Best radio type for 5 floor communication

  • Hi,

    I am looking to set up a sensor in my garage, which is located inside my apartment building, 5 floors below my controller (Home Assistant, with zwave, zigbee and RFXCOM interfaces, as well as a mysensors gateway, that is not connected yet, but has only a NRF24L01+ radio), which is inside my apartment. I live in the third floor, the garage is in floor -2.

    I have been looking at RFM69, as well as RFM95 specs, that refer a 500 m / 2 km line of sight range ( 1). A mysensors implementation of a presence detector or a remote switch for the garage door would not be hard to do.

    My question is: considering that the range I am looking for is much shorter than any of those (about max 30-50 meters in a straight line), but with a lot of concrete walls and iron structures in between the two points, do you think this could be a good solution?

    If not, what would you advise for such application?

    Thanks for your help!


  • Hardware Contributor

    @andrezibaia - my understanding that lower frequencies easier penetrate walls, and im also suspecting the Nrf24l01+ (2.4Ghz) wont work. Im using RFM69 for my outdoor nodes, and its working well penetrating the house walls - but in your case you have multiple floors (thicker than walls?)... If you have the radios, I would try them.

  • Yes, lower frequencies are better for going longer distances and penetrating walls, etc. I also would not try the NRF radios. 2.4GHz almost certainly won't do it.

    The 433MHz RFM69 might do it, but I would be a bit surprised. I think your best shot is to try a LoRa module, so the RFM95 might do it.

    If it doesn't work right away with just the boards and basic antennas, it's always possible to get better range with a good setup of directional antennas. In fact, sometimes having the right antenna is almost more important than the radio. (Not really, but it is super important.)

  • From my experience (I have more then 10 nodes with RFM69 HCW 433Hz - I've choosen it according better penetration by walls and slabs). All nodes working with standard wire antenna.

    • My nodes inside the internal garden (distance about 15 m to the gateway with one glazed wall (aluminium structure)). They work with maximum power of signal and my RSSI is about -95 dB (poor). Sometime I lost the signal which is very frustrating.
    • Node at upper level than the gateway (distance about 4 m, reinforced concrete slab between). RSSI is about -86 dB and signal is stable (signal breaks are rare).

    What I can say after three years using RFM69:

    • distance inside the building is short (to about 15 m, stable signal to 10 m or less)
    • sometime signal is lost and it depend from different reasons (ie. weather - yes, inside the building too)
    • nodes or gateway should be at hight min. 1 m above the slab (heigher is better)
    • nodes should be away from other transmitter (ie. wifi router)
    • I have experimented with different kind of antennas but without big success (but still wire antennas, not with directional ones)

    I have built few nodes with NRF24L01 but I couldn't use them at all - very short range in my house. That's why I've choosen RFM69 (a little bit better).

    I'm not happy with RF modules and now I try to jump to RS485 system by wire (I have alarm system I don't use and I try to adopt it). So I'm glad that MySensors have RS485 gateway now. I have built 4 simple nodes with RS485 modules and they work for couple of months without problems. And they work with star typology up to 17 m. Thank you MySensors !

  • Hardware Contributor


    I also think in your case rfm95 or equivalent might be the solution.

    About personal xp, I mostly use rfm69 in prod, 868mhz because 433mhz needs bigger antenna, and bigger gnd plane else you don't get the full range that 433 can provide. Note: available freq depends on where you live

    I use ATC which sets emission power level from -18 to +13 (for rfm69cw) :

    • gw is high power version (rfm69H or rfm95)
    • homemade pcbs with optimizations for a good range, of course there are often compromises to do vs design
    • rfm69cw (the low power version) and a short range of 10-12m, with 2x rock/concrete walls obstacles, I set ATC RSSI target= -87, and power level is autoadjusted to -11. So it can do a lot more than 10-12m at full power
    • rfm69cw at 55m from the GW and it's ok, with many obstacles on the path (7x rock/concrete walls, a part of the roof is metallic, metallic doors etc)

    As you can see, it's dependant of many factors as different people get different results.

  • Hero Member

    @andrezibaia LoRa has by far the biggest link budget, so if it can't manage it, probably nothing else can either, assuming similar transmit power.

    Also, you may find that your best signal path isn't straight through 5 floors of reinforced concrete but rather bouncing the signal off an adjacent building or the like.

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