Word: echoeing
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...simplest terms, a radar set shoots radio energy at a target, catches the reflected echo, times the round trip, divides by two, and. since the speed of the radio wave is known, translates all the information into a "blip" of light on a fluorescent (television) screen showing the target's distance and position...
...practice radar is not that simple. A conventional transmitter, sending continuous radar waves, would not do, for the same reason that a man roaring incessantly at a cliff would get back only a confusing noise. To get a clear, time-able echo, he must utter a short, sharp shout. That is exactly what radar does. It sends staccato "pulses" of electric energy, each less than a millionth of a second in length, at a rate of about 1,000 a second. Each pulse has time to make a round trip (about a thousandth of a second for a target...
...problem in radar is to generate enough power to get a detectable echo from a distant point. Of the total energy sent out in a radar beam scanning the skies, only a tiny fraction hits the target (e.g., a plane), and a much tinier echo gets back to the receiver. Engineers estimate that if the outgoing energy were represented by the sands of a beach, the returning echo would be just one grain of sand...
Radiation Laboratory and Bell Laboratories proceeded to develop an uncharted part of the radio spectrum-microwaves. For radar, the relatively long radio waves (one and a half meters) used early in the war had serious shortcomings: 1) they gave only a crude, distorted echo; 2) they had some blind spots, especially close to the ground; 3) they required huge "bedspring" antennae. Microwaves solved all these problems at one stroke. These tiny waves, which are measured in centimeters, can be formed into a beam precise enough to detect the periscope of a submerged submarine...
...bowl-shaped antenna which beams the outgoing radio pulses, catches the echo...