﻿Radiation from Bent Antenna?. 595 



chosen, viz., 138 feet, the field in the direction in which the 

 free end points is then about 60 per cent, of that in the opposite 

 direction (see fig. 4, Plate XVII. ). The polar diagrams more- 

 over confirm Mr. Marconi's observation and also my mathe- 

 matical theory that the minimum radiation is not in the 

 direction 90° from the maximum but more nearly 105°, to 

 110°. It will be seen that the effect of making the hori- 

 zontal part of the antenna longer is not so much to increase 

 the fore and aft inequality as to squeeze in the sides of the 

 polar diagram and make it narrower. 



The wave-lengths emitted in each case were measured with 

 a special form of cymometer consisting of a condenser of 

 known capacity and a variable inductance of calculable 

 magnitude. This cymometer circuit was placed near to the 

 horizontal portion of the transmitting antenna and tuned to 

 it until the current in the cymometer circuit was found to be 

 a maximum, as determined by a thermoelectric detector. The 

 frequency in the antenna thus being known from the constants 

 of the cymometer circuit, the radiated wave-length could be 

 calculated. On account of the capacity plate at the end of 

 the antenna, the emitted wave had a length rather greater 

 than 5 times the total length of the antenna, the exception 

 being the -I : 16 case in which the wave-length found by 

 several measurements was 92 feet. 



It is clear then that when using electric waves of about 

 100 feet in length and receiving at a distance of 138 feet, or 

 not much greater than one and one- third of a wave-length, 

 the inequality in radiation in different azimuths is well marked, 

 and is greatest for a certain ratio of horizontal to vertical 

 portions of the antenna. This fore and aft inequality moreover, 

 as well as the form of the polar curve, varies with the distance 

 of the receiving antenna as shown by the following experiment. 

 A bent transmitting antenna 10 feet lono- was used of which 

 3 feet of the length was vertical and 7 feet horizontal. The 

 receiver was placed successively at 138 feet and 78 feet 

 distance and the polar curves taken. The values of the 

 current in the receiving antenna in different azimuths were 

 as shown in Table II. (p. 596). It will be seen that at the 

 shorter distance the inequality in fore and aft radiation is less 

 evident. These values are plotted in the polar carves in 

 figs. 7 and 8 (Plate. XVIL). 



In comparing these results with the theory given we must 

 notice that the theory presupposes that the current in the 

 sending antenna or circuit is everywhere the same. The 

 mathematical investigation of the problem becomes immenselv 

 difficult unless we make this assumption. 



