HalTech ICT Solution

MICROWAVE (MW) LINK ALIGNMENT

1. WHAT IS MW LINK ALIGNMENT?
Microwave link alignment means accurately pointing two microwave antennas toward each other so that the radio link can receive the best possible signal.

A good alignment gives:
- Strong RSL
- Stable modulation
- Better throughput
- Low packet loss
- Low BER
- Better fade margin
- Stable link during rain or bad weather

2. MAIN PURPOSE OF MW ALIGNMENT
- To achieve maximum received signal level
- To keep the link stable
- To improve capacity
- To reduce interference impact
- To maintain high modulation
- To reduce link down issues
- To improve network availability

3. REQUIRED TOOLS
Basic tools:
- Compass
- GPS or mobile GPS app
- Laptop
- Ethernet cable
- Radio software or web login
- Binoculars
- Spanner set
- Site document
- Walkie-talkie or phone communication

Safety tools:
- Safety helmet
- Full body harness
- Double lanyard
- Safety shoes
- Gloves

4. IMPORTANT PARAMETERS
RSL:
Received Signal Level. It shows how strong the received signal is.

SNR:
Signal to Noise Ratio. Higher SNR gives better modulation and stable link.

BER:
Bit Error Rate. Lower BER is better.

TX Power:
Transmit power from radio.

RX Power:
Received power from remote radio.

Modulation:
Capacity level of the link. Example: QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 2048QAM.

Fade Margin:
Extra signal reserve for rain, fog, humidity, and other fading conditions.

Frequency:
Operating frequency of the MW link.

Polarization:
Vertical or horizontal signal orientation.

5. TYPES OF ALIGNMENT
A. Coarse Alignment:
Initial pointing of antenna using azimuth, compass, GPS, and visual direction.

B. Fine Alignment:
Small movement of antenna to get the best RSL and stable link performance.

6. BEFORE ALIGNMENT CHECKLIST
Check these before starting:
- Correct site name
- Correct remote site
- Correct azimuth
- Correct antenna height
- Correct antenna size
- Correct frequency
- Correct TX/RX frequency pair
- Correct polarization
- ODU installed properly
- IDU or modem powered on
- Ethernet or management access working
- Grounding completed
- No LOS obstruction
- Weather condition is safe
- Tower climbing permission is available

7. STEP-BY-STEP ALIGNMENT PROCESS

Step 1: Verify site data
Check:
- Site A coordinates
- Site B coordinates
- Link distance
- Azimuth
- Antenna height
- Frequency plan
- Antenna size
- Polarization

Step 2: Install antenna properly
Make sure:
- Antenna is mounted tightly
- Bracket is not loose
- ODU is fixed correctly
- Polarization is correct
- Grounding cable is connected
- IF/RF cable is connected properly

Step 3: Set approximate direction
Use:
- Compass
- GPS
- Azimuth value
- Remote tower direction

Point the antenna approximately toward the remote site.

Step 4: Coordinate with remote team
Both sides should communicate by phone or walkie-talkie.

One engineer should move the antenna.
Another engineer should monitor:
- RSL
- Modulation
- Link status
- Alarm status

Step 5: Horizontal alignment
Slowly move antenna left and right.

Watch RSL carefully.

Example:
- If RSL improves from -70 dBm to -60 dBm, continue moving slowly.
- If RSL improves to -48 dBm, stop near the best point.
- If RSL starts dropping again, move back slightly.

Step 6: Vertical alignment
Slowly move antenna up and down.

Find the best RSL point.

Step 7: Fine tuning
Move antenna very slowly in small steps:
- Left
- Right
- Up
- Down

Find the peak signal level.

Step 8: Tighten bolts carefully
Tighten all bolts slowly.

Important:
- Do not move antenna while tightening.
- Tighten both sides gradually.
- Check RSL again after tightening.

Step 9: Final verification
Confirm:
- RSL is stable
- Modulation is stable
- BER is clean
- No alarm
- Traffic is passing
- Link capacity is correct

8. GOOD ALIGNMENT TARGET
A good alignment should have:
- Strong RSL
- Stable SNR
- High modulation
- No major BER
- No LOS obstruction
- Good fade margin
- Stable traffic

9. EXAMPLE TARGET RSL
Example only:

Link distance: 7 km
Frequency: 18 GHz
Antenna size: 0.6 m
Expected RSL: around -40 dBm to -50 dBm

If actual RSL is much weaker, such as -65 dBm or -70 dBm, possible reasons:
- Wrong alignment
- Wrong antenna direction
- LOS blocked
- Wrong polarization
- Low TX power
- Cable loss
- Frequency mismatch
- Hardware issue

10. COMMON PROBLEMS AND SOLUTIONS

Problem: No signal
Possible causes:
- Wrong azimuth
- Wrong frequency
- Wrong polarization
- Remote radio is off
- Cable issue
- ODU fault

Solution:
- Recheck azimuth
- Check frequency pair
- Check polarization
- Confirm remote power
- Check cable and connector
- Check ODU status

Problem: Weak RSL
Possible causes:
- Poor alignment
- Obstruction
- Wrong antenna size
- Low TX power
- Loose bracket

Solution:
- Fine tune antenna
- Check LOS
- Verify antenna size
- Check TX power
- Tighten mounting bracket

Problem: RSL fluctuating
Possible causes:
- Loose antenna
- Loose pole
- Bad connector
- Weather fading
- Interference

Solution:
- Tighten antenna and pole
- Check connector
- Check grounding
- Monitor during clear weather
- Check frequency interference

Problem: Link down during rain
Possible causes:
- Low fade margin
- Poor alignment
- High frequency link affected by rain
- Small antenna size

Solution:
- Improve alignment
- Increase antenna size if required
- Reduce link distance if possible
- Check fade margin
- Optimize frequency planning

Problem: High BER
Possible causes:
- Interference
- Weak signal
- Bad cable
- Poor SNR
- Hardware issue

Solution:
- Check spectrum/interference
- Improve RSL
- Replace faulty cable
- Check SNR
- Check radio hardware

11. POLARIZATION CHECK
MW antennas commonly use:
- Vertical polarization
- Horizontal polarization

If polarization is wrong:
- Link may not come up
- RSL may be very weak
- XPIC may fail
- BER may increase

Always match local and remote polarization correctly.

12. LOS CHECK
LOS means Line of Sight.

Clear LOS is required between two antennas.

Avoid:
- Buildings
- Trees
- Hills
- Tower steel obstruction
- Water tank
- Roof edge
- Nearby wall
- Signboard

Even partial blockage can reduce signal quality.

13. FRESNEL ZONE
Fresnel zone is the invisible RF clearance area around the direct path.

Even if visual LOS is clear, the Fresnel zone may be blocked.

Fresnel blockage can cause:
- Weak RSL
- Poor SNR
- Link instability
- Rain fade problem
- Throughput drop

14. FADE MARGIN
Fade margin means extra signal strength available above the minimum required level.

Higher fade margin gives better link stability.

Good fade margin helps during:
- Heavy rain
- Fog
- Humidity
- Atmospheric fading

Typical good fade margin:
- 20 dB to 35 dB or more, depending on link design

15. ALIGNMENT BEST PRACTICES
- Move antenna very slowly
- Do not rush alignment
- Always monitor live RSL
- Communicate clearly with remote team
- First do horizontal alignment
- Then do vertical alignment
- Repeat fine tuning until peak signal
- Tighten bolts carefully
- Check RSL after tightening
- Take screenshot of final parameters
- Keep record of final RSL and modulation

16. FIELD ENGINEER TIPS
- Never depend only on compass
- Use azimuth and visual direction together
- Check remote site height and direction
- In long distance links, small movement creates big signal change
- For high frequency links, alignment must be very accurate
- E-band links need more precise alignment
- Check if antenna is installed behind wall edge or obstruction
- Avoid alignment during heavy wind
- Do not climb during lightning or storm

17. FINAL ACCEPTANCE CHECKLIST
After alignment, confirm:

- Link is up
- RSL is as per link budget
- SNR is good
- Modulation is stable
- Capacity is correct
- BER is normal
- No critical alarm
- No packet loss
- Traffic passing successfully
- Antenna bolts are tight
- Grounding is completed
- Weatherproofing is done
- Final screenshot taken
- Site photo taken

18. SIMPLE FIELD EXAMPLE
Site A to Site B MW Link

Distance: 5 km
Frequency: 15 GHz
Antenna size: 0.6 m
Polarization: Vertical
Target RSL: -45 dBm

During alignment:
- Initial RSL: -78 dBm
- After horizontal adjustment: -58 dBm
- After vertical adjustment: -48 dBm
- After fine tuning: -44 dBm

Final result:
- RSL: -44 dBm
- Modulation: Stable
- BER: Normal
- Link: Up
- Traffic: Passing

19. SAFETY WARNING
Tower work is dangerous.

Always use:
- Helmet
- Harness
- Safety shoes
- Gloves
- Double lanyard

Do not work during:
- Heavy rain
- Strong wind
- Lightning
- Unsafe tower condition

Safety first, alignment second.

20. CONCLUSION
MW link alignment is one of the most important tasks in telecom transmission.

Proper alignment gives:
- Strong signal
- Better link capacity
- Stable network
- Less packet loss
- Better customer experience
- Higher link availability

A small alignment mistake can create big problems, especially for long distance, high frequency, and high capacity microwave links.
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