Proxim Tsunami MP.11 manual a.Neighboring buildings

Tsunami MP.11 Antenna Installation

The definition of the 1st Fresnel zone is an imaginary boundary line offset along the direct signal path. This boundary is defined as the point where if a signal were reflected between the two antennas, it would travel a distance exactly one-half wavelength longer than the direct-path signal. Each succeeding Fresnel zone boundary adds an additional half-wavelength to the reflected path distance between the antennas.

Signals reflected from any even-numbered Fresnel zone result in signal cancellation; those from odd-numbered Fresnel zones add to the direct path signal.

The exact shape and width of the Fresnel Zone is determined by the path length and frequency of the radio signal. The width as distance from the direct antenna beam is approximately 6 m (21 ft) in the middle of the wireless link for a distance of 6.5 Km (4 mi) and a frequency of 5.8 GHz. This width also is the required clearance of the antenna beam from obstacles in its path, to avoid loss of radio signal.

When any significant part of this zone is obstructed, a portion of the radio energy is lost, resulting in reduced performance. Reduced performance also can occur when obstacles close to the antenna beam cause signal reflections or noise that interfere with the radio signal.

The following figure shows some typical examples of obstacles you must avoid for the directional antenna to operate effectively:

a.Neighboring buildings

b.Trees or other obstructions

c.Power lines

For optimal performance, you must ensure that the type and placement of the antennas leave sufficient clearance of the Fresnel Zone at the maximum width of the bulge, which is typically at the mid-point between the antennas.

Figure 2. Potential Obstacles for a Directional Antenna

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