Lichtenstein (radar)

Lichtenstein FuG 202 Viestimuseo 2.JPG display: FuG 220 and FuG 202 radar of Me 110 1945.jpg [[Image:ME-110G-2 at RAF Hendon.jpg|thumb|A [[Messerschmitt Bf 110|Bf 110 G-4]] in the RAF Museum in Hendon, with second generation FuG 220 Hirschgeweih antennas, without the short-range FuG 202]]
 * The left tube indicated other aircraft ahead as bumps.
 * The centre tube indicated range to a specific target and whether they were higher or lower.
 * The right tube indicated whether the target was to left or right.]]

The Lichtenstein radar was among the earliest airborne radars available to the Luftwaffe in World War II. Developed by Telefunken, it was available in at least four major revisions, designated FuG 202 Lichtenstein B/C, FuG 212 Lichtenstein C-1, FuG 220 Lichtenstein SN-2 and FuG 228 Lichtenstein SN-3. (FuG is short for Funk-Gerät, German "radio set"). The Lichtenstein series remained the only widely deployed airborne interception radar used by the Germans during the war, the microwave-based FuG 240 "Berlin" was still in testing when the war ended.

FuG 202 Lichtenstein B/C
Early FuG 202 Lichtenstein B/C units were not deployed until 1942. They operated at a maximum RF output power of 1.5 kW, on the 75 cm wavelength (490 MHz, or low UHF band), requiring complex Matratze (mattress) antennas, consisting of a total of thirty-two dipole elements, mounted in four groups of eight, each at the forward end of one of four forward-projecting masts.

FuG 212 Lichtenstein C-1
During 1943 the Lichtenstein B/C was improved as the FuG 212 Lichtenstein C-1, with longer range and wider angle of view, still operating at UHF Frequencies between 420 and 480 MHz and still using the complex Matratze aerial set. By this point in the war, the British had become experts on jamming German radars. The Luftwaffe flightcrew of a B/C-equipped Ju 88 R-1 night fighter, Werknummer 360 043, defected in April 1943 and landed in Scotland, presenting a working example of the German radar for the first time, with the aircraft itself, still in existence as of the 21st century, becoming a museum exhibit in the UK. The subsequent refinement of 'Window' (known as Düppel by the Luftwaffe, from the Berlin suburb it was first found near) rendered Lichtenstein B/C almost useless for several crucial weeks.

FuG 220 Lichtenstein SN-2
By late 1943, the Luftwaffe was starting to deploy the greatly improved FuG 220 Lichtenstein SN-2, operating on a longer-wavelength of 90 MHz (lower end of the US VHF FM broadcast band) frequency which was far less affected by electronic jamming, but this required the much larger Hirschgeweih (stag's antlers) antennas, with only eight dipole elements, looking like a much-enlarged version of what occupied the forward end of each one of the earlier quadruple Matratze masts. This aerial setup also produced tremendous drag and slowed the operating aircraft by up to 50 km/h (30 mph). The first SN-2 set had a problem with a huge minimum range of 500 meters, initially requiring the retention of a supplementary B/C or C-1 set with its full set of four Matratze masts, but the alarming drag that full sets of both types of antennas caused, from both radars being installed, later changed the requirement to only a "one-quarter" subset of the earlier Matratze array at the end of a single mast, centrally mounted on the nose of the aircraft when the BC or C-1 UHF radar remained installed. Improvements in spring 1944 led to newer SN-2 versions with lower minimum range, which allowed the older UHF radar system to be removed entirely. In July 1944, the newest version of the SN-2 radar fell into Allied hands when a fully equipped Ju 88 G-1, of 7 Staffel/NJG 2, flew the wrong way on a landing beacon and landed in England by accident, with the crew not realising the mistake until it was too late to destroy the radar or IFF gear. This led to successful jamming of several frequency bands of the FuG 220 (I to III, 72, 81 and 90 MHz), and a partial adoption of the use of the low-to-mid VHF band FuG 216 and 217 Neptun radar set, but several other bands that the SN-2 used were still operational. After the Allied jammings the FuG 220 antenna setup was optimized for the still operational bands, the 90-degree vertical dipole setup was changed to a 45-degree diagonal setup.

Late-war developments
Late in 1944, the Morgenstern (Morningstar) antenna, comprising a doubled set of two Yagi antenna arrays at 90° angles to each other, on a central, forward projecting mast was developed, and used by both the SN-2 and Neptun radar sets. This was just compact enough to fit into the nose of a Ju 88G, and was covered with a rubber-coated, wooden conical radome with the extreme tip of each element barely protruding above the surface. Further development led to the FuG 228 Lichtenstein SN-3 radar set but this saw little to no service.

A 9 cm wavelength system known as FuG 240 Berlin was developed, based on captured examples of the Allies' cavity magnetron technology but saw little to no operational use.

Allied countermeasures
The Allies were able to jam and track the early FuG 202 and 212 sets by Summer 1943. During several months in this period they rendered these sets almost useless by blinding them with 'Window', known as Düppel to the Germans of World War II, and today known as Chaff. Fully jamming the SN-2 took longer but was probably accomplished by the Allies following the mistaken landing of a Ju 88G-1 night fighter from NJG 2 at RAF Woodbridge, equipped with both the Flensburg radar detector and the SN-2 radar on July 13, 1944, compromising both systems to the Allies. Much more dangerous were Mosquito intruders equipped with a device called Serrate to allow them to track German night fighters by emissions from their Lichtenstein B/C, C-1 or SN-2 sets.

An aerial maneuver known as the 'corkscrew' was developed to remove an attacked heavy bomber from within the 60-degree cone of coverage of an attacking night fighter's Lichtenstein radar. The technique was developed using the same early model UHF-band Lichtenstein-equipped, Ju 88R-1 night fighter that had landed at RAF Dyce in April 1943 by its defecting crew. It was also later flown in tests by the RAF's enemy aircraft evaluation unit, No. 1426 Flight, known colloquially as the 'Rafwaffe'.