GAIN OF DIRECTIVE ANTENNAS 



83 



Arrays Incorporating Both Horizontal and 

 Vertical Directivity 



The gains of arrays combining both horizontal and vertical direc- 

 tivity may not be simply calculated by adding the gains (expressed 

 in decibels) corresponding to elements arranged respectively along the 

 two principal coordinate axes. However, they may be calculated 

 except for earth effects by means of equation (26) below. Some cal- 

 culations of this kind have been made and the data are tabulated below. 

 They assume a total of 36 couplets which are arranged variously as 

 noted. In the first case all 36 couplets are arranged as a simple 

 horizontal array. The second case assumes that they are arranged in a 



TABLE II 



Fig. 20 — Approximate three-dimensional diagram. Linear antenna array 

 reflector. Aperture two wave-lengths by eight wave-lengths. 



with 



broadside rectangle two elements high and 18 elements wide. This 

 combination may be regarded as two arrays of 18 couplets arranged one 

 above the other. The third case similarly assumes three arrays of 

 12 couplets each. A separation between couplets of j4 wave-length 

 has been assumed throughout. The most economical arrangement of 

 such an array depends not only on the relative costs of real estate 

 and towers but also on feed-line losses and effects due to the proximity 



