[2016]

In 1950 the West Berlin authorities began dumping debris from wartime bombing in the Grunewald, in the British sector. The rubble pile was known as the Teufelsberg and it soon became the highest point in the city with a summit about 400 feet above sea level. From the early 1960s this man-made hill hosted a joint British and American Sigint site which operated until the end of the Cold War. I was involved at one stage in planning this site, and offer here some recollections of the experience.

Why were important Sigint resources located in West Berlin, in the middle of the deployed Soviet and East German armies and air forces, and why in particular were they placed on a rubble pile? The answer lay in the physics of radio transmissions. Radio waves travel in straight lines and do not bend around the earth's circumference, or not much. At some frequencies they bounce off layers of the ionosphere between 75 and 250 miles above the earth, and thus are suitable for long-distance communication. Many of our Soviet targets in the Cold War were of this kind: high frequency (HF) transmissions which could be effectively intercepted at ranges of some hundreds of miles. Other targets operated differently, using higher frequencies which did not have this ionospheric effect; instead they transmitted over a limited range, akin to those of personal VHF radios. This second category included Soviet radio-relay systems, radars and other Elint emissions, battlefield radio and airground plain language. For all of these targets the interceptor had to get close, ideally within line of sight of the transmitters, with audibility increased by the height of the target, the intercept site, or both. Our Sigint targets in Germany were a mixture of those which needed this type of close access (particularly air-ground voice) and those in the HF range, which were interceptable over longer distances. Many other factors influenced the location and tasking of the British Sigint stations, but all depended on the audibility of their targets.

Radio interception of both kinds had provided Allied commanders with tactical intelligence in the wartime re-conquest of Europe, and after 1945 the British Sigint units in occupied Germany were deployed to provide similar coverage of the Soviet and Warsaw Pact forces confronting them across the East–West border.