|
Radio
broadcasting is an audio (sound)
broadcasting service, traditionally
broadcast through the air as radio waves (a
form of electromagnetic radiation) from a
transmitter to an antenna and a thus to a
receiving device. Stations can be linked in
radio networks to broadcast common
programming, either in syndication or
simulcast or both. Audio broadcasting also
can be done via cable FM, local wire
networks, satellite and the Internet.
Radio
Originally,
radio or radioteleography was called
'wireless telegraphy', which was shortened
to 'wireless'. The prefix radio- in the
sense of wireless transmission was first
recorded in the word radioconductor, coined
by the French physicist Edouard Branly in
1897 and based on the verb to radiate (in
Latin "radius" means "spoke of a wheel, beam
of light, ray"). 'Radio' as a noun is said
to have been coined by advertising expert
Waldo Warren (White 1944). The word appears
in a 1907 article by Lee de Forest, was
adopted by the United States Navy in 1912
and became common by the time of the first
commercial broadcasts in the United States
in the 1920s. (The noun 'broadcasting'
itself came from an agricultural term,
meaning 'scattering seeds'.) The term was
then adopted by other languages in Europe
and Asia, although British Commonwealth
countries retained the term 'wireless' until
the mid-20th century. In Japanese, the term
'wireless' is the basis for the term 'radio
wave' although the term for the device that
listens to radio waves is literally 'device
for receiving sounds'.
In recent years the term 'wireless' has
gained renewed popularity through the rapid
growth of short range networking, e.g., WLAN
('Wireless Local Area Network'), WiFi and
Bluetooth as well as mobile telephony, e.g.,
GSM and UMTS. Today, the term 'radio' often
refers to the actual transceiver device or
chip, whereas 'wireless' refers to the
system and/or method used for radio
communication. Hence one talks about radio
transceivers and Radio Frequency
Identification (RFID), but about wireless
devices and wireless sensor networks.
History of radio
Although invention was long attributed to
Guglielmo Marconi, the identity of the
original inventor of radio, at the time
called wireless telegraphy, is contentious.
Development from a laboratory demonstration
to commercial utility spanned several
decades and required the efforts of many
practitioners. The controversy over who
invented the radio, with the benefit of
hindsight, can be broken down as follows:
-
In 1887,
David E. Hughes transmitted Morse code
by radio at and below the Super low
frequency range (via a clockwork
transmitter).
-
In 1888,
Heinrich Hertz produced and measured the
Ultra High Frequency range (via a
sparkgap transmitter).
-
In 1891,
Nikola Tesla began wireless research. He
developed means to reliably produce
radio frequencies, publicly demonstrated
the principles of radio, and transmitted
long-distance signals.
-
Between 1893
and 1894, Roberto Landell de Moura, a
Brazilian priest and scientist,
conducted experiments. He did not
publicise his achievement until 1900 but
later obtained Brazilian patent.
-
In 1894 in
Kolkata (Calcutta), Sir Jagdish Chandra
Bose (J. C. Bose) invented the mercury
coherer, together with the telephone
receiver.
-
Alexander
Stepanovich Popov, in 1894, built his
first radio receiver, which contained a
coherer but actually coherer was first
demonstrated by J.C. Bose. Popov
demonstrated the coherer, further
refined as a lightning detector, to the
Russian Physical and Chemical Society on
May 7, 1895.
-
In 1894,
Guglielmo Marconi read about Hertz's and
Tesla's work on wireless telegraphy, and
began his own experiments.
-
In December
of 1901 Guglielmo Marconi used J.C.
Bose's inventions to receive the radio
signal in his first transatlantic radio
communication over a distance of 2000
miles from Poldhu, UK, to St. Johns,
Newfoundland. Marconi was celebrated
worldwide for this achievement. Soon
after the patent was given to Marconi.
He even received the Nobel Prize.
-
In early
1900s Reginald Fessenden and Lee de
Forest invented amplitude-modulated (AM)
radio) allowing an audio signal to be
sent over the air.
-
In 1935
Edwin H. Armstrong invented
frequency-modulated (FM) radio, so that
an audio signal can avoid "static," that
is, interference from electrical
equipment and atmospherics.
In 1943, the
U.S. Supreme Court acknowledged that
Marconi's work wasn't original, and the
patent ownership is given back to Nikola
Tesla. However, Tesla died shortly before
the decision was announced
From
Wikipedia. |
Page Menu