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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Should I power it seperately? Is the power it is getting from pixhawk not enough for long transmission?

Sahmeem, yes, the Pixhawk will not deliver enough Amp (depending on your power-settings). Please do power from its own 5 V source. How are your results with the circular polarized antennas and setup remote from the copter-frame ?

It has been a long time since updating everyone on what we have been up to!

The RFD900x and RFD868x have been quietly released into the marketplace and are proving to be as good as expected.
The key differences between the RFD900+ and RFD900x series is the replacement of the processor with a 32 bit arm based processor, along with an improved radio transceiver.

The processor gives a large capability boost which has let us implement: Encryption, transparent PPM pass through and higher data rates.

All the new features, PPM, Encryption, are explained in the datasheets which are online ( Sorry it took ages to get them up! )
One key thing to be aware of is that the 900X series modems are only 3.3V I/O tolerant.,   The 900+ are able to take 5V on I/O pins.

We are in the process of developing a JR style TX module which can plug into the back of an existing transmitter and give RC control over a 900MHz link, **AS WELL AS** a Wifi access point for mission planner to connect to and pass through telemetry data, wirelessly from your laptop, tablet, or android phone running tower.  We have prototypes working and are getting plastic tooling manufactured at the moment :) :)

A ruggedised base station is also under design which houses a similar access point, and is battery powered.  
This enables a clean, wireless ground station setup.

With earlier versions of 900x firmware we were able to get a net throughput of around 300kb/s, which some beta customers were able to put through 640x480 x 20FPS video over the RFD900x link.  We have proto firmware working at higher rates, expecting up to around 700-800kb/s to be a practical limit of where we get to.  This should give a more reasonable video quality.   Range will not be as good as with the normal telemetry rates of 64kb/s, but, should still be quite respectable.  The target is to achieve around 5km or more with video over the link.

We have also been busy in the background with an asynchronous version of firmware which allows virtually any number of nodes to be in the network at the same time.  This is planned to be used for industrial applications, but, could very well be useful for swarming applications of UAVs.  We have had a few discussions with Mike Oborne on ways of making it all work nicely with Mission Planner, but, at the moment, the swarming support is only in planning stages.   The Async firmware is working well overall and is the recommended multipoint solution.

Modem Tools - originally they were based on Python and Glade which was OK for a while, but, the transition to WIN10, broke a fair few things with the libaries which are very frustrating to try to track down.   We have changed over to a C# implementation which is based on the work from Mike O, and integrated all the options on the 868/900u, 868/900+ and 868/900x.   The new modem tools are available to download in the files/Tools section on our support site.  http://files.rfdesign.com.au

On our web store you may also notice a bunch of Pixhawk2 related hardware.  We have found working with the UAV developer and manufacturer community really enjoyable over the years and figured that we would like to help by supporting the Ardupilot community with great hardware and good service.

I also just realised that it is around 5 years since my first post in 2012, announcing the original RFD900 modem.   I am thankful for your support over the years which has enabled us to keep making new products and being able to be a small part of your projects as well.


Hi Shameem,

Regarding the poor range on your setup, would you be able to email some pictures of the quad/antenna setup and the ground station antenna setup to info@rfdesign.com.au, or post them here?  - We may be able to offer some assistance with what you are seeing.

The antenna placement and ground reference for monopoles has a large effect on performance of the antennas.  Also, the RF noise level in band on the vehicle and ground station can significantly affect range too..

I have a couple of RFD900+ radios. If I get a 900X for my new airplane will it link with my 900+ ground station?

I tried to use the new 2.0 tool and it will not connect to my 900+ with 2.6 firmware. I have 1.6 tool on the same computer and it works. Is 2.0 tool for 900x only or am I doing something wrong?


Hi Seppo et al,

What is the status on regulatory compliance in Europe for RFD868x? Will this be pursued by RFDesigns at some point? Is there an eta for this? The documentation (particularly for the 868MHz version) is quite light but does state that "The modem is designed for system integrators who will integrate the modem into their own projects and product prototypes.  The user is responsible for compliance with local regulations for radio transmitters."...while listing the general compliance achieved for Oz/NZ and the US/Canada. It would be great to get the basic compliance confirmed for EU operation as well. 

If importing the modem to the EU as a consumer it seems to be hit and miss whether customs lets them through. My last order got returned to Australia by customs due to missing CE mark (and lack of statement of conformity / RTT&E, i think). 

I am supporting a project that looks at integrating a 868x into a commercial UAV which is sold in limited quantity - getting the end system compliance tested and certified is financially not feasible. Has anyone operating the units in Europe (or specifically Germany) had compliance successfully confirmed? Any practical tipps? 



Hi Seppo et all,

I have been using the RFD900 and 900+ for quite some time now. I m very happy with their performance. i had made a small change to the connection configuration of the modem with pixhawk. I am externally powering the RFD900 from before also. Now i have made a longer data cable for the interface between Pixhawk and the modem. After this particular change, it takes almost 2 full minutes for the initial connection to take place on the GCS. Previously, the connection would take a maximum of 20secs.

Nevertheless, the performance is still very good but the time taken for the initial connection is just too long. What could i possibly be doing wrong??

Thanks & Regards,


Does the RFD868x with FW 2.53 support single channel / non hopping mode? It does seem to accept the setting even though the config tool and docu says minimum number of channels is 5. 

Thanks + regards,


Dear Seppo,

My Rfd900 was working perfectly for 6 months now.Suddenly yesterday Stuck on boot loader mode. I tried uploading all the firmware available with all the available tools from rfdesign.com.au. Still nothing. Is it possible to send it to you and check what is happening? 

Kind Regards Dimitris

follow on about PPM use.

I have a system setup using the PPM over RFD900x to control a gimbal.

When the motor (electric heli) starts the gimbal usually rotates left and down. Looking at the PPM output from the radio it is outputting min on all channels (~1000us). If I turn off my RC transmitter I get output held for a couple of seconds then about 1500ms on chan 1 and 2 and min on chan 3...

I have tried to set the default (failsafe?) PPM value with the 

   AT&R Record default PPM stream for PPM output (vehicle side)

but I just get an "ERROR" Response... 

how do I set the default PPM (when there is no valid signal) to the vehicle ?

RT&R Record default PPM stream for PPM output (vehicle side)

When will the default be transmitted to the vehicle...


There will be a time lag of about a second before failsafe kicks in.

Please ensure you have V2.4 or later when using PPM as the recording had a bug previous to that.

Please ensure that you are connect via ftdi cable to the vehicle side when sending AT&R,

or to the ground side radio when sending RT&R.

You cannot set the default signal correctly until you have an active ppm stream going to your vehicle, otherwise there is no stream to record.

The default (recorded stream) will be sent once the vehicle side radio fails to see  a PPM stream for 50 ppm cycles. Cycle time varies between radios and stream length, but about 22ms is nominal , so roughly 1 second.

Did the RFD900 ever get FCC approved? If so, can you please provide the FCC ID?

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