JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. II, MARCH 4, 1912 No. 5 



RADIO-TELEGRAPHY. — Damped and undamped oscillations. 

 L. W. Austin, U. S. Naval Wireless Telegraphic Laboratory. 



The idea has occurred to me that the ground absorption of 

 damped and undamped oscillations might differ from each other, 

 other Conditions being the same. Therefore the following exper- 

 iment was carried out between the Naval Academy at Annapolis, 

 Md., and the Radiotelegraphic Laboratory at Washington. The 

 antenna at Annapolis is of the harp form, approximately 150 feet 

 high. In this damped oscillations were produced by a Fessenden 

 rotary gap 2 kw. sending set of the type used in our long distance 

 quantitative measurements. 1 The continuous oscillations were 

 produced by a Poulsen arc. In both cases the resonance curve 

 of the antenna was examined by means of a wave meter to make 

 certain that only one definite wave length was emitted The 

 coupling of the Fessenden set was made extremely loose so as to 

 reduce the antenna current to the value obtainable from the arc, 

 the decrement being approximate y 0.15. This antenna current 

 was 3.5 amperes and the wave length with each set was 1060 

 meters. • 



The antenna at the Radiotelegraphic Laboratory is an eight 

 wire harp approximately 180 feet high at top and 60 feet high 

 at bottom. This makes the center of capacity 120 feet above 

 the earth. Taking the height of the center of capacity of the 

 Annapolis antenna as 75 feet from the earth, from the data 



1 Bulletin Bureau of Standards, 7:315. 1911. 



Ill 



