User's Manual

DragonWave Inc. 46
AirPair 100 UL 24 GHz Product Manual
6.3. Fine-adjust alignment of the radios
This section describes how to perform fine-adjust alignment of the radios. When
you prepare to align the radios, you must consider two important factors:
• Main Lobe and Side Lobes of Radio Waves
• Clear Line of Sight (LOS)
6.3.1. Main Lobe and Side Lobes of Radio Waves
When you align the radios, make sure you align to the Main Lobe of the
transmission. If you mistake a Main Lobe for a Side Lobe during installation,
there can be a 20-30 dB loss of signal strength. For example, if the Calculated
RSSI = -42 dB then the side lobe would be at approximately -62 dB, or 20 dB
lower than the calculated level.
The size of the beamwidth for the 24 GHz AirPair systems is approximately 2
degree, which is approximately equivalent to a thumb's width when the arm is
fully extended. Align as closely to the centre of the 2-degree beamwidth as
possible. It takes very little adjustment to swing past the main lobe, as can be
seen in Figure 6-7. A beamwidth of 2 degrees is narrow and alignment errors can
occur when you lock on to a Side Lobe instead of onto the Main lobe. If you align
to a Side Lobe and miss the Main Lobe, your signal strength is reduced. Make
sure you align the antenna to the Main Lobe.
Note: Verify the RSSI is within 2 dB of the calculated value.
Figure 6-7
2 Degree Beamwidth