How to increase Tx-Power on Qualcomm Atheros AR9287 in Debian?

Question

Debian

Hello. There is a Qualcomm Atheros AR9287 WiFI adapter that works as a wireless Internet access point. This adapter runs Debian 8 ("Jessie") OS.
My actions:

# iw reg set BZ
# ip link set wlan0 down
# iwconfig wlan0 txpower 30dBm
# ip link set wlan0 up

However, the commands iw list | grep "dBm" and iwconfig wlan0 keep outputting 20 dBm instead of the desired 30 dBm:

* 2412 MHz [1] (20.0 dBm)
* 2417 MHz [2] (20.0 dBm)
* 2422 MHz [3] (20.0 dBm)
* 2427 MHz [4] (20.0 dBm)
* 2432 MHz [5] (20.0 dBm)
* 2437 MHz [6] (20.0 dBm)
* 2442 MHz [7] (20.0 dBm)
* 2447 MHz [8] (20.0 dBm)
* 2452 MHz [9] (20.0 dBm)
* 2457 MHz [10] (20.0 dBm)
* 2462 MHz [11] (20.0 dBm)
* 2467 MHz [12] (20.0 dBm)
* 2472 MHz [13] (20.0 dBm)

wlan0     IEEE 802.11bgn  Mode:Master  Tx-Power=20 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off

Tell me, please, how can I increase the transmitter power (Tx-Power) for this piece of iron?

Answer 1

If my memory serves me, it is forbidden by law to set the Wi-Fi power to more than 20 dBm without receiving frequencies and registering.

Answer 2

For client devices such as a laptop, the power is a priori less than that of a standard TD of 20 dbm. Yes, and the point here is not the power supplied to the antenna, but the gain of the antenna itself, the antenna is a passive device.