General Concepts of Modern HF Communications

For the military in many nations, if not in all nations, HF is a primary means of communications rather than a backup. In some countries no other communication techniques are contemplated for such services as ship to shore or aircraft to ground over distances beyond line of site. The vulnerability of satellites makes nations consider HF communications as a primary military communication medium even when satellites are part of their military operations. For HF communications, the basic advances are in equipment development, in the concept of Real Time Channel Evaluation, and in the coding and error correction methods incorporated in developed and developing modems. In order to outline the concepts of modern HF communications, the Electromagnetic Wave Propagation Panel of AGARD/NATO developed a lecture series on this subject. Propagation advances, error correction methods, and equipment advances as illustrated by material from the lecturers in this unclassified series will be outlined.