RADIATION CHARACTERISTICS OF AN ANTENNA. 



195 



If there is no inductance, X = Xo, and the factor becomes 



2Trl 



J = 1 cos -r— . 

 \ 



(4) 



This is illustrated in (a). 



In the case with added inductance, X ?^ Xo, and we must keep the 

 general form of J given in equation (3). This equation for positive 

 values of / gives the upper half of the diagram (b). When I is supposed 



FiGUEE 2. 



negative the curves obtained continue along the dotted lines of (b) 

 and do not give a figure symmetrical with the upper half. To pro- 

 duce proper symmetry the absolute value of I must be employed in equation 

 {1) when it is applied to the distribution of the image to take account of 

 reflection. 



