An early-warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the air defences the maximum time in which to operate. This contrasts with systems used primarily for tracking or gun laying, which tend to offer shorter ranges but offer much higher accuracy.
PAVE PAWS Early-warning radar, Alaska
RAF Fylingdales, Pave Paws Ballistic Missile Early Warning System, North Yorkshire
AWACS plane
Chain Home, or CH for short, was the codename for the ring of coastal early warning radar stations built by the Royal Air Force (RAF) before and during the Second World War to detect and track aircraft. Initially known as RDF, and given the official name Air Ministry Experimental Station Type 1 in 1940, the radar units were also known as Chain Home for most of their life. Chain Home was the first early warning radar network in the world and the first military radar system to reach operational status. Its effect on the war made it one of the most powerful systems of what became known as the "Wizard War".
Chain Home at RAF Poling, West Sussex
Robert Watson-Watt's position with the 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.
Stanley Baldwin's 1932 comments on future aerial warfare led to a "feeling of defencelessness and dismay." It was the UK's concern about this issue that led to so much support being given to radar development while other countries had a much more lackadaisical approach until the war started.
A 1925 radio magazine photograph of Grindell-Matthews' death ray