Attachment Radiation Hazard Rep

This document pretains to SES-LIC-20130425-00342 for License on a Satellite Earth Station filing.

IBFS_SESLIC2013042500342_994460

                   AvL TECHNOLOGIES
                   designs for ultimate performance



                                 RADIATION HAZARD STUDY
                                              For
                                 AvL Technologies 1.6m Antenna

This analysis predicts the radiation levels around a proposed earth station complex, comprised of one
or more aperture (reflector) type antennas. This report is developed in accordance with the prediction
methods contained in OET Bulletin No. 65, "Evaluating Compliance with FCC Guidelines for Human
Exposure to Radio Frequency Electromagnetic Fields," Edition 97-01, pp 26-30. The maximum level of
non-ionizing radiation to which employees may be exposed is limited to a power density level of 5
milliwatts per square centimeter (5 mW/cm2) averaged over any 6 minute period in a controlled
environment and the maximum level of non-ionizing radiation to which the general public is exposed
is limited to a power density level of 1 milliwatt per square centimeter (1 mW/cm2) averaged over any
30 minute period in a uncontrolled environment. Note that the worse-case radiation hazards exist
along the beam axis. Under normal circumstances, it is highly unlikely that the antenna axis will be
aligned with any occupied area since that would represent a blockage to the desired signals, thus
rendering the link unusable.


Earth Station Technical Parameter Table

Antenna Actual Diameter                                          1.6 meters
Antenna Surface Area                                            2.01 sq. meters
Antenna Isotropic Gain                                          45.7 dBi
Number of Identical Adjacent Antennas*                             0
Nominal Antenna Efficiency (ε)                                  65%
Nominal Frequency                                             14250 MHz
Nominal Wavelength (λ)                                         0.021 meters
Maximum Transmit Power / Carrier                                 170 Watts
Number of Carriers                                                 2
Total Transmit Power                                             340 Watts
W/G Loss from Transmitter to Feed                                0.5 dB
Total Feed Input Power                                           303 Watts
Near Field Limit         Rnf = D²/4λ =                          30.4 Meters
Far Field Limit          Rff = 0.6 D²/λ =                       73.0 Meters
Transition Region      Rnf to Rff
*The Radiation Levels will be increased directly by the number of antennas indicated, on the
assumption that all antennas may illuminate the same area.

In the following sections, the power density in the above regions, as well as other critically important
areas will be calculated and evaluated. The calculations are done in the order discussed in OET Bulletin
65. In addition to the input parameters above, input cells are provided below for the user to evaluate
the power density at specific distances or angles.


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                   AvL TECHNOLOGIES
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1.0        At the Antenna Surface

The power density at the reflector surface can be calculated from the expression:

PDrefl =      4P/A =                                                    60.3 mW/cm² (1)
Where:        P = total power at feed, milliwatts
              A = Total area of reflector, sq. cm

In the normal range of transmit powers for satellite antennas, the power densities at or around the
reflector surface is expected to exceed safe levels. This area will not be accessible to the general
public. Operators and technicians should receive training specifying this area as a high exposure area.
Procedures must be established that will assure that all transmitters are rerouted or turned off before
access by maintenance personnel to this area is possible.


2.0        On-Axis Near Field Region

The geometrical limits of the radiated power in the near field approximate a cylindrical volume with a
diameter equal to that of the antenna. In the near field, the power density is neither uniform nor does
its value vary uniformly with distance from the antenna. For the purpose of considering radiation
hazard it is assumed that the on-axis flux density is at its maximum value throughout the length of
this region. The length of this region, i.e., the distance from the antenna to the end of the near field, is
computed as Rnf above.

The maximum power density in the near field is given by:

                 PDnf = (16 ε P)/( π D²) =                       39.2 mW/cm²         (2)
                                                      From 0 to 30.4 meters
Evaluation
 Uncontrolled Environment:                                  See Section 4
 Controlled Environment:                                    See Section 4



3.0        On-Axis Transition Region

The transition region is located between the near and far field regions. As stated in Bulletin 65, the
power density begins to vary inversely with distance in the transition region. The maximum power
density in the transition region will not exceed that calculated for the near field region, and the
transition region begins at that value. The maximum value for a given distance within the transition
region may be computed for the point of interest according to:

PDt =        (PDnf)(Rnf)/R = dependent on R                                 (3)
where:       PDnf = near field power density
             Rnf = near field distance
             R = distance to point of interest
15 North Merrimon Ave • Asheville, NC 28804 USA • 828.250.9950 • 828.250.9938 FAX • www.avltech.com


                 AvL TECHNOLOGIES
                 designs for ultimate performance



          For:                                               30.4 < R < 73.0 meters

We use Eq (3) to determine the safe on-axis distances required for the two occupancy conditions:

Evaluation:

Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu:         See Section 4
Controlled Environment Safe Operating Distance,(meters), Rsafec:           See Section 4



4.0    On-Axis Far-Field Region

The on- axis power density in the far field region (PDff) varies inversely with the square of the distance
as follows:

         PDff = PG/(4 π R²) = dependent on R                               (4)
         where: P = total power at feed
                 G = Numeric Antenna gain in the direction of interest
                 relative to isotropic radiator
                 R = distance to the point of interest
                                                             For: R > Rff = 73.0 meters

                                                                    PDff = 16.8 mW/cm²
                                                                           at Rff

We use Eq (4) to determine the safe on-axis distances required for the two occupancy conditions:

Evaluation:

Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu :           299 meters
Controlled Environment Safe Operating Distance,(meters), Rsafec :             134 meters



5.0    Off-Axis Levels at the FarField Limit and Beyond

In the far field region, the power is distributed in a pattern of maxima and minima (sidelobes) as a
function of the off-axis angle between the antenna center line and the point of interest. Off-axis power
density in the far field can be estimated using the antenna radiation patterns prescribed for the
antenna in use. Usually this will correspond to the antenna gain pattern envelope defined by the FCC
or the ITU, which takes the form of:

Goff = 32 - 25log(Θ)
for Θ from 1 to 48 degrees; -10 dBi from 48 to 180 degrees
(Applicable for commonly used satellite transmit antennas)
15 North Merrimon Ave • Asheville, NC 28804 USA • 828.250.9950 • 828.250.9938 FAX • www.avltech.com


                   AvL TECHNOLOGIES
                  designs for ultimate performance




Considering that satellite antenna beams are aimed skyward, power density in the far field will usually
not be a problem except at low look angles. In these cases, the off axis gain reduction may be used to
further reduce the power density levels.

For example: At one (1) degree off axis At the far-field limit, we can calculate the power density as:

  Goff = 32 - 25log(1) = 32 - 0 dBi = 1585 numeric
                               PD1 deg off-axis = PDff x 1585/G = 0.72 mW/cm²        (5)



6.0     Off-Axis power density in the Near Field and Transitional Regions

According to Bulletin 65, off-axis calculations in the near field may be performed as follows: assuming
that the point of interest is at least one antenna diameter removed from the center of the main beam,
the power density at that point is at least a factor of 100 (20 dB) less than the value calculated for the
equivalent on-axis power density in the main beam. Therefore, for regions at least D meters away
from the center line of the dish, whether behind, below, or in front under of the antenna's main beam,
the power density exposure is at least 20 dB below the main beam level as follows:

PDnf(off-axis) = PDnf /100 =                  0.39    mW/cm² at D off axis (6)

See page 5 for the calculation of the distance vs elevation angle required to achieve this rule for a
given object height.


7.0     Region Between the Feed Horn and Reflector

Transmissions from the feed horn are directed toward the reflector surface, and are confined within a
conical shape defined by the feed horn. The energy between the feed horn and reflector is conceded to
be in excess of any limits for maximum permissible exposure. This area will not be accessible to the
general public. Operators and technicians should receive training specifying this area as a high
exposure area. Procedures must be established that will assure that all transmitters are rerouted or
turned off before access by maintenance personnel to this area is possible.

Note 1:
Mitigation of the radiation level may take several forms. First, check the distance from the antenna to
the nearest potentially occupied area that the antenna could be pointed toward, and compare to the
distances appearing in Sections 2, 3 & 4. If those distances lie within the potentially hazardous
regions, then the most common solution would be to take steps to insure that the antenna(s) are not
capable of being pointed at those areas while RF is being transmitted. This may be accomplished by
setting the tracking system to not allow the antenna be pointed below certain elevation angles. Other
techniques, such as shielding may also be used effectively.




15 North Merrimon Ave • Asheville, NC 28804 USA • 828.250.9950 • 828.250.9938 FAX • www.avltech.com


                 AvL TECHNOLOGIES
                designs for ultimate performance



Evaluation of Safe Occupancy Area in Front of Antenna

The distance (S) from a vertical axis passing through the dish center to a safe off axis location in front
of the antenna can be determined based on the dish diameter rule (Item 6.0). Assuming a flat terrain
in front of the antenna, the relationship is:

S = (D/ sin α ) + (2h - D - 2)/(2 tan α)                                            (7)


Where:     α = minimum elevation angle of antenna
           D = dish diameter in meters
           h = maximum height of object to be cleared, meters

For distances equal or greater than determined by equation (7), the radiation hazard will be below safe
levels for all but the most powerful stations (> 4 kilowatts RF at the feed).

For                             D=                1.6        meters
                                h=                 3         meters
Then:
                                 α                 S
                                 5                32.1       meters
                                10                16.0       meters
                                15                10.7       meters
                                20                8.0        meters
                                25                6.4        meters
                                30                5.3        meters
                                45                3.5        meters

Suitable fencing or other barrier should be provided to prevent casual occupancy of the area in front of
the antenna within the limits prescribed above at the lowest elevation angle required.




15 North Merrimon Ave • Asheville, NC 28804 USA • 828.250.9950 • 828.250.9938 FAX • www.avltech.com



Document Created: 2013-04-25 13:36:06
Document Modified: 2013-04-25 13:36:06

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