Near-Far Test
Cleaned Lesson Transcript / Study Notes
The next test is the Near-Far Test.
This test verifies whether the BDA/DAS system has sufficient antenna density and gain control performance to support radio users in different locations inside the building.
1. Purpose of the Near-Far Test
The Near-Far Test checks what happens when a radio close to an antenna drives the BDA into saturation.
When a near radio keys up very close to an antenna, it can cause the BDA to engage:
- AGC — Automatic Gain Control
- ALC — Automatic Level Control
When this happens, the BDA reduces gain to protect itself from being overdriven.
The purpose of the test is to confirm that, while the near radio is causing gain reduction, another radio farther away can still transmit through the BDA and reach the donor site with enough power.
2. Near Radio Condition
Start by keying up the near channel.
The near radio represents the strongest signal condition the BDA should see from inside the building.
From the configuration, the test radio is used to create the near-radio condition.
The CW generator is then used to replicate that near-radio signal during the test.
The setup should include compensation for any attenuation in the test path.
The test also pulls in information from the previous Uplink Power and Gain test.
3. Select the Test Point
Select the appropriate test point for the near-radio condition.
This test point represents the “hottest” or strongest expected signal input into the BDA.
Add the near-radio measurement to the report.
The software will indicate what signal level must be generated by the CW generator to replicate the near-radio condition.
In this example, the required generated signal is approximately:
20 dBm
A slightly stronger signal may be acceptable to ensure the near-radio condition is fully represented.
4. Key the Far Radio
Once the signal generator is running and replicating the near-radio condition, key the far radio.
The far radio represents a weaker signal condition from farther away in the building.
The test determines whether the far radio can still reach the donor site while the BDA is already being driven by the near-radio condition.
Add the far-radio result to the report.
5. Review the Results
After the near and far measurements are added to the report, review the pass/fail criteria.
The test checks whether the far radio still meets the required target power output while the near-radio signal is causing AGC or ALC activity.
In this example, the system meets the criteria.
The far radio is still able to achieve the required target power output.
Final Result
The Near-Far Test confirms that the BDA can support a strong near-radio signal without preventing a far radio from reaching the donor site.
This test documents:
- Near-radio condition
- Far-radio condition
- Test frequency or filter
- Attenuation compensation
- Previous uplink power and gain data
- CW generator level
- AGC/ALC impact
- Target power output
- Pass/fail result
In this example, the system passes because the far radio still meets the required target power output while the near-radio condition is present.