Radiation Hazard S band

1136-EX-ST-2013 Text Documents

BlackSky Global, LLC

2013-12-19ELS_144211

RKF Engineering Solutions, LLC 1229 19th St. NW, Washington, DC 20036 Phone 202.463.1567 Fax 202.463.0344 www.rkf-engineering.com Radiation Hazard Report – 3.7-meter Antenna This report analyzes electro-magnetic non-ionizing radiation which would accompany the operation of the Black Sky 3.7-meter earth station antenna (manufactured by Orbit and known as model AL-1000-SX) which will be used to uplink S-Band signals to their two satellites. The antenna will be located at Tukwila, WA where the site elevation is 15.9m AMSL. The antenna will be transmitting at S-Band (2025-2110 MHz). This report provides calculations which are used to determine the transmission power density in the “Far Field”, the “Near Field” and the “Transition Region”. Additional analysis determines the region between the “Main Reflector and the Subreflector”, the “Main Reflector Region” and the “Main Reflector and the Ground”. Accordingly, we use the “Maximum Permissible Exposure” limits published by the FCC OET 65 Bulletin for the General Population/Uncontrolled Exposure and the limits for the Occupational/Controlled Exposure. The results of the calculations meet the FCC’s OET Bulletin, No. 65, with the exception of the “Main Reflector and the Subreflector”, where a Hazard Zone is located. The Hazard Zone, the region between the “Main Reflector and the Subreflector”, is a dangerous location for workers to be in, doing tests, or replacing various equipment, or doing anything required their having a reason to be located there. All workers will be advised that being in the Hazard Zone while the antenna is transmitting is strictly forbidden. Black Sky will have specific rules placed on numerous highlighted signs for all employees and temporary workers to see. The signs will be available in the area of work and elsewhere around the antenna where it can be seen at any time. In addition, whenever the antenna is transmitting to the satellite, red lights will be illuminated alerting workers and visitors to be careful to stay away from the antenna and any other equipment which may be operating. Black Sky will maintain a 7-day- per-week hotline at its Mission Control Center. Make certain that no one is near the antenna during transmissions. The results of the calculations performed are all within the FCC’s requirements except for the Hazard Zone.

Far Field Analysis The calculation for the Far Field location includes the actual distance to where the far field begins, followed by a calculation of the power density at that location. Near Field Analysis The power flux density will be at its highest value the whole length of the Near Field area. We evaluate end of the Near Field, followed by the maximum power density in that area. Transition Area In the transition area between the Near and Far Fields, the power density decreases inversely with the square of the distance. Main Reflector and Subreflector The subreflector of the antenna transmits directly to the Main Reflector which reflects the transmissions to free space. The maximum amount of power density in this area will be calculated at the subreflector. Main Reflector Area Power density at the 3.7 meter dish is analyzed and the calculation provided. Area from the Main Reflector to nearby Ground The power density in this area will be determined by calculation of the nearby ground area. Conclusions The following page provides the details of each analyzed area. The results of the calculations demonstrate that the Black Sky 3.7-meter antenna will meet all required values of power density except for the area between the subreflector and the main reflector, where signage will be used to prevent any dangerous exposure to the public or working employees. RKF Engineering Solutions, LLC 1229 19th Street NW, Washington DC 20036 Page 2

S-Band Power Density S-Band Power Inputs Units Calculations Density Units S-Band Diameter 3.7 m Far Field distance 55.4445 m S-Band Gain 33.5 dBi On-Axis Power Density Far Field 0.579526358 W/m^2 S-Band Gain 2238.72114 0.057952636 mW/cm^2 S-band EIRP 41.65 dBW Power S-Band 8.15 dBW Near Field Distance 23.101875 m Freq (S-Band) 2025 MHz Near Field Power Density 1.352869552 W/m^2 Wavelength S-Band 0.14814815 m 0.135286955 mW/cm^2 Antenna efficiency S-Band 0.36365475 Power in Watts 10 W Transition Distance 39.2731875 m S-Band Subreflector Diameter 123.333333 cm Transition Region Power Density 0.795805619 W/m^2 S-Band Subreflector Area 11946.7787 cm^2 0.079580562 mW/cm^2 S-Band Antenna Surface Area 10.7521009 m^2 Flange/Reflector 3.348182879 mW/cm^2 Main Reflector Region 3.720203199 W/m^2 0.37202032 mW/cm^2 Antenna/Ground 0.9300508 W/m^2 0.09300508 mw/cm^2


Document Created: 2013-12-19 13:16:12
Document Modified: 2013-12-19 13:16:12
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