Radiation Hazard Analysis

0126-EX-ML-2016 Text Documents

BlackSky Global, LLC

2016-06-21ELS_178443

Radiation Hazard Report Exhibit
Page 1 of 6

Analysis of Non-Ionizing Radiation for an 18.3-Meter Parabolic Antenna Earth
Station System

This report analyzes the non-ionizing radiation levels for an 18.3-meter parabolic antenna 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 6
Table 3. Formulas and Parameters Used for Determining Power Flux Densities

Parameter Symbol Formula Value Units
Ant Largest Dimension D Input 18.3 m
Frequency F Input 450.2 MHz
Wavelength 𝜆𝜆 300/F 0.666666667 m
Transmit Power P Input 100 W
Antenna Gain (dBi) G es Input 35 dBi
Antenna Gain (factor) G 10Ges /10 3162.27766 n/a
Pi 𝜋𝜋 Constant 3.141592654 n/a
Antenna Efficiency 𝜂𝜂 Input 0.42 n/a
Ant Equiv Surface Area A Surface 2
Gλ /(4𝜋𝜋)/𝜂𝜂 263.0219909 m2

Radiation Hazard Report Exhibit
Page 3 of 6
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)
= 301.5 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)
= 0.277 W/m2
= 0.0277 mW/cm2

2. Main Reflector Calculation
Note that the RF power out of the amplifier is 100 W. The transmitted power will be less than 100 W
due to line loss between the amplifier and antenna, which is predicted to be 4.5 dB. These calculations
assume zero line loss in order to provide a worst case scenario in the case that line loss is lower than
predicted.
The power density S surface in the main reflector is determined as follows:
Main Reflector Surface Power Density Ssurface = 4P/Asurface (3)
= 1.521 W/m2
= 0.1521 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) (3)
= 125.6 m

The maximum power density in the Near Field can be determined from the following equation:
Near Field Power Density Snf = 4ηP/Asurface (4)
= .646 W/m2
= .0646 mW/cm2

Radiation Hazard Report Exhibit
Page 4 of 6
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
highest power density the antenna can produce in any of the regions away from the antenna. The
power density at a distance R tz can be determined from the following equation:
Transition Region Power Density Stz = Snf R nf /R tz (5)
= 0.0646 mW/cm2

R tz is calculated at a distance of 125.6 meters from the antenna, which is the worst-case distance. This
is the edge of the near-field, R nf.

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 (6)
= 0.380 W/m2
= 0.0380 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 (R ff = 8.36 m) S ff 0.0277 Satisfies FCC MPE
Main Reflector Surface S surface 0.1521 Satisfies FCC MPE
Near Field (R nf = 3.48 m) S nf 0.0646 Satisfies FCC MPE
Transition Region (R nf < R tz < R ff ) S tz 0.0646 Satisfies FCC MPE
Between Reflector and Ground Sg 0.0380 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 (R ff = 8.36 m) S ff 0.0277 Satisfies FCC MPE
Main Reflector Surface S surface 0.1521 Satisfies FCC MPE
Near Field (R nf = 3.48 m) S nf 0.0646 Satisfies FCC MPE
Transition Region (R nf < R tz < R ff ) S tz 0.0646 Satisfies FCC MPE

Radiation Hazard Report Exhibit
Page 5 of 6
Between Reflector and Ground Sg 0.0380 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 6 of 6
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 0.3 mW/cm2 for the
Uncontrolled Areas, and the MPE limits of 1.5 mW/cm2 for the Controlled Areas.
The earth station parabolic antenna is in the middle of a fenced in area with locked gate on top of a 20’
tower with a locked access cover; 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: 2016-06-21 09:53:50
Document Modified: 2016-06-21 09:53:50

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