THEORY AND RESULTS 



155 



400 



1,000 



2,000 3,000 4,000 5,000 



HEIGHT ,h , IN m 



6,000 7,000 



Figure 4.47. Distance versus height above duct representing average Washington, 

 D.C., and Fairbanks, Alaska, atmosphere. 



distance, do, that the radio ray travels from the transmitter to the top of 

 the duct is given by 



d(ht - 



hA): 



(4.38) 



i.e., the distance obtained by using the difference of ht and Ha as the value 

 of height on the abscissa in figures 4.47 and 4.48 gives the distance do. 

 The distance, dho, to the standard radio horizon from the transmitter is 



dho = \^2ht 



(4.39) 



if ht, the transmitter height, is in feet and rf^o is in miles. Using this fact 

 and figures 4.47 and 4.48, table 4.10, which shows the ratio of do to dho, 



Table 4.10. Ratio of onset point of fading zones from transmitter to distance of radio 

 horizon from the transmitter, do/dho, for various transmitter heights at Washington, D.C. 



