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HomeMy WebLinkAboutFORT COLLINS CLUB WIRELESS TELEPHONE FACILITY - PDP/FDP - 11-01 - CORRESPONDENCE - WTE / WTF INFORMATIONIf you should have any questions or are in need of any further information regarding the RF emissions from this site you may contact me at the below listed number. Michael D. Lawson Date Senior RF Engineer National Regulatory Compliance & RF Product Test (913) 315-2383 100 90 80 70 60 50 40 30 20 10 0 Figure 1-5 Percent of MPE vs. Horizontal Distance (1 Antenna) Cylindrical Model 1 I I 1 1 • L J L J ♦ L J L J 3 L J ..L J l 1 1 1 I I I 1 I I I 1 1 1 1 _____, __________r I ________________1 I 1 1 _ ____--- 1 ____ _____�___ __�_____,____ --- ____ 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 ----=-----=-----'- 1 1 1 ---- '-----'----- '----- 1 I '-----'----------------i-----�------ �- 1 1 ---------- ---i- --- 1 -- -- - ---• 1 1 1 1 1 1 1 1 1 1 I I 1 • L J L J t L J L J ♦ L J _L J ♦ 1 1 1 1 1 1 I 1 1 1 1 1 1 1 ----' ----=----- 1 1 --- '- 1 --------- � 1 I 1 1 I 1 1 1 I 1 1 1 1 1 1 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 Distance (ft) �— General OccupationE The results of Figure 1-3 and 1-4 show that to incur 100% of the Maximum Permissable Exposure levels from the back of the antenna an individual would have to be directly within .0019 feet. In other words the person would have to touch the back of the antenna. Again since this antenna is mounted 7.5ft off the roof top. This is unlikely to occur. Maintenance Safeguards Routine maintenance within 3 ft of the antennas are 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 7.5 ft off the above the roof top and a individual would have to come within 2 ft of the front of the antenna and touch the back of the antenna to reach any where close to FCC maximum exposure limits. Since these antennas are mounted 7.5 ft off the roof top, 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. 100 90 80 70 60 so 40 30 20 Percent of MPE vs. Horizontal Distance (1 Antenna) Cylindrical Model , i r i i . . - , - _ --' S -------'------ -------------- ' --- �---i-----'-----'-----'-----'-----'-----'-----'--_--'-----r----=- T= --- -- - 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 Distance (ft) Figure 1-3 �-General -0- Occupation The results of the analysis show in Figure 1-2 that to incur 100% of the Maximum Permissable Exposure levels an individual would have to be directly within 2.01 ft 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 2ft from the antenna above ground level and 7.5 ft above the roof top. Figure 1-3 shows how rapidly the Power Density levels, in percent of FCC maximum, fall off as the distance increases. Results for DN40XC961 (Back of Antenna) Figure 1-4 Cylindrical Model t Power 0.012 watts icy 1940 MHz i Height 0 feet Length of Antenna 4.67 feet 4cIth 65 degrees Exposure Limit Percent # Ant. 100.00% 1 50.00% 2 33.33% 3 5.00% 20.0 General Occupational 1.00 5.00 mw/cmZ feet feet feet feet Distance 0.00 0.00 0.00 0.00 0.01 0.00 0.04 0.01 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 towers and in any other areas that our antennas are used. In this situation the antennas are mounted 7.5 ft above the roof top level situated on a roof. The following are a summary of the results obtained from our in-house modeling tools for this site. Results for DN40XC961 (front of Antenna) Figure 1-2 Cylindrical Model mit Power 12.71 watts ency 1940 MHz na Height 7.5 feet al Length of Antenna 4.67 feet -Width 65 degrees Exposure Limit Percent # Ant. General Occupational 1.00 1 5.00 mw/cmz Distance 100.00% 1 0.24 0.05 feet feet feet 50.00% 2 0.49 0.10 33.33% 3 0.73 0.15 5.00% 20.0 1 4.89 0.98 feet Cylindrical Model The concept of the cylindrical model is to take the power actually delivered to the antenna, P, (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 rooftop level, the average power density in a 6- foot tall area immediately above the roof level (where a person might be standing) is reduced according to how far above the roof the antenna is mounted. The equation for the power density is then P, • K(Ho , La S= BW 20 La • Rh ( 3 0) Antenna Rd H. Rh Hn Roof or Ground Level 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 (47rr), for the distance r away from the antenna. In general we will consider the shortest distance between the antenna and a six 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 407r • R d 2 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 Sprint PCS evaluates all sites, to determine the percent of exposure incurred by the General public and also Occupational exposure resulting from the operation of our antennas. This is an issue that we take very seriously, 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 the above mentioned site. Current FCC -adopted Exposure Limits In FCC 96-326, the FCC adopted new exposure guidelines. The guidelines are given in terms of mw/cm^2 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 IEEE/ANSI 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 5.0 mw/cm2 for general public and occupational cases, respectively. Figure 1-1: FCC Exposure Limits. - *-=-splinto Michael Lawson - Senior RF Engineer-NEPA Compliance PCS 11880 College Boulevard Overland Park, KS 66210 Ph(913) 315-2383 (913) 315-2541 Date: 4127/01 To: Ft Collins Planning and Zoning From: Michael Lawson RE: FCC NEPA Compliance for Site DN40CX961 Site Address: 1307 E. Prospect Road, Ft Collins CO 80525 Site Description: Non Communication Tower Site Owner: Sprint PCS The purpose of this letter is to demonstrate compliance with FCC standards in regards to the electromagnetic emissions from the roof top, site DN40CX961, located at the above mentioned address. 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 Absorbtion 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 5.00m/cm^2 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 outdoor antennas are designed to concentrate the majority of their signal power out of the front of the antenna in a very thin beam. These installations consist of three antennas each designed to cover 120 degrees for a total of 360 degrees of coverage. 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 roof top antenna installation operating 7.5 feet above the roof top level using 65 degree beamwidth antennas.