Kehl-Strasbourg radio control link

The Kehl-Straßburg radio control link was a German MCLOS radio control system of World War II. The system was named for Kehl, at the time a suburb of Strasbourg, and Strasbourg, the French/German city on the Rhine. It was used by the Fritz X guided bomb and the Henschel Hs 293 guided missile.

The Kehl-Straßburg system combined two units. The dual-axis, single-joystick-equipped Funkgerät (FuG 203) Kehl series of radio-control transmitter sets, fitted aboard the launch aircraft, were used to send the control signals to the ordnance, with the ordnance device itself picking up the signals through a Funkgerät (FuG 230) Straßburg receiver after release. The generic term Funkgerät, the source for the FuG prefix, translates directly into "radio equipment" in English, and also prefixed the designations of other various types of German military electronics, like the Lichtenstein airborne intercept radar series, and the Erstling IFF radio gear, among others.

The Kehl-Straßburg control link relied on radio contact between the bomb or missile and the guidance unit. As a result, it was highly susceptible to electronic countermeasures. After the initial attacks in August 1943 the Allies went to considerable effort to develop devices which jammed the 48.2 MHz to 49.9 MHz low-VHF band radio link between the Kehl transmitter aboard the launching aircraft and the Straßburg receiver embedded in either the Hs 293 or the Fritz X ordnance. Early efforts by the U.S. Naval Research Laboratory (NRL) produced the XCJ jamming transmitter, installed aboard the destroyer escorts USS Herbert C. Jones and Frederick C. Davis in late September 1943. The XCJ was ineffective because the frequencies selected for jamming were incorrect. This was updated in time for Operation Shingle, leading to the XCJ-1, which was installed aboard destroyer escorts Frederick C. Davis and Herbert C. Jones, as well as destroyers Woolsey, Madison, Hilary P. Jones, and Lansdale. These six ships rotated service at Anzio, with three deployed at any time. The manually operated jamming system met with some success, though it proved cumbersome and was easily overwhelmed if large numbers of weapons were deployed simultaneously.

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