112 AUSTIN: HIGH FREQUENCY RESISTANCE 



given in Table XVI of the paper already cited it is possible to 

 calculate the amount of energy which would have been received at 

 the given distance ( 30 miles) over salt water. The current reduced 

 to a receiving antenna resistance o" 25 ohms would amount to 

 21O10 -6 amperes. The actual current received was 7610 - ' 

 amperes, therefore, the ground absorption amounts to 64 per cent. 



The currents were measured as in the former experiments 2 by 

 means of a rectifying detector with galvanometer in a circuit 

 coupled to the antenna. The galvanometer deflections amounted 

 on an average to 80 millimeters and no certain difference could 

 be detected between the deflections due to the damped and to 

 the undamped oscillations. The uncertainty of the observations 

 amounted to probably 10 per cent. No correction was made for 

 the difference in effective resistance of the receiving antenna for 

 the damped and undamped waves. This might amount to from 

 10 to 20 per cent. 



The conclusion to be drawn is that the absorption of the energy 

 of the waves in passing over the country in question was the same 

 in the case of the undamped and moderately damped oscillations 

 within the limits of the errors of observation. 



RADIO-TELEGRAPHY. — Suitable wire sizes for high frequency 

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

 Laboratory. 



It often becomes necessary in high frequency testing to intro- 

 duce definite amounts of resistance into the circuits. For the 

 sake of convenience in calculation it is usually desirable to have 

 the wires composing the resistances of such size as to make the 

 so-called skin effect negligible since in this way it is possible to 

 measure the resistance by direct current methods and to be sure 

 that the high frequency resistance will be practically the same 

 in value. If the experimenter does not take the trouble to calcu- 

 late the relation between high frequency a>nd direct current resist- 

 ance, he is frequently led to use resistance wires of too small size, 

 thus unnecessarily sacrificing current carrying capacity. 



2 Bulletin Bureau of Standards, 7:295. 1911. 



