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Measuring Signal Performance
9.1 Introduction
The performance of a microwave link (wireless link established between two outdoor antennas) is closely related to the
following factors:
•
Range
•
Fresnel Zone
•
Clearance Factor
Calculating the above factors help you align the antennas properly and achieve a better throughput.
9.2 Determining the Range
Range is the maximum distance a microwave link travels and is based on the:
•
Type of the outdoor antenna equipment (Outdoor antennas differ in technical specifications).
•
Data speed of the wireless link.
•
Clearance of the signal path (see
Use the following formula to determine the range of the microwave link:
Range = Maximum Range x Clearance Factor
1. Maximum Range: It is the theoretically calculated value achieved under optimal circumstances, by using the
available products and their technical specifications that comply with the local radio regulations. The calculations
made assuming the optimal radio conditions do not guarantee of achieving the same maximum distance at your
location.
2. Clearance Factor: See
Variations in calculations of the above two factors occur due to any of the following reasons:
•
Incorrect alignment of antennas.
•
Polarization mismatch of the antennas.
•
Sources of interference or unexpected reflections in the signal path that affect the quality of communication (Refer
Determining the Optimal Antenna
•
Severe weather conditions such as heavy rainfall, snow or strong winds.
•
Unexpected obstacles in the link path.
•
Seasonal influences such as leaves on trees or icing of the antennas.
9.3 Fresnel Zone
The narrow antenna beam emerged from the antennas contain a bulged area called as Fresnel Zone. The first Fresnel Zone is
known to be an imaginary boundary line offset along the direct path of the signal, where a signal reflected will travel an
additional one-half distance of wavelength. Each succeeding Fresnel Zone boundary adds an additional half-wavelength to
the reflected path distance than the direct signal path between the antennas.
When any significant part of the Fresnel Zone is obstructed, a portion of the radio energy is lost that results in reduced
performance. Reduced performance can also occur when obstacles close to the antenna beam cause signal reflections or
noise that interfere with the radio signal.
Weather conditions (rain or snow) usually do not have much impact on the performance of your device, provided you have
sealed all the cable connectors with weatherproofing tape. Seasonal influence on signal propagation can occur in the
following situations:
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AP-9200R - Hardware Installation Guide
Clearance
Factor).
Clearance
Factor.
Placement).
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