Radar in the Modern World

Scott Martin

D. Hyland

English 192

Research Paper

Radar in the Modern World

Radar is usually taken for granted in these days of modern technology. Many people do not know how radar is really used, how it works, or why we need it. People are familiar with several uses of radar like police enforcement radar guns and radar that measures how fast a baseball is pitched in a major league game. These are only a few of the many uses radar has to offer. Radar can determine several properties of an object from a distance, such as its position, speed, direction of travel, and shape; it can also detect objects out of the range of sight in all weather conditions, making it a fundamental utility for many industries.

The term radar actually came from the acronym representing RAdio Detection And Ranging. Radar is a detection system used to locate and identify objects. Simply put, radar is the process in which radio waves are emitted from the source of the system; those waves ricochet off objects in their path, and the radar system detects the echoes of signals that return.

"One would think that so important a contribution to the world's technology would be chronicled with great care at every step...This, unfortunately, is not the case, and for reasons quite understandable" (Page 14). Sometimes history can be hard to distinguish from truth and legend, the history of radar is no exception. Many contributions have been made to the development of radar over the years. For many years prior and during the Second World War, radar was considered a top-secret military tool. Once it was made public, people used the existing information about radar to come up with their own variations for different applications. As a result, the true origin of radar has become blurred within conflicting claims.

Radar can be traced back as far as 1832 when British physicist Michael Faraday suggested the existence of an electromagnetic field between certain objects from his scientific observations. Working from these ideas, British physicist James Clerk Maxwell predicted mathematically the existence and behavior of radio waves in 1873. In 1886, physicist Heinrich Hertz from Germany and Elihu Thomson from America confirmed the existence of radio waves with demonstrations showing examples of reflection, refraction, and direction finding of radio waves. By 1904, Christian Hulsmeyer, a German inventor, applied for a patent for a device that used radio waves in a collision-avoidance device for ships. Hulsmeyer's system was not very accurate and only signaled when two ships' radio waves were in concurrent directions, which meant that they were headed directly for each other; however, it was only effective for a range of one mile. His detection device worked off the ship's existing low-frequency radios which did not travel very far. In June of 1922, Italian radio expert, Guglielmo Marconi drew attention to the fact that he had observed the reflection of high-frequency waves by metallic objects many miles away (Page 183); soon after this discovery, many people from around the world began developing devices to use this discovery for navigation purposes .

The first true discovery of radar was in September of 1922 when Americans Albert H. Taylor and Leo C. Young observed the interruption of high frequency radio communication by ship passing between transmitter and receiver. They also observed "beats" produced by large objects when they moved within the transmission area (between the source and receiver). Taylor and Young named it the beat method for a reason. While working with a high frequency radio communication from opposing sides of a river in New York, the normal steady tone that they were working on suddenly grew twice in loudness then faded into nothing. A short time after, the tone grew back to twice its original loudness, and then back down to its original decibel level. In curiosity, the men looked out to see that a large steam boat had just passed through their line of radio signal causing the gap in radio contact. Since both men were employed by the U.S. Navy, they knew the difficulties the navy had with guarding a harbor in low visibility (Page 21). At that moment, the first practical use of radar was born.

Radar was still in its infancy, but ideas were showing up everywhere. In 1930, Young and Lawrence A. Hyland were studying at the U.S. Naval Research Laboratory, experimenting with a short-wave transmitter and receiver over several miles. The receiver started to pick up unusual reception, and the tone fluctuated up and down. Looking for what was wrong, Hyland checked and rechecked all the possibilities. Finally, he discovered that at every instance the mysterious action took place, an airplane was flying overhead. With this new discovery, radar became a known science, and the military set up a formalized project titled Detection of Enemy Vessels and Aircraft by Radio (Page 26). These two discoveries by Young, Taylor, and Hyland were crucial in the development of the original form of radar. Without these discoveries, there would be no radar.

In 1925, Gregory Breit and Merle A. Tuve, two research workers from Carnegie Institution of Washington, performed many ionosphere experiments, the technique used in modern day radar (Shafford). Ionization is the formation of electrically charged atoms or molecules; initially, atoms posses a neutral charge and when an atom loses a negatively charged electron for one reason or another, it becomes a positively charged ion.

The ionosphere is a layer of ions in the atmosphere approximately 50 miles above the earth's surface extending up to 600 miles or more above the Earth. At these altitudes, the air is extremely thin allowing air particles to spread out. When the atmospheric particles are ionized by radiation, usually by the ultraviolet rays from the sun, they tend to remain ionized, because few molecular collisions occur in the upper atmosphere which would change them back to non-charged molecules. Most molecules at these extreme altitudes are ions making a layer of charged particles allowing the gas to become a conductor of electricity.

Using this charged layer, scientists could rebound radio waves off the reflective layer. The ionosphere also curves with the earth; therefore, it was possible to bounce a wave off the ionosphere and beyond the horizon to the receiver. Without this discovery, people would not know the possibilities of sending radio signals beyond the horizon because electromagnetic waves travel in a straight line to infinity until it meets an object obstructing its path. That object in this instance is