Chapter 6 — RADAR \ND SATELLITE EQUIPMENT 



TRANSMITTER 

 PULSE • 



ECHO 

 PULSES 



SWEEP LINE 



PRECIPITATION 

 ECHOES 



FACE OF 

 TUBE 



SCALE OF MILES 

 ENGRAVED ON TRANS- 

 PARENT OVERLAY 



210.362 

 Figure 6-1. — General appearance of A-type scan 

 presentation as it would appear on the range in- 

 dicator CRT. 



R-Scan Presentation 



The R-type scan is almost identical to the 

 A-type. The difference between the two is that 

 the A-scan presentation displays the total range 

 starting at range and ending at any one of 

 several ranges selected; the R-scan presenta- 

 tion isolates a portion of the range scale and 

 expands it. 



PPI-Scope 



Another type of display commonly used in 

 radar is termed Plan Position Indicator (PPI). 

 This display makes it possible to read range 

 and bearing information simultaneously. A dia- 

 gram of a basic PPI-scope is shown in figure 

 6-2. 



RANGE 

 MARKS 



Figure 6-2.- 



AZIMUTH 



INDICATOR 



SCALE 



210.383 

 •Diagram of PPI-scope. 



In essence, with the PPI-scope, the sweep 

 starts at the center of the tube instead of at 

 one edge as it does on the A-scope. As the 

 antenna rotates around a 360° circle, the sweep 

 rotates simultaneously. The intensity of the 

 sweep display is modified by the presence of 

 a return signal. Thus, the position of a target 

 is indicated at the correct azimuth and range 

 by a bright spot on the display tube. A map- 

 like picture is thereby produced on the tube as 

 the antenna rotates in the ai'muth plane. 



RHI-Scope 



The Range Height Indicator (RHI) is another 

 scope found on radar equipment. Its function 

 is not unlike that of the PPI except that when 

 this scope is used, the azimuth of the antenna 

 is kept fixed while the antenna moves from view- 

 ing at 0° elevation to a predetermined elevation. 



Range Markers 



Each of the conventional scopes provides for 

 some direct indication of range by display of 



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