ULTRA-SIIORT-WA VE TRANS ML'^.SIUN PHENOMENA 



213 





120 



40 eO 120 160 200 240 260 320 360 400 440 480 



FEET 



F"ig. 12 — Profile map of Beer's Hill. 



With a sufficiently plane slope a maximum-to-minimum field com- 

 parison should yield a dependable value of the amplitude of the reflec- 

 tion coefficient since the other two reflection components (transmitter 

 hill and intermediate earth surface) are not rapidly varied by such a 

 limited change in receiving antenna height. Unfortunately the an- 

 tenna could not be elevated above 55 feet (16.8 meters), and with the 

 moderate hill slope existing, this was insufficient to reach the first 

 above-ground field minimum. 



The intermediate earth surface reflection component, at this near- 

 grazing incidence, acts to reduce the total received field, and it is im- 

 portant to obtain an idea of how great this effect is likely to be. It is 

 necessary to rely on the accuracy of the topographical maps as issued 



< -3 



Fig. 13- 



20 30 40 I 



ANTENNA HEIGHT IN FEET 



-Local reflection at Beer's Hill. \'ertical 

 polarization x = 4.45 meters. 



