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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      • My purpose will be to use the tracker for video only, since the RDF900 gives me plenty of Telem range. In that case, it seems it might be more secure to use put the GCS in the middle, so if there is a fault in the AT, the Telem link is not vulnerable. Is this flawed logic?
        • Hello iskess,

          What range does your RFD900 offer with stock Antennaes??

          Also i want to fly my UAV at 20 kms (LOS). What would be the right Antennae setup? Do i need to get a Directional 12 dBi Yagi (I already have the Yagi) with a Tracker??

          Thanks in advance!!

          • I use an RDF900 on the ground and a 3DR in the air with a homemade Turnstile antenna based on IBCrazy's design. The RDF900 has a 8db linear patch (no tracker) and an omni. I haven't exceeded 8km because of my video limitation. At that distance my telemetry was still strong.
            I imagine with a pair of RDF900 and a Yagi you should be able to exceed your 20km goal. Go to Suppo's thread, there are a lot of more knowledgable folks to share their experience.
            • Thanks a lot, iskess!!!

              Will do and let u know!

  • Thank you for the reply
    but i have other problems.
    My tracker is so configured:
    APM2.5 with two servo connected to RC1 and RC2;
    the 3DR radio (id 25) is connected to serial 2 and the PC via USB.
    The vehicle is a Hexacopter with PixHawk V3.2 with a 3DR radio (id25).
    When I connect my pc to APM2.5 i see the tracker with all parameters and it's ok, but when i press ctrl-x i see the hexa but this is the screen(no parameters):


    are there other parameters to set?
    thanks for patience


    • today I retried to use the AT and I have found this procedure to use it:
      I turned on the hexacopter, I have connected the pc to hexa (with 2 3dr radio) then i turned on the AT with a 3rd radio with the same id. AT works in this way.
       However if I do not connect the pc before, the AT doesn't work.
      How do you explain this behavior?
      sorry for my bad english

      • Developer


        Ok, what's causing this is that copter by default only sends heartbeats out on it's telemetry links until a GCS connects and asks for a specfic rate (which you can configure).  The problem is that if you connect the copter later, the MP has already sent it's requested rates to the antenna tracker.  When the copter joins the party it's missed the messages.

        The easiest solution is to set the SR0_, SR1_ or SR2_ parameters on the vehicle's flight controller manually using the mission planner's full parameter list (or full parameter tree).  So for example, if the vehicle's APM/Pixhawk has a 3dr radio on Telem1 you would connect to it with the mission planner and set SR1_POSITION to "5" (or some other number) and press "Write Params" button.  With this done, the next time the copter is turned on it will immediately start sending position information 5x per second.

        • Thank you very much, now the AT finally works.
          I have a last question, if I have a 180 degrees servo for pitch and a 360 endless servo for the yaw, how can I configure them?

          • I could be mistaken but I don't believe the AT is set up to support continuous-rotation servos..

            • According to the documentation it does, but I think it has to be one or the other. Either both are regular or both are continuous.

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