Pick an RTL that does the ranges you are interested in and I doubt you can go wrong. The rtlblog v4 is recommended but hard to get ahold of now. They receive only but actually work quite well when paired with correct antenna.
HackRF is not as good at listening -- a bit deaf -- but does provide much larger bandwidth and obviously the low powered half duplex tx ability.
If you just want to grab random signals around and explore, get a cheap RTL.
If you really want to go back and fourth with a device, to modify data packets etc get a hackRF.
If you want to push beyond those limitations, you'll probably already know what you're shopping for next at that point.
Beware, you'll end up acquiring many different radio devices and then likely start building antennas out of scrap, buying a nanovna, and falling deeper and deeper into the magical rabbit hole!
HackRF is not as good at listening -- a bit deaf -- but does provide much larger bandwidth and obviously the low powered half duplex tx ability.
If you just want to grab random signals around and explore, get a cheap RTL.
If you really want to go back and fourth with a device, to modify data packets etc get a hackRF.
If you want to push beyond those limitations, you'll probably already know what you're shopping for next at that point.
Beware, you'll end up acquiring many different radio devices and then likely start building antennas out of scrap, buying a nanovna, and falling deeper and deeper into the magical rabbit hole!