An airborne man-made radio noisa model was developed and programed on a 

 graphics computet at NOSC to aid in the evaluation. Parametric equations 

 developed by Skomal 2 are used to model the heiqht gain of can-made radiv> noiae 

 as a function of distance from the source. Ooefficlentfe for these equations 

 are calculated from data measured over Seattle by Buehler and Lunden. To 

 provide a useful approximation to the geographical dependence of airborne man- 

 made radio noise in the continental United States, two hundred of the nation's 

 largest cities and 62 of the largest counties and military installations are 

 used as sources of radio noise in the model. 



Radio noise maps are produced using this model and are used to evaluate 

 the effect of man-made ladio noise on the operation of K3CS. Those maps show 

 that very little of the continental United States is free of airborne man-made 

 radio noise. Minimum noise levels are found during the night at low altitudes 

 for distances greater than 100 miles from most metropolitan areas. 



2.0 SURFACE MAN-MADE RADIO NOISE 



Perhaps the first Known case of man-made interference to radio signals 

 occurred in 1902 when Dr. A. Hoyt Taylor heard ignition noise from a two- 

 cylinder automobile. Today, man-made radio noise extends to all continents 

 and is detectable at subsynchronous satellite altitudes in the frequency range 

 of 30 Hz to 7 GHz. 



Man-made radio noise is of three types: (1) incidental radiation from 

 electric power lines, ignition systems, electric motors, home electrical ap- 

 pliances; (2) intentional radiation such as wireless announcing systems, cam- 

 pus radio stations, walkie-talkies, door-opener transmitters, and licensed 

 transmitters; and (3) unintentional radiation from cable TV systems, microwave 

 ovens, industrial heaters, medical diathermy equipment, RF-stabilized arc 

 welders, and many others. 4 The lower portion of the spectrum is dominated by 

 industrial, scientific and medical equipment, with power line and automobile 

 ignition noise becoming major contributors around 30 VXz and ignition noise 

 achieving a position of dominance at and above 100 MHz. 



Surface man-made radio noise has an impulsive distribution with frequency 

 and approaches a thermal ization (Gaussian distribution) with increasing alti- 

 tude. This thermalization increases with increasing frequency also. Figure 2 

 shows median daytime values of surface man-made radio noise power in terms of 

 Fa (dB above thermal noise at 288-K) as a function of frequency for business, 

 residential, rural and quiet rural ai^as. 5 Business areas are denned as the 



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