Amateur radio, also known as ham radio, is the use of the 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 authorized person interested in radioelectric practice with a purely personal aim and without pecuniary interest"; and to differentiate it from commercial broadcasting, public safety, or professional two-way radio services.
An example of an amateur radio station with four transceivers, amplifiers, and a computer for logging and for digital modes. On the wall are examples of various amateur radio awards, certificates, and reception report cards (QSL cards) from foreign amateur stations.
Polish amateur radio station SP1QE, featuring 1930s vacuum tube transmitter and receiver.
An amateur radio station in Wales. Multiple transceivers are employed for different bands and modes. Computers are used for control, data modes, SDR, RTTY and logging.
A young Polish woman with radio antennas in Åland
Wireless communication is the transfer of information (telecommunication) between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most common wireless technologies use radio waves. With radio waves, intended distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications involve other electromagnetic phenomena, such as light and magnetic or electric fields, or the use of sound.
A handheld on-board communication station of the maritime mobile service
Bell and Tainter's photophone, of 1880.
Marconi transmitting the first radio signal across the Atlantic.
Power MOSFETs, which are used in RF power amplifiers to boost radio frequency (RF) signals in long-distance wireless networks.