TEE RADAR RECEIVER 



729 



converter is similar to a form described in a previous section. The signal in 

 this example is introduced into the converter section of the waveguide 

 through an iris following the TR tube. Two 2K25 reflex oscillator tubes 

 are mounted upon this waveguide with their output probes extending into 

 the guide proper. The crystal cartridge is located near the end of the wave- 

 guide with an adjustable piston terminating the guide. A waveguide to 



_iH(-' 



R-F 

 AMPLI- 

 FIER 



jHh' 



jH(- 



T 



_jHH 



-ORJir- 



Fig. 22. — 1000-mc Radar Receiver Input Circuit. Schematic diagram. 



coaxial transforming section employs the crystal as an extension of its axial 

 element with an adjustable capacitance element for tuning purposes. 



It will be observed here that a shutter is included in this design, whereby 

 the crystal element can be isolated from the signal input end of the wave- 

 guide. This is a most necessary device on all radar converters employing 

 crystal converter elements to prevent accidental overload of the crystal. 

 When the transmitter is not in operation and accordingly the TR tube "keep 

 alive" is not energized, there is a possibility of subjecting the crystal element 

 to signals of sufficient amplitude to destroy its characteristic. These over- 



