Attachment RF_Statement.pdf

This document pretains to SES-LIC-20050912-01243 for License on a Satellite Earth Station filing.

IBFS_SESLIC2005091201243_454136

                             Engineering Statement
                   RADIOFREQUENCY EXPOSURE CALCULATIONS
                                             prepared for
                                 Gray Television Licensee, Inc.



        Gray Television Licensee, Inc. (“Gray”) is applying for a license to operate a transportable
“KU Band” satellite uplink. The uplink transmit antenna would be located on a vehicle roof and
operated at various locations throughout the United States. The instant study was completed to
evaluate the potential for human exposure to radiofrequency electromagnetic field in accordance
with the guidelines established by the Federal Communications Commission (“FCC”). In particular,
the study determined whether exposure to radiofrequency (“RF”) electromagnetic field from this
antenna would exceed FCC maximum permissible exposure limits to the general public and to
occupational workers, at locations in the vicinity of the uplink antenna, based on data provided by
the applicant and representatives of the equipment manufacturers.


Human Exposure to Radiofrequency Electromagnetic Field
        The Gray proposed operation was evaluated using the procedures outlined in FCC OET
Bulletin No. 65 (“OET 65"). OET 65 describes a means of determining whether a proposed facility
exceeds the RF exposure guidelines specified in §1.1310 of the Rules. Under present Commission
policy, a facility may be presumed to comply with the limits in §1.1310 if it satisfies the exposure
criteria set forth in OET 65. Based upon that methodology, and as demonstrated in the following,
the transmitting system under study will comply with the cited adopted guidelines at publicly
accessible locations when procedures described herein are followed.


Public Exposure
        According to Gray, the uplink antenna will be operated from a truck roof with a center of
radiation height of approximately 3.5 meters above the ground. The mechanical design of the
mounting equipment is optimized to orient the antenna toward satellites which operate well above
the horizon. With the elevation of the antenna and considering the look angle range, the nearest
location to the antenna at two meters above ground is greater than one dish diameter from the main
beam.




                                     Cavell, Mertz & Davis, Inc.


                                      Engineering Statement
                                             (page 2 of 5)


       Prevention of public exposure by predicted RF electromagnetic field in excess of the general
population/uncontrolled limit1 depends on adherence to the following operational guidelines by the
Gray technicians. To assure that no publicly accessible area is within the “main beam” of the uplink
antenna, sites and satellites will be selected such that the elevation angle of the antenna will always
exceed five degrees (and at least one dish diameter) above the horizon, nearby buildings, and places
accessible by the public.


       Because the instant antenna is of a transportable design, permanently installed fences and
gates are impractical. Therefore, the use of crowd control stanchions, cones, and conspicuous RF
exposure warning signs will be used to prevent public access in areas near the uplink antenna that
are known to exceed the FCC’s general population / uncontrolled MPE limit. These areas will be
defined either by measurements made by qualified, on-site, personnel or by the calculations
described herein.


       Based on data provided by the applicant, the following parameters were used in the study:



            Antenna Manufacturer                       AVL
            Antenna Model                              AVL-12MUSA
            Center Frequency                           14.250 GHz
            Wavelength at Center Frequency             0.02103807 meters
            Max Average Antenna Input Power            79.6 Watts
            Antenna Diameter                           1.2 meter
            Antenna Gain                               43.5 dBi
            Antenna Gain Ratio                         22387.2
            Aperture Efficiency                        0.697




       1
         The general population/uncontrolled maximum permissible exposure (“MPE”) limit of 1 mW/cm² for
14,250 MHz is specified in §1.1310 of the Rules.



                                      Cavell, Mertz & Davis, Inc.


                                            Engineering Statement
                                                     (page 3 of 5)


       The area in the immediate vicinity of the antenna is known as the “near field region.” In this
region (17.1 meters in the case at hand), the antenna directional characteristics of have not fully
formed. Therefore, antenna manufacturer “off-axis” discrimination specifications cannot be utilized
for the purpose of determining potential RF exposure.                      OET 65 provides a methodology
(Equation 13) for calculating an absolute “worst case” exposure figure within this region.
Additionally, OET 65 specifies that the “worst case” power density would be reduced by 20 dB at
locations at least one antenna diameter (1.2 meters) off-axis from the “main beam” of the antenna.
In this instance, the predicted off-axis, near field is 0.197 mW/cm², or 19.7 percent of the general
population/uncontrolled limit. Off-axis predicted fields reduce commensurately at greater distances
from the antenna in the antenna transition region.


       In the “far field” region of the antenna (in this case, starting at a distance of 41.07 meters
from the antenna2), the antenna directional characteristics have formed, and the off-axis “far field”
power density can be readily calculated using “off-axis” antenna discrimination specifications. At
locations greater than four degrees off-axis from the “main beam,” the manufacturer of the proposed
antenna specifies a minimum side-lobe attenuation of 36 dB. Again using the methodology detailed
in OET65, this “off-axis” attenuation is predicted to result in a power density of 0.0049 mW/cm²,
or 0.49 percent of the general population/uncontrolled limit.


       As shown above, the “compliant area” is defined by any location more than four degrees and
1.2 meters away from the satellite antenna “main beam.” Appropriate crowd control devices
(described earlier) would be deployed 2-3 meters from the uplink truck (to prevent unauthorized
access) and at sufficient distances in the direction of the antenna “main beam” to assure that publicly
accessible locations do not result in “head heights” approaching the five-degree and 1.5 meter
non-compliant area.




       2
           The transition region between the near field and far field would lie between 17.1 and 41.07 meters.



                                            Cavell, Mertz & Davis, Inc.


                                      Engineering Statement
                                              (page 4 of 5)


Controlled Access Area Exposure

        Access to the vicinity of the antenna will be limited and restricted to authorized, trained
personnel. Using data provided by the applicant, the potential for RF exposure to occupational
workers was evaluated. As described previously, the maximum predicted off-axis, “near field”
power density is 0.197 mW/cm², or 3.94% of the controlled limit. As the operator will generally be
posted at locations either behind the parabolic reflector or in the truck itself, it is anticipated that
actual exposure will be substantially less than the above “worst case” prediction.



        With respect to worker safety, it is believed that based on the preceding analysis, excessive
exposure would not occur provided that adequate physical separation is established. As mentioned
previously, detailed operator policy will be employed protecting workers from excessive exposure
when work must be performed where high RF levels may be present. Such protective measures may
include, but will not be limited to, restriction of access to areas where levels in excess of the
guidelines may be expected, or the complete shutdown of facilities when work or inspections must
be performed in areas where the exposure guidelines would otherwise be exceeded. On-site RF
exposure measurements may also be undertaken to establish the bounds of safe working areas. The
applicant will coordinate exposure procedures with all pertinent facilities.



Conclusion

        As demonstrated herein, excessive levels of RF energy will not be caused at publicly
accessible areas by strictly following the policy detailed herein. Consequently, neither members of
the general public nor occupational staff will be exposed to RF levels in excess of the Commission’s
guidelines. Access to the vicinity of the uplink antenna will be restricted and controlled through the
use of crowd control stanchions, cones, and conspicuous RFR warning signs as part of an overall RF
safety program. The above study presumes that the subject antenna is the sole source of RF energy
at the uplink site. In the case of multiple emitters, further analysis or measurement is necessary to
assure compliance.



                                      Cavell, Mertz & Davis, Inc.


                                      Engineering Statement
                                             (page 5 of 5)


Certification

       The undersigned hereby certifies that the foregoing statement was prepared by him or under
his direction, and that it is true and correct to the best of his knowledge and belief. Mr. Clinton is
a staff engineer in the firm of Cavell, Mertz & Davis, Inc.




                                                             Robert J. Clinton
                                                             September 9, 2005

Cavell, Mertz & Davis, Inc.
7839 Ashton Avenue
Manassas, VA 20109
(703) 392-9090




                                      Cavell, Mertz & Davis, Inc.



Document Created: 2005-09-09 11:54:09
Document Modified: 2005-09-09 11:54:09

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