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BELL SYSTEM TECHNICAL JOURNAL 



be in effect severed as far as the electromagnetic wave is concerned, and any 

 excitation in the outi)ut will be due to the a-c velocity and convection current 

 of the electron stream which crosses the lossy section. 



We will first idealize the situation and assume that the helix is severed 

 and by some means terminated looking in each direction, so that the voltage 

 falls from a value V to a value in zero distance, while v and i remain un- 

 changed. 



We will consider a case in which b — d = Q = 0, and in which a voltage 



0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 



d 

 Fig. 9.5 — Suppose that the circuit loss parameter changes suddenly with distance 

 from to (i or from d to 0. Suppose there is an increasing wave only incident at the point 

 of change. How large will the increasing wave beyond the point of change be? These 

 curves tell (6 = gc = 0). 



V is applied to the helix iV wavelengths before the cut. Then, just before 

 the cut, 



and 



(jUoC/ri)vi = Vi/8i 



(-2VoC'/h)h = V,/8l 



etc. 



(9.19) 



(9.20) 



