Radar revolution

12 May 2020

Interview with 

Craig Murray, Imperial War Museum Duxford

RADAR-SCREEN

A stylised radar detection screen, a series of concentric circles split into eight sections

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The outcome of the Battle of Britain was heavily affected by radar. Radar, coined by the US Navy as an acronym of Radio Detection and Ranging, works sort of like how bats find prey. A transmitter blasts out a signal, it bounces off incoming objects, and depending on the signal that’s received back, you can tell, what, if anything is inbound. But how did it get developed. Adam Murphy spoke to Craig Murray from the Imperial War Museum in Duxford...

Craig - Radar certainly is not a British invention, but its one perfected for its use by the British to do what it's supposed to do. The Germans have come up with a think for use in the German Navy for ships, but it's never really exploited as such. But the actual technology, the radio direction-finding technology it comes off, has been really around since the early days of radio development and in the early 1900s they're using it to get fixes on things, usually for for weather, for boats. You can't really tell how far something is, but you can get a fix on a where it is, if that makes any sense. It's more 'we know it's there', but the technology is so limited, it can only be used for relatively short-term meteorological stuff like incoming storms or fog that's quite close. What happens in the 1920s is a guy, a Scottish physicist called Robert Watson-Watt, who is with the Met Office but he works with the National Physical Laboratory on the radio research section, that kind of combined labs; he's got an interest in radio waves.

And he develops a system called huff-duff for the Met system, and it basically instantaneously gives you a fix; and the Met Office use it to develop weather reporting for aviators so they can tell when storms are coming in. So he has this. After, I think it's in '27, the labs of the Met Office and National Physical Centre are amalgamated into this new lab, and he's put in charge. And he takes on this guy called Alfred Wilkin in 1931, and they run a report based off of this, that aircraft nearby cause this fading in the signal. It's basically, the strength comes and goes; which is a bit irritating if you're listening to the radio, the sound comes in, it comes out, drops out, distorts, and clips. And so with these three things going on, they've kind of got the basis for something that can work on radar. Because even back in the early 1900s they realised that metal reflects radio signals, and in fact aircraft being present in an area is distorting the signal. It's this idea that there's something there.

Adam - But how does that translate to a full military sensing infrastructure? Well, like with all good spy stories, it starts with a death ray.

Craig - In 1934 the Tizard Committee, who are basically there to look into research for air defence... because the theory up to then, and something that was put forward, was the bomber will always get through, you can't really defend against them because we don't know when they're coming, et cetera, et cetera. And in 1934 the RAF ran a big exercise with some 350 aircraft they split into two: one lot would be the bombers, one lot would be the fighter defenders, and the only information they get would be from observers on the ground reporting incoming raids. And what they found was that 70% of the bombers could hit London without even meeting a fighter. So this wasn't good. And there were also rumours going around at the time - and this is where the Tizard Committee start contacting Watson-Watt - there were rumours of a death ray that could be produced using radio signals. Now anybody with a working brain pretty much knew this was bunk, it was just utter nonsense; but the RAF, the Air Ministry, and the Tizard Committee were like, "well, we need to check this out, because if there is anything in it you don't want the Germans having it; because if they do have it, they're going to knock out air fighters as their bomber come in, and vice versa". So they thought, "we'll at least run it through science. Let science decide if it's bunk or not". Wilkin is given the task by Watson-Watt to have a look at it, and pretty much quickly turns and says, "it's nonsense, it'll never work. But I'll tell you what it does do, the radio waves: it can detect incoming objects." And this is reported back to the Tizard Committee, and they're like, "yeah, thanks for telling us, we kind of knew that. We hoped what you'd say was that the death ray thing is bunk, and it is; but we like this, this is interesting what you've got here on incoming things."

Adam - So with a new potential way to turn the tide in their favour, it was a matter of investing heavily in the science of it all.

Craig - In 1935 they've got something, they can spot something coming in at a hundred miles out. A little bit later than '36 they've managed to get the towers working so they can actually determine height of the incoming raid as well. And it's not until '40 when you've got these rotating radars we think of now that can read inland. As it turns out, because the Germans rule over France relatively quickly, they're basing their aircraft at Calais, so something they thought would be coming from a long way off originally is now coming from 20 miles across the Channel. I always like to think of it as being a bit like the internet invented by the US military in the 1960s. It has no centre that could be knocked out; I mean, this applies to the radar station. Pilots buy instinct don't fly near to pylons, it's a scary thing, because there's wires and that's just asking for trouble; and also bombing them is very difficult because they're a latticework tower, and explosions tend to come out, so it's very hard to destroy. And even if you do manage to destroy them, the neighbouring station can take over its sweep, so they compensate for each other. So it's a nigh-on impossible tasks for the Germans to remove this system, coupled with the fact that they don't fully understand what it does, and they don't really get the radar is picking them up. They just don't seem to get the radar thing at all.

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