Attachment RadHaz

This document pretains to SES-MOD-20101026-01341 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2010102601341_847422

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study When applying for a license to construct and operate, modify, or renew an earth station, it is understood that the applicant must certify whether grant of the application will have significant environmental impact as defined in the Federal Communications Commission's (FCC) rules, 47 C.F.R. § 1.1307. In this report Spacenet analyzes the maximum radiofrequency (RF) levels emitted from the satellite communications antenna described below. The reference document for this study is OET Bulletin No.65, Edition 97-01, Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, August 1997. 1. Antenna Near-Field Power Density Calculation The extent of the near-field is defined by the following equation1: Rnear = (Dantenna)² / (4λ) where: Rnear = extent of the near-field (in meters) Dantenna = diameter of the antenna main reflector (in meters) λ = wavelength of the RF transmit frequency (in meters) The maximum on-axis power density within near-field is defined by the following equation2: Snear = {(16η Pfeed) / [π(Dantenna)²]} / 10 where: Snear = maximum on-axis power density within the near-field (in milliwatts per square centimeter) η = antenna aperture efficiency Pfeed = maximum power into antenna feed flange (in watts) Dantenna = diameter of the antenna main reflector (in meters) 1 See OET 65 page 27 formula (12). 2 See OET 65 page 28 formula (13). The right side of the equation is divided by 10 so that the power spectral density units on the left side will be mW/cm2. Page 1 of 6

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study 2. Antenna Far-Field Power Density Calculation The distance to the beginning of the far-field region is defined by the following equation3: Rfar = [0.6(Dantenna)²] /λ where: Rfar = distance to beginning of far-field (in meters) Dantenna = diameter of the antenna main reflector (in meters) λ = wavelength of the transmit frequency in (meters) The maximum on-axis power density within the far-field is defined by the following equation4: Sfar = [(Pfeed Gantenna) / 4π(Rfar)²] / 10 where: Sfar = maximum on-axis power density in the far-field (in milliwatts per square centimeter) Pfeed = maximum power into antenna feed flange (in watts) Gantenna = antenna main beam gain at AF transmit frequency (in numeric value) Rfar = distance to beginning of far-field (in meters) The on-axis power densities calculated from the above formulas represent the maximum exposure levels that the system can produce. Off-axis power densities will be considerably less. 3. Antenna Transition Region Power Density Calculation The on-axis power spectral density for the transition region is defined by the following formula5: Str = Snear Rnear / R where: Str = maximum on-axis power density in the transition region (in milliwatts per square centimeter) Snear = maximum on-axis power density in the near-field (in milliwatts per square centimeter) Rnear = is the distance that defines the end of the near field region. R = is the distance within in the transition region between the near field and far field regions. 3 See OET 65 page 29 formula (16). 4 See OET 65 Section 2, page 19, formula (3) and page 29, formula (18). The right side of the equation is divided by 10 so that the power spectral density units on the left side will be mW/cm2. 5 See OET 65 page 34, formula (17). Page 2 of 6

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study Since the distance within the transition region “R” will always be greater than the distance to the end of the near field region “Rnear” then Str ≤ Snear. 4. Antenna Feed-Flange Power Density Calculation The maximum power density at the antenna feed-flange is defined by the following equation6: Sfeed = 1000{[4(Pfeed)] / {[π(Dfeed)²] / 4}} where: Sfeed = maximum power density at the antenna feed-flange (in milliwatts per square centimeter) Pfeed = maximum power into antenna feed flange (in watts) Dfeed = diameter of the antenna feed-flange (in centimeters ) 5. Antenna Main Reflector Power Density Calculation The maximum power density in the main reflector region of the antenna is defined by the following equation7: Santenna = {[4(Pfeed)] / {[π{(Dantenna)²] / 4}} / 10 where: Santenna = maximum power density in the antenna main reflector region (in milliwatts per square centimeter) Pfeed = maximum power into antenna feed flange (in watts) Dantenna = diameter of the antenna main reflector (in meters) 6. Power Density Calculation between the Antenna Main Reflector and the Ground The maximum power density between the antenna main reflector and the ground is defined by the following equation: Sground = {Pfeed / {[π{(Dantenna)²] / 4}} / 10 where: Sground = maximum power density between the antenna main reflector and the ground (in milliwatts per square centimeter) Pfeed = maximum power into antenna feed flange (in watts) 6 The formula is multiplied by 1,000 on the right side of the equation to change the units from watts on the right side of the equation to milliwatts on the left side. 7 See OET 65 equation (11) which is “S = 4 P / A”, where “A” is the area of the reflector and for a circular reflector A = π (Dantenna )2 / 4. The formula is divided by 10 on the right side to change the units from meters and watts on the right side of the formula to cm and mW on the left side. Page 3 of 6

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study Dantenna = diameter of the antenna main reflector (in meters) 7. Calculation of Radiation Levels and FCC Standards Spacenet understands that a licensee must ensure that people are not exposed to harmful levels of radiation. Spacenet plans to utilize the 0.75 meter ASC Signal fixed and temporary-fixed antennas with 1, 2 or 4-watt transmitters. The transmitters will be operated at full output power. The preceding formulas were used to calculate the power densities shown on the following page. The Commission’s maximum permissible exposure (MPE) limits at the transmit frequency band for the earth stations included in this application are provided in the table set forth below. Maximum Permissible Exposure (MPE) Limits at 14,000-14,500 MHz Power Averaging Density Time Exposure Criteria (mW/cm2) (minutes) Reference OET 65 page 67 general population/uncontrolled 1 6 Appendix A exposure Table 1 (A) OET 65 page 67 occupational/controlled exposure 5 30 Appendix A Table 1 (B) Page 4 of 6

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study Radiation Hazard Calculations – 0.75 meter ASC Signal Fixed & Temporary Fixed Antenna IDs 0.75M & TF 75E 0.75M & TF 75E 0.75M & TF 75E Antenna main reflector diameter 0.75 m 0.75 m 0.75 m Feed flange diameter 6.35 cm 6.35 cm 6.35 cm RF transmit frequency 14.250 GHz 14.250 GHz 14.250 GHz Transmitter power output 1.0 W ( 0 dBW ) 2.0 W ( 3 dBW ) 4.0 W ( 6 dBW ) Transmitter to antenna feed flange loss 0.3 dB 0.3 dB 0.3 dB Power into antenna feed flange 0.93 W ( -0.3 dBW ) 1.87 W ( 2.7 dBW ) 3.73 W ( 5.7 dBW ) Main-beam gain of antenna 38.8 dBi 38.8 dBi 38.8 dBi Antenna aperture efficiency 0.70 0.70 0.70 Antenna main reflector surface area 0.4418 m² 0.4418 m² 0.4418 m² Feed flange surface area 31.67 cm² 31.67 cm² 31.67 cm² Wavelength at RF transmit frequency 0.021 m 0.021 m 0.021 m Distance to beginning of far-field region 16.0 m 16.0 m 16.0 m Distance to extent of near-field region 6.68 m 6.68 m 6.68 m Max. on-axis power density in far-field 0.22mW/cm2 0.44 mW/cm2 0.88 mW/cm2 Satisfies MPE Limits Satisfies MPE Limits Satisfies MPE Limits Max. on-axis power density in near-field 0.59 mW/cm2 1.18 mW/cm2 2.37 mW/cm2 Satisfies MPE Limits (see Note 2) (see Note 2) Max. on-axis power density in transition region 0.59 mW/cm2 1.18 mW/cm2 2.37 mW/cm2 Satisfies MPE Limits (see Note 2) (see Note 2) Max. power density at feed-flange (see note 1) 117.5 mW/cm2 235.8 mW/cm2 471.5 mW/cm2 Potential Hazard Potential Hazard Potential Hazard Max. power density at main reflector 0.84 mW/cm2 1.69 mW/cm2 3.38 mW/cm2 Satisfies All MPE Limits (see Note 2) (see Note 2) Max. power density between main reflector and 0.21 mW/cm2 0.42 mW/cm2 0.84 mW/cm2 ground Satisfies All MPE Limits Satisfies All MPE Limits Satisfies All MPE Limits Note 1: Feed flange power density exceeds both uncontrolled MPE limit of 1 mW/cm2 and controlled MPE limit of 5 mW/cm2 Note 2: Satisfies controlled MPE limit of 5 mW/cm2, but is a potential hazard for uncontrolled MPE limit of 1 mW/cm2 Page 5 of 6

Spacenet Services License Sub, Inc. Application for a Modification of Earth Station Authorization E000035 Exhibit C - Radiation Hazard Study 8. Conclusion The calculations provided in this exhibit indicate that MPE limits are exceeded in certain areas of the 0.75 meter earth stations. The 0.75 meter fixed and temporary-fixed antenna exceeds the MPE limits for occupational/controlled and general population/uncontrolled exposure at the feed horn and in the area between the feed horn and reflector for the 1, 2 and 4-watt transmitters. Additionally, for installations where a 2 or 4-watt transmitter is used, the MPE for general population/uncontrolled exposure is exceeded at the antenna reflector, in the near field region and the transition region. All 0.75 meter fixed antennas will be installed such that the area where the MPE is exceeded will not be readily accessible to humans. All 0.75 meter temporary-fixed antennas will be installed on the roof of a vehicle or other location such that for all installations the area where the MPE is exceeded will not be readily accessible to humans. Additionally, all transmissions will be terminated whenever the technical staff is required for maintenance or other activities to occupy the regions where potentially hazardous power density levels can exist. The 0.75 meter fixed and temporary-fixed earth stations have an automatic shut-off mechanism that will terminate transmissions if the receive signal is lost, which will occur if there is blockage of the area between the feed horn and reflector. Page 6 of 6


Document Created: 2008-03-05 09:15:23
Document Modified: 2008-03-05 09:15:23
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