Abstracts of Technical Articles From Bell System Sources 



Notes on the Effect of Solar Disturbances on Transatla?itic Radio 

 Transmission.^ Clifford N. Anderson. In 1923 when the relation 

 between abnormal long-wave radio transmission and solar disturbances 

 was first noted, the outstanding abnormality was the great decrease in 

 night time signal field strength accompanying storms in the earth's 

 magnetic field. There was a slight increase in daylight signal field but 

 this was distinctly secondary to the efi^ect upon night field. Previous 

 to 1927, data on signal fields were limited to one set of measurements 

 a week, and although daylight signal field strengths were higher during 

 periods of increased magnetic activity, it was somewhat difficult to 

 determine the efi"ect of individual storms. The present notes show the 

 efl^ects of individual storms of 60-kc transatlantic radio transmission 

 and also give some indication as to their efi'ect on short-wave radio 

 transmission. 



The Mutual Impedance Between Adjacent Antennas} Carl R. 

 Englund and Arthur B. Crawford. The simple theory for the 

 computation of reflecting or multibranch antenna systems is sketched. 

 If the points at which observations of electrical quantities are to be 

 made are definitely specified, a knowledge of the self and mutual 

 impedances (properly defined) between antennas is sufficient to make 

 the computations determinate. Of the circuit constants, the most use- 

 ful and accessible is the antenna current ratio 



and in the work here reported has been measured in the range 0.33 X 

 to 1 X. Experiment has shown that in this range is that theoretically 

 calculable for a Hertzian doublet. Actually this range is equivalent to 

 X/3 to 00 . The discussion of experimental procedure is purposely 

 thorough. 



An Experimental Method for the Determination of the Ballistic De- 

 magnetization Factor.''^ Donald Foster. A method is described for 

 experimentally determining the ballistic demagnetization factor. By 

 means of a double search coil ot novel design the magnetization and 



1 Proceedings of the Institute of Radio Engineers, September, 1929. 

 - Proceedings of the Institute of Radio Engineers, August, 1929. 

 ^Philosophical Magazine, September, 1929. 



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