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Tsunami MP.11 Antenna Installation
Copyright © 2006 Proxim Wireless Corporation. All rights reserved. 25
If any significant part of this bulged zone is obstructed, a portion of the radio energy is lost, which can affect the
performance of your wireless link in terms of maximum range and transmit rate.
In Figure 3, you see two variables that determine the shape of the antenna beam, also referred to as Fresnel
Zone:
• The distance between the antennas (a)
• The clearance required for optimal performance (b), where clearance should be interpreted as:
º Vertical clearance above the ground and the highest buildings or objects in the signal path
º Horizontal clearance from neighboring buildings and objects in the signal path
For optimal range and throughput performance, you must ensure that your antenna installation provides
maximum clearance in both horizontal and vertical direction.
Clearance should be interpreted as follows:
• In open areas without obstacles in the signal path, clearance is measured as height above the surface of the
earth. For example, if the antenna is mounted on the roof, this height includes the height of the building plus
the height of the mast above the rooftop.
• In areas with obstacles in the signal path between the two antennas, clearance should be measured as height
above the highest obstacle in the signal path.
• In dense urban areas, the clearance should be measured as height above the highest rooftop or any other
obstacles in the signal path between the two antennas.
For situations in which local authorities, the proprietor of the premises, or other factors do not let you set up an
antenna mast that lets you meet the listed clearance requirements, you may be unable to achieve a full line-of-
sight clearance. At the same time, however, when the distance that your wireless outdoor installation must cover
is less than the listed maximum range, you may not even need full clearance.
To determine the effect of insufficient signal path clearance, you must determine the Clearance Factor as
described below, and calculate its effect on the range for your antenna installation using the formula described in
“Determining the Outdoor Range” on page 23.
• If the clearance for your antenna installation is equal to or better than the minimum clearance requirement,
the Clearance Factor for your installation is 100%.
• If your actual clearance is less than the minimum clearance, use the diagram depicted in the following figure
to determine the actual range that applies in your situation.
Note: The Clearance Factor Diagram should be used as a rule-of-thumb for estimating the probable range in
case the clearance requirements are not fully met. In real life, using FCC approved products, you will also
find it almost impossible to achieve the level of clearance for maximum range, due to interference from
other radio products.