Located at Beaumont la Hague on the north west of the Cotentin peninsula, this site was one of six early radio guidance sites built in France to support bombing raids on England.
In order to improve the accuracy of night-time or low visibility bombing raids, German forces developed a system known as Knickebein – their first-ever radio guidance system – which broadcast medium frequency radio beams from large antennas based at strategic locations.
Knickebein translates to ‘bent leg’ or ‘crooked leg’ and refers to the dog-leg shape of the FuSan 721 antenna used to broadcast the radio beams.
The beams were based on morse code and were a series of dots and dashes which could be detected by a lead aircraft in a bombing raid. If the aircraft detected dots or dashes, they knew they were off target to the left or right and it was only when the radio operator/navigator onboard heard a single tone that they knew they were in direct line of flight to their objective.
A third beam would also be broadcast to enable the aircraft to determine the range to their target and it’s believed the system enabled the bombers to deliver their payloads within a 1.5km radius of accuracy – far better than previous unguided raids.
By June 1940, British intelligence services had detected the broadcasts and were able to jam the signals destroying the accuracy of raids, leading the Germans to develop more precise and robust systems including the X-Gerat and later Y-Gerat guidance systems.
The Luftwaffe-run facility at Beaumont Hague – known as site K9 - featured a FuSan 721 type antenna mounted on a 10m diameter circular track plus a crew bunker and large generator building. The track outline can still be seen today in an agricultural field, but the generator building has been overtaken by local industry and is no longer accessible.
The other five sites in France can be found near Sortosville-en-Beaumont, Caen, Dieppe, Brittany, and Boulogne-sur-Mer with other Knickebein stations in The Netherlands, Germany, Italy, and Norway.