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BELL SYSTEM TECHNICAL JOURNAL 

 TABLE III 



-Vl^ 



/=°.V/i' 



/=».V/2'' 



=v^ 



-/«2V/r 



/^2-//2^ 



the location of the attenuation peaks of the network with relation to the 

 cut-off frequencies and are given by the expression : 



^"=Vf 



/^nW 



f^nVf2" 



n = I, 2, 3, 



where / 00 „ is the frequency of infinite attenuation. 



These tables give the design formulae for the networks of Figs. 8 and 

 12. To obtain the equations for a network having crystals in the 

 series arms alone, it is only necessary to let bs = 0. If one of the 

 peaks of the filter of Fig. 8 (a) is placed at infinity — which results when 

 ^2 = /2//1 — the two coils will have equal values and by the theorem 

 illustrated by Fig. 5 can be brought out to the ends of the filter, 

 simplifying the construction. In a similar manner if one of the peaks 

 of the filter of Fig. 8 (b) is placed at zero frequency, i.e. 62 = 1, the two 

 shunt inductances are equal and can be brought out to the ends of 

 the filter. The design equation of the narrow band filter of Fig. 12 

 with the lattice crystals replaced by condensers can be obtained from 

 Table III by letting 62 = 0. 



