Attachment Attachment 7

This document pretains to SES-MOD-20100302-00285 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2010030200285_803181

                                            Prepared by Andrew Corporation


                                   RADIATION HAZARD ANALYSIS




      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
                                                                                     2
      limited to a power density level of 1 milliwatt per square centimeter (1 mW/cm ) 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
      unuseable.

      The parameters which determine the radiation levels for the proposed earth station antenna site follows:
                                    Earth Station Technical Parameter Table

                     Antenna Actual Diameter                      (Enter value)         3.80 meters
                     Antenna Surface Area                                             11.3 sq. meters
                     Antenna Isotropic Gain                   (Enter value)           53.2 dBi
                     No. of Identical Adjacent Antennas       (Enter value)              0
                               Note: The Radiation Levels will be increased directly by the number of antennas
                                   indicated, on the assumption that all antennas may illuminate the same area.
                     Nominal Antenna Efficiency (ε)                                   65%
                     Nominal Frequency                        (Enter value)         14250 MHz
                     Nominal Wavelength (λ)                                        0.0211 meters
                     Maximum Transmit Power / Carrier         (Enter value)           12.7 Watts
                     Number of Carriers                       (Enter value)              1
                     Total Transmit Power                                             12.7 Watts
                     W/G Loss from Transmitter to Feed:       (Enter value)            1.0 dB
                     Total Feed Input Power                                             10 Watts

                                                                   2
                     Near Field Limit=           Rnf =            D /4λ =               171 meters
                                                                       2
                     Far-Field Limit =           Rff =            0.6 D /λ =            412 meters
                     Transition Region =                    Rnf        to         Rff

      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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                                             Prepared by Andrew Corporation


      1. At the Antenna Surface:

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

                                                                          2
                      PDrefl =      4P/A =             0.36      mW/cm                                  (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 will 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. 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:

                                    (16 ε P)/(πD ) =
                                                 2                                       2
                      PDnf =                                          0.00       mW/cm                  (2)
                                                                    from 0 to        171       meters
      Evaluation in Near Field Region:
                     Uncontrolled Environment:                    Complies to FCC Limits

                      Controlled Environment:                     Complies to FCC Limits


      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
                                             For:            171     < R <           412       meters


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                                             Prepared by Andrew Corporation


      We use Eq (3) to determine the safe on-axis distances required for the two occupancy conditions:
      Evaluation in Transistion Region:
       Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu: In N-F region, See Section 2

        Controlled Environment Safe Operating Distance,(meters), Rsafec:         In N-F region, See Section 2



      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:
                                              2                     dependent on R
                     PDff =           PG/(4πR ) =                                                     (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 > 412           meters
                                                                                        2
                                                    PDff =              0.00     mW/cm at Rff

      We use Eq (4) to determine the safe on-axis distances required for the two occupancy conditions:
      Evaluation in Far Field Region:
        Uncontrolled Environment Safe Operating Distance,(meters), Rsafeu : In N-F region, See Section 2

         Controlled Environment Safe Operating Distance,(meters), Rsafec :       In N-F region, See Section 2



      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)

      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

                                                                                        2
                     PD1 deg off-axis =           PDff x 1585/G =      0.0000    mW/cm                (5)


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                                          Prepared by Andrew Corporation




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                                            Prepared by Andrew Corporation

      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 =       0.000     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 Sub-reflector

      Transmissions from the feed horn are directed toward the subreflector surface, and are confined within a
      conical shape defined by the feed horn. The energy between the feed horn and subreflector 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 will 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.




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                                                Prepared by Andrew Corporation

                            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 =         3.8        meters
                              h=           2         meters        Enter clearance height required
                      Then:
                           α                S
                          10              16.8       meters
                          15              11.3       meters
                          20               8.6       meters
                          25               7.1       meters
                          30               6.0       meters
       Specific Elev:    41.2              4.7       meters        Enter minimum elevation angle required
       Specific Elev:     45               4.5       meters        Enter minimum elevation angle required

      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.




Rad Haz Report EMF - ver 20080521v1.xls              6/11/2008 11:07 AM                                               6



Document Created: 2009-08-25 15:32:08
Document Modified: 2009-08-25 15:32:08

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