Allied Radar Fighters 1938 - 1945: Air War in the Darkness

Forgetting the lessons learned in the fight against Zeppelins during the First World War, the British Ministry of Aircraft production considered that the production of specialized night fighters was a waste of resources.
The Technisches Amt (Technical Office of the Luftwaffe) was of the same opinion and delayed for years the production of the Heinkel He 219, the only one of the seventeen twin-engine German airplanes that measured up the Pathfinder Mosquitoes.
Both institutions showed a great lack of vision in blocking all the night fighter projects proposed by the industry.
By mid-1940 the reality of night combat showed how unprepared both air forces were for this type of war.
The medium bombers Bristol Blenheim and Dornier Do 17 converted into emergency night fighters were too slow and heavy to be effective.
In 1934 German scientists of the GEMA obtained their first practical radar that operated in 50 cm wavelength.

In 1939, Telefunken manufactured a radio telemeter and proposed, without success, its manufacturing as radio altimeter for the Luftwaffe. In February 1940 the research went on, tilting the beam towards the horizontal to use it in the location of aircrafts.
The Matratze antenna (with four double pairs of 27.5 cm dipoles) mounted on the aircraft nose reduced the speed in 25 mph. This was not much of a problem for a Messerschmitt Bf 110, but reduced excessively the performances of the heavy night fighter Dornier Do 217.
The British solved the problem of the drag parasite produced by its Yagi antennas using microwaves, generated by a magnetron, and small parabolic antennas enclosed in aerodynamic radomes.