Product Manual

Installation of Radio and Modem
45
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 11. 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 11
2 Degree Beamwidth
Version 2.0