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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Too much problems with base noise using RDF900 as ground radio.

Dear Seppo ,
I have just bought a RDF900 for use it as ground radio and my first tests are very dissapointing because of what I think that is an unacceptable local RSSI noise. Although the mean noise is around 40-60, what is little bit high but between the normal range, as I have readed you in some place (in this or another post, I don't remember), it fluctuates a lot with frequent peaks over 80-100 and it causes a lot of errors and a very short range (much less than expected). I also have have high peaks of remnoise.

Please, find here-attached tlog of a flight and a picture or a graph of radios performance along it.

I have tried different configurations, firmware updating, conections in different PCs or laptops but I still have the same problem and I don't know how to proceed to resolve it.
Next I told you what is my setup:

* Base radio: RDF900 with original dipole antennas (from http://rfdesign.com.au). Firmware updated to SIK 1.9 through Mission Planner 1.2.99 and Default Config. Connected to PC through FTDI usble cable (with a ferrite)

* Air radio: 915Mhz Radio Telemetry Kit, also updated to SIK 1.9. and a ferrite in cables to APM. It is installed in a quad with APM 2.6 and arducopter 3.1. I am ussing 5,8 Ghz FPV system and MinimOSD connected to APM trough an Y cable in the Telemetry port.

I usually set the ground radio over the roof of my car, at a distance of about 1,5 m from the laptop.

So, my questions are:

Could it be caused by interferences with GSM network (Spain)?
Could it be resolved by a different config or by another firmware?

Please, any advice is wellcome


has anyone here used the LC-1000RU transceiver for making wireless connection between PC and arduino . i recently got this device but am unable to get it to work , i need serious help pleasee please if anyone can . i have to use it in my final year project and i have very little time . please help me if anyone can .

Module link: lc1000RU

Dear Seppo or anyone inclined to help,

I've been struggling with this problem for a few weeks now; I have run out of ideas and turn to you for help. 

APM 2.6 + external compass/gps running plane 2.78b
-RFD 900 Telemetry Radios on both sides, running SiK 1.9. 3 DB antennas on the receiving side (tablet/PC size) and stock antennas on the plane.
-1.3ghz for video (800mw)
-ezuhf for control

I've checked the noise levels with all my gear turned on, and I get 20-30 noise readings on local & remote (with about 90-110 value for RSSI)

I cannot fly further than 150 meters without losing telemetry. I've tried changing my AIR_SPEED to 24 from 64, but does not help. I've also tried powering the local radio by USB and external BEC, same results. I have no issues with video or EZUHF; I can go as far as 35 minutes affords me without losing either.

I am using two antennas on both RFD900 radios. I see some people are only using one? I haven't tried single antenna.

Attached are pictures of the RSSI values, my configuration parameters & the plane layout. Any help, input or suggestions would be greatly appreciated.

Thank you!


Dear Raph,

First of all, check your antennas (inside the rubber cover, if possible) and their connectors (if you haven't done it yet). You have very low noise levels but your rssi are not so high for two modules been so close. And 150 m is a short distance for a configuration problem. I had problems like yours before with a 3DR radio set because a broken antenna.

By the way, I take this opportunity to update my noise problems with my RDF900 modules. I reduce noise a bit if I set my ground module far away of my car (more than 3 m) using usb extensions and a tripod.

Surprisingly, my RCtimer ground radio have lower noise levels than RDF900 module when it is placed in the same position (although it have a lower RSSI), specially when they are placed close to my car (in its roof, for example).

RemNoise is also been reduced using this Low pass filter: http://www.readymaderc.com/store/index.php?main_page=product_info&a...

Hope to make more tests soon and I'll tell you if I got any improvement


Thank you for your input! I will check the antennas. Another user said that I have my antenna orientation completely wrong on the plane, which could be the cause of my issues. I have replaced them with 90 degree antennas so they are pointed up (in a slight V shape actually). Hopefully the winds will calm and I can test and come back with results.

I have both RDF Flex1 and RFD Flex2 antenna's. From reading through this thread I see the long thin one [ Flex 1 ] goes horizontal [ I think it would be wise to state that with the product ] . My question is I know the long part should go horizontal however I'n not clear on if the thin way can go horizontal as well. For instance I would like to install it on the bottom of the fuselage i.e. horizontal both ways. Or... would it be best to have it mounted on the side of the fuselage i.e. long ways horizontal short ways vertical. 



Hello Seppo,

Any news on that project to make the RFD900 an RFD868 or 433 MHz?

Thank you,


Hi Rick,

The FLEX1 antenna can be used in both of the cases you describe.  If you have the choice of mounting it on the bottom of the fuselage, or side, - I would go for the side, providing there is good clearance from metal.



Dynamic power control available for Beta testing

It has been a very long time since writing - we have been keeping busy with all kinds of project work and when we have a chance, designing new hardware 

We have some new software features which might be of interest when looking to save power --- Dynamic power control !

When it is enabled in V1.10 (beta), the modems will monitor the RSSI levels, and adjust their transmit power to achieve a target RSSI level.

The details are in the "Software manual", at: RFD900 Software manual (Page 8 has the goods!)

Quick summary:
ATR0=255 (this disables Dynamic power, and sets modem to maximum permissible power set in ATS4)

Starting point values:
ATR0=150 (target RSSI)
ATR1=20 (hysteresis, before a power change is commanded)

It is still in Beta, so if you have a chance to check it out and feedback your comments, it would be much appreciated.


Hi!, Just a quick update - we have a bunch of new cables in stock to connect RFD900, and RFD900u's to both APM2.5 and Pixhawks in stock!  - This should make connecting things up easier :)


I just got my RFD900 modems from JDrones. They are cased in physically different casing than that of rfdesigns versions. And the air module comes with a telemetry cable whose connector does not snug fit the telemetry port on my APM2.5 board. I did not try to push it hard fearing something may get broken. However I was powering my board with usb cable and not by UBEC. Though I could read the ground module settings in config tool I could not connect the two modules in any way. I was wondering whether is it because of apm being powered by usb. Another problem with JDrones modems are, they have no status LED, which leads to confusion whether they are powered on or not. However I still finding ways to connect both modules with each other. Hope I get some heads up from you guys.


You cannot use telemetry if you are hooked up via USB.

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