Radiation Hazard S band general

0831-EX-PL-2014 Text Documents

BlackSky Global, LLC

2014-12-10ELS_156800

Radiation Hazard Report Exhibit
Page 1 of 5

Analysis of Non-Ionizing Radiation for a 3.7-Meter Dish Antenna Earth Station
System

This report analyzes the non-ionizing radiation levels for a 3.7-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

Radiation Hazard Report Exhibit
Page 2 of 5
Table 3. Formulas and Parameters Used for Determining Power Flux Densities

Parameter Symbol Formula Value Units
Ant Largest Dimension D Input 3.7 m
Ant Equiv Surface Area ASurface 𝜋𝜋D2 /4 10.75 m2
Frequency F Input 2071.875 MHz
Wavelength 𝜆𝜆 300/F 0.145 m
Transmit Power P Input 25 W
Antenna Gain (dBi) Ges Input 34.4 dBi
Antenna Gain (factor) G 10Ges /10 2754 n/a
Pi 𝜋𝜋 Constant 3.141592654 n/a
2 0.427 n/a
Antenna Efficiency 𝜂𝜂 Gλ /(4𝜋𝜋)/Asurface

Radiation Hazard Report Exhibit
Page 3 of 5
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 /𝜆𝜆 (1)
= 56.7 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/(4𝜋𝜋R ff 2 ) (2)
= 1.70 W/m2
= 0.170 mW/cm2

2. Main Reflector Calculation
The power density Ssurface in the main reflector is determined as follows:
Main Reflector Surface Power Density Ssurface = 4P/Asurface (3)
= 9.30 W/m2
= 0.930 mW/cm2

3. 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 /(4𝜆𝜆) (4)
= 23.64 m

The maximum power density in the Near Field can be determined from the following equation:
Near Field Power Density Snf = 4ηP/Asurface (5)
= 3.97 W/m2
= 0.397 mW/cm2

4. 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

Radiation Hazard Report Exhibit
Page 4 of 5
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)
= 0.397 mW/cm2

Rtz is calculated at a distance of 23.64 meters from the antenna, which is the worst case; it is the edge
of the near-field boundary, Rnf.

5. 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 )
= 2.33 W/m2
= 0.233 mW/cm2

6. 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 = 56.7 m) Sff 0.170 Satisfies FCC MPE
Main Reflector Surface Ssurface 0.93 Satisfies FCC MPE
Near Field (Rnf = 23.6 m) Snf 0.397 Satisfies FCC MPE
Transition Region (Rnf < Rtz < Rff) Stz 0.397 Satisfies FCC MPE
Between Reflector and Ground Sg 0.233 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 = 56.7 m) Sff 0.170 Satisfies FCC MPE
Main Reflector Surface Ssurface 0.93 Satisfies FCC MPE
Near Field (Rnf = 23.6 m) Snf 0.397 Satisfies FCC MPE
Transition Region (Rnf < Rtz < Rff) Stz 0.397 Satisfies FCC MPE
Between Reflector and Ground Sg 0.233 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.

Radiation Hazard Report Exhibit
Page 5 of 5
7. Conclusions
Based upon the above analysis, it is concluded that FCC RF Guidelines have not been exceeded in any
of the zones in the Uncontrolled (Table 4) or the Controlled (Table 5) environments. 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. 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: 2014-12-09 12:19:25
Document Modified: 2014-12-09 12:19:25

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