JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. 11 March 4, 1921 No. o 



RADIOTELEGRAPHY. — The wave front angle in radiotelegraphy^ 

 h. W. Austin, U. S. Naval Radio Research Laboratory. 



One of the outstanding problems in radiotelegraphic transmission 

 is the determination of the angle between the advancing wave front 

 and the earth. A number of physicists- have treated the subject 

 theoretically and a resume of their conclusions may be found in Zen- 

 neck's Wireless Telegraphy (translation 1915), pp. 246-2.5.3. The 

 subject is of great importance in the theory of transmission and has a 

 very practical interest in the reception of signals on ground antennas. 



Several experimenters have attempted to measure the wave front 

 angle by means of receiving loops, the method being to rotate the 

 loop around a vertical axis to the point of minimum signal and then to 

 rotate again around a horizontal axis in the plane of the wave front 

 until silence is obtained. A little consideration will show that this 

 method is not applicable to the problem, since after the minimum is 

 obtained by rotation about the vertical axis, none of the magnetic 

 lines of the wave can thread the loop no matter what its angle in ref- 

 erence to the wave front, any residual effect in this position being due 

 to the action of the loop as an antenna. 



The most obvious method for measuring the angle, and the one 

 which seems most free from objection, makes use of a pivoted straight 

 wire antenna system well elevated above the ground with a receiver 

 inserted in the middle. The general arrangement is shown in figure 1 , 

 and the method of shielding the circuits in figure 2. The antenna 

 consists of two collector wires, each 30 feet long, supported on a 

 piv^oted wooden spreader (Fig. 1) 60 feet long, mounted at the top 

 of a 55 foot wooden pole so as to be capable of rotation about a hori- 



1 Received December 20, 1920. 



/-J. Zenneck, Ann. Phys. 23: 846. 1907. K. UllER, Jahrb. 2: S. 190S. A. 

 SOMMERFELD, Ann. Phys. 28: 665. 1909. P. Eppstein, Jahrb. 4: 176. 1910. 



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