Radar: A Silent Eye in the SkyDaniel Brosk Period TwoToday’s society relies heavily on an invention taken for granted: radar.
Just about everybody uses radar, whether they realize it or not. Tens ofthousands of lives rely on the precision and speed of radar to guide their planethrough the skies unscathed. Others just use it when they turn on the morningnews to check the weather forecast.While radar seems to be an important part of our everyday lives, it hasnot been around for long. It was not put into effect until 1935, near World WarII.
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The British and the Americans both worked on radar, but they did not worktogether to build a single system. They each developed their own systems at thesame time. In 1935, the first radar systems are installed in Great Britain,called the Early Warning Detection system. In 1940, Great Britain and theUnited States install radar aboard fighter planes, giving them an advantage inplane-to-plane combat as well as air-to-ground attacks.Radar works on a relatively simple theory. It’s one that everybody hasexperienced in their lifetime. Radar works much like an echo.
In an echo, asound is sent out in all directions. When the sound waves find an object, suchas a cliff face, they will bounce back to the source of the echo. If you countthe number of seconds from when the sound was made to when the sound was heard,you can figure out the distance the sound had to travel. The formula is:(S/2) X 1100 = D (Half of the total time times 1100 feetper second equals the distance from the origin to the reflection point)Of course, radar is a much more complicated system than just somebodyshouting and listening for the echo. In fact, modern radar listens not only foran echo, but where the echo comes from, what direction the object is moving, itsspeed, and its distance. There are two types of modern radar: continuous waveradar, and pulse radar.Pulse radar works like an echo. The transmitter sends out short burstsof radio waves.
It then shuts off, and the receiver listens for the echoes.Echoes from pulse radar can tell the distance and direction of the objectcreating the echo. This is the most common form of radar, and it is the onethat is used the most in airports around the world today.Continuous wave radar works on a different theory, the Doppler Theory.The Doppler Theory works on the principle that when a radio wave of a setfrequency hits a moving object, the frequency of the wave will change accordingto how the object is moving.
If the object is moving toward the Doppler radarstation, the object will reflect back a higher frequency wave, If it is movingaway, the frequency of the wave will be lower. From the change in frequency,the speed of the target can This is the type of radar that is used to trackstorms, and the type of radar used by policemen in radar guns.These are the basics of radar. But, there is a lot of machinery andcomputer technology involved in making an accurate picture of what is in the sky,on the sea, or on the road.
Most radar systems are a combination of sevencomponents (See Appendix A). Each component is a critical part of the radarsystem.The oscillator creates the actual electric waves. It then sends theradio waves to the modulator.The modulator is a part of the timing system of a radar system.
Themodulator turns on and off the transmitter, creating the pulse radar effect. Ittells the transmitter to send out a pulse, then wait for four milliseconds.The transmitter amplifies the low-power waves from the oscillator intohigh-power waves. These high-power waves usually last for one-millionth of asecond.The antenna broadcasts the radar signals and then listens for the echoes.
The duplexer is a device that permits the antenna to be both a sendingdevice, and a receiving device. It routes the signal from the transmitter tothe antenna, and then routes the echoes from the objects to the receiver.The receiver amplifies the weak signals reflected back to the antenna.It also filters out background noise that the antenna picks up, sending only thecorrect frequencies to the signal processor.
The signal processor takes the signals from the receivers, and removessignals from stationary objects, such as trees, skyscrapers, or mountains.Today, this is mostly done by computers.And last, but not least, we come to the display screen. For many years,this was a modified TV tube with an electroluminescent coating, which lights upwhen hit by electrons, and retained the glow for a few seconds. This is whatcreates the “blips” on the radar screen, that flash about every ten seconds,then fade. In newer systems, the signal processor and the display screen arecombined into a single computer.
With the power of today’s computers, thisinformation is transmitted around the world, to other airports, to thegovernment, and to TV stations, where weather broadcasts are made.Today, radar systems are standard around the country. The United Stateshas the most sophisticated radar system, both on the ground and in the sky.
Onthe ground, we track planes, weather, ships, and many Intercontinental BallisticMissiles. From space, we use satellites with radar to map the globe, spy onforeign countries, and track over the oceans. In each instance, radar plays akey role in our day-to-day lives.BibliographyHitzeroth, Deborah. Radar: The Silent Detector, 96 pp.
, ills., Lucent Books,1990. Page, Irving H. “RADAR,” The New Book of Popular Science, pgs. 246-253,Grolier Inc.