how to configure right wireless part of that device because wifi speed really low up ti 15 mbits to 802.11n close to ap …
in internet speed 100 mbit wifi max 15 lan part don’t tryed yet…
In my experience RouterOS doesn’t perform well out of the box in ordinary 802.11n mode with laptops and other non MTik devices.. I would like too to hear some short stories how to utilize full 11n speeds without endless tweaking. I did see a lot of activity in the forum for this topic, but since it wasn’t actual for me then, I didn’t follow. And perhaps that’s why cheap TP-Link router now downloads at least twice as fast as my 751GA-2HnD 
The RB751’s have a lot more RF power than a budget AP. 26dBm compared to only 17dBm in many cases.
Testing on the bench close to the AP can give poor results as the test device is “swamped” with signal.
The only real tweak is to ensure both HT chains are enabled and only use AES ciphers when you enable WPA/WPA2 PSK.
These are now defaults in the latest FW so it should be ok.
I have latest firmware WPA2 AES …
what antenna should i choose
periodically CPU 100% due to flash it can be?
I use the default internal ones at my office and it is giving me good internal coverage within the building. (about 200 m2).
I get OK outside coverage too.