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Spreading Factor is a LoRaWAN setting that controls how slowly a device transmits. At SF7, the fastest setting, a 10-byte sensor reading takes 56 milliseconds to transmit. At SF12, the slowest, the same reading takes 2.5 seconds. The slower transmission travels much further and is more resistant to interference.
Each step up in SF approximately doubles the time-on-air and adds around 2.5 dB to the link budget. ADR manages SF automatically across the fleet, pushing devices to the fastest setting that still delivers reliable packets.
- SF7 – fastest data rate (~5.5 kbps), shortest range, lowest power per transmission, best for devices close to a gateway
- SF12 – slowest data rate (~290 bps), longest range, highest power per transmission, for devices at the network edge
- Airtime impact – at SF12, one device sending every 10 minutes consumes 44× more channel time than the same device at SF7
- EU duty cycle – longer airtime at high SF limits how often a device can legally transmit in the 868 MHz band