standards and guidelines for communication sites - Radio And ...
standards and guidelines for communication sites - Radio And ... standards and guidelines for communication sites - Radio And ...
ENGINEERING CONSIDERATIONS APPENDIX A: ELECTROMAGNETIC ENERGY INFORMATION A.3.7 UPTIME 11.D-8 14.D-9 17.D-10 21.D-11 12.C-8 C 15.C-9 18.C-10 22.C-11 24.C-12 13.B-8 16.B-9 19.B-10 23.B-11 25.B-12 FIGURE A-10 COMPOSITE RF FIELDS WITH FIVE ANTENNAS TRANSMITTING The combined fields produce levels exceeding the MPE allowed in all areas surrounding the antennas. In these situations, some means of controlling exposure must be used. These techniques may include RF protective clothing, re-engineering the antenna system, or power shutdown or reduction when working in the area. While power shutdown or reduction may appear to be an effective technique, either may be impractical for wireless communications services. It is normally reserved for broadcast transmitters. One preferred method of addressing this is to elevate the antennas above the roof area. Complex antenna sites have a “personality” that makes them unique. The personality of the site is not only determined by the RF power, frequency, and manufacturer of the equipment, but by the operational characteristics. The RF level and frequency can be determined by understanding the equipment specifications, but operational characteristics can only be quantified by monitoring the usage. Because of the high number of pagers, paging transmitters will have a very high transmitter duty cycle. Trunking (SMR) transmitter activity will depend on customer loading density. This can range from transmitters rarely transmitting, to transmitters rarely not transmitting. Private customer equipment will have a very diverse usage characteristic that can not be predicted. The important point in understanding the characteristics of different services is that they can seldom be predicted. Additionally, characteristics for transmitters will change due to cultural elements. Transmitters located in Las Vegas will have considerably different uptime characteristics than transmitters located in San Antonio, Texas or New York City. Tests have shown that a site will vary significantly from one time period to another. Sample measurements on a roof of a large building showed a variation in transmitter activity of over 30% between 11:00 a.m. and 2:00 p.m. Uptime relates to all of the transmitter activity of a site. Uptime can seldom be predicted or characterized precisely, and thus usually must be measured. The amount of Uptime directly affects the EME exposure levels on a site. A-18 68P81089E50-B 9/1/05 27.D-13 28.C-113 29. B-13
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES ENGINEERING CONSIDERATIONS In the consideration of site activity, there is an upper level of 100% uptime, or when all transmitters are keyed and actually energized. Actual usage would be the most accurate consideration, but least practical to implement. Actual usage varies greatly over time and antenna. Each antenna has an uptime characteristic based on density of combining, transmitter usage, and activity. While the use of Uptime could provide a better approach to predicting the actual levels that could be encountered, it proves to be impractical. Determining the Uptime characteristics can be very complex and change with time. Only by constantly monitoring and adjusting the model can uptime be used. Uptime cannot be theoretically calculated, it must be measured. Measurement of uptime involves high speed scanning of frequencies over a long period of time. Only after thousands of activity observations taken over days of monitoring will the worst case, actual, and instantaneous uptime be understood. This complex procedure creates uncertainty. Practically, the uptime that should be used in the analysis of complex sites usually is 100% or total uptime. A.3.8 ANTENNA SITE DOCUMENTATION Any evaluation is only as accurate as the data used to make the evaluation. Antenna site documentation is important and shall be done in a standardized manner. For the analysis of EME fields, there are two methods of documentation. One proves to be considerably more exact but both allow an engineer to understand the EME situation and apply the proper compliance procedures, if necessary. A.3.8.1 ACTUAL DOCUMENTATION Actual documentation provides an accurate picture of the site situation. Actual documentation can be used by engineers for purposes other than EME analysis. Proper documentation requires a detailed description of transmitters, cable, antennas, and location on the tower. Specifically, the following information is required: • Transmitter frequency by antenna mount • Power out of transmitter • Network loss between transmitter and antenna • Antenna characteristics and specifications • Antenna location and standoff • Uptime characteristics • Areas frequented by personnel • Layout of antenna field (roof or tower) 68P81089E50-B 9/1/05 A-19
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STANDARDS AND GUIDELINES FOR COMMUNICATION SITES ENGINEERING CONSIDERATIONS<br />
In the consideration of site activity, there is an upper level of 100% uptime, or when all<br />
transmitters are keyed <strong>and</strong> actually energized. Actual usage would be the most accurate<br />
consideration, but least practical to implement. Actual usage varies greatly over time <strong>and</strong><br />
antenna. Each antenna has an uptime characteristic based on density of combining, transmitter<br />
usage, <strong>and</strong> activity.<br />
While the use of Uptime could provide a better approach to predicting the actual levels that<br />
could be encountered, it proves to be impractical. Determining the Uptime characteristics can be<br />
very complex <strong>and</strong> change with time. Only by constantly monitoring <strong>and</strong> adjusting the model can<br />
uptime be used. Uptime cannot be theoretically calculated, it must be measured. Measurement<br />
of uptime involves high speed scanning of frequencies over a long period of time. Only after<br />
thous<strong>and</strong>s of activity observations taken over days of monitoring will the worst case, actual, <strong>and</strong><br />
instantaneous uptime be understood. This complex procedure creates uncertainty. Practically,<br />
the uptime that should be used in the analysis of complex <strong>sites</strong> usually is 100% or total uptime.<br />
A.3.8 ANTENNA SITE DOCUMENTATION<br />
Any evaluation is only as accurate as the data used to make the evaluation. Antenna site<br />
documentation is important <strong>and</strong> shall be done in a st<strong>and</strong>ardized manner. For the analysis of<br />
EME fields, there are two methods of documentation. One proves to be considerably more exact<br />
but both allow an engineer to underst<strong>and</strong> the EME situation <strong>and</strong> apply the proper compliance<br />
procedures, if necessary.<br />
A.3.8.1 ACTUAL DOCUMENTATION<br />
Actual documentation provides an accurate picture of the site situation. Actual documentation<br />
can be used by engineers <strong>for</strong> purposes other than EME analysis. Proper documentation requires<br />
a detailed description of transmitters, cable, antennas, <strong>and</strong> location on the tower. Specifically,<br />
the following in<strong>for</strong>mation is required:<br />
• Transmitter frequency by antenna mount<br />
• Power out of transmitter<br />
• Network loss between transmitter <strong>and</strong> antenna<br />
• Antenna characteristics <strong>and</strong> specifications<br />
• Antenna location <strong>and</strong> st<strong>and</strong>off<br />
• Uptime characteristics<br />
• Areas frequented by personnel<br />
• Layout of antenna field (roof or tower)<br />
68P81089E50-B 9/1/05 A-19
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