Dell PowerConnect W-AP175 Dell PowerConnect W-AP175P Installation Guide - Page 10

Figure 5 Antenna Height and Line of Sight Visual Line of Sight 3 miles (4.8 km) 2.4 m A 20 m 17 m 5.4 m Radio Line of Sight B 1.4 m 9m 12 m A wireless bridge or mesh link is deployed to connect building A to building B, which is located three miles (4.8 km) away. Mid-way between the two buildings is a small tree-covered hill. From the above table it can be seen that for a three-mile link, the object clearance required at the mid-point is 5.3 m (17.4 ft). The tree tops on the hill are at an elevation of 17 m (56 ft), so the antennas at each end of the link need to be at least 22.3 m (73 ft) high. Building A is six stories high, or 20 m (66 ft), so a 2.3 m (7.5 ft) mast or pole must be constructed on its roof to achieve the required antenna height. Building B is only three stories high, or 9 m (30 ft), but is located at an elevation that is 12 m (39 ft) higher than building A. To mount an antenna at the required height on building B, a mast or pole of 1.3 m (4.3 ft) is needed. CAUTION: Never construct a radio mast, pole, or tower near overhead power lines. NOTE: Local regulations may limit or prevent construction of a high radio mast or tower. If your wireless bridge or mesh link requires a high radio mast or tower, consult a professional contractor for advice. Antenna Position and Orientation Once the required antenna height has been determined, other factors affecting the precise position of the wireless bridge or mesh link must be considered:  Be sure there are no other radio antennas within 2 m (6 ft) of the wireless bridge or mesh link. These include other WiFi radio antennas.  Place the wireless bridge or mesh link away from power and telephone lines.  Avoid placing the wireless bridge or mesh link too close to any metallic reflective surfaces, such as roofinstalled air-conditioning equipment, tinted windows, wire fences, or water pipes. Ensure that there is at least 5 feet clearance from such objects.  The wireless bridge or mesh link antennas at both ends of the link must be positioned with the same polarization direction, either horizontal or vertical. Proper alignment helps to maximize throughput. Radio Interference The avoidance of radio interference is an important part of wireless link planning. Interference is caused by other radio transmissions using the same or an adjacent channel frequency. You should first scan your proposed site using a spectrum analyzer to determine if there are any strong radio signals using the 802.11a/b/g channel frequencies. Always use a channel frequency that is furthest away from another signal. If radio interference is still a problem with your wireless bridge or mesh link, changing the antenna direction may improve the situation. 10 Dell PowerConnect W-AP175 Outdoor Access Point | Installation Guide