High Frequency Global Communications System

The High Frequency Global Communications System (HFGCS) is the U.S. Department of Defense's single global, strategic, high-power HF Nuclear Command, Control and Communications (NC3) and non-nuclear Command and Control (C2) network. It provides rapid, reliable communications to the President and Secretary of Defense, DOD agencies, and allied users equipped with HF radio technology worldwide.

The system consists of 13-15 ground stations strategically located around the world, two network control stations, airborne relay platforms like the E-6B Mercury, and extensive antenna infrastructure. HFGCS is USSTRATCOM's primary strategic HF pre-attack NC3 dependency system, providing broadcasts to global strategic forces and serving as a critical beyond-line-of-sight communications system in satellite-challenged environments.

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for most HFGCS information out there, mainly because he did such a thorough job—but some of it's inevitably gotten outdated since nobody's really picked up where he left off.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 2009. But they became less forthcoming about it sometime in the late 2000s.

That said, the HFGCS isn't classified or secret. It's described as a "24-hour/7-day nonsecure network", though it does support secure communications via NSA Type 1 encryption using the KIV-7. 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.

Operations

The HFGCS operates as a 24/7/365 nonsecure network with encryption capabilities, providing rapid, reliable, non-dedicated communications support to the President and Secretary of Defense, DoD agencies, and aircraft and ships of the United States government during peacetime, contingency operations, and war. The system is not dedicated to any service or command, but supports all DoD authorized users on a traffic precedence/priority basis.

HFGCS is USSTRATCOM's primary strategic HF pre-attack NC3 dependency system, providing broadcasts to global strategic forces. The system supports war plan dissemination and daily operational requirements for USSTRATCOM, WHCA, Joint Chiefs of Staff (JCS), National Military Command Center's Emergency Action Message distribution, Special Air Mission communications, Major Air Force Commands and Combatant Commanders.

Services Provided

HFGCS provides a wide range of communications services:

• General phone patch and message relay services
• Automatic Link Establishment (ALE)
• HF data support, including access to AUTODIN/NOVA and SACCS
• Command and control mission following
• Emergency assistance (distress and urgency situations)
• Emergency Action Message broadcasts
• HF direction finding assistance
• Air traffic control support
• E-mail connectivity to NIPRNeT and SIPRNeT
• Secure calls via dedicated circuits

Phone patch service allows direct voice communications between ground agencies and aircraft by electronically connecting telephone circuits to radio transmitters and receivers. Message relay service enables HFGCS operators to transcribe encoded or plain-text messages for aircraft or ground stations and forward them to addressees by radio or landline.

Supported Commands and Agencies

The system supports aircrews, ground forces, naval operations (USN and USCG), and control stations. HFGCS is the primary HF C2 resource for Air Mobility Command cargo and tanker aircraft. Major users include:

• U.S. Strategic Command (USSTRATCOM)
• Joint Chiefs of Staff (JCS) and National Military Command Center
• Air Mobility Command (AMC)
• Air Combat Command (ACC)
• Pacific Air Forces (PACAF)
• United States Air Forces in Europe (USAFE)
• Air Force Space Command (AFSPC)
• Air Force Materiel Command (AFMC)
• Air Force Intelligence, Surveillance and Reconnaissance Agency
• White House Communications Agency (WHCA)
• Department of Homeland Security
• Federal Emergency Management Agency (FEMA)
• Transportation Security Administration
• State Department
• Civil Air Patrol
• NASA
• Allied coalition forces and other aircraft as appropriate

The HFGCS also provides Defense Communications System (DCS) HF Entry services for tactical units in areas where DCS connectivity is unavailable or insufficient.

Each HFGCS ground station provides coverage over approximately 6,000 square miles. When a station is experiencing technical difficulties or undergoing maintenance, other stations can seamlessly assume its coverage area.

Historical Operations

In the 1990s, the HFGCS supported a mission called SITFAA (Sistema Interamericano de Telecomunicaciones de la Fuerza Aérea Americana), described as a Spanish/English/Portuguese language network supporting North, Central, and South American Air Force users in 18 countries with voice and data HF links. This mission does not appear in documentation from the 2000s onward and its current status is unknown.

Use by Other Networks

While HFGCS operates as an independent network under Air Force control, its ground station infrastructure is also utilized by other communications systems:

• MYSTIC STAR - A separate worldwide communications system operated by the U.S. Army, Navy, and Air Force under DISA Operations Center control. MYSTIC STAR provides HF and satellite communications for the President, Vice President, Cabinet members, and other senior officials aboard Special Air Mission aircraft by directly controlling radio equipment located at HFGCS ground stations.

This shared infrastructure allows multiple critical communications networks to leverage the same worldwide HF transmission capability without requiring duplicate ground stations.

How It Works

The HFGCS operates as a 24/7/365 nonsecure network with encryption capabilities. The system utilizes HF radio technology in the 2-30 MHz operational frequency band, which can penetrate oceans, pass through hurricane walls, and extend signals to the surface of the moon. This makes HFGCS the primary means of communication for U.S. contingencies in severely degraded and hostile environments, and a key beyond-line-of-sight communications component in satellite-challenged environments.

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. Each station includes transmitters, receivers, control systems, intersite communications equipment, and antenna infrastructure.

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 24/7 from Centralized Network Control Stations (CNCS). Radio operators at the CNCS use position consoles to individually control each remote HF global station. This means an operator at Andrews or Grand Forks can control any of the worldwide ground stations—for example, remotely operating the transmitters and receivers at Yokota, Diego Garcia, or any other site.

The two CNCS locations are:

• Joint Base Andrews, Maryland - Primary control station, operated by the 789th Communications Squadron.

• Grand Forks Air Force Base, North Dakota - The second control station, operated by the 319th Communications Squadron under the 319th Reconnaissance Wing. A 2016 government contract confirms that ground stations "are remotely controlled and operated 24 hours a day, 7 days a week by radio operators from two net control stations (NCS) located at Andrews AFB, MD and Grand Forks AFB, ND".

The original plan in the mid-2000s was to establish the second CNCS at Offutt Air Force Base, Nebraska. However, by 2016 Grand Forks Air Force Base had become the operational second control station. Offutt may still maintain some backup or alternate capability, though its exact current role is unclear from available documentation.

There's also the question of what RED RIVER and WOLFHOUND are—they kind of sort of act like control stations, but not quite. 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 from the early 2020s cite between 13-15 ground stations. Current operational information comes from multiple sources including a 2023 Air Force antenna maintenance contract, DoD flight information handbooks, and operational materials from 2022-2023.

Each station is assigned a "Global" callsign for operational use (e.g., "Andrews Global", "Sigonella Global") as documented in flight information handbooks and operational materials.

Active Stations

• Andrews Air Force Base (Joint Base Andrews), Maryland - Davidsonville (transmitter) and Brandywine (receiver) sites
• Ascension Island Auxiliary Field, South Atlantic Ocean
• RAF Croughton, England
• Diego Garcia, British Indian Ocean Territory
• Elmendorf Air Force Base (Joint Base Elmendorf-Richardson), Alaska - Range extends across the Bering Sea, vital for communications with aircraft intercepting Russian aircraft near U.S. airspace
• Guam - Anderson Air Force Base and Naval Base Guam, with Barrigada and Finegayan sites
• Hickam Air Force Base (Joint Base Pearl Harbor-Hickam), Hawaii - Lualualei and Wahiawa sites
• Lajes Field, Azores, Portugal - Cinco Picos and Villa Nova sites
• Offutt Air Force Base, Nebraska - Elkhorn (transmitter, 386 acres) and Scribner (receiver, 156 acres) sites located 35 miles northwest of Offutt in rural areas to minimize interference and keep transmitters separated from receivers. Features 32 antennas total: 15 HF, 8 directional rotatable log periodic, and 9 omni directional. The central U.S. location provides flexibility to support either coast
• Puerto Rico - Salinas and Isabela sites
• Sigonella Naval Air Station, Sicily, Italy
• West Coast - Dixon and Lincoln, California
• Yokota Air Base, Japan - Tokorozawa and Owada sites

The network consists of approximately 13-14 main station locations. Many stations have multiple transmitter and receiver sites separated to minimize interference. A 2022 operational diagram also referenced a "South Atlantic" station distinct from Ascension, but no additional details are available about this facility.

Former Stations

• Naval Air Station Keflavík, Iceland - Closed 2006
• Loring Air Force Base, Maine - Closed 1994

Station Architecture

Each HFGCS station consists of three sites: transmitter, receiver, and control, with supporting infrastructure including antennas, feedlines, intersite communications, and other support systems.

HFGCS consists of two major components: the radio/network infrastructure (Scope Command) and the antenna infrastructure (Antenna Program Support).

The current Scope Command system incorporates Automatic Link Establishment (ALE) to automate communications, and replaced older high-power Global HF equipment. Equipment is based on commercial-off-the-shelf (COTS) or Government-developed products configured for DOD to provide unique military capabilities. Current modernization efforts under the "Scope Command Next Generation" program continue to update and modernize audio switching equipment, mitigate COTS obsolescence, and update unsupportable end-of-life components.

Prior to Scope Command, the network operated different radio systems deployed over several decades:

• Scope Pattern (1950s) - 3 kW
• Scope Control (1950s) - 10 kW
• Scope Signal III (1980s) - 10 kW

Modernization

The "Scope Command Next Generation" program is modernizing the ground station infrastructure worldwide. This includes updating and modernizing audio switching equipment, mitigating commercial-off-the-shelf (COTS) obsolescence, and updating other unsupportable end-of-life components to meet increased information assurance system security compliance requirements.

A 2022 contract with Collins Aerospace for $176.9 million covers support for the ground radio network infrastructure through August 2028. The 2023 contract with Long Wave Inc. for $112.6 million covers antenna maintenance and installation through September 2030. Operations and maintenance services have also been provided by PAR Technology Corporation, which operates and maintains the satellite communications, teleport facilities, and VLF, HF, and VHF ground-based radio transmitter/receiver facilities.

HFGCS supports HF Modernization with six lines of effort across the DoD:

1. Improve Arctic C2 by implementing modern HF standard waveforms and adding station(s) at strategic locations
2. Implement DoD HF Modernization strategy synchronizing efforts across services to implement more robust and resilient waveforms
3. Execute USAF HF Modernization requirements supporting Airborne HF Radio Modernization (AHFRM) for modernized airborne radio equipment
4. Integrate Air Operations Center (AOC) HF radio requirements and robust waveforms as alternate communications in satellite-challenged environments
5. Implement PACAF HF Strategy improving INDOPACOM AOR support with robust and resilient HF communications
6. Execute NC3 HF Modernization efforts

The hardware and integration is based on commercial-off-the-shelf (COTS) or Government-developed products configured for DOD to provide unique military capabilities required for a strategic HF system. The program provides modern, robust, resilient, and dependable radio stations with beyond line of sight radio coverage to ensure HF radio communications is available in areas of interest to the United States.

See Also

• Emergency Action Message
• E-6B Mercury
• Larry Van Horn
• Nuclear Command, Control and Communications
• MYSTIC STAR