THEORETICAL INA^ESTIGATION OF THE RADIATION 

 CHARACTERISTICS OF AN ANTENNA. 



By George W. Pierce. 



Received May 6, 1916. 



1. Introduction. — For the proper design of a radiotelegraphic 

 transmitting station it is important to know the radiation charac- 

 teristics of different types of antenna. 



For example, if a flat-top antenna is to be employed, the question 

 arises as to what is the best relation of the length of the horizontal 

 part to the length of the vertical part, when the excitation is to be 

 produced by a given type of generator. It may be known in a general 

 way that the greater the vertical length, the greater the radiation 

 resistance; it may also be known that the greater the horizontal 

 length of the flat-top the greater the capacity of the antenna will be, 

 and the greater will be the amount of current that can be made to flow 

 from certain types of generator. Now these two quantities, radiation 

 resistance and applied current, are both factors in determining the 

 out-put from the antenna. 



For a given generator, with known characteristics, the problem of 

 getting the greatest output of high frequency energy is a problem in 

 the determination of the maximum value of the product of current 

 square and radiation resistance of the antenna. 



But this is not the whole problem, for there comes also Into con- 

 sideration the question as to how much of the radiated energy is 

 radiated by the horizontal flat-top in what may be a useless direction. 



Again, of the energy radiated from the vertical part of the antenna, 

 how much of it contributes to the electric and magnetic forces on the 

 horizon, where the receiving station is situated? 



For the solution of these various problems it is important to know 

 the radiation characteristics of the antenna in the form of certain 

 functional relations. These relations should be known even when 

 inductance is added at the base of the antenna for providing coupling 

 or for increasing the wavelength to adapt it to the generator. These 

 quantities should be known theoretically, since the ordinary measure- 

 ments of these quantities do not permit us to distinguish radiation 



