RTL-SDR

An RTL2832U dongle with an R820T2 or R860 tuner is the cheapest useful receiver ever made, and the majority of what WaveShark decodes was written against one. Roughly 2.4 MS/s of usable span is enough for every protocol here that is not Wi-Fi, Bluetooth, television or a drone video link.

The bandwidth is the limit, not the decoding. A 2.4 MHz span across 433 MHz holds every sensor in a building at once; the same span cannot hold one Wi-Fi channel.

Below about 24 MHz a stock dongle hears nothing without help, so shortwave needs an upconverter or direct sampling, which the radio dialog switches on.

WaveShark drives the dongle with its own USB driver rather than librtlsdr, which is also how it runs in a browser: app.waveshark.io takes the dongle over WebUSB with nothing installed.

What it reaches

• ISM sensors, TPMS, utility meters and Z-Wave
• ADS-B, UAT, ACARS, VDL Mode 2 and AIS
• DMR, P25, NXDN, TETRA, M17 and analogue voice
• POCSAG and FLEX paging, APRS, SSTV and radiosondes
• NOAA APT and Meteor LRPT weather satellite passes

What it will not do

• Wi-Fi, Bluetooth LE, Zigbee and DJI DroneID: one channel is wider than the whole span
• DVB-T television: a multiplex is 8 MHz
• Shortwave without an upconverter or direct sampling
• Transmitting anything

Setup

Nothing from librtlsdr is loaded, but on Linux the rtl-sdr package brings the udev rules that let you open the device without root, and the blacklist that keeps the television driver off it. On Windows, bind WinUSB to the RTL2832U interface with Zadig first or nothing can open it, the browser included.