STANDING- WAVE ANTENNAS 



29 



determined by the extra distance [(X/2) cos 6] The radiation patterns for various values of n are 



which it must travel. The radiation field is then plotted in Figure 14. Table 1 gives the radiation 



equal to the radiation field of one half -wave element resistances, relative lengths of major lobes, and the 



(as a function of angle 9) multiplied by the vector gains, with comparative figures for the doublet and 



kCl 



1.0 



n = l 



n=3 



n = 4 



n = 5 



resultant for the n elements. Thus 



X 



6.0 



n = 6 



Figure 14. Cophased half-wave dipoles (relative fields). 



the multi-half-wave antennas of Section 3.2.5. 



[e'° + e'" + e'-" + + + e^'""""] 



^■" Effects of Finite Diameter 

 on Center- Fed Linear Antennas 



to 



X 



o 



UJ 



u 



z 

 < 

 t- 

 u 

 < 

 111 



QC 



sm 6 

 5000 

 4000 

 3000 

 2000 



1000 





 -1000 



-2000 

 -3000 

 -4000 



-50 00 



(18) Figure 15 shows the input reactance, and Figure 16 

 the input resistance of a center-fed antenna of 

 arbitrarj' length. The input impedance is a series 

 combination of the two components. The important 



X/4 



X/2 



3X/4 X 5X/4 



HALF-LENGTH OF ANTENNA 



Figure 15. Reactance at input of a center-fed antenna of arbitrary length. 



