This is just a simple test using matlab (bottom: black/yellow) to directly connect to an RTL dongle and generate a spectrum analysis. I also ran HDSDR at the same time (blue screen) so that you could see what things look like there. It's the same signal @ 50.074.194 on both displays. They are sharing the same antenna.
This is just to show that matlab could possibly be used as a spectrum analyzer via an RTL dongle similarly to HDSDR (although of course in this example not nearly as nice).