In the first world war, there was no such thing as a radar, or any form of scanning device, so that the war was only fought by eyes and ears. Whoever heard, or saw the ships first would have had more time to prepare. As far back as June 1932, there had been Post Office Reports about a plane interfering with radio signals, and re-radiating them. Then Sir Robert A. Wast on-Watt, A British Electronics Genius, (the man who invented the stereo with only two speakers) came up the idea of RDF, Radio Direction Finding. With his staff A.
F. Wilkins, he was able to submit a paper about a thing called radar as codename, in 1935. It was proved that the theory would work, but with a range of only 8 miles. Then and there started the radar research. By 1939, the Germans also had their own RDF installation, named the Freya. It proved quite effective in picking up British bombers, and they were able to pick up bombers ensemble at 114 kilometers.
Although as early as September, Britain had radar stations all over the country, 16 altogether to give air raid warnings, but those radar can only give air raid warnings, as it is designed to do. It can by no means radar scan the air and it is so bulky so that it cannot be made portable. The British ASV I (Air to Surface Vessel Mark I) portable radar, (quite bulky, still, even for a ship, ) had an extremely short range, and was terribly inaccurate, because of the wavelength used, so it cannot detect small objects, only big. In experiment, the ASV III had used a magnetron oscillator valve, and it had a wavelength of nearly as short as 10 cm, and would have been very accurate for 1941, but the receiver was not as good as it should be, so it had a range of only 6 miles. The early British radar development was always handicapped by its range.
In 1941, ASV II was put into mass production, 4000 sets was ordered. It had a range of 12-20 miles, still handicapped by its receiver. It was a lot more practical than ASV I, anyhow, as it was designed for mass production. It was not until 1942, when the U-boats were zooming about everywhere, an ultra breakthrough of ASV III/H 2 S boosted the British radar industry, a new receiver. The range was increased to 40 miles. There were scientific arguments over whether the Bomber (H 2 S) or Coastal (ASV III) Command had the priority.
It was decided that H 2 S may be used first. It turned out to be a wrong decision, A Stirling fitted with H 2 S was shot down near Rotterdam on February 2, the H 2 S were retrieved by the Germans. But the German Scientists were never able to make a receiver in 2-3 months, as suggested by Watson-Watt. It was 8 months time, before a Naxos-U receiver was made against ASV III systems, thanks to the huge gap in technology between the British and the German. By the time that Naxos-U and Naxos-U anti-bomber were put into operation (October 1943, January 1944, ) it was already too late for the Germans. D-Day was about to arrive.
The story of radar can go on and on until today, and the development of radar-proof bomber planes, but the second world war was over, The Germans surrendered. The radar was only a small, but very important contribution. The second world war was very much a war of intelligence and technology. This is not really a part of the project.
It maybe is interesting to see what amazing theory that Sir Robert Watson-Watt came up with in 1935.