Electromagnetic Wave

Radio wave is electromagnetic wave. We know longitudinal wave and transversal wave also. The wave concept is from basic math for physical phenomena. It explains how the wave moves, interact, and get deflected. All waves are f = f (xąvt),it’s a math, and when you need math help,you can find online math tutor that will help you a lot about this in the internet. Wave is not an easy part of math and physic,but with online math tutoring, you’ll get the answer quickly.

Actually to learn radio wave with online math help is one of the way to get the science. You can try books, but you still need direct tutorial. You can find free online math tutoring to get the basic understanding for radio wave.then you can explore the knowledge by yourself. Internet helps you a lot for this kind of problem, and free online math help is a nice move to start. Online math help is helping you not only with the radio wave and math,but also interact with people and that is important, considering some of scientist are never actually meet real people but numbers.

Back to topic, radiowave is somehow around us and we can take advantages by using it wisely. For the sake of science,that all we have and we know are for the human prosperity and the everlasting world for our next generations.

Satellite Radio , work

Satellite radio is such a remarkably simple concept that one might wonder why it took until 2001 for the first space-based audio service to make its debut in the United States.

At least it’s simple on the surface: Take a music, news or talk station, beam the signal up to a satellite, and overcome the limitations of ground-based transmitters whose signals generally drop off as distance increases. Then make sure the programming is more appealing than traditional radio stations and cut down on the number of commercials in exchange for a monthly subscription fee.

But as it turns out, satellite radio is a whole lot more complex than it seems on paper – and it took cutting-edge technology to make the systems operated by Sirius Satellite Radio and XM Satellite Radio work.

XM and Sirius are not the first companies to enter the satellite radio industry: Worldspace Corp., a firm based in Washington, has provided satellite radio in Asia and Africa since 1998. But Worldspace was intended primarily for use in fixed locations, while the systems used by XM and Sirius are optimized to reach U.S. listeners on the go.

From the ground up

It took a number of years to develop the XM and Sirius systems.

Engineers had to figure out how to squeeze dozens of individual channels into a relatively small amount of bandwidth and come up with reliable methods of beaming signals from thousands of miles in space to roving antennas smaller than tennis balls.

They also had to develop inexpensive circuitry, or chipsets, to enable receivers to decode the satellite signals, which are encrypted to prevent reception by non-subscribers. Both firms are working on newer versions of their chipsets that will be smaller and use less power.

Sirius and XM each took somewhat different approaches, although the end result, from a lay person’s perspective, is the same: 100 channels of music, news, sports and other fare available virtually anywhere in the continental United States. The companies are trying to distinguish themselves with programming and attitude.

XM’s system uses two very powerful satellites floating in space directly above the equator. The spacecraft are in geostationary orbit — they appear from the ground to remain in fixed perches, because they move around the Earth at the same speed the planet is rotating.

Geostationary satellites are commonly used for all sorts of space-based communications because they enable use of inexpensive, fixed antennas. Satellite TV and Internet systems are two examples of consumer-oriented technologies that use this type of satellite.

Repeat that, please

Since geostationary spacecraft are above the equator, terminals on the ground must have a decent view of the southern sky to receive signals from them. This posed a challenge for XM, since listeners in cars often pass by obstacles, such as buildings, foliage or hills, which can block geostationary satellite signals.

XM’s solution is a network of repeaters – antennas on buildings and other sites that receive satellite signals from an optimally placed antenna and retransmit them. The repeaters are located primarily in built-up areas, where loss of the satellite signal is most likely to occur.

Each XM receiver is equipped to receive signals from both of the company’s Boeing 702 satellites and a repeater simultaneously. As long as one of the sources is available, the radio will play without interruption. In addition, the receivers have buffers that store programming for several seconds, allowing operation to continue even if no signal is available momentarily.

Sirius uses a trio of Loral FS1300 satellites in unique elliptical orbits in an effort to avoid the problems posed by geostationary satellites.

The orbits, shaped like figure eights, allow the satellites to appear higher in the sky than XM’s, cutting down on the potential for a listener to be out of range of a satellite signal — and allowing Sirius to have a much smaller number of repeaters.

Sirius’ repeater network also avoids the need for specialized antennas that can track the company’s non-geostationary satellites as they move about the sky, Sirius feeds its repeaters using capacity on a geostationary satellite leased from a traditional satellite operator. Listeners can’t tell that the signals they receive via the repeaters do not travel over Sirius’ fleet of satellites.

The Sirius satellites each spend about 16 hours over the United States, then whip around the other side of the Earth and return eight hours later for another stint hovering over Sirius’ listening area, according to Ted Hessler, the company’s vice president of space segment and enterprise operations.

Two Sirius spacecraft cover the United States at any given time, Hessler said.

In the studio

XM and Sirius both operate digital broadcast centers that combine dozens of individual recording studios with huge amounts of storage to hold hundreds of thousands of compact discs worth of music in digital format.

Programmers just point and click at the material they want to play, and it airs directly from the storage system at the appointed time. During transmission, the system also adds a short description of the music or other material for display on a small receiver screen.

That is one unique advantage to satellite radio — you can find out the artist and song title as each piece of music plays.

The 22 terabytes of storage capacity at XM’s facilities in Washington can hold about 250,000 CDs, said Anthony J. Masiello, XM’s senior vice president of operations.

Terry Smith, senior vice president and chief technology officer of Sirius, said his company’s studios in mid-town Manhattan have about seven terabytes of storage. While that is less than XM has, Smith says it’s plenty.

“Our library is constantly being refreshed as new content comes in,” Smith said.

Both companies also maintain large collections of CDs to augment their digital libraries. They also retransmit programming that originates elsewhere, such as news, sports and comedy channels, and maintain studios where artists perform live.

Another, less visible key to satellite radio is digital compression, a technique to use radio spectrum as efficiently as possible. Both satellite radio broadcasters use sophisticated algorithms to squeeze as much material as they can into the available bandwidth without causing audio quality to degrade.

XM and Sirius are each allocated 12.5 megahertz of radio spectrum by the U.S. Federal Communications Commission.

Satellite radio for education

EDUSAT, according to the Indian Space Research Organization (ISRO), is the first exclusive satellite for serving the educational sector. It supports radio broadcasting, along with audio-video on C-band and Ku-band, and is built around the concept of digital interactive classrooms and a multimedia system.

The satellite has multiple regional beams covering different parts of India, which theoretically enables programmes to be broadcast in relevant local languages – India has 18 official languages and over 1500 dialects. “India will require 10,000 new schools each year and meeting the teaching needs on such a scale [by conventional methods] will be impossible,” Madhavan Nair, chairman of ISRO told New Scientist at the launch of the satellite.

EDUSAT can provide connectivity to schools, colleges and higher levels of education and also support non-formal education including developmental communication. The nation-wide beams are being harnessed by agencies like IGNOU, NCERT and the All India Council for Technical Education (AICTE), to reach hundreds of Receive Only Terminals (ROTs) and Satellite Interactive Terminals (SITs) located in schools and colleges, many in remote areas.

Content generation is the responsibility of user agencies, but it is a matter of concern that, over a year after the satellite was launched, much of its capacity is lying idle.

Satellite access for radio broadcasting is also available on other platforms like WorldSpace, which offers a ‘development channel’ to agencies like Equal Access for networking community FM channels (as in Nepal), or for directly broadcasting development and educational programmes for community listening on WorldSpace receivers.

The promise of radio
U.K. Open University’s notable success with educational radio has demonstrated how invaluable radio can be for weak students, who benefit from the medium as a supplementary learning tool. But the use of radio for distance education in India, as mentioned earlier, has had mixed results. AIR’s educational broadcasts are

All the same, it has been amply proved that radio – rightly used – can improve educational quality and relevance, lower educational costs and improve access to education, particularly for disadvantaged groups. It is most effective when supported by trained facilitators, group learning, group discussion, feedback and the use of multimedia approaches.

There is no single ideal format for educational radio. Innovative programming like those developed by Sesame Workshop in Africa, for instance, offer some very effective approaches to non-formal education over radio. Recently, AIR agreed to a proposal from Sesame Workshop India to provide airtime on national and regional radio channels for locally produced versions of the universally popular ‘Sesame Street’. The programmes would be aimed at pre-schoolers, and would also provide under-served children with access to educational media, especially in rural areas.

India spends just 3.4% of its GNP on education. Over 35% of the population is illiterate, and the drop out rate in schools is staggeringly high, with 40% of all school-going children dropping out during the primary stage itself. The percentage of dropouts goes up to 67% by Class X. The Supreme Court of India (in 1993) has declared education of children up to 14 years to be a fundamental right, but school attendance is related to the perceived importance of education by parents, and also to socio-economic factors.

Despite rapid developments in communication technologies in the last few decades, radio broadcasting remains the cheapest mode of mass communication in India, catering equally to the needs of the rich and the poor, rural and the urban masses and reaching the remotest parts of the country. In a country where the literacy rate is 65%, and fewer than 50% of homes are electrified, the humble transistor radio plays a vital role in the country’s socio-economic and cultural development.

Rural and deprived communities, with low literacy rates and little access to formal education, stand to benefit the most from distance learning through community radio. If and when such communities are permitted to set up their own low power radio stations – and 4000 such community radio stations are possible in India, according to government estimates – then we could witness a revolution in education far beyond anything dreamt of by the purveyors of digital technology in a digitally divided country.

Using radio for education and community development is part of the 75-year-old Reithian ambition for radio broadcasting. Children and youth can be easily and cheaply trained, and the goals of universal primary and secondary education for all can be reached more easily with broadcast support. Among the poor and marginalized people of the country, radio could even create a new class of people – educated but illiterate.