COVERAGE DIAGRAMS 4A7 
1930 =10 =100 =90 =80 =10 =60 =30 
20 LOG A—20L0G A 
Figure 14. Values of dy as functions of h; and 20 log A 
—20 log \. (See equation 56. The letters refer to cover- 
age diagrams plotted in Figures 16 to 39.) 
1, 2,--- , 11, 12 in Figures 16 to 39, with the chart 
number being given by Figure 15. 
Use of Charts 
The charts given in Figures 16 to 39 may be used 
for drawing coverage diagrams where the reflection 
coefficient is assumed equal to —1 and when the 
directivity factor F2/Fi is equal to unity. Hach 
chart may be used for values of r near that for 
which the chart is drawn. For intermediate values, 
interpolation between charts is necessary. Errors 
inherent in interpolation limit the accuracy attained 
On each chart are complete lobes or lobe out - 
lines labeled A, B, C,---, M, N. In the follow 
ing description these letters are referred to as lobe 
letters and the numbers 1 to 12 as chart numbers. 
Hach chart is plotted to two scales. 
The problem of constructing coverage diagrams 
resolves itself into finding the chart number and lobe 
letter corresponding to given values of gain factor A, 
transmitter height 4;, and wavelength \. As stated 
in previous text the basic parameters of the general- 
ized coverage diagrams are R and do or r and do. 
The value of r is given in Figure 15 as a function of 
and hy. Figure 15 was constructed from equation 
(51) which, after the substitution of numerical 
values, becomes: 
1030 4 
r= Tae (iors = 4), (59) 
The value of r determines the chart number. The 
lobe letter is found from the do corresponding to the 
given gain factor, transmitter height, and frequency. 
Figure 14 gives the lobe letters A, B, C,---, M, N 
as functions of 20 log A — 20 log ) and the trans- 
mitter height. The relationship for plotting these 
lines is given by equation (56). 
As an illustration of the use of the generalized 
coverage diagrams, assume 20 log A = —83, hy = 
33 meters, and f = 200 mc (A = 1.5 meters). If a 
straight line is drawn connecting h; = 33 and = 1.5 
in Figure 15, it will intersect the r scale at r = 8. 
Thus the chart number is 5. Now the lobe letter 
to be used in chart 5 must be found. For this case, 
20 log A — 20 log \ = —86.48. The coordinates 
20 log A — 20 log \ = —86.48, and h; = 33, de- 
termine the lobe letter to be H in Figure 14. Figure 
24 shows lobe E on chart 5. The first lobe is shown 
completely, together with the lower half of the second 
lobe. It must be noted that the coordinates of these 
charts, v = d/dr and u = he/h, are dimensionless. 
To convert to height hz and range d, the vertical 
distances must be multiplied by h; and the hori 
zontal distances by dy. In this case hi = 33 meters 
and dr = V2kah, = 23.6 km. The actual coordi- 
nates of the position of maximum range are hz = 
375 X 33 = 12.4kmandd = 15.4 X 23.6 = 365 km. 
Wiaure 15. Chart number and 7 as a function of \ and hy. (See Figures 16 to 39.) 
