102 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 5 



zontal as well as a vertical axis. The receiving set consists of a pri- 

 mary inductance and parallel capacity connected between the two 

 collectors as shown in figure 2, and a secondary, generally of the mag- 

 netic back-coupled oscillating vacuum tube type, provided with a 

 two-stage audio frequency amplifier, though in some experiments a 

 radio-audio amplifier with heterodyne was used. The whole set in- 

 cluding the batteries was mounted on top of the pole. 



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Fig. 1. Diagram of pivoted straight wire antenna system, mounted on top of 55 foot pole. 



The method of experiment is as follows. The antenna is first set 

 vertical with the horizontal axis approximately in the plane of the 

 wave front. This gives maximum signal. It is then rotated about 

 the horizontal axis and as the antenna approaches the horizontal 

 position the signal fades as on an ordinary radio compass. At some 

 angle it dies out, and then as the rotation is continued comes in again. 

 At the mean of the two positions of just audible signal, the antenna is 

 perpendicular to the wave front if there are no causes of distortion. 

 The antenna is next rotated through 180 degrees and two more angles 

 of disappearing signal are observed. The mean of the four observa- 

 tions should give the determination with considerable accuracy. 



In the final experiments the mast with its pivoted antenna and 

 instruments was erected on the Anacostia Flats not far from the 

 Washington Navy Yard. The absence of wire lines and houses within 



