Decode Sigfox with an SDR

Group

IoT & sensors

In the mode list

IoT, 868 / 902 MHz

What Sigfox is

Sigfox uplinks, receive only: ultra-narrowband D-BPSK at 100 bit/s (RC1 868.130 MHz, RC3, RC5, RC6) or 600 bit/s (RC2 902.200 MHz, RC4) anywhere in the 200 kHz macro channel. Each frame's type, device ID, message counter, payload in hex (or the single bit), the downlink request flag and the authentication code (shown, never checked: it needs the device key), the CRC checked, and the three….

Frequencies and settings

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is IoT, 868 / 902 MHz.

What OnAir shows

Sigfox uplinks, receive only: ultra-narrowband D-BPSK at 100 bit/s (RC1 868.130 MHz, RC3, RC5, RC6) or 600 bit/s (RC2 902.200 MHz, RC4) anywhere in the 200 kHz macro channel. Each frame's type, device ID, message counter, payload in hex (or the single bit), the downlink request flag and the authentication code (shown, never checked: it needs the device key), the CRC checked, and the three repetitions (ranks 1 - 3, each with its own convolution code) merged into one message with their frequencies and level. Frame layout from the public Sigfox radio specification. Nothing is decrypted.

Limits and what it was checked with

Checked with generated signals and impairments; recordings of real signals welcome.

Which radio you need

This is a shortwave mode, so the radio has to tune HF. An SDRplay, Airspy HF+ or an RTL-SDR in direct-sampling mode do that directly; with a HackRF an HF upconverter or a direct-sampling receiver is the usual route. A long wire or loop antenna matters more than the radio.

Receiving and the law

Questions about Sigfox

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