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Shortwave Radio Facts

Shortwave radio works in much the same way as FM and AM radio, except that you can hear shortwave broadcasts from hundreds and even thousands of miles away from the broadcasting source. Reception of these broadcasts requires a special radio, and gives listeners a peek into the news, culture and music of the people where these broadcasts originate.

Definition
- Shortwave radio broadcasts are found between the 3- and 30-MHz frequency bands that allow signals to travel long distances. Broadcasters often use these frequencies to transmit internationally. Some examples of shortwave broadcasters include the BBC, Germany's Deutsche Welle, the Voice of America, Radio Japan and Radio Canada International. What programming is available depends on the time of day and the availability of propagation to a specific locale.
Propagation
- Shortwave radio signals propagate in a different way than standard FM and AM broadcasts -- although AM broadcasts in the right conditions can propagate in a similar fashion, just not as far. While most FM and AM transmissions are "line of sight" -- meaning broadcasts travel across the Earth's surface -- shortwave signals bounce off a layer of the atmosphere known as the ionosphere, located 50 or so miles above the Earth's surface. Radio signals bounce off this atmospheric layer and get directed back towards the Earth's surface.
Frequencies
- You can find commercial shortwave broadcasts on select parts of the higher frequency bands. Look for stations in between the following frequencies: 2.300 to 2.495 MHz, 3.200 to 3.400 MHz, 3.850 to 4.000 MHz, 4.750 to 5.060 MHz, 5.900 to 6.200 MHz, 7.100 MHz to 7.350 MHz, 9.400 to 9.990 MHz, 11.600 to 12.100 MHz, 13.500 to 13.870 MHz, 15.100 to 15.800 MHz, 17.480 to 17.900 MHz, 21.450 to 21.750 MHz and 25.600 to 26.100 MHz. Official United States time broadcasts are found on 2.5, 5, 10, 15 and 20 MHz.
Reception
- Shortwave broadcast reception is often better at nighttime than during the day. This is because sunlight charges the particles in the ionosphere, causing radio waves to be more readily absorbed by the ionosphere during daylight hours. When darkness falls, the ionosphere loses its charge and bends radio waves back to the Earth more frequently. Lower levels of the ionosphere also dissipate at night, meaning radio waves travel farther into the ionosphere before being reflected back to Earth.

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