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No distinctive difference in field testing for sx1262 at low RF data rate

We tested the line-of-sight distance for sx1262 with different Bandwidth and SF but the distance is not distinctively improved at lower RF data rate.

The testing kit is: SMA antenna+sx1262+MCU+1ppm TCXO; Data package size=32 bytes. Low data rate optimzation is enabled. RX Boosted gain is disabled.

433MHz SF=11 BW=125Khz Distance: 4.86km
433MHz SF=12 BW=62.5Khz Distance: 5.1km
433MHz SF=12 BW=31.25Khz Distance: 5.2km

According the calculator tool, the sensivity at SF=11/BW=125Khz is -134.5dBm, at SF=12/BW=62.5Khz is -140dBm and at SF=12/BW=31.25Khz is -143.1dBm.

The distance at SF=11/BW=125Khz seems to be normal but the distance at SF=12/BW=31.25Khz is only about 300 meters longer. However the sensitivity of the latter should be about 10dB better than the former, which should have much longer distance. Does any one know the reason?

Btw, our instrument can not provide the LORA modulation signal and the measured FSK sensitivity at 4.8k bps is about -115~116dBm.
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Hi Marky,

Your sensitivity indication looks good. My hunch here is that you are terrain limited in your testing. 10 dB buys you 2x the distance for the FSPL calculation only, but is real world condition, you might have some terrain issues preventing from seeing a longer distance.

Maybe a Google Earth pic if where you're testing would give us a clue?