MEXICO INDEPENDIENTE
2.1 ORGANIZACIÓN DE LAS NACIONES UNIDAS (ONU) .1. HISTORIA DE LA ONU
2.1.3. ORGANISMOS ESPECIALIZADOS DE LA ONU
2.1.3.16. ORGANISMO MULTILATERAL DE GARANTIA DE INVERSIONES (OMGI) 1 HISTORIA
Side lobe signal readings can be mistaken for main lobe readings when signals are tracked on different elevation (or azimuth). Figure 4-9 shows a horizontal radio propagation model of the antenna, and signal levels at three different elevation positions (1-7 represent the measured signal level values of the received signal strength indicator (RSSI) port of the ODU.)
Figure 4-9 Three tracking paths
Signal levels for each path
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Head-on view of tracking paths for different elevations
l Line AA' represents that the main lobe of the antenna is almost aligned properly. The main lobe is at point 2, and the first side lobes are at points 1 and 3. Slightly adjust the azimuth of the antenna at point 2 until the peak signal appears.
l Line BB' represents that the elevation of the antenna slightly deviates from the main lobe.
The signal peaks appear at points 4 and 5. The signal peak at point 4 is higher than the signal peak at point 5 because of the antenna characteristics. As a result, point 4 may be mistaken for the peak point of the main lobe signal. The correct method is to set the azimuth of the antenna to the middle position between the two signal peaks. Then, adjust the elevation of the antenna until the three signal peaks of line AA' appear. Slightly adjust the elevation and azimuth of the antenna at point 2 until the peak signal appears.
l Line CC' represents that the elevation of the antenna completely deviates from the main lobe and is almost aligned with the first side lobe. The signal peak of the first side lobe at point 6 and the signal peak of the first side lobe at point 7 appear as one signal peak. As a result, points 6 and 7 may be mistaken for the peak point of the main lobe signal. The correct method is to set the azimuth of the antenna to the middle of points 6 and 7. Then, adjust the elevation of the antenna until the three signal peaks of line AA' appear. Slightly adjust the elevation and azimuth of the antenna at point 2 until the peak signal appears.
When the side lobe peak at one side is higher than the side lobe peak at the other side, as shown in Figure 4-10, a common error is to move the antenna left to right along line DD' or top to bottom along line EE' so that the three signal peaks of line AA' can appear. As a result, point 1 may be mistaken for the peak point of the main lobe signal. The correct method is to adjust the elevation in the middle of points 1 and 2 or the azimuth in the middle of points 1 and 3. Several adjustments are required so that the three signal peaks of line AA' can appear. Slightly adjust the elevation and azimuth of the antenna at point 2 as shown in Figure 4-9 until the peak signal appears.
Figure 4-10 Aligning the antenna with the first side lobe
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4.5.2 Aligning Single-Polarized Antennas
When you align single-polarized antennas, you need to align the main lobes of the antennas by adjusting the azimuth and elevation of the antennas at both ends.
Prerequisite
l The NE commissioning of the radio equipment at both ends of a radio link must be complete.
l The weather must be suitable for outdoor work. There should be no rain, snow or fog between stations.
l The on-site conditions must meet the requirements for an antenna to operate at a high altitude and the personnel required to commission the antenna must be trained to work at high altitudes
l The ATPC function must be disabled (the default status on the NE is Disabled).
l The AM function must be disabled (the default status on the NE is Disabled).
Tools, Equipment, and Materials
l Adjustable wrench
l Telescope, interphone, and socket-head wrench
l Multimeter (with a BNC connecter prepared at one end for future tests), and north-stabilized indicator.
Precautions
l If the radio link is configured in 1+1 protection mode and one antenna is used at each end, power off the standby ODUs at both ends before aligning the antennas. After the antennas are aligned, power on the standby ODUs at both ends.
l If the radio link is configured in 1+1 SD mode, align the antennas as follows:
1. Power on the active ODUs at both ends. Ensure that they are powered on during the alignment.
2. Power off the standby ODUs at both ends. Then, align the main antennas at both ends.
3. Power on the standby ODU at the local end. Retain the position of the main antenna at the remote end, and adjust the diversity antenna at the local end.
4. Power on the standby ODU at the remote end. Retain the position of the main antenna at the local end, and adjust the diversity antenna at the remote end.
l If the radio link is configured in 1+1 FD mode and two antennas are used at each end, align the antennas as follows:
1. At both ends, power on the main ODUs, power off the standby ODUs, and align the main antennas.
2. At both ends, power off the main ODUs, power on the standby ODUs, and align the diversity antennas.
CAUTION
You can adjust the azimuth and elevation of antennas by adjusting the related nuts or screws.
For details, see the related installation guide.
Procedure
Step 1 Determine the azimuth of an antenna according to the installation position and height of the antenna. Then, adjust the elevation of the antenna to the horizontal position.
Step 2 Connect a multimeter to the received signal strength indicator (RSSI) port on the ODU at the local end and test the voltage value VBNC.
TIP
It is recommended that you make the test line terminated with a BNC connector at one end in advance because it is more convenient to test the voltage value VBNC.
Figure 4-11 Testing the RSSI voltage by using a multimeter
Step 3 Adjust the azimuth and elevation of an antenna as follows:
1. Retain the position of the antenna at the remote end.
2. Use the multimeter to measure VBNC. At the local end, rotate the antenna widely in the horizontal direction.
When you rotate the antenna, the tested signal peaks may be as follows:
l Three signal peaks are tracked, for example, line AA' in Figure 4-9. In this case, adjust the azimuth of the antenna to the peak position at point 2 as shown in Figure 4-9.
l Two signal peaks are tracked, for example, line BB' in Figure 4-9. In this case, adjust the azimuth of the antenna to the middle of points 4 and 5 as shown in Figure 4-9. Then, adjust the elevation of the antenna so that the three signal peaks in the case of line AA' can appear. Adjust the antenna to the peak position at point 2 as shown in Figure 4-9.
l One signal peak is tracked, for example, line CC' in Figure 4-9. In this case, adjust the azimuth of the antenna to the middle of points 6 and 7 as shown in Figure 4-9. Then, adjust the elevation of the antenna so that the three signal peaks in the case of line AA' can appear. Adjust the antenna to the peak position at point 2 as shown in Figure 4-9.
3. Slightly adjust the elevation and azimuth at point 2 as shown in Figure 4-9 until VBNC reaches the peak within the tracked range.
4. Adjust the antenna until VBNC reaches the peak value. Then, fix the antenna at the local end.
NOTE
When you tighten the antenna, ensure that VBNC remains the peak value.
Step 4 Repeat Step 2 to Step 3 to adjust the antenna at the remote end. When VBNC reaches the peak value, tighten the antenna at the remote end.
Step 5 Repeat Step 2 to Step 4 for two to four times. When VBNC at the local end and VBNC at the remote end reach the peak value, tighten the antennas at both ends
Step 6 Use the multimeter to test VBNC at both ends. Obtain current RSL by referring to the relation curve between VBNC of ODUs and RSLs at both ends.
NOTE
The curve diagram of VBNC and RSL is delivered in the carton of the ODU.
Actual RSL must be the same as planned by the network planning department.
NOTE
l If VBNC does not meet the requirements, see the OptiX RTN 620 Radio Transmission System Maintenance Guide for handling the fault.
Step 7 Observe the ODU indicator on the IF board. If the ODU indicator blinks yellow, align the antennas.
Step 8 Tighten all the screws of the antennas.
NOTE
Use the multimeter to check the received value of RSSI. Avoid any fault in the alignment of antennas in the process of tightening the screws.
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4.5.3 Aligning Dual-Polarized Antennas
When you align dual-polarized antennas, you need to align the main lobe of the antenna signals by adjusting the azimuth and elevation of the antennas at both ends. You also need to adjust the feed booms of the antennas so that the cross-polarization discrimination (XPD) meets the specified requirements.
Prerequisite
l The NE commissioning of the radio equipment at both ends of the radio link must be complete.
l The weather must be suitable for outdoor work. There should be no rain, snow or fog between stations.
l The on-site conditions must meet the requirements for the antenna to operate at a high altitude and the personnel required to commission the antenna must be trained to work at high altitudes
l The ATPC function must be disabled (the default status on the NE is Disabled).
l The AM function must be disabled (the default status on the NE is Disabled).
Tools, Equipment, and Materials
l Adjustable wrench
l Telescope, interphone, and socket-head wrench
l Multimeter (with a BNC connecter prepared at one end for future tests), and north-stabilized indicator.
Procedure
Step 1 Power off the vertically polarized ODUs at both ends of the radio link, power on the horizontally polarized ODUs at both ends of the radio link, and thus ensure that the antennas transmit horizontally polarized signals.
Step 2 Adjust the azimuth angle and elevation angle of the antennas at both ends by referring to 4.5.2 Aligning Single-Polarized Antennas, and ensure that the main lobe of the horizontally polarized signals is aligned with the antenna.
Step 3 Measure the RSL (P1) of the horizontally polarized signals at the local end.
1. Use a multimeter to measure the signal level on the RSSI port of the horizontally polarized ODU.
2. Calculate the RSL (P1) of the horizontally polarized received signals by referring to the curve diagram in the ODU box.
Step 4 Adjust the feed boom at the local end, and ensure that the RSL of the vertically polarized signals reaches the lower threshold (P2).
1. Power on the vertically polarized ODU at the local end.
2. Use a multimeter to measure the signal level on the RSSI port of the vertically polarized ODU.
3. Calculate the RSL (P2) of the vertically polarized signals by referring to the curve diagram in the ODU box.
4. Calculate the XPD1 (XPD1 = P1 - P2).
If... Then...
The calculated XPD1 (XPD1 = P1 - P2) should not be less than 30 dB.
Proceed to the next step.
The calculated XPD1 (XPD1 = P1 - P2) should not be less than 30 dB.
Perform Step 5.
5. Release the holder of the feed boom to some extent, and turn the feed boom slightly until the signal level reaches the lower threshold. The calculated XPD1 (XPD1 = P1 - P2) should not be less than 30 dB.
Step 5 Record the angle (D1) of the current feed boom.
Step 6 Power off the horizontally polarized ODUs at both ends of the radio link, power on the vertically polarized ODUs at both ends of the radio link, and thus ensure that the antennas transmit vertically polarized signals.
Step 7 Measure the RSL (P3) of the vertically polarized signals at the local end by referring to Step 3.
Step 8 Adjust the feed boom at the local end, and ensure that the RSL of the vertically polarized signals reaches the lower threshold (P4).
1. Power on the vertically polarized ODU at the local end.
2. Use a multimeter to measure the signal level on the RSSI port of the vertically polarized ODU.
3. Calculate the RSL (P4) of the vertically polarized signals by referring to the curve diagram in the ODU box.
4. Calculate the XPD2 (XPD2 = P3 - P4).
If... Then...
The calculated XPD2 (XPD2 = P3 - P4) should not be less than 30 dB.
Proceed to the next step.
The calculated XPD2 (XPD2 = P3 - P4) should not be less than 30 dB.
Perform Step 9.
5. Release the holder of the feed boom to some extent, and turn the feed boom slightly until the signal level reaches the lower threshold. The calculated XPD2 (XPD2 = P3 - P4) should not be less than 30 dB.
Step 9 Record the angle (D2) of the current feed boom.
Step 10 Adjust the feed boom slightly (ranging from D1 to D2), and ensure that XPD1 and XPD2 are not less than 30 dB.
NOTE
If D1 and D2 are the same, you need not adjust the feed boom.
Step 11 Tighten all the screws of the antennas.
NOTE
Use the multimeter to measure the received value of RSSI. Avoid any fault in the alignment of antennas in the process of tightening the screws.
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