l.tCriM TLHI-. (JVC //./..•/ /OW.V 517 



ill ilu- other family dt'tine pairs of valiit's of tin- frf(|uenc-y and of tht- 

 ()owrr at thf rfftTfiirf junction for wliich \hv systi-m is in phaM" 

 i'(|iiilil)riuni. 



Thf relations In'twivn these two (|u,ii)titii's frfiiuenr\' and power — 

 may be expressed I)y two curves, one indicating the values necessary 

 for enerjj>' e()uilil>rium, the other indicating the values necessary for 

 phase e(|uiiil)rium. The intersections of these curves correspond to 

 the only v.ilues meeting both conditions. The se\eral elements 

 must, therefore, adjust themselves to operate at tlu- freciuency and 

 at the [K)wer indicated by such an intersection. 



MfKI-.i T OF \'.\RI.\TI()NS IN ClRl IH Kl.KMICNTS 



In addition to determining the fre(iuenc\' and power at which a 

 given system is in stable equilibrium, it is important to be able to 

 predict the effect upon these quantities of such changes as may be 

 e.xpecti-d to occur in the elements composing the s>stem. It is then 

 a relatively simple matter to so redesign these elements that some 

 jxirticular effect shall be reduced, or increased, as desired. The 

 circuit which has already been described may be used for illustrating 

 the application of the graphical method in answering some of the 

 questions occurring most frequentK- in connection with vacuum tube 

 oscillators. 



One of the more important (iroblems concerns the reaction on the 

 oscillating circuit of the load absorbing system. Let us imagine 

 that an impedance, to which energy is to be supplied, is connected 

 across the junction A. If this impedance is a complex quantity it 

 will alter both the amplitude and the phase of the voltage across the 

 junction. This will affect both families of cur\es — Figs. 5 and 7 — 

 which flefine the operation of the amplifier. If, for simplicity in the 

 present discussion, we assume the load impedance to be a pure re- 

 sistance, the inajor change will be a reduction in the voltage across .-1 

 for a given voltage across B. The ratio of the \oltage at B to that 

 at ,4 will be increased and the family of curves defining the power 

 ratio relations between frequency and power ratio in the amplifier 

 will thus be movetl upward. The reaction upon the energy e(|uilib- 

 rium curve — cur\'e A. F"ig. 6 — will be to decrease both its height and 

 its breadth. .Assuming that the phase equilibrium curve remains 

 unchanged, it is apparent that the frequency- at which the system is 

 in stable equilibrium will be increaseti and that the power delivered 

 to the junction .1 will be decreased. .Any change affecting the ampli- 

 fication of till' v.iiimm hibf circuit would react in much the sam',- w.iv. 



