Editing Chain Home (section)

===Radio research in the UK===
[[File:Robert Watson-Watt.jpg|thumb|upright=0.8|[[Robert Watson-Watt]]'s position with the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] placed him at the centre of a network of researchers whose knowledge of radio physics was instrumental to the rapid development of radar.]]

Since 1915, Robert Watson-Watt had been working for the [[Met Office]] in a lab that was colocated at the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]]'s (NPL) [[Radio Research Station (UK)|Radio Research Section]] (RRS) at [[Ditton Park]] in [[Slough]]. Watt became interested in using the fleeting radio signals given off by [[lightning]] as a way to track [[thunderstorm]]s, but existing RDF techniques were too slow to allow the direction to be determined before the signal disappeared. In 1922,{{sfn|Bowen|1998|p=7}} he solved this by connecting a [[cathode-ray tube]] (CRT) to a directional [[Adcock antenna]] array, originally built by the RRS but now unused. The combined system, later known as [[huff-duff]] (from HF/DF, high frequency direction finding), allowed the almost instantaneous determination of the bearing of a signal. The Met Office began using it to produce storm warnings for aviators.{{sfn|Watson|2009|p=39}}

During this period, [[Edward Victor Appleton|Edward Appleton]] of [[King's College, Cambridge]] was carrying out experiments that would lead to him winning the [[Nobel Prize in Physics]]. Using a BBC transmitter set up in 1923 in [[Bournemouth]] and listening for its signal with a receiver at [[Oxford University]], he was able to use changes in wavelength to measure the distance to a reflective layer in the atmosphere then known as the [[Kennelly–Heaviside layer|Heaviside layer]]. After the initial experiments at Oxford, an NPL transmitter at [[Teddington]] was used as a source, received by Appleton in an out-station of King's College in the East End of London. Watt learned of these experiments and began conducting the same measurements using his team's receivers in Slough. From then on, the two teams interacted regularly and Watt coined the term [[ionosphere]] to describe the multiple atmospheric layers they discovered.<ref>{{cite book |first=Robert |last=Clark |title= Sir Edward Appleton G.B.E., K.C.B., F.R.S. |url=https://books.google.com/books?id=fZg4BQAAQBAJ |publisher= Elsevier |year=2013 |pages=39–45, 51, 53|isbn=9781483153766 }}</ref>

In 1927 the two radio labs, at the Met Office and NPL, were combined to form the Radio Research Station (with the same acronym, RRS), run by the NPL with Watt as the Superintendent.{{sfn|Bowen|1998|p=7}} This provided Watt with direct contact to the research community, as well as the chief signals officers of the [[British Army]], [[Royal Navy]] and [[Royal Air Force]]. Watt became a well-known expert in the field of radio technology.{{sfn|Bowen|1998|p=7}} This began a long period where Watt agitated for the NPL to take a more active role in technology development, as opposed to its pure research role. Watt was particularly interested in the use of radio for long-range aircraft navigation, but the NPL management at Teddington was not receptive and these proposals went nowhere.{{sfn|Bowen|1998|p=9}}