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BELL SYSTEM TECHNICAL JOURNAL 



the Rochester data into other months. An examination of the noise 

 data observed on the loop antenna at Houiton along with the loop 

 antenna received noise obtained at Rochester, New York, point by 

 point during the period of these tests indicated a fairly constant differ- 

 ence between the noise at these two places. On 37 days during Sep- 

 tember, October and November 1930, observations of printer operation 

 at Rochester and noise observations at Houiton were made within the 

 same hour. Using the errors observed in the Rochester radio copy on 

 these 37 days and the corresponding 37 values of loop noise at Houiton 

 the cumulative curves shown in Fig. 6 were obtained. From these two 

 curves the same relation as shown in Fig. 5 can again be obtained.* 



5 10 15 20 25 30 



SIGNAL-TO-NOISE RATIO (db) 



AT V. F. FILTER OUTPUT 



Fig. 5 — -Relation between printer errors and signal-to-noise ratio as 

 determined from the Rocky Point-to- Rochester tests. 



Since such a good correlation had been observed between the 

 Rochester and Houiton data over the period covered by the tests, it ap- 

 peared that the Rochester data might be extrapolated to cover a greater 

 time by use of the Houiton noise readings. The same general method 

 as outlined in Appendix A has, therefore, been applied to the Houiton 

 loop noise data for the entire year of 1930 and the results are shown by 

 Fig. 7. From this figure the great seasonal and diurnal variation in 

 grade of transmission is at once apparent. It must be emphasized that 



* For detail of method see Appendix A. 



