WIDE-BAND TRANSMISSION OVER COAXIAL LINES 659 



ably little effect on the attenuation. In order to study the effect of 

 eccentricity upon the attenuation, tests were made in which this effect 

 was much exaggerated, and the results substantiated theoretical pre- 

 dictions. The impedance of the circuits was measured over the same 

 range as the attenuation. A few measurements on a short length 

 were made at frequencies as high as 20,000 kilocycles. 



SPACING OF INSULATORS 



Fig. 3 — Structure used in Phoenixville installation. 



Measurements were secured of the shielding effect of the outer con- 

 ductor of the coaxial circuit up to frequencies in the order of 100 to 

 150 kilocycles, the results agreeing closely with the theoretical values. 

 Above these frequencies, even with interfering sources much more 

 powerful than would be encountered in practice, the induced currents 

 dropped below the level of the noise due to thermal agitation of elec- 

 tricity in the conductors (resistance noise) and could not be measured. 



The preliminary tests at Phoenixville, therefore, demonstrated that 



