In most countries of the world, people can obtain government-issued licenses to send and receive messages by radio for nonprofessional purposes. In America, this hobby is called amateur radio or ham radio. If you want only to listen to communications and broadcasting, and not to transmit signals, you do not need a license in the United States (although you do need one in some countries).
Who Uses Amateur Radio?
Anyone can use ham radio, provided they can pass the tests necessary to obtain a license. Amateur radio operators (or hams) can communicate in numerous modes, including voice, Morse code, television, and various forms of text messaging. Text messaging can be done in real time, or by posting messages similar to electronic mail (e-mail). Radio amateurs have set up their own radio networks. Some of these networks have Internet gateways. This mode is known as packet radio.
Some radio hams chat about anything they can think of (except business matters, which are illegal to discuss via ham radio). Others like to practice emergency communications skills, so they can be of public service during crises such as hurricanes, earthquakes, or floods. Still others like to go out into the wilderness and talk to people far away while sitting out under the stars and using battery power. Amateur radio operators communicate from cars, boats, aircraft, and bicycles; this is called mobile operation. When transceivers are used while walking or hiking, it is known as portable or handheld operation.
Amateur Equipment and Licensing
A computer-controlled amateur radio station
A simple ham radio station has a transceiver (transmitter/receiver), a microphone, and an antenna. A small station can fit on a desktop, and is about the size of a home computer or hi-fi stereo system. Accessories can be added until a ham “rig” is a large installation, comparable to a small commercial broadcast station.
Above figure shows an example of a fixed, computer-controlled amateur radio station. The computer can be used to control the functions of the transceivers, and also to communicate using digital modes with other hams who own computers. The station can be equipped to interface with the telephone services, also called landline. The computer can control the antennas for the station, and can keep a log of all stations that have been contacted.
The best way to learn about ham radio in the United States is to contact the headquarters of the American Radio Relay League (ARRL), 225 Main Street, Newington, CT 06111. They maintain a Web site at www.arrl.org. If you live outside the United States, the ARRL can direct you to an organization in your home country that can help you obtain a license and get on the air.
The high-frequency (HF) portion of the radio spectrum, at frequencies between 3 and 30 MHz, is sometimes called the shortwave band. This is a misnomer by contemporary standards; the waves are long compared with ultrahigh frequencies (UHF), microwaves, and IR, which are commonly used in wireless devices. In free space, a frequency of 3 MHz corresponds to a wavelength of 100 m; 30 MHz corresponds to 10 m. In the early years of radio when the shortwave band got its name, the wavelengths between 3 and 30 MHz were short compared with the wavelengths of most broadcast and communications signals, which had wavelengths in the kilometer range.
Anyone can build or obtain a shortwave or general-coverage radio receiver, install a modest outdoor antenna, and listen to signals from all around the world. This hobby is called shortwave listening or SWLing. In the United States, the proliferation of computers and online communications has, to some extent, overshadowed SWLing, and many young people grow up today ignorant of a realm of broadcasting and communications that still predominates in much of the world. But some people are still fascinated by the fact that people can contact each other using wireless devices alone, without the need for any human-made infrastructure other than an antenna at the source and another antenna at the destination. The ionosphere returns shortwave signals to the earth’s surface, and allows reliable global broadcasting and communication to take place today, just as it has since the early 1900s.
Various commercially manufactured shortwave receivers are available. Most electronics stores carry one or more models, along with antenna equipment, for a complete installation. Amateur radio conventions, called “hamfests,” can be a good source of shortwave receiving equipment at bargain prices. For information about events of this sort in your area, you can contact the American Radio Relay League at www.arrl.org, or pay a visit to your local amateur radio club.