A 22m diameter ring of 1.5m wide concrete with a small concrete recess in the centre is all that remains of one of the largest radio navigation systems installed in Normandy during WW2.
The La Pernelle site, to the north of Utah Beach landing area, was the home to a 28m by 35m antenna – a structure so large and heavy at around 120 tons it required four electric trams running on rails on top of the concrete ring to turn the device.
It was part of the Bernhard system – a rotating-directional ground-beacon of system of radio navigation developed in late 1940 and created to replace the Knickebein system which was jammed and overcome by Allied intelligence almost as quickly as it was introduced.
More than a dozen sites were constructed in the German occupied territories with La Pernelle designated as Bernard-4.
To the Germans, the system was known as FuSAn724 (Funksendeanlage) and the large antenna was a VHF transmitter which would send locational bearing data to radio receivers in night fighter aircraft helping to direct them to intercept Allied bombers.
The antenna, and the large wooden equipment and crew cabin incorporated into the structure, rotated along a set of rails mounted on top of the concrete ring at two revolutions per minute and the signal from it could be received over 300 miles away, depending on the altitude of the aircraft.
The antenna is believed to have been installed here in early 1941, abandoned by the Germans in June 1944 following the Normandy landings, and was ordered to be dismantled by Allied forces the following month.
Today you can see the concrete ring and recess in an overgrown corner of a farm field at the D125/D328 crossroads near to a more modern communication site on the hill inland of the village of La Pernelle.
At the centre you can still see the concrete foundation and steps down to what would have been a flat-roofed, brick built central equipment building which housed a power control panel and emergency shut off, transmitter units, printers similar to those installed in the receiving aircraft, and a slip ring assembly which ensured the electrical lines didn’t twist as the antenna rotated.
The site also included barracks blocks, a generator building and a separate mast which would monitor the output from the main antenna.
For what looks like a simple concrete ring, there’s an incredibly high tech (for the time) background story to the site and is well worth a visit.