RADIATION CHARACTERISTICS OF AN ANTENNA. 



209 



^' ^"^ I 3!2 " 5!4 ^ ^ 7!6 ^ 



p ..) 2=^ + 2^-4 ,, 



/?3 = lo -j ^j3 P 



42 + 2^-6 



A:* + 



(41) 



9 



ttXo 

 47ra 



(42) 



a = length of vertical part of antenna in same unit as X 



(e. g. meters), 

 p = radiated power in watts instantaneous value, 



I = -^ . (43) 



sin q/2 



where 



7o = amplitude of current at the base of antenna in amperes. 



11. Radiation Resistance of Vertical Part of the Antenna. 



— In equation (40) is given the power radiated from the vertical part 

 of the antenna, on the assumption that radiation from the horizontal 

 part of the antenna does not interfere with it. It will be shown later 

 in §14 et seq. how this interference is computed and allowed for. 

 Accepting for the present the assumption of non-interference, we may 

 obtain the radiation resistance of the vertical part of the antenna. 



The radiation resistance is defined as the time average of radiated 

 ■power divided by the time average of the square of the current at the base 

 of the antenna. 



In taking the time average of the power (40), it is to be noted that 



