General Theory on the Propagation of Radio Waves in the Ionized Layer of the Upper Atmosphere

1. Theories on the propagation of radio waves in the entire range of frequencies used in communications are treated together with discussions on the applicable limit of the theory of geometrical optics to wave propagation. 2. Definitions of the "low-frequency," "medium-frequency," "medium-high-frequency," and "high-frequency" waves are given from the theoretical points of view. 3. A new term, "step reflection," is introduced to explain the propagation of medium-frequency waves, and its characteristics are explained. 4. Attenuation of a wave traveling through the ionized layer is calculated for various kinds of wave paths and electronic distributions. 5. The "metallic reflection theory" is applied to the investigations of the low-frequency transmission and a number of low-frequency phenomena; especially the sunset and sunrise drop of field intensity and polarization errors (or night errors) in direction finding are explained by applying the present theory. 6. Propagation of medium-frequency waves is treated by using the "step reflection method." 7. Medium-high-frequency and high-frequency transmissions are treated by applying the theory of geometrical optics, giving reasons why waves of 100-meter band in daylight and those of 500-meter band during the night have bad transmission characteristics. Propagation characteristics of the waves in the entire range of frequencies used in radio communications are seen in Table I and Fig. 9. 8. Transmission characteristics of the waves of various frequencies during the magnetic storm are theoretically considered by comparing them with our experiences hitherto known.