SATELLITE RADIO
Satellites are one of the greatest achievements of mankind. They have been used for various applications like communication, military application, weather forecasting and so on. They play a big role in the case of television channels and other entertainment networks. One of the latest applications of satellites is the satellite radio. Satellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations
Satellite radio is a subscriber based radio service that broadcast directly from satellites. It is an advanced form of mobile radio service where one can receive compact disc quality music and other entertainment channels. Even if the person is miles away from the radio station, the quality of the program is not affected. The paper deals with the basic structure of the satellite radio and its transmission and reception procedures.
SETELLITE
A satellite is an object that goes around, or orbits, a larger object, such as a planet. While there are natural satellites, like the Moon, hundreds of man-made satellites also orbit the Earth.
Communications antennae, radio receivers and transmitters enable the satellite to communicate with one or more ground stations, called command centers. Messages sent to the satellite from a ground station are "uplinked"; messages transmitted from the satellite to Earth are "downlinked."
How are satellites launched?
The trick when launching a satellite is to get it high enough to do its job without losing the capsule to outer space. It's a delicate balance of push and pull, accomplished by the inertia of the moving object and the Earth's gravity. If you launch a satellite at 17,000 mph, the forward momentum will balance gravity, and it will circle the earth. On the other hand, if the satellite is launched faster then 23,500 mph, it will leave the gravitational pull of the Earth.
REDIO
Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light.[1] Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, phase, or pulse width. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.
Definitions of Satellite radio
· A satellite radio or subscription radio (SR) is a digital radio signal that is broadcast by a communications satellite, which covers a much wider geographical range than terrestrial radio signals
System design
Satellite radio uses the 2.3GHz S band in North America and generally shares the 1.4GHz L band with local Digital Audio Broadcasting (DAB) stations elsewhere. It is a type of direct broadcast satellite and is strong enough that it requires no satellite dish to receive. Curvature of the earth limits the reach of the signal, but due to the high orbit of the satellites, two or three are usually sufficient to provide coverage for an entire continent.
A satellite radio is basically a digital radio that receives signals broadcast by communications satellite. This allows a person with a radio to follow his favourite satellite radio stations anywhere in the country unlike the terrestrial radio (AM and FM) whose signals are limited to a certain area depending on the power of the station. Some of the advantages of a satellite radio are that the sound is of digital quality and there are no commercials.
But satellite radio is not for free, it is available on subscription for a fee.
"Our endeavour and priority in India is to educate the consumer and create awareness of the benefits of the product and our services across the region," says Andy Ras-Work,
Worldwide COO, WorldSpace Satellite Radio. Currently WorldSpace is the only satellite radio offering its services in the country. It has a base of around 60,000 subscribers to its bouquet of 40 radio stations playing a wide variety of entertainment, news and music genres, he says.
In India satellite radio is largely limited to connoisseurs of music who don't like commercials. "The biggest challenge the medium faces currently is the lack of understanding of the concept and its features. That's the reason we are focusing on expanding our reach and educating music lovers across the country on the value proposition that we offer them," says Ras-Work.
With an aim to reach out to the masses, WorldSpace besides its campaigns in print, radio and outdoor advertising (billboards scream, "Radio is back!"), has its salesmen going door-to-door selling the concept.
There is a healthy debate in the US between terrestrial and satellite radio providers with the former claiming that it is the traditional form of radio that caters to the local audience with a local feel.
A listener of a satellite radio cannot get local radio stations. In other words, a Bengali or a Tamilian living in Delhi [ Images ] can tune in to satellite radio channels of their choice on the receiver, but cannot listen to a local station.
Although popular in malls and some petrol stations, the concept of satellite radio is yet to catch the fancy of individual households in India. There are some problems, says a user. The Yagi antenna needs to be fitted in open space, preferably on top of the building and it is thus prone to be tampered. Paying subscription too is not easy, as one has to pay it online or by cheque to WorldSpace office and wait for the password. Although the music quality is very good, commercials have been replaced by WorldSpace's own promos, which are no less irritating, he says.
With Indians adopting the latest global technologies, and in fact in many cases dictating the way technologies are developing worldwide, WorldSpace believes, it is only a matter of time before satellite radio is well entrenched in the mindshare of people across the country. Satellite radio is yet to catch up, but it is not long before, like in western countries, car manufacturers in India also start installing satellite radio receivers to cater to a larger demand.
Portable Satellite Radio
Portable satellite radios let you listen to satellite radio just about anywhere you go. They are very similar to standard portable music players, designed for music on the go. These however, feature built-in antennas that receive the satellite signal, and come with rechargeable batteries. In fact, all you have to do is plug in headphones, and you can easily listen to and carry them around easily. Reception can be tricky however, being blocked by buildings and tall trees, and sometimes by your own body depending you the way you are facing and how you are carrying it. However, the best reception will be received outdoors in the open
Satellite Radio Systems
Satellite radio is an idea over a decade in the making. In 1992, the U.S. Federal Communications Commission (FCC) allocated a spectrum in the "S" band (2.3 GHz) for nationwide broadcasting of satellite-based Digital Audio Radio Service (DARS). Only four companies applied for a license to broadcast over that band. The FCC gave licenses to two of these companies in 1997. CD Radio (later Sirius Satellite Radio) and American Mobile Radio (later XM Satellite Radio) paid more than $80 million each to use space in the S-band for digital satellite transmission.
Satellite radio companies are comparing the significance of their service to the impact that cable TV had on television 30 years ago. Listeners aren't able to pick up local stations using satellite radio services, but they have access to hundreds of stations offering a variety of music genres. Each company has a different plan for its broadcasting system, but the systems do share similarities. Here are the key components of the two satellite radio systems: Satellite radio works a lot like satellite TV -- you purchase a receiver and pay a monthly subscription fee for a certain number of channels.
History of Satellite Radio:
The history of satellite radio dates back to 1992. Till around this time, radio services were provided by commercial ventures. They were largely subscription-based and subject to the clarity permitted by proprietary signals and specialized hardware. Sound reception was dictated by the extent of decoding and playback demanded over a specific population density. Most earlier providers of radio frequencies did cover news and weather updates, reports from the world of sports and music as well as stock market readings. However, most of the time broadcasts were subject to weather conditions and proximity to structural obstructions. But, all this changed with the advent and commercial use of the satellite radio. The use of orbiting satellites to refine sound quality and frequencies slowly replaced the redundant Digital Audio Broadcasting and HD Radio.
In 1992, XM Radio and Sirius became the first companies to earn FCC licenses, to commercially manufacture and facilitate the use of satellite radios. These two companies delivered SDARS or Satellite Digital Audio Radio Services across the United States of America. The venture took around a decade since inception was to be delivered. Finally, in 2001 digital satellite radio was launched nationwide. XM is recognized as the first to deliver the national digital satellite radio service, beginning with over 100 channels. Today, the pioneer caters to demands in music, current affairs, celebrity controversies, sports, science and children's programs through more than 170 channels. Satellite radio is now encoded using the state-of-the-art CT-aacPlus technology. The highly digitized CD quality not only delivers robust and crisp radio signals, but also proves its superiority over analog radio signals, with little or no loss of signal quality.
Satellite radio is facilitated from impressive recording studios and stations. These studios are empowered by flawless sound quality delivered on account of satellite broadcasters set in geo-stationary orbits. Higher elevations and inclination angles around 60 degrees are consistently sought to enable access to a clearer 'line of sight' and fewer structural obstructions. The use of a number of omni-directional arrays and high quality land based repeaters located at various select locations, guarantee reception of optimum satellite frequencies. Companies providing the satellite radio services are now equipped with transportable and vehicle mount antennas, to take receiver-configurations to the next level. Satellite radio, like AM, is an evolutionary stage in the life of the radio industry. Like FM grew out of AM, satellite radio too, is paving the way for further innovation in spectrum technology.