Originally Posted by
ORAC
Yep, the Trimingham Car Killer. The radar had a bunch of duff phase shifters on the Antenna. These were used to set the initial angle that the radio energy left the antenna (the radar used a frequency modulated pulse that changed the angle of the beam from low down to high up during the duration of the pulse, which was tens of microseconds long. Basically this was the same as light refracting through a change in medium, change the wavelength (colour) leads to a change in angle). When the radar had the high power option fitted to it (removed sometime between 2001 and 2004) There had been a six monthly check of the Antenna with a thermal imaging camera. If any of the phase shifters were unserviceable, they got very hot and this could be seen on the photo. They would then have to be replaced. The Engineering Authority though in low power mode, the phase shifters would never fail, so the camera check was removed from the scheduled maintenance. Because a lot of the phase shifters were not working correctly, a lot of energy was going into the ground instead of into the air.