This small concrete construction was built for an antenna which formed part of Germany’s Y-Gerat radio guidance system for directing bomber aircraft to their targets.
Y-Gerat was an advancement on the X-Gerat system which had already been rendered useless by Allied countermeasures. It was also known as Wotan or Woden after a one-eyed god which was apt as this was a single-beam navigation system which also included a distance-measurement element.
Y-Gerat used a single, narrow radio beam pointed over the target which was received by a transponder on a lead aircraft and returned back to the ground station. The time taken for the signal to return determined the distance.
Unlike previous navigation systems, German bombers didn’t have to track the signal from the Y-Gerat radio beam. Instead, the guidance was radioed to the pilot from the ground station.
As with previous systems, British intelligence was able to counter the beam, this time thanks to a dormant BBC TV transmitter at Alexandra Palace in north London which coincidentally broadcast at the same 45 MHz frequency as Y-Gerat.
By transmitting signals back to the aircraft, it was able to disrupt the accuracy of the system and as time went on the signal strength was increased to the stage where the whole Y-Gerat system was inoperable due to the high levels of feedback. It was to be German’s final radio guidance system.
Today the transmitter building stands on the edge of a housing estate and is partially buried so the inside cannot be accessed.