Build an automatic frequency scanner with RTL-SDR and Gqrx - Slowmin
HackRF Initial Review
Using the HackRF One as a wideband spectrum analyzer – 0xStubs
Portapack H2 HackRF One RTL SDR Software Defined Radio, Software Defined Radio Kit 3.2 Inch TFT Screen 2000mAh Battery SDR Radio Receiver, SMA Antenna Socket (Host, USB, Tie Rod Antenna, Amplifier): Amazon.co.uk:
Sniffing GSM traffic with HackRF. – Ziggy's of the world