Attachment Exhibit B

This document pretains to SES-MOD-20101216-01583 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2010121601583_857060

Exhibit Number B - Radiation Hazard Analysis ANALYSIS OF NON-IONIZING RADIATION FOR A 3.8 METER EARTH STATION Completed: 12/02/2010 This report analyzes the non-ionizing radiation levels for a 3.8 meter earth station. It is the purpose of this report t determine the power flux densities of the earth station at the antenna surface, near field, far field, and the transition region. Results are summarized in Table 1 on page 4. The Office Engineering & Technology Bulletin, No. 65, August 1997, specifies the following Maximum Permissib Exposure (MPE) levels for non-ionizing radiation : 1. Occupational/Controlled Exposure is 5mW/cm² (five milliwatts per centimeter squared) over an average time of 6 (six) minutes. 2. General Population/Uncontrolled Exposure is 1mW/cm² (one milliwatt per centimeter squared) over an average time of 30 (thirty) minutes. The following parameters were used to calculate the various power flux densities for this earth station: Location: Dillingham Earth Station, Alaska Latitude: 59.04 °N Longitude: 158.46 °W Operating Frequency: 6175 MHz Wavelength (λ) 0.0485 meters Antenna Diameter (D): 3.8 meters Antenna Area (A): 11.34 meters² Transmit Antenna Gain: 46.1 dBi Transmit Antenna Gain (G): 40738.0 numeric Maximum 1° Off Axis Gain 29.0 dBi Maximum 1° Off Axis Gain (G1°) 794.3 numeric Antenna Efficiency (η): 0.674 numeric Feed Power (P): 200 Watts Exhibit B Page 1 of 4

Exhibit Number B - Radiation Hazard Analysis 1. Antenna Surface The power density in the main reflector region can be estimated by: Power Density at Reflector Surface, Ssurface = 4P/A = 70.54 W/m² = 7.05 mW/cm² Ssurface= maximum power density at antenna surface P= power fed to the antenna A= physical area of the antenna 2. Near Field Calculations In the near field region, of the main beam, the power density can reach a maximum before it begins to decrease with distance. The magnitude of the on axis (main beam) power density varies according to location in the near-field. The distance to the end of the near field can be determined by the following equation: Extent of Near Field, Rnf = D²/4(λ) = 74.36 meters Rnf= extent of near field D= maximum dimension of antenna (diameter if circular) λ= wavelength The maximum near-field, on-axis, power density is determined by: On Axis Near Field Power Density, Snf = 16ηP/D²π = 47.53 W/m² = 4.75 mW/cm² The maximum near-field, 1° off-axis, power density is determined by: Power Density at 1° Off Axis Snf 1°= (Snf/G)*G1° = 0.0927 mW/cm² Snf= maximum near-field power density Snf 1°= maximum near-field power density (1° off axis) η= aperture efficiency P= power fed to antenna D= maximum dimension of antenna (diameter if circular) Exhibit B Page 2 of 4

Exhibit Number B - Radiation Hazard Analysis 3. Far Field Calculations The power density in the far-field region decreases inversely with the square of the distance. The distance to the beginning of the far field region can be found by the following equation: Distance to the Far Field Region, Rff = 0.6D²/λ = 178 meters Rff = distance to beginning of far field D= maximum dimension of antenna (diameter if circular) λ= wavelength The maximum main beam power density in the far field can be calculated as follows: On-Axis Power Density in the Far Field, Sff = (P)(G)/4π(Rff)2 = 20.36 W/m² = 2.04 mW/cm² The maximum far-field, 1° off-axis, power density is determined by: Power Density at 1° Off Axis Sff 1°= (Sff/G)*G1° = 0.0397 mW/cm² Sff= power density (on axis) Sff 1°= power density (1° off axis) P= power fed to antenna G= power gain of antenna in the direction of interest relative to an isotropic radiator Rff = distance to beginning of far field 4. Transition Region Calculations The transition region is located between the near and far field regions. The power density decreases inversely with distance in the transition region, while the power density decreases inversely with the square of the distance in the far-field region. The maximum power density in the transition region will not exceed that calculated for the near-field region. The power density in the near field region, as shown above will not excee St= 4.75 mW/cm². St 1° = 0.0927 mW/cm². Exhibit B Page 3 of 4

Exhibit Number B - Radiation Hazard Analysis Table 1 Summary of Expected Radiation Levels Calculated Maximum Maximum Permissible Exposure (MPE) Region Radiation Level (mW/cm²) Occupational General Population 1. Antenna Surface Ssurface= 7.05 Potential Hazard Potential Hazard 2. Near Field Snf= 4.75 Satisfies MPE Potential Hazard 3. Far Field Sff= 2.04 Satisfies MPE Potential Hazard 4. Transition Region St= 4.75 Satisfies MPE Potential Hazard 5. Near Field 1° Off Axis Snf 1°= 0.0927 Satisfies MPE Satisfies MPE 6. Far Field 1° Off Axis Sff 1°= 0.04 Satisfies MPE Satisfies MPE 7. Transition Region 1° Off Axis St 1° = 0.0927 Satisfies MPE Satisfies MPE 7. Conclusions 7. Conclusions Based on the above analysis it is concluded that the only risk of exposure to levels higher than the Maximum Permissible Exposure limit a at the surface of the antenna, in the near-field of the main beam, in the far-field of the main beam, and in the transition region of the main beam. At 1° off axis the radiation levels are well within limits. A 5° minimum elevation angle and a fence surrounding the facility will protect the public from exposure to high radiation levels. The transmitter will be turned off during antenna maintenance and the 5° minimum elevation angle will ensure safety of the earth station personnel. JP Metangbou RF Engineer GCI Communication Corp. Exhibit B Page 4 of 4


Document Created: 2010-12-02 14:25:02
Document Modified: 2010-12-02 14:25:02
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