The Best Antenna for the Best Scenario


Looking at a laundry list of antennas and their capabilities might overwhelm you. Now that the raw data has been presented, we show you a few examples of how these antennas can be used.

Warehouses

Because warehouses and manufacturing facilities are large installations, an omni-directional antenna, mounted at 25 feet up, provides good coverage. You want to place the antenna high enough so that it clears racks of equipment. However, you don't want to place it so high that you lose range. Remember that although omnidirectional antennas radiate in a 360-degree horizontal plane, they don't often exceed 75 degrees vertically.

Optimally, you can locate the antenna in the center of the facility. However, in cases where an antenna must be placed against a wall, a directional antenna is best.

Offices

It should come as no surprise that different sized offices will require different antennas:

  • Small offices are well suited with an omnidirectional antenna. However, if the antenna is located in the back of the office, a directional antenna can improve performance. The antenna should be wall mounted, above as many obstructions as possible.

  • Large offices are best served with omnidirectional antennas, mounted just under the ceiling girders or the drop ceiling. Ideally, the antenna is placed in the center of the coverage cell and in as open an area as possible. Again, if it must be placed against a wall, a directional antenna is ideal.

Bridging

Antennas for wireless bridging vary, and they depend on the type of bridging you employ:

  • Point-to-point deployments must take into consideration distance, obstructions, and the antenna's location. If connecting indoors, a dipole or mast mount omnidirectional antenna can be used. When used outdoors, a directional high-gain antenna should be used. Locate these antennas as high as possible and avoid obstacles.

Note

You can even increase outdoor ranges if you use a parabolic dish antenna25 miles with 2.4-GHz systems and 12 miles with 5-GHz systems.


  • Point-to-multipoint bridges generally use two different types of antennas. At the main communications point, an omnidirectional antenna should be used. Remote sites use directional antennas that are aimed at the main site's antenna. This is shown in Figure 2-7.

    Figure 2-7. The Main Communications Point in a Point-to-Multipoint Solution Should Employ an Omnidirectional Antenna, Whereas Remote Sites Should Use Directional Antennas





Cisco 802.11 Wireless Networking Quick Reference
Cisco 802.11 Wireless Networking Quick Reference
ISBN: 158705227X
EAN: 2147483647
Year: 2005
Pages: 126

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