CALCULATION OF RADIO GAIN 
Free Space 
Radio Gain 
399 
iLele} 
50. 
5 
= 
f= 
= 
= 
1.5m (f= 200MC)| — 
30m 0 
200 
e 
1ooom p 
22.4 (13.5DB) a 
10 
5 
2 
Ficurer 26. Radio gain (in db) versus distance. 
radar set by echo from the target of cross section 
o = 10 square meters is to be calculated. 
Rapro Gain:OnE-Way TRANSMISSION (see Figure 26). 
1. The number r from Figure 15 in Chapter 6 or 
equation (115) is found to be 9.403. 
2. u = he/hy = 33.3. 
3. For r > 2 and n = 1, 7p is approximately equal 
to 1/r. Hence we start with p = 0.1. 
4. Equation (121), with p = 0.1 and u = 33.3, 
givesv = 2.76. 
5. From equation (112), R = 9.445, 
6. n = R/r = 1.005. Hence the target is on the 
first G.e., lowest) lobe. Moving in the direction of 
increasing distance, the target soon approaches the 
first maximum. To get points beyond, i.e., n. < 1, 
we need greater values of p but it is not necessary or 
desirable to go below about n = 0.8, since the curve 
beyond n = 0.8 is generally in the transition region 
in which the curve is more easily and more accurately 
obtained by joining the optical and diffractive curves. 
The diffractive part of the calculation is given on 
pp. 404-432.Accordingly, in Table 2, the values of p 
are taken only slightly above p = 0.1 (correspond- 
ing to n = 1) and are diminished to find points at 
the nearer distances. 
