USAF High Frequency Global Communications System

USAF HIGH FREQUENCY GLOBAL COMMUNICATIONS SYSTEM (HFGCS)

GENERAL - The HFGCS System is a worldwide network of 15 high-power HF stations providing air/ground HF command and control radio communications between ground agencies and US military aircraft and ships. Allied military and other aircraft are also provided support IAW agreements and international protocols as appropriate. The HFGCS is not dedicated to any service or command, but supports all DoD authorized users on a traffic precedence/priority basis. General services provided by the HFGCS are:

• General Phone Patch and Message Relay Services
• Automatic Link Establishment (ALE)
• HF Data Support
• Command and Control Mission Following
• Emergency Assistance
• Broadcasts
• HF Direction Finding Assistance
• ATC Support
• E-Mail connectivity to NIPRNeT and SIPRNeT

MODERNIZATION - SCOPE Command replaces older high power Global HF equipment. SCOPE Command incorporates Automatic Link Establishment (ALE) to automate communications. All HFGCS station transmit and receive equipment is remotely controlled from the Centralized Network Control Station (CNCS) at Andrews AFB, MD.

General Calling. Aircrews use a preliminary call as outlined in ACP-121 US Supp 2 using the collective callsign "MAINSAIL" or the HFGCS station call sign (example: Sigonella Global this is Dark 86 on 11175, OVER). HFGCS operators require approximately 10 seconds (for automated equipment configuration) to respond to calls for service. The HFGCS operator may request the aircraft change to a discrete frequency for improved and/or extended service.

(a) PUBLISHED FREQUENCY LISTING - frequencies to provide increased "Global" coverage. The published frequency listing does not reflect complete system frequency authorizations. These published frequencies will be used for initial contact, EAM broadcasts, and short-term C2 phone patch and message delivery. Other extended or special services will be moved to each station’s available "discrete" frequencies.

(b) FREQUENCY GUIDE - The frequency guides are designed to optimize air/ ground communications.

Primary HFGCS Frequencies 24 Hours:   8992 and 11175
Back up HFGCS Frequencies Day:        13200 15016
Back up HFGCS Frequencies Night:      4724 6739

                         DISTANCE (1)
TIME (2)
       200-7500 NM      750-1500 NM           More than 1500 NM
-------------------------------------------------------------------
0000L   4724            6712-6739-8992        6712-6739-8992-11175
0400 L  4724            4724-6712-6739        6712-6739-8992
0800 L  4724-6712-6739  6712-6739-8992-11175  11175-13200-15016
1200 L  4724-6712-6739  8992-11175-13200      13200-15016
1600 L  4724-6712-6739  8992-11175-13200      13200-15016
2000 L  4724-6712-6739  6712-6739-8992-11175  1175-13200-15016

1. When less than 200 NM any frequency
2. Local time at ground station.

FREQUENCIES - SUMMER (Apr-Sep)
STATION    4724       6712        6739        8992      11175     13200       15016
----------------------------------------------------------------------------------------
Andrews   0500-1330Z              0300-1600Z  24 hours  24 hours  1330-0500Z  1600-0300Z
Ascension 2300-0700Z              2200-0900Z  24 hours  24 hours  0700-2300Z  0900-2200Z
Croughton 2300-0600Z  2100-0800Z              24 hours  24 hours  0600-2300Z  0800-2100Z
Dieg Gar  1400-0100Z              1200-0200Z  24 hours  24 hours  0100-1400Z  0200-1200Z
Elmendorf 0600-1500Z              0400-1700Z  24 hours  24 hours  1500-0600Z  1700-0400Z
Guam      1300-2200Z              1100-2400Z  24 hours  24 hours  2200-1300Z  2400-1100Z
Hawaii    0800-1700Z              0700-1800Z  24 hours  24 hours  1700-0800Z  1800-0700Z
Keflavik  1930-0600Z              1630-1000Z  24 hours  24 hours  0600-1930Z  1000-1630Z
Lajes     2200-0800Z              2000-1200Z  24 hours  24 hours  0800-2200Z  1200-2000Z
Offutt    0400-1330Z              0200-1700Z  24 hours  24 hours  1330-0400Z  1700-0200Z
Puerto R  0400-1200Z              0100-1400Z  24 hours  24 hours  1200-0400Z  1400-0100Z
Sigonella 2200-0530Z              1900-0900Z  24 hours  24 hours  0530-2200Z  0900-1900Z
West Coas 0600-1400Z              0300-1800Z  24 hours  24 hours  1400-0600Z  1800-0300Z
Yokota    1300-2200Z              1100-2200Z  24 hours  24 hours  2200-1300Z  2200-1100Z

FREQUENCIES - WINTER (Oct-Mar)
STATION   4724        6712        6739        8992      11175     13200       15016
----------------------------------------------------------------------------------------
Andrews   2400-1200Z              2200-1400Z  24 hours  24 hours  1200-2400Z  1400-2200Z
Ascension 2200-0800Z              2100-1000Z  24 hours  24 hours  0800-2200Z  1000-2100Z
Croughton 1800-0600Z  1700-0900Z              24 hours  24 hours  0600-1800Z  0900-1700Z
Diego Gar 1600-2300Z              1400-0200Z  24 hours  24 hours  2300-1600Z  0200-1400Z
Elmendorf 0330-1630Z              0200-1800Z  24 hours  24 hours  1630-0330Z  1800-0200Z
Guam      1300-2030Z              0800-2200Z  24 hours  24 hours  2030-1300Z  2200-0800Z
Hawaii    0700-1600Z              0400-1800Z  24 hours  24 hours  1600-0700Z  1800-0400Z
Keflavik  1700-0730Z              1530-1000Z  24 hours  24 hours  0730-1700Z  1000-1530Z
Lajes     1800-0730Z              1700-0900Z  24 hours  24 hours  0730-1800Z  0900-1700Z
Offutt    0030-1330Z              2300-1400Z  24 hours  24 hours  1330-0030Z  1400-2300Z
Puerto R  0100-1100Z              2300-1200Z  24 hours  24 hours  1100-0100Z  1200-2300Z
Sigonella 1700-0500Z              1600-0800Z  24 hours  24 hours  0500-1700Z  0800-1600Z
West Coas 0130-1400Z              0030-1500Z  24 hours  24 hours  1400-0130Z  1500-0030Z
Yokota    0900-2100Z              0800-2200Z  24 hours  24 hours  2100-0900Z  2200-0800Z

Unclassified Phone Patch and Message Relay Services

(a) Phone Patch Service. Phone patching allows direct voice communications between ground agencies and aircraft by electronically connecting telephone circuits to radio transmitters and receivers. Phone patch service is reserved for official unclassified business only and shouldn’t exceed 5 minutes. Patches of more than 5 minutes or of a sensitive nature should be run on a discrete frequency. Users requesting a phone patch must include all information necessary for HFGCS operators to complete the call, such as the identity or location of the called parties and telephone number if known. Phone patches are monitored by HFGCS operators. If radio reception isn’t of sufficient quality to complete the patch, they will attempt to copy the traffic and relay it to addressees.

(b) Message Relay Service. HFGCS operators transcribe encoded or plain-text messages for aircraft or ground stations and forward them to the addresses by radio or landline. The text of the messages can be in the form of alpha-numerics, code words, plain text, acronyms, and/or numerical sequences. Aircrews may use "READ BACK" procedures when the message data is critical, or when an incomplete transmission is suspected due to poor radio reception. All messages received by Global stations will be accepted and delivered by the fastest means available according to precedence and priority.

(c) ALE - For ALE radios to operate properly, the radio must have a loaded datafill,

ALE Address and Frequency Chart
Station      ALE      Frequency
             Address  3137 4721 5708 6721 9025 11226 13215 15043 18003 23337
Andrews      ADW       x    x    x    x    x    x     x     x     x     x
Ascension    HAW       x    x         x    x    x     x     x     x     x
Croughton    CRO       x    x         x    x    x     x     x     x     x
Diego Garcia JDG       x    x    x    x    x    x     x     x     x     x
Elmendorf    AED       x    x    x    x    x    x     x     x     x     x
Guam         GUA       x    x    x    x    x    x     x     x     x     x
Hawaii       HIK       x    x         x    x    x     x     x     x     x
Keflavik     IKF       x    x    x    x    x    x     x     x     x     x
Lajes        PLA       x    x    x    x    x    x     x     x     x     x
McClellan    MCC       x    x    x    x    x    x     x     x     x     x
Offutt       OFF       x    x    x    x    x    x     x     x     x     x
Salinas      JNR       x    x    x    x    x    x     x     x     x     x
Sigonella    ICZ       x    x    x    x    x    x     x     x     x     
S Atlantic   MPA       x    x    x    x    x    x     x     x     x     x
West Coast   MCC       x    x    x    x    x    x     x     x     x     x
Yokota       JTY       x    x         x    x    x     x     x     x     x