RADIATION CHARACTERISTICS OF AN ANTENNA. 



211 



PART II. 

 Field due to horizontal Portion of Antenna. 



12. Introductory Notions. — To determine the electromag- 

 netic field and radiation characteristics of the horizontal flat-top 

 portion of the antenna, let the rectangular coordinates of any distant 

 point P (Fig. 7) be x, y, z. 



Figure 7. 



And let the coordinates of any point P' on the flat-top be x' , 0, a; 

 the coordinates of the image point P" be x' , 0, — a. 



Then the distance from the origin of coordinates to the distant 

 point is 



OP = To = V.r2 + T/2 ^ 22 



The distances of the distant point from the point on the flat-top 

 and its image respectively are 



and 



P' P ^ ,' = V(.T - x'y + ir- + (- - ay. 



P" p = r" = V(.r - .tT + ?/' + {z+aY 



Then r' - ro = V(.r - x'Y -f y' + (z - af - ^x^ + y' + z\ 



