By Mitchell Round
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The principles RADAR was invented by Nikola
Tesla in 1917. But it wasn’t built until 1934.
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The same year it was used to detect an air raid.
It was good because of how fast it detected the
planes.
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But the British used it as a aircraft detection
fully first during WW2. They used it because
they believed the Germans were building
“death rays.”
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The war started research to find better
resolution, more portability and more features
for radar. The post-war years have seen the use
of radar in fields as diverse as air traffic
control, weather monitoring, and astrometry
and road speed control.
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RADAR is a detection system that uses
electromagnetic waves to identify the range,
altitude, direction, or speed of both moving
and fixed objects such as aircraft, ships, motor
vehicles, weather formations, and terrain. The
term RADAR was coined in 1941 as an
acronym for radio detection and ranging.
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The word RADAR is now apart of the English
Language and it has now lost it capitalisation.
It is the only word in the English language that
is both an acronym and a palindrome.
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A radar system has a transmitter that emits
microwaves or radio waves. These waves are in
phase when emitted, and when they come into
contact with an object are scattered in all
directions. The signal is thus partly reflected
back and it has a slight change of wavelength if
the target is moving.
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This enables radar to detect objects at ranges
where other emissions, such as sound or visible
light, would be too weak to detect.
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Radar absorbing material, containing resistive
and sometimes magnetic substances, is used on
military vehicles to reduce radar reflection.
This is the radio equivalent of painting
something a dark color.
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Radar waves scatter in a variety of ways
depending on the size of the radio wave and
the shape of the target. If the wavelength is
much shorter than the target's size, the wave
will bounce off in a way similar to the way
light is reflected by a mirror. If the wavelength
is much longer than the size of the target, the
target is polarized, like a dipole antenna.
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When the two length scales are comparable,
there may be resonances. Early radars used
very long wavelengths that were larger than
the targets and received a vague signal,
whereas some modern systems use shorter
wavelengths that can image objects as small as
a loaf of bread.
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Short radio waves reflect from curves and
corners, in a way similar to glint from a
rounded piece of glass. The most reflective
targets for short wavelengths have 90° angles
between the reflective surfaces.
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These corner reflectors are commonly used as
radar reflectors to make otherwise difficult-todetect objects easier to detect.
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Detection and Search RADAR
Targeting RADAR
Triggers
Weather sensing RADAR system
Navigational RADAR
Mapping RADAR
Road RADAR
RADAR for biological research
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Info From:
http://en.wikipedia.org/wiki/Radar
Pictures From:
http://images.google.com.au/imghp?hl=en&t
ab=wi
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By Mitchell Round