F400 ePTP link drops Reason: 53 (AP KEEP ALIVE RX STUCK)

So this link ran great at 40Mhz ePTP for a year or so, just perfect, not even a hiccup.

Had to bump it up to 80Mhz and it just started dropping with no reason given. Then upgraded firmware and seemed to be good again but lots of odd errors in logs. Support gives me beta software RC9 to try and errors still there but now DFS hits, DFS hits over and over…

So go back to 40Mhz channel , still running 5.4.1RC9 and it seemed fine for a few hours then started dropping the link every few minutes with

F=5620 11axahe40plus. Reason: 53 (AP KEEP ALIVE RX STUCK)

(oh and the occasional DFS thrown in the mix too).

So I looked and I see lots of posts with the keep alive stuck error but so far the only one I found with a possible solution was one person that changed from ePTP to TDD. However F400 doesn’t have TDD.

Anyone else seeing this on F400 and found a solution ?

I’ve seen the Reason: 53 (AP KEEP ALIVE RX STUCK) issue on a handful of F400 links. I’ve assumed that it is transient noise causing the issue, but on one particular link that was having a lot of this, I replaced the radios with AF5xHD and haven’t had a single issue or seen any evidence of noise.

I replaced all of our 3000L PTP with AF5xHD and they have been absolutely bullet proof. This is (and probably will be) the last of my Cambium PTP links, it replaced a PTP550 that was terribly unreliable and I was really happy / impressed with it for a year but that honeymoon is over.

It’s a short link, just under 1.5km and we have a couple of really really short AF60-LR links that are also bullet proof. According to Ubiquiti’s link planner the link should have 100% uptime, even in torrential downpours… Ubiquiti is bad to fudge their numbers but I think I’m going to find out how reliable AF60-LR is at 1.5km

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At 1.5km an AF60-LR will be rock solid, except maybe if it gets iced over or packed with wet snow.

Got a set of Jirous radomes for them so hopefully no snow/ice accumulation issues.