CONSTANT FREQUENCY OSCILLATORS 



91 



to be located in the grid leads instead of in the plate leads, a condenser 

 must be used. This may replace the conventional stopping condenser. 

 Where the reactance is in the plate lead for a similar type of oscillator, 

 the stopping condenser in the grid lead should be large so as to have 

 negligible impedance. Similar expedients are suggested for the im- 

 pedances of the other types of oscillator circuits. 



As typical of the general method whereby any of the simplified cir- 

 cuits of Figs. 1 to 18 may be elaborated into a conventional circuit of 

 this kind, including the various adjunctive circuits, Fig. 19 should be 



STOPPING 

 CONDENSER 



Fig. 19 — Practical arrangement of oscillator with three series tuned coupled circuits. 



referred to. This figure illustrates a complete wiring diagram of the 

 oscillator of Fig. 7 and shows an example of stabilization by means of 

 the inductance L5 in the plate circuit and the inductance L4 in the grid 

 circuit. In addition to satisfying the relation shown in Fig. 7, it may 

 be noticed that the value of L5 is such as to tune with Ci to the oscilla- 

 tion frequency, and, similarly, the value of L4 is such as to tune with 

 C2 to the oscillation frequency. Under such conditions a resistance of 

 appreciable value may be introduced into the circuit of L3 without 

 affecting the frequency of the stabilization. The reason for this may 

 be explained briefly as follows: 



Consider a single series circuit formed of one of the three meshes of 

 Fig. 19, for instance that composed of the elements, Tg, in parallel with 

 the 8000-ohm leak, La, and Co. This circuit is in series resonance at 

 the frequency at which the circuit as a whole oscillates. Therefore it 

 tends to introduce resistance impedance only into w^hatever circuits it 

 is reactively coupled with. Thus, the effect of this circuit upon the 

 adjacent circuit, L3, Ci, C\, with which it is coupled is to introduce 

 resistance only. Similarly, if this last circuit operates at series reso- 



