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• <br /> BASE STATION EXPOSURES AT CELLULAR FREQUENCIES <br /> Standard General-Public Occupational Typical Typical Typical expo- <br /> Limit(averaged Limit(averaged ambient ground-level sure 30 inches <br /> over 30 minutes) over six minutes) level maximum from antenna <br /> exposure proper <br /> 1982 ANSI 2900 pW/cm2 Same 0.0005% 0.034% 103% <br /> 1992 ANSI 580 pW/cm2 2900 pW/cm2 0.0025% GP 1.7% GP 517% GP <br /> 0.0005% 0 0.034% 0 103% 0 <br /> 1986 NCRP 580 pW/cm2 2900 pW/cm2 0.0025% GP 1.7% GP 517% GP <br /> 0.0005% 0 0.035% 0 103% 0 <br /> 1986 NCRP with 580 pW/cm2 580 pW/cm2 0.0025% 1.7% 517% <br /> modulation <br /> derating <br /> 1987 IRPA 435 pW/cm2 2175 pW/cm2 0.0034% GP 0.2% GP 690% GP <br /> 0.0007% 0 0.046% 0 138% 0 <br /> DISTANCES TO ACCEPTABLE EXPOSURES FROM BASE STATION ANTENNAS <br /> The following table shows distances,as a function of ERP,to the power flux densities permitted by stan- <br /> dards discussed at the Federal Focus Symposium. The underlying calculations assume no reflection or <br /> absorption, 15 active channels,and omnidirectional antennas.Actual base stations tend to emit less signal <br /> power downward than outward,so the table probably overstates real exposures at the base of a tower. <br /> Because most base-station antennas are 150 feet or so in the air,minimum distances to both the general- <br /> public and occupational limits are more than satisfied.Fewer channels(less exposure)or more channels <br /> (more exposure)may be active at a given base station than the 15 channels assumed. <br /> • <br /> Standard General-Public Distance to Occupational Distance to <br /> Limit General-Public Limit Occupational <br /> Limit Limit <br /> 1982 ANSI 2900 pW/cm2 15.01t(500 W) Same As General Same As General <br /> 10.5 ft.(250 W) <br /> 6.7 ft(100W) <br /> 4.7 ft(50 W) <br /> 3.0 ft (20 W) <br /> 1992 ANSI 580 pW/cm2 33.0 ft(500 W) 2900 pW/cm2 15.0 ft(500 W) <br /> 23.5 ft.(250 W) 10.5 ft(Z50 W) <br /> 14.9 ft(100W) 6.7 ft.(100W) <br /> 10.5 ft(50 W) 4.7 ft(50 W) <br /> 6.7 ft(20W) 3.0 ft (20W) <br /> 1986 NCRP 580 pW/cm2 33.0 ft(500 W) 2900 pW/cm2 15.0 ft.(500 W) <br /> 23.5 ft(250 W) 10.5 ft(250 W) <br /> 14.9 ft(100W) 6.7 ft(100W) <br /> 10.5 ft(50 W) 4.7 ft(50 W) <br /> 6.7 ft(20 W) 3.0 ft.(20 W) <br /> 1986 NCRP with N/A N/A 580 pW/cm2 33.0 ft.(500 WI <br /> Modulation 23.5 ft(250 W) <br /> Derating 14.9 ft(100W) <br /> 10.5 ft(50 W) <br /> 6.7 ft(20 W) <br /> 1987 IRPA 435 pW/cm2 38.4 ft(500 W) 2175 pW/cm2 17.2 ft.(500 W) <br /> 27.2 ft.(250 W) 12.2 ft(250 WI <br /> 17.2 ft.(100W) 7.7 ft(100W) <br /> 12.2 ft(50 W) 5.4 ft(50 W) <br /> 7.7 ft.(20 W) 3.4 ft(20 140 <br />