Nortel WLAN Security Switch 2361 Guia de Instalação Página 84
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84 Appendix
NN47250-506 (324883-B Rev 02 Version 02.02)
In addition to the free space path loss mentioned above, RF signals will be attenuated as they pass through
objects such as foliage, walls and buildings. The level of signal attenuation in these instances can increase the
loss and reduce the communications range by an additional amount of 10 to 20 dB or greater. Care should be
used when installing the antennas and access points to ensure that no objects or barriers are blocking the
communication paths of the antennas.
Most, if not all, antenna performance characteristics are specified under free space conditions. It is important
to realize that these performance characteristics may change once the antenna is located in its operating
environment. Surrounding objects, such as the earth, walls, buildings, floors, etc. will impact the antenna's
specified performance. The fact that antenna performance may change in the operating environment does not
invalidate the use of free space data. It is impossible to specify performance for all environments and the free
space performance characteristics provide the most suitable reference for comparing relative antenna
performance.
When an antenna is located near the earth, its radiated field couples with the earth and changes the antenna's
radiation pattern and impedance characteristics. The antenna impedance is changed from its free space value
by the addition of a component known as ground impedance. The presence of this component changes how RF
energy is delivered to the antenna in that some energy normally radiated by the antenna is now dissipated in the
earth. This will reduce the system efficiency.
In addition to impacting the antenna impedance, the earth also changes the antenna's radiation pattern and
polarization depending upon the height the antenna is located above the ground. When an antenna is located
over the earth, an "image" is generated in the earth. This image will contribute to the total radiated field by
vector summing the direct and reflected waves. This is essentially a multipath phenomenon and illustrates how
the antenna height affects pattern performance. Mechanical down-tilt can be used to try and compensate for
these effects. Down-tilt refers to tilting the main beam downward, away from the perpendicular with the
horizon. Mechanical down-tilt really only applies to sectorized antennas that have narrow horizontal
beamwidths of less than or equal to 60 degrees. The narrower the azimuth pattern, the more uniform the tilt
will be across the 3-dB beamwidth of the antenna.
Optimizing antenna location can reduce multipath and interference problems. This includes antenna height, as
well as, location relative to nearby objects. Protecting against multipath fading is difficult and may require
other techniques, such as diversity, to mitigate multipath interference. Overall antenna selection and location
optimization is not an arbitrary task. It does require an evaluation of system coverage and range requirements,
a review of access point locations, and a review of surrounding objects that may become a source of
interference.
- Solution Guide 1
- Contents 3
- 6 Contents 6
- Outdoor Solution 7
- Customer service 8
- 2332 Access Points 9
- Canadian IC statement 10
- Declaration of conformity 11
- Радио Модел 12
- Community 14
- Transmit Power Control (TPC) 15
- Taiwan Compliance Statement 16
- United States and Canada 18
- 2.4 GHz Band 18
- 5.0 GHz Bands 18
- External Antenna Statement 22
- Country 2.4 GHz 5.0 GHz 23
- Warning conventions 27
- Radio safety warnings 29
- Earth ground warning 35
- Introduction 39
- Package contents 40
- Signal path distance 41
- Antenna polarization 41
- Signal path clearance 41
- Physical site survey 41
- Physical site 42
- Hardware installation 43
- Installation 47
- Grounding principles 48
- Figure 6. Drip Loops 49
- Outdoor external antennas 50
- Coax cable seal installation 51
- Software installation 53
- Site Planning 58
- Safety Precautions 59
- Reference Information 60
- Applying coax seal tape 61
- Figure 14. Mounting Bracket 62
- Terminal Strip Connection 66
- Software 67
- Appendix 69
- Surge Suppression 70
- Appendix 75 75
- 76 Appendix 76
- Appendix 77 77
- Antenna properties 78
- Appendix 79 79
- Effective Radiated Power 80
- Polarization 80
- RF Propagation and Path Loss 82
- Appendix 83 83
- 84 Appendix 84
- Appendix 85 85
- 5.15 GHz 86
- 5.47 GHz 86
- 5.85 GHz 86
- 88 Appendix 88
- Appendix 91 91
- 92 Appendix 92
- Appendix 93 93
- 94 Appendix 94
- Appendix 95 95
- 96 Appendix 96
- Appendix 97 97
- 98 Appendix 98
- Appendix 99 99
- 100 Appendix 100
- Appendix 101 101
- 102 Appendix 102
- Appendix 103 103
- 104 Appendix 104
- 2462 MHz 105
- 2412 MHz 105
- 2437 MHz 105
- 106 Appendix 106
- Appendix 107 107
- 108 Appendix 108
- Appendix 109 109
- 110 Appendix 110
- Appendix 111 111
- 112 Appendix 112
- Appendix 113 113
- 114 Appendix 114
- Appendix 115 115
- 116 Appendix 116
- Appendix 117 117
- 118 Appendix 118
- Appendix 119 119
- Figure 23. Top view 119
- Figure 24. Bottom view 119
- 120 Appendix 120
- Figure 25. Side view 120
- Figure 26. Mounting screws 120
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