LONG-WAVE RADIO TELEPHONE TRANSMISSION 693 



siderable efifect on long-wave radio transmission, the effect would 

 apparently be an increase in field strength in daytime, opposite to the 

 result observed by Pickard on signals from Nauen. For the period 

 covered by the curves in Fig. 4, the increased daylight field strength in 

 August is not explained by correlation with the curves of magnetic 

 activity. 



Nature and Sources of Data 



The long-wave radio telephone data used in this study are measure- 

 ments of field strength at the receiving stations, and each individual 

 observation is a simple physical measurement. The data taken before 

 1927, although relatively meager, were observations made under 

 controlled conditions, a single-frequency signal being employed. Since 

 1927 the data, while much more abundant, had to be taken under 

 operating conditions with speech transmission. However, since such 

 measurements can be made on a commercial circuit only when in the 

 judgment of the operating forces it is desirable and feasible to establish 

 that circuit, it is inevitable that the overall picture will be distorted by 

 the requirements of practical circuit operation. This could readily 

 obscure such minor effects as correlation with meteoric showers, and 

 would be likely to introduce some discrepancies between day and night 

 behavior. 



Sources of the data used in Figs. 2 and 3 are as follows : 



Ultra-violet and sunspot data from Terrestrial Magnetism, 39, 234, September 1934. 

 Solar limb-prominences data from Astronomische Mitteilungen, 130, 217, 1933, and 



from 131, 23, 1934. 

 Data for the Washington measurements — for 1923, figure by correspondence with the 



Bureau of Standards; for 1924 to 1930, reference 24; for 1931-1932, reference 



25; observations were discontinued in 1933. 

 Magnetic character data, " C" measure, from volumes 29 to 39, inclusive, of Terrestrial 



Magnetism. 

 Magnetic activity, U\ measure, from references 10, 26, and 28. 



ACKN OWLEDGMENTS 



The authors wish to thank the personnel of the American Telephone 

 and Telegraph Company and British General Post Office who made the 

 observations and supplied the radio transmission data used in this 

 paper. Acknowledgments are also due the Carnegie Institution of 

 Washington, the United States Bureau of Standards, and Dr. Charles 

 P. Olivier for other information used by the authors in correlating and 

 interpreting the results. 



Bibliography 



1. H. Plendl, "Concerning the Influence of the Eleven-Year Solar Activity Period 

 Upon the Propagation of Waves in Wireless Telegraphy," Proc. I. R. E., 20, 

 520, March 1932, and references. 



