LoRa vs FSK
Edit on GitHubThe two modulation modes of the SX1262: LoRa sensitivity versus FSK compatibility, and which the beacon uses and why.
LoRa vs FSK
The SX1262 supports two modulations: LoRa (proprietary spread-spectrum) and FSK (standard frequency-shift keying). The beacon can use either, and the choice changes who can hear it.
The comparison
| Property | LoRa | FSK |
|---|---|---|
| Sensitivity | Down to about -137 dBm | About -120 dBm |
| Interference rejection | Excellent | Standard |
| Decodable by | Only LoRa radios | Nearly any radio |
| Data rate at sensitivity | Low | Higher |
| Bandwidth use | Wide (spread) | Narrow |
The compatibility axis
FSK at 433 MHz is what generic receivers, scanners and PMR446-adjacent hardware expect: a 5 kHz deviation FSK signal is audible on any FM receiver as a tone burst. LoRa is only audible to another LoRa radio, which is the E22 modules or a LoRa SDR setup.
What the beacon does
The firmware supports both, selected in CONFIG mode:
- FSK: the compatible default for a rescue device, decodable by the broadest set of receivers (see Receiver Compatibility).
- LoRa: the sensitive mode, used between two beacons or with a matching receiver when range beats compatibility.
The range difference
At the same power, LoRa’s sensitivity advantage is worth 10 - 15 dB, roughly doubling the range in open terrain. That is real. The reason the beacon defaults to FSK anyway is the mission: being heard by whatever is out there beats being heard farther by fewer things.
Related pages
- Modulation in the Beacon for the project’s modulation
- Sensitivity vs Selectivity for the receiver theory
- Receiver Compatibility for who hears what