192 



SITING 



Permanent echo diagrams are useful for: 



I . Indicating blind areas in a station's coverage. 



'2. Assigning the operating area of a station. 



3. Checking the range and azimuth accuracy. 



4. Checking the performance. 



5. Estimating nonstandard propagation. 

 G. Planning test flights. 



hills aie screened by a local obstruction. This local 

 echo at, say, three miles, is combined with the main 

 pulse or ground return and the distant echo is 

 weakened or eliminated entirely. 



Shielding causes a loss of coverage, which in 

 operating regions may be more serious than the 

 permanent echoes. Rear areas which are not scanned 



' 100 



SEA 



LAND 



Figure 8. A typical i)ermaneiit ei-lui diaKram for a VHF radar. 



10.4.3 



Shielding shoukl be well shielded so that back and side echoes 



The principal device in the field for the control of do not interfere ^^th targets in important tactical 



permanent echoes is shielding. This means that the regions. Operation over such shielded sectors would 



antenna must be sited in such a way that distant be limited to high targets. 



