Amateur radio

Amateur radio is a noncommercial radio service in which licensed operators communicate, experiment with radio technology, and provide public-service communications.

Radio spectrum: The range of electromagnetic frequencies used for radio communication and other technologies. Amateur operators share designated frequency bands within this broader resource.
Amateur radio emergency communications: The use of amateur radio operators and equipment to support communications during disasters and other emergencies. This public-service role becomes valuable when conventional communication networks fail.
Amateur radio licensing: A government authorization that permits an individual to transmit on designated amateur radio frequencies. Licenses establish operator privileges and the rules for transmitting.
Guglielmo Marconi: An Italian inventor and entrepreneur who developed practical wireless telegraphy systems in the late nineteenth and early twentieth centuries. His work helped make radio experimentation possible before amateur service was formally organized.
Citizens band radio: A personal radio service that allows short-range communication on designated channels without individual operator licenses in some countries. Unlike amateur radio, it generally offers fixed channels and less scope for technical experimentation.
Radio propagation: The behavior of radio waves as they travel through the atmosphere, space, and surrounding objects. Propagation conditions determine which distant stations an amateur signal can reach.
Amateur radio satellite: An artificial satellite that provides a transponder or other communication facility for amateur radio operators. Operators use these spacecraft to make contacts beyond ordinary terrestrial coverage.
Amateur radio call sign: An assigned identifier used to identify an amateur radio station during transmissions. Operators use call signs to identify stations and satisfy regulatory requirements.
Radio Act of 1912: A United States law that required radio stations to obtain licenses and assigned amateur stations wavelengths below 200 meters. It established licensing and pushed American amateurs toward shorter wavelengths.
Family Radio Service: A short-range, license-by-rule radio service in the United States using designated channels and certified equipment. Its equipment and operating privileges are more restricted than those of licensed amateurs.

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