United States High Frequency Global Communications System (HFGCS)
Frequencies (USB) 4724kc, 8992kc, 11175kc, 15016kc

Mainsail: Any ground station

The Network Control Station uses a one- or two-word callsign that is replaced daily at 00:00 UTC

Individual stations: Andersen, Andrews, Ascension, Croughton, Diego Garcia, Elmendorf, Hickam, Lajes, Offutt, Puerto Rico, Sigonella, West Coast, Yokota

Aircraft callsigns (partial list)
Reach ###: Air Mobility Command transport aircraft
Doom ##, Rogue ##, Skull ##: Boeing B-52 Stratofortress

ALE
Frequencies (USB) 3137kc, 4721kc, 5708kc, 6721kc, 9025kc, 11226kc, 13215kc, 15043kc, 18003kc, 23337kc

Ground station addresses
ADW: Andrews
AED: Elmendorf
CRO: Croughton
GUA: Andersen
HAW: Ascension
HIK: Hickam
ICZ: Sigonella
JDG: Diego Garcia
JNR: Puerto Rico
JTY: Yokota
MCC: West Coast
OFF: Offutt
PLA: Lajes

Aircraft addresses (partial list)
1#####: Lockheed C-5 Galaxy
2#####: Boeing C-17 Globemaster III
4#####: McDonnell Douglas KC-10 Extender
5#####: Boeing KC-135 Stratotanker
E3####: Boeing E-3 Sentry
NW1: Boeing E-4 ("Nightwatch")
NOTE: The digits are taken from the last digits of the tail numbers.
The ALE channels are used primarily for text messaging with the 2G ALE Automatic Message Display (AMD) feature, although radio checks using plain voice are common. Each active ground station emits an ALE sounding every 3 hours.

SIPRNet

Frequencies (USB) 3113kc, 5702kc, 6715kc, 8968kc, 11181kc, 15091kc, 17976kc, 27870kc


Ground station addresses
ADWSPR: Andrews
AEDSPR: Elmendorf
CROSPR: Croughton
GUASPR: Andersen
HAWSPR: Ascension
HIKSPR: Hickam
ICZSPR: Sigonella
JDGSPR: Diego Garcia
JNRSPR: Puerto Rico
JTYSPR: Yokota
MCCSPR: West Coast
OFFSPR: Offutt
PLASPR: Lajes

Aircraft addresses: Same as the ALE network, but with the suffix DAT or IGM

The HFGCS provides an HF gateway into the SIPRNet, a U.S. Department of Defense computer network for classified information. Links are established using 2G ALE, while the data mode used is MIL-STD-188-110A.