RADL\TION CHARACTERISTICS OF AN ANTENNA. 



249 



meters, say). To solve this problem, it is only necessary to look up 

 the four ohm point on the different 7-curves of Figures 14 or 15, and 

 find the corresponding value of X/Xo. We can then find the Xo of the 

 antenna, since X is given. Dividing the Xo by 4 we obtain the total 

 length of antenna. The value of 7 gives the fractional part of this 

 length which is to be horizontal. The complete result is tabulated 

 in Table IV. 



TABLE IV. 



Constants of the Different Antennae that have 4 Ohms Resistance at 



2000 Meters. 



The question as to which of these antenna to choose for the given 

 purpose is now chiefly a problem in economics. The economic ciues- 

 tion is, which, for example, is cheaper: Two poles or towers 93 meters 

 high and 372 meters apart, or one tower 198 meters high? This 

 of course pre-supposes that it is designed to use a flat-top antenna 

 instead of some other type, such as an umbrella. 



The problem is, however, not wholly economic because the lower 

 antenna would he preferable as a receiving antenna on account of its 

 weaker response to atmospheric disturbances. There is also the 

 further question as to which of the tabulated antennae will give the 

 greatest vertical intensity of electric and magnetic force on the horizon 

 at a distant receiving station. This is the subject matter of the 

 next Part (Part V). 



