RTL-SDR

Receive-only software radio. Watch 433 MHz remotes, pagers and telemetry in the spectrum.

25–35€ Radio & RF

What it does

An RTL-SDR is a cheap receive-only software-defined radio built around a USB TV tuner chip. Paired with SDR software it lets you look at a wide slice of spectrum and demodulate common signals, from fixed-code garage remotes to weather balloon telemetry. It only listens: transmitting needs a separate transceiver.

Use cases

Survey what's on air

Sweep the 433/868 MHz ISM bands to see which frequencies a device actually uses before building an attack.

Decode a fixed-code remote

Capture and demodulate a simple OOK/ASK signal to recover the bits a garage door or doorbell sends.

Watch unencrypted telemetry

Weather stations, tyre-pressure sensors, and similar devices often broadcast in the clear.

How you use it

Confirm the dongle is seen, then point general-purpose decoders at the band of interest:

rtl_test -t
rtl_433 -f 433920000    # generic ISM-band decoder, many common protocols
# or open gqrx / SDR# for a live waterfall

Variants & pitfalls

Receive-only. It cannot transmit or replay anything by itself; pair it with a transceiver (or a Sub-GHz module) for that half of the work.

Antenna matters. The bundled telescopic antenna is a poor match for 433/868 MHz; a tuned antenna makes a large difference in range.