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In this article, different modes of propagation are presented first. Factors affecting ground‐wave propagation are discussed. Propagation models and available software are presented and compared. The solar–terrestrial system, which forms the sky‐wave propagation environment, is described. Factors affecting sky‐wave propagation are discussed in detail. Different propagation models are discussed qualitatively and compared quantitatively. Definitions of the most important terms relating to propagation are given in Section 6.

Abstract. This paper presents results of an extensive comparative study in which all four major field-strength prediction methods are compared with measured data. The most recent data bank has been used. These methods are analyzed in detail. Factors affecting sky-wave propagation are discussed. Some historical background is also presented. IntroductionThe purpose of this paper is to evaluate the currently used LF/MF sky-wave propagation models. A brief historical background, including some major worldwide field-strength measurement campaigns, is presented in section 2. The most up-to-date and largest data bank has been organized and studied and used in this study. Factors affecting sky-wave propagation and some observed phenomena are discussed in section 3. Currently used methods for predicting field strengths are qualitatively discussed in section 4 and quantitatively compared in section 5. Historical Background: Six Decades of Concerted EffortsIn this section a brief historical background behind the currently used field-strength prediction models is given. This is important for two reasons: to document some valuable historical facts and, more importantly, to help the users to select the right propagation models for their particular applications. The two curves were formally adopted at the 1938 Early International Efforts and the Cairo

The sections in this article are Ground‐Wave Propagation The Sky‐Wave Propagation Environment Sky‐Wave Propagation at LF and MF Sky‐Wave Propagation at High Frequency Space‐Wave Propagation at VHF and UHF Acknowledgments and Closing Remarks Glossary