Hello!

I'v got an RB 411AH with R42n-M inside.
Antenna - Omni 2.4GHz 9dB V

Antenna has been set on middle building of complex, and when I'm in other building ( my office in other building is in same level as antenna, maybe 1-2 meters lower, and distance is like 10-20m ) and my signal is very low, on Windows 7 wireless icon I got like 1-2 lines...

RouterBoard is powered with 25m long POE cable.

Some screenshots of settings:

what are the buildings made of? are they metal roof? do they have brick walls? you may need to try a 12 or 15 db omni.

Today I tried with 12dB Omni antenna, but nothing changed still same.
I'v checked connectors for antenna and RB, everything seems fine.

Tried with switching antenna modes, but didnt changed alot

Sounds like bad design.

You cant expect an ap on one building to provide decent cover into another building as foil backed plasterboard, foil insulation, bronzed or pilkington k glass all severely degrade the signal if not kill it outright.

Have you taken readings from the first bulding to ensure that the signal is good at origin?