In radio communication, used in
radio and
television broadcasting,
cell phones,
two-way radios,
wireless networking, and
satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by
modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In
radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In
radio navigation systems such as
GPS and
VOR, a mobile navigation instrument receives radio signals from
navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless
radio remote control devices like
drones,
garage door openers, and
keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device. (Full article...)
Mary Dudley (born Mary Elizabeth Goode; April 8, 1912 – March 17, 1964), known as Mary Dee, was an American disc jockey who is widely considered the first African-American woman disc jockey in the United States. She grew up in
Homestead, Pennsylvania, and then studied at
Howard University for two years. After having her family, she attended Si Mann School of Radio in
Pittsburgh, and on August 1, 1948, went on the air at
WHOD radio. Gaining national attention, Dee broadcast from a storefront, "Studio Dee", in the
Hill District of Pittsburgh from 1951 to 1956. She moved her show, Movin' Around with Mary Dee, to
Baltimore and broadcast from station
WSID from 1956 to 1958. In 1958, she moved to
Philadelphia and hosted Songs of Faith on
WHAT until her death in 1964.
Dee is considered a pioneer in developing the radio format that combines coverage of community affairs with music and news. She was one of the first two black women admitted to the
Association of American Women in Radio and Television, and was successful in campaigning for the organization to forgo meetings in
segregated facilities. During her lifetime she received numerous awards for her civic work. In 2011 she was honored posthumously with the Thomas J. MacWilliams Lifetime Achievement Award from the Media Association of Pittsburgh. (Full article...)
Image 5Animation of a
half-wave dipoleantenna radiating radio waves, showing the
electric field lines. The antenna in the center is two vertical metal rods connected to a
radio transmitter (not shown). The transmitter applies an
alternating electric current to the rods, which charges them alternately
positive (+) and
negative (−). Loops of electric field leave the antenna and travel away at the
speed of light; these are the radio waves. In this animation the action is shown slowed down tremendously. (from Radio wave)
Image 6Animated diagram of a
half-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver R. The
electric field (E, green arrows) of the incoming wave pushes the
electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). Since the length of the antenna is one half the
wavelength of the wave, the oscillating field induces
standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R). (from Radio wave)
Image 10Diagram of the
electric fields (E) and
magnetic fields (H) of radio waves emitted by a
monopole radio transmitting
antenna (small dark vertical line in the center). The E and H fields are perpendicular, as implied by the phase diagram in the lower right. (from Radio wave)
Image 11Heinrich Rudolf Hertz (1856–1894) proved the existence of electromagnetic radiation (from History of radio)
Image 12Reginald Fessenden (around 1906) (from History of radio)
Image 14In the 1920s, the
United States government publication, "Construction and Operation of a Simple Homemade Radio Receiving Outfit", showed how almost any person handy with simple tools could a build an effective
crystal radio receiver. (from History of radio)
Image 15Around 1920, radio broadcasting started to get popular. The
Brox Sisters, a popular singing group, gathered around the radio at the time. (from History of radio)
Image 16Advertisement placed on November 5, 1919, Nieuwe Rotterdamsche Courant announcing PCGG's debut broadcast scheduled for the next evening (from Radio broadcasting)
... that the relative rarity of the
radiodontTitanokorys(video featured) in
Marble Canyon suggests that the deposits in which it was found may represent the outermost edge of its distribution in life?
... that listeners to
ESPN's sports podcasts are "13 years younger than"
ESPN Radio listeners, according to a company executive?
RadioDecember 12, 2006 "...to create, expand, and maintain Wikipedia articles related to radio, including radio propagation and reception, radio programming, radio personalities, and the business of radio." (Example:
Mutual Broadcasting System)
Radio StationsFebruary 15, 2005 "...to coordinate the activities of creating and maintaining articles about radio stations." (Example: Pulse FM Kingborough & Huon)
PodcastingJanuary 21, 2007 "...to make Wikipedia's knowledge of notable Podcast and podcast-related information as complete as possible." (Example:
Podcast)
Amateur Radio(Inactive), August 24, 2006 "...to improve Wikipedia's articles related to Amateur radio, maintain the amateur radio category and its sub-categories for clean organization, and to produce and maintain templates for Amateur radio-related topic identification." (Example:
Amateur radio)
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