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vcvc Δλ λ Δω ω ── ═ ── ═ ── The Doppler Shift

In 1915 Robert Watson-Watt joined the Meteorological Office as a meteorologist. Working at an outstation at Aldershot, in Hampshire, Britain, he developed the use of radio signals generated by lightning strikes to map out the position of thunderstorms. The difficulty in pinpointing the direction of these fleeting signals led to the use of rotating directional antennas, and in 1923 the use of oscilloscopes in order to display them. An operator would periodically rotate the antenna and look for "spikes" on the oscilloscope to find the direction of a storm. At this point the only missing part of a functioning radar was the transmitter.Robert Watson-WattMeteorological Office meteorologistAldershotHampshireBritainlightningthunderstormsoscilloscopestransmitter By 1934 Watson-Watt was well established in the area of radio as head of the Radio Research Station at Ditton Park near Slough. He was approached by from the Air Ministry, who asked about the use of radio to produce a 'death ray', after hearing Germans claims to have built such a device. Watt quickly wrote back that this was unlikely, and he pointed out that in the absence of progress, meanwhile attention is being turned to the still difficult, but less unpromising, problem of radio detection and numerical considerations on the method of detection by reflected radio waves will be submitted when required. Watson-Watt and his assistant Arnold Wilkins published a report on the topic on February 12, 1935, titled The Detection of Aircraft by Radio Methods.Radio Research StationDitton ParkSloughAir Ministrydeath rayArnold WilkinsFebruary The Daventry Experiment 26 February 1935, set up by A.F.Wilkins and his driver, Dyer, to demonstrate the feasibility of RADAR.26 February1935A.F.Wilkins On February 26, 1935 Watson-Watt and Wilkins demonstrated a basic radar system to an observer from the Air Ministry Committee the Detection of Aircraft. The previous day Wilkins had set up receiving equipment in a field near Upper Stowe, Northamptonshire, and this was used to detect the presence of a Handley Page Heyford bomber at ranges up to 8 miles by means of the radio waves which it reflected from the nearby Daventry shortwave radio transmitter of the BBC, which operated at a wavelength of 49 m (6 MHz). This convincing demonstration, known as the Daventry Experiment, led immediately to development of radar in the UK.February NorthamptonshireHandley Page HeyfordDaventry shortwaveBBCm

Radio detection and ranging (radar) is viewed by most as one of the quintessential technological accomplishments of the Twentieth Century. Radio detection finding or RAD, as it was known in Great Britain, was perhaps the single biggest piece of technology, aside the atom bomb, that emerged from of the ashes of World War II. The employment of RAD made the defence of Britain possible. The Royal Air Force enjoyed a major technological advantage during the Battle of Britain because most of the time, they knew where was headed the bulk of the Luftwaffe force. It could be argued that without radar, the fierce battle that ranged over the skies above the British country side would had been lost. Radar also warned the Americans at Pearl Harbour of a massive airborne formation heading towards them. Unfortunately for the United States forces at Hawaii, misinterpretation of the radar data lead to the attack being a ‘surprise’. Radar was used extensively by the Americans in their Pacific and Atlantic campaigns. Today, many facts about the development of radar is widely known. What is seldom mentioned by historians and researchers alike is the fact that in the beginning, it was Nazi Germany, not Britain, which was leading the way in the field of radio detection. On a the clear morning of September