Mikrotik wAP_ac low throughput in 5ghz

Hi,

I´m testing my RB wAP ac, and after several tests i detected my tthroughput is very lower.
The RB is connected to a cisco router, and via ethernet cable directly on Cisco
my throughput is 85Mpbs. If i connect through the AP on 5Ghz, my throughput is about 20Mbps.

There is a possible configuration adjustment?

Thanks in advanced

Regards

what client are you using to test? are you running in 802.11ac mode or 802.11a mode?

The test is running under 802.11ac mode, and i use a several clients.. iphones, desktops,.. mac… everyone as ythe same problem.
Thanks

Not enough information to work with. paste your wireless config for that interface, use command line /wireless export command and delete/replace all sensitive information