Antenna for the RFM69



  • Hi,

    I guess I'm lacking a bit of antenna theory...

    I'll be connecting a single core wire to act as an antenna to the RFM69 module. I could understand that it should be exactly 164.7mm long for 434Mhz. I could also understand that having the most accurate lenght makes all of the difference in the antenna efficiency.

    Now my question is: Since I'm going to solder it in the RFM69 hole, should I consider a few mm more, for the part that goes through the hole?
    In other words, is the 164.7mm the size from the PCB surface (and therefore needs a few mm extra to get into the hole), or what matters is having a 164.7mm wire soldered (and having some mm out in the other PCB surface).

    Thanks,
    Joaoabs



  • @joaoabs said in Antenna for the RFM69:

    the part that

    I'm no rf antenna expert but to my understanding the length corresponds to unshielded part of the wire, so if the hole is surrounded by the ground plane then the length is measured from the pcb surface.


  • Hardware Contributor

    @joaoabs said in Antenna for the RFM69:

    I'll be connecting a single core wire to act as an antenna to the RFM69 module. I could understand that it should be exactly 164.7mm long for 434Mhz. I could also understand that having the most accurate lenght makes all of the difference in the antenna efficiency.

    Now my question is: Since I'm going to solder it in the RFM69 hole, should I consider a few mm more, for the part that goes through the hole?
    In other words, is the 164.7mm the size from the PCB surface (and therefore needs a few mm extra to get into the hole), or what matters is having a 164.7mm wire soldered (and having some mm out in the other PCB surface).

    this exact antenna length is in an ideal world, but it's a good start. There are some points here that can also modify rf performance too https://forum.mysensors.org/post/91880

    In short, pcb shape and its gnd size including battery (called the antenna gnd counterpoise, wider for 433mhz), antenna shape, bent or not, can have effects on bandwidth, efficiency etc.
    when you don't have tools for checking rf, you could empirically experiment by adding/removing few millimeters and see how it affects rssi for example. And better checking it with your node in final setup (in enclosure with battery, as it can also affect perf).
    This is fine tuning but sometimes depending on the node build it can improve range, then needs less TX power for same job, less TX power = less batt used.. and "greener" RF/less loud


 

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