Looks like crappy range problem from previous post is fixed now. Today I managed to reach 2.8km range with better antennas. The ones I got from LoRa32u4 supplier were NOT 868MHz antennas for sure! 2.4GHz/5GHz probably, hard to tell. Traces on PCB are ~60mm long, so perhaps those are loaded 3/2 monopoles for 2.4GHz or 1.2GHz? No idea.
Anyhow, I soldered 78mm long copper wires to both TX and RX and did the same route as yesterday. At 500m link was solid. At 2.8km, link was solid when antenna polarizations were matched. With 40dB of link budget still to spare. Quite nice!
LoRa modulation was set to:
- Bandwidth: 500kHz
- Coding Rate: 2
- Spreading Factor: 8
- CRC: On
- Receiver Sensitivity (computed): -131dBm
- Transmit Power: 17dBm (50mW)
- Total link budget: 148dB
- Payload: 13 bytes per frame
Now it's time to optimize air protocol a little and shave a byte or two…