476 



lUil.L SYSTEM TECHNICAL JOURNAL 

 NoisK Stkkncth 



Next to field strength the most important factor in determining 

 the communication possibilities of a radio channel is that of the 

 interfering noise. The extent to which noise is subject to (liuni.il 

 and seasonal xariations is therefore of first order of importance. 



Transmission from Ffacky PpintLI.(WQL) to New Southqate Eno 



GMT IE PU 12 AM 12 12 PM 12 AM e 12 PM 12 AM B. K. PM 12 



F«b. S2-25 S«pU 23-24 Jan. 27-28 Oct. ft- 



25-26 JO-Oct. I F»b. 1- 



12 12 PM 12 AM IZ 



1924 



1 livlurc 

 riul afte 



lagnctic storm had !>cgiin. 



I'iR. 1.? — Correlation I>ctwccn radio transmission and variations in earth's 

 niadndir field 



Diiiniul Vdrialion. An ex.imi)le of llie diurnal characteristic of 

 the noise for both ends of the transatlantic path is given in Fig. 14. 

 One curve is shown for each of the several frecjuencics measured. 

 The outstanding points to be observed are: 



1. The rise of the static noise about the time of sunset at the receiv- 

 ing station, the high \alue.s. prevailing at night, and the rather sharp 

 decrease accompan_\ing sunrise. The curve for 15 kc. shows the ex- 

 istence of high \alues also in the afternoon. During the summer 

 months higii afternoon values are usual for all fretiuencies in this 



