RFD900, RFD900+ - New long range radio modem

Hi All,

I would like to introduce you to a new radio modem that we developed for very long range datalinks!


Some of the key features of the RFD900 are as follows:

  • Multi point and point to point link capability.
  • Long range >40km depending on antennas and GCS setup.
  • 2 x RP-SMA RF connectors, diversity switched.
  • 1 Watt (+30dBm) transmit power.
  • Transmit low pass filter.
  • > 20dB Low noise amplifier.
  • RX SAW filter.
  • Passive front end band pass filter.
  • Open source firmware / tools, field upgradeable, easy to configure.
  • Small (30 x 57 x 13 mm), light weight (14.5g).
  • Compatible with 3DR / Hope-RF radio modules.
  • License free use in Australia, Canada, USA, NZ.


These modems are designed to support long range applications, while being easy to use and affordable.  

These modems have been flying in various platforms and have demonstrated excellent performance in real applications. 

RFD900 modems are now available at: http://store.rfdesign.com.au

Support within APM planner and the radio configurator from Michael Oborne is already available.

It works seamlessly with APM planner, all radio Mavlink parameters are available.

Update, December 2014:  The RFD900+ with improved specifications is available now at:


Seppo Saario



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  • Moderator

    Hi everyone,

    We are trying to put RFD900+ in a single channel (non-hopping) mode to execute some frequency tests, does anybody have a hint to put the module in "Test-Mode"?

  • Thanks for that Paul. Hopefully will get it sorted shortly and be in the air soon.


  • you need a jumper if you are powering the radio from FTDI or from pixhawk

    pin 4 is the + (positive power) pin for the radio, 1 and 2 are the - (negative) ground pin and are interconnected, pin 5 is + from the cable and pin 5 and 6 are interconnected, so you need to jump 6 and 4 to get power from pin 5 to pin 4. 

    if you use external power supply  4 is + and 1 or 2 is -

  • This is off the RFD900 datasheet/manual.

    Pin 1 of the FTDI cable (black wire) should connect
    to pin 1 of the RFD900 header. In order to
    power the modem from the +5V USB power, a jumper is
    needed to connect pins 4 and 6.
    To power the modem from an external +5V supply, con
    nect the power to pins 2 and 4 as
    shown in figure 5.1.

    Thought this was how to set up.

  • Developer

    no, you are reading "it" wrong.   what are you reading? 

    Glen Leeon said :

    Am I reading this right?

    The modem that is on the quad should have a jumper across pins 2 and 4.

    And the modem connected to computer via USB has jumper across pins 4 and 6?



  • Am I reading this right?

    The modem that is on the quad should have a jumper across pins 2 and 4.

    And the modem connected to computer via USB has jumper across pins 4 and 6?



  • V2.4 firmware for rfd900x radio.

    Here is a link to AT command interface.


    The new one will vary slightly. ATI5 will show new parameter set, and ATI5? will give parameter info.


    SiK AT Commands
  • I assumed your talking 2.4 firmware, instead radio version number ?

    kent Martin said:


    Please first ensure you have version 2.4 or later. There was a bug with ppm record on earlier versions.
    If yours isn't let me know, and I can send you the correct version.
    PPM input or outputs pins can be configured for your ground and air radios respectively.
    Set up PPM input and output before recording fail safe ppm signal.
    The air side radio should also record your desired PPM signal in the even of radio link loss. 
    ( You can do this with remote AT if you like, note it will give an error if you try and record the ground side).
    You should set your controls to whatever will let you flight controller know that something is wrong,
    Then type in the AT command to record the ppm stream. Check in Mission planner that the signal is correct, then record it.
    Put your controls back to normal and check mission planner has returned to normal, then turn off your transmitter and ground and check that mission planner is going into the correct mode for a fault.
    AT commands are:
    1. for PPM input (ground)(pin 15 of header GPIO1.1,GPI1_1R/CIN ) "ATI16 = 1 "
    2. for PPM output (pin 15 of header GPIO1.1,GPI1_1R/COUT ) "ATI17 = 1 "
    3. to record the PPM stream for link loss "AT&R"
    The PPM input will need to be level shifted down to 3.3V as it is not 6V tolerant, which is likely the level coming out of your transmitter.
    You can make one up with 3V zener and 1K resistor, or we will hopefully be selling adapters for this soon if you are not familiar with this yourself.
    Note you can't configure both PPM input and output on one device as they are the same pin and you will have to disable one before enabling the other.
    Note also that you configure the correct end and don't mix them up.
    Once configured you should be able to control your aircraft using the radio and use mavlink at the same time.
    Note, you might notice it's not quite as responsive due to delays, but it is very flyable. 
    If you're drone racing, it might not be what you're after. (maybe in the next version of firmware this might get improved on).
  • Developer

    Dennis and Paul,

    The multipoint firmware for RFD900 does not do relaying. It only supports a topology where you have multiple ground stations and one aircraft, so that you do not need to send packets between the two radios that are not in line of sight.

    I have built a firmware for the upcoming RFD900x that does do relaying and I will release the firmware once the RFD900x is released. We are using the firmware for OBC'2016 to get packets from the retrieval aircraft to the GCS via a relay aircraft. The firmware I've written is a fairly simple change to the point-to-point firmware rather than being based on the multipoint firmware. It only supports 3 nodes at the moment, but could be extended to more nodes if needed.

    Cheers, Tridge

  • Kent,

    Thanks for the info. Loads of it there for me to digest at this stage but will work slowly through it get to where I want to.

    Firstly. I am not familiar with AT commands and where/how I view/change and program them. Can you point me the right direction? What do I need to use to set up and even check which version my modems are at the moment?



This reply was deleted.


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