Exhibit 5 7m Rad Haz Study

0075-EX-CN-2018 Text Documents

BlackSky Global, LLC

2018-01-29ELS_203984

BlackSky Global, LLC                                                                            Exhibit 5
Radiation Hazard Report                                                                       Page 1 of 5


                         Analysis of Non-Ionizing Radiation for a
                      7.3-Meter Dish Antenna Earth Station System

This report analyzes the non-ionizing radiation levels for a 7.3-meter earth station system. The analysis
and calculations performed in this report comply with the methods described in the FCC Office of
Engineering and Technology’s General RF Exposure Guidance, 447498 D01 v05r02. The radiation safety
limits used in the analysis are in conformance with Title 47 Chapter I, Subchapter A, Part 1, Subpart I,
Section 1.1310. Section 1.1310 specifies that there are two separate tiers of exposure limits that are
dependent on the situation in which the exposure takes place and/or the status of the individuals who
are subject to the exposure. The Maximum Permissible Exposure (MPE) limits for persons in a General
Population/Uncontrolled environment are shown in Table 1. The General Population/Uncontrolled
MPE is a function of transmit frequency and is for an exposure period of thirty minutes or less. The
MPE limits for persons in an Occupational/Controlled environment are shown in Table 2. The
Occupational MPE is a function of transmit frequency and is for an exposure period of six minutes or
less. The purpose of the analysis described in this report is to determine the power flux density levels
of the earth station in the far-field, near-field, transition region, and between the antenna edge and
the ground and to compare these levels to the specified MPEs.
                 Table 1. Limits for General Population/Uncontrolled Exposure (MPE)

                          Frequency Range (MHz)            Power Density (mW/cm2)
                                 0.3 - 1.34                          100
                                 1.34 - 30                  180/Frequency(MHz)^2
                                  30-300                             0.2
                                 300-1500                   Frequency(MHz)/1500
                               1500-100,000                           1


                      Table 2. Limits for Occupational/Controlled Exposure (MPE)

                          Frequency Range (MHz)            Power Density (mW/cm2)
                                  0.3-3.0                            100
                                  3.0-30                    900/Frequency(MHz)^2
                                  30-300                              1
                                 300-1500                    Frequency(MHz)/300
                               1500-100,000                           5


BlackSky Global, LLC                                                                          Exhibit 5
Radiation Hazard Report                                                                     Page 2 of 5


             Table 3. Formulas and Parameters Used for Determining Power Flux Densities

 Parameter                       Symbo        Formula                  Value        Units
                                    l
 Ant Largest Dimension             D            Input                   7.3           m
 Ant Equiv Surface Area          ASurface      𝜋D2 /4                  41.9          m2
 Subreflector Diameter              d           Input                  0.61           m
 Subreflector Surface Area        ASub         𝜋d2 /4                 0.292          m2
 Frequency                          F           Input               2071.875         MHz
 Wavelength                         𝜆          300/F                  0.145           m
 Transmit Power                     P           Input                   50            W
 Antenna Gain (dBi)                Ges          Input                   41           dBi
 Antenna Gain (factor)             G          10Ges /10              12589           n/a
 Pi                                𝜋          Constant            3.141592654        n/a
                                            2                         0.501          n/a
 Antenna Efficiency                 𝜂     Gλ /(4𝜋)/Asurface




1. Far Field Distance Calculation
The distance to the beginning of the far field can be determined from the following equation:
     Distance to the Far Field Region                    R ff = 0.60 D2 /𝜆                  (1)
                                                              = 221.0 m


The maximum main beam power density in the far field can be determined from the following
equation:
     On-Axis Power Density in the Far Field              Sff = GP/(4𝜋R ff 2 )               (2)
                                                             = 0.10 W/m2
                                                             = 0.010 mW/cm2


2. Subreflector Calculation
The power density Ssub in the subreflector is determined as follows:
     Subreflector Surface Power Density                  Ssub = 4P/Asub                     (3)
                                                              = 684.4 W/m2
                                                              = 68.44 mW/cm2
3. Main Reflector Calculation
The power density Ssurface in the main reflector is determined as follows:
     Main Reflector Surface Power Density                Ssurface = 4P/Asurface             (3)
                                                                  = 4.78 W/m2
                                                                  = 0.478 mW/cm2


BlackSky Global, LLC                                                                             Exhibit 5
Radiation Hazard Report                                                                        Page 3 of 5




4. Near Field Calculation
Power flux density is considered to be at a maximum value throughout the entire length of the defined
Near Field region. The region is contained within a cylindrical volume having the same surface area as
the antenna. Past the boundary of the Near Field region, the power density from the antenna
decreases linearly with respect to increasing distance.
The distance to the end of the Near Field can be determined from the following equation:
     Extent of the Near Field                            R nf = D2 /(4𝜆)                       (4)
                                                              = 92.1 m


The maximum power density in the Near Field can be determined from the following equation:
     Near Field Power Density                            Snf = 4ηP/Asurface                    (5)
                                                             = 2.39 W/m2
                                                             = 0.239 mW/cm2


5. Transition Region Calculation
The Transition region is located between the Near and Far Field regions. The power density begins to
decrease linearly with increasing distance in the Transition region. While the power density decreases
inversely with distance in the Transition region, the power density decreases inversely with the square
of the distance in the Far Field region. The maximum power density in the Transition region will not
exceed that calculated for the Near Field region. The power density calculated in Section 2 is the
highest power density the antenna can produce in any of the regions away from the antenna. The
power density at a distance Rtz can be determined from the following equation:
     Transition Region Power Density                     Stz = Snf R nf /R tz                  (6)
                                                             = 0.239 mW/cm2


Rtz is calculated at a distance of 143.0 meters from the antenna, which is the worst case; it is the edge
of the near-field boundary, Rnf.



6. Region between the Antenna and the Ground
Assuming uniform illumination of the antenna surface, the power density between the antenna and
the ground can be determined from the following equation:
     Power Density between Antenna and Ground            Sg = P/Asurface                      (7 )
                                                            = 1.19 W/m2
                                                            = 0.119 mW/cm2


BlackSky Global, LLC                                                                            Exhibit 5
Radiation Hazard Report                                                                       Page 4 of 5




7. Summary of Calculations


             Table 4. Summary of Expected Radiation Levels for Uncontrolled Environment

                                       Calculated Maximum Radiation Power
 Region                                         Density Level (mW/cm2             Hazard Assessment
 Far Field (Rff = 343.1 m)                 Sff                 0.103            Satisfies FCC MPE
 Subreflector Surface                     Ssub                 68.44            Exceeds limitations
 Main Reflector Surface                  Ssurface              0.478            Satisfies FCC MPE
 Near Field (Rnf = 143.0 m)                Snf                 0.239            Satisfies FCC MPE
 Transition Region (Rnf < Rtz < Rff)       Stz                 0.239            Satisfies FCC MPE
 Between Reflector and Ground              Sg                  0.119            Satisfies FCC MPE


               Table 5. Summary of Expected Radiation Levels for Controlled Environment

                                       Calculated Maximum Radiation Power
 Region                                         Density Level (mW/cm2             Hazard Assessment
 Far Field (Rff = 343.1 m)                   Sff                0.103           Satisfies FCC MPE
 Subreflector Surface                       Ssub                68.44           Exceeds limitations
 Main Reflector Surface                    Ssurface             0.478           Satisfies FCC MPE
 Near Field (Rnf = 143.0 m)                  Snf                0.239           Satisfies FCC MPE
 Transition Region (Rnf < Rtz < Rff)         Stz                0.239           Satisfies FCC MPE
 Between Reflector and Ground                Sg                 0.119           Satisfies FCC MPE


It is the applicant's responsibility to ensure that the public and operational personnel are not exposed
to harmful levels of radiation.

8. Conclusions
Based upon the above analysis, it is concluded that FCC RF Guidelines have been exceeded in one of
the zones in the Uncontrolled (Table 4) and one of the zones in the Controlled (Table 5) environment.
The applicant proposes to comply with the Maximum Permissible Exposure (MPE) limits of 1.0
mW/cm**2 for the Uncontrolled Areas, and the MPE limits of 5.0 mW/cm**2 for the Controlled Areas.
The earth station dish antenna will be mounted on a platform; so the applicant agrees that the
antenna will be in an area secured from the public and worker personnel not familiar with the earth
station system. The only zone in Table 4 (Uncontrolled Environment) in which the FCC MPE limits are
exceeded is between the main reflector and the subreflector, which will be well within the secured
area. The only zone in Table 5 (Controlled Environment) in which the FCC MPE limits are exceeded is
between the main reflector and the subreflector, which will only be accessed by personnel while the


BlackSky Global, LLC                                                                                Exhibit 5
Radiation Hazard Report                                                                           Page 5 of 5


transmitter is turned off. Non-assigned worker personnel and the general public must be accompanied
by knowledgeable earth station personnel when they enter the earth station secured area.
The applicant agrees to abide by the conditions specified in Condition 5208 provided below:

       Condition 5208 - The licensee shall take all necessary measures to ensure that the antenna does not
       create potential exposure of humans to radiofrequency radiation in excess of the FCC exposure limits
       defined in 47 CFR 1.1307(b) and 1.1310 wherever such exposures might occur. Measures must be taken
       to ensure compliance with limits for both occupational/controlled exposure and for general
       population/uncontrolled exposure, as defined in these rule sections. Compliance can be accomplished in
       most cases by appropriate restrictions such as fencing.
       Requirements for restrictions can be determined by predictions based on calculations, modeling or by
       field measurements. The FCC's OET Bulletin 65 (available on-line at www.fcc.gov/oet/rfsafety) provides
       information on predicting exposure levels and on methods for ensuring compliance, including the use of
       warning and alerting signs and protective equipment for worker.



Document Created: 2018-01-19 18:08:56
Document Modified: 2018-01-19 18:08:56

© 2024 FCC.report
This site is not affiliated with or endorsed by the FCC