The role of the ionosphere in radio wave propagation

WHEN Marconi electrified the world in 1901 by sending radio signals across the Atlantic Ocean, he incidentally proved that the upper atmosphere is electrified. Diffraction was insufficient to explain the bending of the electromagnetic waves around the 30 degrees of the earth´s curved surface. The waves could not penetrate the earth. So there was only one way they could go the incredible distance, and that was by reflection from one or more conducting strata in the atmosphere. So reasoned Professor A. E. Kennelly, and he published the idea a few months after Marconi´s demonstration. Oliver Heaviside reached the same conclusion and published² it at nearly the same time; his paper however mentioned only a single layer. This postulated layer was known for a number of years as the Kennelly-Heaviside layer, and the entire ionized region in the upper atmosphere which affects the transmission of radio waves is now called the ionosphere. Radio waves transmitted by means of it are called sky waves, in contradistinction to the ground waves, those which are propagated along the earth´s surface.