High Frequency Global Communications System/Claude Draft

The High Frequency Global Communications System (HFGCS) is the U.S. military's primary HF radio network for broadcasting Emergency Action Messages and providing communications to strategic forces worldwide. It consists of ground stations scattered across the globe, control centers that operate them remotely, and airborne platforms like the E-6B Mercury that can relay messages.

Background

Most explanations of the HFGCS you'll find online are recycling the same information from 15-20 years ago. Larry Van Horn's 2006 writeups remain the foundation for most HFGCS information out there, mainly because he did such a thorough job—but some of it's inevitably gotten outdated since nobody's really picked up where he left off.

The military used to be more open about the HFGCS. The system even had its own public website back in the 1990s, and the Air Force published articles about HFGCS operations through 2006. But they became less forthcoming about it sometime in the mid-2000s.

That said, the HFGCS isn't classified or secret. You can still find mentions of it in news stories and official documentation. In fact, detailed contemporary descriptions come straight from the Department of Defense and are published annually—they're just buried in budget documents running around 1,000 pages. These budget docs are worth reading because some of the information in them is more current than the old stuff still floating around.

How It Works

When people talk about "the HFGCS," they usually mean the network of ground stations that broadcast EAMs and other traffic, provide phone patches, and handle various other communications tasks.

Primary Frequencies

As of January 2024, the primary HFGCS frequencies are:

• 4724 kHz
• 8992 kHz
• 11175 kHz
• 15016 kHz

The ground stations usually simulcast messages on all these frequencies simultaneously, though not always. Sometimes broadcasts are exclusive to just one or some of the frequencies. The HFGCS has historically operated on predetermined schedules, and probably still does.

Control Stations

The ground stations are remotely controlled from Centralized Network Control Stations (CNCS). Andrews AFB is definitely one of them. A 2006 article mentioned that Andrews was expecting to get "another CNCS at Offutt Air Force Base".

Based on listening to the network—like when planes request radio checks and you hear different ground stations respond with different signal reports—there's clearly at least one additional control center. Wikipedia (unsourced) says the second station is Grand Forks AFB, and you can find support for this pretty easily.

Grand Forks isn't Offutt, so something changed along the way. At the very least, Offutt had a major flood that damaged facilities. But it's definitely not the case that Andrews is the only control center.

There's also the question of what RED RIVER and WOLFHOUND are—they kind of sort of act like control stations, but not quite.

Ground Stations

The HFGCS operates a worldwide network of high-power HF transmitter sites. Different sources cite anywhere from 13 to 15 stations, likely reflecting changes over time as stations have been added or decommissioned.

Known HFGCS transmitter sites include:

Active Stations

• Ascension Global - RAF Ascension Island/Ascension Auxiliary Field, Ascension Island (British Overseas Territory)
• Diego Garcia Global - Naval Support Facility Diego Garcia (British Indian Ocean Territory)
• Elmendorf Global - Joint Base Elmendorf-Richardson, Alaska
• Hickam Global - Joint Base Pearl Harbor-Hickam, Hawaii
• MacDill Global - MacDill Air Force Base, Florida
• Sigonella Global - Naval Air Station Sigonella, Sicily, Italy

Additional stations are known to operate from or have operated from locations in:

• Guam
• Puerto Rico
• England (likely RAF Croughton)
• Portugal (likely Lajes Field, Azores)
• Japan
• Nebraska (possibly Offutt AFB)
• Maryland (possibly Andrews AFB or Fort Meade)

Former Stations

• Keflavík Global - Former Naval Air Station Keflavík, Iceland (closed 2006)
• Loring Global - Former Loring Air Force Base, Maine (closed 1994)

Station Architecture

Each HFGCS station consists of three sites: transmitter, receiver, and control infrastructure. The stations are equipped with different radio systems depending on when they were installed:

• Scope Pattern (1960s-1970s) - 3 kW
• Scope Control (1960s-1970s) - 10 kW
• Scope Signal III (1980s) - 10 kW
• Scope Command (1990s) - 4 kW

The actual number and exact locations of all active stations aren't comprehensively documented in public sources, which is part of why older lists keep getting recycled.

See Also

• Emergency Action Message
• E-6B Mercury
• Larry Van Horn