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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