1446 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1957 



the zeros of the cosine shape occurred at the proper freciuencies, as ob- 

 served when the associated rheostat was set at maximum and minimum 

 positions, with all other rheostats set at midrange, or no-echo, setting. 



Some reflections were present in the main signal path as evidenced by 

 ripples in the gain characteristic when all rheostats were set at midrange, 

 corresponding to the "flat" loss condition. These reflections were reduced 

 to some extent by minor readjustments of the balancing screws on the 

 directional couplers. The over-all flat gain characteristic obtained after 

 these adjustments is shown on Fig. 12. 



This figure also shows the seven gain characteristics obtained when 

 each pair of rheostats is set for maximum gain. The markers on the refer- 

 ence trace correspond to the band edges. A sharp gain bump resulting 





M 



1.0 DB 

 _1 



P 1 



60 MC 80MC 

 FLAT GAIN 



jams. 

 /I 



._m 



FIRST TERM 

 f, = 40 MC 



IF 



/nnnm 



mm 



SECOND TERM 

 f^ = 20 MC 



THIRD TERM 

 f,= 13.33MC 



^■■k ^IBk ^BHk ^Hflk 



flffiiiin mmxm iBmiiBi pnRii 



mmmw wskkiw mmim mmism 



"^mKF HHV ^<VBr ^IBV^ 



FOURTH TERM 

 f, = 10MC 



FIFTH TERM 

 f5=8MC 



SIXTH TERM 

 f6 = 6.67MC 



SEVENTH TERM 

 f7 = 5.72MC 



Fig. 12 — Measured gain characteristics of equalizer. 



1.0 DB 



60 MC 80 MC 

 FLAT GAIN 



iBB: 

 «■ 



"If 



THIRD TERM 

 KNOB 3L ON STEP 11 

 KNOB 3R ON STEP 1 



jm 



A 



Wil 



Ml 



1 



FIFTH TERM 

 KNOB 5L ON STEP 11 

 KNOB 5R ON STEP 1 



Fig. 13 — Gain change introduced by changing delay terms from zero to maxi- 

 mum. Left, normal case. Middle, third harmonic term at maximum. Right, fifth 

 harmonic term at maximum. 



