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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  • Hi Jeremy,

    Following on from Paul, if you check the signal quality in mission planner in the tuning page.  RSSI, Remote RSSI, Noise and Remote Noise are the parameters of most interest.

    Generally noise is around 40-60 counts, and when both radios are set to 20dBm, in reasonalble (say 0.5m) away from each other, with dipoles, or monopoles, you should see around 205 to 217 on both modems for RSSI.

    If both modems are showing similar values, then the hardware is OK.

    If one is showing something significantly less, say, 150 to 180, while the other is at 217, then there is a modem issue, which we will sort out for you.

    The biquad looks pretty nice, It will be interesting to hear how that works on the tracker..

    On the copter side, to get the best results there, it is better to use a dipole (a little big I know), or, a flex 1 antenna on a plastic strip.  The monopole antennas, both straight and 90 deg versions are designed to work with a ground plane.

    When mounted straight onto the modem, the performance is degraded, but, certainly not to the level you are seeing now.

    With best regards,


  • @Kent and @Paul thank you for the reply.  

    Here's a link to the photos so you can see exactly what I'm talking about.  It has all my ATI5 params posted there as well.  BTW, the air side antennae are NOT pointing, simply using some quarter wave dipole omnis.  However, even using the 20dBm settings I should be getting more than 1000ft range before my signal quality degrades below 40%!  I'll have to try some of the tests you mention when I get some more free time this weekend.


    Also here's a video of my previous test that was obviously pretty close in range so you can see the tracker actually working.  Now to sort out that pesky telemetry signal problem.  


  • Jeremy,

    I can't see the photos you added.

    From your description I assume you have something moving your antennae on the air side.

    Is it both or just one antenna?

    Might be best to go back to basics to find the problem.

    Install standard antennae on the air side without position control.

    Set power to 30 dBm (both ends). i.e. a normal set-up.

    Check how this performs. 

    Also send though a log of both your radio's config (ATI5).

    If this test works then there is a problem with your controlled antennae somewhere.

    If not then need to check anything else non standard ( antennae, and fitted securely).

    Let us know how you go.

  • In MP the signal quality drops to below 40% at 1000ft from home.  :(

  • What is the signal quality if you check with MP or radio tools ?

  • All in the know about RFD900 radios with Mavlink based telem data.

    So believe it or not I'm having some range issues with my RFD900+ radios.  I keep reading and reading and hearing about how folks are getting 10km or 15km or more with the 30dBm setting and 64kbps bandwidth, but I'm getting ~1000ft!  No problems actually connecting, just really short range before degradation, details on setup below.  I'm putting ample power into both RFDs so I just can't figure out what the problem is.  Wondering if anyone has experienced something similar or maybe I just have defective radios?

    I got my antenna tracker up and working with a 900MHz biquad attached to the rfd900+ but my telemetry link is marginal at best even at 1000ft away.  My tracker actually stops pointing due to data loss at anything more than that.  Any thoughts?  I have quarter wave dipoles on the "tx" end and on the "rx" end I've got my tracker with one biquad and one larger whip.  I'm only running the radios at 20dBm power output (default) but I should still get much further than 1000ft!  I put tx and rx in quotes since the link is obviously bidirectional.  Here's a couple photos of my setup.  Any help would be greatly appreciated. 


  • ok, thank you

  • sarkis,

    A default key is set but obviously this is not very secure.

    To change it you must set both ends with a new key that is the same.

    Encryption is 128 bit or 16 bytes of hex data (32 nibbles of ascii hex characters)

    The command is


    change the string to any 32 hex characters (0-9,A-F) of your choice.

    You must set all 32 characters. you can also set the remote end via RT instead of AT ( and don't forget to save AT&W)

    make sure to set remote end first and reboot before doing local end or you will lose the link.

    reset local end and check that you have connection again.

    If you lose link set each one locally to the same key and try again.








    please assign your own unique KEY for security purposes.


  • Hello I have a question about encryption
    In settings I have actyivated encryption ,,ats15=1
    Encryption level 1
    But don 't know how to set encryption key.thank you
  • Wow! thank yo very much kent, Ill test them right away and give you any feedback possible.


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