115-N. AT&T Mobility Proposed Base Station (Site No. CN3242A/Results Way, Cupertino, California/Statement of Hammett & Edison, Inc., Consulting Engineers, dated 10/26/10.pdfATTACHMENT N
AT&T Mobility • Proposed Base Station (Site No. CN3242A)
Results Way • Cupertino, California
Statement of Hammett & Edison, Inc., Consulting Engineers
The firm of Hammett & Edison, Inc., Consulting Engineers, has been retained on behalf of
AT&T Mobility, a personal wireless telecommunications carrier, to evaluate the base station (Site No.
CN3242A) proposed to be located at Results Way 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 personal wireless
services are as follows:
Wireless Service
Frequency Band
Occupational Limit
Public Limit
Microwave (Point -to -Point)
5-80,000 MHz
5.00 mW/cm2
1.00 mW/cm2
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
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
permissible exposure limits without being physically very near the antennas.
HAMMETT & EDISON, INC.
a z AT3242596.3
5AN Px:1WNCO Page 1 of 3
AT&T Mobility • Proposed Base Station (Site No. CN3242A)
Results Way • 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 and Facility Description
Based upon information provided by AT&T, including zoning drawings by Jeffrey Rome &
Associates, Inc., dated September 30, 2010, it is proposed to install twelve Kathrein Model 800-10764
directional panel antennas on a new 67-foot steel pole, configured to resemble a pine tree, to be sited
near the western edge of the parking lot located at Results Way in Cupertino. The antennas would be
mounted in stacked groups of four at effective heights of about 58 and 65 feet above ground and
would be oriented with up to 6° downtilt toward 20°T, 140°T, and 260°T, to provide service in all
directions. The maximum effective radiated power in any direction would be 3,090 watts,
representing simultaneous operation at 2,150 watts for PCs and 940 watts for cellular.
Presently located at a different site, on the roof of a building about 130 feet to the northwest, are
similar antennas for use by Sprint Nextel. For the limited purpose of this study, the transmitting
facilities of that carrier is assumed to be as follows:
Operator Service Maximum ERP Antenna Model Downtilt Height
Sprint Nextel PCs 1,500 watts Andrew RR9017 none 34'/a ft
Study Results
For a person anywhere at ground, the maximum ambient RF exposure level due to the proposed
AT&T operation by itself is calculated to be 0.0034 mW/cm2, which is 0.49% of the applicable public
exposure limit. The maximum calculated cumulative level at ground, for the simultaneous operation
of both carriers, is 0,73% of the public exposure limit. The maximum calculated cumulative level at
any nearby building is 2.4% of the public limit. The maximum calculated cumulative level at the
second -floor elevation of any nearby residence* is 0.92% 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 levels.
* Located at least 245 feet away, based on photographs from Google Maps.
HAMMETT & EDISON, INC.
AT3242596.3
CONSULTING ENCIN ERS i
a BAN FRANCiSCO Page 2 of 3
AT&T Mobility s Proposed Base Station (Site No. CN3242A)
Results Way - Cupertino, California
No Recommended Mitigation Measures
Due to their mounting locations, the AT&T antennas would not be accessible to the general public,
and so no mitigation measures are necessary to comply with the FCC public exposure guidelines. It is
presumed that AT&T will, as an FCC licensee, take adequate steps to ensure that its employees or
contractors comply with FCC occupational exposure guidelines whenever work is required near the
antennas themselves.
Conclusion
Based on the information and analysis above, it is the undersigned's professional opinion that
operation of the base station proposed by AT&T Mobility at Results Way 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 is consistent with measurements of actual exposure
conditions taken at other operating base stations.
Authorship
The undersigned author of this statement is a qualified Professional Engineer, holding California
Registration Nos. E-13026 and M-20676, which expire 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.
October 27, 2010
4 t IIANtWTT & EDISON, INC. AT3242596.3
CONSULTING ENGINEERS
SAN FRANC1SM 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 ANSWEEE 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:
Frequengy
Applicable
Range
(MHz)
0.3 — 1.34
1.34— 3.0
3.0 — 30
30 — 300
300— 1,500
1,500 — 100,000
I1111111
N
100
10
0.1
Electromagnetic Fields (f is freauencv of emission in MHz
Electric
Magnetic
Equivalent Far -Field
Field Strength
Field Strength
Power Density
(v/m)
(Alm)
(mW/cm2)
614 614
1.63 1.63
100 100
614 823.8/f
1.63 2.191f
too 18011
1842/ f 823.8/f
4.89/ f 2.191 f
goo/ f, 18011
61.4 27.5
0.163 0.0729
1.0 0.2
3.54-1h 1.59ff
4f/106 -�rf1238
f/300 f/1500
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
terrain, if required to obtain more accurate projections.
HEHAMMETT & EDISON, INC.
Cor�su[ TEKG MG�FRS FCC Guidelines
SAN FRANaSCO 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 Pnet mW 2
B 7rxD xh' in lam'
sw
and for an aperture antenna, maximum power density Smax = 0.1 x �6X ri X P„e` , in mW/cm2,
where 0Bw = 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
= 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:
2.56x1.64x100xRFF2 xERP
power density s = in mW/cm2,
4xzxD2
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 location
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.
HEHAMMETT & EDISON, INC.
CQNSU MNc ENGINEERS Methodology
SAN FRANCISCO Figure 2