Sub-GHz, 433 MHz & RTL

RTL_433, RFLink, OpenMQTTGateway — capture cheap weather stations, TPMS, and remotes.

The "free sensor" tier — half the consumer-grade weather stations, tire-pressure sensors, doorbells, and 433 MHz remotes already on the market beacon their data unencrypted. A $25 SDR or a $5 ESP32 receiver, and they're yours.

For the broker carrying decoded messages see MQTT for Home; for ESPHome firmware see IoT Firmware Platforms; for the BLE side of "promiscuous listening" see BLE & Bluetooth IoT.

RTL_433 — the SDR-side decoder

★ RTL_433 — C; takes IQ samples from an RTL-SDR (or HackRF / SDRplay), demodulates / decodes 300+ device protocols at 433 / 315 / 868 / 915 MHz, and publishes JSON to stdout / MQTT / syslog. Weather stations (Acurite, Ambient, Oregon, La Crosse, ...), TPMS, doorbells, garage remotes, energy meters, and on and on.
- https://github.com/merbanan/rtl_433
★ rtl_433 Home Assistant add-on — wraps RTL_433 + an RTL-SDR dongle + MQTT auto-discovery; one-click for HA OS users.

RTL-SDR hardware

★ Nooelec NESDR Smart v5 / NESDR SMArt XTR — quality RTL-SDR with TCXO; the recommended starter. ~$30.
RTL-SDR Blog v4 — newer chipset; broader frequency range; the default 2026 pick.
RTL-SDR.com v3 — older but plentiful; works fine.
HackRF One — full transceiver; SDR superpower; expensive (~$400 in 2026); overkill for receiving but fun.
SDRplay RSP1A / RSPdx — superior receiver; good for wide-band capture.
★ A long antenna helps more than a fancy SDR. Get a real outdoor antenna with a low-noise amplifier before upgrading the SDR.

OpenMQTTGateway — the ESP32-side decoder

★ OpenMQTTGateway (OMG) — see IoT Firmware Platforms. With a CC1101 or SX1276 module wired to an ESP32, OMG decodes 433 MHz / 868 MHz protocols, BLE, IR, and publishes everything to MQTT. The "I don't want a Pi running an SDR" answer.
- https://github.com/1technophile/OpenMQTTGateway

Sonoff RF / Tasmota approach

Sonoff RF Bridge R2 — flashed with Tasmota or Portisch firmware; learns and replays 433 MHz codes; great for cheap PIR / door / smoke alarm sensors that are already in your house from past gimmicks.
Tasmota with PORTISCH firmware — extends the RF Bridge to handle protocols the stock chip can't.
CC1101 + ESP32 in Tasmota — Tasmota also speaks CC1101 directly; competitive with OMG.

RFLink

RFLink Gateway — older Arduino-based 433 MHz / 868 MHz / IR gateway; serial bridge; HA integration. Less active than OMG in 2026 but still works; large protocol library.
- http://www.rflink.nl/blog2

TPMS / car tire pressure

★ rtl_433 -R 60 captures most TPMS sensors at 315 / 433 MHz. Useful for fleet management or "is my trailer leaking again?"
Tire-pressure decoders for individual brands are baked into RTL_433.

Energy / power meter telemetry

rtl_amr — separate RTL-SDR program for AMR / ERT electric / gas / water meters in North America (some utilities still use unencrypted broadcasts). YMMV; check your meter's frequency and encryption status.
Hildebrand Glow Stick / Glow IHD (UK) — small MQTT gateway that exposes Smart Meter (SMETS2) consumption data over MQTT. Pricey but clean. See Energy Monitoring.

Hardware to know

CC1101 — Texas Instruments sub-GHz transceiver; OOK / ASK / FSK; the default chip behind 433 MHz tools.
SX1276 / SX1278 (Semtech) — LoRa-capable transceivers (also do FSK); reach for if you also want LoRa.
NRF905 — older; legacy.

Practical guidance

Antennas first, gain second. A quarter-wave whip cut to length destroys a fancy SDR with a stock rubber duck.
rtl_433 -F mqtt -F json — publish to MQTT and log raw JSON for diagnostics.
Specify protocol IDs (-R 32 -R 40 -R 153) in production. Running with all 300+ protocols enabled wastes CPU and produces ghost detections.
Filter by device.id — most sensors broadcast a stable ID; lock onto yours so a neighbor's identical weather station doesn't stomp on your readings.
Range matters more than the SDR. RTL_433 outdoors with a real antenna will pick up sensors a kilometer away in clear conditions.

Pick this if…

Default sub-GHz capture: RTL_433 + RTL-SDR Blog v4.
No SDR, ESP32 only: OpenMQTTGateway with a CC1101.
Existing 433 MHz remotes / sensors with replay: Sonoff RF Bridge + Tasmota.
TPMS / fleet: RTL_433 with -R for your protocol.
UK smart meter: Hildebrand Glow Stick.

Sub-GHz, 433 MHz & RTL_433