What should be my sampling frequency?

The sampling frequency should be at least double the maximum frequency. If your measurement is done in the pass-band (2.38 GHz-2.46 GHz), so the maximum frequency is 2.46 GHz which means that the sampling frequency should be at least 2x2. 46 GHz = 4.92 GHz.

1. What sampling frequency should I use?
2. Is 48000 sample rate good?

What sampling frequency should I use?

Overall, recording at 44.1kHz is a safe option that will provide you with high-quality recordings, regardless of the type of audio project you're working on. 44.1kHz is the most common sample rate for music CDs. It captures the entire audible frequency spectrum accurately.

Is 48000 sample rate good?

For most music applications, 44.1 kHz is the best sample rate to go for. 48 kHz is common when creating music or other audio for video. Higher sample rates can have advantages for professional music and audio production work, but many professionals work at 44.1 kHz.