HF - Global Communications System
The High freqeuncy Global Comunication System (HF-GCS) is a network of short wave transmitters of the United States Air Force , which is used to communicate with aircraft in flight, ground stations and some surface activity States Navy States.
The transmitters and receivers worldwide system HF-GCS are controlled remotely from Andrews. Before 1 October 2002, the system was known as Global High Frequency System (GHFS) .
The stations HF-GCS tend to operate in aeronautical bands around 5, 8 and 11/12 MHz, but they are in use also other freqeunze.
The frequencies in the voice of the HF-GCS main 4724.0 kHz, 6739.0 kHz, 8992.0 kHz, 11175.0 kHz, 13200.0 kHz and 15016.0 kHz in USB. In addition to HF-GCS, US military planes often use the system Affiliate Radio System (MARS) , with stations HF ( 13927.0 kHz ) and the Canadian Forces stations HF ( 11232.0 kHz ) to transmit messages.
A common use for the HF-GCS is to allow communication between the aircraft in flight through the Defensive Switched Network (DSN) with an Air Force base and to get local weather conditions, to arrange for refueling, and to inform the basis of the number of passengers and crew.
The HF-GCS also performs the communication function of emergency messages Emergency Action Messages (EAM).
Furthermore, the EAM the HF-GCS also plays a few different types of messages. A priority code higher orders is a message Skyking, which is a message for orders that require immediate attention.
Force Direction Messages (FDM's) are sent through the HF-GCS, although it is impossible to determine whether the message is a FDM or just another EAM in reading phase.
Although the broadcasts are often in SSB, the use of the transmission mode digital ALE is increasingly common. Naval Special Warfare HF-GCS integrates the use of satellite communications between aircraft and ground stations.
Guide for Receiving
The communications can be easily received leaving any receiver for radio amateurs or SWL switched on the frequencies indicated above, in particular on 8992.0 kHz USB.
It is not need for special antennas for the reception, whose signal intensity is always good during the arc the haunting and the calendar year; However you will need to be in an open or have an external antenna.
Emergency Action Message (EAM)
In the system of command and control of strategic nuclear weapons of the US military, an 'Emergency Action Message (EAM) is a preformatted message that directs nuclear forces with capacity to perform specific main attack options (MAO) or limited attack options (Laos ) in a nuclear war. Individual countries or regions may be included or referenced in the EAM, as specified in the single integrated operational plan (SIOP).
Messages EAM using cryptographic protocols (including methods such as digital signature) to authenticate messages, to ensure that they can not be forged or altered.
In the US, the EAM will be issued by the National Military Command Center (NMCC) in the Pentagon or, if it was destroyed by an enemy attack first, by a deputy National Military Command Center or the Boeing E-4B National Airborne Operations Center (NAOC).
Messages are sent in digital format for the main commands with nuclear capability through the digital network of automatic safety (AUTODIN). The messages are then relayed to the aircraft that are in a state of alert by the US Strategic Command at Offutt Air Force Base in Omaha, Nebraska, with a single sideband modulation of high frequency radio transmitters Global Communications System (formerly known as the Global Service high frequency). The EAM is forwarded to nuclear submarines launchers firing through repeaters special designed for communication with submarines. The transmitters include those designed to operate at very low frequency (VLF). Submarines collect the message via special antennas. The applicant must then nuclear forces able to make a EAM without fail. Manned bombers can be recalled, but the missiles fired from silos in the ground or from submarines can not be recalled.
Skyking messages are read on the same network as EAM, also known as "Foxtrot Broadcast" these messages stop an EAM, if necessary, to be read. They contain a higher priority and time sensitive code for orders that require immediate attention.
The stations of the system HF-GCS:
- Global Andersen, Andersen Air Force Base, Guam Island
Global Andrews, Andrews Air Force Base, Maryland USA
Global Ascension, RAF Ascension Island, Atlantic Ocean
Croughton Global, RAF Croughton, United Kingdom
Global Diego Garcia, Diego Garcia Naval Station, Indian Ocean
Global Elmendorf, Elmendorf Air Force Base, Alaska
Hickam Global, Hickam Air Force Base, Hawaii
Global Lajes, Lajes Field, Azores
Lincoln Receiver Site (aka West Coast Global), Beale Air Force Base, California
Offutt Global, Offutt AFB, Nebraska
Puerto Rico Global, Salinas, Puerto Rico
Global Sigonella Naval Air Station Sigonella, Sicily, Italy
Global Yokota, Yokota Air Base, Japan
- Thule Air Base, Greenland
Keflavík Global, NAS Keflavik, Iceland
Summer time (April/September)
|Andrews||0500z 1330z||0300z 1600z||24/24||24/24||1330z 0500z||1600z 0300z|
|Ascension||2300z 0700z||2200z 0900z||24/24||24/24||0700z 2300z||0900z 2200z|
|Croughton||2300z 0600z||2100z 0800z||24/24||24/24||0600z 2300z||0800z 2100z|
|Diego Garcia||1400z||1200z 0200z||24/24||24/24||0100z 1400z||0200z 1200z|
|Elmendorf||0600z 1500z||0400z 1700z||24/24||24/24||1500z 0600z||1700z 0400z|
|Guam||1300z 2200z||1100z 2400z||24/24||24/24||2200z 1300z||2400z 1100z|
|Hawaii||0800z 1700z||0700z 1800z||24/24||24/24||1700z 0800z||1800z 0700z|
|Lajes||2200z 0800z||2000z 1200z||24/24||24/24||0800z 2200z||1200z 2000z|
|Offutt||0400z 1330z||0200z 1700z||24/24||24/24||1330z 0400z||1700z 0200z|
|Puerto Rico||0400z 1200z||0100z 1400z||24/24||24/24||1200z 0400z||1400z 0100z|
|Sigonella||2200z 0530z||1900z 0900z||24/24||24/24||0530z 2200z||0900z 1900z|
|West Coast||0600z 1400z||0300z 1800z||24/24||24/24||1400z 0600z||2200z 1100z|
|Yokota||1300z 2200z||1100z 2200z||24/24||24/24||2200z 1300z||2200z 1100z|
Winter season (October/Marc)
|Andrews||2400z 1200z||2200z 1400z||24/24||24/24||1200z 2400z||1400z 2200z|
|Ascension||2200z 0800z||2100z 1000z||24/24||24/24||0800z 2200z||1000z 2100z|
|Croughton||1800z 0600z||1700z 0900z||24/24||24/24||0600z 1800z||0900z 1700z|
|Diego Garcia||1600z 2300z||1400z 0200z||24/24||24/24||2300z 1600z||0200z 1400z|
|Elmendorf||0330z 1630z||0200z 1800z||24/24||24/24||1630z 0330z||1800z 0200z|
|Guam||1300z 2030z||0800z 2200z||24/24||24/24||2030z 1300z||2200z 0800z|
|Hawaii||0700z 1600z||0400z 1800z||24/24||24/24||1600z 0700z||1800z 0400z|
|Lajes||1800z 0730z||1700z 0900z||24/24||24/24||0730z 1800z||0900z 1700z|
|Offutt||0030z 1330z||2300z 1400z||24/24||24/24||1330z 0030z||1400z 2300z|
|Puerto Rico||0100z 1100z||2300z 1200z||24/24||24/24||1100z 0100z||1200z 2300z|
|Sigonella||1700z 0500z||1600z 0800z||24/24||24/24||0500z 1700z||0800z 1600z|
|West Coast||0130z 1400z||0030z 1500z||24/24||24/24||1400z 0130z||1500z 0030z|
|Yokota||0900z 2100z||0800z 2200z||24/24||24/24||2100z 0900z||2200z 0800z|
Thank's Oliver for translating!