107-F. T-Mobile RF Energy Study.pdfATTACHMENT F
T-Mobile West Corp. • Proposed Base Station (Site No. SF24189D)
11371 Bubb Road - Cupertino, California
Statement of Hammett & Edison, Inc., Consulting Engineers
The firm of Hammett & Edison, Inc., Consulting Engineers, has been retained on behalf of T-Mobile
West Corp., a personal wireless telecommunications carrier, to evaluate the base station (Site No.
SF24189D) proposed to be located at 11371 Bubb Road in Cupertino, California, for compliance with .
appropriate guidelines limiting human exposure to radio frequency ("RF") electromagnetic fields.
Prevailing Exposure Standards
The U.S, Congress requires that the Federal Communications Commission ("FCC") evaluate its
actions for possible significant impact on the environment. A summary of the FCC's exposure limits
is shown in Figure 1. These limits apply for continuous exposures and are intended to provide a
prudent margin of safety for all persons, regardless of age, gender, size, or health. The most restrictive
FCC limit for exposures of unlimited duration to radio frequency energy for several wireless services
are as follows:
Wireless Service Frequency Band Occupational Limit Public Limit
Microwave (Point -to -Point) 5-80,000 MHz 5.00 mWlcm2 1.00 mWlcm2
BRS (Broadband Radio) 2,600 5.00 1.00
AWS (Advanced Wireless) 2,100 5.00 1.00
PCS (Personal Communication) 1,950 5.00 1.00
Cellular 870 2.90 0.58
SMR (Specialized Mobile Radio) 855 2.85 0.57
700 MHz .700 2.35 0.47
[most restrictive frequency range] 30-300 1.00 0.20
Power line frequencies (60 Hz) are well below the applicable range of these standards, and there is
considered to be no compounding effect from simultaneous exposure to power line and radio
frequency fields.
General Facility Requirements
Base stations typically consist of two distinct parts: the electronic transceivers (also called "radios" or
"channels") that are connected to the traditional wired telephone lines, and the passive antennas that
send the wireless signals created by the radios out to be received by individual subscriber units.
The transceivers are often located at ground level and are connected to the antennas by coaxial cables.
A small antenna for reception of GPS signals is also required, mounted with a clear view of the sky.
Because of the short wavelength of the frequencies assigned by the FCC for wireless services, the
antennas require line -of -sight paths for their signals to propagate well and so are installed at some
height above ground. The antennas are designed to concentrate their energy toward the horizon, with
very little energy wasted toward the sky or the ground. Along with the low power of such facilities,
this means that it is generally not possible for exposure conditions to approach the maximum
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HAMNMTT & EDIsom INC.
co:�' iMNIGENCINEERS TM24189XS96
SAN rkaancECO Page 1 of 3
T-Mobile West Corp. - Proposed Base Station (Site No. SF24189D)
11371 Bubb Road • Cupertino, California
Computer Modeling Method
The FCC provides direction for determining compliance in, its Office of Engineering and Technology
Bulletin No. 65, "Evaluating Compliance with FCC -Specified Guidelines for Human Exposure to
Radio Frequency Radiation," dated August 1997. Figure 2 attached describes the calculation
methodologies, reflecting the facts that a directional antenna's radiation pattern is not fully formed at
locations very close by (the "near -field" effect) and that at greater distances the power level from an
energy source decreases with the square of the distance from it (the "inverse square law"). The
conservative nature of this method for evaluating exposure conditions has been verified by numerous
field tests.
Site Description
Based upon information provided by T-Mobile, including construction drawings by Michael Wilk
Architecture, dated July 2, 2010, it is proposed to mount three RFS Model APXV18-206513-C
directional panel antennas on an existing 60'/2-foot utility pole sited in the public right-of-way located
near 11371 Bubb Road in Cupertino. The antennas would be mounted with up to 20 downtilt at an
effective height of about 44'/2 feet above ground and would be oriented toward 07, 1207, and 240°T,
to provide service in all directions. The maximum effective radiated power in any direction would be
360 watts, representing simultaneous operation at 180 watts each for AWS and for PCS. There are
reported no other wireless telecommunications base stations nearby.
Study Results
For a person anywhere at ground, the maximum RF exposure level due to the proposed T-Mobile
operation is calculated to be 0.0012 mW/cmZ, which is 0.12% of the applicable public exposure limit.
The maximum calculated level at the second -floor elevation of any nearby residence* is 0.22% of the
public exposure limit. It should be noted that these results include several `worst -case" assumptions
and therefore are expected to overstate actual power density Ievels from the proposed operation.
Recommended Mitigation Measures
Due to their mounting locations, the T-Mobile antennas would not be accessible to the general public,
and so no mitigation measures are necessary to comply with the FCC public exposure guidelines. To
prevent occupational exposures in excess of the FCC guidelines, no access within 2 feet directly in
front of the antennas themselves, such as might occur during maintenance work on the pole, should be
allowed while the base station is in operation, unless other measures can be demonstrated to ensure
that occupational protection requirements are met.
HA UVMTT & EDISON, INC.
C0T\SUL:r]NG ENGMEAt'; TM24189X596
SAN FRANCISCO Page 2 of 3
T-Mobile Vilest Corp. • Proposed Base Station (Site No. SF24189D)
11371 Bubb Road • Cupertino, California
Posting explanatory warning signst at the antennas and/or on the pole below the antennas, such that
the-- signs would be readily visible from any angle of approach to persons who might need to work
within that distance, would be sufficient to meet FCC -adopted guidelines.
Conclusion
Based on the information and analysis above, it is the undersigned's professional opinion that the
operation of the base station proposed by T-Mobile West Corp. at 11371 Bubb Road in Cupertino,
California, will comply with the prevailing standards for limiting public exposure to radio frequency
energy and, therefore, will not for this reason cause a significant impact on the environment. The
highest calculated level in publicly accessible areas is much less than the prevailing standards allow
for exposures of unlimited duration. This finding i.s consistent with measurements of actual exposure
conditions taken at other operating base stations. Posting of explanatory signs is recommended to
establish compliance with occupational exposure limitations.
Authorship
The undersigned author of this statement is a qualified Professional Engineer, holding California
Registration No. E-18063, which expires on June 30, 2011. This work has been carried out under his
direction, and all statements are true and correct of his own knowledge except, where noted, when data
has been supplied by others, which data he believes to be correct.
July 28, 2010
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707/996-5200
# Warning signs should comply with OET-65 color; symbol, and content recommendations. Contact information
should be provided (e.g., a telephone number) to arrange for access to restricted areas. The selection of language(s)
is not an engineering matter, and guidance from the landlord, local zoning or health authority, or appropriate
professionals may e required. Signage may also need to comply with the requirements of PUC 0095.
HAMMETT & EDISON, INC
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Page 3 of 3
FCC Radio Frequency Protection Guide
The U.S. Congress required (1996 Telecom Act) the Federal Communications Commission ("FCC")
to adopt a nationwide human exposure standard to ensure that its licensees do not, cumulatively, have
a significant impact on the environment. The FCC adopted the limits from Report No. 86, `Biological
Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields," published in 1986 by the
Congressionally chartered National Council on Radiation Protection and Measurements ("NCRP").
Separate limits apply for occupational and public exposure conditions, with the latter limits generally
five times more restrictive. The more recent standard, developed by the Institute of Electrical and
Electronics Engineers and approved as American National Standard ANSI/IEEE C95.1-2006, "Safety
Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to
300 GHz," includes similar limits. These limits apply for continuous exposures from all sources and
are intended to provide a prudent margin of safety for all persons, regardless of age, gender, size, or
health.
As shown in the table and chart below, separate limits apply for occupational and public exposure
conditions, with the latter limits (in italics and/or dashed) up to five times more restrictive:
_ Frequency
Applicable
Range
(MHz)
0.3 - I.34
1.34 - 3.0
3.0 - 30
30- 300
300- 1,500
1,500- 100,000
Electromagnetic Fields f is frequencyfrequengy
of emission in MHz
Electric
Magnetic
Equivalent Far -Field
Field Strength
Field Strength
Power Density
(V/rn)
(Alm)
(mw/cm2)
6I4 614
1.63 1.63
100 100
614 823,81f
1.63 2.191f
100 - 18011
1842/ f 823.8/f
4.89/ f 2.191f
900/ f 1801
61.4 27.5
O.163 0.0729
1.0 0.2
3.54* 1.594f
-Tf/106 Vf1238
ff300 f11500
137 61.4
0.364 0.163
5.0 1.0
Occupational Exposure
` PCS
� FM Cell
Public Exposure
0.1 1 .10 100 103 104 105
Frequency (MHz)
Higher levels are allowed for short periods of time, such that total exposure levels averaged over six or
thirty minutes, for occupational or public settings, respectively, do not exceed the limits, and higher
levels also are allowed for exposures to small areas, such that the spatially averaged levels do not
exceed the limits. However, neither of these allowances is incorporated in the conservative calculation
formulas in the FCC Office of Engineering and Technology Bulletin No. 65 (August 1997) for
projecting field levels. Hammett & Edison has built those formulas into a proprietary program that
calculates, at each location on an arbitrary rectangular grid, the total expected power density from any
number of individual radio sources. The program allows for the description of buildings and uneven
, ccura a projections.
1114" PU - . T8 Hwm= & EDISON, INC.
CDNSULnNGRNGUgEFM FCC Guidelines
SAN FRANCISCO
Figure 1
RFR.CALCTm Calculation Methodology
Assessment by Calculation of Compliance with FCC Exposure Guidelines
The U.S. Congress required (1996 Telecom Act) the Federal Communications Commission ("FCC") to
adopt a nationwide human exposure standard to ensure that its licensees do not, cumulatively, have a
significant impact on the environment. The maximum permissible exposure limits adopted by the FCC
(see Figure 1) apply for continuous exposures from all sources and are intended to provide a prudent
margin of safety for all persons, regardless of age, gender, size, or health. Higher levels are allowed for
short periods of time, such that total exposure levels averaged over six or thirty minutes, for
occupational or public settings, respectively; do not exceed the limits.
Near Field.
Prediction methods have been developed for the near field zone of panel (directional) and whip
(omnidirectional) antennas, typical at wireless telecommunications base stations, as well as dish
(aperture) antennas, typically used for microwave links. The antenna patterns are not fully formed in
the near field at these antennas, and the FCC Office of Engineering and Technology Bulletin No. 65
(August 1997) gives suitable formulas for calculating power density within such zones.
For a panel or whip antenna, power density S = 180 x 0.1 x Pre'
in mW/cm 2
BBw Tc x D x h ' ,
and for an aperture antenna, maximum power density Smax = 0.1 x 16x 77 hZ x PneC � in mW/CM2,
where 6Bw = half -power beamwidth of the antenna, in degrees, and
Pnet = net power input to the antenna, in watts,
D = distance from antenna, in meters,
h = aperture height of the antenna, in meters, and
rl = aperture efficiency (unitless, typically 0.5-0.8).
The factor of 0.1 in the numerators converts to the desired units of power density.
Far Field.
OET-65 gives this formula for calculating power density in the far field of an individual RF source:
power density S = 2.56 x 1.64 x 100 x RFFZ x ERP mW 2
in Icm ,
4xacxD2
where ERP = total ERP (all polarizations), in kilowatts,
RFF = relative field factor at the direction to the actual point of calculation, and
D = distance from the center of radiation to the point of calculation, in meters.
The factor of 2.56 accounts for the increase in power density due to ground reflection, assuming a
reflection coefficient of 1.6 (1.6 x 1.6 = 2.56). The factor of 1.64 is the gain of a half -wave dipole
relative to an isotropic radiator. The factor of 100 in the numerator converts to the desired units of
power density. This formula has been built into a proprietary program that calculates, at each Iocation
on an arbitrary rectangular grid, the total expected power density from any number of individual
radiation sources. The program also allows for the description of uneven terrain in the vicinity, to
obtain more accurate projections.
HAMMETT & EDISON, INC.
CONSULTING ENGW EEIZS Methodology
e#hodology
Figure 2