FuG 240 Berlin

The FuG 240 "Berlin" was an airborne interception radar which the German Luftwaffe introduced at the very end of World War II. It was the first German radar to be based on the cavity magnetron, which eliminated the need for the large multiple dipole-based antenna arrays seen on earlier radars, thereby greatly increasing the performance of the night fighters. Introduced by Telefunken in April 1945, only about 25 units saw service.

The German Luftwaffe first introduced an airborne interception radar in 1942, the FuG 202 "Lichtenstein B/C" and its direct follow-on version, the FuG 212 Lichtenstein C-1. Both units operated at 490MHz, in the low UHF band with a wavelength of 0.61 meter. Radar antennas are sized roughly to the operational wavelength, or a fraction thereof, so the FuG 202 and 212 required large, 32-dipole Matratze (mattress) antenna arrays that projected in front of the aircraft and caused considerable drag.

By 1943 a series of efforts and lucky intercepts had allowed the Royal Air Force to introduce jammers, which interfered with the AI radar's operation. The RAF also introduced the Serrate radar detector, which allowed British night fighters to home in on the Lichtenstein radars. Over the summer and fall of 1943, the RAF downed an impressive number of German night fighters.

The Luftwaffe responded by introducing the FuG 220 Lichtenstein SN-2 in late 1943. To avoid RAF jamming, the SN-2 operated in the low-VHF range, at 90MHz, or 3.33 meter wavelength. The SN-2's lower frequency range required enormous eight-dipole Hirschgeweih (stag's antlers) antennas, which created so much drag that aircraft were slowed by some 50 km/hour.

The Lichtenstein SN-2 was eventually supplanted by the Neptun radar. Based on the same basic technology as the Lichtenstein, the Neptun operated on six mid-VHF frequencies between 158-187MHz. with shorter dipole antennas, still in the "antler" mounting format. This unit was only a stop-gap solution.

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