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Winter/Spring 2010 Vol. 10 Number 1

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Calling All Frequencies

Cell phones, wireless Internet devices, even garage-door openers, all emit radio signals when used. ©Ryan Burke/iStockphotoAs new technologies are developed, the radio spectrum -- a finite resource -- is allocated to more users. The proliferation of these technologies is a boon to industry and consumers. But the explosion of radio signals flying through the air is having some unintended effects on areas of scientific research that monitor radio emissions from natural sources, such as hurricanes or distant galaxies. Interference from "active" users -- technologies emitting a radio signal -- can drown out the natural emissions monitored by scientists. A new report from the National Research Council examines usage of the radio spectrum and how it can be managed to balance the needs of all users.

All matter emits signals at a characteristic frequency that depends on its temperature. Cold gases, the dust between stars, and materials on Earth (e.g., water, soil, atmospheric gases) tend to emit signals in the radio portion of the electromagnetic spectrum, which lies well below the visible range. For decades, scientists have been monitoring natural radio emissions to learn about Earth's atmosphere and climate as well as aid in our understanding of the universe.

The radio spectrum, however, is limited. Interference with natural emissions can occur when active users transmit at frequencies inside or outside their assigned band -- usually inadvertently -- causing background noise in quiet bands protected for scientific use. In the U.S., the radio spectrum is regulated by the National Telecommunications and Information Agency (NTIA) for federal government users and by the Federal Communications Commission (FCC) for all others. Users are assigned specific frequency bands and given maximum allowable power levels for their emissions. The interference problem is a one-way street, though; "passive" users of the radio spectrum -- researchers who are only monitoring and not emitting signals -- cannot interfere with other users.

Both active and passive use of the radio spectrum is increasing. The elevating tension between competing needs suggests that the procedures currently in place for regulating spectrum use, which were developed prior to 1950, should be updated. According to the National Research Council report, the White House Office of Science and Technology Policy should create a permanent advisory body to identify ways to improve spectrum sharing among all users. The report also recommends that the FCC and NTIA ensure that scientific access to spectrum is preserved in the development of future spectrum policy. --  Rebecca Alvania

Spectrum Management for Science in the 21st Century. Committee on Scientific Use of the Radio Spectrum, Standing Committee on Radio Frequencies, Board on Physics and Astronomy, Division on Engineering and Physical Sciences (2010, 248 pp.; ISBN 0-309-14686-0; available from the National Academies Press, tel. 1-800-624-6242; $52.75 plus $5.00 shipping for single copies).

The committee was co-chaired by Marshall Cohen, professor emeritus, California Institute of Technology, Pasadena, and Albin Gasiewski, professor of electrical and computer engineering, University of Colorado, Boulder. The study was funded by the National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, and the National Science Foundation.

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Copyright 2010 by the National Academy of Sciences