INTERMITTENT BEHA VIOR IN OSCILLA TORS 



19 



phase characteristics shown in Fig. 23. The choice of this particular shape 

 is best explained by reference to Fig. 24 which presents the over-all envelope 

 loop transmission of the system. It is seen that the phase shift is relatively 

 constant at 90° over a wide band of frequencies and that the gain falls off 

 appro.ximately linearly over the same band. In particular the gain becomes 

 zero around 5000 cycles whereas the phase does not reach zero below 500, ()(K) 



40 

 80 

 120 

 160 



10 



100 1,000 10,000 100,000\ 1,000,000 



f-'N/SEC. 



Fig. 24 — Overall envelope transmission of Fig. 22. 



200.000 w 



100,000w 



Fig. 25 — Configuration of auxiliary filter. 



cycles. In terms of Nyquist's criterion this represents a very stable system 

 which is little disturbed by transient effects. A system having even greater 

 stability could be achieved by beginning the cut-off at lower frequencies. 

 It would then be found that the output was somewhat sluggish in reaching 

 a new equilibrium after being disturbed. Such a behavior is not uncommon 

 but is generally undesirable. 



Elements which give approximately the characteristics called for in Fig. 

 23 are shown in Fig. 25. The peak of loss at one megacycle is contributed 

 by the series resonant trap. The rest of the behavior is due to the 0.5 ni 

 condenser in combination with the associated resistors. 



