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| quikcafe.com | History of radio | Discovery and development | Wireless age | 20th century | Uses of radio | Audio | Data | Digital Radio |
Radio
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Radio is the wireless transmission of signals, by modulation of
electromagnetic waves with frequencies below those of light. Wireless is an old-fashioned term for a radio receiver, referring to its use as a wireless telegraph; now the term is used to describe modern wireless connections such as in cellular networks and wireless broadband Internet. Radio waves Radio waves are a form of electromagnetic radiation, created whenever a charged object (in normal radio transmission, an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to a few hundred gigahertz. |
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ELF - SLF - ULF/VF - VLF - LF/LW - MW - HF/SW - VHF - UHF - SHF -
EHF Electromagnetic radio spectrum Other types of electromagnetic radiation, with frequencies above the RF range are infrared, visible light, ultraviolet, X-rays and gamma rays. Since the energy of an individual photon of radio frequency is too low to remove an electron from an atom, radio waves are classified as non-ionizing radiation. Electromagnetic spectrum and diagram of radio transmission of an audio signal. Electromagnetic radiation travels (propagates) by means of oscillating electromagnetic fields that pass through the air and the vacuum of space equally well, and does not require a medium of transport (such as the aether). When radio waves pass an electrical conductor, the oscillating electric or magnetic field (depending on the shape of the conductor) induces an alternating current and voltage in the conductor. This can be transformed into audio or other signals that carry information. Although the word 'radio' is used to describe this phenomenon, the transmissions which we know as television, radio, radar, and cell phone are all classed as radio frequency emissions. |
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| quikcafe.com | History of radio | Discovery and development | Wireless age | 20th century | Uses of radio | Audio | Data | Digital Radio |