i used atheros 5211 with routerOS 2.8.11 and connect to atheros 5213 with routerOS 2.8.26
Using band 5 Ghz. The distance between those two radio are 7 km.
basic-rates-a/g=6Mbps,9Mbps for the two site.
When i used the bandwidth-test, i have total traffic up/down around 6Mbps.
The ping between those two are ok. Around 20 ms.
But the problem begin when i connect those two site with real traffic, which has traffic arround 4 Mbps. The ping are increase until 200 ms.
What is the problem ? It's only 4 Mbps traffic, still under 6 Mbps.

I have the same problem conecting 5212 and 5211 on 2.5 Mbps have huge pings .
Very greatfull in a solution .

The basic rate is used for link maintenance -- set it back to 6Mb/s and then leave the supported rates to all of the rates.

Or reset the entire config and start ove.

John

Set data rates max of 12 or 18mbps, and leave basic rates 6mbps as tully said.