Early Radar Memories

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The huge CH aerial masts were clearly visible even from large distances, attracting the attention of German intelligence already in the years preceding the ...
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The huge CH aerial masts were clearly visible even from large distances, attracting the attention of German intelligence already in the years preceding the war. Surprisingly, the Germans did not discover their true purpose until 1940 but once they did, several attempts we made to bomb the RDF stations from the air. Pevensey was attacked this way on 12 August 1940 and temporarily put out of action. Fortunately, it took only 6 hours to bring it back on the air again.
[Tc7 via Flickr]

Tracking the Luftwaffe

Jean had to watch the early type RF5 screen with a hairy RAF blanket thrown over her head as the cathode ray tube was weak and therefore hard to see.

On her very first day of operation, in 1940, at Pevensey, she saw on her screen a large number of what were probably Heinkels and Dorniers. She informed her (male) supervisor and suggested he take over but he said: ‘It’s Your Operation, you do it.’

At this early time there was no pressing of buttons. You worked out your own plots. It was hard to count the exact number of planes as they were all coming together and going up and down – which is called beating. You don’t see a separate blip for each one when there’s a lot bunched together.

Jean counted the number of aircraft as an unprecedented 200 plus. She and her supervisor reported the sighting to Stanmore, which could hardly believe Jean’s figures. Could they be dealing with migrating birds?

The plotter in the filter room at Stanmore said she would have to seek verification from her scientific observer who was looking down on the plotting from the window above. Jean was proved to be right. Not birds but planes. Nearly 200 enemy planes.

In those early days at Pevensey you were able to speak to the pilot. Both the operatives and the pilots used nicknames. One character who was often called upon at that time was Blood Orange Smith. Blood Orange was meant to be a reconnaissance pilot but often got bored and went after the enemy. He always came back safely.

You had to plot outgoing friendly planes as well as incoming enemy ones. Distinguishing between the two was another difficulty inherent of the early CH operations, but by the time of the Battle of Britain, RAF combat aircraft carried special ID system called IFF. Jean explains:

‘If we were sending up fighters into the heart of the battle you could be plotting one of your own planes believing it was the enemy, so you needed an ID to establish that they were friendly. This was called IFF – Identification, Friend or Foe.’

At a later point, Jean returned to Bawdsey in an operational capacity. At this time Stanmore decided that their own personnel would benefit from knowing where their plots were coming from and arranged a two-week exchange. Thus my sister found herself seated at the famous board in Stanmore’s filter room. She remembers:

’There was a Halma Clock on the wall. Its face was divided into colours. Time was divided into colours. There was never more than 2-1/2 minutes of plotting on the table at one time because everything was moving so quickly.

A number of people looked down at the plotting from the windows above. The scientific observer, of course, plus VIPs, the BBC, representatives of the Army and Navy, members of the Observer Corp and, frequently, Lord Dowding himself wearing full uniform and, I was told, his carpet slippers.’

Jean still has a photograph of Betty Smith, the girl she made the exchange with, who she believes went on to become a film actress.

Radar improvements

As the war progressed, many modifications and improvements were made to the original equipment, although its basic modus operandi remained the same. In due course Jean moved onto the more sophisticated RF7. This had a vastly improved cathode ray tube that allowed her to throw off the hairy blanket and watch her screen in a more convenient way. Jean still has a drawing that she made of an RF7.

Schematic drawing of the RF7 radar receiver from Jean’s personal notebook
[Jean Semple]

Illustration of the RF7 receiver unit from the contemporary RAF handbook makes for an interesting comparison with Jean’s drawing.
[Crown Copyright]

With the newer equipment you could provide a signal that an Allied pilot could switch onto if need be. For instance, in the event that he had broken away from the squadron and lost his bearings. This signal could only be used as a last resort as it could be picked up by the Germans.

In early RF7 days, at one station, 11 and 12 Group operated a system called Spotted Dog. Set next to the observer was a large console about four-foot-square covered with Perspex. Jean remembers:

‘Laid out on the console under the Perspex was our section of a map of Britain. The Perspex itself was marked with an ordinance grid reference. The console had a gadget, connected to a range finder. This gadget was an illuminated spot the size of a farthing.

Once the operator had an optimum reading they would stop the gadget. A person standing beside the operator with a clipboard wrote down time, seconds and plot. Another person turned to the console and marked the position on its ordinance grid with a grease pencil. Meanwhile, the observer made speech contact with the filter room at Stanmore.

All the plots recorded on the clipboard were later transferred to another map. The idea was to see where, in principal, all the dots were collecting and where they were not. In the end you had big patches of dots and other areas where there was nothing. You could draw a line round the big patches of dots, like a balloon. These were called lobes. The areas remaining would be the blind spots that Jerry could take advantage of. ‘

Connected to the Radar Station’s four aerials was the Parent Unit, the Plan Position Indicator. The PPI’s parabolic reflector resembled our modern satellite dishes. There was a little tube in the centre of it, which was hollow. No one seemed to know why it worked, but it did. The PPI was connected to a cathode ray tube that produced not a thin line but a wide sweep. This system adequately covered the lobes and the vulnerable gaps between the lobes. In due course a curtain array was, including 100-foot dipoles that could be energised at will.

Another procedure to ensure accurate observing and plotting was by use of a theodolite. A rigger would climb the 340-foot steel aerial with the theodolite. Meanwhile, an autogiro would be flying at a pre-determined height and bearing. The theodolite then took the true reading of the height and bearing of the autogiro. Its results would be picked up on the CH cathode ray tube and compared with the less accurate Goniometer plot. The discrepancy would be declared a percentage of a pure rose, and would be drawn as, for instance, a 90 to 95% distorted rose and allowances could then be made for the differential. After a while, this work became automated with the help of RAF General Post Office equipment and personnel working from a sub-station.

By 1943, the bomber offensive was in full swing and with it, the aerial operations intensified beyond recognition. Jean remembers:

‘As war progressed we were sending up 1000 bombers at any one time and they all had to be plotted. The plotting was enormous for 1000 bombers so we had to divide our maps into four. Taking each quarter you tried to give four readings, an inner and an outer reading both of bearing and of range. We’d start with a mean range, appearing like a range of mountains, with inner and outer edges and four corners. Sometimes the planes were miles apart.’

Jean (Sally) Semple achieved the rank of Sergeant and had the chance to go further, having been twice recommended for a commission. Marriage intervened, however, and she left the service with a Clause 11 discharge – pregnancy. Her friendships with fellow Radar Operators continued into civilian life with her closest colleague, Joan Pile, dying only a short time ago. Jean and her husband have recently moved from the Welsh countryside to a pleasant town house close to leisure amenities.

Jean would like me to end this account with a question: ‘On every watch, a civilian male would sit in the corner of the operations room wearing a set of headphones. He never spoke or wrote anything down. He was known as “The Headache.” Does anyone know what he was doing?’

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12 Comments | Add New

By Lesley Griffiths  |  2013-08-11 at 21:22  |  permalink

Dear Katherine and Jean – fascinated to read this. My mother, then Mercia Lovett, was a radar operator on Romney Marsh n WW2 – I ssume this was RAF Rye asi t seems the only likely candidate. I know it’s a long shot, but see Jean was there at one time. I know it’s 70+ years ago but I wonder if Jean remembers the name of any of her colleagues there. My mother married David Griffiths, an RAF sergeant, in June 1945 at Willesborough Parish Church in Ashford. Sadly Mum died in 1966 and so I never got around to asking her the questions that I now wished I had.
Very best wishes to you both

By David Savage  |  2014-09-27 at 10:01  |  permalink

Hello I am looking for any memories of Coastal Radar Stations in Somerset. Particularly in the Minehead, Wachet , Ilfracombe areas. I am aware of the Northhill site but any 2WW and Cold War information would be greatly appreciated inlcuding and especially Northhill.

Many Thanks

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