r.tcuiM niir. oscii.i..ii()ns 



521 



ninililiriiim (■ur\i' lo (iciui in .1 purlioii nl ilic l.illtr w luic it .ip- 

 |in>.ulu's tlu- horizontal. It \\iiiil<l .ipiicu (loir.ililc, 1 lu'iclnrc. if 

 Irwiuency stabilitv' is to be pushed i" ilir liniii, in permit ,1 slight 

 phase displacement to occur in the aiiiplilur in mclci ili.ii ilu- inter- 

 section nn>;lu be located at a place where the aini)liliide e(|iiilil>rinni 

 ciir\e is sleeper. Any decrease in the slope of the phase e(iiiiiibriuni 

 cur\e will be more than compensated for !)>■ the increase in slope of 

 the amplitude cur\c. It will be apparent from the cur\-es that such 

 an adjustment reduces the amount of fre(|uency change accompanying 

 .u\y change in phase displacement at the expense of am[)litude sta- 

 l>ility. In practice, phase changes can be made smaller than trans- 

 mission gain changes and we are conse(|uentIy iiistified in placing 

 most of the burden of holding the fre<iuenc\' to ti.irrow litnit> on the 

 phase eiiuililirium characteristic. 



As a result of the foregoing analysis it appears that tlu- .unplitier 

 should be designed so that, at the normal operating point, its gain 

 \aries but little with load and so that it iniriuliiris as small a phase 

 shift as [Kjssible. The tuned circuit should li.i\i' little dam[)ing and 

 the \ariation in damping with load should be reduced to a minimum. 

 Although these conclusions ha\e been based upon the characteristics 

 of a s|)ecitic circuit. the\' a()pK' e(|uall\' well lo other circuits of the 

 same general form. 



I^ICSIC.N OF C'lRcriT KOK Hk.II I'RI-nt !• N( V ST.MUI.irV 



The arrangement of an oscillating circuit eiub<)d\ing the features 

 which the preceding section has shown to be essential, if the gener- 

 ated current is to be maintained within narrow fre(;iuenc\- liruits, 

 is gi\en in Fig. S. Ttu' frequeiHA control unit is a shunt resonant 



Fig. 8 — Circuit of cunstaiit frci|uc-iicy oscillator 



