Attachment Rad Haz Report

This document pretains to SES-STA-20171213-01333 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2017121301333_1314485

Radiation Hazard Study 450 MHz Earth Station This study analyzes the non-ionizing radiation levels for a 450 MHz Yagi tracking earth station. This report is developed in accordance with the prediction methods contained in OET Bulletin No. 65, Evaluating Compliance with FCC Guidelines for Human Exposure to Radio Frequency Electromagnetic Fields, Edition 97-01. Bulletin No. 65 specifies that there are two separate tiers of exposure limits that are depending on the area of exposure and/or the status of the individuals who are subject to the exposure -- the General Population/Uncontrolled Environment and the Controlled Environment, where the general population cannot access. The maximum level of non-ionizing radiation to which individuals may be exposed is limited to a power density level of 1.5 milliwatts per square centimeter (1.5 mW/cm2) averaged over any 6 minute period in a controlled environment, and the maximum level of non-ionizing radiation to which the general public is exposed is limited to a power density level of 0.3 milliwatt per square centimeter (0.3 mW/cm2) averaged over any 30 minute period in a uncontrolled environment. In the normal range of transmit powers for satellite antennas, the power densities at or around the antenna surface are expected to exceed safe levels. The purpose of this study is to determine the power flux density levels for the earth station under study as compared with the MPE limits. This comparison is done in each of the following regions: 1. Far-field region 2. Near-field region 3. Transition region 4. The region between the antenna edge and the ground Input Parameters The following input parameters were used in the calculations: Parameters: Value Unit Symbol Antenna Diameter 3.15 m D Antenna Transmit Gain 16.5 dBi G Transmit Frequency 450 MHz f Power Input to the Antenna 60.26 W P Calculated Parameters: The following values were calculated using the above input parameters and the corresponding formulas:

Parameter Value Unit Symbol Formula Antenna Surface Area 1.663 m2 A Gλ2/(4π)/λ Antenna Efficiency 0.95 η Gλ2/( π2D2) Gain Factor 44.7 g 10 G/10 Wavelength 0.67 m λ 300/f Behavior of EM Fields as a Function of Distance The behavior of the characteristics of EM fields varies depending on the distance from the radiating antenna. These characteristics are analyzed in three primary regions: the near-field region, the far-field region and the transition region. Of interest also is the region between the antenna and ground. For yagi antennas with circular cross sections, such as the antenna under study, the near- field, far-field and transition region distances are calculated as follows: Parameter Value Unit Formula Near-Field Distance 3.72 m Rnf = D2/(4λ) Distance to Far-Field 8.93 m Rff = 0.60D2/(λ) Distance of Transition Region 3.72 m Rt = Rnf The distance in the transition region is between the near and far fields. Thus, R nf < Rt < Rff. However, the power density in the transition region will not exceed the power density in the near-field. Therefore, for purposes of the present analysis, the distance of the transition region can equate the distance to the near-field. Power Flux Density Calculations The power flux density is considered to be at a maximum through the entire length of the near-field. This region is contained within a cylindrical volume with a diameter, D, equal to the diameter of the antenna. In the transition region and the far-field, the power density decreases inversely with the square of the distance. The following equations are used to calculate power density in these regions. Parameter Value Unit Symbol Formula Power Density in the Near-Field 13.77 mW/cm2 Snf 16.0 η P/(πD2) Power Density in the Far-Field 0.27 mW/cm2 Sff GP/(4π Rff2) Power Density in the Transition Region 13.77 mW/cm2 St Snf Rnf /(Rt) The power density between the antenna and ground, is calculated as follows: Parameter Value Unit Symbol Formula Power Density b/w Reflector and Ground 3.62 mW/cm2 Sg P/A The below table summarizes the calculated power flux density values for each region. In a controlled environment, the only regions that exceed FCC limitations are shown below. These regions are only accessible by trained technicians who, as a matter of procedure, turn off transmit power before performing any work in these areas.

Power Density Value Unit Controlled Environment Far Field Calculation 0.27 mW/cm2 Satisfies FCC MPE Near Field Calculation 13.77 mW/cm2 Exceeds Limits Transition Region 13.77 mW/cm2 Exceeds Limits Region b/w Antenna & Ground 3.62 mW/cm2 Exceeds Limits In conclusion, the results show that the antenna, in a controlled environment, may exist in the regions noted above and applicant will take the proper mitigation procedures to ensure it meets the guidelines specified in 47 C.F.R. § 1.1310. The antenna will be installed at DS12 Access Road, Prudhoe Bay, Alaska 99734. Access to the antenna requires a 45 ft man-lift, which should safely restrict any public access. It should be noted that all spaces at least 8.5 m away from the antenna satisfy the FCC MPE limits for the general population. The earth station will be marked with the standard radiation hazard warnings, as well as the area in the vicinity of the earth station to inform the general population, who might be working or otherwise present in or near the path of the main beam. The applicant will ensure that the main beam of the antenna will be pointed at least one diameter away from any building, or other obstacles in those areas that exceed the MPE limits. Since one diameter removed from the center of the main beam the levels are down at least 20 dB, or by a factor of 100, public safety will be ensured. Finally, the earth station’s operational personnel will not have access to areas that exceed the MPE limits while the earth station is in operation. The transmitter will be turned off during periods of maintenance so that the MPE standard of 1.5 mW/cm2 will be complied with for those regions in close proximity to the antenna, which could be occupied by operating personnel.


Document Created: 2017-12-13 23:27:41
Document Modified: 2017-12-13 23:27:41
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