About Electromagnetic Pulse

Electromagnetic Pulse (EMP) is an instantaneous, intense energy field that can overload or disrupt at a

distance numerous electrical systems and high technology microcircuits, which are especially sensitive to power surges.  A large scale EMP effect can be produced by a single nuclear explosion detonated high in the atmosphere.  This method is referred to as High-Altitude EMP (HEMP).  A similar,smaller-scale EMP effect can be created using non-nuclear devices with powerful batteries or reactive chemicals.  This method is called High Power Microwave (HPM).  Several nations, including reported sponsors of terrorism, may currently have a capability to use EMP as a weapon for cyber warfare or cyber terrorism to disrupt communications and other parts of the U.S. critical infrastructure.  Also, some equipment and weapons used by the U.S. military may be vulnerable to the effects of EMP.

 The threat of an EMP attack against the United States is hard to assess, but some observers indicate that it is growing along with worldwide access to newer technologies and the proliferation of nuclear weapons.  In the past, the threat of mutually assured destruction provided a lasting deterrent against the exchange of multiple high-yield nuclear warheads.  However, now even a single, low-yield nuclear explosion high above the United States, or over a battlefield, can produce a large-scale EMP effect that could result in a widespread loss of electronics, but no direct fatalities, and may not necessarily evoke a large nuclear retaliatory strike by the U.S. military. This, coupled with published articles discussing the vulnerability of U.S. critical infrastructure control systems, and some U.S. military battlefield systems to the effects of EMP, may create a new incentive for other countries to rapidly develop or acquire a nuclear capability. Policy issues raised by this threat include (1) what is the United States doing to protect civilian critical infrastructure systems against the threat of EMP, (2) could the U.S. military be affected if an EMP attack is directed against the U.S. civilian infrastructure, (3) are other nations now encouraged by U.S. vulnerabilities to develop or acquire nuclear weapons, and (4) how likely are terrorist organizations to launch a smaller-scale EMP attack against the United States ?

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Radio, a potential medium for education

While admiring the growth of radio production and broadcast technology, Madhu Ranjan feels that it still continues to be an under-utilized technology in education. According to her, radio has enormous potential to improve distance education systems especially when integrated with other technologies such as television, mobile telephones, and the Internet.

Soon after its invention in the late 1890s, radio, due to its information and

entertainment value, vast reach, and immediacy, became the most popular means of mass communication around the world.

With the arrival of television, the birth of satellite broadcasting technology, and later the Internet, radio’s listener base began to erode and its importance diminished.  In the 1970s, however, radio (FM band) once again gained popularity, especially among young listeners.

Today, improved broadcasting quality, more innovative and entertaining content, and new technological developments in fields such as digital and satellite radio have made radio a resurgent medium, extremely popular in the fields of advertising and entertainment. Affordability, portability, and access indoors and outdoors give radio a clear edge over other media. Additionally, radio is increasingly becoming a more dynamic medium, as it is integrated into other new technologies such as television, mobile telephones, and the Internet.

This has opened up new opportunities for a variety of forms of delivery and access. For example, portable, low-cost FM transmitting stations have been developed and digital radio systems that transmit via satellite are being set up in many parts of the world. Internet streaming audio software technology now allows a global audience to listen to news from a distant country. In addition, the development of wind-up and solar radios utilizing inexpensive power sources allows radio to can cut across geographic, economic, and cultural boundaries.

However, radio still continues to be an under-utilized technology in education. This is somewhat surprising because, for a learner, radio is a simple, user friendly, accessible, and a well-established medium. From an educational provider’s point of view it is easy and inexpensive to set up, produce, and broadcast programs. Most nations currently have the engineering skills and broadcasting talent to apply this technology to education.

Today, many schools, colleges, universities, and other organizations use distance education systems. While developing a distance education system, factors such as cost effectiveness, efficiency, and the availability of appropriate communication technologies, as well as access and equity issues, particularly those related to gender, language, social status, and religion, are the most important considerations.

Other factors to consider relate to how distance learners can best use their higher order thinking skills and how they can cope with the limitations of time, age, gender, and language. Radio is able to address these issues while reaching a diverse group of learners and can be valuable in many different distance learning environments including schools, colleges and universities, businesses, and public sector organizations.

For distance education providers, radio is a cheaper alternative to other communication technology mediums. Producing interactive radio programs in distance education requires only low-priced equipment compared with other cutting-edge technologies. Educational institutions do not need to spend much money for establishing interactive radio studios in their organizations.

Learners are equally fortunate, because they do not have to buy or rent the costly and complex equipment required by TV and the Internet. There are no boundaries to broadcasting educational programs with interactive radio throughout the world and as long as learners have access to a very low-cost radio, they can listen to programs wherever they are; riding in their cars, traveling by bus or train, or working at home.

Moreover, interactive distance educational programs can be recorded for learners via inexpensive equipment, such as cassettes, CDs, or MP3 players. Educational radio helps provide equal access to knowledge for everyone by breaking digital walls around the world.

Interactive radio programs allow people with disabilities (with the exception of the hearing-impaired) to hear the voices of instructors, classmates, and experts, enhancing their ability to learn. While listening to interactive radio programs, learners have more time to construct knowledge.

Community radio is also an immensely powerful technology for the delivery of information with enormous global potential.  It is particularly powerful in providing access to information for marginalized populations, including women, minorities, and the poor, who often do not have access to more cutting edge technology. Radio can expand opportunities for the intended beneficiaries of development to participate in the in the development agenda, which can appropriately and adequately respond to their needs and aspirations.

Currently, the benefits of radio as a learning medium are overlooked. Conventional wisdom assumes that high-cost communication media ensure better interactive distance learning. Radio, however, when incorporated with interactive learning approaches, has enormous potential to improve distance education systems. In a very imaginatively designed program – funded by USAID and implemented by EDC – that makes the process of teaching-learning interesting and meaningful, radio lessons that introduce substantial interaction among students and teachers are improving classroom interaction in close to 300,000 government schools reaching over 25 million primary school students across several states in India.

Many interventions around the world are using radio innovatively; successfully enhancing the quality of teaching learning in traditional classroom settings, imparting health messages to communities; and providing useful information on agriculture to farmers.  Although it is not currently being exploited to its full potential, radio is a medium with tremendous potential, particularly for educational purposes.

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.