WBX daughterboard power output

Hello everyone!

Currently we are doing some measurements for a research project on the
USRP1 and a few daughterboard. Attached is a measurement of a frequency
sweep with the USRP1 and the WBX daughterboard. There is a measurement
point for every MHz and the gain of the WBX is set to 20. As you can
see, the input power of 0dBm only results in a -17dBm output power
(around 1250MHz) at it’s best (the light blue graph).

Does anyone know why this happens? With a gain of 20, a 0 dBm input
signal should result in a maximum output of the ADC since the ADC’s max
lies around +10dBm.