Last week the BBC showed a fantastic drama documentary on the early development of radar, with the excellent Eddie Izzard playing the key role of Robert Watson-Watt – the man who helped develop it.

The title quote “Building castles in the sky” is attributed to Sir Winston Churchill and referred to radar being used to defend the UK from German air attack.

The concept of radar came out of the desire to develop an offensive radio beam weapon to disrupt enemy aircraft in flight, something that proved a little too challenging for the time. However, the ability to detect aircraft at range – RADAR being radio detection and ranging – was ultimately achievable and the Chain Home network was conceived and built, contributing significantly to the outcome of World War II.

As with many drama documentaries, blurring of fact and fiction is par for the course, but this portrayal was comfortably close to what the history books tell us and is well worth a watch, giving credit to a British engineer who is often overlooked.

To this day, radar is used in both civil and military applications and remains a challenge to engineers in the quest to detect aircraft at long ranges whilst providing the accuracy that our air traffic controllers need.

These demands often conflict against one another as was illustrated in the programme. We need both high power transmitters and super sensitive receivers along with mechanical elements, and in the latest generation systems, some very sophisticated real time data processing. To this day modern evolutions of the original concept are in service in what we now call “Primary Radar” serving civil military and meteorological needs.

The radar station at Great Dunn Fell.

The radar station at Great Dunn Fell.

Since the earliest days radar systems have been evolving, with what we now call Secondary Radar developed from the ‘IFF – Identification Friend or Foe system’ that helped identify friendly aircraft from hostile. Secondary Radar provides additional information from the aircraft such as identity, height and in the most recent evolution known as ‘Mode S’ a number of supplementary aircraft parameters to support the ATC operation.

New technologies continue to appear, most recently we have ADS (Automatic Dependent Surveillance) and Multilateration systems, but all the latest systems currently require the aircraft to cooperate in some way with the ground systems.

Everyone who flies today owes a debt to Robert Watson-Watt and his team, with the technology they developed in 1935 remaining clearly traceable as the backbone of what we still use today.


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Alastair Campbell

As an Air Traffic Controller I have used radar for 35 years and kind of taken it for granted. Coincidentally, last night I watched “Castles in the Sky” and, as I’ve said elsewhere, having seen the struggles Robert Watson Watt had to get it to work, I will no longer take it quite as much for granted.



Chris Zarebski

Nick – Facinating stuff . For those interested in learing more I recommend
R. V. Jones’ Most Secret War: British Scientific Intelligence 1939-1945 which gives an excellent insight into the early days of radar and the battle of the beams.



Michael Katzmann

GEC Journal of Research had a nice technical description of the ‘Chain Home’ system on the 50th anniversary of the ‘Daventry Experiment’


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