On http://routerboard.com/R52NM there is a written that these cards have 23dB, but in routeros only i see is 18dB. Version is 5.6 on RB800 firmware 2.30. Setting are "station", "5GHz-a", "manual txpower",... How to get those 23dB. Should I input it manually in TX power tab? I have obtained 8 of those cards to replace CM9, but what to do with the power?

This post might help;
http://forum.mikrotik.com/viewtopic.php ... et#p263824

Also have you 0 in antenna gain in wireless

So, everything is normal and working as it should even the winbox is reporting only 18dB?

if you open up the specifications of this card (PDF in the link you posted), you will see:

802.11g || 6Mbit || -95 || 23dBm

so, this level of tx power will only be possible in 802.11g, at 6Mbit datarate.

It's not working for me. Here is the screenshot from 2GHz-onlyG

like it says "composite power", you need to connect the second antenna and enable the second chain. then you will see 23. it will work in wireless diversity mode. you can use the second antenna in other polarization, or the same. depends on circumstances, you need to test how it works best for you.

Thank You. Now everything is clear, because someone mentioned 3dB of difference between one and two chain...

in your screenshot you have 20, and that is for one chain, as you are using 802.11g, switch to n, and enable second chain. Result will be 23dBm as written.

Thank You. Now everything is clear, because someone mentioned 3dB of difference between one and two chain...

dBm = 10 log a, a in mW output power, base is 10 == one chain

2 chains means 10 log (a+a) = 10 log 2a = 10 log 2 + 10 log a = 3 + 10 log a (in dB), (10 log 2 = 3)

Regards

Ali