Link-11 is the U.S. Navy shipboard version of NATO’s Tactical Data Information Link “A” (TADIL A). The Link-11 system is used to provide high-speed, computer-to-computer exchange of digital tactical information among ships, aircraft, and shore installations.
Link-11 data communications can operate with either high-frequency (HF) or ultra-high-frequency (UHF) radios. In the HF band, Link-11 provides gapless omnidirectional coverage of up to 300 nautical miles from the transmitting site. In the UHF band, the Link-11 system is capable of line-of-sight omnidirectional coverage, approximately 25 nautical miles between ships and 150 nautical miles for ship-to-air links.
It features an 8 phase PSK (DCPSK, Differentially Coherent PSK), scrambled, 1800Hz tone. The system is supposed to be good against poor HF conditions and problems such as multipath and fading. Throughput rates up to 4800bps occur with block interleaving of 0, 1.2 or 9.6 sec delay. Each packet has 192 bits (80ms) + 64 bits sync (26.67ms), each frame carries 72 bits of user info and the last frame always contains a 72 bit stop sequence. This waveform is implemented in the General Atronic GA-122 HF modem or the Harris RF-5254B. Swedish diplo stations use a derivative of this system from Rockwell/Collins (Mediaware). Single tone modems sound like 3kHz of noise.
Extensive use by US and NATO forces
Audio Samples and Waveform
Technical Description courtesy of the DigiFAQ 5.3, copyright 1995-1997 by Mike Chace-Ortiz and Stan Skalsky, 1995-2006 by Worldwide Utility News. Used with permission and All Rights Reserved