Electronic Warfare (Measure-Counter Measure)

This Me110G-4 mounts the huge ‘stag-antler’ antennae of the metre-wave Lichtenstein SN-2. However, the small aerial cluster in the centre of the nose gives away that this aircraft is equipped with the SN-2b radar. These early SN-2 sets had a very large minimum range, and so a second radar set from a Lichtenstein C-1 was installed to cover this dead zone. The resulting installation was draggy and caused a loss of aircraft performance. Worse still, the Funker (or radar operator) was forced to use two separate radar sets simultaneously. The later SN-2c had a short enough minimum range that it could drop the C-1 set.

In 1937 a British research scientist, R.V. Jones, first noticed that a strip of aluminium foil drifting through the air produces a blip on radar screens. 2,000 of these strips, 11/2 ft high and 1 inch wide, shows up on radar screens very similar to a British heavy bomber. In the summer of 1941 a RAF Wellington bomber fitted with special radio aerials (antenna whips) found it received a lot of attention by German gunners even when it was flying among other planes. It was deduced that the radio aerials created a larger radar echo of the bomber than would be the case otherwise, thereby drawing more enemy fire. During the next air raid this bomber participated in, against Benghazi in Libya, the crew dropped packets of aluminium strips 18 inches long and 1.5 inches wide (the size of the special aerials) but no change was observed. One more time the aluminium strips were used but with no useful results the whole idea was abandoned.

A year later and after many experiments it was found that a bundle of 240 aluminium strips produced a radar echo similar to a RAF Blenheim bomber. Ten such bundles released over a mile made it nearly impossible for radar to pick out the real bomber‘s echo. First used operationally in a series of four major raids by bomber Command against Hamburg July 24 – August 2, 1943. On the first night alone 92 million strips of Window were released (about 40 tons) from 746 RAF bombers. The German radar operators were totally confused because the Window cloud showed up on their screens as thousands of aircraft. Accurate pinpointing of the invading bombers was therefore impossible so that, on that night, the German night defences were rendered completely ineffective. The new weapon spelled the end of the Himmelbett system because, with both the flak and night fighter arms denied radar back-up they had to rely upon random pick-ups by the similarly handicapped searchlights successfully confusing the German defenses. From this point forward Window was used on every air raid and in many of the numerous spoofing raids to deceive the German defenses.

Window was aluminium foil stiffened with a black paper backing and cut into strips 30 cm long and 1.5 cm in width. The silvery side was coated with lampblack, a fine soot collected from incompletely burned creosote or kerosene, so the clouds of Window would not show up in the glare of search lights. At first window was released from the aircraft by any convenient opening but soon each Lancaster was fitted with a louvered box structure on the lower starboard side of the nose. From here Window was released by the Flight Engineer or the bombs Aimer.

The AAF called window “chaff” because of the way it resembled wheat chaff in the wind. First use by 8th Air Force was in December of 1943 and for the 15th Air Force March of 1944.

By 1944 every AAF bomber in the lead wing carried 144 packages of chaff. These were dropped at four second intervals, so each plane could lay a chaff lane or “corridor” 20 miles long.


The Germans’ Freya early warning radars were reinforced by the introduction of the Wassermann (Aquarius) and Mammut (Mammoth) long distance radars which could plot bombers above the radar ‘horizon’ as far north as Norfolk and Suffolk, but these could be jammed by the British airborne Mandrel device.

To counter Freya, the British used equipment called ‘Moonshine’. Carried by Boulton Paul Defiant aircraft of the Special Duties Flight (later No. 515 Squadron RAF), a single set retransmitted a portion of the Freya signal amplifying the apparent return. Eight planes with ‘Moonshine’ could mimic a force of 100 bombers

Bombers could also detect when they were being monitored by the German Würzburg gun-laying radar with a device called Boozer.

Measure Counter-Measure

June 1940 Wurzburg 25 mile range radar, mainly used in AAA aiming could judge altitude
Sept 1940 Freya 75 mile range radar for early warning of approaching aircraft, could not judge altitude
October 40 Wurzburg Used in pairs. One tracks the bomber, the other an interceptor which is vectored to the target
Sept 1941 Wurzburg Riese Giant version of Wurzburg, range over 40 miles
Feb 1942 Lichtenstein Radar Airborne radar range 2 miles to 200 yards
March 42 Mammut Improved Freya early warning radar, 200 mile range. cant measure altitude
March 42 Wassermann Early warning radar 150 mile range, could judge altitude
March 42 Gee Navigation aid for British bombers accuracy to within 6 mi at 400 mile range
June Shaker Lead bomber aircraft blind dropped marker bombs with Gee for following bombers
August Moonshine Device that greatly amplified Freya radar pulses, giving impression of larger force. Used in Defiants. Used until October 1942
August Heinrich Transmitters that jammed the Gee ground transmitters. Gee became unusable by Nov 42
Nov Mandrel Noise based jammer, mainly against Freya radar put in planes flying ahead of and with bombers
Nov Tinsel Device which Amplified engine noise to disrupt ground-to-air communications
Dec Oboe 270 mi range accurate blind bombing system used in pathfinders. US bombers first use 10/43
Jan 1943 H2S Powerful centrimetric radar which gave rough representation of terrain on CRT screen in bomber. Water vs. land is easily seen. Also cities vs. open countryside. Not fully effective till June 1943. First American use Nov 1943
March Monica Radar transmitter in tail of bombers range 1000 yards. No IFF. to give warning of approaching
March Boozer Radar receiver which gave visual warning if aircraft detected by Wursburg/Lichtenstein radar
June A1 Mk X Centriimetric airborne radar. British version of U.S. SCR720
June Serrate Radar receiver for nightfighter which picked up Lichtenstein giving visual cues of height and direction
July Window Bundles of metal foil, confuse Wurzburg/Lichtenstein radars
Aug Special Tinsel Update to Tinsel to jam new High Frequency German transmitters
September Naxburg Modified Wurzburg which could pick up H2S signals. Could pick up individual aircraft 150 mi
Oct ABC ‘Airborne Cigar’ airborne transmitter to jam German fighters VHF radiospar
Oct Corona Special Tinsel transmitters to send out false instructions to German fighter pilots
Oct SN-2 Airborne radar impervious to Window. range 4 mile to 400 yards
Nov Wurzlaus Modification to Wurzburg which under favorable conditions could differentiate between moving bombers and relatively motionless chaff (Window)
Nov Nurnberg Modification to Wurzburg allowing skilled operator to distinguish between pulse from bomber or a pulse from chaff
Nov Flensburg Airborne receiver which picked up Monica transmissions
December Dartboard Jamming of Stuttgart radio station which was giving musical coded instructions to nightfighters
Jan 1944 Drumstick Ground transmitters sending meaningless Morse code signals to disrupt German Morse ground to air
Jan Oboe Oboe converted to centrimetric wavelength
Jan Naxos Airborne receiver which picked up HsS signals
April 44 Jagdschloss Ground radar range 90 miles working on four separate frequencies
April Egon Ground to air fighter guidance system. Range 125 mi
August Jostle IV Improved ABC blots out whole range of frequencies at a time instead of one at a time
September Window Window made to block SN-2 radar
Oct Serrate IV Modified Serrate to home in on SN-2 signals
Oct Perfectos Airborne transmitter-receiver which activated German IFF set showing the fighters transmissions a direction and distance to to plane could be found
Oct Piperack Airborne transmitter to jam SN-2
Dec Micro-H American alternative to Gee should later ever be jammed

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