User's Manual

Part # 34357-MNL Rev.03 SPEEDLAN 9200 User Guide
2-16
Note: For long distances, additional antenna height is often required to overcome
signal diffraction and to provide clear Radio LOS. For Radio LOS, a clear Fresnel
(Freh-nel) zone is required to minimize diffraction effects. The Fresnel zone is shaped
like an elongated football. The most clearance is required at the mid-point between the
two sites.
Beyond approximately 10 miles, the curvature of the earth can also become significant.
At these longer distances, visually sighting the remote site can be difficult or impossible
due to atmospheric haze. Terrain data (map or differential GPS) must be relied upon for
determining path clearance. Elevation data determined with these methods is above
Mean Sea Level; and does not account for curvature of the earth. Both the curvature of
the earth and the Fresnel clearance numbers can be combined to determine the
additional clearance required above any natural or man-made obstructions along the
path.
Obtaining this clearance can be accomplished by raising the antenna height at one or
both sites. If this is not practical, then consider relocating one or both sites to locations
with higher elevations. Another option is to add a third site to go over or around the
obstacle.
If you see any obstructions between two antennas, move one or both antennas to
another location.
Step 2. Mounting the Antenna
Follow the instructions below to mount the antenna.
a On a side-building mount, position the bracket so there will be at least three
feet (one meter) above the roof line where the pole is attached. This enables
room for the antenna and reduces signal loss from building reflection.
Note: It is not recommended to mount the antenna onto any unstable object.
b Allow for as much space between the wall brackets as possible while
maintaining the appropriate antenna height. For extended poles, additional
wall brackets may be necessary.
c Assemble the antenna and mount it to the pole using the included V-bolt
antenna mounting hardware. For a semi-parabolic grid type antenna, align
the grid to run parallel with the grid on the tip of the antenna horn.