Hyper-Frequency Wave Guides — General Considerations 

 and Experimental Results * 



By G. C. SOUTHWORTH 



A peculiar form of electrical propagation is described below. It makes 

 use of extremely high frequencies — «ven beyond those generally employed 

 in radio. In some respects it resembles ordinary wire transmission but un- 

 like the latter there are no return conductors, at least of the usual kind. 



In this transmission, electromagnetic waves are sent through guides made 

 up either of an insulator alone or of an insulator surrounded b\- a conductor. 

 In a special case this insulator may be air. There are at least four different 

 types of waves or electrical configurations that may be propagated. One of 

 them is such that theor\- indicates its attenuation through a hollow conduc- 

 tor continuousK- decreases with increase of frequency. Although the paper 

 deals largely with the nature of this transmission, some of the fundamental 

 pieces of apparatus used in experimental work are described. The\' include 

 generators, receivers and wave-meters. 



Introduction 



THIS paper describes a novel form of electrical propagation by 

 means of which extremely high-frequency waves may be trans- 

 mitted from one point to another, through specially constructed wave 

 guides. The guide used for this purpose may take any one of several 

 different forms. It may be a hollow copper pipe, which for the higher 

 frequencies now available would be about 3 or 4 inches in diameter, 

 or possibly a somewhat smaller conducting tube filled with some in- 

 sulating material combining high dielectric constant and low loss, or 

 it may conceivably be a rod or wire of dielectric material. ^ 



The phenomena involved in this form of transmission are exceed- 

 ingly interesting and at first sight paradoxical for in some cases trans- 

 mission is effected through a single wire of insulating material sur- 

 rounded by metal in place of a pair of metal wires surrounded by 

 insulation. In others the wire is made entirely of insulating material. 

 In still others electrical effects are observed only on the interior of 

 hollow metal cavities instead of the exterior only as is ordinarily 

 experienced. In all cases there is no return current path, at least of 

 the kind that is commonly assumed in ordinary transmission. 



The frequencies appropriate for this form of transmission begin at 

 the higher of those generally known as ultra-high frequencies that is, 

 2000 mc. (X = 15 cm.) and extend to an indefinite upper limit possibly 



*To be presented at joint meeting of Amer. Phys. Soc. and I.R.E., Washington 

 D. C, April 30, 1936. 



• The mathematical theor\- of these phenomena is given in a companion paper 

 by J. R. Carson, S. P. Mead and S. A. SchelkunofT, this issue of the Bell System 

 Technical Journal. 



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