Gain more than 20 dB in uhd tx


I am using gnu 3.7, Ubuntu 13.04, USRP N200 with XCVR2450.

When I run gr-uhd/ examples/grc$ sudo ./ I can increase
tx gain to more than 20 dB. The power of the XCRV2450 is 100mW.
In this case the sink or the source will react to an higher gain

  1. Why does it happen?

  2. The second question is how about always transmitting with max gain?