134 



COVERAGE DIAGRAMS 



■p = 0.1r?max/'rfr- The point of intersection of this line 

 with the selected Di-contour then gives the desired 

 p,q combination that corresponds to the given 

 A'alues of dniax and Di. 



From this pair of values (p,q), the corresponding 

 receiver height /12 may be calculated by the relation 

 [equation (98) in Chapter 5] 



/i2 = hi 



1 



1 - p= + 



1 -ryj 



220 



200 



**^ Construction of 



Path-Difference Loci 



An assumed value of in equation (12) determines 



6, the phase shift caused by the path difference, as 



5=9. + 2Trn, (18) 



where n assumes all integral A'alues and zero. This 



value of S determines the path difference A = ?■ — r^, 



A=^. 

 27r 



D=.99 



(19) 



D=.95 



Figure 5. Curves of constant-divergence factor D and path difference parameter R. (Radiation Laboratory.) 



Now both coordinates of the desired point are known, 

 and the point may be plotted. Plotting a series of 

 different points by the same method yields a smooth 

 cm-ve, which is the envelope of all lobe maxima. 

 The locus of minima may similarly be plotted by 



using sin- — = and 



rfmin = Vr,yo(l - D) 



(17) 



instead of equation (16). Intermediate range curves 

 are found by assigning nonintegral values to m in the 

 equation U = imr and substituting in equation (12). 



But from equation (97) in Chapter 5 



2/ii- 



2/ix2 (1 - p-y- 

 dT p 



dr 



9/(p) 



(20) 



where /(?;) is given in Figure 18 in Chapter 5. 



In tliis calculation, q may be taken as the inde- 

 pendent variable. The assumed values of q together 

 ■with A from equation (19) determine f(p) in equa- 

 tion (20). For given values of /(;;), the correspond- 

 ing values of p may be read from Figure 18 in Chap- 

 ter 5. The coordinate.s h^ and d on the path-diffei- 



