NS ORD-1996-033 Zoning Ordinance Text Amendments - Telecommunication Towers

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JULES COHEN & ASSOCIATES, P.C. CONSULTING E VGiNEExS WASHINGTON, D.C. 20036 40 Engineering Statement Page 4 Carrboro, North Carolina Uncontrolled environments are locations where there is exposure of individuals who have no knowledge or control of their exposure. A residential area would be an example of an uncontrolled environment. The MPE for uncontrolled environments for emissions in the 300 to 3000 MHz frequency range may be calculated using the formula S= f 1500 where, as before, f is the frequency in megahertz, and S is power density in milliwatts per square centimeter. While there are some exceptions, in general, the MPEs for uncontrolled environments are one-fifth the MPEs for controlled environments, and the averaging times for uncontrolled environments are five times longer than for controlled environments. As was the case with the protection guide level and the MPE for controlled environments, the most restrictive MPE for uncontrolled environments occurs at 869 MHz. Applying this frequency to the formula yields an WE for uncontrolled environments 0.58 mW/cm=. Measurement Procedure Electromagnetic field sa gth measurements were made using a Narda, model 8716, serial number 06052, electromagnetic monitor calibrated in units of milliwatts per square centimeter. The model 8761, serial number 02003, isotropic probe was used for all electric field measurements. The electromagnetic monitor exhibits of sensitivity threshold of 0.005 mW/cm2. The sensitivity threshold of the instrument corresponds to 0.17 percent of the MPE for controlled environments and 0.86 percent of the MPE for uncontrolled environments. Because of the frequencies is use at the site and the distances from the radiation sources being measured, the electric field component of radiation alone was sufficient to define cgxmire, and a full course of magnetic field measurements was deemed unnecessary. However, a model 8731, serial number 02030, isotropic probe was used for spot magnetic field measurements. The electromagnetic monitor and probes were calibrated as a system in April 1992.