﻿596 



Prof. J. A. Fleming on the Electri 



ic 



Table II. 



Bent transmitting antenna 3 feet vertical, 7 feet horizontal. 

 Straight receiving antenna (vertical) 10 feet high. 





Current in Receiving Antenna in 



Azimuth of 



arbitrary units. 



horizontal part 

 of Antenna. 











At 78 feet distance. 



At 138 feet distance. 



o 

 



100 



100 



15 



91 



94 



30 



96 



87 



45 



91 



76 



60 



81 



77 



75 



83 



67 



90 



81 



65 



105 



74 



60 



120 



7° 



52 



135 



70 



56 



150 



71 



57 



165 



71 



43 



180 



64 



50 



On the other hand, in the actual antennae the current 

 varies from a maximum at the earthed end up to zero at the 

 free end. The effect of this is to make the actual magnetic 

 moment of the bent oscillator less than would be the case on 

 the assumption of a uniform current in it. 



Suppose, however, we consider a small closed rectangular 

 circuit to be traversed by an oscillatory current of maximum 

 value I. Through the centre of the rectangle draw a line 

 parallel to one side and produce it both ways. Take points 

 a and b at equal distances r from the centre both on the 

 right and left-hand sides of the rectangle. Let H be the 

 maximum magnetic force at a and b perpendicular to the plane 

 of the rectangle, and E the electric force in the plane of the 

 rectangle and perpendicular to the bisecting line. Then it 

 can be shown that 



H = 



18,/S.; 



1S>/S.: 



\-m 4 7 A —-mrr-\-l 9 



where 8//, Bz are the sides of the rectangle and m = 2ir/\, 

 where A, is the wave-length of the radiation. 



These formula? can be arrived at on the principles explained 



