Attachment RF Exposure Study

This document pretains to SES-LIC-20111220-01467 for License on a Satellite Earth Station filing.

IBFS_SESLIC2011122001467_929538

Engineering Statement RADIOFREQUENCY EXPOSURE CALCULATIONS prepared for KMBC Hearst Television Inc. KMBC Hearst Television Inc. (“Hearst”) herein proposes a new fixed “Ku Band” satellite uplink to be located at 6455 Winchester Avenue, Kansas City, Missouri. The following study was conducted to evaluate the proposed facility with respect to the potential for human exposure to radiofrequency (“RF”) electromagnetic field. Specifically, the study determined whether exposure to RF electromagnetic field would exceed FCC maximum permissible exposure limits to the general public and, when certain procedures are followed, to occupational workers in the vicinity of the Earth station antenna. Human Exposure to Radiofrequency Electromagnetic Field The Hearst operation was evaluated using the procedures outlined in FCC OET Bulletin No. 65 (“OET 65"). OET 65 describes a means of determining whether a proposed facility exceeds the RF exposure guidelines specified in §1.1310 of the Rules. Under present Commission policy, a facility may be presumed to comply with the limits in §1.1310 if it satisfies the exposure criteria set forth in OET 65. Based upon that methodology, and as demonstrated in the following, the transmitting system under study will comply with the cited adopted guidelines at publicly accessible locations when procedures described herein are followed. Public Exposure The antenna is located at ground level in a fenced area accessible only to occupational personnel through a locked door having appropriate warning signs. The only areas accessible to the public are located at a significant distance and well off-axis from the antenna main lobe. The mechanical design of the antenna mount is normally configured such that the antenna main beam is aimed at a geostationary satellite located well above the horizon. Although not normally to be used with other satellites, the proposed facility will be capable of operation throughout the entire satellite arc. Prevention of public exposure to predicted RF Cavell, Mertz & Associates, Inc.

Engineering Statement (page 2 of 4) electromagnetic field in excess of the general population/uncontrolled limit1 depends on adherence to the following operational guidelines by Hearst technicians. As shown below, RF attributable to the Hearst Earth station antenna at locations outside of the “main beam”2 will not exceed the FCC general population and uncontrolled RF exposure limits. To assure that no publicly accessible area is within the “main beam” of the uplink antenna, the Earth station transmitter will only be permitted to operate when the antenna elevation exceeds 4.5 meters and five degrees away from the horizon, nearby buildings, and places accessible to the public. Based on data provided by the applicant, the following parameters were used in the study: Antenna Manufacturer ViaSat, Inc. Antenna Model 8345 Center Transmit Frequency 14.250 MHz Wavelength at Center Frequency 0.02104 meters Max Average Antenna Input Power 56.2 Watts Antenna Diameter 4.5 meters Antenna Gain 54.3 dBi Antenna Gain Ratio 269,153 Antenna Aperture Efficiency 0.596 1 The general population/uncontrolled maximum permissible exposure (“MPE”) limit of 1 mW/cm² for 14,250 MHz is specified in §1.1310 of the Rules. 2 For purposes of this study, the “main beam” extends 4.5 meters beyond an imaginary cylinder extending skyward from the “face” of the Earth station antenna plus any location within five degrees of the center-line of the antenna. Cavell, Mertz & Associates, Inc.

Engineering Statement (page 3 of 4) The area in the immediate vicinity of the antenna is known as the “near field region.” In this region (241 meters in the case at hand), the antenna directional characteristics of have not fully formed. Therefore, antenna manufacturer “off-axis” discrimination specifications cannot be utilized for the purpose of determining potential RF exposure. OET 65 provides a methodology (Equation 13) for calculating a “worst case” exposure figure within this region. Additionally, OET 65 methodology suggests that the “worst case” power density would be reduced by 20 dB at locations at least one antenna diameter (4.5 meters) off-axis from the “main beam” of the antenna. In this instance, the predicted off-axis, near field is 0.014 mW/cm², or 0.3 percent of the general population/uncontrolled limit. Off-axis predicted fields reduce commensurately at greater distances from the antenna in the antenna transition region. In the “far field” region of the antenna (starting at a distance of 578 meters from the antenna), the antenna directional characteristics have formed and the off-axis “far field” power density can be readily calculated using off-axis antenna discrimination specifications. At locations greater than eight degrees off-axis from the “main beam,” the manufacturer of the antenna specifies a side-lobe attenuation of 46.3 dB.3 Again using the methodology detailed in OET65, this off-axis attenuation results in a power density of 0.00 mW/cm², or 0.00 percent of the general population/uncontrolled limit.4 Controlled Access Area Exposure As described previously, access to the fenced area is limited and restricted to authorized, trained personnel. Additionally, all areas within 4.5 meters of the sides and back of the antenna, as well as areas located in the antenna “main beam” (as defined by footnote 3) have been conspicuously identified as having the potential to exceed occupational exposure limits. Access within these areas is permitted only when the Earth station transmitter has been disabled. 3 According to ViaSat, the antenna pattern meets the FCC specifications of §25.209 and thus has a gain of 8 dBi or less 8-degrees off-axis. 8 dBi is 46.3 dB less than the 54.3 dBi main-lobe antenna gain. 4 When rounded to nearest one-hundredth mW/cm² and percent. Cavell, Mertz & Associates, Inc.

Engineering Statement (page 4 of 4) With respect to worker safety, it is believed that based on the preceding analysis, excessive exposure would not occur because adequate physical separation has been established and maintained. On-site RF exposure measurements may also be undertaken to establish the bounds of safe working areas. Conclusion As demonstrated herein, excessive levels of RF energy will not be caused by strictly following the policies detailed herein. Consequently, neither the general public nor occupational staff will be exposed to RF levels in excess of the Commission’s guidelines. Access to the vicinity of the uplink antenna is restricted and controlled through the use of locked doors, boundary markers, conspicuous RFR warning signs, as part of an overall RF safety program. Certification The undersigned hereby certifies that the foregoing statement was prepared by him or under his direction, and that it is true and correct to the best of his knowledge and belief. Mr. Ryson is a senior engineer in the firm of Cavell, Mertz & Associates, Inc. Daniel G. Ryson December 7, 2011 Cavell, Mertz & Associates, Inc. 7839 Ashton Avenue Manassas, VA 20109 (703) 392-9090 Cavell, Mertz & Associates, Inc.


Document Created: 2011-12-09 13:50:51
Document Modified: 2011-12-09 13:50:51
© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC