GAS-DISCHARGE T RAN SM IT-RECEIVE SWITCH 



73 



which the reflected signal intensity varies as an object of fixed size approaches 

 a radar set from a great distance. Such an object as seen by a given radar 

 set may be represented on Fig. 25 by a straight Une having a slope of 12 db 

 per factor of two in distance. Several such lines are shown. Considering 

 line A it will be observed that this target can first be seen at a distance 

 corresponding to 12 microseconds. Since this target line always remains 

 below the TR recovery line for times shorter than that at the intersection 

 point, an object once seen will remain in view continuously as it approaches 



5 '2 



time: in microseconds 



Fig. 26— The recovery time characteristic at two different transmitter power levels for the 

 724B tube in a 1.5 db TR box 



the transmitter even in spite of the poor recovery characteristics of the TR 

 box. A certain amount of sensitivity-time-control action is actually pro- 

 vided. The recovery time characteristic frequently does not necessarily 

 set a lower limit on the effective range of a radar system although it always 

 sets a limit on the smallest effective target size which can be observed. 



The recovery time characteristic is critically related to the transmitter 

 output power level as shown by the data for a 724B tube shown in Fig. 26. 

 When the recover>' time curves for two different power levels are compared, 

 the target line which is just detectable at a power level of 11.4 kw is shown 

 as the line marked A Contrasting with the 721A behavior this target would 

 be visible only at one point and would then be lost from sight as it approached 



