TRANSOCEANIC TELEPHONE SERVICE 



265 



prevent satisfactory long-wave operation. On the other hand severe 

 fading or the poor transmission accompanying a magnetic disturbance 

 may interrupt short-wave service without affecting the long waves 

 adversely, — in fact magnetic disturbances often improve long-wave 

 transmission in the daytime. The service interruptions on the two 

 types of circuits are thus nearly unrelated to each other and have no 

 definite tendency to occur simultaneously. This is the principal 

 reason why both long-wave circuits and short-wave circuits appear 

 essential to reliable radiotelephone service. 



On routes which are very long or which cross tropical areas which 

 result in static sources facing the directive receiving antennas, long 



+ 10 



+ 5 



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in 



X 



o 



z 



If) -10 

 o 



y -15 



>-20 



I- 



< 



Ml 



a. -25 



-30 



-36 



18,740 -5^ 

 < 



■2. 



2 



18,730 < 



sl£- 



Q 



18,720 H 



18.710 p 



UJ 



z 

 o 



18,700 < 



18,690 



"i 



I- 



< 



5 4 3 2 

 HAYS BEFORE 



I 



STORM 



3 4 5 6 



DAYS AFTER 



18,680 , 



18,670 ^ 

 z 

 o 

 a 



18,660 2 

 O 

 O 



18,6501: 



Fig. 2 — Effect of magnetic disturbances on radio transmission. 



waves cannot as yet be successfully employed and short waves alone are 

 available. However, experience tends to indicate that on North 

 and South routes such as between North and South America, the 

 interruptions associated with magnetic storms are less severe and of 

 shorter duration. 



The cycle of events which accompanied a particularly severe mag- 

 netic storm ^ in July, 1928, is shown graphically in Fig. 2. The light 



■* Data regarding other magnetic disturbances are given in a paper by C. N. Ander- 

 son, entitled "Notes on the Effect of Solar Disturbances on Transatlantic Radio 

 Transmission," /. R. E. Proc, Vol. 17, No. 9, September, 1929. 



