842 



BELL SYSTEM TECHNICAL JOURNAL 



Exponential tapering comes about from heat losses and radiation losses 

 in the feed line. With attenuation a per wavelength, (1) becomes** 



2 cosh ap — 2 cos 27r(cos d — ^) 

 ay- + 47r2(p cos d - /3)2 



(5) 



20 25 30 



DEGREES OFF AXIS 



Fig. 5 — Effect of sinusoidal tapering of power upon directional characteristic of a six 

 wavelength continuous array. 



Feed line attenuation increases slightly the minor lobe amplitudes and tills 

 in the nulls. Exponential tai)ering caused by radiation can be reduced or 

 eliminated if the coupling of the radiating elements to the feed line is gradu- 

 ally increased along the line. 



4. The Polyrod Antenna 

 It has been found e.xperimentally that a suitably proportioned dielectric 

 rod can act as an efficient endtire radiator. A complete understanding of 

 * hoc. cit. 



