Dell PowerConnect W-AP175 Dell PowerConnect W-AP175P Installation Guide - Page 8

Identifying Known RF Absorbers/Reflectors/Interferences Sources Identifying known RF absorbers/reflectors/interference sources while out in the field during the installation phase is critical. Even though outdoor environments consist of fewer RF absorbers/reflectors/interference sources compared to indoor environments, ensure that these sources are identified and taken into consideration when installing and mounting an AP to its fixed outdoor location. RF Absorbers  Cement/Concrete  Natural Items: Trees/vegetation  Brick RF Reflectors  Metal Objects: Roof-installed air-conditioning equipment, chain link fences (depending on aperture size), other wire fences, or water pipes RF Interference Sources  Other 802.11a/b/g/n or broadband access equipment operating nearby  Industrial RF welding equipment or other Industrial, Scientific and Medical (ISM) equipment that utilizes RF to heat or alter the physical properties of materials  Military, Commercial Aviation or Weather Radar Systems Line of Sight (Radio Path Planning) A wireless bridge or mesh link requires a "radio line of sight" between the two antennas for optimum performance. The concept of radio line of sight involves the area along a link through which the bulk of the radio signal power travels. This area is known as the first Fresnel Zone of the radio link. For a radio link, no object (including the ground) must intrude within 60% of the first Fresnel Zone. Figure 4 illustrates the concept of a good radio line of sight. Figure 4 Line of Sight Visual Line of Sight Radio Line of Sight If there are obstacles in the radio path, there may still be a radio link but the quality and strength of the signal will be affected. Calculating the maximum clearance from objects on a path is important as it directly affects the decision on antenna placement and height. It is especially critical for long-distance links, where the radio signal could easily be lost. When planning the radio path for a wireless bridge or mesh link, consider these factors:  Avoid any partial line of sight between the antennas  Be cautious of trees or other foliage that may be near the path, or may grow and obstruct the path. 8 Dell PowerConnect W-AP175 Outdoor Access Point | Installation Guide