A model for time and frequency spreading of HF radio signals propagating through the equatorial ionosphere

An essential part of a method for the prediction of reliability of a digital communication system at HF, is the inclusion of a model for post-sunset scattering of signals in both the time and frequency domains. Although models have been developed for trans-ionospheric scintillation, little quantitative data is available for terrestrial systems. This paper proposes a model and indicates a procedure for the inclusion of scattering in the estimation of reliability.