Amateur radio is a popular technical hobby and volunteer public service that uses designated radio frequencies for the non-commercial exchange of messages, wireless experimentation, self-training, and emergency communications. RSGB Get Started in Amateur Radio

Amateur radio, also known as ham radio, is the use of radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communications. The term “amateur” is used to specify “a duly authorised person interested in radioelectric practice with a purely personal aim and without pecuniary interest;” Wikipedia Amateur Radio