High Frequency Global Communications System

The High Frequency Global Communications System (HFGCS) is a network of single sideband shortwave transmitters of the United States Air Force which is used to communicate with aircraft in flight, ground stations and some United States Navy surface assets. All worldwide receiving and transmitting sites in the HF-GCS system are remotely controlled from Andrews Air Force Base and Grand Forks Air Force Base. Before 1 October 2002 it was known as the Global High Frequency System (GHFS).

HFGCS stations tend to operate in the aviation bands clustered around 5, 8 and 11/12 MHz, although other frequencies are in use. The primary HFGCS voice frequencies are 4724.0 kHz, 6739.0 kHz, 8992.0 kHz, 11175.0 kHz, 13200.0 kHz and 15016.0 kHz. In addition to the HFGCS, U.S. aircraft frequently use Military Affiliate Radio System (MARS) HF stations (13927.0 kHz) and Canadian Forces HF stations (11232.0 kHz) to relay messages.

One common use for the HFGCS is to place telephone calls from the aircraft in flight by means of the Defense Switched Network (DSN) to an Air Force base to obtain local weather conditions, to arrange for refueling, and to inform the base of the number of passengers and crew. The HFGCS also carries Emergency Action Messages.^[1]

In addition to EAM's the HFGCS also carries a few different types of messages. A higher priority code for orders is a Skyking Message, which is a time sensitive message for orders that need immediate attention. Force Direction Messages (FDM's) are also sent through the HFGCS, although it is impossible to tell whether the message is an FDM or just another EAM being read.^[1] The sign off 'Colour Bar' is currently being used (2016) at the end of the transmission.

Although transmissions are often single sideband, the use of the ALE transmission mode is more and more common. Naval Special Warfare HFGCS complements the use of satellite communications between aircraft and ground stations.

Stations of the HF-GCS Network^[1]

• Andersen Global, Andersen Air Force Base, Guam, USA
• Andrews Global, Andrews Air Force Base, Maryland, USA
• Ascension Global, Ascension Auxiliary Airfield, Ascension Island, British Overseas Territories
• Croughton Global, RAF Croughton, United Kingdom
• Diego Garcia Global, Diego Garcia Naval Station, British Indian Ocean Territory
• Elmendorf Global, Elmendorf Air Force Base, Alaska, USA
• Hickam Global, Hickam Air Force Base, Hawaii, USA
• Lajes Global, Lajes Field, Azores, Portugal
• Lincoln Receiver Site (aka West Coast Global), Beale Air Force Base, California, USA
• Offutt Global, Offutt Air Force Base, Nebraska, USA
• Puerto Rico Global, Salinas, Puerto Rico, USA
• Sigonella Global, Naval Air Station Sigonella, Sicily, Italy
• Yokota Global, Yokota Air Base, Japan

Closed Stations

• Thule Air Base, Greenland
• Keflavík Global, Keflavík NAS, Iceland

References

Wikimedia Commons has media related to High Frequency Global Communications System.

1. 1 2 3 "The HF-GCS". October 2014. Retrieved October 28, 2014. 

Further reading