The Physical Reality of Zenneck's Surface Wave 



By W. HOWARD WISE 



The first part of the paper shows that a vertical dipole does not 

 generate a surface wave which at great distances behaves like 

 Zenneck's plane surface wave. In Parts Two and Three it is shown 

 that it is not necessary to call upon the Zenneck wave to explain 

 the success of the wave antennas. 



IN 1907 ^ Zenneck showed that a plane interface between two semi- 

 infinite media could support, or guide, an electromagnetic wave 

 which is exponentially attenuated in the direction of propagation along 

 the interface and vertically upwards and downwards from the interface. 

 Zenneck did not show that an antenna could generate such a wave 

 but, because this "surface wave" seemed to be a plausible explanation 

 of the propagation of radio waves to great distances, it was commonly 

 accepted as one of the components of the radiation from an antenna. 



After Sommerfeld ^ formulated the wave function for a vertical 

 infinitesimal dipole as an infinite integral and noted that the integral 

 around the pole of the integrand is the wave function for a surface 

 wave, which at great distances is identical with the Zenneck wave, 

 no one questioned the reality of Zenneck's surface wave. 



There has been recently pointed out by C. R. Burrows ^^ the lack 

 of agreement between various formulas and curves of radio attenuation 

 over land when the dielectric constant of the ground must be taken 

 into account. The values of Sommerfeld ^ and Rolf ^ are stated to 

 differ from those of Weyl ^ and Norton ^ by an amount just equal 

 to the surface wave of Zenneck. Burrows ^^ presents experimental 

 data supporting the correctness of the Weyl-Norton values and raises 

 a question as to whether a surface wave really is set up by a radio 

 antenna. A vertical current dipole does not generate a surface wave 

 which at great distances behaves like Zenneck's plane surface wave. 

 Theoretical and numerical evidence leading to this conclusion is 

 presented in Part One of this paper. A contemporary theoretical 

 investigation by S. O. Rice * leads to the same conclusion. 



The reader familiar with wave antennas will at once ask why the 

 wave antennas seem to justify the Zenneck surface wave theory by 

 means of which they were conceived and designed if there is no surface 



* "Series for the Wave Function of a Radiating Dipole at the Earth's Surface," 

 this issue of the Bell Sys. Tech. Jour. 



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