Flex1800 properties

Hi All,

I am trying to estimate a narrow-band 2x2 MIMO channel by using two PCs,
USRPs and four flex1800 daughterboards.

I want to be able to measure the gain of the four subchannels with high
accuracy. Of course calibration is required - and this is what I am
struggeling with.

On thing I seem to have discovered is that there must be no signal
than -50dBm when the gain of the receiver is set to 50dB. Any signal in
case includes signals far (in frequency) from my desired signal.

It also seems like the gain of the receiver chains can differ a few
of dB depending on the signal strength of the input signal.

Does this make sense ?