Attachment Rad Haz

This document pretains to SES-STA-20151119-00861 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2015111900861_1115774

EXHIBIT A Radiation Hazard Study 2.4 meter Ka-Band INTRODUCTION The FCC adopted new guidelines and procedures in 1996 for evaluating environmental effects of radio frequency (RF) emissions. In order to provide assistance in determining whether proposed or existing transmitting facilities comply with the new guidelines, the FCC Office of Engineering and Technology revised OET Bulletin 65. The revised version updates limits for Maximum Permissible Exposure (MPE) in terms of electric and magnetic field strength and power density for transmitters operating at frequencies between 300 kHz and 100 GHz. This bulletin was adopted by the FCC in their General Docket No. 97-303 on August 25, 1997. In order to comply with the requirements of the Report and Order, calculations to determine the power flux densities in the far field, near field, and reflector regions of the earth station antenna have been made and are contained in this study. The FCC guidelines incorporate two separate tiers of exposure limits that are dependent on the situation in which the exposure takes place and the status of the individuals who are subject to exposure. The earth station transmitting equipment and antenna are located within a controlled area and not accessible to the general public. Entry is restricted to employees who have been made fully aware of the potential for human exposure and can exercise control over their exposure. Therefore occupational / controlled exposure maximum power density limits are used in this study. The FCC Office of Engineering and Technology suggests a method for calculating the maximum values of the power densities emanating from an aperture antenna in OET bulletin 65. This method is used to determine the power densities associated with the satellite antenna. The Mount Jackson Ka-Band satellite earth station will be equipped with an amplifier having a maximum output of 10 watts. The transmitter will feed a 2.4 meter antenna via a transmission link with no loss. The following calculations will be based on a maximum output power at the antenna flange of 10 watts: Antenna Surface: The maximum power density directly in front of the antenna may be expressed as: 4P S surface = A where: S surface = maximum power density at the antenna surface P = power fed to the antenna A = physical area of the aperture antenna 1

EXHIBIT A Radiation Hazard Study 2.4 meter Ka-Band Using the parameters for the Mount Jackson antenna: S surface = 4 (10 Watts) / π (2.4 meters / 2) 2 S surface = 40 Watts / 1.4 m 2 S surface = 8.8 Watts / m 2 S surface = 0.9 mW / cm 2 Near- Field Region: In the near field of the main beam the power density can reach a maximum before it begins to decrease with distance. The extent of the near field can be described by the following equation: D2 Rnf = 4λ where: Rnf = extent of near field D = maximum diameter λ = wavelength Using the parameters for this antenna: λ = 0.01 meters @ 30000 MHz Rnf = (2.4 meters) 2 / 4(0.01 meters) Rnf = 5.8 / .04 meters Rnf = 144 meters The magnitude of the on axis power density varies according to location in the near field. However, the maximum value of the near field, on axis, power density can be expressed by the following equation: 16ηP S nf = πD 2 where: S nf = maximum near field power density η = aperture efficiency P = power fed to the antenna D = antenna diameter Using the parameters for this antenna: 2

EXHIBIT A Radiation Hazard Study 2.4 meter Ka-Band η = .65 P = 10 Watts S nf = 16 (.65) (10 Watts) / π (2.4 meters) 2 S nf = 104 Watts / 18.1 meter 2 S nf = 5.7 Watts / meter 2 S nf = 0.6 mW / cm 2 Far Field Region: For purposes of evaluating RF exposure, the distance to the beginning of the far field region can be approximated by the following equation: 0.6 D 2 R ff = λ where: R ff = distance to the beginning of far field D = diameter of antenna λ = wavelength Using the parameters for this antenna: R ff = 0.6 (2.4 meters) 2 / .01 meter R ff = 346 meters The power density in the far field region of the antenna pattern decreases inversely as the square of the distance. The power density in the far field region of the radiation pattern can be estimated by the equation: S ff = PG / 4πR 2 where: S ff = power density (on axis) P = power fed to antenna G = power gain of the antenna in the direction of interest R = distance to the point of interest Using the parameters for this antenna: 3

EXHIBIT A Radiation Hazard Study 2.4 meter Ka-Band S ff = 10 Watts (10(55.1 dBi/10)) / 4 (π) (346) 2 S ff = 3235937 / 1500919 S ff = 2.2 Watts / meter 2 S ff = 0.2 mW / cm 2 Region between Feed and Reflector: The RF energy radiated from the feed system is highest at the feed horn aperture. The power density at any point in this region is expressed by the equation: S feed = P/A where: A = Cross section area of feed horn in meter² P = Radiated transmitted power in watts At the sub-reflector surface the power density is: S feed = P/A = 10 / π (0.1/ 2)² = 1455 Watts/meter² S feed = 146 mW / cm² 4

EXHIBIT A Radiation Hazard Study 2.4 meter Ka-Band CONCLUSION The results of the above calculations are summarized in the following table. Region Power Density Remarks Antenna Surface 0.9 mW/cm² Safe Level Main Reflector Sub-reflector Region 146 mW/cm² Hazardous Near Field < 144 meters 0.6 mW/cm² Safe Level Far Field > 346 meters 0.2 mW/cm² Safe Level Results of this hazard study indicate that the 5 mW/cm² MPE limit for Occupational/Controlled Exposure in the 1500 – 100,000 MHz range is not exceeded in areas directly in front of the antenna in the far field. The region where this limit may be exceeded will be the region between the reflector and the feed horn. This area is not readily accessible to personnel and whenever personnel are required to work on the radiating or reflecting parts of the antenna structure, the transmitter will be turned off. Signs to this effect will be posted at the transmitter site. Based on this study of predicted radio frequency levels, it is concluded that operation of this satellite earth station meets OET Bulletin 65 maximum permissible exposure limits and that no harmful effects will occur to station personnel or anyone within proximity of the station. Therefore, in accordance with 47 CFR § 1.1307 (b) of the Commission's Rules, preparation and submission of an Environmental Assessment (EA) is not required. 5


Document Created: 2015-11-19 14:00:27
Document Modified: 2015-11-19 14:00:27
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