How can I set the bandwidth of the Lopy4 to 7.8 kHz to achieve the RF sensititvity of -148 dBm?

[iotGeek]

I have read about the -148 dBm RF sensitivity in the Lopy4 specsheet on page 21:

How can I set the bandwidth of the Lopy4 to 7.8 kHz to achieve the RF sensitivity of -148 dBm? The documentation says I can chose only LoRa.BW_125KHZ , LoRa.BW_250KHZ or LoRa.BW_500KHZ for the bandwith. I would like to use the Raw LoRa mode.

[bmarkus]

To go below 125kHz bandwidth your modem must have a TCXO, an ordinary XTAL do not have the required stability. Is Lopy4 equipped with TCXO?

[iotGeek]

@bmarkus right now it has no TCXO but I can connect one to the Lopy4:

[bmarkus]

If you have the proper hardware, you need a custom firmware to support additional bandwidth settings. Lower bandwidth means lower speed or longer transmission time which can be an issue not only for the application but for local regulations, see 1% transmit duty cycle in Europe or max 400ms dwell time in US. Is it really worth? There must be a reason why it is not used by others.

[jcaron]

@bmarkus In Europe, one of the sub-bands allows 10% duty cycle. Also, IIRC if you do LBT-AFA (listen before talk, frequency agility), there's no duty-cycle limit (maybe not on all bands, too lazy to check).

[bmarkus]

@jcaron said in How can I set the bandwidth of the Lopy4 to 7.8 kHz to achieve the RF sensititvity of -148 dBm?:

@bmarkus In Europe, one of the sub-bands allows 10% duty cycle. Also, IIRC if you do LBT-AFA (listen before talk, frequency agility), there's no duty-cycle limit (maybe not on all bands, too lazy to check).

You are right, and also allowed RF power may vary on subbands. Still bitrate is very low.