Aviat Networks ECLIPSE EDGE, User Manual

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260-668080-001 Rev 002 March 2013 33
Eclipse Edge User Manual
Edge Main Beams and Side Lobes
This section describes how to locate the main beam, and typical tracking path errors.
Refer to:
• Locating the Main Beam for Edge Antennas
• Tracking Path Error for Edge Antennas
Locating the Main Beam for Edge Antennas
Ensure the antennas are aligned on the main beam, and not a side lobe.
Once a measurable signal is observed, very small alignment adjustments are required
to locate the main beam. For instance, a 1.2m antenna at 23 GHz typically has 0.9° of
adjustment from center of main beam to the first null (0.4° to the -3 dB point).
Antenna movement across the main beam will result in a rapid rise and fall of signal
level. As a guide, 1 degree of beam width is equivalent to moving approximately 1.0
mm around a standard 114 mm (4.5 in.) diameter O/D pipe.
Antennas can be verified as being on main beam (as opposed to a side lobe) by
comparing measured receive signal level with the calculated level.
Signal strength readings are usually measurable when at least a main beam at one
end and first side lobes at the other are aligned.
The strongest signal occurs at the center of the main beam. The highest first lobe
signal is typically 20–25 dB less than the main beam signal. When both antennas are
aligned for maximum main beam signal strength, the receive signal level should be
within 2 dB of the calculated level for the path. This calculated level should be
included in the installation datapack for the link.
Figure 3-12 on page 3-33 is an example of a head-on, conceptual view of the beam
signal strength, with concentric rings of side lobe peaks and troughs radiating outward
from the main beam.S
Figure 3-12.
Indicative Head-on Signal Pattern for a Parabolic Antenna
Item Description
1 Center of main beam provides maximum signal level.
2 Outer edge of main beam, 3-10 dB below main beam.
3 Trough between main beam and first side lobe, 30 dB below main peak.
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