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. Get payday loan to make a payment.

Interactive radio for education

Interactive Radio Instruction (IRI) is an instructional tool designed to deliver active learning by radio. It delivers daily 30-minute radio broadcasts that promote active learning and are designed to improve educational quality and teaching practices in schools and to deliver a complete basic education to learners not in school.

Image credits: EDC / Cover page of the report
Data gathered between 1975 and 2000 demonstrated that Interactive Radio Instruction (IRI) had improved learning outcomes in conventional classrooms by between 10% and 20% when compared with control classrooms not using IRI.

IRI is an effective delivery mechanism for in-service professional development, as teachers are able to actively employ improved instructional techniques in the classroom while undergoing radio-based training. Teachers not only demonstrated a better understanding of pedagogical concepts emphasised by broadcasts, but more frequently utilised active learning and student-centered techniques in lessons independent of radio guidance.

The manual looks into the aspects of learning outcomes by subject, on the impact of IRI on pre-primary and early childhood learning outcomes, radio-based in-service professional development for primary school teachers.

The document has been broadly organised in the following sections:

- Student learning outcomes by subject area

- Student learning outcomes in early childhood education

- Teacher professional development observation outcomes

- Student learning outcomes with marginalised populations

Citing examples from various countries the manual highlights the impact of IRI on the learning outcomes of four key marginalised groups: girls, orphans and vulnerable children, learners in fragile states, and those in rural areas.

A review of the learning outcomes of various countries brought to light some of the successful, and not-so-successful, IRI experiences. Key findings of the research revealed that without adequate information on student attendance, quality of teacher training and consistency of teacher attendance, it was impossible to draw definitive conclusions regarding the marginal impact of IRI on student learning.Students not only can create NFL, MLB, NBA & NCAA emblems but any of their favorite team easily.

How have radio and TV broadcasting been used in education?

Radio and television have been used widely as educational tools since the 1920s and the 1950s, respectively. There are three general approaches to the use of radio and TV broadcasting in education:

1. direct class teaching, where broadcast programming substitutes for teachers on a temporary basis;
2. school broadcasting, where broadcast programming provides complementary teaching and learning resources not otherwise available
3. general educational programming over community, national and international stations which provide general and informal educational opportunities

The most notable and best documented example of the direct class teaching approach is Interactive Radio Instruction (IRI).This consists of “ready-made 20-30 minute direct teaching and learning exercises to the classroom on a daily basis. The radio lessons, developed around specific learning objectives at particular levels of maths, science, health and languages in national curricula, are intended to improve the quality of classroom teaching and to act as a regular, structured aid to poorly trained classroom teachers in under-resourced schools.” IRI projects have been implemented in Latin America and Africa. In Asia, IRI was first implemented in Thailand in 1980; Indonesia, Pakistan, Bangladesh and Nepal rolled out their own IRI projects in the 1990s. What differentiates IRI from most other distance education programs is that its primary objective is to raise the quality of learning – and not merely to expand educational access – and it has had much success in both formal and non-formal settings. Extensive research around the world has shown that many IRI projects have had a positive impact on learning outcomes and on educational equity. And with its economies of scale, it has proven to be a cost-effective strategy relative to other interventions.

Mexico’s Telesecundaria is another notable example of direct class teaching, this time using broadcast television. The programme was launched in Mexico in 1968 as a cost-effective strategy for expanding lower secondary schooling in small and remote communities.Perraton describes the programme thus:

Centrally produced television programs are beamed via satellite throughout the country on a scheduled basis (8 am to 2 pm and 2 pm to 8 pm) to Telesecundaria schools, covering the same secondary curriculum as that offered in ordinary schools. Each hour focuses on a different subject area and typically follows the same routine – 15 minutes of television, then book-led and teacher-led activities. Students are exposed to a variety of teachers on television but have one home teacher at the school for all disciplines in each grade.

The design of the programme has undergone many changes through the years, shifting from a “talking heads” approach to more interactive and dynamic programming that “link[s] the community to the programme around the teaching method. The strategy meant combining community issues into the programs, offering children an integrated education, involving the community at large in the organization and management of the school and stimulating students to carry out community activities.” Assessments of Telesecundaria have been encouraging: drop out rates are slightly better than those of general secondary schools and significantly better than in technical schools. In Asia, the 44 radio and TV universities in China (including the China Central Radio and Television University), Universitas Terbuka in Indonesia, and Indira Ghandi National Open University have made extensive use of radio and television, both for direct class teaching and for school broadcasting, to reach more of their respective large populations. For these institutions, broadcasts are often accompanied by printed materials and audio cassettes.

Japan’s University of the Air was broadcasting 160 television and 160 radio courses in 2000. Each course consists of 15 45-minute lectures broadcast nationwide once a week for 15 weeks. Courses are aired over University-owned stations from 6 am to 12 noon. Students are also given supplemental print materials, face-to-face instruction, and online tutorials.

Often deployed with print materials, cassettes and CD-ROMS, school broadcasting, like direct class teaching, is geared to national curricula and developed for a range of subject areas. But unlike direct class instruction, school broadcasting is not intended to substitute for the teacher but merely as an enrichment of traditional classroom instruction. School broadcasting is more flexible than IRI since teachers decide how they will integrate the broadcast materials into their classes. Large broadcasting corporations that provide school broadcasts include the British Broadcasting Corporation Education Radio TV in the United Kingdom and the NHK Japanese Broadcasting Station. In developing countries, school broadcasts are often a result of a partnership between the Ministry of Education and the Ministry of Information.

General educational programming consists of a broad range of programme types – news programs, documentary programs, quiz shows, educational cartoons, etc. – that afford non-formal educational opportunities for all types of learners. In a sense, any radio or TV programming with informational and educational value can be considered under this type. Some notable examples that have a global reach are the United States-based television show Sesame Street, the all-information television channels National Geographic and Discovery, and the radio programme Voice of America.The Farm Radio Forum, which began in Canada in the 1940s and which has since served as a model for radio discussion programs worldwide, is another example of non-formal educational programming. It shows that you can also learn from lecturers with or without ID lanyards that represents certain University or college.

Radio

In the 1930s and 1940s, when radio still was regarded as a new medium, special children’s programs were broadcast in order to attract young listeners. As such programs became popular, production increased. Children and teenagers took pleasure in listening to programs specifically aimed at children as well as other programs. By this time, American children aged nine to twelve listened to radio approximately two to three hours a day, especially during the evening. Girls preferred romantic and historical dramatizations and boys listened more to popular and novelty programs, but one study came to the conclusion that the differences mattered less than the similarities. With some variations, comedy and mystery radio plays were preferred above others by both boys and girls of all ages. Thus children enjoyed a variety of programs, including those produced for adults.

As with other electronic media, radio was met with worries from the adult world. In Sweden, as in other countries, it was a common anxiety that too much listening could make children passive and less eager to play. In the 1940s, Swedish teachers expressed worries about being regarded as mere “loudspeakers” by children accustomed to passively listening to radio. However, compared with reactions to other electronic media, radio seems to have incited relatively few “moral panic” attacks. Partly this can be explained by radio’s supposed usefulness in education (discussed below).

In the 1950s, when TELEVISION was introduced, researchers in Britain came to the conclusion that television reduced radio listening more than it reduced any other activity. In spite of this, one in three children said that if they had to do without radio they would miss it quite a lot. The study also noticed that children who had been watching television for several years listened a little more often to the radio. This was described as a revival in line with reports of adults’ media behavior. While radio plays could not compete with television plays, other types of programs held listeners’ interest, including panel games, discussions, music, and sports commentaries.

Other studies have arrived at the similar conclusion that, with increasing age, children spent more time with radio than with television. TEENAGERS in particular have been found to be regular radio listeners. Researchers have attributed this to the socialization effects of radio, although explanations of what those effects are have varied over time. In the 1970s socialization to political virtues was considered to be an important factor, while in the 1980s, radio was seen as a source for identity formation in a peer group. This change can be related to the shift of content in programs addressed to teenagers. In the 1980s and 1990s teenagers listened more to music than to anything else on radio.