Shortwave radio is a range of radio frequencies used for international broadcasting, amateur radio, utility broadcasts such as time and weather, and other uses. The shortwave radio spectrum falls above the AM radio or "medium wave" band and below the CB radio (Citizens Band) frequencies.
The shortwave spectrum is divided into several radio bands, some of which are reserved for amateur radio use and some of which are reserved for radio broadcasts. As shortwave signals can travel over long distances, many of these broadcasts are intended for an international audience. Many shortwave stations switch frequencies several times a day, or broadcast on more than one frequency at once. This is because reception conditions are always changing depending on the frequency, the time of day, and other reasons, so shortwave stations will change their frequency several times a day to optimize their reception.
Starting in World War II, governments began using shortwave broadcasts as a means of getting their broadcasts to people in enemy territory. The United States government started the Voice of America, and the United Kingdom's BBC signals, over shortwave into the Axis countries. Later during the Cold War, Western shortwave stations such as the Voice of America would be an important source of news from the free world for those living behind the Iron Curtain. The Soviet Union countered this with their Radio Moscow which used high powered transmitters to broadcast communist propaganda around the world in many languages. Some countries including China, North Korea, and, during World War II, Germany and Japan, used jamming of shortwave radio signals in an attempt to prevent their citizens from listening.
Christian broadcasting on shortwave
There are many Christian radio stations using the shortwave bands. As shortwave radio is an effective method of reaching people in many third world countries in their own language, Christian ministries use shortwave to reach these people. Increasingly, many Christian shortwave radio stations in the United States are also intended for a domestic audience and broadcast in English. These range from WWCR, which sells airtime to a variety of Protestant ministries and conservative political programs; to WEWN, a Catholic station operated by the EWTN television network; to WYFR, the long-running station featuring the Calvinist ministry of Harold Camping.
WWV in Colorado and WWVH in Hawaii broadcast on 2500, 5000, 10,000, 15,000, and 20,000 kilohertz, providing time of day, solar conditions, and other related information. Other utility signals you may hear on shortwave include radio teletype and fax signals, airport and maritime weather forecasts, and finally spy broadcasts which are easily recognizable because they typically consist of a series of numbers being read in groups of four or five, usually in English or Spanish. The shortwave bands also used to be widely used for maritime communications by ships at sea, such as the international emergency frequency of 2182 kilohertz, but this has largely been replaced by the use of satellite communications.
- Passport to World Band Radio, 2007 edition. International Broadcasting Services Ltd. ISBN 0-914941-63-1.