HYPER-FREQUENCY TRANSMISSION 311 



of this paper. Another paper, entitled "Cber den Nachweis elektro- 

 magnetischer Wellen an dielektrischen Drahten," ^pubHshed in 1916 by 

 Zahn, is of interest because of the historical note attached, which 

 indicates that experimental work was begun in 1914 by Riiter and 

 Schriever, two students of Zahn, and continued with such diligence as 

 the exigencies of war permitted until the date of Zahn's paper, at least. 

 In 1920 Southworth, then working at Yale University, accidentally 

 observed such waves in a trough of water which he was using in con- 

 nection with some high-frequency studies, measured their wave-lengths 

 and recognized their identity with those discussed by Schriever '" 

 in a paper which appeared at about that time. In 1924 Carson re- 

 discovered the transmission characteristics of the hollow conducting 

 cylinder, and disclosed it in an unpublished memorandum entitled 

 "Hyper-Frequency Wave Filters." Finally, in 1931, Southworth, 

 then a research engineer with the American Telephone and Tele- 

 graph Company, returned to the subject and initiated the compre- 

 hensive investigation which he is reporting in a companion paper. '^ 

 Independently, and almost simultaneously. Hartley, at the Bell 

 Telephone Laboratories, suggested the possibility of guided transmis- 

 sion along a hollow cylindrical dielectric wire; and these two (South- 

 worth and Hartley) enlisted our cooperation in a mathematical in- 

 vestigation. 



In the theoretical parts of these papers dissipation was always 

 neglected, though obviously the attenuation would be a controlling 

 factor in practical applications. The writers, on the other hand, have 

 given especial attention to this factor. Out of this research there 

 emerged the remarkable fact that with hollow conducting guides there 

 exists one and only one type of wave the attenuation of which decreases 

 with increasing frequency; a unique characteristic which does not 

 attach to dielectric wires, nor so far as the writers are aware, to any 

 other type of guided wave. 



lA. Transmission Through Hollow Conducting Cylinders 



Throughout this paper it will be assumed that the cylindrical sheath 

 possesses high conductivity and that the losses in the internal dielectric 

 medium are either small or negligible. Subject to these assumptions 

 the effect of dissipation on the attenuation of the wave is formulated in 



* Ann. der Phys., Vol. 49, 1916, pp. 907-933. This paper contains several col- 

 lateral references. 



* " Elektromagnetischen Wellen an Dielektrischen Drahten," Ann. der Phys., Vol. 

 63, 1920, pp. 645-673. 



'"Hyper-Frequency Wave Guides — General Considerations and Experimental 

 Results," G. C. Southworth, this issue of the Bell System Technical Journal. 



