REFLEX OSCILLATORS 



567 



In addition to improving the electronic tuning characteristics the design 

 was found to be more stable against variations in load, as would be ex- 

 pected from the discussion of Section VIII. 



The arrangement adopted provided a prototype electron optical system 

 which was used in a whole series cf reflex oscillators designed for radar and 

 communication systems. These tubes were the 726A, 726B and 726C, 

 2K29, 2K22, 2K23 and 2K56. 



The output line of these tubes is intended to couple through an adapter 

 to either a coaxial line or a wave guide. In the first case the adapter serves 

 to couple the output line of the tube to the cable, in some instances through 



120 130 140 



NEGATIVE REPELLER VOLTAGE 



Fig. 66. — Use of the electron optical system shown in Fig. 65 eliminated the bad fea- 

 tures of the repeller characteristics of the earlier 1349XQ in which the electrons were re- 

 turned to the repeller region and gave the repeller characteristic of the final 2K29 

 (dashed line). 



an impedance transformer and in some instances directly. As practice 

 developed it became standard to design for optimum oscillator output 

 characteristics with output line coupled to a 50 ohm resistive impedance. 

 In the second case the adapter serves to couple the tube output line to the 

 guide through a transducer. 



A t>'pical example of a reflex oscillator incorporating this construction 

 is the 2K29. This tube is intended to cover the frequency range from 3400 

 to 3960 Mc/s. An external view of this tube is shown in Fig. 67. It will 

 be observed that the center conductor of the output line extends beyond the 

 polystyrene supporting bushing. Fig. 68 shows an adapting fitting which 



