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for most HFGCS information out there, mainly because he did such a thorough job—but some of it's inevitably gotten outdated since nobody's really picked up where he left off.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. A 2023 Air Force contract for antenna maintenance work listed specific locations for HFGCS stations, providing the most detailed contemporary picture of the network.

Active Stations

Based on the 2023 contract, HFGCS stations operate at the following locations:

Maryland

• Joint Base Andrews (Davidsonville and Brandywine sites)

Alaska

• Joint Base Elmendorf-Richardson

Pacific

• Guam - Barrigada and Finegayan
• Hawaii - Lualualei and Wahiawa

Atlantic/Indian Ocean

• Ascension Island Auxiliary Field
• Diego Garcia
• Lajes Field, Azores (Cinco Picos and Villa Nova sites)

Continental United States

• Offutt Air Force Base, Nebraska (Elkhorn and Scribner sites)
• Dixon, California
• Lincoln, California

Caribbean

• Puerto Rico - Isabella and Salinas

Europe

• Naval Air Station Sigonella, Sicily, Italy

Japan

• Yokota Air Base (Tokorozawa and Owada sites)

The network appears to consist of approximately 13-15 main stations, with many stations having multiple transmitter and receiver sites. For example, both Andrews and Offutt have two separate antenna sites listed, and Guam, Hawaii, Lajes, Puerto Rico, and Yokota each have two sites.

Former Stations

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

Notably, RAF Croughton in England—often cited in older sources as an HFGCS station—does not appear in the 2023 contract locations, suggesting it may no longer be active or may have a different role in the network.

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 2023 contract for "High Frequency Global Communications System – Antenna Program Support III" was awarded to Long Wave Inc. for $112.6 million and covers program depot maintenance and installation activities for high-power HF antennas and antenna subsystems through September 2030.

See Also

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