Spectrum Analyzer

Hello, 

I want to make a spectrum analyzer. i have a USRP. I did this using QT GUI Range. 

My main goal is to create a spectrum that I can look at between 70mhz - 6ghz. When I set the bandwidth to 6ghz, i can actually see it in a window, but the sample rate of my card is 56mhz. So wouldn't the maximum bandwidth I can see be 56 mhz? 

Another Question: Can i build a 6ghz spectrum analyzer on gnuradio without writing any frequency switch algorithm?

Kind regards,