Transmitting Antenna in Wireless Telegraphy. 21 



The curves in B and C (figs. 11, 12) are very similar, from 

 which it is to be concluded that the simple earth connection is 

 equivalent to a wire similar to the antenna, or, as already indi- 

 cated in previous experiments, the earth acts as a mirror. 



The curves in D (fig. 14) are not so regular in their form as 

 those in B and C. There is a gradual fall of potential, but 

 the fundamental is not so intense as in the others, and there is 

 a superposition of other oscillations. This agrees with the 

 statement of de Forest* that with this arrangement there is 

 liability to overtones. It is to be observed, too, that here 

 again the disturbance is produced at some distance from the 

 earth end. 



It is to be noted that none of the curves in A is similar to 

 any in C. From this it follows that though as far as the fre- 

 quency of the oscillations in an open circuit is concerned, a 

 capacity may replace an inductance, still the form of the oscil- 

 lations is quite different in the two cases. 



Thus the direct method is in general result similar to the 

 simple system, but it is more regular and more powerful. 

 According to Wienf the radiation is 13 times as intense as that 

 of the simple radiator. 



III. Conclusions. 

 The following conclusions seem to follow from my experi- 

 ments : 



1. In the simple Marconi method and the method of direct 

 excitation, when the antenna is joined to earth, the effect is 

 similar to using a wire the same as the antenna to balance it ; 

 that is, considered from an optical point of view, the earth 

 acts as a plane mirror. 



2. In these conditions the chief oscillation is the funda- 

 mental of the antenna, with wave-length four times its length. 

 The condenser circuit in the method of direct excitation 

 impresses its wave-length on the antenna, but its oscillations 

 are not nearly so intense as those proper to the antenna itself. 

 Thus the manner of oscillation is essentially the same in the 

 two methods, but the latter is more regular and powerful than 

 the former. 



3. In the inductive method of excitation, on the other hand, 

 the prominent feature of the oscillations is that one due to the 

 condenser circuit. With antennae of different lengths there is 

 little change in this oscillation, the curve indicating it being 

 decided and definite ; but only one quarter of its wave-length 

 is shown. This may be due to the great losses from radiation 

 by the wire. The fundamental proper to the antenna is also 



* L. de Forest, N. Y. Electrical World and Engineer, May 17, 1902. 

 fM. Wien, Ann. der Physik, viii, p. 686, 1902. 



