The RAF pioneered the creation of a squadrons and aircraft that had a dedicated ELINT function. Y-Service, the RAF signals intelligence unit began employing ELINT aircraft in 1940 using Anson and later Wellington bombers to plot out the Knickebein beams used by the Luftwaffe for guided night bombing. The German's use of radar bomber offensive over Europe underscored the need for a dedicated ELINT aircraft unit and in January 1943, 192 Squadron was established with a mixture of Wellingtons, Hallifaxes, and Mosquitoes. Generally, 192 and other ELINT units preferred large bombers like the Halifax for ELINT work as their was sufficient space in the fuselage to accommodate the bulky equipment. Later in the war, surplus B-17s and B-24 became available and supplemented the ELINT aircraft. The pioneering work by 192 allowed for the USAAF to develop its own ELINT aircraft, modifying B-24 and P-38 droopsnoots to supplement the 8th Air Force's jamming units.

One of 192 Squadron's basic missions was to plot out the Luftwaffe's radar network on the continent. The aircraft carried paper and wire sound recording devices like Bagful and Blonde that could pick up the radar frequencies and their duration. This allowed the RAF to keep abreast of German radar developments and the location of its radar stations. These missions also overlapped with spoof raids in which not only would the aircraft record German radar network, but also give false signals to confuse the Luftwaffe's defense network in advance of major raids. The ELINT work done by 192 and other units of 100 Group proved to be quite valuable for wider military operations beyond the bomber offensive. The ELINT aircraft flew patrols over the North Sea, the Channel, and the Bay of Biscay to determine the scale and type of Fortress Europe's radar network in advance of Overlord. This allowed the Allies to develop effective countermeasures to prevent German radar stations from picking up the Allied invasion armada.

Although RAF jamming efforts never fully negated the German radar stations, the ELINT aircraft employed by units like 192 kept the technological edge over the Germans in the radar war. The result was there were relatively few electronic surprises that the Germans had during the course of the war. This is not to say that Allied ELINT was infallible. One of its blind alleys was the Big Ben jamming operations in which ELINT aircraft chased after the nonexistent radio control of the V-2s. Two-seater P-38s on loan from the USAAF's 7th Photographic Group engaged in Ferret operations over the Low Countries to locate and jam these alleged radio signals. Although the Big Ben missions were doomed to failure, they did uncover new developments in the German radar system as the Germans tried to rebuild their network after the Allied invasion had disabled their French-based stations. Although number of dedicated ELINT aircraft was relatively small compared to other electronic warfare units, their impact upon the electronics war was much greater than their numbers would suggest.

Sources

Bowman, Martin W. 100 Group (Bomber Support): RAF Bomber Command in World War II. Barnsley: Pen & Sword, 2006.

Lake, Jon. Halifax Squadrons of World War 2. Oxford: Osprey Aviation, 1999.

Streetly, Martin. Confound and Destroy: 100 Group and the Bomber Support Campaign. London: Macdonald and Jane's, 1978.