In the first decades of the twentieth century, Europe and the United States began to notice that airplanes flying in the sky create some interference in radio communications, since radio signals are partially reflected from airborne equipment. Soon, this phenomenon began to be deliberately used to detect various distant objects. As a result, radar stations were built.
The principle of operation of the radar
The radar station (radar) has a different, abbreviated name - radar. This is an abbreviation of the phrase "radio detecting and ranging", which translates as "radio detection and ranging." Such a station operates according to the following principle.
First, radio pulses are sent from the radar transmitter with a very high frequency, after which the receiving antenna picks up any echo of the radio signal that has reached the place of radiation.
The direction from which the signal comes after reflection from a solid surface is called the target azimuth. The distance to it can be calculated based on the time it takes for the signal to travel to the target and back.
First inventions and experiments
A device of this principle of operation was patented in 1904 by an engineer from Germany Christian Hülsmeier. It was called a telemobilescope. However, on German soil, the device was not used anywhere.
In 1922, US Navy engineers began experimenting with transmitting radio signals across the Potomac River. As a result of such experiments, ships fell into the detection field, which during the passage blocked the path of the emitted radio waves.
Robert Watson-Watt, a physicist from Scotland, was researching how radio waves could be used to detect airplanes in mid-air. He patented his radar in 1935. The British, realizing that World War II would soon begin, by the beginning of autumn 1938 had built a number of radar stations along some strategically important coasts of England.
Also, the radar began to be used for accurate targeting of anti-aircraft and naval guns.
Magnetron and klystron
Radars had a very high frequency of radiation, which required special electronic equipment. The first transmitters were equipped with a magnetron - an electrovacuum device. Physicist Albert Hull (USA) was engaged in its construction. By 1921, the device was created.
But 14 years later, the engineer Hans Holman invented the multi-cavity magnetron. A similar device was assembled in the USSR in 1936-1937. (led by M. Bonch-Bruevich) and in Britain in 1939 - physicists Henry Booth and John Randall.
9 cm - this was the length of the radio waves that the new device produced. Thanks to this, the radar was already able to detect the submarine's periscope from a distance of 11 km.
In 1938, two brothers from the United States, Russell and Sigurd Varian, invented another device for amplifying the radio signal - the klystron.
Use of the radar for peaceful purposes
The fighting in the war is over. The radar was still in use. But not for military purposes, but for peaceful purposes. In 1946, experts in the field of astronomy received a radio signal reflected from the lunar surface, and in 1958 - from the surface of Venus. Astronomers from the USSR have successfully studied (using radar) other planets - Mercury (in 1962), Mars and Jupiter (in 1963).
The NASA space agency has used spacecraft in orbit to map the ocean floor of the globe. Also, radars are of great help to meteorological services in predicting the weather.
