MRV Communications MRW55, User Manual

Page: 37 / 244

Radio Path Planning
3-5
3
A wireless bridge link is deployed to connect building A to a building B, which is
located three miles (4.8 km) away. Mid-way between the two buidings 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 contructed 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 bulding A. To mount an anntena at the
required height on building B, a mast or pole of only 1.3 m (4.3 ft) is needed.
Warning: 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 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 must be considered:
• Be sure there are no other radio antennas within 2 m (6 ft) of the wireless bridge
• Place the wireless bridge away from power and telephone lines
• Avoid placing the wireless bridge too close to any metallic reflective surfaces, such
as roof-installed air-conditioning equipment, tinted windows, wire fences, or water
pipes
• The wireless bridge antennas at both ends of the link must be positioned with the
same polarization direction, either horizontal or vertical
A
B
3 miles (4.8 km)
5.4 m
17 m
20 m
2.4 m
12 m
9 m
1.4 m
Visual Line of Sight
Radio Line of Sight