AN INVISIBLE NET
As the Royal Air Force marks its centenary, Peter Ranscombe salutes three Scots who gave the service one of its most effective weapons – radar
Peter Ranscombe investigates the history of radar
Few sounds struck as much fear into the hearts of Britons during the Second World War as the drone of the air raid siren. From Clydebank and Liverpool to Coventry and London, the wailing of the klaxon heralded another night of hiding in an Anderson or Morrison shelter.
Yet if the air raid siren was the sound of fear then there was another noise that could make the heart leap with hope; the roar of a Spitfire or Hurricane engine as the fighters raced into the night sky to attack the enemy bombers overhead. While brave pilots sacrificed their lives to stop the Nazis from winning the Battle of Britain, their commanders back on the ground pored over their radio sets and table-top charts to direct the defence of the nation.
And we have three Scots to thank for one of the most effective weapons in their arsenal – radar. Without the technical ingenuity of Sir Robert Watson-Watt, the mathematical prowess of visionary physicist James Clerk Maxwell and the strategic foresight of Air Chief Marshal Sir Hugh Dowding, the course of the war – and the history of our land – could have taken a very different direction.
Radar – or radio detection and ranging – was used to spot enemy bombers as they approached Britain from the south and the east, allowing the Royal Air Force’s (RAF’s) fighter command to scramble its aircraft so that they were ready to meet the looming threat. While the air force had enough planes, it had a severe shortage of trained pilots, making it essential to deploy fighters at the right time and in the right place to defeat Hitler’s Luftwaffe.
Watson-Watt feels like one of the most unlikely war heroes. Born in Brechin and trained at University College in Dundee – at the time part of the University of St Andrews – he joined the Met Office in 1915 as a meteorologist.
Although he didn’t invent radar, he was the first to prove it worked on a
large scale. His first system was used to identify thunderstorms by detecting when bolts of lightning split or ‘ionised’ the air, knocking off some of the tiny electron particles orbiting around the nucleus at the centre of the nitrogen and oxygen atoms in the sky.
After leaving the Met Office, Watson-Watt became head of the National Physical Laboratory’s radio department. When the Air Ministry set up a committee in 1933 to beef-up Britain’s defences, he was asked to design a ‘death ray’ that would use radio waves to kill enemy pilots in the sky; rumours were rife that the Nazis already possessed such a weapon.
Watson-Watt quickly realised that such death rays were impossible because they would require so much energy to power them. However, he and his colleague, Skip Wilkins, calculated that they would be able to detect approaching aircraft before they could be seen with the naked eye by sending out radio waves and then measuring the time it took for the echo to return after bouncing off the aeroplane’s body.
Trials of their device began in 1935 using a BBC shortwave radio transmitter. It was able to detect the direction in which a Handley Page Heyford bi-plane was flying while it was 13 miles away.
Eventually, using a more powerful radio transmitter, the system could track aircraft that were 75 miles away. A network of radar stations was built along the south and east coasts, casting an invisible net across the sky and giving Britain a crucial edge when the Luftwaffe launched its major assault in 1940.
They say that all great inventors stand on the shoulders of giants, and such colossi don’t come much larger than Maxwell, who came up with the mathematics that not only underpinned Watson-Watt’s radar system but also forms the basis of much of our digital world, from mobile phones to satellite television. Not bad for a kid whose nickname at the Edinburgh Academy was ‘dafty’.
‘At school he was at first regarded as shy and rather dull,’ explained fellow pupil and physicist Peter Guthrie Tait. ‘He made no friendships and spent his occasional holidays reading old ballads,
drawing curious diagrams and making rude mechanical models. This absorption in such pursuits, totally unintelligible to his schoolfellows, who were then totally ignorant of mathematics, procured him a not very complimentary nickname.’
Maxwell developed the equations that underpinned the relationship between electric fields, magnetic fields and light. He even predicted the existence of the radio waves that would be used in radar systems.
Light is part of the electromagnetic spectrum, which links everything from the invisible infra-red and ultra-violet light that we can’t see, to the radio waves and microwaves that are used by mobile phones and wifi internet connections.
While Maxwell provided the maths and Watson-Watt developed the wherewithal, it took the vision of a third Scot to make radar a reality. During the 1930s, it was Dowding’s department at the Air Ministry that provided the funding for the first experimental radar stations, as well as the cash that developed the Spitfire and the Hurricane.
Then, as commander-in-chief of fighter command during the Battle of Britain, it was Dowding who brought his two investments together to defeat the Nazis. He was modest about his achievement: ‘Mine was the purely defensive role of trying to stop the possibility of an invasion, and thus giving the country a breathing spell… it was Germany’s objective to win the war by invasion, and it was my job to prevent such an invasion from taking place.’
Dowding’s network of radar stations passed information into the filter and operation rooms in his headquarters at Bentley Priory, linked to a further four operations rooms in regional groups around the country by a complex web of telephone cables. The set-up became known as the ‘Dowding System’ and was the world’s first integrated network of air defence.
Today, radar is still used as a key tool in aviation, tracking movements to keep both passenger and military aircraft safe in the skies. While the importance of its peace-time role cannot be underestimated, to the war-weary Britons emerging from their bomb shelters, radar was the RAF’s secret weapon that kept the enemy at bay during our country’s darkest hour.
A network of radar stations were built along the south and east coasts casting an invisible net