138 



BELL SYSTEM TECHNICAL JOURNAL 



Since the principal axis of the antenna is nearly always directed 

 toward the distant transmitter, the conditions which will maximize the 

 above expression are of prime interest. The determination of these 

 conditions is greatly simplified by the assumption of a perfect ground. 



PLAN 



, _X_SIN(tt/3),_'^_t^P3 (3) 



NOTE — 



PHASES REFERRED TO POINT R 



FOR ELEMENTS © AND (5) AND 



TO RESPECTIVE SIDE APEXES FOR 



ELEMENTS (g) AND® 



T = Zo ^-^V^/ 



SIDE ELEVATION IN INCIDENT 

 PLANE OF WAVE-DIRECTION 



t ^t- 





Fig. 1 — Horizontal rhombic antenna dimensions. 



Fortunately this is not a radical assumption for the case of horizontally 

 polarized waves at the usual incident angles. This may be verified by 

 reference to Fig. 2 where the values of a and a are plotted for several 

 ordinarily encountered ground constants. 



