Phase characteristics of h.f. radio waves received after propagation by the ionosphere

A radio wave after reflection from the ionosphere is considered to consist of a specularly reflected component plus a varying diffracted component. The ratio of the power in the specular component to that in the diffracted component is of interest in considering the design and performance of large-aperture receiving arrays. A theoretical treatment is presented whereby this ratio can be derived from the probability distribution of the phase difference between the signals received at two widely spaced aerials. Apparatus for the determination of the phase-difference distribution is described, and the experimental technique developed for using the apparatus is discussed. The results of measurements made on typical h.f. transmissions are presented and discussed in relation to known ionospheric phenomena. Consideration is also given to the use of the techniques for the determination of the vertical arrival angle and the angular spread of the cone of radiation of a received signal.