Attachment E910021 RadHaz Study

This document pretains to SES-RWL-20100929-01220 for Renewal on a Satellite Earth Station filing.

IBFS_SESRWL2010092901220_842411

                        Radiofrequency (RF) Radiation Hazard Study
                  License No. E910021: Chena Hot Springs (AT&T Alascom)
This report summarizes the non-ionizing radiofrequency (RF) exposure levels associated with the above antenna
system. RF prediction models and associated exposure limits referenced in this study are outlined in the
Federal Communications Commission (FCC) Office of Engineering and Technology (OET) Bulletin 65
Edition 97-01 (August 1997). The FCC-exposure limits define the level of RF energy that a person may be
continuously exposed without experiencing adverse health effects. This "safe" level, herein referred to
as Maximum Permissible Exposure (MPE) limit, is comprised of two-tiers: one for conditions which the public may
be exposed (General Population/Uncontrolled) and the other for exposure situations usually involving workers
(Occupational/Controlled). Therefore, the intent of this study is to define the maximum "worst-case"
RF exposure levels and compare the results relative to the applicable MPE limits.

Based upon the following system parameters, the applicable MPE limits are:           1.0   mW/cm^2 and
    5.0     mW/cm^2 for General Population/Uncontrolled and Occupational/Controlled environments,
respectively, as specified in 47 CFR Part 1.1310.
                                                  System Parameters
          Antenna Diameter (D1):          4.5       meters         Antenna Surface Area (D1a):    15.90    meters^2
         Feed horn Diameter (D2):        0.07       meters        Feed horn Surface Area (D2a):   0.004    meters^2
            Operating Frequency:         6175       MHz                         Wavelength ( ):   0.049    meters
  Antenna Gain (G), @ 6175 MHz:          46.2       dBi                        Numerical Gain: 41686.93835
Transmit Power @ Antenna Input*:         20.0       watts
Calculated Aperture Efficiency (n ):     0.49                   Center height above ground level:       4.55      meters

   * Based on 40 W maximum power amplifier rating, where the actual operating power level will be reduced
     by at least a factor of 2.0 (3 dB minimum output backoff, transmission loss, etc.). For purposes of
     study, this equates to an aggregate output EIRP for all carriers of      59.2       dBW maximum.

                                                  Hazard Assessment

For parabolic aperture antennas, three (3) regions are defined for predicting maximum RF exposure levels within
the main-beam (on-axis) path: near-field, transition, and far-field regions. RF prediction methods are based
on where the point-of-interest falls within these regions:

     1. The far field (Rff) region is determined by the following equation: 0.6 D^2/ . This equates to a linear
     distance of approximately            250.09     meters from the antenna. The maximum main beam RF
     exposure level (Sff), in terms of power density units, at this point can be calculated as follows:

                        Sff = PG / 40 (Rff)^2 =        0.11     mW/cm^2

     2. The near field (Rnf) region is determined by the following equation: D^2/ 4 . This equates to a linear
     distance of approximately          104.20        meters from the antenna. The maximum RF exposure level
     (Snf), in terms of power density units, within this region can be calculated as follows:

                          Snf = 0.4n P/ D1a =  0.25   mW/cm^2
                (Assume maximum value maintained throughout the near field region)


  ** The transition (Rt) region is between the near-field and far-field regions, defined as Rff - Rnf. This equates to a
     region extending   145.88    meters, beginning at        104.20 meters and ending             250.09      meters
     from the antenna. While the exposure intensity decreases inversely with the square of the distance in the




    February, 2005                                     Page 1 of 3


                  Radiofrequency (RF) Radiation Hazard Study - Continued
                 License No. E910021: Chena Hot Springs (AT&T Alascom)
                                           Hazard Assessment - Continued



     far field region, the exposure intensity decreases inversely with distance in the transition region. Therefore, the
     maximum RF exposure level in the transition region will not exceed the above calculated near field value (Snf).
     If the point-of-interest falls within the transition region, the estimated RF exposure level (St), in terms of power
     density units, can be calculated using the following mid-point (Rt) example:

                               St = Snf * Rnf / R =     0.15     mW/cm^2 - at mid-point of Rt
                                   note: where 'R' is the point-of-interest within the Rt



This prime focus antenna design uses a focal-point feed horn to direct RF energy towards the main reflector
dish. The following calculations are used to predict the RF exposure levels at the main reflector surface and
feed horn aperture:



    3. The maximum RF exposure level (Smain-surface) in front of the main reflector surface (at rim), in terms of
    power density units, can be calculated as follows:

                              Smain-surface = 0.4*P / D1a =         0.50     mW/cm^2

    4. The maximum RF exposure level at the feed horn surface (Sfeed), in terms of power density units,
    can be calculated as follows:

                                       Sfeed = 0.4*P / D2a =      2078.76 mW/cm^2




For evaluating accessible areas outside the main beam path, a practical estimation is to consider the maximum
allowable gain pattern envelope for fixed-satellite services. Specifically, the antenna gain shall lie below the
envelope defined as -10 dBi for angles greater than 48 degrees and less than/equal to 180 degrees from the main
lobe axis. In considering areas immediately below the main reflector rim, the maximum RF exposure levels
directed towards this region (Spoi), in terms of power density units, can be calculated as follows:

    5.                            Spoi = PG/40 (R)^2 =               0.003 mW/cm^2
                       Note : where 'R' is the point-of-interest is just below antenna rim, which
                        equates (in this case) to a centerline distance:         2.25    meters




   February, 2005                                       Page 2 of 3


                   Radiofrequency (RF) Radiation Hazard Study - Continued
                  License No. E910021: Chena Hot Springs (AT&T Alascom)
                                      Hazard Assessment - Summary
                            Summary of Calculated RF Exposure Levels
         Region                          Level (mW/cm^2)                             Assessment
 A.   Far Field (Rff),   250.09     meters, =         0.11                        Satisfies FCC MPE Limits
 B.   Near Field (Rnf),  104.20     meters, =         0.25                        Satisfies FCC MPE Limits
 C.   Rim of Main Reflector =                         0.50                        Satisfies FCC MPE Limits
 D.   Feed Horn Surface =                            2078.76         Potential to exceed FCC Occupational MPE Limit
 E.   Area below Antenna Rim =                        0.003                       Satisfies FCC MPE Limits


                                                    D
     C                                          Feed Horn
 Rim of Main                                                                                               A
  Reflector                                                                                             Far Field

                                                                    B
                                                                 Near Field




                                                                                                  E
                                                                                       Area Below Antenna Rim

                                                      Conclusion

The results of this study indicate that accessible ground level areas, surrounding the antenna base
and horizontal to the main beam axis, do not exceed the most restrictive FCC-General Population/Uncontrolled
MPE limit.

The highest RF exposure levels are isolated to regions located between the feed horn and main reflector surface,
which are typically inaccessible during normal operations. To ensure compliance with the FCC Occupational/Controlled
MPE limit, these areas shall be controlled (restricted access) and the antenna system de-energized during any
maintenance/service activities occurring within the main reflector or subreflector regions.

This study concludes that operation of this satellite earth station will not expose workers or public members
to RF levels in excess of the applicable MPE limits. Therefore, in accordance with 47 CFR Part 1.1307 (b),
preparation and submission of an Environmental Assessment (EA) is not required.


         Performed by:      Kimberly A. Kantner, RRPT                    AT&T / EH&S - Radiation Safety Office
                 Date:    09/27/10                                        Phone No.      407 277-1641




      February, 2005                                   Page 3 of 3



Document Created: 2010-09-29 15:36:02
Document Modified: 2010-09-29 15:36:02

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