HP ProCurve 530 NA (J8986A) Management And Configuration Manual page 176

Wireless Interface Configuration
Modifying Antenna Settings
6-24
Figure 6-8. Setting Transmit Power Reduction
To Modify the Transmit Power Reduction:
Select Network Setup > Radio.
1.
Use the Tx Power Reduction drop-down to select a dBm value.
2.
[Update]
3. Select to set the radio transmit power reduction.