NIER Study Report
SITE NAME:
413839 SAN PEDRO VALLEY EAST CA
ATC Customer:
Dish
LOCATION:
Pacifica, California
COMPANY:
American Tower
Woburn, Massachusetts
March 17th, 2022
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 1
Contents
DISCLAIMER NOTICE ...............................................................................................................................2 INTRODUCTION..........................................................................................................................................3 SITE AND FACILITY CONSIDERATIONS...........................................................................................3 POWER DENSITY CALCULATIONS.....................................................................................................4 APPENDIX 1 SATELLITE PHOTO.......................................................................................................5 APPENDIX 2 FCC OET-65 MPE LIMIT STUDY..............................................................................6 APPENDIX 3 INFORMATION PERTAINING TO MPE STUDIES .............................................7 APPENDIX 4 MPE STANDARDS METHODOLOGY......................................................................9 RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 2
Disclaimer Notice
This work is based upon our best interpretation of available information.
However, these data and their interpretation are constantly changing.
Therefore, we do not warrant that any undertaking based on this report will be successful, or that others will not require further research or actions in support of this proposal or future undertaking. In the event of errors, our liability is strictly limited to replacement of this document with a corrected one. Liability for consequential damages is specifically disclaimed. Any use of this document constitutes an agreement to hold Tower Engineering Professionals and its employees harmless and indemnify it for all liability, claims, demands, and litigation expenses and attorney’s fees arising out of such use.
Work product documents released prior to account settlement remain the sole property of Tower Engineering Professionals and must be returned on demand. Underlying work notes and data relating to this document remain the property of Tower Engineering Professionals. This document shall not be reproduced in whole or part without permission of Tower Engineering Professionals. Any dispute hereunder shall be adjudicated in North Carolina. Any use or retention of this document constitutes acceptance of these terms, the entire work product, and all charges associated therewith.
COPYRIGHT © 2021 BY
TOWER ENGINEERING PROFESSIONALS
KINSTON, NORTH CAROLINA
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 3
NIER STUDY REPORT
413839 SAN PEDRO VALLEY EAST CA
Pacifica, CA
INTRODUCTION
Tower Engineering Professionals (TEP) of Raleigh, NC has been retained by American Tower (ATC) of Woburn, Massachusetts to evaluate the RF emissions of an existing tower at this location.
SITE AND FACILITY CONSIDERATIONS
Site 413839 SAN PEDRO VALLEY EAST CA is located at in Pacifica CA at coordinates 900 Yosemite Dr. The support structure is a 55’ stealth monopole.
The installation consists of six wireless antenna levels with radiation centers of 55’, 8’, 35’, 34’, 33’, & 19’ above ground level. All antennae will have a radiation center as described above. All data used in this study was provided by one or more of the following sources:
1. ATC furnished data
2. Compiled from carrier and manufacturer standard configurations
3. Empirical data collected by TEP
A satellite view of the study area is located in Appendix 1.
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 4
POWER DENSITY CALCULATIONS
Graphs of the power density at different distances from the transmitter, compared to FCC MPE general population and occupational limits, may be seen in Appendix
2. These limits are based upon the Information Relating to MPE Standards found in Appendix 3. Study methodology may be seen in Appendix 4, which describes the Non-Ionizing Radiation Prediction Models. This site IS in compliance with FCC OET-65 MPE limits.
Prepared By:
March 17th 2022 Adam Carlson MS, CBRS, CPI CBRE
Program Manager
Tower Engineering Professionals
Approved By:
Andrew T Haldane P.E.
Tower Engineering Professionals
License No. 77052
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 5
APPENDIX 1 Satellite Photo
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 6
APPENDIX 2 FCC OET-65 MPE Limit Study
Maximum Power Density (@80’): 0.8900mW/cm²
General Population MPE (@80’): 184.5603%
Occupational MPE (@80’): 32.8926%
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 7
APPENDIX 3 Information Pertaining to MPE Studies
In 1985, the FCC first adopted guidelines to be used for evaluating human exposure to RF emissions. The FCC revised and updated these guidelines on August 1, 1996, as a result of a rule-making proceeding initiated in 1993. The new guidelines incorporate limits for Maximum Permissible Exposure (MPE) in terms of electric and magnetic field strength and power density for transmitters operating at frequencies between 300 kHz and 100 GHz.
The FCC's MPE limits are based on exposure limits recommended by the National Council on Radiation Protection and Measurements (NCRP) and, over a wide range of frequencies, the exposure limits were developed by the Institute of Electrical and Electronics Engineers, Inc., (IEEE) and adopted by the American National Standards Institute (ANSI) to replace the 1982 ANSI guidelines. Limits for localized absorption are based on recommendations of both ANSI/IEEE and NCRP.
The FCC's limits, and the NCRP and ANSI/IEEE limits on which they are based, are derived from exposure criteria quantified in terms of specific absorption rate (SAR). The basis for these limits is a whole-body averaged SAR threshold level of 4 watts per kilogram (4 W/kg), as averaged over the entire mass of the body, above which expert organizations have determined that potentially hazardous exposures may occur. The MPE limits are derived by incorporating safety factors that lead, in some cases, to limits that are more conservative than the limits originally adopted by the FCC in 1985. Where more conservative limits exist, they do not arise from a fundamental change in the RF safety criteria for whole-body averaged SAR, but from a precautionary desire to protect subgroups of the general population who, potentially, may be more at risk.
The FCC exposure limits are also based on data showing that the human body absorbs RF energy at some frequencies more efficiently than at others. The most restrictive limits occur in the frequency range of 30-300 MHz where whole-body absorption of RF energy by human beings is most efficient. At other frequencies, whole-body absorption is less efficient, and consequently, the MPE limits are less restrictive.
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 8
MPE limits are defined in terms of power density (units of milliwatts per centimeter squared: mW/cm2), electric field strength (units of volts per meter:
V/m) and magnetic field strength (units of amperes per meter: A/m). The far-field of a transmitting antenna is where the electric field vector (E), the magnetic field vector (H), and the direction of propagation can be considered to be all mutually orthogonal ("plane-wave" conditions).
Occupational/controlled exposure limits apply to situations in which persons are exposed as a consequence of their employment and in which those persons who are exposed have been made fully aware of the potential for exposure and can exercise control over their exposure. Occupational/controlled exposure limits also apply where exposure is of a transient nature as a result of incidental passage through a location where exposure levels may be above general population/uncontrolled limits (see below), as long as the exposed person has been made fully aware of the potential for exposure and can exercise control over his or her exposure by leaving the area or by some other appropriate means.
General population/uncontrolled exposure limits apply to situations in which the general public may be exposed or in which persons who are exposed as a consequence of their employment may not be made fully aware of the potential for exposure or cannot exercise control over their exposure. Therefore, members of the general public would always be considered under this category when exposure is not employment-related, for example, in the case of a telecommunications tower that exposes persons in a nearby residential area.
Additional details can be found in FCC OET 65.
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 9
APPENDIX 4 MPE Standards Methodology
This study predicts RF field strength and power density levels that emanate from communications system antennae. It considers all transmitter power levels (less filter and line losses) delivered to each active transmitting antenna at the communications site. Calculations are performed to determine power density and MPE levels for each antenna as well as composite levels from all antennas.
The calculated levels are based on where a human (Observer) would be standing at various locations at the site. The point of interest where the MPE level is predicted is based on the height of the Observer.
Compliance with the FCC limits on RF emissions are determined by spatially averaging a person’s exposure over the projected area of an adult human body, that is approximately six-feet or two-meters, as defined in the ANSI/IEEE C95.1 standard. The MPE limits are specified as time-averaged exposure limits. This means that exposure is averaged over an identifiable time interval. It is 30 minutes for the general population/uncontrolled RF environment and 6 minutes for the occupational/controlled RF environment. However, in the case of the general public, time averaging should not be applied because the general public is typically not aware of RF exposure and they do not have control of their exposure time. Therefore, it should be assumed that any RF exposure to the general public will be continuous.
The FCC’s limits for exposure at different frequencies are shown in the following Tables.
Limits for Occupational/Controlled Exposure
Frequency
Range
(MHz)
Electric Field
Strength (E)
(V/m)
Magnetic
Field
Strength (H)
(A/m)
Power
Density (S)
(mW/cm2)
Averaging
Time |E|2,
|H|2 or S
(minutes)
0.3 - 3.0 614 1.63 100* 6
3.0 - 30 1842/f 4.89/f 900/F2 6
30 - 300 61.4 0.163 1.0 6
300 - 1500 -- -- f/300 6
1500 -
100,000
-- -- 5 6
f = frequency
* = Plane-wave equivalent power density
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 10
Occupational/controlled limits apply in situations in which persons are exposed as a consequence of their employment provided those persons are fully aware of the potential for exposure and can exercise control over their exposure. Limits for occupational/controlled exposure also apply in situations when an individual is transient through a location where occupational/controlled limits apply provided he or she is made aware of the potential for exposure.
f = frequency
* = Plane-wave equivalent power density
General population/uncontrolled exposures apply in situations in which the general public may be exposed or in which persons that are exposed as a consequence of their employment may not be fully aware of the potential for exposure or cannot exercise control over their exposure.
It is important to understand that these limits apply cumulatively to all sources of RF emissions affecting a given area. For example, if several different communications system antennas occupy a shared facility such as a tower or rooftop, then the total exposure from all systems at the facility must be within compliance of the FCC guidelines.
The field strength emanating from an antenna can be estimated based on the characteristics of an antenna radiating in free space. There are basically two field areas associated with a radiating antenna. When close to the antenna, the region is known as the Near Field. Within this region, the characteristics of the RF fields are very complex and the wave front is extremely curved. As you move further from the antenna, the wave front has less curvature and becomes planar. The wave front still has a curvature but it appears to occupy a flat plane in space (plane-wave radiation).
This region is known as the Far Field.
Limits for General Population/Uncontrolled Exposure
Frequency Range
(MHz)
Electric Field
Strength (E)
(V/m)
Magnetic Field
Strength (H)
(A/m)
Power Density
(S)
(mW/cm2)
Averaging Time
|E|2, |H|2 or S
(minutes)
0.3 - 1.34 614 1.63 100* 30
1.34 - 30 824/f 2.19/f 180/F2 30
30 -300 27.5 0.073 0.2 30
300 -1500 -- -- f/1500 30
1500 -100,000 -- -- 1.0 30
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 11
Two models are utilized to predict Near and Far field power densities. They are based on the formulae in FCC OET 65. As this study is concerned only with Near Field calculations, we will only describe the model used for this study. For additional details, refer to FCC OET Bulletin 65.
Cylindrical Model (Near Field Predictions)
Spatially averaged plane-wave equivalent power densities parallel to the antenna may be estimated by dividing the antenna input power by the surface area of an imaginary cylinder surrounding the length of the radiating antenna. While the actual power density will vary along the height of the antenna, the average value along its length will closely follow the relation given by the following equation:
Where:
S = Power Density
P = Total Power into antenna
R = Distance from the antenna
L = Antenna aperture length
For directional-type antennas, power densities can be estimated by dividing the input power by that portion of a cylindrical surface area corresponding to the angular beam width of the antenna. For example, for the case of a 120-degree azimuthal beam width, the surface area should correspond to 1/3 that of a full cylinder. This would increase the power density near the antenna by a factor of three over that for a purely omni-directional antenna. Mathematically, this can be represented by the following formula:
Where:
S = Power Density
θBW = Beam width of antenna in degrees (3 dB half-power point) P = Total Power into antenna
R = Distance from the antenna
L = Antenna aperture length
If the antenna is a 360-degree omni-directional antenna, this formula would be equivalent to the previous formula.
S = P ÷ 2πRL
S = (180 / θBW) P ÷ πRL
RF Design & Services |Tower Engineering Professionals, Inc. (www.tepgroup.net) 105 W Caswell Street | Kinston, NC 28501 12
Spherical Model (Far Field Predictions)
Spatially averaged plane-wave power densities in the Far Field of an antenna may be estimated by considering the additional factors of antenna gain and reflective waves that would contribute to exposure.
The radiation pattern of an antenna has developed in the Far Field region and the power gain needs to be considered in exposure predictions. Also, if the vertical radiation pattern of the antenna is considered, the exposure predictions would most likely be reduced significantly at ground level, resulting in a more realistic estimate of the actual exposure levels.
Additionally, to model a truly "worst case" prediction of exposure levels at or near a surface, such as at ground-level or on a rooftop, reflection off the surface of antenna radiation power can be assumed, resulting in a potential four-fold increase in power density.
These additional factors are considered and the Far Field prediction model is determined by the following equation:
Where:
S = Power Density
EIRP = Effective Radiated Power from antenna
Rc = Reflection Coefficient (2.56)
R = Distance from the antenna
The EIRP includes the antenna gain. If the antenna pattern is considered, the antenna gain is relative based on the horizontal and vertical pattern gain values at that particular location in space, on a rooftop or on the ground. However, it is recommended that the antenna radiation pattern characteristics not be considered to provide a conservative "worst case" prediction. This is the equation is utilized for the Far Field exposure predictions herein.
S = EIRP × Rc ÷ 4πR2