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802.11a Bridge BR5811b MTI Proprietary Page 17
2-9 Align the Antenna (TBD)
Antenna alignment is performed with both the near-end and the far-end terminals operating.
The antenna position is adjusted while monitoring the RSSI for antenna alignment voltage. The
higher the RSSI voltage reading is, the stronger the signal. The range of the RSSI voltage
reading is from 0 to 3.28VDC, and the resolution is 256 divisions.
Caution: To ensure optimum system performance, the main lobe of the antenna must be aligned with the center
of the far end antenna. Rotate the antenna through the range of radiated power so the main lobe can be positively
identified. Each side lobe is approximately 20 dB lower than the preceding lobe as you move away from the main
lobe.
This antenna alignment procedure is applicable to both protected and non-protected system
configurations. Align the antenna as follows:
Note: Repeat this procedure if the initial alignment does not produce the correct RSSI reading.
1. Consult your path calculation and adjust the radio’s attenuation level, so do not exceed
the maximum receiving signal level.
2. Verify that the Bridge at the far end is operational.
3. At the near-end Bridge, remove the protective cap from the RSSI BNC connector.
4. Connect a voltmeter to the RSSI connector and set the voltmeter to measure VDC.
5. Pivot the antenna slowly in the azimuth direction. Monitor the voltmeter and locate the
position where the voltage is minimum (null) and record the reading.
6. Monitor the voltmeter and pivot the antenna in the elevation direction. Pivot the antenna
to the position where the voltage is minimum on the voltmeter and record the reading.
7. Repeat these steps as necessary to get an accurate reading.
8. Tighten all fasteners and check that the null has not changed. If the null has changed,
repeat the procedure until the null is maintained after tightening the fasteners.
9. Disconnect the voltmeter and replace the RSSI protective cap.
Note: The signal level over the link is not optimal until both antennas are correctly aligned.