Ultimate LRS : 40 km telemetry & RC link

Telemetry and RC link for APM, Pixhawk, Vector, etc


  • Fly safely with Ultimate LRS

Distance of 40km with vee antenna on plane, and 4 elements yagi on ground station : click here for detailed setup.

Discussion forum on RCgroups is here.


This projects provides drone and FPV flyers with a long range 1 watt bidirectionnal link for RC and telemetry. Use it to replace your other telemetry or LRS systems by a single system having many advantages :


With 1W or power, the Ultimate LRS provides full telemetry and RC control up to 40 km. Check the user provided content page to see many flight videos.

Notice that 40 km is not the limit of the system, but the further a user has flown with it, limited by his plane’s battery range. The system is capable to go to 100 km with good antennas and a sufficient altitude to keep a direct line of sight (earth’s curvature).


The speed of Ultimate LRS allows to make all mavlink operations in the air. For example connecting, modifying parameters in flight, uploading new waypoints, or any other mavlink command.

It not only support the default Mission Planner telemetry speed, but can handle much more such as 10 refresh per second for the attitude and position, giving completely smooth artificial horizon movements.

A more detailed features comparison with 3DR radios is provided here.

Fast RC link & Mavlink telemetry : 72 packets per second

Fast RC link & Mavlink telemetry : 72 packets per second

Unbeatable price

The Ultimate LRS is based on two Hobbyking OrangeRX 1W TX modules (or a 1W module + a 100mW module).

These 1W modules are available for $28.95 each, a total of $57.90 for a complete system, notice that the firmware is completely free.

Complete documentation

The project provides a complete documentation on this site, including clear installation instructions, links to user videos and content, complete spectrum analysis, proposed mods etc.

Active community

A very active user community has grown in this rcgroups forum. Feel free to join the community and propose your ideas and suggestions, or get answers to your questions.

Users have made new 3D printed cases, new antennas designs and videos,click here to see some user provided videos and other ULRS related creations.


The Ultimate LRS is complex inside and simple outside : no technical settings to guess, it’s just plug and play.



Besides the stable version presented on this page, a beta version is currently under testing by a team of 100 beta testers. Some of its features are presented here. It will become an official release around mid-January.

Notice that the Ultimate LRS is only a part of a more complete, that will include a complete  ground station with a 3D virtual cockpit. This is not the latest status, but gives an idea of the features :

Where do I start ?

Well, you’re exactly in the right place :

  •  First, gather material described below, mainly the OrangeRX modules and an FTDI cable
  • Then install the firmware as explained below

That’s it, now take your favourite plane or quad and send your flight videos !







OrangeRX Open LRS 433MHz Transmitter 1W (compatible with Futaba radio)


Mission Planner set-up

  • Connect your APM via micro USB cable.
  • Install Mission Planner from here. This is the link to version 1.3.37 because Mission Planner 1.3.38 has a bug that shows an abnormal number of lost packets.
  • Select the APM COM port and connect at 115200 bauds

2013-11-13 11_56_19-Mission Planner 1.2.80 build 1.1.5016.13386

  • If not already done, install APM firmware.

2013-11-13 11_52_42-Mission Planner 1.2.80 build 1.1.5016.13386

  • Connect.

2013-11-13 11_58_47-Mission Planner 1.2.80 build 1.1.5016.13386

  • Go to full parameter list.

2013-11-13 12_02_25-Mission Planner 1.2.80 build 1.1.5016.13386

  • Click Find 2013-11-13 12_02_36-Mission Planner 1.2.80 build 1.1.5016.13386
  • Search for ‘serial’.

2013-11-13 12_02_59-Mission Planner 1.2.80 build 1.1.5016.13386

  • Change SERIAL1_BAUD to 19 (for 19200 bauds telemetry)
    • (Pixhawk users, please check this page)
    • Notice that SERIAL1 = UART0, SERIAL2 = UART1, etc
  • Write params 2013-11-13 12_05_49-Mission Planner 1.2.80 build 1.1.5016.13386
  • Configure your radio.
  • Configure your flight modes (for example use a 3-way switch, and choose manual, FBWA and RTL modes)

Hardware setup

Firmware setup

  • For ULRS 1.X : Follow instructions on this page to download the ULRS 1.X updater, which will download the latest firmware and flash it on your TX and RX. If necessary have a look at this page to see how to connect a FTDI adapter.
  • For ULRS 2.X : Follow instructions on this page to download an install ULRS CC, which is an administration tool that will download and flash the latest firmware.
  • You’re done ! Double-check the list to be sure you didn’t forget anything


  • Be careful that this system is powerful and requires good antennas. The monopole antennas (such as provided with the OrangeRX and Wolfbox modules) won’t give good results and can sometimes damage the modules. Have a look at this page for antennas recommandations.

Additional information

  • Have a look at the FAQ, it provides many tips on how to improve your range.
  • Have a look at some antenna suggestions.
  • Notice no binding is needed, it just works out of the box.
  • LEDs meaning is the same on RX and on TX :
    • One led means “receiving packet”,
    • The other led means “sending packet”.
    • For example if the TX is connected but not the RX, it will only light up one led (“sending packet”).
  • RSSI is available on this pin on both ground and plane 1W modules (ground and plane): RSSI
  • To connect RSSI to APM or an OSD, use a RC filter (NB : a value of 10k rather than 1k works better, I’ll update this diagram) :rssi-schema_03
  • For the 100mW RX, the RSSI is on the first channel (closest to PCB edge)
  • You can use a long cable to connect the TX to the computer. For example if you have the computer in the car, and want to run a few steps TX in hand to lauch the plane.Two options :
    1. Connect a 5 meters USB cable to the computer, and have the FTDI adapter near the TX. (5 meter is the USB standard limit, else you’ll have to insert an USB hub before going another 5 meters)
    2. or you have the FTDI adapter on the computer, and have a long serial cable. I’ve used 20 meters cable without issues.
  • IMPORTANT : disconnect the USB cable from APM when using telemetry (when it’s connected, APM will default to 115200 bauds and we’re using the same port for telemetry)
  • Remember that the Mission Planner communicates at 115200 bauds with the OrangeRX TX module.

ULRS pinout

Always useful during installation… click to enlarge :


ULRS extensions

  • You could be interested in adding 16 servos to your ULRS (not just having a serial PPM), have a look at this page.




To try out the beta version, visit this page.

2016-01-02 20_10_48-Ultimate LRS Control Center - Version 2.23 Beta



  1. Daniel says:


    Instead a long serial or usb cable, it’s possible connect via a serial Bluetooth?

    Great project, congratulations and thanks for share!

  2. Simon Edwards says:


    Thank you very much for this fantastic work. I now have telemetry working between 2x1W 433 orangerx units and Bluetooth to my computer. Brilliant!

    Couple of questions:

    1. When bound, both units show red and blue lights constantly on. Is this normal?
    2. The setup works great with your firmware. As an experiment, I tried using openLRsng in Google Chrome and flashing “TX as RX” onto the APM TX but without luck. Do you have any ideas why this doesn’t work? No worries if not, just curious.

    I have emailed you a picture of my setup showing the lights mentioned in point 1.

    Thanks again!


    • admin says:

      Hi, yes it’s normal that all the LEDs are ON. Regarding openlrsng I can’t help you as it’s not a firmware I created, the best is to ask in its forum.

  3. Andrew Borntrager says:


    I have 2 orange rx open LRS tx and flashed them with custom firmware. I have the jumper on my APM to activate serial PPM. Telemetry data is coming back fine. I have a regular Futaba rx (PWM) going to a PWM to PPM encoder. The PPM signal then goes to my APM. My apm is armed, and the servos go in a locked positon and stay. I did a radio calibration, and can clearly see my Futaba radio inputs on my Mission Planner screen move perfectly with my RC input movements on my radio. MP lets me switch from manual to RTL or any mode I want. The servos stay locked in place, despite changing to manual mode. The IT Luxembourg site shows the PPM signal from the Orange RX module, not a receiver. Could this be my problem, or is there any way to make this work, or a reason why my setup is not working?

    • admin says:

      If you see the servo input in mission planner, then it’s fine on the radio side. If the servo don’t move, this is typically due to a servo calibration issue or issue with servo parameters : check the RCX_XXX parameters.

      Also check this : http://plane.ardupilot.com/wiki/apmplane-troubleshooting-guide/#no_servo_output_in_any_mode_other_than_manual
      and this : http://copter.ardupilot.com/wiki/common-optional-hardware/common-servo/#testing_with_the_mission_planner

      Hope this helps

      • Andrew Borntrager says:

        Hey thanks a lot! I got everything working fine except for rssi. When I hook it up to analog channel zero and make the rssi value show up on the screen, it always says zero. When I enable the airspeed sensor in MP, the airspeed value goes crazy(which I actually have rssi connected to, so I think MP is receiving at least raw data). Should this be 3v or 5v, and might I need any scaling? Thanks for the awesome setup. I’m combing this with cellular video via a Raspberry Pi.

        • admin says:

          Interesting setup with raspberry pi ! For the RSSI you’ve got to select the pin and activate the RSSI input pin (0, 1 or 13) with APM parameter RSSI_PIN, and select the range (3.3V or 5V) with parameter RSSI_RANGE.

          • steve Sumner says:

            When you setup the rssi cable, do you have to put in the capacitors like all the other diy rssi cables, or is it just a straight cable. Also when I flashed my 2 TX’s last night the one I flashed as TX just beeped and beeped after successful completion of the program, is that normal?
            And one more question I could not find anywhere what the connection between the TX Module and transmitter looks like? does it just plug in like normal or is there some other setup. BTW love your program, so much easier than openlrs. Thank u

          • admin says:

            Thanks, you’ve got to use a capacitor for RSSI, because Atmega can only output a PWM signal, which will be filtered/smoothed to an analog voltage by the capacitor.

            The TX will beep when the RX is off. Normally this is used to hear when a packet or the connection is lost.

            The TX module can simply be plugged in.

  4. lvming says:

    If I have two sets of three OrangeRX equipment to work with, how they do not interfere with each other, thank you.

  5. Jean Joubert says:

    I am trying to get RSSi to work, can you please give more detail on the capacitor to use and how to connect? Have seen various descriptions of doing this but most common a combination of a 4.7k resistor and 10uF capacitor? Presume I have to set the RSSI_RANGE Parameter to 3.3V.

    Thanks again for your work on this system, can’t believe how well this works after I have wasted so much time with OpenLRSNG!!

    • admin says:

      Hi, the PPM pin is already connected via a 1k resistor, so all that’s needed is a capacitor. 10 µF seems a good value, but even lower values should be OK. The capacitor must be connected between the PPM pin and the GND.

  6. Tobias says:

    Hi, this is a great project! Would your code also work on the Hawkeye DTFUHF gear? I have the taranis module and the 9ch receiver. I’ve been waiting for mavlink integration with openlrsng for soo long now and not much progress.. your code seems to be perfect! Somewhere you mention it needs no binding. How does it deal with multiple users at the same time? e.g. when flying with a friend?

    • admin says:

      Hi, I made this firmware because I wanted to fly long range with APM, the goal was to have something very reliable, using a bidirectional 1W link, and able to handle 19200 bauds for mavlink. So far a user took it to 40km, which is pretty good but not yet the limit. The next version will include the ability to select the channels, for now it’s a one-user system.

      DTF UHF compatibility will be included, for I’m waiting for a new DTF unit to ship.

  7. Julius says:

    what a great project, thank you very much for this awesome LRS option.
    However i am stuck for a while now. Managed it to flash two 1 W Tx’s as RX and Tx, normal RC link also works quite good. However iam not able to connect my 1W TX to the mission planner (via FTDI). I think i have wired everything correct, still when trying to connect to the module i get the Message: ”No Mavlink hearthbeat recieved”. My FTDI seems to work, as it is blinking. Somehow my APM fails to send Telemtry over the RX to the TX. 1W RX is connected to channel 1 with PPM jumper in place. TX/RX pins of the 1W RX Serial Port are connected to the APM Telemtry Port, but here iam not sure to which pins one should connect exactly, since there are a lot and your Picture is diffecult to understand since there is no wirking diagram – only a pic with cables running into the Telemtry Port.

    • admin says:

      OK, First check that the baudrate in mission planner is set to 115200 bauds, and in APM to 19200 (19) bauds.

      • Julius says:

        It might be a dumb question of mine, but how does one check this? When connecting via usb the baud rate is 115200 Bauds. And according to your instructions i set Serial 1 Baud to 19200 Bauds. Where do i have to set those (57) Bauds?

        • admin says:

          Sorry, I meant 19200 bauds (corrected in my answer above). You can’t connect the APM simultaneously via USB and via ULRS telemetry : it will automatically go to 115200 bauds as soon as a USB cable is plugged in.

          • Julius says:

            Allright i think i might forgot to make some hardware mods to the TX modules, like connecting the serial tx pin to the rf pin of the module connector – are those mod nessecarry for enabling telemtry on a Turnigy 9xr Pro? And which radio/firmware are you using?

          • admin says:

            I’m using a Taranis, but you can use any RC TX which gives a PPM signal. It just requires to connect the PPM pin, the VCC and the GND. No other mods are required for basic operation.

  8. Oscar says:

    Do you know if the current firware is compatible with original hawkeye (non dtf uhf)? I’ve heard the pcb si very close to flytron or orangeRX.
    Thanks for making mavlink telemetry possible with “openlrs” hardware

    • admin says:

      Thanks ! For now it’s compatible with boards having exactly the same wiring as the original 1W or 100mW Flytron, I don’t think the original hawkeye has the same wiring as Flytron. Next version will be compatible with those.

  9. Joseph Douce says:

    Great project… I’m wanting to to control my milticopter from mission planner via the joystick option. As is described on the 3dr website with the 3rd radios below. Im using a pixhawk. If I set up 2 OrangeRX TX 1W. As described above will this work? I control currently purely from mission planner. I have no rc controller.


    Can I simply replace my 3dr radios with 2 x OrangeRX TX?

  10. Joseph Douce says:

    The idea is to also use the laptop for fpv. Been experimenting with android phone as fpv camera over 3/4g to get away from fpv range limitations.

  11. Lyn says:

    This is a brilliant addition to APM. I have one question, you say you are developing “frequency hopping”. Would it also be possible to allow an option to use 458 MHz as this is a legal rc control frequency in the UK, 433MHz is not!


    • admin says:

      Thanks, yes the frequencies will be selectable within the full range allowed by the RFM23BP module.

  12. Piotr says:

    Hi, it’s really fantastic project, thanks. I flashed Tx&Rx, then connected APM to PC. The RC link works perfectly. Now try to connect the Tx directly to PC via FTDI to check if telemetry is well transferred. Could you please attached the wiring of the Tx – FTDI – PC connection. It would help me and maybe other less experienced people. Thank you in advance and I’m waiting for the “frequency hopping version”.

  13. Arunas says:

    Thank you , great job . Everything work perfect .

  14. Julius says:

    Hey its me again,
    I just want to thank you and let know you that everythings works flawless now. Keep up the good work, I am looking forward to your next software release. Donation granted.

  15. Dillon says:

    Can your firmware also be used on the regular Tx as Tx and Rx as Rx? I don’t have 2 Tx’s but I have a very unreliable link using stock openlrsng firmware.

  16. felekb says:

    Will This firmware work with OrangeRC TX 100mw? I would like to keep the whole radio at 100mW for legal reasons.

  17. Khaled Homouda says:

    Thank you , great job. Just want to clarify: the connection is working RC wise, but, the telemetry is not showing in the Taranis transmitter. The module is plugged in the taranis. shouldn’t it be? as you are explaining connecting the PPM, VCC, and Gnd, does this mean not plug the module?
    the voltage is showing in mission planner, but how do I make it show in the transmitter, and where does the RSSI modified cable with the cap and res attache to other than the rx? does it have to go to the OSD, or you mean it will go somewhere else? Thanks a lot

  18. Saku says:

    Hi, Does anyone have experience using APM Planner 2.0 for MAC instead of the recommended Mission Planner 1.3.15? I’ve been using openlrsng for a while now, but after reading about this project decided today to order skyeye with relevant components to build an UltraLRS plane.

  19. JoeRockhead says:

    Greetings, Could you post the wiring from the Orange to the HobbyKing version of the flight controller (HKPilot 2.7)? Do you connect the Orange to the Telemetry port like the Pixhawk?


  20. JoeRockhead says:

    I have a question about the Mission Planner version. I missed the step about installing version Mission Planner 1.3.15. I mistakenly installed the latest version 1.3.31 (ArduPlane version). Everything seems to work fine with the latest version. Is there any danger running the latest version of ArduPlane firmware? Thx

  21. NEVdD says:


    I am designing long range/long autonomy drones and got quite disappointed by OpenLRSng gitsly branch because the telemetry link is extremely slow.

    A nice subscriber of my YouTube channel recommended me to try Ultimate LRS which looks very interesting!

    Thank you for your work (even though I didn’t test it yet), you detailed every step of the setup very clearly which is really nice! (and provided an updater to flash the Orange Rx system easily)
    Do your system support the serial transfer of the telemetry data to the remote control? (you know, this kind of thing http://www.rcgroups.com/forums/showpost.php?p=26953006&postcount=2802)

    Btw I am based in Belgium so if you want to share some projects or make a YouTube video about Ultimate LRS it’d be nice 🙂

  22. omid says:

    Hi, sorry if my question is’nt so related.
    I want to setup up this project. want to know what is your suggestion for long range video transmitter?

    • admin says:

      I’m using a simple 1.2GHz 800mW transmitter, can’t even remember where I bought it. You’ll find a lot of information about FPV video equipment on rcgroups.

  23. Alfonso says:

    I was wondering, how long can be the ppm cable that goes from the radio modem to the controller?

    i wanted to make a confortable installation, but i dont know if the signal will reach with a 3 or 4 meters of cable.

    Did somebody try it?

    Amazing work!! i cant wait to have the system working.

    • admin says:

      Hi, there are 4 options :

      – I would recommend to mount the TX module close to the antenna, with a FTDI adapter, and run a long USB cable (+ a power cable or use a battery). From its specification USB can have a maximum length of 5 meters.

      – Several users are also using a long serial cable rather than USB cable, but I don’t know exactly their range. With real RS-232 (-12V / +12V) it would be easy to reach several tens of meters, but here the serial signal is only 0-5V. But for several meters there should be no issue.

      – Sending the PPM signal over a long wire should work too, but don’t forget that the pulses are sampled at 2MHz, so it can be sensitive to signal degradation and interferences.

      – Using a bluetooth module can also be an option ( http://www.itluxembourg.lu/site/using-ultimate-lrs-with-a-bluetooth-module/ ), it works well but it seems that the max range of the ULRS is reduced maybe because of interferences.

      • csomyy says:

        I think, Alfonso tries to separate the RC module from the RC transmitter because of some reasons. For example fixed antenna orientation issues. The long PPM cable leads me to this opinion.

        I tried a 2.4–>433 beacon station. 2.4G RC with PPM output. It worked well.
        So you can have your transmitter in your hands, can move freely, and can have the 433 TX module fixed on a pole or in the ground station.

  24. remote_syst3ms says:

    Curious, About setting these up for serial link only. I do not fly.. I only am looking for a low cost full duplex wireless serial connection. Is there a TxRx passthrough that can be used to Transceive? I’m trying to have long range sensors on cameras, that commands can be sent to the cameras through the OrangeRX.

  25. Alfonso says:

    Thanks for the response!!

    I was thinking about making a small electrical box under my pan&tilt antenna. From this “box” i would pull out:

    1) USB cable to the computer
    2) PPM cable to a joystick (radio W/O module)

    and I was thinking about giving 3-5m of lenght to this cables to make a comfy installation. Before doing the bundles, i was wondering if anybody has done this with good results.

    Thanks again to the admin.

    Changing the subject, another idea that occurred to me that could be done with this project was trying to enable the MIMO capabilities that i think the original hardware is supposed to have, creating a diversity system. I think i readed something like this from the radio that orange use.

    Im talking w/o any knowledge about how complicated will be to achieve this.

    • admin says:

      Yes it’s a good idea to keep the module close to the antenna, and just have a PPM and USB cable going out. The officially supported USB max length is 5 meters and I’ve already used such a cable with good results. For the PPM, I don’t know exactly the limit, but a friend of mine was using about 3 meters without issues. Notice that it’s also possible to use Bluetooth as documented on the site.

      If I’m right the RFM23BP modules aren’t able to do MIMO, but the chip which is on the module is able to do diversity. However, the module RFM23BP connects the chip in a way that disallows the native diversity. However by having to OrangeRX modules it’s possible to make diversity by software, I’m working on this for a future release.

      • Alfonso says:

        you are right. I must have misread the MIMO capabilities of the module.

        Thanks again for the info!! i might do the cable 3M long for starting. i was thinking not to use Bluetooth in order to make it simpler, but it is a great idea though.

  26. Sette says:

    I have manage to display the status rxrssi in Mission Planner, and it works great with the LC-filter, but has anyone manage to display the same rxrssi parameter in latest verison of Tower?

  27. shelly316 says:

    Can You please make support for 100mw orangerx tx modules

  28. Balázs Orbán says:

    Recently I have flashed 2 OrangeRX 1W Futaba style modules with your software as RX and TX. It seems to me that the bind was successful, The TX is beeping probably proportional with RSSI, the leds are blinking on both module. I would like to test the telemetry with two FTDI modules using two separate serial terminal windows. The Baud rate was set to 19200 on both terminal windows, but I am receiving wrong data in both directions. Are there any special settings on Parity, Stop bits, Data bits other than default 8N1 setup or some handshake protocol is used?

    • admin says:

      Yes it’s possible to use it as a radio modem, but notice that the TX must be connected at 115200 bauds, and the RX must be connected at 19200 bauds. Of course be careful not to send data at more than 19200 bauds (even on the TX which is connected at 115200 bauds). But if using with two putty consoles for example, it can be used as a chat for testing.

  29. Daniele says:

    What bout connecting the ppm pin via 30 meters of ethernet cable to an orange module on the roof? I ve tried it just yesterday, it works, but i m not sure of its reliabilty. Is there anyone more expert than me that wants to share some suggestione?

    • admin says:

      It’s OK, especially with ethernet cable. If it’s too long you’ll notice some imprecision in the PPM or issues with the serial connection. I don’t know the exact maximum length, but as long as it works don’t worry 😉

  30. bahadir says:

    can i use ultimate lrs modded hk modules with arkbird or rvosd?

    • admin says:

      Hello, you can use it with any system that use a serial communication at 19200 bauds. If this baudrate is supported by rvosd or arkbird it will work.

  31. MONTILIEN says:

    Congratulations for your very nice work…
    Is it possible to setup in the 868Mhz band?
    I have developped a 30dBm module in this band based on Flytron V2 receiver. I will post the pcb files as soon as all tests are OK..
    Best regards

  32. Doug says:

    Does this work with the 2.4 GHz modules?… I am in North America

    • admin says:

      Unfortunately this is made for the RFM23BP modules, which are 433MHz modules. There are no exactly equivalent chip in the 2.4GHz band.

  33. Vedant says:

    Will there be any issue if two persons are using the UltimateLRS System at the same time?

  34. Venelin says:

    I tried to find an option for diversity receiving by the receiver side. But I can not find such an option. As is well known the diversity receiver improves overall by three dB receiver’s sensitivity, when the antennas are properly located.
    Do you have plans to implement such a feature in the future development?

    • admin says:

      Yes, HopeRF (manufacturer of the RFM modules) is even talking about a 6 dB improvement, that would double the range. I’m working on it, in an implementation involving two modules talking to each other via I2C.

  35. Tomoko says:

    If you are interested in topic: earn online money by typing
    download lessons – you should read about Bucksflooder first

  36. Fernando P says:

    Hi, thank very much for the information!!!the page is excelent!. I´m thinking to buy the WolfBox 1w module or the orange 1w, my tx is a flysky fs-i10 and don’t have for modules change but in rcgroups I see this: http://www.rcgroups.com/forums/showthread.php?t=2327457 . Doing that. Do you think this module can work with my tx flysky?.

    Pd: sorry for my bad english

    Thanks, From Argentina

Leave a Reply

Your email address will not be published. Required fields are marked *