414 PROPAGATION THROUGH THE STANDARD ATMOSPHERE 
(Figures 35 and 46), and we must find the value of 
lhe which corresponds to a known value of Hy (Fig- 
ure 47) for the appropriate value of Q = «,/60oi. 
From The, hy is found by dividing by I. 
If only one antenna height is less than 4/1, then de- 
fine 20 log A as 20 log A + 20 log 1 — 20 log H, for 
that antenna and hz then refers to the other antenna. 
C. Non-standard atmosphere. k # 4/3. The pre- 
ceding graphs are all based on k = 4/3. lf k 4/8, 
hy, he, d, and A should be replaced by hy’, he’, d’, and 
A’, where 
-1/3 
W=h (=) , 
-2/3 
1)” 
2/3 
va)" 
or 
3k? 
20 log A’ = 20log A + 20 log (2) (178) 
The change of h,d, A to the primed values can be 
made with the aid of Figure 43, i.e., if h,d are known, 
change to h’,d’, then Figure 37 will give A’, which 
in turn will give A’, and this with the aid of Figure 43 
will give A. 
_ D. Change to dimensionless coordinates. In the op- 
tical region, convenient coordinates are (see Section 
6.5) 
d d 
v= — oa 
V2Qkahy dr 
22 
hy 
For these coordinates, equation (175) becomes 
ee, (179) 
hug(e) 
Writing 
é = eh, 
s = sV2kah, wu) 
it follows that 
eh, = eu, 
sv = sd, 
and, using equations (150) and (159), 
Ss? = 2e. 
Consequently, Figure 37 can be_used with sv 
replacing sd, ew replacing ehz, and A is defined in 
equation (179). 
Caution: In using the graphs, care must be exercised 
when one or both antennas are elevated to see that the 
recewver antenna 1s well within the diffraction region, 
1.€., 
d>> d,. (181) 
for ae hata Si 
E d 20 log/ 3k\7 
io===10 o0(3)* 
= 3 fo) 4/3 
= 50 2 
40 
50 30 5 3 
40 20 4 
4 
5 
30 f 10 
s = 10 
10 
20 5 
2] A 
e iS 
20 
2] = 
3 I ! 
a 40 
= 50 
5 
= 
5 3 
5 25 100 
2 4 2 
4 
3 | 200 
3S 30 
300 
2 OS 
2 04 400 
03 5g 500 
02 
\ 1 1e00 
A] Ol 
Ficure 43. Relation of h,d to h’,d’ as a function of k. 
E. Illustrative problems; diffraction formula; di- 
electric earth. | Previously , four types of problems 
were considered for the optical-interference region. 
The same four types are given here, for a receiver 
below the optical-interference region. A dielectric 
earth is assumed so that the figures on pp. 413- 416 
are applicable. These require supplementing by 
equations (3) and (5). ° 
