COVERAGE DIAGRAMS 435 
VERTICAL 
COVERAGE OIAGCRAM 
ANTENNA HEIGHT 
73.4 WAVELENGTHS 
FOR 106mc 
hy HEIGHT IN KILOMETERS 
d@ DISTANCE IN KILOMETERS 
Fieurt 2. Vertical coverage diagram. 
the lobe from the polar sine formula [equation (11)]. 
On the other hand, the shape of the contour is of 
great importance when there are few lobes and the 
null area is large. This is illustrated in Figure 3, 
Where there are only two complete lobes in the 
region of interest. 
The second point to be noted is the varying effect 
of divergence on the lobe number and angle. It 
may be seen from equation (89) in Chapter 5 that 
the divergence factor approaches unity as tan y 
hg HEIGHT IN KILOMETERS 
a 7 fi AS 
2 Sa 
increases (see also Figure 11). The divergence 
factor is low for small angles and then approaches 
unity rapidly. This accounts for the reduced range 
of the first three lobes of Figure 2. For the larger 
angles, the maximum range is approximately equal 
to twice the free-space range. When the ratio h;/) is 
small, the angle at the first lobe maxima is large, since 
y = nd/4hy. In this case, the effects of divergence 
will be negligible except for the lower part of the 
first lobe, and the polar sine function derived for the 
ANTENNA HEIGHT 
ae ‘“ 
32.3 WAVELENGTHS 
FOR 106 MC 
b= 91.4m 
s Lal 
A= 2.83 
HORIZONTAL 
POLARIZATION 
2° 72° 
1%" 
VERTICAL 
COVERAGE DIAGRAM | 
d DISTANCE IN KILOMETERS 
Ficure 3. Vertical coverage diagram. 
