THE RADAR RECEIVER 



725 



The single-cavity velocity-modulated oscillator is admirably suited to 

 electrical remote control of its oscillation frequency by means of the potential 

 applied to the repeller element, thus lending itself to automatic frequency 

 control in a simple manner. Figure 19 indicates the frequency and power 

 output versus repeller voltage characteristic of a typical 2K25 10,000-mc 

 reflex oscillator when operating at a normal mode previously shown in 

 Fig. 18. It is customary to define the electronic tuning range of a reflex 

 oscillator as that range of frequencies over which the power output exceeds 



54 



o 



ELECTRONIC 

 TUNING IN ' 

 MC/SEC= 90 



A l/K 



z^ 



n\ 



20 40 60 60 100 120 140 160 180 200 220 240 260 280 300 320 

 NEGATIVE REPELLER VOLTAGE 



Fig. 18. — Typical output power modes vs. repeller voltage for a 2K25 type reflex 

 oscillator. 



50% of the maximum power output. The tube whose characteristic is 

 illustrated in Fig. 19 would accordingly have an electronic tuning range 

 of 53 mc. 



2.16 Typical Radar Input Circuit Designs 



An example of a radar receiver input circuit operating in the 1000-mc 

 frequency range is shown in its final mechanical form in Fig. 20. This 

 particular design was employed in several military ground radar systems 

 including the Mark-20 Searchlight Control equipment of Fig. 1, and in modi- 

 fied form in several naval fire control systems. It consists of two stages 

 of radio-frequency amplification, a converter stage, and a local beating 



