On inet I found that you can not set power less than what it is in regdb. So. If in my regdb power is like this
[alex@mb2l ~]$ iw reg get
global
country 00: DFS-UNSET
(2400 - 2494 @ 40), (N/A, 33), (N/A)
(2457 - 2482 @ 20), (N/A, 20), (N/A), AUTO-BW, NO-IR
(2474 - 2494 @ 20), (N/A...