The Office of Safety and Security purchased a NARDA Safety Test Solution GmbH, Selective Radiation Meter 3000 (SRM-3000) equipped with a three axis (triaxial) antenna.  The SRM-3000 is an instrument for measuring electromagnetic fields in the frequency range from 75 Megahertz (MHz) to 3 Gigahertz (GHZ).  The triaxial antenna allows the SRM-3000 to perform simple and fast isotropic measurements by automatically detecting the three spatial components of the field being measured.  The main measurement task is the determination of electromagnetic field strength (power density).

The SRM-3000 with the tri-axial probe, measures the electromagnetic field selectively, by service and frequency, regardless of where the radiation is radiating.  Used in the safety evaluation mode, the SRM-3000 provides a spectrum analysis of a variety of frequency bands within the 75 MHz to 3 GHz range (i.e. all FM frequency from 88.5 MHz to 107.9 MHz, the Personal Communication System (PCS) receive band of 1850 MHz to 1910 MHz, and the PCS transmit band of 1930 MHz to 1990 MHz). 

The SRM-3000 comes precalibrated from NARDA Safety Test Solution GmbH and has a recommended calibration interval of 24 months.  The SRM-3000 can be operated in temperatures ranging from -10^o C to 50^o C and relative humidity of 5 to 95 percent.  The SRM-3000 can be operated in brief periods of rain, though it was never operated in the rain during any FCPS survey.

The SRM-3000 has a variety of setup options.  For the purpose of the FCPS surveys the SRM-3000 was set up to measure survey locations utilizing the triaxial (X,Y,Z axis measurement or isotopic measurement) using the safety evaluation spectrum analysis setting.

The frequency range was set up between 75 MHz and 3 GHz.  The measurement range (this determines the sensitivity of the system) was set at the lowest possible sensitivity or 1.6 microwatts per centimeter squared (uW/cm²). 

The display measurement was setup in the milliwatts per centimeter squared (mW/cm²) setting.  The SRM-3000 displayed test results in milliwatts (1,000^th of a watt or 1X10^-3 watts), microwatts (1,000,000^th  of a watt or 1 x 10^-6 watts), nanowatts (1,000,000,000^th of a watt or 1 x 10^-9 watts), and picowatts (1,000,000,000,000^th of a watt or 1 x 10^-12 watts).

The trace type, which determines how the values recorded are evaluated and displayed, was set on the MAX AVERAGE mode.  The MAX AVERAGE mode evaluates and displays the average of all maximum values for a specific survey point. The MAX AVERAGE mode in essence is the worst-case scenario for each specific survey point.

The Office of Safety and Security field staff collaborated with the Fairfax County, Department of Information Technology, Emergency Communications Branch, in the design of and methodology of the survey.  The Fairfax County, Department of Information Technology, Emergency Communications Branch, has at least two (2) NARDA-trained staff members who followed the Office of Safety and Security field staff on a site survey to verify survey methodology and site measurements with Emergency Communications Branch's NARDA RF meter equipment.

Survey methodology was designed taking into consideration Section 3: Measuring RF Fields of the FCC’s OET Bulletin 65, “Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields.”

Each individual survey location was evaluated and recorded using the SRM-3000 with the setup described in the above instrumentation section.

Monopoles situated on the school sites have different telecommunication carrier’s antennas installed on them.  All the monopole carriers, on school sites, transmit and receive in a specific range of frequencies known as the American Personal Communication System (PCS) cell phone band. The American PCS cell phone band is divided into three distinct segments: 1) A 60 MHz wide cell phone receive band (1850 to 1910 MHz), 2)  A 20 MHz wide "unlicensed" band (the frequency that consumer home cordless phones uses), which also serves as a "guard band" (1910 to 1930 MHz), and 3) A 60 MHz wide cell phone base station transmit band (1930 to 1990 MHz).

For purposes of this survey, the PCS cell phone receive band (1850 to 1910 MHz) and the PCS cell phone base station transmit band (1930 to 1990 MHz) were measured at each sampling location to determine the total PCS RF emission emanating from FCPS monopole sites as well as total PCS RF emissions from those sites without monopoles.

Additionally, as a comparison to other RF energy at all sites, RF emissions from the local radio FM transmit bands (88 MHz to 107.9 MHz) and local television channel transmit bands (174.0 MHz to 806.0 MHz), consisting of local television Channels 7 through 70, were measured and recorded.

OSS field staff collected MAX AVERAGE data for five (5) minutes at each specific location.  The SRM-3000 typically collected and evaluated RF energy every 2 seconds.  Each individual survey location data point represents approximately 150 MAX AVERAGE values.  On average OSS field staff collected 30 sample points at each school site with cell phone base station antennas and 15 sample points at schools without cell phone base station antennas.

Surveys were performed at school sites during normal school days typically during the hours of 0900 to 1500, with most surveys being performed during 1100 to 1430.

At school sites with cell phone base station antennas, the base station antenna was located onsite, the orientation of the antenna array (typically mounted triangularly, three different arrays, around the base station antenna).  The base station antenna and orientation were marked on an aerial photograph of the school. 

Field staff started at the base of the cell phone base station antenna and worked out from that location to physical geographical sites at the school.  The physical sites were picked so that they could be located on aerial photographs and the distance from the cell phone base station antenna to the survey point could be determined also the physical site represented a survey point that could be revisited and resurveyed. 

Though survey locations were located at geographical physical sites, those survey locations were chosen so that they would be as close to perpendicular (in front of one of the three antenna arrays) to the antenna array at each school site with a cell phone base station antennae.  Some typical physical survey locations included: school exterior entrances, playgrounds, and physical education fields.

Non-monopole school survey sites were chosen to represent a variety of school site environments; sparse urban development (Clifton E.S., Fairview E.S., and Robinson S.S.); intermediate urban development (Kilmer M.S. and Freedom Hill E.S.); and denser urban development (Marshall H.S., Jackson M.S., and Stenwood E.S).  Some typical physical survey locations at school sites without cell phone base station antennas included: school exterior entrances, playgrounds, and physical education fields

Survey locations inside schools with monopoles were chosen in classrooms that were closest to the monopole and that faced monopoles.  Interior survey measurements were taken in first floor, second floor, and in one case (Centreville High School) a third floor classroom.  Survey measurements were taken in the middle of classrooms. 

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