Meshtastic Live Decode (ct125)
2026-09-27
Meshtastic uses 869.525 MHz with 250 kHz wide LoRa signals (LongFast is spreading factor 11), heard by an RTL-SDR running OpenWebRX+. Here OpenWebRX+ does the decoding itself: it drops damaged and duplicate packets, decrypts the default LongFast channel with its public key, unpacks the payload and publishes each result over MQTT to the monitor node, which keeps a running log and a table of nodes by their 32-bit node number. Text on the default channel, node names and hardware, battery and airtime telemetry and traceroutes are readable; packets from other channels show as encrypted, and positions are not published. Getting this working took some detective work: at first not a single packet decoded, even strong ones from a test node on the desk. Comparing the RTL-SDR with an Airspy R2 on one antenna through a splitter showed that gain, the centre frequency and the dongle itself made no difference; the culprit was the sample rate. At 2.048 MS/s the resampling to the decoder's 1 MS/s corrupted the long chirps, while at 2.0 MS/s every packet decoded. The log is at fbbaa87a5c6f7d336979478ceb04aae6.
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