The Raf used different systems. One of these was simply to drop small pieces of aluminium, they would immediately be detected and confuse the German radars. This was calle dwindowing. An other system was THE ABC onboard jamming device used for instance by 101 Squadron. A special operator would jam the German radars and make sure the bober stream was not detected. When the Germans discovered the A channel, the operator had a few seconds to switch to the B or to the C channel.

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