SELECTIVE FADING OF MICROWAVES 



09 



nature of the fading. Some data derived from the continuous i-oconhngs 

 of signal levels are presented in an appendix. 



The angle-of-arri\'al observations were made at a frequency of 2-1,000 

 megacycles. The freiiuency-sweei) experiment and the reconhngs of signal 

 levels were made in the 8700 to 4200 mc^gacycle frequency hand as were 

 the short pulse observations described in the companion paper. 



GENERAL DISCUSSION OF PROPAGATION PHENOMENA 



The map of Fig. 1 shows the location of the experimental transmission 

 paths. The path between Crawford Hill and Southard Hill is 17 miles 

 long and clears the intervening terrain by 65 feet, approximately one 

 Fresnel zone at a frequency of 4000 megacycles. The other path, between 

 Crawford Hill and a 100-foot tower on the Murray Hill Laboratory 

 property, is 22.8 miles long and has clearance of 280 feet. Fig. 2 shows 

 the profiles of these two paths. 



The general characteristics of over-land microwave transmission are 

 well kno^\ii and need be reviewed only briefly. During the daytime 

 hours, when the lower atmosphere is thoroughly mixed by rising con- 

 vection currents and winds, the signals are normally stable and are near 



MORRISTOWN 



MURRAY HILL 

 LAB 



ASBURY 

 PARK 



Fig. 1 — Map showing location of the experimental transmission path. 



