Did you know that the PTP 820 has an RF Loopback?

RF Loopback is under Radio, Diagnostics, Loopback

RF Loopback is quite intrusive—expect the link to go down during this test!

RF Loopback allows you to test one radio at a time—mute all of the other radios that you’re not testing. (Be sure to mute the far end radio as well!)

RF Loopback provides 60-70 dB of attenuation, good MSE, and zero defective blocks.

Select a fixed modulation mode, disable Adaptive Tx power admin, and set the Tx power to maximum.

Under Radio, Diagnostics, Loopback, turn “On” RF Loopback, and observe the following:

  • Go to Radio, Radio Parameters
  • The RX Level should be 60-70 dB less than the Operational TX Level
    • For example, if the TX Level is 22 dBm, the RX Level should be -38 to -48 dBm
  • MSE at -40 dB or lower
  • Zero defective blocks

If the radio doesn’t pass this test, consider replacing the hardware! (You might have a bad transmitter or receiver.)

Note that you can also select IF loopback for PTP 820G to test the IF cable up the tower.

Use in good health!


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We are troubleshooting a PTP 820S link remotely.  I turned on the loopback to test.  Since starting the test I can no longer communicate with the radio.  We only have one cable connected to the radio using the POE/ETH port.  It appears the Ethernet port shut down?  Any ideas on how to stop the loopback test without physically going to the radio location?

That is not normal behavior and may indicate a larger problem.  The RF loopback has a configurable timer operation and should resume normal operation after the configured loopback time expires (it also shouldn't lock you out of the radio).  Unless you have a way to remotely reboot the radio I think an onsite visit is needed, unfortunately.

A typical time limit of 3-5 min should be sufficient to enable the loopback, monitor the statistics and diagnose.  The radio will resume normal operation after the timer expires (except in this case, it appears).  I would contact our support group and open a ticket.

If it does come back, I would consider upgrading the firmware to 10.5 (latest at time of this post).  Read the release notes first to ensure single upgrade capability.