rfm69 frequency question



  • Hello,

    I have a problem in understanding rfm69 different frequency modules. I have a GW with the latest MySensors and rfm69hcw (LORA footprint) transceiver. This is 433Mhz one. Today I received a bunch of 868Mhz ones and installed a 868Mhz rfm69w on a node. The code on the node was compiled with RF69_433MHZ (I used to use this node with 433Mhz rfm69w). To my surprise the GW with 433Mhz transceiver has been talking to the node with the 868Mhz transceiver (though compiled with RF69_433MHZ option). How come this possible?

    Thanks
    Alex



  • @alexsh1 said:

    I have a problem in understanding rfm69 different frequency modules. I have a GW with the latest MySensors and rfm69hcw (LORA footprint) transceiver. This is 433Mhz one. Today I received a bunch of 868Mhz ones and installed a 868Mhz rfm69w on a node. The code on the node was compiled with RF69_433MHZ (I used to use this node with 433Mhz rfm69w). To my surprise the GW with 433Mhz transceiver has been talking to the node with the 868Mhz transceiver (though compiled with RF69_433MHZ option). How come this possible?

    The only difference between the 315, 433, 868 and 915 MHz modules are the RF circuit, that's matched to the specific frequency band. The SX1231 on the boards are the same for all frequencies. So if you have the modules close to each other it will work even if you tune a module to a different frequency than it was designed for. Felix from lowpowerlabs stopped selling the 868 MHz version of the modules as the 868 and 915 MHz modules are so similar, that the RF circuit works well for both bands

    • Jan


  • @chrille and there is no interruption if a few modules (say 433 and 868) are working tuned to the same freq RF69_433MHZ ?

    I was under impression that with 433Mhz module you cannot see 868 / 915 ones. Clearly this is not the case.



  • @alexsh1 You need to have all modules running at the same frequency, but if you're willing to loose some coverage (and potentially harm the PA of the module) you can tune any version of the module to any frequency supported by the chipset (which is a significant part of the spectrum from 290 MHz to 1 GHz)



  • @chrille OK, thanks - in essence they all can communicate, but the best to keep it to the RF it was designed for.
    Thanks for your help



  • I wish I knew about it before as I ordered several Moteinos without radios, which are very cheap in the US, and then ordering 868Mhz radios separately.
    Well, well - every day I learn something new


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