subject: What is Radio? [print this page] What is Radio? What is Radio?
Radio th transmission f signals b modulation f electromagnetic waves wth frequencies below persons f visible set alight. Electromagnetic radiation travels b means f oscillating electromagnetic fields tht pass through th air n th vacuum f space. Information carried b systematically varying (modulating) m property f th radiated waves, such amplitude, frequency, phase, r pulse width. Whn radio waves pass n electrical conductor, th oscillating fields induce n alternating current n th conductor. Th n b detected n transformed nt sound r thr signals tht carry information.
Originally, radio r radiotelegraphy w called "wireless telegraphy", whh w shortened t "wireless" b th British. Th prefix radio- n th sense f wireless transmission, w first recorded n th word radioconductor, coined b th French physicist douard Branly n 1897 n based n th verb t radiate (n Latin "radius" means "spoke f a wheel, beam f set alight, ray"). Th word appears n a 1907 article b Lee De Forest, w adopted b th United States Navy n 1912 n became common b th time f th first commercial broadcasts n th United States n th 1920s. (Th noun "broadcasting" itself came frm n agricultural term, meaning "scattering seeds widely".) Th term w thn adopted b thr languages n Europe n Asia. British Commonwealth countries continued t mainly th term "wireless" until th mid 20th century, though th magazine f th BBC n th UK h bn called Radio Times r n t w first published n th early 1920s.
