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AT&T Mobility Base Station No. CCL01039 RF ReportAT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG W1KY Page 1 of 5 ©2021 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 proposed modifications to its existing base station (Site No. CCL01039) located at One Infinite Loop in Cupertino, California, for compliance with appropriate guidelines limiting human exposure to radio frequency (“RF”) electromagnetic fields. Executive Summary AT&T proposes to replace some of its directional panel antennas above the four-story office building located at One Infinite Loop in Cupertino. The proposed operation will, together with the existing base stations at the site, comply with the FCC guidelines limiting public exposure to RF energy; certain mitigation measures are recommended to comply with FCC occupational guidelines. Prevailing Exposure Standard 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 limit for exposures of unlimited duration at several wireless service bands are as follows: Transmit “Uncontrolled” Occupational Limit Wireless Service Band Frequency Public Limit (5 times Public) Microwave (point-to-point) 1–80 GHz 1.0 mW/cm2 5.0 mW/cm2 Millimeter-wave 24–47 1.0 5.0 Part 15 (WiFi & other unlicensed) 2–6 1.0 5.0 C-Band 3,700 MHz 1.0 5.0 CBRS (Citizens Broadband Radio) 3,550 1.0 5.0 BRS (Broadband Radio) 2,490 1.0 5.0 WCS (Wireless Communication) 2,305 1.0 5.0 AWS (Advanced Wireless) 2,110 1.0 5.0 PCS (Personal Communication) 1,930 1.0 5.0 Cellular 869 0.58 2.9 SMR (Specialized Mobile Radio) 854 0.57 2.85 700 MHz 716 0.48 2.4 600 MHz 617 0.41 2.05 [most restrictive frequency range] 30–300 0.20 1.0 AT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG W1KY Page 2 of 5 ©2021 General Facility Requirements Base stations typically consist of two distinct parts: the electronic transceivers (also called “radios”) 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. 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”). This methodology is an industry standard for evaluating RF exposure conditions and has been demonstrated through numerous field tests to be a conservative prediction of exposure levels. Site and Facility Description Based upon information provided by AT&T, including construction drawings by J5 Infrastructure Partners, dated September 24, 2021, that carrier presently has twelve directional panel antennas installed on short poles above the roof of the four-story office building located at One Infinite Loop in Cupertino. It is proposed to replace six of those antennas with six directional panel antennas – three Ericsson Model AIR6449, two CommScope Model NNH4-65A-R6H4, and one CommScope Model NNHH-65A-R4-V2 – at the same locations, next to the remaining six CommScope Model NNHH-65A-R4 antennas. The CommScope antennas would employ up to 16° downtilt and the Ericsson antennas would employ up to 19° downtilt. The antennas would be mounted at an effective height of about 64 feet above ground, 7½ feet above the roof, and would be oriented in three groups of four (each with one of the Ericsson antennas) toward 20°T, 140°T, and 260°T, to provide service in all directions. The maximum effective radiated power in any direction would be 124,310 watts, representing simultaneous operation AT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG W1KY Page 3 of 5 ©2021 at 101,200 watts for C-Band,* 3,600 watts for WCS, 7,740 watts for AWS, 5,070 watts for PCS, 1,090 watts for cellular, and 5,610 watts for 700 MHz service. Presently located on the roof of the adjacent building to the north are similar antennas for use by T-Mobile and Verizon Wireless. For the limited purpose of this study, the transmitting facilities of those carriers are assumed to be as follows: Operator Service Maximum ERP Antenna Model Downtilt Height T-Mobile AWS 4,400 watts Ericsson AIR21 2° 63 ft PCS 4,400 Ericsson AIR21 2 63 700 MHz 3,300 RFS APXVARR24 2 63 600 MHz 3,300 RFS APXVARR24 2 63 Verizon AWS 11,800 CommScope NHH-65B 2 65 PCS 5,300 CommScope NHH-65B 2 65 Cellular 2,800 CommScope NHH-65B 2 65 700 MHz 2,800 CommScope NHH-65B 2 65 Study Results For a person anywhere at ground, the maximum RF exposure level due to the proposed AT&T operation is calculated to be 0.15 mW/cm2, which is 18% of the applicable public exposure limit. The maximum calculated cumulative level at ground, for the simultaneous operation of all three carriers, is 23% of the public exposure limit. The maximum calculated cumulative level at any other nearby building † off the Apple campus is 11% of the public limit. The maximum calculated cumulative level at the second-floor elevation of any nearby residence‡ is 4.8% 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. Levels are calculated to exceed the applicable exposure limits on the roof of the subject building, on the roof of the adjacent building to the north, and on the architectural arch to the south, as shown in Figure 3. * The manufacturer reports that the antenna transmits 75% of the time in this band; this factor is incorporated into the calculations. Also included is a statistical factor reducing the power to 32% of maximum to account for spatial distribution of served users, as recommended by AT&T (based on the United Nations International Telecommunication Union ITU-T Series K, Supplement 16, dated May 20, 2019); this factor is subject to confirmation by measurements, which are recommended. † Located at least 400 feet away, based on photographs from Google Maps. ‡ Located at least 650 feet away, based on photographs from Google Maps. AT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG W1KY Page 4 of 5 ©2021 Recommended Mitigation Measures It is recommended that the nearest roof access hatches be kept locked, so that the AT&T antennas are not accessible to unauthorized persons. 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 AT&T and of the property owner. It is recommended that boundary lines be marked on the roof with blue and yellow paint to identify areas within which exposure levels are calculated to exceed the public and occupational FCC limits, respectively, as shown in Figure 3. No work in the yellow-shaded areas, such as might occur during certain maintenance activities, should be allowed while the pertinent antenna group 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 roof access hatches, at the boundary markings, and at the antennas, readily visible from any angle of approach to persons who might need to work within that distance. Similar measures should already be in place for the other carriers; applicable mitigations for those carriers have not been determined as part of this study. Conclusion Based on the information and analysis above, it is the undersigned’s professional opinion that the proposed operation of the AT&T Mobility base station located at One Infinite Loop in Cupertino, California, can comply with the prevailing standards for limiting human exposure to radio frequency energy and, therefore, need 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. Locking the roof access hatches is recommended to establish compliance with public exposure limits; training authorized personnel, marking roof areas, and posting explanatory signs are recommended to establish compliance with occupational exposure limits. § 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. AT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG W1KY Page 5 of 5 ©2021 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, 2023. 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 November 17, 2021 FCC Radio Frequency Protection Guide FCC Guidelines Figure 1 1000 100 10 1 0.1 0.1 1 10 100 103 104 105 Occupational Exposure Public Exposure PCS CellFM Po w e r De n s i t y (m W / c m 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 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 Frequency (MHz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© RFE.CALCTM Calculation Methodology Assessment by Calculation of Compliance with FCC Exposure Guidelines Calculation Methodology Figure 2 ©2021 180  θ BW × 0.1 × Pnet π × D × h 0.1 x 16 x n x P x h2 0.1 × 16 × η × Pnet π × h 2 net BW 180 0.1 x Pnetx θ 180  θ BW × 0.1 × Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180  θ BW × 0.1 × Pnet π × D × hS = qBW Hammett & Edison has incorporated the FCC Office of Engineering and Technology Bulletin No. 65 (“OET-65”) formulas (see Figure 1) in a computer program that calculates, at millions of locations on a grid, the total expected power density from any number of individual radio frequency sources. The program uses the specific antenna patterns from the manufacturers and allows for the inclusion of uneven terrain in the vicinity, as well as any number of nearby buildings of varying heights, to obtain accurate projections of RF exposure levels. The program can account for spatial-averaging when antenna patterns are sufficiently narrow, and time- averaging is typically considered when operation is in single-frequency bands, which require time-sharing between the base station and the subscriber devices. OET-65 provides this formula for calculating power density in the far-field from an individual RF source: in mW/cm2 power density where ERP = total Effective Radiated Power (all polarizations), in kilowatts, RFF = three-dimensional relative field factor toward point of calculation, and D = distance from antenna effective height to point of calculation, in meters. The factor of 2.56 accounts for the increase in power density due to reflections, assuming a reflection coefficient of 1.6 (1.6 x 1.6 = 2.56). This factor is typically used for all sources unless specific information from FCC filings by the manufacturer indicate that a different reflection coefficient would apply. 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. Because antennas are not true “point sources,” their signal patterns may not be fully formed at close distances and so exposure levels may be lower than otherwise calculated by the formula above. OET-65 recommends the cylindrical model formula below to account for this “near-field effect”: in mW/cm2 power density S = where Pnet = net power input to antenna, in watts, = half-power beamwidth of antenna, in degrees, D = distance from antenna effective height to point of calculation, in meters, and h = aperture height of antenna, in meters. The factor of 0.1 in the numerator converts to the desired units of power density. OET-65 confirms that the “crossover” point between the near- and far-field regions is best determined by finding where the calculations coincide from the two different formulas, and the program uses both formulas to calculate power density. 180  θ BW × 0.1 × Pnet π × D × h 0.1 x 16 x n x P x h2 0.1 × 16 × η × Pnet π × h 2 net BW 180 0.1 x Pnetx θ 180  θ BW × 0.1 × Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180  θ BW × 0.1 × Pnet π × D × hS = qBW 180  θ BW × 0.1 × Pnet π × D × h 0.1 x 16 x n x P x h2 0.1 × 16 × η × Pnet π × h 2 net BW 180 0.1 x Pnetx0 180  θ BW × 0.1 × Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180  θ BW × 0.1 × Pnet π × D × hS = AT&T Mobility • Base Station No. CCL01039 One Infinite Loop • Cupertino, California FA No. 10093972, USID No. 16720, PA No. 3701A0YHEG Calculated RF Exposure Levels on Roof W1KY Figure 3 Recommended Mitigation Measures 2021c • Lock nearest roof access hatches • Mark roof areas as shown • Post explanatory signs • Provide training Notes: See text. Base image from Google Maps. 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 Exceeds 10x Occupational - Orange WARNING Exceeds Public - Blue NOTICE No r t h at roof access hatch AT&T antenna groups FEET 5050 1000 Verizon antennas T-Mobile antennas raised arch roof access hatch on adjacent building Additional antennas on this building for use by T-Mobile and Verizon are not shown; their orientations avoid overlap of areas exceeding FCC limits. lower roof N/A