690 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1954 



undriven wave has a smaller attenuation coefficient than the driven 

 wave, "How much less is the undriven line wave amplitude than would 

 have existed at the same value of x if the same incident wave had been 

 launched in the lower loss line and in the absence of coupling to the 

 higher loss line?" This amphtude difference for the condition 

 (ai — a-2)/c = 1 is represented in Fig. 28 by the difference between the 

 cur\-e for E-/* and the curve labeled 20 log e". Similarly, for the condition 

 (ai — a2)/c = 2, this amplitude difference is represented by the difference 

 between the curve for £2** and the curve labeled 20 log e ". 



The general case of 71 ^ 72 is important both in interpreting undesired 

 mode coupling effects in multi-mode systems as well as in e\'a]uating 



-40 

 -30 



-0.6 

 -O.S 

 -0.4 



-0.1 

 -0.08 



-0.06 

 -0.05 

 -0.04 



10 



I 2345678 



CX IN RADIANS 



Fig. 29 — Driven and undriven line wave amplitudes versus ex with (ai — a2)/c 

 0.03 and (/Si - 02)/c = 0.5. 



