702 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



By neglecting the second tenn in (9) and comparing the result with 

 (8) it can be seen that the attenuation of a conventional coaxial cable 

 and a Clogston cable are equal at a frequency given by: 





(11) 



The numerical examples given later in this paper indicate that a 

 Clogston cable will have higher attenuation than a conventional coaxial 

 cable at frequencies below F^c , and less attenuation at higher frequencies. 

 At frequencies sufficiently higher than F^c , the attenuation of a Clogston 

 cable will increase rapidly which is evident from the second term in (9) . 

 It is in the region between Fmc and frequencies where the second term 

 in (9) becomes important that Clogston cables can theoretically pro- 

 vide less attenuation than a conventional coaxial cable. 



5. IMPEDANCE, PHASE CONSTANT AND SPEED OF PROPAGATION 



The equivalent impedances of Clogston I and Clogston II cables are 

 developed in the second part of this paper and are equal to: 



(12) 



^" "" VL C Clogston II. 



In these expressions Lin, Lex and Cex are the internal and external 

 inductances and capacitances respectively. For conventional coaxial 

 cables they are discussed by S. A. Schelkunoff in * 'Electromagnetic 

 Waves" (Van Nostrand, 1943). For the Clogston analogy. Part II of 

 the present paper gives the reasoning adopted in defining them. In a 

 Clogston II cable the external inductance goes to zero and the external 

 capacitance to infinity, but the product LexCex nevertheless remains 

 constant. 



The impedance of a conventional coaxial cable, in the frequency 

 range considered, is given by: 



=/ 



I (.8) 



where L and C are the external inductance and capacitance of the con- 

 ventional coaxial cable. 



The equivalent impedance of a Clogston cable is lower than that of 

 conventional coaxial cable of the same outer diameter. Numerical eval- 



