REFLEX OSCILLATORS 



637 



^" 



[-»- VORd J 



(GAP) 



Fig. 124.^A gap consisting of lined up grids. 





0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 



ra 



Fig. 125.— A factor used in obtaining the modulation coefficient of lined up grids vs 

 tlie wire spacing in radians, n is the fraction open. The curve for n = 1 also applies 

 approximately for a mesh grid. 



Suppose we average over the open space of the grid. If the grid is a frac- 

 tion n open, from (bl7) we see that the average over the open space will be 

 obtained by substituting for Go a quantity G{ya, n) given by 



G(ya,n) = {sinh (w7a/2)/(;i7c/2)}Go(7a) 



(b34) 



In Fig. 125, Giya,n) is plotted vs. ya for n = 1, .9, .8. This about covers 

 the useful range of values. It should be positively noted that the average 

 is over the open area of the grid and applies to current getting through. 



It remains to evaluate the factor/. Suppose x = 0. At the surface of 

 the grid wire, y = r, the radius of the wire, 



8V = (F(a/4x) In [2 (l - cos ^) = iV[a/2n) In [2 sin ^'1 



