474 abstracts: radiotelegraphy 



mile, mean rainfall, and depth in inches on drainage areas. The com- 

 plete base data are published in order that independent studies may 

 be made in greater detail. For purposes of comparison, there are 

 records and information covering all floods since the country was first 

 settled. H. D. McG. 



RADIOTELEGRAPHY.— .4t>^/aM^ antenna constants. J. M. Cork. 

 Bur. Standards Sci. Paper 341. Pp. 14, figs. 12. 1919. 



This paper contains data observed by the writer while an officer in 

 the Signal Corps, U. S. Army, and is published by permission of the 

 Chief Signal Officer. The purpose of this work was to devise a method 

 for measuring airplane antenna constants (i. e., capacity, inductance, 

 natural wave length) under conditions of actual flight; and to use this 

 method to obtain data on various forms of fixed and trailing wires. 



The principle of the method involves a continuous wave oscillator 

 feeding directly into the antenna and substituting for the antenna a 

 variable calibrated condenser and adjusting for the same wave length 

 as with the antenna in the oscillating circuit. The result obtained is the 

 eff^ective capacity of the antenna. Having found this, a variable cali- 

 brated non-inductive resistance is varied until the D. C. component of 

 the plate current reads the same as for the real antenna. This gives the 

 effective antenna resistance. Knowing the eff"ective values of capacity 

 at various wave lengths, the true capacity, inductance and natural 

 wave length are readily found. 



By this method results were obtained with various forms of fixed 

 wires, and one, two and four trailing wires of various lengths, are sum- 

 marized. 



A method for finding the directional transmitting effect of various 

 antennas is also described. In order to compare the amounts of energy 

 received, a detector tube with a three-stage audio amplifier is used. A 

 transformer is placed in the plate circuit of the last amplifier tube, the 

 secondary of which is connected to the heater coil of a thermocouple 

 connected to a D. C. micro ammeter. This when calibrated is free 

 from many of the uncertainties of the ordinary audibility meter. A 

 typical directional curve of the trailing wire antenna is included in the 

 paper. J. M. C. 



