RF Study DIR-2018-02.pdfAPPLE INC. AT&T Site No. CCL04410
10335 North Tantau Avenue Sprint Site No. SF96xc031
Cupertino, California T-Mobile Site No. SF14981A
Proposed Base Stations Verizon Site No. 431599
J8ZJ
Page 1 of 5
Statement of Hammett & Edison, Inc., Consulting Engineers
The firm of Hammett & Edison, Inc., Consulting Engineers, has been retained on behalf of Apple Inc.,
to evaluate the base stations for personal wireless telecommunications carriers AT&T Mobility,
Sprint, T-Mobile, and Verizon Wireless (Site Nos. CCL04410, SF96cx031, SF14981A, and
431599 “Highway 280 Tantau,” respectively) proposed to be located on the Apple office building
(TA09) at 10335 North Tantau Avenue in Cupertino, California, for compliance with appropriate
guidelines limiting human exposure to radio frequency (“RF”) electromagnetic fields.
Executive Summary
Four wireless carriers propose to install directional panel antennas behind the existing view
screen wall above the roof of the four-story Apple office building located at 10335 North
Tantau Avenue in Cupertino. The proposed operations will comply with the FCC guidelines
limiting public exposure to RF energy; certain mitigation measures are recommended to
comply with FCC occupational guidelines.
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 GHz 5.00 mW/cm2 1.00 mW/cm2
WiFi (and unlicensed uses) 2–6 5.00 1.00
BRS (Broadband Radio) 2,600 MHz 5.00 1.00
WCS (Wireless Communication) 2,300 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 2.40 0.48
[most restrictive frequency range] 30–300 1.00 0.20
APPLE INC. AT&T Site No. CCL04410
10335 North Tantau Avenue Sprint Site No. SF96xc031
Cupertino, California T-Mobile Site No. SF14981A
Proposed Base Stations Verizon Site No. 431599
J8ZJ
Page 2 of 5
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. 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.
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 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 Apple, including architectural drawings by Hammel, Green and
Abrahamson, Inc., dated “10/XX/17,” AT&T Mobility, Sprint, T-Mobile, and Verizon Wireless
propose to install base stations behind the existing view screen wall above the roof of the four-story
office building located at 10335 North Tantau Avenue in Cupertino. The antennas would be mounted
at an effective height of about 64 feet above ground, 11½ feet above the roof. The following
information has been provided by the individual carriers:
APPLE INC. AT&T Site No. CCL04410
10335 North Tantau Avenue Sprint Site No. SF96xc031
Cupertino, California T-Mobile Site No. SF14981A
Proposed Base Stations Verizon Site No. 431599
J8ZJ
Page 3 of 5
AT&T
• Zoning drawings by J5 Infrastructure Partners, dated October 13, 2017
• Four CCI Model TPA-65R-BU4A antennas in pairs and four CCI Model HPA-33R-BUU-H4,
employing up to 4° downtilt
• Oriented in pairs toward 40°T and 225°T, and in a group of four toward 300°T
• Maximum effective radiated power 21,760 watts: 4,540 watts at WCS, 6,060 watts at AWS,
5,560 watts at PCS, 2,960 watts at cellular, 2,640 watts at 700 MHz
Sprint
• Zoning drawings by Fullerton Engineering Design, dated October 18, 2017
• Four RFS Model APXVFRR12X-C and four RFS Model AW3378 antennas, employing up to
2° downtilt
• Oriented in identical pairs toward 0°T, 110ºT, 260°T, and 300°T
• Maximum effective radiated power 8,790 watts: 6,140 watts at BRS, 2,170 watts at PCS,
480 watts at SMR
T-Mobile
• Zoning drawings by Black & Veatch, dated October 16, 2017
• Three Ericsson Model AIR32-KRD901146, three RFS Model APXVF13-C-A20, and three
RFS Model APX16DWV antennas, employing up to 2° downtilt
• Oriented in identical groups of three toward 30°T, 160°T, and 280°T
• Maximum effective radiated power 10,100 watts: 4,400 watts at AWS, 4,400 watts at PCS,
1,300 watts at 700 MHz
Verizon
• Zoning drawings by Streamline Engineering and Design, Inc., dated September 28, 2017
• Twelve Amphenol Model HEX454CW0000G antennas, employing no downtilt
• Oriented in groups of three toward 0°T, 90°T, 180°T, and 270°T
• Maximum effective radiated power 18,640 watts: 9,640 watts at AWS, 4,320 watts at PCS,
2,600 watts at cellular, 2,080 watts at 700 MHz
APPLE INC. AT&T Site No. CCL04410
10335 North Tantau Avenue Sprint Site No. SF96xc031
Cupertino, California T-Mobile Site No. SF14981A
Proposed Base Stations Verizon Site No. 431599
J8ZJ
Page 4 of 5
Study Results
For a person anywhere at ground, the maximum RF exposure level due to the cumulative operation of
all four carriers is calculated to be 0.061 mW/cm2, which is 6.6% of the applicable public exposure
limit. The maximum calculated level on the top floor of the building is 1.8% of the public exposure
limit; this occurs in only one area, with typical levels elsewhere on that floor less than 1%. The
maximum calculated level at the underground garage is less than 0.1% of the public exposure limit.
The maximum calculated level at the second-floor elevation of any nearby residence* is 1.9% 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 from the proposed operation.
Levels on the roof of the building may exceed the applicable public limit, as shown in Figure 3.
Recommended Mitigation Measures
Due to their mounting locations and height, requiring passage through a locked door to reach the roof,
the carriers’ antennas would not be accessible to unauthorized persons, 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, it is recommended that appropriate RF safety training, to include
review of personal monitor use and lockout/tagout procedures, be provided to all authorized personnel
who have access to the structure, including employees and contractors of the respective carriers and of
the property owner. No access directly in front of the antennas themselves, such as might occur
during certain maintenance activities above the roof outside the screen wall, should be allowed while
the base station is in operation, unless other measures can be demonstrated to ensure that occupational
protection requirements are met. It is recommended that explanatory signs† be posted at the access
doors in the view screen and on the view screen wall in front of the antennas, readily visible from any
angle of approach to persons who might need to work within that distance.
* Located at least 480 feet away, based on photographs from Google Maps.
† 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 be required.
APPLE INC. AT&T Site No. CCL04410
10335 North Tantau Avenue Sprint Site No. SF96xc031
Cupertino, California T-Mobile Site No. SF14981A
Proposed Base Stations Verizon Site No. 431599
J8ZJ
Page 5 of 5
Conclusion
Based on the information and analysis above, it is the undersigned’s professional opinion that
operation of the proposed base stations at 10335 North Tantau Avenue 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. Training authorized personnel and posting
explanatory signs are recommended to establish compliance with occupational exposure limits.
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, 2019. 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.
_________________________________
William F. Hammett, P.E.
707/996-5200
December 7, 2017
FCC Radio Frequency Protection Guide
FCC Guidelines
Figure 1
Frequency (MHz)
1000
100
10
1
0.1
0.1 1 10 100
103 104 105
Occupational Exposure
Public Exposure
PCS
CellFM
PowerDensity(mW/cm2)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 Electromagnetic Fields (f is frequency of emission in MHz)
Applicable
Range
(MHz)
Electric
Field Strength
(V/m)
Magnetic
Field Strength
(A/m)
Equivalent Far-Field
Power Density
(mW/cm2)
0.3 – 1.34 614 614 1.63 1.63 100 100
1.34 – 3.0 614 823.8/ f 1.63 2.19/ f 100 180/ f2
3.0 – 30 1842/ f 823.8/ f 4.89/ f 2.19/ f 900/ f2 180/ f2
30 – 300 61.4 27.5 0.163 0.0729 1.0 0.2
300 – 1,500 3.54 f 1.59 f f /106 f /238 f/300 f/1500
1,500 – 100,000 137 61.4 0.364 0.163 5.0 1.0
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.
RFR.CALC ™ Calculation Methodology
Assessment by Calculation of Compliance with FCC Exposure Guidelines
Methodology
Figure 2
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
BW
0.1 Pnet
D 2 h , in mW /cm 2,
and for an aperture antenna, maximum power density Smax = 0.1 16 Pnet
h 2 , in mW /cm 2,
where BW = 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:
power density S = 2.56 1.64 100 RFF 2 ERP
4 D2 , in mW /cm 2,
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.
APPLE INC.
10335 North Tantau Avenue
Cupertino, California
Proposed Base Stations
J8ZJ
Figure 3
Recommended Mitigation Measures
AT&T Site No. CCL04410
Sprint Site No. SF96xc031
T-Mobile Site No. SF14981A
Verizon Site No. 431599
Calculated RF Exposure Levels on Roof
FEET
50 0 50 100
Calculations performed according to OET Bulletin No. 65, August 1997.
Colors shown represent percent of applicable FCC public limit.
[blank] <100%>100%>500%
FEET
50 0 50 100
Calculations performed according to OET Bulletin No. 65, August 1997.
Colors shown represent percent of applicable FCC public limit.
[blank] <100%>100%>500%
Notes: See text. Base drawing from Fullerton
Engineering Design, dated October 18, 2017.
Calculations performed according to OET Bulletin
65, August 1997.
Shaded color
Boundary marking
Sign type
Legend:Exceeds
Occupational
- Yellow
CAUTION
N/A
blank
Less Than
Public
- Green
INFORMATION
Exceeds 10x
Occupational
- Orange
WARNING
Exceeds
Public
- Blue
NOTICE
• Post explanatory signs
• Provide training Northouter roof
access door
AT&T antennas
Sprint antennas
T-Mobile antennas
Verizon antennas
outer roof
access door