Figure 9. Daytime 45 MHz airborne man-made radio noise 

 map of the continental United States for an altitude of 

 5 thousand feet. Shaded areas represent noise power 3 dB 

 or less above galactic noise. 



in figure 10, daytime 45 MHz contours for a 10 thousand foo^altitud e are 

 shown. Smaller shaded areas indicate increasing noise ^ la f^ Ranees from 

 business areas characteristic of the height gain xllust ^«- f^ 

 as contours are still too small to .b. ' ««£^ ^ rs ! *r - 30 thoufand 

 are clearly shown in figure 11. JW*** « «£ ^ ^^ ^ 



2J ^SS.^JTS °the th coun^ r/tt disappearance of shaded areas 

 indicating low noise. 



The full effect of height gain is shown in figure 12. Daytime ^45 MHz 

 contours for an altitude of 70 thousand feet are shown. Notice that the JO dB 

 contours have expanded to cover a major portion of the eastern «"^ed State^ 

 Comparison of figures 13 and 14 with the preceding two figures shows ^the 

 dSnal variation^ airborne radio noise. Nighttime 45 »."»»f»» 

 and 70 thousand foot altitudes are ehoven on these maps. Note the re ^™" 

 of shided area, in the western United States indicating low noise. «9urea « 

 and 16 show the effect of frequency on airborne man-made radio noise. *"°™ 

 be seen, these daytime radio noise wps calculated for an altitude of 30 thou 

 sand feet show decreasing radio noise with increasing frequency. 



14 



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