PTP820S getting stuck on lowest MRMC rate

We have many PTP820S links, in various frequency plans. All running at least FW 11.7, some 12.0, some 12.1, all running adaptive profiles enabled, Adaptive power disabled. We are seeing several links having issues where one end of a link will throttle down to the lowest profile rate (4 QAM), and stay locked there. This happens, typically, after a power failure, or weather fade. The modem MSE will be very degraded (< -14). After one or more reboots, eventually the link will come back to the correct modulation profile, with MSE back to > -40, and will stay there until the next link fade/fail. We even see this during new path build-out / alignment. Signal strength will be as predicted, but the MSE will be poor. A reboot (or more) will correct this and path will meet or exceed the design. Great radios, just an odd problem. Anyone else having similar issues, experience?

Curious why you run with “Adaptive power disabled”… we’re the opposite, we have it enabled for every link, and from what I understand, is the preferred state. We have many PTP8X0 links as well and have not experienced the issue you’re reporting. All of our radios are on firmware release 12.

Cambium has told us, several times, not to run ATPC, unless short hops, where power needs to be reduced. Running both ATPC and the adaptive profile, confuses the radio. That being said, we do see the power changing / profile. This seems to be a FW issue, as the receiver sees the MSE and very low, and chooses the low profile to keep the link up, and power for 4 QAM is max value.

Yeah, ATPC and adaptive power are two different things… and yes, you are correct in that you don’t want to run both at the same time (at least in certain instances, like you said, unless it’s for short “hot” hops). Again, we run adaptive power (and NOT ATPC) on every link.

Most times MCS is lowered because of noise; might be worth investigating that

I’d accept noise, interference, for an answer, if a reboot didn’t resolve the problem. Intermittent noise, would clear itself, not disappear when radio is rebooted. This is a FW and/or HW issue where the link fails, the receiver gets noisy, due to signal fade, or power fail, and when the path is re-established, the receiver still sees the “faded” signal (MSE <12), reboot puts MSE back to >40. Also, these are across several paths, different locations, some urban, some rural, different band plans.

We have two more hops, showing the same MSE degradation, different band plans, geographic diverse. Forcing reboot(s) eventually clears the problem. I’m struggling to believe no one else is having similar problems. It’s statistically unlikely, so many of these licensed, coordinated, links, could all be experiencing interference, that radio rebooting solves …

At this point I’d probably discuss this with your Cambium RTM and then if this is happening frequently enough, try to catch it in the act and have the RTM go through the configuration with you along with opening up a support ticket with Cambium.