HackRF One from Great Scott Gadgets is a Software Defined Radio peripheral capable of transmission or reception of radio signals from 1 MHz to 6 GHz. Designed to enable test and development of modern and next generation radio technologies, HackRF One is an open source hardware platform that can be used as a USB peripheral or programmed for stand-alone operation.
Great for listening on RF emitters and transmitting on ISM bands (check your country’s ISM frequencies before transmitting). It’s even better if you are HAM licensed with an ultra-wide range of transmitting frequencies (basically, all of them)!