Attachment RF Hazard Study

This document pretains to SES-LIC-20160323-00269 for License on a Satellite Earth Station filing.

IBFS_SESLIC2016032300269_1130811

Radiofrequency Radiation Hazard Study prepared for WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station On behalf of WGBH Educational Foundation, this statement provides the results of a Radiofrequency Radiation Hazard Study regarding a proposed new 4.8 meter earth station uplink facility to be established in Boston, MA. The earth station will operate in the “Ku” band with a transmitter power output of 100 watts and a General Dynamics 4.6 meter diameter dish antenna. In keeping with §1.1307(b) of the FCC’s rules, the proposed operation has been evaluated for human exposure to radiofrequency energy using the procedures outlined in FCC OET Bulletin No. 65 (“OET 65”). According to the applicant, the 4.6 meter dish antenna is rooftop mounted on an office building utilized by television station WGBH-TV (Boston, MA). The rooftop is 22 meters above ground level and access to the rooftop is controlled and limited to authorized and trained personnel. The following data have been used with the OET 65 equations for predicting RF fields for a parabolic aperture antenna: Proposed Earth Station Parameters Center Frequency of Operation 14.250 GHz Wavelength at Center Frequency 0.02105 meters Transmitter Power Output (Average) 100 Watts Antenna Diameter 4.8 meters Antenna Gain 55.0 dBi Antenna Gain Ratio 316,228 Antenna Aperture Efficiency 0.314 At the range of the uplink transmit frequencies (14.0 – 14.5 GHz), according to FCC rule section §1.1310 the maximum permissible exposure (“MPE”) limit for human exposure to RF electromagnetic field is 1.0 mW/cm2 for general population / uncontrolled exposure and 5.0 mW/cm2 for occupational / controlled exposure.

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station (page 2 of 3) The following RF power density results were calculated using OET 65 procedures (see Appendix 1): Maximum RF Power Density Calculated Power Density Region (mW/cm2) Conclusion Far Field On-axis 0.58 Satisfies Both MPE (begins at 656.6 m) Transition Region On-Axis Exceeds Uncontrolled MPE 1.36 (273.6 to 656.6 m) Satisfies Controlled MPE Near Field On-axis Exceeds Uncontrolled MPE 1.36 (ends at 273.6 m) Satisfies Controlled MPE Off-axis Near Field 0.0136 Satisfies Both MPE (at one antenna diameter) Off-axis Far Field 0.000017 Satisfies Both MPE (656.6 m at 7° off axis) On-axis (in the main beam of the antenna), the maximum near field power density is calculated to be 1.36 mW/cm2, which also extends into the transition region. This satisfies the occupational / controlled MPE limit but exceeds the general population / uncontrolled limit. Such on-axis locations are well elevated above ground and are not accessible by the general public. The antenna’s arc of potential operation does not encroach on any nearby tall buildings. Off-axis, the maximum power density is 0.014 cm2 which does not exceed the general population / uncontrolled MPE. Since the areas of interest for general population / uncontrolled exposure relates to locations at ground level or other accessible areas in the vicinity of the rooftop fixed earth station dish, the distance between the antenna and the general population is substantially greater than one antenna diameter from the main beam. The maximum calculated signal density at one antenna diameter off-axis in the near field is equal to or less than 0.014 mW/cm2 or 1.4% of the general population / uncontrolled MPE. When the antenna’s actual off-axis distance and elevation angle to the general population in the vicinity of the antenna location are considered, the calculated signal density at publicly accessible locations will be even lower. Based on this analysis, it is concluded that the general public will not be exposed to RF levels in excess of the general population / uncontrolled MPE.

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station (page 3 of 3) When accessing the rooftop, most personnel can easily limit their access to a distance of at least one antenna diameter away from the antenna and the main beam while the dish is in operation, as these areas comply with the general population / uncontrolled MPE limit. Authorized and trained personnel individuals that are covered by the occupational / controlled MPE limit may approach the antenna to a minimum distance of 0.32 meters from any part of the antenna, provided that they do not enter the area in front of the antenna’s main reflector. To assure the compliance with safety limits, all emissions shall cease whenever personnel must access areas within 0.32 meters of the antenna as those areas may exceed the occupational / controlled MPE limit. Chesapeake RF Consultants, LLC January 12, 2016 207 Old Dominion Road Yorktown, VA 23692 703-650-9600

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station APPENDIX 1 RF POWER DENSITY CALCULATIONS NEAR FIELD REGION Within the near-field region of a parabolic reflector antenna, the maximum value of RF power density occurs on-axis at a distance of Rnf (Extent of Near Field) as expressed by: Rnf = D2 / 4λ where: Rnf = distance to beginning of near-field D = antenna diameter λ = wavelength For this analysis, it is assumed that the maximum value of the RF power density exists throughout the entire length of the near-field region. For the proposed Ku-band satellite uplink earth station, the near field extends to a distance of: Rnf = 273.6 meters The maximum value of on-axis RF power density that is possible within the near field region of the proposed Ku-band satellite earth station antenna can be expressed by the following equation: Snf = (16 η P) / ( π D2) where: Snf = Maximum near-field power density η = Aperture efficiency P = Power fed to the antenna For the Ku-band satellite earth station antenna, the maximum RF power density in the near field is calculated to not to exceed: Snf = 1.36 mW/cm2 OET 65 states that the “power density at that point (one antenna diameter removed from the center of the main beam) would be at least a factor of 100 (20 dB) less than the value

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station APPENDIX 1 RF POWER DENSITY CALCULATIONS (page 2 of 4) calculated for the equivalent distance in the main beam.” Accordingly, estimates of the off-axis RF power density in the near field region were made with this conservative presumption. For the proposed Ku-band satellite earth station, the General Population/Uncontrolled Exposure at a distance of at least 4.8 meters from the maim beam, the near field maximum off-axis power density is no greater than: Snf(oa) = 0.0136 mW/cm2 TRANSITION REGION The RF power density in the transition region between the near field and the far field of a parabolic reflector antenna decreases inversely with distance from the antenna. The far field region (farthest extent of the transition region) can be approximated by the following equation: Rff = 0.6 D2 / λ where: Rff = distance to beginning of far-field The beginning of the far field is calculated to be: Rff = 656.6 meters The maximum value of on-axis RF power density level in the transition region can be determined by the following relationship: St = Snf Rnf / R where: St = Maximum power density for transition region R = distance to point of interest Assuming the point of interest is R=Rnf = 273.6 meters where the maximum (upper bound) of the power density exists, the RF power density in the transition region is: Snf = 1.36 mW/cm2 (Maximum predicted density in the transition region)

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station APPENDIX 1 RF POWER DENSITY CALCULATIONS (page 3 of 4) The General Uncontrolled/Exposure area will be at least one antenna diameter distant from the Ku-band satellite earth station antenna and, according to OET 65, the off-axis power density can be conservatively assumed to be at least 20 dB below the maximum level from the center line axis of the antenna. Within the transition region, the maximum off-axis RF power density is less than the maximum value of: St (oa) = 0.0136 mW/cm2 FAR FIELD REGION For the proposed Ku-band satellite earth station, the maximum possible value of on-axis RF power density in the far field region can be determined as follows: Sff = (P G) / (4 π R2) where: Sff = Power density (on axis) G = Power gain relative to an isotropic radiator For the Ku-band satellite earth station, the maximum RF power density at the end of the transition between the near field and the far field (R = 656.6 m) was calculated to not exceed: Sff = 0.584 mW/cm2 In compliance with the antenna meeting or exceeding performance specifications under §25.209(a)(2) of the FCC rules, the off-axis gain of the proposed antenna is 8 dBi (a power gain of 6.31) or less in any direction 7 degrees or more from the main lobe. The off-axis RF power density for the Ku-band satellite earth station can be conservatively calculated using the far field power, gain, and distance relationship as: Sff(oa) = (P G) / (4 π R2)

Radiofrequency Radiation Hazard Study WGBH Educational Foundation Fixed Satellite Service - Fixed Earth Station APPENDIX 1 RF POWER DENSITY CALCULATIONS (page 4 of 4) Assuming a distance of 656.6 meters from the antenna (the far-field location nearest the antenna), the off-axis RF power density is calculated to be: Sff(oa) = 0.0000117 mW/cm2 OFF-AXIS POWER DENSITY The minimum distance required for authorized and trained personnel to approach the antenna from locations not in the main beam can be determined as follows: S = (P G) / (4 π R2) Solve for R (distance), where P = 100 Watts G = unity S = 5 mW/cm2 (Occupational Limit) R = 0.32 meters Authorized and trained personnel individuals that are covered by the occupational / controlled MPE limit may approach the antenna to a minimum distance of 0.32 meters from any part of the antenna, provided that they do not enter the area in front of the antenna’s main reflector.


Document Created: 2016-01-12 14:19:42
Document Modified: 2016-01-12 14:19:42
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