36 



ANTENNAS 



Figure 29. Broadside arra}', elements perpendicular 

 to paper. 



n = 5 



d 



t\--9 



n=i3 



n = i7 



Figure 30A. Effect of arraj' length for broadside with 

 element spacing s = X/2. (From Radio Engineers' 

 Handbook by Terman.) 



where 



2'^ , 



a = — s COS (p. 



\ 



(26) 



For center-fed half-wave dipoles, from equation (3) 



Eel = 



607 



cos I — COS 6 j 



sin d 



(27) 



The patterns for the equatorial plane are illustrated 

 in Figiu-es 30A and 30B. Figure 30A shows the m- 

 crease in directivity with increasmg number of 

 elements. Figure 30B illustrates the effect of element 

 spacing on the production of side lobes. Figiu-e 31 

 gives the gain for various spacings and array lengths. 

 From this it appears that s = 5X/8 is approximately 

 the optimum spacing. 



Spacing 

 infinitely 

 close 



Spacing = A ([^ 



Telements 



6\ 



Spacing^^^ 

 5 elements 



Spacing = X 

 4 elements 



Figure .30B. Effect of element spacing for broadside 

 for array length L = 3X. (From Radio Engineers' 

 Handbook by Terman.) 



40 

 35 

 30 

 25 



20 

 15 

 10 



2 4 6 8 10 12 14 16 



Array Length In Wave Lengths 



Figure 31. Gain for broadside array of doublets as a 

 function of array length and spacing. (From Radio 

 Engineers' Handbook by Terman.) 



