The Propagation of Radio Waves of Frequency Less than 1 kc

The simplified mode theory of propagation in a waveguide formed by the earth and a concentric ionosphere of constant height is applied to the experimental observations of Chapman and Macario for the frequency range between 100 cps and 1000 cps. It is demonstrated that the discrepancies between the theory and the nighttime experimental results may be explained by modifying the theory and postulating an effective increase in the ionospheric height as the frequency decreases. This concept is also shown to be not necessarily incompatible with the results for day.