TRANSISTOR OSCILLATOR FOR MULTIFREQUENCY PULSING 1325 



4 TIMES 

 NORMAL LOAD 



Fig. 8 — Effect of load and value of feedback resistance on the level of the output. 



permits some deterioration in transistor characteristics before the change 

 in output is sufficient to require readjustments. 



Variation in the absolute level of output due to variations in Va, (see 

 Fig. 3) between transistors and to differences in coils is taken care of by 

 the use of taps on the output windings. 



Harmonics of the fundamental frequency are created by the non- 

 linearity of the transistor characteristics. These harmonics are accentu- 

 ated by excessive feedback. The level of the harmonics for a representa- 

 tive transistor are shown in Fig. 9. 



The effect of variations in feedback on the frequency is shown in Fig. 

 10. The shift is thought to be due to several factors all small. One is the 

 lack of perfect coupling between the transformer windings. Another is 



1050 1000 950 900 850 800 750 700 650 600 550 

 EXTERNAL FEEDBACK RESISTANCE IN OHMS 



Fig. 9 — Effect of feedback on harmonics with normal load. 



