4500L TDD PTP Radio Issues - No TX at all

Products ePMP
1

Hello

Just wondering if anyone else has had 4500L radios loose the ability to TX randomly when in TDD PTP mode?

I have a link between two tower sites. At site A, we have a 4500L in TDD PTP mode on one side, and at site B we have a Force 400C and it seems like the 400C can no longer see or connect to the 4500L.

For backup, we have another 400C at site B that connects to a different 4500L at site A that is in TDD AP mode with a bunch of clients on it at site A. This AP has been rock solid.

Both Force 400C’s at site B can’t see this 4500L, but can see our other AP’s at Site A.

We have the dedicated PTP for capacity and to get GPS sync with our other APs. For context, we have an additional 2x 4500L AP’s at site A along with a 4500C.

Thinking the failure at Site A was a one-off, I swapped the 4500L radio out and it came back online immediately and worked for about two weeks before failing in the exact same way again.

The last error message I got on the client was this: 2025.08.08 08:43:55 +00:00 SH9-Briar kernel: [2132159.873430] SM disassociated from AP[bc:e6:7c:22:c0:57] F=5735 11axahe40plus. Reason: 33 (GPFs MISS) and I believe the AP rebooted itself when this occurred. I have support files from both.

With the current radio, I have currently tried:

  • Factory Reset
  • Drop to 20Mhz channel width from 40Mhz
  • Standard TDD Mode
  • Disabled GPS Sync
  • WLR Mode
  • 5.10.1 upgraded to 5.10.2-RC8
  • Downgraded both sides to 5.8.0
  • Factory Reset again

I have the original radio on the bench and it is doing the exact same thing, I just find it hard to believe that we have two dead 4500Ls back to back, especially when we currently have two that are on the tower working fantastic.

Any help would be greatly appreciated!

2

Just figured I would post an update, got the 4500L on the bench and I can get it to work, but the signals are extremely weak. I am seeing -77db / -44db between the 4500L and a Force ePMP 4525. I have a gap of around 2 inches between the radios. This at least indicates it’s not an antenna issue.

The 4500L is set to 24db TX power. I also tried 4db and it causes the link to drop out completely. Is there a chance this is a software issue or do I need to RMA both units for a hardware issue?

I have not factory reset this unit just yet, although I have factory reset the one that is deployed in the field a couple of times.

3

Hi Chris,

Do you have the support ticket opened for that issue?
Can you send me the email with Tech Support files attached please?
fedor(dot)trutsko(at)cambiumnetworks.com

Thank you.

4

Hello Fedor

I have sent you the files. I do not have a support ticket opened yet as this seems like a software bug to me rather than a hardware issue.

5

This happened to me as well on a 4500L. I tried all sorts of troubleshooting, as well as a factory reset. We ended up replacing the unit.

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6

Pretty much had the same thing. Waiting on RMA replacement. There was a early batch of 400c with a similar issue also.

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7

Fedor got us replacement units and they have been working fantastic so far, so must have been a bad batch.

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8

Hi @Chris_L ,

thank you for your confirmation!

We precisely monitor our RMA pipeline. We did not find any correlation with a particular batch.

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9

Thanks for the clarification. I am pretty sure these two radios came together on the same order and they came with same very very old firmware so I made an assumption.

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