HomeMy WebLinkAboutCUP 01-24; Marja Acres PCS Facility; Conditional Use Permit (CUP) (7)Sprint PCS -NEPA RF Compliance
15200 Santa Fe Trail Drive, Lenexa, Kansas 66219 Office (913) 890-2519 Fax (913) 523-0436
Date: 9/12/03
To: City of Carlsbad, California
From: Dave Kirk
RE: FCC NEPA Compliance for Site SD25XC154
Site Address: 4901 El Camino Real, Carlsbad, California 92008
Site Description: Stealth Antennas (concealed in trunk of fake palm tree)
Site Owner: Jay Franklin Hoffman and Maryon Dooley Hoffman, Co-Trustees, T.T.D.
The purpose of this letter is to demonstrate compliance with FCC standards in regard to the
electromagnetic emissions from the antennas located in the fake palm tree at site SD25XC154
located at 4901 El Camino Real, Carlsbad, California.
The FCC, in regulating electromagnetic radiation, applies a modified version of the standards
developed by the American National Standards Institute (ANSI) and the Institute of Electrical and
Electronics Engineers (IEEE) to include the NCRP standard for Specific Absorption Rate or SAR, for
PCS bands. These standards, when converted over to the more familiar power density specification,
set a maximum power density level for public areas at 1.00mW/cm2 (milliwatts per square
centimeter) for general population exposure and 5.00mW/cm2 for occupational exposure. As a
measure of safety, this level is set 50 times lower than levels the standards committees felt could
potentially be harmful for constant exposure. PCS technology uses very low power transmitters
especially when compared with TV and Radio broadcasting which can be hundreds of thousands of
times more powerful than a PCS station.
Our antennas are designed to concentrate the majority of their signal power out of the front of the
antenna in a very thin beam. This installation consists of two three-sector directional antenna
configuration. Each sector has one transmit and receive antenna and one receive-only antenna.
Signal strength coming from the back of an antenna and from positions well below an antenna is
typically hundreds of times lower than the signal in the main beam at the front of the antenna.
Through software modeling techniques we can calculate the power density from a Sprint PCS
installation at a variety of locations around the proposed site.
The site in this instance is a OTHER antenna installation using a 65-degree beam width antenna.
Sprint PCS evaluates all sites, to determine the percent of exposure incurred by the general public
as well as occupational exposure resulting from the operation of our antennas. This is an issue we
take very seriously and much effort and manpower goes into maintaining NEPA compliant sites. In
addition to this, regular audits are conducted to ensure accuracy and completeness. We have
developed several proprietary software programs exclusively used to determine Power Density
levels and to compute Maximum Exposure limits. It is also our policy that when a site is changed in
any manner that would impact exposure levels, a new analysis is performed. All data is saved and
available to the FCC upon request.
The following contains information on the current FCC standards, the type of modeling Sprint PCS
uses to ensure compliance to the standards and the results of the study for this particular site.
Current FCC-adopted Exposure Limits
In FCC 96-326, the FCC adopted new exposure guidelines. The guidelines are given in terms of
mW/cm2 and the maximum limits are termed 'Maximum Permissible Exposure' (MPE) for both
occupational and general cases. Because these guidelines are based upon the same SAR limits as
those in the IEEEIANSI and NCRP guidelines, they also include the safety factors of 10 and 50 for
occupational and general public scenarios respectively.
The graph in Figure 1-1 shows the current FCC MPE guidelines. The two arrows indicate the cellular
( -850 MHz) and PCS ( -1900 MHz) frequencies. The exposure limits for PCS, expressed in terms of
more readily determined "power density", are 1.0 and 5.00mW/cm2 for general public and occupational
cases, respectively.
FCC Exposure Limits
~
\ " "' \. Cellular PCS
~
E u l E = E
\ v
:::;
I!! " .. 0 It
\ \ w
1 o\ ~ ' )()() poo
\
0
Frequency, MHz
Figure 1-1: FCC Exposure Limits.
Current FCC Rules/Regulations
The current regulations are contained in CFR Title 47, Sections 1.1307 and 1.1310.
A brief summary of the current regulation is as follows:
In general, all facilities, operations and transmitters regulated by the Commission must comply with
the exposure limits put forth in the NEPA rules of Title 47, Part 1, Section 1.1307 and 1.1310.
Applications to the Commission . . . must contain a statement confirming compliance with the limits
unless ... categorically excluded.
Technical information showing the basis for this statement must be submitted to the Commission
upon request.
In the case of multiple fixed transmitters, any action necessary to bring the facility into compliance is
the shared responsibility of all licensees whose transmitters contribute more than. 5% of the
exposure limit applicable to that transmitter.
Spherical Modeling
The concept of the spherical model is to assume that the EIRP of the actual antenna is being
applied to a point source (true isotropic radiator). This is really only valid in the center of the main
beam of the antenna but it guarantees a worst-case view everywhere else. The power density is
then calculated by dividing the EIRP by the surface area of the sphere (4nt), for the distance r away
from the antenna. In general, we will consider the shortest distance between the antenna and a six
(6) foot area above the roof or ground where a person might stand. Additionally, we must multiply
the EIRP by a power reflection coefficient to account for the fact that reflections from the roof or
ground could add constructively with the incident wave at the point in question. The equation for
power density is
EIRP·PRC S=----=--40n-· Rd
S is power density in mw/cm2
EIRP is in watts
PRC is the power reflection coefficient (we will use 2.56 for most applications, as specified by the
EPA)
Rd is the radius, direct distance from antenna (bottom) to point of interest, meters
Cylindrical Model
The concept of the cylindrical model is to take the power actually delivered to the antenna, Pt (NOT
EIRP) and assume it is equally distributed over the surface of a cylinder of the same length as the
antenna. If the antenna is a directional antenna then we reduce the surface area of the cylinder by
BW/360 (BW is the 3-dB beam-width in degrees). This is a good near-field model. Additionally, if
the antenna is mounted above the level, the average power density in a 6-foot tall area immediately
above the rooftop level (or where a person might be standing or located), is reduced according to
how far above/below the person the antenna is mounted.
The equation for the power density is then:
S = (BW) 20·1l·L ·R · -a h 360
S is the power density in mw/cmA2
P1 is the actual (or worst case assumed) power delivered to the antenna,
watts
K(HtbLa) is the correction factor for antenna mounting height
Ha is the antenna mounting height, feet
La is the length of the antenna, meters
Rh is the horizontal distance along roof from antenna to point of interest,
meters
BW is the 3-dB beam-width of antenna
K(Ha,La) 0.5-0.14656 · H a 0 <= Ha < 6
0.17532-0.01076·Ha 6 <= Ha < 10
0.06772 lO<=Ha
K( Ha.La) makes corrections for antennas mounted lower than the roof level and for antennas shorter than
6feet.
Roof or Grmmd Level
Exposure Modeling
Using Spherical and Cylindrical Modeling, it is the policy of Sprint PCS to perform sufficient analysis
on each site to assure that the above mentioned FCC Rules and Regulations are being met. Sprint
PCS proprietary software is used to model RF exposure conditions on rooftops and in any other
areas that our antennas are used. In this situation, the antennas are mounted inside a fake palm
tree.
-------··-···-~-····-··-········ .. ··-····
· .. ~
The following are a summary of the results obtained from our in-house modeling tools for
this site.
Results for SD25XC154 (Front of Antenna) Figure 1-2
Cylindrical Model
Height
Length of Antenna
m-Width
Figure 1·3
100
90
eo
70
eo i 50
.,. 40
311
20
IG
General
.-----~ 48 watts I---~1~9~40~MHz
0 feet
t-----:2::""';5=tfeet
6.5 degrees ._ __ __,
Percent of fltPE vs. Horirontal Distance (1 Antenna)
Cylindrical Model
0 ~~----~----~~~----~~L-~----~--~~--~~~------~ 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12A:I 13.0 14.0 IS.O 16.o 17.0 18JI 19.0 20.0
-(II)
The results of the analysis show in Figure 1-2 that to incur 100% of the Maximum Permissible
Exposure levels an individual would have to be directly within 7.5905 feet of the front of the
antenna in it's main beam. This could only occur if an individual climbed in front of the antenna or
placed a bucket truck less than !&_feet from the front of the antenna. Figure 1-3 shows how rapidly the
Power Density levels fall off (in percent of FCC maximum), as the distance increases.
Results for SD25XC154 (Back of Antenna) Figure 1-4
Cylindrical Model
ransmit Power
Frequency
nro,nn<> Height
Length of Antenna
General
Figure 1-5
3 s 8
.---.,....,.='"'"' .1.5175 watts
l940 MHz
Q feet 1----~ 2;5 feet 1---..;;._-1 65, degrees '------"'
Percent oiiiiPE 111. Horlrantal OISiance (1 Amtenna)
Cylindrical Model (Back of 1111enna 15riB F19 rirll•)
8 IMI-•~ 12 13 I• 15 16 1; 18 19 2)
The results of Figure 1-4 and 1-5 show that to incur 100% of the Maximum Permissible Exposure
levels from the back of the antenna an individual would have to be directly within 0.2400 feet. fu
other words, the person would have to be behind the antenna and closer than 3 inches. Again, since these
antennas are mounted above ground level with limited access, this is unlikely to occur.
. . c
Maintenance Safeguards
Routine maintenance within 8.0 feet of the antennas is no cause for concern. If for some reason the
antennas need to be moved or handled then the regional RF Manager at Sprint PCS should be
notified or you may call at 1-888-859-1400 to facilitate a power down.
Summary
As can be seen from the data, these antennas are mounted on a OTHER above ground level.
An individual would have to come within less than 8.0 feet of the front of the antenna and/or
within 3 inches (or touch the back of the antenna) to reach anywhere close to FCC maximum
exposure limits. Since these antennas are mounted above ground level, with limited access,
this is unlikely to occur.
Exposure to Radio Frequency Electromagnetic Fields is of great concern to Sprint PCS and we
evaluate all sites for compliance to current FCC rules and regulations. We are continually striving to
improve the quality of our modeling techniques through continuous improvement of our software
tools and training procedures. We recognize our role as an industry leader to place the health and
welfare of the public and occupational workers in high regard and we will continue to do so through
mandatory modeling and measurements as required. We determine the hazard that is present and
inform occupational workers through training and appropriate signage.
Please don't hesitate to call if you should have any questions or are in need of any further
information regarding the RF emissions from this site.
Sincerely,
Dave Kirk, RF Manager
Regulatory Compliance
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