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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  • I'm trying to visualize what I would need to replace the radios on my plane and quad with an RFD 900x.  I'm not sure how to connect my FrSky Taranis, or Spektrum, controller to the PPM on the 900x which would also be connected to the tablet or laptop.  Or is this not possible?  It would be great to only have one radio for the telemetry and control.

  • Scott,

    Hmmm, I'm not sure I'm allowed to say?

  • Thank you, Kent.

    One more question.. Any plans to release a mini version of the 900x?

  • Scott,

    Hopefully we'll get some time to look at SBUS. In the mean time hassle Arducopter to support 16 channels PPM.

    We support up to 16 in PPM now. 

    It is not envisaged for us to have interoperability with 900x and 900+. The 900+ although a great workhorse is not easy to work with. It is open source however so with mods to 900+ code and it could be updated to talk to the 900x in theory.

    This would be the best option, however there are still some hairy problems you could come across. The SIK developers may be interested in trying and I could lend them my knowledge to help them bring it up to scratch but they might have the same objections to working with that processor. 

  • Kent, I'd be very interested in SBUS, because there are some limitations w/ PPM and Arducopter (only supports 12 channels PPM), and the little PPM/SBUS decoders usually have more functions with SBUS (like the ability to output 9-16 instead of just 1-8).

    Also, an important question for me is, will the 900x's support older 3dr style modems with a future firmware update, or would I need a 900+ to interface with older modems?

    RC latency seemed like gopro video lag to me..  But I didn't time it.  Only move transmitter, some 100's of ms delay and the servo moved.  I think it would be flyable w/out much trouble at all, but I have still not flow w/ it yet (I kind of need sbus support, or APM to support 16 ppm channels before I can use it)

  • PPM latency is linked to the window timeslot. Usually set to about 100mS (@64K).

    It is also affected by how much data is being sent back down at the time as it can use unused portions of the aircraft side downlink (unless there isn't any).

    Reducing the window timeslot will reduce latency. However there will be a cost with throughput.

    During testing I couldn't notice it, but a more expert flyer said he could.

    So it may not be good for drone racing but for many other applications it should be suitable.

    If you tinker with settings let us know how it goes for you. 

    It won't be made available on the 900+. Yes there are significant processor differences that would make it near impossible (except for the very insane) to do on the 900+. 

    We might be looking into SBUS interface in the future as well.

    We do have other firmware that will likely be better than SIK (conventional time slicing), that should do much better at latency however this is still in development. 

    If anyone is using it now, let us know how well you think it is working, and try some tweaks to max window time (ATS14 I believe), if you're keen.

  • Developer

    PPM over the 900+ is not currently possible, at all. Its a new feature of the 900x, which have a more powerful processor onboard.

    Ravi said:

    can someone suggest if the PPM input and output via pin15 is possible on older RFD900+. would the firmware needed to be upgraded on RFD900+. I had been thinking about this for a long time since I fly long distance fixed wing aircrafts.

  • can someone suggest if the PPM input and output via pin15 is possible on older RFD900+. would the firmware needed to be upgraded on RFD900+. I had been thinking about this for a long time since I fly long distance fixed wing aircrafts.

  • I see that the 900X has just become available. Does anyone have more information or specifications?

  • Interesting. Thanks

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