martynwheeler / u-lora

raspi-lora for micropython
GNU General Public License v3.0
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SNR readings, query #14

Open davefes opened 11 months ago

davefes commented 11 months ago

I notice that when the RSSI gets down to about -120dB that the SNR readings jumps from a low value (say 1-2dB) to a high value (ie 56dB).

I see in def _handle_interrupt() that RSSI is modified depending on SNR, but can't see anything that modifies the SNR value. According to section 4.1.1.4 in the RFM96W datasheet it looks like SNR should be reported as negative dBs below some value (ie -120dBm, maybe depends of modem_config).

How do I interpret the very high SNR readings at low signal levels?