From Drake Panzer

The High Frequency Global Communications System (HFGCS) is a vital command and control network used by the United States Air Force to send instructions to operations across the world. Traffic is relayed across the world by a network of transmitters linked by satellites and landlines.

HFGCS traffic is unencrypted (although the messages are coded) which means anyone can listen in. It's really cool to peek into the highly-classified world of the United States.

What are they sending?

HFGCS frequencies are used for Emergency Action Messages (EAM) and Skyking messages. Both message types are spoken by a live operator and probably use something like a One-time Pad to encrypt the message data.

One-time Pads work something like this:

  1. A short coded message is broadcasted on a certain radio frequency
  2. The agent or asset listens to the broadcast and writes down the message
  3. The agent or asset decodes the message using a One-time Pad given to them prior

While we can't decode the messages or know the recipients, we can tell if something interesting is going on if there's a lot of traffic. A spike in traffic means something is happening or is going to happen.

Types of Messages

Emergency Action Messages (EAM)

A vital method of giving orders all United States nuclear-capable forces at once. Probably used to order a nuclear strike and coordinate nuclear-capable forces.

EAM messages are usually in this format:

  1. A 5-digit code, repeated five times
  2. The message is read


A higher priority message that can interrupt an ongoing EAM. Skyking messages are intended for recipients similar to EAM messages. The main difference between Skyking and EAM is that Skyking is for messages that are time-sensitive and higher priority than EAM. Nicknamed "Foxtrot Broadcasts".

Skyking messages are a lot shorter than an EAM.

Skying messages are usually in this format:

  1. Skyking, Skyking. Do not answer: [CODE WORD] Time [MM] Authentication [XX]
  2. Message is repeated
  3. Callsign of the sender is given
  4. Operator signs off

Other Uses

HFGCS is also used for high-priority unclassified general aircraft operations. HFGCS can also broadcast a phone call from a ground stations.

On September 11, 2001, at 10:52 am an Emergency Action Message was sent to the military ordering DEFCON level 3.

HFGCS Frequencies

Frequency Comments
8992.00 kHz USB EAM 24/7
11175.00 kHz USB EAM 24/7
15016.00 kHz USB EAM Day
13200.00 kHz USB EAM Day
4724.00 kHz USB EAM Night
6739.00 kHz USB EAM Night

Listening to Skyking


CountyComm GP-5 SSB


Further Reading