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'We spent six weeks at Yatesbury, near Calne, Wiltshire, on a most intensive training course,' remembers Sydney Partridge, born in London in 1922, 'with day and night shifts all around the clock in dark operating rooms. The concentration was so intense that some of us talked in our sleep, muttering ranges and bearings, along with any other thing that was in our minds.'
Sydney, aged 19, joined the RAF and was being trained for 'Radio/Direction Finding', later known as RADAR.
'All of us operators were from similar backgrounds, reasonably well educated in English, maths, etc., but with very little knowledge of electricity let alone radio, so we had a lot to learn. But most of us managed to meet the 'passing-out' requirements (with the incentive of a week's leave at home, if you passed!) and were then 'posted' to various operational RDF stations around the Southern and Eastern coasts of England.
I think I should here explain that Radar was not then the sophisticated thing that you see in films or on TV nowadays. During the War all radar operators had to work in the dark to allow the maximum visibility of the 'signal' and to protect the luminosity of the radar 'screen' from being weakened, by exposure to the light. A sheet of cardboard covered the face of the screen whenever daylight was let into the room, during cleaning and maintenance.
The operators in the main 'Chain Home' (CH) stations did not have a revolving 'trace' on the screen but simply a horizontal line with vertical deflections (such as you see on one line of an 'ECG' heart-monitoring machine in hospital series on TV). On radar, the deflections are of varying strengths and distances from the start of the line, and are caused by various objects, which cause a reflection of the energy of the radio wave, such as aircraft, barrage balloons, tall hills etc. The whole of the line may be made 'fuzzy' by radio interference ('atmospherics'), which makes the genuine responses from real objects more difficult to identify. A seal is super-imposed on the screen so you can read off the distance in miles (radio waves travel at a speed of 186,240 mph), so the time taken for the response to get back from the object can be translated into the distance it is from you.
The skill of the radar operator is to pick out the real objects from the 'fuzzy' line to identify what it is, if possible, and to find what bearing (compass bearing) it is from the radar station. This is called DF-ing ('direction finding') and once you have the direction and range of the object from the station, you can 'plot' its position on a grid-reference map, and pass the information of the resulting grid reference to the Filter Operations Room at Flight Control. This is done by telephone, where the Filter Room WAAFs put identification counters on their huge map to show the position etc. of the object. This is so that the Flying Control officers on their dais overlooking the huge map, can direct our fighter aircraft onto an interception route to attack the hostile(s), keeping radio telephone contact with the pilots all the while.
Although I did my initial training on the above 'Chain Home' equipment, I spent most of my service with a later development that was used on 'Chain Home Low' (CHL) station. This had a lower search area than the CH stations, using a special shape of aerial which focused the radio signals into a 'beam' (like an invisible searchlight beam), about eleven degrees wide, which could be turned through an arc of say 120 degrees. One 'swept' the aerial through that 120 degree arc by hand turning of the wheel that controlled the aerial, and when you saw a suspicious object you focused the aerial on it, turning the aerial slightly to left and right of it until you found the precise bearing. You then passed that bearing and the range to another operator who converted it on the map into a grid reference, which he passed to the Filter Room.
The aerial was rather like a bed spring, about 12 ft. long and 6 ft. high with a wire mesh reflector mounted behind the radio 'di-poles', to direct the radio signals forward into a beam. This 'bed spring' was mounted on a vertical pole, which went through the roof of the operators' hut. The lower end of the pole had the controlling mechanism mounted on it, with a steering wheel (from a motor car) attached to it, and a small wooden handle clamped onto one of the spokes of the wheel. *(See picture 16a of notes). * This was beside the operator's position and, as he gazed into his radar screen, he turned the handle which rotated the aerial above him. There was a considerable strain on the bolts which clamped that handle onto the wheel, as the operator suddenly stopped the aerial, then reversed it and went forward again in a series of jerks when action was at its height. Occasionally the clamp-bolts on the handle would sheer off and the operator had to grab hold of the car steering wheel with both hands, to prevent the aerial revolving out of control, especially in a high wind. This happened once while I was operating it and it was quite an experience!
The problems with this equipment were resolved by the invention of so-axial cable for the feeding of the transmit and receive signals, and this allowed the continuous 360 degrees revolving of the aerial. At the same time the radar 'tube' was re-designed to provide a revolving trace, like a minute hand, with the 'trace' radiating from the centre. The received signals were fed onto the revolving 'trace' as an increase in brilliance (instead of a vertical deflection) and as the trace revolved, so the increased brilliance painted a sausage-shaped 'blip' onto the 'after-glow' surface of the screen. With the aerial turning at 3 revolutions per minute, the next revolution painted the latest position of the object onto the screen as a fresh 'sausage', before the previous one had faded from the after glow. With the next revolution painting a later position, the afterglow enabled one to see that an object was moving in a particular direction with the succession of gradually fading 'sausages'.
The placing of a transparent perspex grid reference map in front of the screen meant that the operator could read off the grid reference directly from the screen (using his judgement of the position of the object from the middle of the curved 'sausage'). This was done by mentally sub-dividing each square of the grid into tenths, vertically and horizontally, to give the four figure reference that was required for accuracy in 'plotting' the track of the object. This system of the revolving trace was called the 'Plan Position' (P.P.I.) which is still used by Air Controllers for civil airways etc.
This system of 'direct control from the radar screen' was used to produce 'Ground Controlled Interception' (GCI) whereby a former pilot could sit beside the tube in the GCI station, and talk directly by radio telephone to the pilot of the aircraft which was intended to intercept the Hostile(s).
This was achieved by the use of GCI equipment on the ground together with 'Air Interception' (AI) equipment, installed in night fighter aircraft (usually 'Beaufighters') which, in addition to its pilot, carried a radar operator who had two radar tubes in front of him. These tubes told him whether the hostile aircraft was I. above or below him, 2. to the left or right of him, and also 3. how far away it was. He would then advise the pilot whether to go higher or lower and whether to turn left or right and, having got their aircraft into the correct position, what distance remained. The pilot could then increase speed until he could see the flames of the enemy's exhaust pipes, by which time he was usually near enough to shoot down the enemy aircraft.
The whole operation was conducted at night, (usually moon-less) which the enemy night bombers preferred, for their own safety from interception by non-radar fighters, and anti-aircraft fire. So it was very much a combined operation from the ground radar, finding the hostile aircraft, passing its position to the GCI station, which then tracked it until it could direct the AI aircraft to a position behind the hostile. Then direct its course and speed until it was only 4 or 5 miles behind the hostile, and instruct it to bring its airborne radar into use, finally, when the latter had 'picked up' the hostile, to hand over control to the AI aircraft to complete the interception.
As part of the morale boosting for the British Public, the success of night fighters was attributed to feeding them on carrots! The most successful of them was referred to as 'Cats-Eyes Cunningham'. Cunningham flew off from Middle Wallop Airfield (near Stockbridge, Hants) and his control station (GCI) was at Sopley (near Christchurch). I was posted to Sopley for a 3-week course on the GCI equipment before I was sent overseas.
I was on the tube on one occasion when Cunningham was under our control and I heard him on the radiotelephone responding to the instructions passed by the controller who was sitting beside me. Cunningham's call-sign was 'Blazer 24' and the conversation was limited to codenames like 'Angels two five' (for height 25000 ft), 'Vector 290' (course 290 degrees) and 'Buster, Buster' meaning 'go full out, you're almost up to him', before handing over the control to the pilot.'
All of this must have given Sydney a severe adrenaline rush, with life after the war surely seeming quite boring.
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