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Lesson#30
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RADIO – A BREAKTHROUGH IN MASS COMMUNICATION
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RADIO – A BREAKTHROUGH IN MASS COMMUNICATION
People around the world were benefiting from the newspapers as
one fine mean of mass
communication since the middle of 15th
century that in the last decade of the 19th
century scientists came
close to opening gates for an entirely different means of
communication which would require no paper and
printing press and transportation of the publication. It was a
mean to carry your voice to million others in a
flash of an eye. It was the invention of radio.
It was a miracle in the field of mass communication that a
person could address a very number of audiences
and that too, to a distance of thousands of kilometers away.
What is radio?
Radio is a technology that allows the transmission of signals by
modulation of electromagnetic
waves with frequencies below those of light.
Science of Radio waves
Radio waves are a form of electromagnetic radiation, and are
created whenever a charged object
accelerates with a frequency that lies in the radio frequency
(RF) portion of the electromagnetic spectrum.
This is the range from a few tens of hertz to a few giga hertz.
Electromagnetic radiation travels by means of
oscillating electric and magnetic fields that pass through the
air and the vacuum of space equally well, and
does not require a medium of transport.
By contrast, other types of electromagnetic radiation, with
frequencies above the RF range are gamma rays,
X-rays, and infrared, ultraviolet and visible light.
How the miracle came about?
The theoretical basis of the propagation of electromagnetic
waves was first described in 1873 by
James Clerk Maxwell in his paper to the Royal Society
A dynamical theory of the
electromagnetic field, which
followed his work between 1861 and 1865.
In 1878 David E. Hughes was the first to transmit and receive
radio waves when he noticed that his
induction balance caused noise in the receiver of his homemade
telephone. He demonstrated his discovery
to the Royal Society in 1880 but was told it was merely
induction.
It was Heinrich Rudolf Hertz who, between 1886 and 1888, first
validated Maxwell's theory through
experiment, demonstrating that radio radiation had all the
properties of waves. A great achievement indeed
it proved to be.
Marconi recognized as radio inventor
In 1896 Guglielmo Marconi was awarded what is sometimes
recognized as the world's first patent
for radio with British Patent 12039,
Improvements in transmitting electrical
impulses and signals and in apparatus therefor.
In 1897 he established the world's first Radio Station on the
Isle of Wight, England. The same year in
the USA, some key developments in radio's early history were
created and patented by Nikola Tesla. The
US Patent Office reversed its decision in 1904, awarding
Guglielmo Marconi a patent for the invention of
radio, possibly influenced by Marconi's financial backers in the
States, who included Thomas Edison and
Andrew Carnegie. Some believe this was done to allow the US
Government to avoid having to pay the
royalties that were being claimed by Nikola Tesla for use of his
patents.
In 1909 Marconi, with Karl Ferdinand Braun, was also awarded the
Nobel Prize in Physics for
"contributions to the development of wireless telegraphy".
Marconi opened the world's first "wireless"
factory in Hall Street, Chelmsford, England in 1898, employing
around 50 people. Around 1900, Tesla
opened the Wardenclyffe Tower facility and advertised services.
By 1903, the tower structure neared
completion. Various theories exist on how Tesla intended to
achieve the goals of this wireless system
(reportedly, a 200 kW system). Tesla claimed that Wardenclyffe,
as part of a World System of transmitters,
103
would have allowed secure multichannel transceiving of
information, universal navigation, time
synchronization, and a global location system.
Others work acknowledgement
In 1894 British physicist Sir Oliver Lodge demonstrated the
possibility of signaling using radio
waves using a detecting device called a
coherer,
a tube filled with iron filings which had been invented by
Temistocle Calzecchi-Onesti at Fermo in Italy in 1884. Edouard
Branly of France and Alexander Popov of
Russia later produced improved versions of the coherer. Popov,
who developed a practical communication
system based on the coherer, is often considered by his own
countrymen to have been the inventor of
radio.
On Christmas Eve, 1906, Reginald Fessenden (using his heterodyne
principle) transmitted the first radio
audio broadcast in history from Brant Rock, Massachusetts. Ships
at sea heard a broadcast that included
Fessenden playing the song
O Holy Night
on the violin and reading a passage from the
Bible. The world's
first radio news programme was broadcast August 31st 1920 by
station 8MK in Detroit, Michigan. The
world's first regular wireless broadcasts for entertainment
commenced in 1922 from the Marconi Research
Centre at Writtle near Chelmsford, England, which was also the
location of the world's first "wireless"
factory.
Early radios ran the entire power of the transmitter through a
carbon microphone. While some early radios
used some type of amplification through electric current or
battery, through the mid 1920s the most
common type of receiver was the Crystal set. In the 1920s,
amplifying vacuum tubes revolutionized both
radio receivers and radio transmitters.
Advancement on radio technology continues
• Aircraft used commercial
AM radio stations for navigation. This continued through the early 1960s
when VOR systems finally became widespread (though AM stations
are still marked on United
States aviation charts).
• In the early 1930s,
single sideband and frequency modulation were invented by amateur radio
operators. By the end of the decade, they were established
commercial modes.
• Radio was used to
transmit pictures visible as television as early as the 1920s. Standard analog
transmissions started in North America and Europe in the 1940s.
• In 1954, Regency
introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5V
Battery".
• In 1960, Sony introduced
their first transistorized radio, small enough to fit in a vest pocket, and
able to be powered by a small battery. It was durable, because
there were no tubes to burn out.
Over the next twenty years, transistors displaced tubes almost
completely except for very high
power, or very high frequency, uses.
• In 1963 color television
was commercially transmitted, and the first (radio) communication satellite,
TELSTAR, was launched.
• In the late 1960s, the
U.S. long-distance telephone network began to convert to a digital network,
employing digital radios for many of its links.
• In the 1970s, LORAN
became the premier radio navigation system. Soon, the U.S. Navy
experimented with satellite navigation, culminating in the
invention and launch of the GPS
constellation in 1987.
• In the early 1990s,
amateur radio experimenters began to use personal computers with audio cards
to process radio signals. In 1994, the U.S. Army and DARPA
launched an aggressive, successful
project to construct a software radio that could become a
different radio on the fly by changing
software.
• Digital transmissions
began to be applied to broadcasting in the late 1990s.
World grabs radio for a range of uses104
AM broadcast radio
sends music and voice in the Medium Frequency (MF -- 0.300 MHz to 3
MHz) radio spectrum. AM radio uses amplitude modulation, in
which louder sounds at the
microphone causes wider fluctuations in the transmitter power
while the transmitter frequency
remains unchanged. Transmissions are affected by static because
lightning and other sources of
radio add their radio waves to the ones from the transmitter.
FM broadcast radio
sends music and voice, with higher fidelity than AM radio. In frequency
modulation, louder sounds at the microphone cause the
transmitter frequency to fluctuate farther,
the transmitter power stays constant. FM is transmitted in the
Very High Frequency (VHF -- 30
MHz to 300 MHz) radio spectrum. FM requires more radio frequency
space than AM and there are
more frequencies available at higher frequencies, so there can
be more stations, each sending more
information. Another effect is that the shorter radio waves act
more like light, travelling in straight
lines that are not reflected back towards the Earth by the
ionosphere, resulting in a shorter effective
reception range.
Aviation voice radios
use VHF AM. AM is used so that multiple stations on the same channel can
be received. (Use of FM would result in stronger stations
blocking out reception of weaker stations
due to FM's capture effect). Aircraft are often so high that
their radios can see hundreds of miles,
even though they are using VHF.
Marine voice radios can
use AM in the shortwave High Frequency (HF -- 3 MHz to 30 MHz) radio
spectrum for very long ranges or narrowband FM in the VHF
spectrum for much shorter ranges.
TETRA, Terrestrial
Trunked Radio is a digital cell phone system for military, police and
ambulances.
Civil and military HF
(high frequency) voice services use shortwave radio to contact ships at sea,
aircraft and isolated settlements.
Government, police,
fire and commercial voice services use narrowband FM on special frequencies.
Fidelity is sacrificed to use a smaller range of radio
frequencies, usually five kilohertz of deviation (5
thousand cycles per second) for maximum pressure, rather than
the 75 used by FM broadcasts and
25 used by TV sound.
What to broadcast
Early radio stations faced the problem of target audience,
especially in a pluralistic society. The
economic growth in certain parts of the world also helped radio
stations to shape their program. So a part
of broadcast was meant to the specific nature of audience along
side news and entertainment. In Pakistan all
radio stations begin their transmission with recitation from
Quran due to specific nature of the audience.
Other societies with religious dominance do the same.
Distribution of time
For religious programs
News and views
Entertainment ... music, plays, children and women.
Education ... on health and common social life matters. |
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