HD-Kanäle von ARD und ZDF ab 30. April 2012" [HDTV: New HD channels from ARD and ZDF after 30 April 2012]. T-online.de (in German). 20 January 2012. Retrieved 8 April 2012.