CALCULATION OF RADIO GAIN 
409 
FREQUENCY IN MEGACYCLES 
"FBO Noa 
‘a a 
e L 
015 aa 
Beh 
—|+- 
eg (8) 
a sea wren — | 
BEPZZ 
eA 
mers ies 
hg IN METERS 
BERIT ES 2] ES ABR Sas 
ol 
i 
Hil 250 
| | 
fo} 
Pena WAVELENGTH IN METERS 
Ticure 35. eg(5) versus wavelength or frequency. For dielectric earth e = 14hc and g(6) = 1. 
Pe 
ee ae 
VASE a es 
[ie Es a Eee 
| Ean eee 
“DeSe uae acm 
Cae eetsne 
EES: act aaa 
ia eae a ale | 
LAcIE EA a ee 
(i Ala cone ey 6 9 0 WW 1 
Figure 36. g andy versus ehg(6). 
standard atmosphere (k = 4/8), is given by 
| 
d= a(é a (Vin + Viz). (163) 
If 4/3 is changed to k, the more general form is 
dy! = V2ka (Vin + Vig). 
The first maximum will now be near 
fe 
=~—d 
4 oe 
Suppose next that the point at distance d,’ for the 
given heights was originally well within the diffrac- 
tive region. The exponential part. of the gain due to 
change of k from 4/3 is equal to 
(164) 
16078 (az'— dz) 
or 
e-1.607 (V3k/4 - 1)sdy,_ 
The above formula is obtained by combining equa- 
tion (149) for F,, and s is obtained from Figure 31 
(& = 4/3). This corresponding gain in decibels is 
20 logio e 1.607 (V3k/4 = 1)sa 
= 20| — 1.607 X a34(/2 3h 1) siz], 
au 14a, ( [3 us 1) db, 
below the free-space value. Since a maximum is now 
near dz’ as a result of changing 4/3 to k, i.e., the 
field has a value of 6 db above the free-space value, 
