TRANSMISSION PROPERTIES OF CLOGSTON TYPE CONDUCTORS 701 

 4. ATTENUATION 



The attenuation of a transmission circuit at high frequencies, where 

 oiL^ R and o)C ^ G, is usually given in the following form: 



i/1+li/i' (7> 



where R is the total ac resistance of both conductors, L, C and G the 

 inductance, capacitance and leakance of the circuit. It will be assumed 

 that the insulation consists of polyethylene or some other material 

 having a very low^ leakance. Thus as a first approximation the second 

 term in (7) can be neglected. 



In a conventional coaxial cable, in the frequency range considered, R 

 will increase in proportion to the square root of frequency, so that 

 neglecting leakance, (7) may be written as follows: 



a=^VF^r (8) 



where Ki is a constant depending upon the dielectric constant of the 

 insulating material and the resistivity of the conductors. D is the 

 inside diameter of the sheath, and F^ac the frequency in megacycles. 



In the second part of this paper it is sho^vn that the attenuation of 

 Clogston I or II cables can be written in the following form: 



a. = ^' + K,wV,^, (9) 



where D = Over-all diameter of laminated cable. 

 w = Copper layer thickness. 



K2 and Kz are constants, different for Clogston I and Clogston II, 

 which depend upon the geometry of the cables, the dielectric constant 

 of the insulating material and the resistivity of the conducting layers. 



The first term in (9) gives a constant loss independent of frequency. 

 The second term contributes little to the attenuation provided w is 

 small enough. In fact, the attenuation mil remain constant within p % 

 of the first term provided: 



w 



= lor i^3 dfL' ^ ^ 



This equation (10) determines the copper layer thickness, which will 

 result in a "flat" attenuation within p per cent up to a frequency F, 



t 



c • 



