Attachment Exhibit A

This document pretains to SES-MOD-20110302-00232 for Modification on a Satellite Earth Station filing.

IBFS_SESMOD2011030200232_872410

CapRock Communications, Inc. EXHIBIT A Radiation Hazard Study Seatel 75cm Ku This study analyzes the potential Radio Frequency (RF) human exposure levels caused by the Electro Magnetic (EM) fields of the above-captioned antenna. The mathematical analysis performed below complies with the methods described in the Federal Communications Commission Office of Engineering and Technology Bulletin No. 65 (1985 rev. 1997) R&O 96-326. Maximum Permisible Exposure There are two separate levels of exposure limits. The first applies to persons in the general population who are in an uncontrolled environment. The second applies to trained personnel in a controlled environment. According to 47 C.F.R. § 1.1310, the Maximum Permissible Exposure (MPE) limits for frequencies above 1.5 GHz are as follows: • General Population / Uncontrolled Exposure 1.0 mW/cm2 • Occupational / Controlled Exposure 5.0 mW/cm2 The purpose of this study is to determine the power flux density levels for the earth station under study as compared with the MPE limits. This comparison is done in each of the following regions: 1. Far-field region 2. Near-field region 3. Transition region 4. The region between the feed and the antenna surface 5. The main reflector region 6. The region between the antenna edge and the ground Input Parameters The following input parameters were used in the calculations: Parameter Value Unit Symbol Atenna Diameter: 0.75 m D Antenna Transmit Gain: 39.00 dBi G Trasmit Frequency: 14250 MHz f Feed Flange Diameter: 7.20 cm d Power Input to the Antenna: 5.00 W P Calculated Parameters The following values were calculated using the above input parameters and the corresponding formulas. Parameter Value Unit Symbol Formula 2 Anenna Surface Area: 0.44 m A πD 2/4 Area of Feed Flange: 40.72 cm2 a πd 2/4 2 2 2 Antenna Efficiency: 0.63 η Gλ /( π D ) Gain Factor: 7943.28 g 10G /10 Wavelength: 0.0211 m λ 300/ f 1 of 3

CapRock Communications, Inc. EXHIBIT A Behavior of EM Fields as a Function of Distance The behavior of the characteristics of EM fields varies depending on the distance from the radiating antenna. These characteristics are analyzed in three primary regions: the near-field region, the far-field region and the transition region. Of interest also are the region between the antenna main reflector and the subreflector, the region of the main reflector area and the region between the main reflector and ground. Figure 1. EM Fields as a Function of Distance For parabolic aperture antennas with circular cross sections, such as the antenna under study, the near-field, far- field and transition region distances are calculated as follows: Parameter Value Unit Formula Near Field Distance: 6.680 m Rnf = D2/(4λ) Distance to Far Field: 16.031 m Rff = 0.60D2/(λ) Distance of Trasition Region 6.680 m Rt = Rnf The distance in the transition region is between the near and far fields. Thus, Rnf ≤ Rt ≤ Rff . However, the power density in the transition region will not exceed the power density in the near-field. Therefore, for purposes of the present analysis, the distance of the transition region can equate the distance to the near-field. Power Flux Density Calculations The power flux density is considered to be at a maximum through the entire length of the near-field. This region is contained within a cylindrical volume with a diameter, D, equal to the diameter of the antenna. In the transition region and the far-field, the power density decreases inversely with the square of the distance. The following equations are used to calculate power density in these regions. 2 of 3

CapRock Communications, Inc. EXHIBIT A Parameter Value Unit Symbol Formula 2 Power Density in the Near-Field 2.871 mW/cm S nf 16.0 η P /(πD 2) Power Density in the Far-Field 1.230 mW/cm2 S ff GP /(4π R ff2) Power Density in the Trans. Region 2.871 mW/cm2 St Snf R nf /(R t) The region between the main reflector and the subreflector is confined within a conical shape defined by the feed assembly. The most common feed assemblies are waveguide flanges. This energy is determined as follows: Parameter Value Unit Symbol Formula Power Density at the Feed Flange 491.2 mW/cm2 S fa 4P / a The power density in the main reflector is determined similarly to the power density at the feed flange; except that the area of the reflector is used. Parameter Value Unit Symbol Formula 2 Power Density at Main Reflector 4.527 mW/cm S surface 4P / A The power density between the reflector and ground, assuming uniform illumination of the reflector surface, is calculated as follows: Parameter Value Unit Symbol Formula 2 Power Density between Reflector and Ground 1.132 mW/cm Sg P /A Table 1 summarizes the calculated power flux density values for each region. In a controlled environment, the only regions that exceed FCC limitations are shown below. These regions are only accessible by trained technicians who, as a matter of procedure, turn off transmit power before performing any work in these areas. Controlled Environment Power Densities mW/cm2 (5 mW/cm2) Far Field Calculation 1.230 Satisfies FCC Requirements Near Field Calculation 2.871 Satisfies FCC Requirements Transition Region 2.871 Satisfies FCC Requirements Region between Main and Subreflector 491.2 Exceeds Limitations Main Reflector Region 4.527 Satisfies FCC Requirements Region between Main Reflector and Ground 1.132 Satisfies FCC Requirements Table 1. Power Flux Density for Each Region In conclusion, the results show that the antenna, in a controlled environment, and under the proper mitigation procedures, meets the guidelines specified in 47 C.F.R. § 1.1310. 3 of 3


Document Created: 2011-03-02 11:56:28
Document Modified: 2011-03-02 11:56:28
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