I've got an AP built from a p3 class machine, using SR5, SR2, and Senao 2511MP cards in RB11 PCI adapters. The 2511mp is a point to point "feed", the SR5 is a point to point "feed", and the SR2 is broadcast, connected via 10ft RG8 to a Pac Wireless 13dBi h-pol omni.
Until about two weeks ago, everything was working fine, but at some point things started going awry. We had made no changes to the AP, other than hooking up a local ethernet line to the LAN port of the machine. We noticed this problem about a week later, but cannot correlate if it started when that line was hooked up.
The behavior is that close stations (less than 3km) have reasonable signal strength (anywhere from -55 to -70), but have very poor CCQ (5-15%) and obviously poor performance due to the poor ccq.
We've tried many things to fix this such as changing out pigtails (both ufl and mmcx), different channels, static vs dynamic ack timout values, and nothing seemed to help to any significant degree.
However, as I was typing this my field tech replaced the SR2 with an R52H and now stations which had 9% have 100%!!
So, I'm going to finish this post, just to share the information.
Low CCQ on close connections with Ubiquity SR2, we fixed it by replacing the SR2 with a Mikrotik R52H.