Measurements of Changes in the Phase Path of Radio Waves Reflected from the Ionosphere at Normal Incidence

Abstract

Fixed-frequency measurements were made at Brisbane, using pulse transmissions, of the changes in phase of radio waves i'eceived after reflection at normal incidence from the various ionospheric layers. Because of the homodyne detector used, such phase-path records have a very good signal-to-noise ratio, Also, due to the difference in behaviour of echoes of different polarization or from different ionospheric layers, the effective resolution is high. When the echoes had a well-defined phase, the rate of change of phase path with time was measured; the slowest rates were for smooth night-time Es layers, when values as low as I m sec-1 were sometimes found, whereas for the night-time F. region the rates were usually in the range 10-40 m sec-l. Records were also made of reflections from drifting Es clouds, and of the effect of underlying Es ionization on reflections from the F. region.