Thanks, that explains all I need to know.
Study Overview and Background
One of the popular topics of discussion concerning Ubiquiti's hi-performance radio card offerings
has to do with the driver reported transmit power levels and how they correspond to the actual
output power of the card. Because of fixed power limitations in versions of the Atheros Linux
MADWIFI driver, Ubiquiti has implemented power "offsets" as a work-around for OEM customers
using driver versions with the power limitations to achieve maximum output power. Mikrotik is the
only known 3rd party software to take into account Ubiquiti's power offset in their user interface for
some, but not all, of Ubiquiti's radio cards.
To sumarise what I gleaned from that, the Ubiquiti cards are set to give a higher output than what they say due to the madwifi driver not supporting the high power output (26dBm) so mikrotik has made corrections for these specific cards, meaning when I put in a value, like the case above of 20dBm, the mikrotik sends the command to the SR2/SR5/SR9 as "10dBm" and the card ACTUALLY outputs 20dBm as it is set to do.
As of 8/2007
Radio | Max Programmed Power | Max Actual Power | Power Offset | Mikrotik Correction for Offset
SR2 16dBm 26dBm 10dB YES
SR4 19dBm 26dBm 7dB NO
SR5 19dBm 26dBm 7dB YES
SR9 16dBm 28dBm 12dB YES
XR2 18dBm 28dBm 10dB NO
XR3 15dBm 25dBm 10dB NO
XR5 18dBm 28dBm 10dB NO
XR9 17dBm 27dBm 10dB NO
