the typical L-Band frequencies, so usually 950 to 2050 MHZ. I'm not sure what the upper limit of the Airspy R2 is. My RTL-SDR cuts at about 1700 MHZ
If you want to check the beacons, many are published here: http://frequencyplansatellites.altervista.org/Beacon-Telemetry_Americas.html and here: http://frequencyplansatellites.altervista.org/Beacon-Telemetry_Atlantic.html
you then have to convert to L-Band. by subtracting the LO frequency (or from the LO frequency if C-Band)
so for example a beacon at 3950 MHz would be seen by the SDR as 5150-3950 = 1200 MHz
Note that it's not uncommon that the beacons be on circular polarization on an otherwise linearly polarized satellite, or vice versa
you should also be able to see narrow transponders on the spectrum in SDR#
Looking at the manual for my Chaparral CR-10 c/ku band receiver that I mainly use as a dish mover for my FTA receiver, I notice that it has separate outputs for Base Band and Data. The BaseBand output has settings for Deemphasized, Emphasized, Unclamped and Clamped. There is also a terrestrial interference filter that can be switched in. Would using Baseband or Data output to an SDR receiver give better results than using the Loop Out on the FTA receiver?