You don't hear much about the FCC's monitoring efforts these days, but during World War 2 the United States Federal Communications Commission had two divisions devoted to SIGINT, the Foreign Broadcast Monitoring Service (FBMS) and the Radio Intelligence Division (RID). The mandate of the FBMS was to record, translate, transcribe and analyze shortwave propaganda radio programs that were being beamed at the United States by the Axis powers. Additionally, between 1940–1947, the FCC's Radio Intelligence Division (RID) monitored clandestine radio transmissions in the United States. The RID was the FCC's “largest single activity” during the war years and helped military and government agencies locate the Axis enemy's clandestine radio transmissions. Radio Historian Brian Harrison, KN4R, explores the fascinating history of these two organizations, the equipment that they used, and their contributions toward winning World War 2 in this video from The Antique Wireless Association.
Video starts at about 44 min in. The unending aaah, uuum and so on made the rest unbearable to listen to. Still, worth a look.
