Radio wave propagation-20´th century highlights

Summary form only given. This paper examines the highlights in the early development of the theory and understanding of radio wave propagation in the 20th century. By the end of the 19th century Maxwell´s equations were well accepted and had been convincingly shown to be valid by a series of detailed experiments carried out by H.R. Hertz as well as others, in particular J.C. Bose. Marconi´s bold experiment in the transmission of telegraph signals across the Atlantic ocean from Prohbu in Cornwall, England to St. Johns, Newfoundland in 1901 was perhaps the unique event that ushered in the era of wireless communications. This success in long distance transmission of radio waves led to considerable speculation on the mechanism of how these waves propagated around the spherical Earth. Four possible mechanisms were in contention for a number of years. These were: diffraction around the Earth, atmospheric refraction, the propagation by means of a surface wave which was investigated by Zenneck in 1907 and demonstrated by the theoretical work of Sommerfeld in his 1911 paper, and the reflection from an upper layer of ionized gas which had been predicted to exist independently by Kennelly and Heaviside in 1902.