User's Manual

February 2003
Rev. A
Page 15 of 47
between the two antennas. Any obstacles in the path of the “line” degrade the propagation
path. The best propagation path is, therefore, a clear line of sight with good clearance
between the “line” and any physical obstacle.
Physical Obstacles
Any physical object in the path between Au and SU can cause signal attenuation.
Common obstructions are buildings and trees. Any buildings or other physical structure such as
trees, mountains or other natural geographic features higher than the antenna and situated in the
path between the two sites can constitute obstructions. Install outdoor antennas high enough to
avoid any obstacles, which may block the signal.
Minimal Path Loss
Path loss is determined mainly by several factors:
• Distance between sites – Path loss is lower and system performance better when
distances between sites are shorter.
• Clearance – Path loss is minimized when there exists a clear line of sight. The number,
location, size, and makeup of obstacles determine their contribution to path loss.
• Antenna height – Path loss is lower when antennas are positioned higher. Antenna height
is the distance from the imaginary line connecting the antennas at the two sites to “ground”
level. “Ground” level in an open area is the actual ground. In dense urban areas, “ground”
level is the average height of the buildings between the antenna sites.