REFLEX OSCILLA TORS 



S43 



Such noise or noise "sidebands" can be produced by any mechanism which 

 causes the parameters of the oscillator to fluctuate with time. As the mean 

 speed, the mean direction, and the convection current of the electron flow 

 all fluctuate with time, possible mechanisms of noise production are numer- 

 ous. Some of these mechanisms are: 



(1) Fluctuation in mean speed causes fluctuation in the drift angle and 

 hence can give rise to noise sidebands in the output through frequency 

 modulation of the oscillator. 



90 



u uj 50 



LU 



o 



UJ UJ 



2z 



- 



(> • 



• 



/ \ • 



•\ 



20 



0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 ' 



RELATIVE FREQUENCY, W 



Fig. 55. — Computed variation of electronic tuning range in megacycles vs relative 

 frequency W. The curve is calculated from the same data as that in Fig. 54 with no 

 additional adjustment of parameters. Points represent experimental data. 



(2) If the drift field acts differently on electrons differently directed, 

 fluctuations in mean direction of the electron flow may cause noise sidebands 

 through either amplitude or frequency modulation of the output. 



(3) Low frequency fluctuations in the electron convection current may 

 amplitude modulate the output, causing noise sidebands, and may frequency 

 modulate the output when the oscillator is electronically tuned away from 

 the optimum power point. 



(4) High frequency fluctuations in the electron stream may induce high 

 frequency noise currents in the resonator directly. 



Mechanism (4) above, the direct induction of noise currents in the reso- 

 nator by noise fluctuations in the electron stream, is probably most impor- 



