H. F. Propagation Confidence Levels and Path Independence

This paper presents the results of a study concerning the confidence limits applicable to the HF (high frequency) propagation prediction techniques presently available for predicting the performance of communications systems operating in the sky-wave mode in the 3-30 megacycle frequency band. The paper also discusses the independence of HF paths in terms of the diversity techniques required to obtain reliable HF communications systems. An example of a communications link designed by the use of HF prediction and diversity techniques is presented. (Author)