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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    • Enes connect a external BEC to the 900 and see if the voltage come up to 5v, the way you have it connected it is dropping the 5v coming from the APM.

      If the Red light stays on solid after connecting BEC you most likely will have reflash the firmware, I had to do that on both of my 900's.

      From looks of your wiring diagram, you are having your APM supplying to many different 5v connections which most cases it's dropping your 5v to 4.2v .


      • Hi James,
          I tried your advice. When I connect to external BEC to the 900 I read 4.99v from multimeter. When I connect  the healty telemetry this value is 5.11v. If I nothing connect to 5v BEC voltage is the same 5.11v

        Red led low light  (same)

        I don't understand whats the wrong?

        • Any electronic circuit that is working normal will have a 10% fudge factor of 5 v , so your circuit is showing that it is working normal. If you had a short it would be much less.

          The reason your voltage intially drop to 4.2v was the APM couldn't handle the load.

          You have what is known as a Load and no Load voltage drop when you connect the 900.

          The BEC will show a no Load voltage reading of 5.11

          When you connected the 900, you got Load voltage of 4.99v that is only a .2 tenths drop in voltage and that is within the 10% fudge factor.

          So to put it in simple terms your 900 is OKAY!!

          Is this a Base Station or a on board the Drone?

          The cable that came with the 900 is most likely wired correct.

          The cable that you have for on board the Drone to the 900 is a different thing , you said you have a APM

          I will upload a picture of the wiring for a Pixhawk to show you how the on board cable should be wired.

          The +5v and -Grd from the BEC goes to pins 2 an 4 the 900.

          You will see in the Picture a +5 and ground - from the Pixhawk, be sure that the -grd wire is connected to pin #1 on the cable going to the 900. Don't connect the +5v wire from the APM to 900 elimnate this wire, just tape it up. The BEC will be handling the powering of the 900. I have a Separate BEC powering the 900 on the Base Station and a separate BEC powering the 900 on the Drone, the APM cannot handle the +5 load to power the 900

          The reason for connecting the -grd wire only is to make sure that your feeding the 900 to a common ground with the rest of your Drone.

          If all the wiring is all correct at Drone and Base Station and you get a solid Red on the 900 check for a Firmware upgrade.

          The six pin cable on the Drone to 900 are different on other Flight Controllers.



          • ... Thankyou so much James for helping out with questions on the RFD900's - It is really appreciated !

          • Hi,
              I am understand you clearly and I tried your all wrote things but nothing change. Yes I don't connect red (+) cable. This broken rfd900 on a plane also I tried ground station on netbook.

            When I connect to ground station telemetry (healty one) from bec voltage is 5.11 like undoad voltage but if ı connect to broken telemetry (on plane one)  voltage is 4.99. I think it seems some problem but I dont now what is the problem.

            This monday I wil go to electronics repair shop. Maybe he understand whats the problem.

            This telemetry really amazing product.But 900 price expensive for me. $ is expensive in Turkey.

            I was fly 10.3 km  and the telemetry's rssi value is %65. Really good value.


            If I can't fix this problem maybe Seppo give some advice or help me. I belive :)

            • Your Quote;  When I connect to ground station telemetry (healty one) from bec voltage is 5.11 like undoad voltage but if ı connect to broken telemetry (on plane one)  voltage is 4.99. I think it seems some problem but I dont now what is the problem.

              4.99v is OKAY.

              Are you using separate BEC on (on Plane one) or are you having voltage from APM to power the 900 ?

              If so,  that tells me the APM can't handle the load and your going to have to use a separate BEC to power the 900 on Plane.

              Another thing Enes, when your trying to communicate to Plane from Base station, you are going to have to move the Plane at least 30 meters from Base Station.

              When you have two 900's close together,  they won't communicate with each other. 

              • ''Are you using separate BEC on (on Plane one) or are you having voltage from APM to power the 900 ?''

                Normally I'm using APM to power the 900. Now if I connect to broken telemetry to Apm only Apm power led (orange or yellow one) on. Ezuhf rx, gps etc. is not working. If I disconnet to broken telemetry to apm everything is ok.

                When you write seperate Bec (5v) i tried on apm and ground station. Yes I disconnect red (+) cable. Telemetry is not working. Yes when I powered seperate bec 5v to rfd900 apm, gps, ezuhf rx etc. all system is working but telemetry is not working.

                • Hi Enes,

                  Sorry to hear you are having some trouble!... - How did your visit to the repair shop go?, were they able to confirm the setup was OK?

                  Firstly, if a modem has a red-led by itself, the modem does need to be re-programmed.  This happens on a small % of units, which we have not found the issue behind yet.  Reprogramming the units fixes it and they remain OK.

                  You can download the latest modem tools, and latest firmware at the following link:


                  If a modem has a red-led it would need to be forced into bootloader mode manually, then upload firmware.  To do this you need to short pin 1 on the 9 way header to ground when you apply power.  It is next to the label "BOOT" on the 9 way row of pads.  Then, upload firmware using modem tools.  The RFD900+ modems need the "900p" version of firmware.

                  When the modems are normally working, you should see a blinking green LED for few seconds while it synchronises, then, solid green LED when it has connection between 2 modems.

                  You can also test if a modem is working correctly ( in terms of physical damage dragging rails etc) by swapping them between the ground and air side, as there is no difference between them.

                  It would be worth knowing if there is any difference between them when you swap them between air and ground station.  Let me know how things go.


                  Home | RFDesign Files
                  Here you will find Supporting files, Binaries and Tools to use our products
                  • Hi Seppo,

                    I go to repair shop yesterday. He examined rfd900. But he dont find the problem. He said maybe telemety's chip is burn. Because when we connect to power the telemetry, chip is little warming up. I order to a new chip from aliexpress. Si1002

                    Can we upload a firmware new chip?

                    Seppo I try force boot but nothing change. Computer can't see telemetry and ı can't upload new firmware.

          • I'm using a RFD 900 and an APM 2.5.  The RFD 900 is set at one watt and I have no problem with the APM powering it.  Just so you all know.


            David R. Boulanger

This reply was deleted.


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