figuring out the Antenna Tracker

3691139590?profile=originalNot many people know but we have an piece of open source software for controlling an Antenna Tracker.  It's been built by Tridge (Arduplane lead developer) for use in the outback challenge.

Sadly we have no documentation and, as far as I know, nobody except Tridge has used it.  Still given Tridge's track record on building great software I suspect it works well and if it doesn't, I'm sure we can fix it.  So to not let this piece of code go to waste, I'd like some help from people who are interested to give it a try and help me figure out how it works.

Here's the little that I know:

  • It runs on any of our supported board (APM1, APM2, PX4, Pixhawk, Flymaple and perhaps VRBrain)
  • For APM1/APM2 users building the code is as easy as opening our hacked ArduinoIDE and selecting File > SketchBook > Tools > AntennaTracker and then building in the normal way.  For PX4/Pixhawk, our autobuilder doesn't automatically build a binary but I can provide one if people are interested.
  • It can control a Pan and Tilt gimbal like this or this found on
  • It may or may not require a GPS
  • It must somehow receive vehicle position updates from the ground station which has the telemetry radio that is connected to the vehicle. Maybe through a USB cable.  Tridge probably uses the python ground station, MAVProxy, to passthrough the vehicle position data to the AT but perhaps we can get MichaelO to build out a similar feature in Mission Planner.
  • I imagine this antenna tracker could also be used to keep a camera focused on the vehicle which might be good for easing the burden on creating videos of our vehicles.

So if you want to give it a try please do and stick any findings, questions or issues below. Alternatively Issues can go into the issues list.

I'll start sticking things into the wiki as they become clear.

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                  • Love the video, nice job! 

                  • I tested the new v0.8.0 of the APM Antenna Tracker which included a new filter to smooth input to the controllers. It worked great for both APM Copter v3.3.3 and APM Plane v3.2.3. My ALT_SOURCE parameter was set to use GPS.

                    My tracker uses an EZTracker with extra side car from ReadyMadeRC, a long range RDF900 telemetry unit and an ImmersionRC DUO 5.8GHz receiver with a directional and omni antenna. The extra side car acts as a counter-balance and a spare battery holder.

                    I posted my param file for those that are interested...

                    APM Antenna Tracker v0.8.0 from Gregory Covey on Vimeo.


                  • can you try and reset the defaults in mission-planer an tell me if it still works after it reboots ? 

        • Developer


          Some more details of what's not working would be helpful.

          Still, the improved logging helps see what's going wrong.  Pitch control is basically working but the gains are too high so you should try reducing PITCH2SRV_P from 0.2 to 0.1.


          Yaw control is pretty messed up though.  Can you try reducing the gain YAW2SRV_P from 0.2 to 0.05?  Maybe reduce the YAW2SRV_D from 0.05 to 0.01.


  • Hi Randy, a few quick questions: 

    1. If apm2.6 or another board with NO onboard compass is used like miniPX4, can the compass be on the yaw only part of the tracker, or should it be on the same platform as the main board? 

    2. Also, is it possible to duplicate pitch servo on any of the available PWM outs like it is possible with multiesotor outs?   


    • Developer


      1. An external compass needs to move in all axis with the board.  We re-use all the same logic as we have for copter, planes, etc, so the EKF will get confused if the compass doesn't move with the main board.

      2. I'm afraid it's not currently possible to duplicate the servo output.  I guess you could use a Y cable to split the PWM output?  It's not a big amount of effort to duplicate it in the code.. but I can't promise when someone would get to that.

      The next priority for me is actually for my new employer, EnRoute.  We're planning on putting together a tracker that can communicate using a Wifi connection instead of a 3DR radio.  To do that we're going to swap out the Pixhawk for a NAVIO2/RPI2 board.. because I think it'll be easier to set-up the wifi connection that way (using a separate Wifi dongle).

      Anyway, thanks for all the testing and feedback people have been doing here.

      • Understood. Thank you! 

        Splitting pwm is an option thus is what I do right now along with servo reverser as I am using two pitch servos in mirror position.  Why it would be usefull to split pwm out is to account for difference in center pwm frequency of each servo (many time it is mechanically impossible to align two servo arms due to the differences in spline teeth positions, adjusting center of each servo independently would allow for absolut alignment via software. 

  • help 

    well today i took out my tracker and my quad not good day

    i was playing around with the setting on the tracker went to write the pram 

    it wrote the pram to my quad i watch it drop 20 meters to its death 

    is there away to check its writing to the tracker not the quad in mission planer

    • In the right hand upper corner of mission planner, there is a drop box for com port and baud rate. Just underneath that, there is a drop box called "Stats".
      That's where you have to select the antenna tracker. By default, it is showing the vehicle, not the tracker. So by writing your parameters, they will be written to the vehicle. After selecting the antenna tracker, the parameters are written to the antenna tracker.
      • yes it was on the tracker that's  what i cant work out 

        just done some testing found a bug in mission planer when your in full list of the prams and click on restore to defaults it reset all it can see LoL so reboot the quad as well

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