Chapter 11 
SITING AND COVERAGE OF GROUND RADARS‘ 
INTRODUCTION 
[pa ISAGENERAL 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. 
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 
restrictions, and the terrain has little effect on the 
coverage. 
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 
71 
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 
coverage may be extended accordingly. The disad- 
vantages of outlying sites presented by communica- 
tion and supply difficulties, exposure to enemy 
attack, etc., should be carefully considered. More 
often, however, the success of the warning system 
depends on effective long-range operation of radars 
located relatively close to the defense area. The early 
warning stations give periodic reports of the grid 
position of an aircraft and its response to interro- 
gation signals. 
The GCI radar is used to direct from the ground 
®By Capt. E. J. Emmerling, detailed by Signal Corps to 
the Columbia University Wave Propagation Group. 
