alt Hacker NewsI’m not an expert but I know of a few. Are you looking at recieve only, or transmit/ recieve? What frequency ranges?
Off the top of my head
HackRF one- relatively cheap, pretty good transceiver, lots of crappy clones
USRP B205mini, expensive, fast, closer to pro equipment
I like my HackRFOne, but be aware it's half-duplex, so it can transmit as well as receive - but can only do one of them at a time. For a little more money you can get full duplex SDRs, which opens up a bunch of extra interesting sttuff you can do.