RADIO PROPAGATION OVER SPHERICAL EARTH 



4Sl 



100 » 500 1000 5000 10,000 



y = d/\/XK2 (dg,XlN KILOMETERS) 



Fig. 2 — Ratio of the field received over perfectly conducting spherical earth 

 with refraction by the lower atmosphere to that over perfectly conducting plane 

 earth. 



formula for long-distance long-wave communication, 



120x7// 



E 



\d 



g-0,0015d/Vx 



(9) 



to the above diffraction formulas. He showed that this formula, (9), 



could be obtained by considering the earth surrounded by a conducting 



shell some 100 km. above the earth's surface. He also showed that 



the factor X~^'- instead of X~^/'^ occurs only when the effect of the upper 



atmosphere becomes important. Equations (1), (2) and (4) apply 



only for distances in which the effect of the upper atmosphere may be 



neglected. 



Experiment 



In Figs. 3 and 4 the theoretical curve of Fig. 2 has been superimposed 

 upon experimental data^ obtained for 0.8 and 4 mc. transmission 

 respectively. Theoretical curves are shown for radius ratios of 1, 

 4/3 and 1.45. The latter gives the best fit with the experimental data. 

 The curve for a ratio of 4/3 estimated from available meteorological 

 data is in fair agreement with the data, but since this is only an 

 estimate of the average value of the ratio it is possible that 1.45 is a 

 better value for the conditions of the experiment. It is doubtful, 



* All experimental points that represented transmission affected by the ionosphere 

 have been excluded. 



