Chapter 15 

 SITING AND COVERAGE OF GROUND RADARS a 



15.1 



INTRODUCTION 



This is a general discussion of the effects of terrain 

 on the operation of ground radar systems. Written 

 to supplement a Signal Corps publication Radar 

 Performance Testing, it is intended to provide a 

 practical, engineering type of solution of siting 

 problems. The principal emphasis is on early warn- 

 ing and other very high frequency [VHF] systems 

 although application may be made to microwave 

 and other types of radio equipment. 



The objective has been to enable field personnel 

 to compute coverage and other characteristics of a 

 given site and radar and reduce the number of test 

 flights required to a minimum. Thus the terrain 

 factors may be evaluated, and a definite, numerical 

 description of the capabilities of a site may be stated. 



Since it is not possible to anticipate all problems 

 that may arise in the field, sufficient theory has been 

 included to cover a fairly wide scope. In most cases 

 several types of solutions are provided so that the 

 accuracy and detail required may be related to the 

 labor involved. A number of fully worked examples 

 are included with a discussion of significant features. 

 The drawings are made to scale and to fit practical 

 situations. 



restrictions, and the terrain has little effect on the 

 coverage. 



15.2 



15.2.1 



RADAR SYSTEMS 

 Types of Ground Radar 



Tactical requirements and intensive technical 

 development have led to the introduction of numer- 

 ous types of ground radar equipment. The charac- 

 teristics and descriptions of these units are given in 

 several Service publications. 



Ground radars may be divided into two classes: 

 (1) those which utilize ground reflection; (2) those 

 which use only the direct ray. Sets which are sited 

 so that ground reflection influences their performance 

 usually have stringent siting requirements and the 

 coverage is dependent on the site. This report is 

 concerned chiefly with this type of radar. Equipment 

 that uses only direct rays is relatively free from site 



"By Capt. E. J. Emmerling, detailed by Signal Corps to 

 the Columbia University Wave Propagation Group. 



15.2.2 



Radar Systems — Tactical Aspects 



In most cases radar stations are operated in groups 

 for the defense of a region of considerable extent. 

 The several stations are assigned sectors in which 

 searches are conducted for designated targets, and 

 these, when located, are reported to a central agency 

 for tactical disposition. Technical operation of such 

 groups requires close study of the topography of the 

 region so that available equipment and personnel 

 may be used to the best advantage. In this way 

 adjacent stations may support each other in the 

 event of outage due to maintenance or enemy activ- 

 ity, and other factors may be taken into account, 

 such as jamming, atmospheric effects, and perma- 

 nent echoes. 



The nature of the region to be protected and 

 the type of application for which the radar equip- 

 ment is to be employed are controlling factors 

 determining the number, location, and kind of sets 

 which must be used. Thus, harbors, islands, and 

 inland mountainous regions present problems with 

 widely differing operational characteristics. Early 

 warning [CHL], fighter control [GCI], gunlaying 

 (coast defense), gunlaying (antiaircraft), and search- 

 light control radars all have different siting require- 

 ments. This report deals mainly with the first three 

 types of equipment listed above, but the methods 

 have general application to other problems such as 

 the siting of direction finding sets [DF]. 



The early warning radar usually has the mission 

 of reporting and identifying enemy aircraft (at say 

 20,000 ft) 45 minutes before they can reach the vital 

 defense area. This is based on the time required to 

 alert the area and to give the defense aircraft time 

 to take off and make their attack. Other missions 

 may be assigned, such as detection of ships or obser- 

 vation of friendly aircraft for purposes of control and 

 air-sea rescue. Using the moderate plane speed of 

 240 miles per hour it is apparent that the early 

 warning radar must have a range of 180 miles if 

 located near the defense area. Sometimes suitable 

 outlying sites, such as islands, are available, and the 



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