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BELL SYSTEM TECHNICAL JOURNAL 



for the slowly varying waves with which we deal, we will always consider 

 If as a real number. 



The gap factor for some other physical arrangements is of interest. At a 

 distance y above the two-dimensional array of strip electrodes shown in 

 Fig. 4.30 



sM^)^. 



(4.71) 



Fig. 4.30— A series of slots dg radians long separated hy walls L long. 



Fig. 4.31 — A system similar to that of Fig. 4.30 but with the addition of an opposed 

 conducting plane. 



If we add a conducting plane a at y = //, as in Fig. 4.31, 

 ^ ^ sin ieg/T) sinh y{h - y) 



(ei/2) 



sinh yh 



(4.72) 



For a symmetrical two-dimensional array, as shown in Fig. 4.32, with a 

 separation of 2 /; in the y direction and the fields above equal to the fields 

 below 



M = 



sin {Og/2) cosh yy 



(4.73) 



{dg/2) cosh yh 



4.5 Effective Field and Effective Current 



In Section 4.4 we have expressed a field component or ''effective field" 

 in terms of circuit voltage by means of a gap-factor or modulation coeffi- 



