REFLEX OSCILLATORS 



471 



is increased, the radio-frequency electron current gradually increases until a 

 maximum value is reached, representing as complete bunching as is possible, 

 after which the current decreases with increasing gap voltage. The maxi- 

 mum value of the current is approximately the same for various drift times, 

 but occurs at smaller gap voltages for longer drift times. 



The radio-frequency power produced is the voltage times the current. 

 As the given maximum current occurs at higher voltages for shorter drift 



POWER DISSIPATED X 

 CIRCUIT AND LOAD/ 

 / 

 / 

 / 

 / 



Q^S 



RADIO-FREQUENCY GAP VOLTAGE, V' 



Fig. 6. — Radio frequency electron convection current / and the radio frecjuency power 

 given U]3 by the electron stream can be plotted vs the radio frequency gap voltage V for 

 various drift times measured in cycles. Maximum current occurs at higher voltage for 

 shorter drift times. For a given number of cycles drift, maximum power occurs at a 

 higher gap voltage than that for maximum current. If the power produced for a given 

 drift time is higher at low voltages than the power dissipated in the circuit and load 

 (dashed curve), the tube will oscillate and the amplitude will adjust itself to the point at 

 which the power dissipation and the power production curves cross. 



times, the maximum power produced will be greater for shorter drift times. 

 This is clearly brought out in the plots of power vs. voltage shown in Fig. 6. 

 The power dissipated in the circuits and load will vary as the square cf 

 the radio-frequency voltage. Part of this power will go into the load coupled 

 with the circuit and part into unavoidable circuit losses. A typical curve 

 of power into the circuit and load vs. radio-frequency voltage is shown in 

 Fig. 6. Steady oscillation will take place at the voltage for which the power 

 production curve crosses the power dissipation curve. For instance, in 

 Fig. 6 the power dissipation curve crosses the power production curve for 



