High frequency (HF) radio is a consistent and critical communications technology for government, civilian, and military institutions throughout the world. Fortified by recent technological advancements, it is rapidly presenting itself as a practical alternative to many satellite systems — providing comparable service that is less expensive and more readily available. This up-to-date, comprehensive reference and planner's guide presents an in-depth description of automated HF communications, considers the many phenomena that affect HF radio, and offers penetrating insight into new and future HF engineering techniques, including: • New information on automatic link establishment (ALE) technology • Advanced variable-transmission rate modems • Wideband (1 MHz) HF communications services • Automated HF networks as an extension of the Internet Helpful chapter-end examples, 100 illustrations, and 135 equations make this an invaluable guide for communications engineers involved with the manufacture of HF radio and ancillary equipment. The authors draw upon years of experience to offer new approaches for establishing and maintaining an automated HF network, based on industry and governmental standards. In addition, it serves as an excellent tutorial for graduate students and systems-level planners.