Attachment RadhadExhibit

This document pretains to SES-STA-20070530-00734 for Special Temporal Authority on a Satellite Earth Station filing.

IBFS_SESSTA2007053000734_570656

Comtech Mobile Datacom Corporation FCC Form 312, Schedule B Exhibit A, Page 1 Radiation Hazard Study – Question 28 Comtech Mobile Datacom Corporation Mobile Earth Station Terminal May 30, 2007 Background Comtech Mobile Datacom Corporation (“CMDC”) designs, manufactures, and is licensed to operate Mobile Earth Station Terminals (“MESs”) in spectrum allocated to the Mobile Satellite Service under the Federal Communications Commission guidelines of Part 25, Title 47 of the Code of Federal Regulations. CMDC is requesting a modification to its existing blanket license. Completion of a routine environmental analysis for RF exposure (as described in Federal Communications Commission Office of Engineering and Technology Bulletin 65 (“Bulletin 65”)) due to emissions from the MES is one of the requirements to modify the existing blanket license. Bulletin 65 identifies two parameters relating to equipment type and usage that determine the appropriate testing methods and limits. First, devices may be classified as either Mobile or Portable. A Mobile device is intended for use in other than fixed locations and should be separated from the user or bystanders by at least 20 centimeters. Portable devices are intended to be operated within 20 centimeters of the user or bystander. Second, the exposure must be deemed Occupational/Controlled Exposure or General Population/Uncontrolled Exposure. Occupational/Controlled Exposure applies where persons are exposed due to their employment or when they have been made aware of the potential for exposure and are able to exercise control over their exposure. Cases where the general public is exposed or where workers are not fully aware of the potential for exposure or are unable to exercise control over the amount of their exposure fall into the General Population/Uncontrolled Exposure category. CMDC MESs fit into the Mobile and General Population/Uncontrolled Exposure categories. As such, the permissible radiation level may be determined using either Maximum Permissible Exposure or Specific Absorption Rate techniques. CMDC elects to use a Maximum Permissible Exposure analysis using the limits for General Population/Uncontrolled Exposure for frequencies above 1500 MHz shown in section B of the table below.

Comtech Mobile Datacom Corporation FCC Form 312, Schedule B Exhibit A, Page 2 Analysis Method A Maximum Permissible Exposure analysis will be done using the methods described in Bulletin 65 and the source-based time-averaging methods described in Title 47 of the Code of Federal Regulations Part 2.1091. The source-based averaging allows scaling of the exposure level based on the inherent duty cycle of the MES. CMDC’s MESs are limited to a maximum transmission duty cycle of 52% (a 1.552 second transmission burst every 3.0 seconds). Bulletin 65 offers several methods for calculating the RF Power Density. Three of these methods seem appropriate for this analysis. First, the equations below will predict the power density in the antenna far field and will overstate the density in the near field.

Comtech Mobile Datacom Corporation FCC Form 312, Schedule B Exhibit A, Page 3 Second, the power density may be determined for an antenna close to a ground plane. The following equation provides this result based on 100% reflection from the ground plane. The power density determined by this method will be four times that of the density determined in the far field. Third, the Environmental Protection Agency has recommended a more realistic approximation of those results in a power density increase of 2.56 above the far field case. This method seems most representative of the typical operating conditions for CMDC’s MESs and is the method adopted for this analysis.

Comtech Mobile Datacom Corporation FCC Form 312, Schedule B Exhibit A, Page 4 Analysis The separation distance required to produce an RF power density less than one milliwatt per square centimeter will be calculated for all possible antennas. The calculations will be done for the maximum antenna input power of 6 dBW and for a maximum duty cycle of 52 %. The antennas that are available for use are characterized in the table below. Antenna Antenna Size Antenna Gain Type ID (meters) (dBi) A1/INT Quadrafilar Helix 0.15 2.9 A2/EXT Quadrafilar Helix 0.15 4.8 A2/EXT Patch 0.06 4.0 A4/INT Quadrafilar Helix 0.15 5.0 A5/EXT Quadrafilar Helix 0.27 3.9 A6/INT Quadrafilar Helix 0.18 3.7 A7/INT Quadrafilar Helix 0.18 6 A8/EXT Quadrafilar Helix 0.18 3.7 Using the maximum power into the antenna of 6 dBW, a duty cycle of 52% and the antenna gains from the table above; the minimum separations to achieve one milliwatt per square centimeter power densities are calculated and listed in the table below. Separation distance for 1 mW Antenna ID Type per square centimeter Power Density (cm) A1/INT Quadrafilar Helix 29 A2/EXT Quadrafilar Helix 36 A3/EXT Patch 33 A4/INT Conformal Patch 37 A5/EXT Quadrafilar Helix 32 A6/INT Quadrafilar Helix 31 A7/INT Quadrafilar Helix 41 A8/EXT Quadrafilar Helix 31 The typical CMDC MES is installed on the top surface of a land vehicle, ship, or aircraft. Distances to operating personnel and the general population will be greater than the separation distances calculated above.

Comtech Mobile Datacom Corporation FCC Form 312, Schedule B Exhibit A, Page 5 The table below indicates the typical CMDC MES mounting location for various applications and the minimum distance necessary to prevent a hazard to operators and the general population. Typical minimum installation Minimum distance necessary Application separation from people (cm) to prevent hazard (cm) Trucking 90 41 Rail 300 41 Container 200 41 Boats >300 41 Aviation 75 41 Conclusions The preceding analysis shows that the CMDC MESs meet the Federal Communications Commission guidelines for RF exposure.


Document Created: 2007-06-01 09:27:07
Document Modified: 2007-06-01 09:27:07
© 2025 FCC.report
This site is not affiliated with or endorsed by the FCC