# Frequent SM disconnects - 3ghz 450b to 450i
**URL:** https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752
**Category:** PMP
**Created:** [August 21, 2026, 8:34pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752 "2026-08-21T20:34:25Z")
**Posts on this page:** 14
**Page:** 1
### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 21, 2026, 8:34pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/1 "2026-08-21T20:34:25Z")
Latest firmware on both the AP and the SM. Distance is 1.3 miles. Not LOS, but pretty close. AP is 450i with 60 degree panel antenna.
Customer complains of losing connection. It does, in fact drop connection, seems to be randomly. I would say its b/c of not a very strong signal, but I have others on this same AP with weaker signals that this does not happen to. I have changed everything out there, POE and radio, still happens.
What should I check? Very frustrating.
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### Author:  [@Eric\_Ozrelic](https://community.cambiumnetworks.com/u/Eric_Ozrelic)
#### Post date: [August 22, 2026, 7:24pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/2 "2026-08-22T19:24:59Z")
Does your AP have sync? Have you tried enabling LTE coexistence settings? Have you updated to firmware release 25.1?
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### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 24, 2026, 5:35pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/3 "2026-08-24T17:35:57Z")
Yes it is externally synced. Yes, I have the LTE coexistance settings in the AP. Yes, I am running 25.1 on both.
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### Author:  [@Jacob\_Turner](https://community.cambiumnetworks.com/u/Jacob_Turner)
#### Post date: [August 24, 2026, 6:19pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/4 "2026-08-24T18:19:37Z")
Have you looked at the modulation rates chart in cnMaestro for the radio that is dropping? I would venture a guess that rates are falling before it drops it’s registration. In my experience this is almost always caused either by noise/interference on the SM side or bad multipath/reflections due to LOS issues. It is sometimes a bad POE adapter or poor cable termination, but it looks like you have ruled that out.
Also, if it drops regularly enough and it is rate-related, you should be able to watch it happen if you are logged into the AP and monitoring sessions → power.
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### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 24, 2026, 8:34pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/5 "2026-08-24T20:34:22Z")
No, I have not checked the mod rates on it. I will check into it. One question though: This SM was moved from another location to the current customers home. The GPS coordinates in CNM were never updated, so the coordinates were off by like a mile. Would that in any way cause this?
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### Author:  [@Jacob\_Turner](https://community.cambiumnetworks.com/u/Jacob_Turner)
#### Post date: [August 24, 2026, 8:46pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/6 "2026-08-24T20:46:34Z")
Unless the SM is losing it grant or something, no. You can see if it is loosing it’s grant both in cnMaestro and the radio cbrs logs.
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### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 24, 2026, 9:00pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/7 "2026-08-24T21:00:46Z")
Not seeing anything related to grant loss in the logs, however, here is a log snippet from the SM:
08/24/2026 : 15:31:03 CDT : : Not received PONG for the last ping (3)
08/24/2026 : 15:31:22 CDT : : Not received PONG for the last ping (4)
08/24/2026 : 15:31:52 CDT : : Not received PONG for the last ping (5)
08/24/2026 : 15:31:52 CDT : : Missed 5 consecutive PONGS, disconnecting with server
08/24/2026 : 15:31:52 CDT : : Sending close frame now reason=[DEV\_PING\_TIMEOUT]
08/24/2026 : 15:31:52 CDT : : callback\_websocket: LWS\_CALLBACK\_CLOSED
08/24/2026 : 15:31:52 CDT : : Attempting (re)connection in 5 seconds
08/24/2026 : 15:32:22 CDT : : Connection in progress timed out with error Invalid argument.
08/24/2026 : 15:32:22 CDT : : OpenConnection to [cloud.cambiumnetworks.com:443](http://cloud.cambiumnetworks.com:443) failed
08/24/2026 : 15:32:22 CDT : : Not able to get cloud details, can’t proceed
08/24/2026 : 15:32:22 CDT : : Unable to discover cnMaestro URL (re-discover in 354 seconds)
08/24/2026 : 15:32:22 CDT : : Attempting (re)connection in 5 minutes
08/24/2026 : 15:33:24 CDT : : Attempting (re)connection in 5 seconds
08/24/2026 : 15:33:25 CDT : : Attempting (re)connection in 5 seconds
08/24/2026 : 15:33:47 CDT : : platform\_set\_fld\_index: Failed to get index for field [EIRP\_Active]
08/24/2026 : 15:33:47 CDT : : Invalid field [EIRP\_Active], please check
08/24/2026 : 15:33:57 CDT : : platform\_set\_fld\_index: Failed to get index for field [EIRP\_Active]
08/24/2026 : 15:33:57 CDT : : Invalid field [EIRP\_Active], please check
What does this mean?
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### Author:  [@Jacob\_Turner](https://community.cambiumnetworks.com/u/Jacob_Turner)
#### Post date: [August 24, 2026, 9:14pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/8 "2026-08-24T21:14:27Z")
All that means is that the SM lost it’s connection to the internet and couldn’t communicate with cnmaestro.
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### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 25, 2026, 8:36pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/9 "2026-08-25T20:36:44Z")
Thank you for telling me that. The SM just disconnected again, and then reconnected. Is there anything I should look for in the logs of the AP or SM to try to find out why/what is causing this? Everything is rather cryptic, not sure what to look for.
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### Author:  [@Cambium\_Lena](https://community.cambiumnetworks.com/u/Cambium_Lena)
#### Post date: [August 26, 2026, 11:33am UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/10 "2026-08-26T11:33:33Z")
Could you help open a support ticket for us to check further?
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### Author:  [@jakkwb](https://community.cambiumnetworks.com/u/jakkwb)
#### Post date: [August 26, 2026, 4:38pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/11 "2026-08-26T16:38:37Z")
certainly. Will do so today
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### Author:  [@anthonyw](https://community.cambiumnetworks.com/u/anthonyw)
#### Post date: [August 26, 2026, 10:32pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/12 "2026-08-26T22:32:52Z")
Isn’t 450i a P12 hardware? v25+ is not compatible. v24.2.2 is the last firmware compatible with P12 hardware.
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### Author:  [@Jacob\_Turner](https://community.cambiumnetworks.com/u/Jacob_Turner)
#### Post date: [August 27, 2026, 1:18am UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/13 "2026-08-27T01:18:56Z")
450i ap is p13 hardware
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### Author:  [@Eric\_Ozrelic](https://community.cambiumnetworks.com/u/Eric_Ozrelic)
#### Post date: [August 27, 2026, 11:35pm UTC](https://community.cambiumnetworks.com/t/frequent-sm-disconnects-3ghz-450b-to-450i/108752/14 "2026-08-27T23:35:28Z")
It’s a little confusing… but you can run R25 on the original SM’s, it just doesn’t support the full VC queue depth that the 450b/i SM’s support. So you’re stuck with around 60-70mbps even when using a 40MHz channel width.