TRANSMISSION PROPERTIES OF CLOGSTON TYPE CONDUCTORS 703 



uations using the above formulas indicate an impedance of about 23 

 ohms for a half -filled Clogston I cable, and about llj^ ohms for a 

 completely filled Clogston H cable, assuming polyethylene insulation 

 with € equal to 2.3 and copper conducting layers having a thickness 

 twice that of the insulating layers {wit = 2). These values compare 

 with about 76 ohms for a conventional coaxial cable having air dielectric 

 and the same outer diameter and 51 ohms for a corresponding coaxial 

 with soHd polyethylene dielectric. 



The phase constants of both Clogston cables in the frequency range 

 where the attenuation is nearly flat, are equal and independent of the 

 geometry of the cables. They are given by: 



iSi = ^11 = WL^C^\ (14) 



assuming uniform layer thicknesses. 



For a conventional coaxial cable the phase constant, neglecting leak- 

 ance, is given approximately by: 



^ = coVLc[l-i(2-^)]. (15) 



The computed speed of propagation, which is equal to co//?, is about 

 71,000 mi/sec for Clogston cables with polyethylene insulating layers. 

 This compares with 123,000 mi/sec for a conventional coaxial cable 

 with polyethylene insulation and 186,000 mi/sec for a coaxial with pure 

 air dielectric. 



6. COMPARISON WITH A CONVENTIONAL COAXIAL CABLE 



To illustrate the effect of the various parameters involved in the 

 attenuation of a Clogston cable, and to compare the result with a 

 convential coaxial cable, a few numerical examples have been evaluated. 



A one-half filled Clogston I and a completely filled Clogston II have 

 been selected arbitrarily for comparison purposes. Fig. 4 shows the 

 attenuation characteristics of these cables for several values of copper 

 layer thicknesses. In each case, polyethylene insulation (e = 2.3) is 

 assumed, with w/t = 2, i.e., the insulating layers have one-half the thick- 

 ness of the conducting layers. In the same figure, the attenuation charac- 

 teristics of two conventional coaxial cables of the same outer diameter, 

 one with air dielectric and one with polyethylene insulation, are shown 

 also. The regions where Clogston cables have in theory less attenuation 

 than conventional coaxial cables of the same outer diameter can be 

 seen in this figure. 



