Radar, first known as Radio Direction Finding, worked via a cathode ray tube, rather like a small television screen, on which an impulse or 'blip' appeared when the transmitter sent out a radio signal. A radar station consisted of a pair of tall metal masts, one to transmit and one to receive signals. At the foot of these was a receiver hut housing the cathode ray tubes. If there were no aircraft in the area covered by the signal, the screen showed only one blip. But when an aircraft appeared, the signal bounced off it and was picked up by the station's receiving antennae, which translated it into another blip on the cathode ray tube.
Radar masts, 110m/360ft high, carried fixed transmitting aerials which gave 'floodlight' cover at Chain Home long range warning stations.
Operators were then able to calculate the range and bearing of the approaching aircraft by the time that elapsed between the signal being transmitted and received. RAF aircraft were fitted with 'friendly' recognition signals, so radar operators could distinguish between them and the enemy. A system of base to fighter control had also been worked out that gave the RAF a tactical advantage over the Luftwaffe. Two types of radar were operating during the Battle of Britain. Chain Home, or high-level radar, had a range of around 160km/100mls and could detect aircraft below 15,000ft. Chain Home Low sets were amazingly accurate at up to 48km/30mls in detecting low-flying aircraft.
When aircraft were picked up on a radar screen, a warning was flashed to Fighter Command Headquarters (FCH) at Bentley Priory, which in turn alerted the Fighter Group protecting the predicted target area. The Group Operations Room decided how many aircraft were needed to respond to the coming attack, ordered fighters to stand by to 'scramble', then handed over the direction of the interception to Sector Airfield Control. This was in radio contact with the pilots and guided them toward the enemy with coded messages. The early warning and other target information was also given to anti-aircraft batteries in the path of the Luftwaffe formation.
Plotters in Operations Rooms moved red and black counters (for enemy and friendly aircraft), marked with figures showing estimated height and strength, on map tables. The coloured direction arrow of each raid was changed to match differently coloured five-minute segments on a special clock as reports were updated. Information was then passed to Sector Controllers who scrambled the aircraft needed to deal with the enemy.
The position of the closing enemy aircraft was constantly updated by the radar stations and fed along the chain of command to the airborne fighters. Once intruders had crossed the coast, the radar stations, which operated only to seaward, could not track them. The task of following their progress then fell to Observer Corps watching posts, whose crews passed on their sightings to the Filter Room at FCB. All this data, combined with radio reports to base from the aircraft once they were airborne, enabled the RAF to plot the development and course of every attack. This was done by moving symbols on large scale table maps in operations rooms from FCH down to sector airfield level.
Hawker Hurricanes of 501 Squadron, County of Gloucester, take off to intercept attacking German aircraft on 16th August 1940.
07-06-2008, 10:19 PM
