840 



BELL SYSTEM TECHNICAL JOURNAL 



The gain of a uniformly excited endfire antenna^ with ^ — p \s 4p. For 

 13 9^ p, the gain can be written 



S = 4.4p. (2) 



5 

 <0.; 



? 60 



10 10 



DEGREES OFF AXIS 



60 + 



Fig. 3— Directional i)attcrns of a six wavelength (p = 6) continuous arra>-. 



The factor A is given graphically in Fig. 4 as a function of 1-k{§ - p), the 

 phase lag.* The highest gain occurs for a phase lag of approximately tt 

 radians relative to free space transmission, that is, for /3 = p + 0.5, in con- 

 formity with the patterns of Fig. 3. For a short radiator, ,1 is about 2; 

 with increasing antenna length, .1 approaches 1.8. 



^ SchelkunolT, loc. cit. p. 347. 



* Fig. 4 and ('(luation (5) were supplied by I>i 



H. T. Friis. 



