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 Seppo,

Yes, a long time - but good to hear the news!  Over the years, I've purchased 3 RFD900s from you and wanted to know if the Telem + PPM passthrough is a firmware update.  My modems are all RFD900, not RFD900+, if that makes any difference.



Seppo, a couple other questions - I assume encryption will only be available on the "+" version, true?  And is there any impact on the throughput?



Hi ID,

A good thing about these modems is that they use spread spectrum whereas GSM is narrow band.  When a spread spectrum receiver de-spreads the incoming signals, narrow band signals are significantly spread out and therefore reduced while the desired spread signal from the RFD modem is increased.  In other words the RFD modems should not be impacted too much by GSM signals, even if their frequencies overlap, IMHO.


Thanks for this clarification mate

Would you have any comments about the first two questions?


Hi Chris,

I am building the firmware for RFD 9000+ (i think it is RDF 900p as well). I downloaded the source code from branch :https://github.com/RFDesign/SiK/tree/SiK. And Compiling is OK. Then I uploaded the new firmware onto one of my two radio modules. 

I found the new firmware version is 1.13.  seems that this version has some problem when using 3DRRadio for configuration. 

Another thing is https://github.com/RFDesign/SiK/tree/900p_v1.9.   Is this the latest version for RFD 900p?  I am compiling it. but get some error. 

Could you please tell me which branch is better for RFD 900p? 

Thank you very much.

I used their prepared binaries (http://files.rfdesign.com.au/firmware/) - choose the one for the 900+, I believe I'm using the 1.9 binaries and they are working well for me.  I also have tried the v2 for multipoint comms.

Try the v1.12  they have on the site, if no good drop back to the v1.9.

I haven't had a need to build the firmware from them at this stage.  I've had a quick look but thats as far as it goes on that one.


1. PPM is a pulse coded output that holds R/C channel information about servo positions. It is a single pin output that can be interpreted by the filght controller to read the positions of your Radio control stick/switches/etc. What is it for? Well if it is used and you have a flight controller on board, then you will no longer need the R/C receiver, or the R/C transmitter. It will need some small circuit to interface to the output of your R/C controller. We'll be working on that, or users can hack some simple resistors to try it out. The ppm input/output pin is separate to the serial input output pins, and both ports can be used at once.

2. Higher data rates? Well why not, but seriously there may be many people who want this, for example passing low quality video, or just more/faster rate data they want to pass to/from flight controller. Of course there's always a loss of range with higher rates, but usability depends if it is still within your requirements at the desired rate. Encryption? Well I guess just link visibility is an issue for some people.



No PPM is not available on the RFD900+, it is only for the new RFD900x due to be released soon... 

I don't think this will be possible on the 900+ due to size constraints and other issues.




The new modem will be a RFD900x not a RFD900+. The RFD900+ is the existing modem and I'm not completely sure of the state of encryption on that version, but I can tell you about on the RFD900x.

On the RFD900x encryption is 128 bit and will have a slight impact on throughput. It depends on the data rate, i.e. lower rates (4,64K) it will be less noticeable and for higher rates (128-500K) it's in the order of around 10 % of the throughput. Note that the RFD900x is already substantially better than the RFD900+ for utilization of the available air rate so with encryption on it will likely still be better then the RFD900+. More data will be released, hopefully with some actual numbers once the product is released.


Hmmm ... I wonder if Seppo would take a 900 as a trade-in on a 900x ;-)  Kidding! 

Thanks for the info, Kent!

Hi All, 

I got a couple of these RDF900+ radios and they communicate okay to each-other from my copter to mission planner, However, the range is the same as the  3DR radios.

Do I need to change some configuration to accomplish longer range? 

Can they be used with 3DR? and if they do, what configuration should I use?

Picture attached.

Thank you to all in advance for your help.


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