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BELL SYSTEM TECHNICAL JOURNAL 



work was accordingly discontinued. For this flight, the signal strength 

 at 80 miles was ten decibels below that observed on November 1, and 

 twenty-one decibels below that recorded September 27. The con- 

 clusion is inescapable that transmission to regions beyond the optical 

 range is determined by conditions which are not constant and which 

 in fact can produce great signal strength changes. 



U 40 



Z 30 



10 20 30 40 50 60 70 80 90 100 110 120 130 



MILES FROM TRANSMITTER 



Fig. 8 — Flights from transmitter. Wave-length — 4.6 meters; Altitude — 1000 feet. 



The 1.58 meter observations at 1000 feet check the 4.6 meter results 

 fairly well. They follow theory within the optical range. Figure 10, 

 corresponding to Fig. 8 for the 4.6 meter observations, shows some 

 indication of diflfraction, and Fig. 11 checks the rapidly falling signal 

 intensity of the bottom curve of Fig. 8. At no time was the half way 

 distance to Montauk reached. There are several reasons for this. 

 The power level available at 1.58 meters was nearly 10 db below that 



