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BELL SYSTEM TECHNICAL JOURNAL 



sometimes be detected up to a distance of 50 miles (81 kilometers). 

 This interference is, however, very much less than on short-wave 

 reception. 



One continuous transmission test from Holmdel and Beer's Hill to 

 Lebanon was made April 24 and 25, 1931, extending through the 

 night and over both the sunset and sunrise periods. The Beer's Hill 

 transmission was horizontally polarized, the Holmdel transmission 

 vertically polarized. The wave-lengths were 4.17 and 4.5 meters, re- 

 spectively. Quarter-hourly observations were taken during the night, 

 and observations were made every five minutes through the sunrise and 

 sunset periods. No signal variations or abnormalities were observed, 

 and harmonics of short-wave stations, though looked for, could not be 



Fig. 21 — Map of line covered by airplane flights. 



heard. We have since observed these harmonics, for high power 

 stations, but not from any great distance. 



The Beer's Hill transmitter power during all our tests never ex- 

 ceeded 6 w^atts, and gave an ample signal intensity at Lebanon, in 

 spite of the 198 degree phase difference of the middle distance reflection 

 component. Telephone transmission was uniformly good. 



Appendix I 

 Calculation of Airplane Reception Curves 

 The resultant field strength at a point in the line of flight (Fig. 22) is 



(1) 



Er = ^{\+ Ke'^e+fr~.ixur,-ro\) 



D 



