1218 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 6 — Base band width per channel versus frequency (for one-mile of wave- 

 guide) using the circular electric mode, loss held constant by varying pipe diame- 

 ter. 



diameters on the order of 1 to 2 inches. Having selected the general 

 region which appears attractive, it is important to know the communi- 

 cation characteristics of a given waveguide. Figs. 7 and 8 show the 

 attenuation and bandwidth characteristics respectively for a 2-inch 

 round copper tube. The theoretical loss (Fig. 7) for the TEoi wave varies 

 from 4 db per mile to 0.64 db per mile over the frequency range from 

 30,000 to 100,000 mc. The higher order circular electric waves have 

 somewhat more attenuation but may be found useful as auxiliary trans- 

 mission channels for short distances. 



It is interesting and important, as will be pointed out later, to note 

 that several of the higher order transverse electric waves have attenu- 

 ation constants which may be within a factor of 3 to 6 times the attenu- 

 ation for the circular electric wave. These waves, TE12 and TE13 , have 



