Editing Robert Watson-Watt (section)

==Early experiments==
In 1916, Watson-Watt wanted a job with the [[War Office]], but nothing obvious was available in communications. Instead, he joined the [[Met Office|Meteorological Office]], which was interested in his ideas on the use of radio for the detection of [[thunderstorm]]s. [[Lightning]] gives off a radio signal as it ionizes the air, and his goal was to detect this signal to warn pilots of approaching thunderstorms. The signal occurs across a wide range of frequencies and could be easily detected and amplified by naval [[longwave]] sets. In fact, lightning was a major problem for communications at these common wavelengths.{{sfn|Brown|1999|p=45}}

His early experiments were successful in detecting the signal and he quickly proved to be able to do so at ranges up to 2,500&nbsp;km (1500 miles). Location was determined by rotating a [[loop antenna]] to maximise (or minimise) the signal, thus "pointing" to the storm. The strikes were so fleeting that it was very difficult to turn the antenna in time to positively locate one. Instead, the operator would listen to many strikes and develop a rough average location.{{sfn|Brown|1999|p=45}}

At first, he worked at the Wireless Station of Air Ministry Meteorological Office in [[Aldershot]], [[Hampshire]]. In 1924 when the War Department gave notice that they wished to reclaim their Aldershot site, he moved to [[Ditton Park]] near [[Slough]], [[Berkshire]]. The [[National Physical Laboratory, UK|National Physical Laboratory]] (NPL) was already using this site and had two main devices that would prove pivotal to his work.{{sfn|Brown|1999|p=45}}

The first was an [[Adcock antenna]], an arrangement of four masts that allowed the direction of a signal to be detected through [[phase (waves)|phase]] differences. Using pairs of these antennas positioned at right angles, one could make a simultaneous measurement of the lightning's direction on two axes. Displaying the fleeting signals was a problem. This was solved by the second device, the WE-224 [[oscilloscope]], recently acquired from [[Bell Labs]]. By feeding the signals from the two antennae into the X and Y channels of the oscilloscope, a single strike caused the appearance of a line on the display, indicating the direction of the strike. The scope's relatively "slow" phosphor only allowed the signal to be read long after the strike had occurred.{{sfn|Brown|1999|p=46}} Watt's new system was being used in 1926 and was the topic of an extensive paper by Watson-Watt and Herd.<ref>R. A. Watt and J. F. Herd, [http://digital.nls.uk/scientists/pageturner.cfm?id=75132036 "An instantaneous direct-reading radiogoniometer"] {{webarchive|url=https://web.archive.org/web/20140202150615/http://digital.nls.uk/scientists/pageturner.cfm?id=75132036 |date=2 February 2014 }}, ''Journal of the Institution of Electrical Engineers'', Volume 64 (February 1926), pp. 611–622.</ref>

The Met and NPL radio teams were amalgamated in 1927 to form the [[Radio Research Station]] with Watson-Watt as director. Continuing research throughout, the teams had become interested in the causes of "static" radio signals and found that much could be explained by distant signals located over the horizon being reflected off the upper atmosphere. This was the first direct indication of the reality of the [[Kennelly–Heaviside layer|Heaviside layer]], proposed earlier, but at this time largely dismissed by engineers. To determine the altitude of the layer, Watt, Appleton and others developed the '[[squegging|squegger]]' to develop a '[[time base generator|time base]]' display, which would cause the oscilloscope's dot to move smoothly across the display at very high speed. By timing the squegger so that the dot arrived at the far end of the display at the same time as expected signals reflected off the Heaviside layer, the altitude of the layer could be determined. This time-base circuit was key to the development of radar.<ref>O. S. Puckle, [https://archive.org/stream/TimeBasesTheirDesignDevelopment/Puckle-TimeBases_djvu.txt "Time Bases, Their Design and Development"], Chapman & Hall, 1943</ref> After a further reorganization in 1933, Watt became Superintendent of the Radio Department of NPL in [[Teddington]].{{citation needed|date=February 2021}}