DISTORTION CORRECTION 489 



since /i = I/2. Imposing this condition on the phase relation 



H = tan (5/2) = a^f, (74) 



there resulted 



2 tan-i (7/2/2) - tan-i H2 = - D,, 



which can be reduced to 



Ho 



4 + 3H2' 



= — tan Di, 



and the cubic in H2, 



Hi" + 3 tan DJL^- + 4 tan Pi = 0. 



(75) 



tS20 



Fretjuency (.cycles per second) 



15.000 



wpoo 



Fig. 18 — Attenuation characteristics of television circuit before and after distortion 



correction. 



The solution of the latter with Bx = — .111 radian gave here 



H<i = .89363, whence ay = i72//2 = .44681 •10-^ 



and in Fig. 17 



Li = 8.533 mh.; C2 = .01185 mf. 



For the purpose of showing the amount and precision of distortion 

 correction produced by the addition of these various networks to the 

 open-wire circuit under different weather conditions, attenuation and 

 time-of-phase-transmission characteristics are given in Figs. 18 and 

 19, respectively. The final results indicate that the design require- 



