An Assessment of Potential Health Effects from Exposure to PAVE PAWS Low-Level Phased-Array Radiofrequency Energy (2005) / Chapter Skim
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4 Exposure Levels
4 Exposure Levels
Pages 37-52
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From page 37... ...
. Recent measurements of PAVE PAWS power density recorded by census tract obtained as part of the current initiative to re-exarnine the potential health effects of exposure to low-level phased-array RF energy are included.
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From page 38... ...
Transmitted Power Each face of the PAVE PAWS radar consists of a regular grid of 2677 antennas of which 885 are unactlve, leaving 1792 active that are directly commected to
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From page 39... ...
, although on average the maximum duty cycle does not exceed 25%. Although the waveform modulation scheme is complicated by the multi-task operation of PAVE PAWS, the modulation of transmitted power experienced at a fixed location on the ground has been estimated based on the assumption that the radar is functioning in an enhanced search mode (where the main beam targets 120 different azimuthal locations at 3° above the horizon every 2.5 seconds)
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From page 40... ...
; (4) the 2000 report by Mitre Corporation on "RF Power Density Exposure at Ground Level for the PAVE PAWS Radar at Cape Cod—Questions and Answers" (MITRE 2000)
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From page 41... ...
was acceptable given the calibration procedures employed and differences in line of sight to the various measurement locations, Interestingly, in this same report (NRC 1979b) , the panel made its own estimahon of nominal and worst-case estimates of average power density on the main axis of a secondary sidelobe taking into account charactenshcs of the radar, and reported numbers of 8.2 ,uW/cm2 (nominal)
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From page 42... ...
More specifically, the committee concluded that average power density outside the Air Force base was not likely to exceed I mW/cm2, the average power density at the exclusion fence surrounding PAVE PAWS was approximately 5 ,uW/cm2, while the average measured intensity at locations where the public would most likely be exposed was 0.06 mW/cm2 (Route 6, 1.0 km from the radar)
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From page 43... ...
had a maximum power density of 3716 ,IlW/cm2, a minimum of 127 ,IlW/cm2, and a mean of 1190 ,UW/cm2 The same equipment and procedures were used to measure power densities within surrounding Cape Cod communities at a height of 6 feet above the ground for all except two locations: (a) the Sandwich Fire Tower, which was 86 feet above the ground and in direct line of sight of the radar, and (b)
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From page 44... ...
At these locations, the power density was calculated by considering the distance from the radar, the main beam elevation angle, and the time-averaging factors associated with the pulse-transmission scheme. For the peak-power calculation, a peak radiated power (543 kW)
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From page 45... ...
The Broadcast Signal Lab Report During the first quarter of 2004, the Broadcast Signal Lab, Medfield, MA (B SL 2004a, b) , executed a survey of RF emissions from the PAVE PAWS radar facility located at the Massachusetts Military Reservation on Cape Cod.
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From page 46... ...
. One interesting exception was the Scargo Hill site whose average power density was 0.0038 ,uW/cm2 at some 18.5 miles from the radar (65 foot elevation)
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From page 47... ...
performed power density measurements on Cape Cod at 26 sites (23 firehouses, 2 commuter parking lots, and l lighthouse) spanning 311 days beginning in May of 2003.
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From page 48... ...
Both data sets also indicate that some of the highest peak power-densities occur at locations having the greater distances from the radar, especially when the straight-line distance from the radar to the measurement site cuts across the coastal waters of Cape Cod Bay. Other findings in the COPPS data are consistent with expectations (and the BSL results)
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From page 49... ...
The final 10 sites selected attempted to represent high, low, and middle-level exposure conditions to these sources as a means of providing a representative sampling of the ambient RF exposures on Cape Cod. The propagation model was used to define the power levels and associated locations that would be expected to bracket exposure conditions given the relevant sources of radiation identified.
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From page 50... ...
of 0.72 ,IlW/cm2, 0.27 ,uW/cm2, 0.32 ,uW/cm2, and 0.26 ,uW/cm2 for the yeats 2001, 2002, 2003, and 2004, respectively. The survey of GSM base stations by the Australian Radiahon Protection and Nuclear Safety Agency measured 13 sites that yielded an average power density iFrom the Website http://www.mcw.edu/gcrc/cop/cell-phone-health-FAtVtoc.html and http:// www, ofcom, org.
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From page 51... ...
Nonetheless, the average power densities have been consistently below 0.1 mW/cm2 and generally in the 0.001-0.01 mW/cm2 range at locations where the public would be expected to be exposed. The simulation studies that have been reported estimate higher values overall, but for the most part still suggest that the exposure of the public is less than I ,uW/cm2 in terms of average power density.
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From page 52... ...
2004a. Survey of RF Energy Field Emissions from the PAVE PAWS Radar Located at Cape Cod Air Force Station, Massachusetts: Final Test Plan, prepared in consultation with international Epidemiology institute, Rockville, MD, by Broadcast Signal Lab, Medfield MA.
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