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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  • What are your PID values?

    I upgraded from position YAW servo to continuous rotation but I think my gains might be a little low.

    Also what does the I term do for yaw or is it turned off in the firmware.

    V1.0 firmware - So it seams to be a fairly good version.

  • I meant to say the SR1_Position param.

  • I managed to figure my issue out.  It was not making any attempt to track the quad because of the SR0_Position setting.  I changed it from a 2 to a 3 and now it is tracking pretty well.  

  • I finally have all the issues worked out with my tracker except one, and was wondering if anyone has any ideas.  Basically the tracker does not track the copter in auto mode.  For example, the copter is due east but the tracker remains pointed south. The red directional line for the tracker says it is pointing south in Mission Planner, so it knows which way it is facing.  Mission Planner also recognizes that the copter is due east.  For some reason it does not make any attempt to point the red line towards the copter.  

    I am running v1.0 at the moment, but had similar issues in v.0.8.  Has anyone else run in to this?



  • DougB said:

    I'm going to purchase a "BM-785HB Servo Gearbox".

    What gear ratio is recommended?


    I guess it all depends what you're going to do with it.

    If it's for tilt, you probably need a bit more power, for yaw maybe less. But if your AT is very heavy, you may choose higher ratio.

    I 3D printer the gears myself and balanced the pitch. Yaw has 2 bearings, so hardly any force is on either of the axes.

    I use metal gear servos, 11kg and modified the yaw to continuous rotation. My gear ratios are about 1 to 5, so I get roughly 55 kg/cm.

    But then again, I balanced everything, so the power is only needed to start motion, not to lift weights.
  • I'm going to purchase a "BM-785HB Servo Gearbox".

    What gear ratio is recommended?


  • Hi Anthony,

    Pulled the APM out of the plane and replaced it with a Pixhawk Mini.  APM now in tracker and we're almost there. Mission planner is correctly showing position of Tracker and Aircraft, haven't quite succeeded in getting the red line to slave to the orange just yet.

    APM 2.6 with tracker V1.0 (No clue as to how to get 0.8)

    Bluetooth from PC to tracker, RFD900 tracker to target.

    360 continuous pan, feedback pot on the pitch 10 allows for approx 100 degrees.

    Extended tuning seems to work the range just fine, scan seems to do make it do it's thing and I assume auto is the where the magic happens when all is well. Will post when I figure out how to make it well...


    Anthony Verloop said:

    Hi Rico,

    Many has changed since APM, you'll be surprised. Best thing to do is connect the AT to mission planner, select Antenna tracker from the drop down box in the upper right hand corner and look at the error messages you get.

    Don't forget to do your accelerometer and compass calibrations.

    The AT firmware is a bit tricky, but once you've got it working, it's flawless.

    Good luck.
  • I installed a new Pixhawk but need advice on yaw setup. I have a position servo setup to turn the tracker 360 degrees. The problem is when I fly by the back side it hits the limit and does not swing back to the other side to pick up my airplane. My old setup worked so I must be missing some configuration parameter.

    If I fly back around so that the error is less than 180 degrees it swings to the airplane and continues tracking.

    I just thought of something. Maybe having the rotation angle set to 360 degrees is the problem. I wonder if setting it to less than 360 would fix the problem. Maybe I will try that in the morning - do you think that will help?


  • What's wrong with V1.0 and why have they not fixed the problems. Do we all need to complain on the other forum or what?

    Anthony Verloop said:

    Mike Mac: Version 0.8 (and other previous version) work with 360 degree servos on yaw. Stay away from version 1.0. I'll share my parameter file shortly.
This reply was deleted.


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