Short-Wave Transmitters




Short-Wave Transmitters

Short-wave radio transmission and reception occurs in the range somewhere between 2 and 30 MHz (megahertz, or million cycles per second). Because these signals are capable of propagating over a greater distance than either AM or FM radio, shortwave is the preferred medium for radio broadcasting to remote locations. World powers in the twentieth century and beyond made use of short-wave radio transmissions to bridge political and physical barriers in sending propaganda messages to distant populations.

Despite their name, shortwaves are relatively long in wavelength compared to most of the electromagnetic spectrum. They measure anywhere from 33 to 262 feet (10–80 m), gargantuan in comparison to ultra high-energy waves such as x rays and gamma rays, of which it would take many millions to cover even the length of a millimeter. On the electromagnetic spectrum, the higher the energy level, the higher the frequency, and the shorter the wavelength.

Shortwaves shorter than AM (amplitude modulation) radio waves, to which the U.S. Federal Communications Commission has assigned the frequency range of 535 kHz to 1.7 MHz. Short-wave transmissions occur somewhere between 2 to 5.9 MHz at the low end, and 26.1 to 30 MHz at the high end. Above these are microwave regions assigned to television stations, as well as FM, which occupies the range from 88 to 108 MHz. Like AM signals, those of short-wave radio transmissions propagate over a great distance because they bounce off of a heavily charged layer in the earth's ionosphere.

The length of signal propagation prompted the establishment of international short-wave communications in the late 1930s. During the Cold War, the world's major powers used shortwave to transmit propaganda messages. Examples of these efforts included the short-wave stations operated by Voice of America, Radio Moscow, Radio Beijing, and the British Broadcasting Corporation.

Long before the 2003 invasion of Iraq, the United States, through its Central Intelligence Agency, supported Iraqi short-wave stations operated by resistance movements. In June 1996, President William J. Clinton provided $6 million to the Iraqi National Accord, which set up several stations, including Twin Rivers Radio, Radio Tikrit, and al Mustaqbal. The latter, whose name means "The Future," broadcast from Kuwait and from U.S. military EC-130 psychological operations planes, on the frequency of 1575.3 kHz (1.5753 MHz), which in the United States would be a high-frequency AM station.

█ FURTHER READING:

BOOKS:

Helms, Harry L. Shortwave Listening Guidebook: The Complete Guide to Hearing the World. Solana Beach, CA: High Text Publications, 1993.

McCormick, Anita Louise. Shortwave Radio Listening for Beginners. Blue Ridge Summit, PA: TAB Books, 1993.

Yoder, Andrew R., and Hank Bennett. The Complete Shortwave Listener's Handbook. New York: McGraw-Hill, 1997.

ELECTRONIC:

Clandestine Radio.com. < http://www.clandestineradio.com > (April 2, 2003).

SEE ALSO

CIA, Foreign Broadcast Information Service
Electromagnetic Spectrum
National Telecommunications Information Administration, and Security for the Radio Frequency Spectrum, United States
Propaganda, Uses and Psychology




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