The Naval Security Group (NAVSECGRU) worldwide CLASSIC BULLSEYE (now FLAGHOIST) network is part of the DOD Worldwide High Frequency Direction Finding System for strategic intelligence collection and emitter location. High-Frequency Direction-Finding [HF-DF, popularly known as huff-duff] intercepts and locates voice and message traffic transmitted on short-wave channels. HF-DF systems operate at frequencies where the signals are reflected from the earth's ionosphere [skywave signals].
Military - Communications
Links: fas.org
By: kjfitz