Monitoring a Repeater Using BPS with a Davicom CORTEX Unit

This guide provides an in-depth explanation of how to monitor a repeater using a Bidirectional Power Sensor (BPS) and a Davicom CORTEX unit (320 or 360 series). It includes everything from physical setup and wiring to configuration and testing, ensuring seamless integration and real-time monitoring of PTT status, forward (FWD) and reflected (REV) power, and VSWR (Voltage Standing Wave Ratio) calculations.

Introduction

Why Monitor Repeaters?

Monitoring repeaters is essential for maintaining the reliability and efficiency of communication systems in industries like broadcasting, public safety, and telecommunications. A properly monitored repeater can help you:

  • Detect failures, such as low power, high VSWR, or no transmission, before they escalate.
  • Ensure compliance with operational thresholds and performance metrics.
  • Facilitate quick troubleshooting and minimize downtime.

How Davicom Enhances Monitoring

Using a Davicom CORTEX unit and BPS sensor allows for:

  • Real-time data visualization.
  • Alarm notifications for critical events.
  • Accurate calculation of VSWR, which reflects antenna system health.

Prerequisites

Hardware Requirements

  1. Repeater:
    • Capable of providing a PTT status signal to indicate when it is transmitting.
  2. Bidirectional Power Sensor (BPS):
    • A model suitable for your power range and frequency. For instance:
      • BPS1050: Ideal for 1–1000W power at frequencies between 30 to 500 MHz.
      • BPS5095: Ideal for 1–1000W power at frequencies between 500 to 950 MHz.
  3. Wattmeter:
    • Used to measure real power for calibration.
  4. Davicom CORTEX Unit:
    • Either Davicom CORTEX 320 or 360, depending on your site requirements.

Documentation

  1. Repeater manual: To locate the PTT qualifier pin and understand its logic.
  2. BPS calibration guide: TB-034r2.
  3. Davicom Knowledge Base: Includes guides on workspaces and general configurations.

Connectivity Tools

  • Necessary cables for wiring the repeater, BPS, and Davicom CORTEX unit. Ideally shielded cables.
  • Screwdriver to adjust the BPS calibration screw during setup.

Physical Installation

1. Locate and Connect the PTT Qualifier Pin

  • Refer to the repeater’s documentation to find the pin responsible for PTT Qualifier/Status.
  • Wire Connection: Connect the PTT qualifier pin to Digital Input 1 (1D1) on the Davicom CORTEX unit.
    • If 1D1 is unavailable, you may use any other digital input, but take note of its ID for configuration.

2. Install the BPS Sensor

  • Place the BPS inline between the repeater and the antenna.
    • Ensure that the BPS is oriented correctly, with the forward (FWD) and reflected (REV) terminals aligned with the signal flow.
  • Temporarily connect a wattmeter to measure forward and reflected power for calibration purposes.

3. Wire the BPS to the Davicom CORTEX

  • Use the following connections:
    • Forward Power: Wire the BPS’s forward power output to Analog Input 1 (1A1 or A1).
    • Reflected Power: Wire the reflected power output to Analog Input 2 (1A2 or A2).
    • Ground: Connect the BPS ground terminal to the Davicom CORTEX ground of both inputs.
Illustrated example with Kenwood NXR-5800

Davicom CORTEX Unit Configuration

The Davicom CORTEX unit requires step-by-step configuration of its inputs and math functions to properly monitor the repeater and its parameters.

Configure the PTT Qualifier

  1. Navigate to Status Inputs:
    • Access Inputs > Status Inputs in the Davicom CORTEX’s web interface.
  2. Create or Edit Input:
    • Add a new input or right-click on 1D1 (if already populated) and choose Configure.
  1. Description Tab:
    • Label the input’s ACTIVE/NORMAL description as PTT Status for easy identification.
  1. Action Tab:
    • Set the Active Level (High or Low) based on the PTT logic of your repeater.
    • Set Action Type to CMD for logical processing.

Configure Forward Power

  1. Navigate to Metering Inputs:
    • Access Inputs > Metering Inputs.
  2. Add New Input:
    • Create a new input and assign it to 1A1.
  3. Description Tab:
    • Set the Active Description to FWD POWER LOW.
    • Set the Normal Description to FWD POWER OK.
  1. Action Tab:
    • In the Qualifier Field, enter 1D1 (PTT status ID). This ensures power readings are only active when the repeater is transmitting.
    • Input the calibration coefficients (A, B, and C) for the specific BPS model and frequency:
      • Example for BPS1050 at 170 MHz (100–200W):
        • A = 8.9053, B = 4.4987, C = 0.
    • Set Alarm Thresholds:
      • Configure thresholds for low/high power alarms, e.g.:
        • Low Alarm: Below 90W.
        • High Alarm: Above 220W.
      • Assign Alarm Call Lists for notification with the “Action Type” dropdown menu.
    • Optionally, configure MAJOR/MINOR thresholds for more nuanced alarms.
  • Calibrate Forward Power:
  • Prepare for Calibration:
    • Temporarily insert a wattmeter inline between the repeater and the antenna.
    • Ensure the BPS is properly wired, with forward power connected to 1A1.
  • Verify Initial Readings:
    • Compare the forward power reading on the wattmeter with the real-time reading displayed in the Davicom CORTEX interface.
  • Adjust the FWD Adjustment Screw:
    • Locate the FWD adjustment screw on top of the BPS sensor.
      • Turn Left: Decreases the power reading on the Davicom CORTEX.Turn Right: Increases the power reading on the Davicom CORTEX.
    • Use a screwdriver to make precise adjustments.
  • Align Readings:
    • Continue adjusting until the forward power reading on the Davicom CORTEX matches the actual wattmeter value.
  • Finalize Calibration:
    • Remove the wattmeter to return to normal operation.
    • Verify the Davicom CORTEX’s real-time reading remains accurate during transmission.

Configure Reflected Power

  1. Repeat the same steps as for Forward Power but assign the input to 1A2.
  2. Skip configuring alarm thresholds if you plan to rely on VSWR for reflected power monitoring.

Configure VSWR Calculation

  1. Navigate to Math Functions:
    • Access Inputs > Math Functions.
  2. Add a New Math Function:
    • Select an available slot (e.g., 1F1).
  1. Operator Setup:
    • Set the operator to SWR.
    • Enter the metering IDs:
      • Field A (Reflected Power): Enter 1A2.
      • Field B (Forward Power): Enter 1A1.
  1. Description:
    • Label the function as VSWR HIGH/VSWR OK.
  1. Save:
    • Save the configuration to activate automatic VSWR calculation.

Workspace Setup for Real-Time Display

  1. Access Workspace Edit Mode:
    • Navigate to the Workspace menu.
  2. Assign Meters:
    • Reassign an available meter to display 1F1 (VSWR Calculation).
    • Verify that the workspace updates with real-time VSWR readings.

Testing and Calibration

Verify PTT Status

  • Check that the PTT status activates when the repeater begins transmitting.
  • Ensure that the status indicator changes appropriately (e.g., from inactive color orange to active).

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Test Forward and Reflected Power

  1. Verify the power readings during transmission:
    • Ensure that forward power matches expected values.
    • Check that reflected power is minimal under normal conditions.
  2. Adjust BPS screws if needed to align readings with the wattmeter.

Simulate Fault Conditions

  1. Disconnect the antenna or create a mismatch to simulate high VSWR.
  2. Confirm that:
    • The VSWR calculation accurately reflects the fault condition.
    • Alarms trigger appropriately for any thresholds exceeded.

Troubleshooting Tips

  • PTT Status Does Not Activate:
    • Recheck wiring between the repeater and the Davicom CORTEX.
    • Confirm the PTT qualifier pin and input logic level.
  • Incorrect Power Readings:
    • Verify BPS calibration coefficients.
    • Ensure all wiring is secure and connections are correct.
    • Recalibrate using the wattmeter if discrepancies persist.
  • VSWR Calculation Incorrect:
    • Double-check the math function configuration, especially the assigned metering IDs.

Additional Notes

Why Use Alarms for Power and VSWR?

Configuring alarms ensures that any deviation in system performance (e.g., low power, high VSWR) is immediately reported. This proactive monitoring can prevent damage to equipment and minimize downtime.

How to Further Optimize Monitoring?

  • Utilize Davicom’s workspace customization options to display additional metrics such as site temperature, RF signal strength, or battery voltage.
  • Integrate the Davicom CORTEX with your SNMP network for centralized monitoring.

Conclusion

By following this comprehensive guide, you have successfully:

  • Installed the BPS sensor and configured the Davicom CORTEX unit.
  • Set up PTT, FWD/REV power monitoring, and VSWR calculation.
  • Enabled real-time monitoring and alarm systems.

This robust setup ensures your repeater operates efficiently, with immediate fault detection and prevention capabilities.

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