A . RADAR 



1. GENERAL 



Radar as used for navigation and position fixing is a system of deter- 

 mining distances by measuring the time -interval between the transmission of 

 pulses and the return of the corresponding echoes from primary targets . In 

 its use of the interrogation and reply method it is similar to such systems as 

 Shoran. 



Radar development began in England in the 1930's, and all of the more 

 recent types of pulse measurement systems evolved from this early work. 

 However, radar differs from the other pulse systems described herein in that 

 the reply is the wave reflected from the target point, and transponding or re- 

 transmitting equipment is not required to send back a reply. Thus, radar is 

 an entirely self-contained system suitable for multi-user application. Ranges 

 of from a few hundred feet to beyond the line of sight (200 feet -50 miles) and 

 range resolution of the order of 1 part in 1000 or better can be expected with 

 most classes of radar equipment. 



2. DESCRIPTION 



Radar systems consist of a transmitter, rotary antenna and switch, 

 receiver, ranging unit, plan -position -indicator display unit (PPI), and associ- 

 ated power supply. A typical system is diagrammed in Figure VI -1 . 





ANTENNA 









\ 



1 















TRANSMITTER 





SWITCH 





RECEIVER 





RANGE UNIT 



— 



PPI 



FIGURE VI-1 TYPICAL RADAR SYSTEM BLOCK DIAGRAM 



135 



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