Radio
EAM & HFGCS field guide
A source-based guide to military Emergency Action Messages, the global HF network, and what public reception logs can establish.
What the name means
The Air Force’s published command-and-control manual describes EAMs as messages carrying significant directives from commanders to their forces. The name alone does not reveal the directive, and a public listener does not hold the intended recipient’s authentication or message material.
HFGCS is a U.S. military HF network with international reach. Its published services include message relay, phone patches, broadcasts, emergency assistance, and other communications. Hearing the network does not mean every transmission is an EAM.
Published voice-channel reference
These are the public reference values in the March 2018 DoD Flight Information Handbook, not a claim of current operational allocation or reception. The independent archive currently copies 11,175 kHz USB. Propagation, receiver availability and local conditions affect what can be heard.
Archived DoD handbook · HFGCS section ↗Read the record, keep the uncertainty
A machine copy can miss characters. A listener correction is still a transcription, rather than an official release. “Partial” and “unconfirmed” entries remain visibly marked. Voice-onset times and recording-start times are distinguished; the latter may include pre-roll.
Retries and multiple receiving stations can produce repeated receptions of the same transmission. An outage or an empty archive is not evidence that the network was silent. This desk does not assign threat scores, decode directives, or infer targets.