Radar: A Silent Eye in the Sky Daniel Brook Period Two Today’s society relies heavily on an invention taken for granted: radar. Just about everybody uses radar, whether they realize it or not. Tens of thousands of lives rely on the precision and speed of radar to guide their plane through the skies unscathed. Others just use it when they turn on the morning news to check the weather forecast. While radar seems to be an important part of our everyday lives, it has not been around for long. It was not put into effect until 1935, near World War II.
The British and the Americans both worked on radar, but they did not work together to build a single system. They each developed their own systems at the same time. In 1935, the first radar systems are installed in Great Britain, called the Early Warning Detection system. In 1940, Great Britain and the United States install radar aboard fighter planes, giving them an advantage in plane-to-plane combat as well as air-to-ground attacks. Radar works on a relatively simple theory. It’s one that everybody has experienced in their lifetime.
Radar works much like an echo. In an echo, a sound is sent out in all directions. When the sound waves find an object, such as a cliff face, they will bounce back to the source of the echo. If you count the 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 feet per second equals the distance from the origin to the reflection point) Of course, radar is a much more complicated system than just somebody shouting and listening for the echo. In fact, modern radar listens not only for an echo, but where the echo comes from, what direction the object is moving, its speed, and its distance.
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There are two types of modern radar: continuous wave radar, and pulse radar. pulse radar works like an echo. The transmitter sends out short bursts of 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 object creating the echo.
This is the most common form of radar, and it is the one that 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 set frequency hits a moving object, the frequency of the wave will change according to how the object is moving. If the object is moving toward the Doppler radar station, the object will reflect back a higher frequency wave, If it is moving away, 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 track storms, and the type of radar used by policemen in radar guns. These are the basics of radar.
But, there is a lot of machinery and computer 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 seven components (See Appendix A).
Each component is a critical part of the radar system. The oscillator creates the actual electric waves.
It then sends the radio waves to the modulator. The modulator is a part of the timing system of a radar system. The modulator turns on and off the transmitter, creating the pulse radar effect. It tells the transmitter to send out a pulse, then wait for four milliseconds. The transmitter amplifies the low-power waves from the oscillator into high-power waves.
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These high-power waves usually last for one-millionth of a second. The antenna broadcasts the radar signals and then listens for the echoes. The duplex er is a device that permits the antenna to be both a sending device, and a receiving device. It routes the signal from the transmitter to the 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 the correct frequencies to the signal processor. The signal processor takes the signals from the receivers, and removes signals 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 up when hit by electrons, and retained the glow for a few seconds.
This is what creates the ‘blips’ on the radar screen, that flash about every ten seconds, then fade. In newer systems, the signal processor and the display screen a recombined into a single computer. With the power of today’s computers, this information is transmitted around the world, to other airports, to the government, and to TV stations, where weather broadcasts are made. Today, radar systems are standard around the country.
The United States has the most sophisticated radar system, both on the ground and in the sky. Onthe ground, we track planes, weather, ships, and many Intercontinental Ballistic Missiles. From space, we use satellites with radar to map the globe, spy on foreign countries, and track over the oceans. In each instance, radar plays a key role in our day-to-day lives.
Bibliography Hit zeroth, Deborah. Radar: The Silent Detector, 96 pp. , ills. , Lucent Books, 1990. Page, Irving H. ‘RADAR,’ The New Book of Popular Science, pigs.
246-253, Grolier Inc. 1994.
