In 1935 the British government asked sir Robert Watson-Watt to inspect the possibility of inventing a radio “death-rays”, which could melt the metal or displace a plane from a fight with sufficient energy. Watson-Watt gave over this problem to his assistant Arnold Wilkins. He made all calculation and enunciated, that so far it is not possible to do it with the available electronic technology. But he foreshadowed and later also proved with his calculation, that if the radio waves bounce back from the flying plane, it is possible to locate its position. (We can see the same effect at the bats, that are flying in an absolute darkness but do not crash into anything. They give off high frequency-tones, that are bouncing back from the objects around and help them to locate the exact position of these objects.) The government committee was enthusiasted with this idea but demanded an ease and practical demonstration to assure itself, that the idea is realistic. The experiment was prepared: on 26^th February 1935 the bomber Heyford flew into the beam of radio waves of the BBC transmitter in Daventry, that was transmitting on the wave-length 49 m. The receiver detected these echoes and pictured them on a screen. The plane had been identified up to the 8 miles´ distance. By December 1935 the production of the first 5 pcs. of the so called CH-stations (first radars were called “Chain Home”) was authorised. By the year 1939 the whole chain of radar stations was operating along the east and south coast of Great Britain. The name “radar” was invented by S. M. Tucker from the American Navy in 1940: it is an abbreviation of an English word “radio detecting and ranging”. In the same year the radar have already played an important role in the “Battle of Britain” against the German Luftwaffe and later, when the radar was integrated into the fighters, bombers and became a part of the ground groups, it became the key-helper by locating the air and naval enemy targets.

The radar system is largely used in naval and air-navigation, traffic (measuring of speed) and meteorology. But the military utilisation is still dropping: thanks to its principles it is easily locatable and is becoming a target for the enemy…

The meteorological radiolocator Praha-Libus (wave-length 3,13 cm, 9595 MHz, the impulse-length 2 mks, the repeat frequency 252 Hz, radius 256 km). It is used to detect the bold rain-fall clouds, it also allows the estimation of the immediate rain-fall intensity. It uses the bounce of the microwaves from the water drops and icy crystals. (Figure was taken-over from the webside http://www.chmi.cz/meteo/rad/rad_sit.html)