In the early 1960s the U.S. Naval Security Group began deploying a network of large high-frequency direction-finding (HF-DF) circularly disposed antenna arrays, the AN/FRD-10s,....
During the Cold War, the Soviet Union built an extensive network of large circularly disposed antenna arrays (CDAAs) for high-frequency radio direction-finding and monitoring. The largest of these CDAAs were known in the West as the Krugs.
The Northrop Grumman RQ-4 Broad Area Maritime Surveillance (BAMS) will pick up a signals intelligence (sigint) payload and communications relay (comms) payload... Added 08/21/2011
BAE Systems offers tactical signals intelligence (SIGINT) payload for tactical unmanned aerial vehicle applications, which includes battlefield emitter mapping.