Low-Cost APRS Digipeater and Modem Implementation Using LoRa and 2-FSK

There is increased interest in the use of LoRa Chirp Spread Spectrum in place of the Bell 202 Audio Frequency Shift Keying over FM modulation typically employed in the amateur radio Automatic Packet Reporting System (APRS) packet network protocol. LoRa’s modulation efficiency along with transceiver module cost and availability makes it enticing, in contrast with AFSK over FM’s higher cost and less efficient nature. To gauge the performance of the novel physical layer implementation in a local setting, we measure the Packet Uplink Success Rate of LoRa and Bell 202 APRS packet transmissions from various distances in a university campus environment. Despite the lower inherent transmit power of commercially available LoRa devices, LoRa-modulated APRS marginally outperforms a representative Bell 202 AFSK over FM APRS implementation.