Chapter 10 
SITING 
GENERAL 
ITING REFERS to the selection and utilization of 
local terrain features which affect propagation 
and the performance of equipment. From a pre- 
liminary analysis, the general location, type of 
equipment, and height may be determined. The 
specific sites available may, however, profoundly 
alter performance-in several ways. Careful analysis 
and tests may then be necessary to determine the 
best use of the facilities at hand and for an under- 
standing of the limitations due to the terrain. 
Siting Requirements 
With communication equipment, the siting prob- 
lems are principally concerned with visibility and, 
in wooded areas, absorption by vegetation. When 
siting direction-finding equipment, it is important 
to realize that reflections from mountains or other 
irregularities may cause serious angular errors which 
should be avoided by proper choice of the location. 
Both direction-finding and radar equipment require 
orientation. 
Radar siting requirements are rather different and 
depend on whether ground reflection is of importance 
or not. The siting of radars operating mainly on 
the direct ray is relatively easy and is principally 
concerned with permanent echoes and visibility. 
The most exacting site requirements are presented 
by the VHF early warning and height-finding radars, 
which to a large extent depend on ground reflection 
for successful operation. The siting problem then 
requires the consideration of terrain effects such as 
limited reflection areas, cliff edges, obstacles, etc., 
which involve diffraction problems of considerable 
complexity. Recommendations for specific sets are 
given in instruction manuals furnished with the 
equipment. 
TOPOGRAPHY OF SITING 
Profiles 
Radar ana direction-finding systems, which may 
cover a large area and involve many services, use a 
grid for plotting purposes. The grid location, height, 
and orientation of each station must be known with 
reasonable accuracy. Topographic maps of a scale 
of one or two miles to the inch and contour intervals 
of not more than 100 feet, preferably 20 feet, should 
474 
be secured. These may be supplemented by aerial 
photographs and surveys. 
In a complicated terrain, it is usually necessary to 
have profiles on several azimuths to determine the 
effective height above the reflecting surface. The 
accuracy required decreases with the distance from 
the transmitter. In most cases sufficient detail is not 
available on maps, so that a personal inspection of 
the terrain should be made to become familiar with 
the nature of the soil and degree of roughness. 
Special attention should be given to ridges, flat 
areas, bodies of water, distance to the shore, hills 
to the rear, obstacles in the operating area and 
at the boundaries. 
Where long distances and directive beams are 
involved, fairly accurate orientation of the order of 
one-half degree is required. Care must be taken when 
using compasses because of local attractions or 
inadequate information on declinations. Observa- 
tions on Polaris give the greatest precision but this 
star is not always visible and it is often inconvenient 
to use a transit at night. Caution must be used in 
aligning on permanent echoes, as they may be diffi- 
cult to identify. In general, several methods should 
be used to obtain independent checks. 
Solar azimuths, correct to the nearest quarter of a 
degree, may be determined from the date time to the 
nearest minute, and the latitude and longitude to 
the nearest degree. Two methods will be given for 
obtaining the azimuth of the sun: (1) by calculation, 
(2) from tables. 
The azimuth of the sun may be calculated from 
the formula, 
tan B = — eu iD) 5 (1) 
cos¢ tan 6 — sing cos (HA) 
= bearing of the sun. The bearing is east or 
west of south when ¢ — 5 is positive. 
The bearing is east or west of north when 
o@ — 6 is negative. The bearing is east 
in the moming (6 will be negative) and 
west in the afternoon (8 will be positive). 
hour angle of the sun. During the morn- 
ing hours when the hour angle is greater 
than 12 hours, its value should be sub- 
tracted from 24 hours for use in the 
formula. 
latitude of the place of observation. 
declination of the sun at the time of 
observation. The signs of @ and 6 are 
important and each is positive when 
north of the equator and negative when 
south. 
where B 
HA 
o & 
