Satellite television

Satellite television is television delivered by way of orbiting communications satellites located 37,000 km (22,300 miles) above the earth's surface. The first satellite television signal was relayed from Europe to the Telstar satellite over North America in 1962. The first domestic North American satellite to carry television was Canada's Anik 1, which was launched in 1973.

Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are fixed toward the satellite that its signals will be transmitted to, and are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The signal is transmitted to devices located on-board the satellite called transponders, which retransmit the satellite signal at a lower frequency.

The satellite signal, quite weak after travelling through space, is collected by a parabolic receiving dish, which reflects the weak signal to the dish's focal point and is received and amplified by a device called a low-noise block downconverter, or LNB (Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB).

The signal, now amplified, travels to a satellite receiver box through coaxial cable (RG-6 or RG-10; cannot be standard RG-59) and is converted by a local oscillator to the L-Band range of frequencies (approximately). Special on-board electronics in the receiver box help tune the signal and then convert it to a frequency that a standard television can use.

There are two primary types of satellite television distribution: direct broadcast satellite (DBS) and television receive-only (TVRO).

Direct broadcast satellite, or DBS, is a relatively recent development in the world of television distribution. "Direct broadcast satellite" can either refer to the communications satellites themselves that deliver DBS service or the actual television service. DBS systems are commonly referred to as "minidish" systems. DBS uses the upper portion of Ku-Band.

The first commercial DBS service, Sky Television, was launched in 1989 and served customers in the United Kingdom. Hughes's DirecTV, the first high-powered DBS system, went online in 1994 and was the first North American DBS service. In 1996, Echostar's DISH Network went online in the United States and has gone on to similar success as DirecTV's primary competitor. Commercial DBS services are the primary competition to cable television service.

In Canada, the two DBS services available are Bell Canada's ExpressVu[?] and StarChoice[?].

Television receive-only, or TVRO, refers to satellite television reception equipment that is based primarily on open standards equipment. This contrasts sharply with direct broadcast satellite, which is a completely closed system that uses proprietary reception equipment. TVRO is often referred to as "big dish" satellite television.

TVRO systems are designed to receive analog satellite signals from both C-Band and Ku-Band satellite television or audio signals. 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 Ku-Band only setup. Additional receiver boxes allow for different types of digital satellite signal reception, such as DVB/MPEG-2 and 4DTV.

Direct broadcasting satellites which can be received by what are known in Chinese as little ears have had a major role in breaking the government monopoly of information on Mainland China. Although met with frequent and generally unsuccessful efforts to regulate them, satellite dishes are fairly common in urban Chinese cities. Satellite television has also played an important role in broadcasting to expatriate communities such as Arabs, and overseas Chinese.

See also: satellite dish, microwave antenna[?]

External Links

• DirecTV homepage (http://www.directv.com/)
• DISH Network homepage (http://www.dishnetwork.com/)
• Bell ExpressVu homepage (http://www.expressvu.ca/home.asp) (Canada)
• StarChoice homepage (http://www.starchoice.com/default.asp) (Canada)
• Sky Television homepage (http://www.sky.com/skycom/home/) (U.K.)
• Lyngemark Satellite Charts (http://www.lyngsat.com/)
• TVRO/C-Band FAQ List (http://www.faqs.org/faqs/Satellite-TV/TVRO/)