Servers by jDrones

Controversy --- does the AT (v1.1) project work

Hi Greg,

Thank you very much for your reply. I once thought of contacting you for help after reading your thread “Mini Ardupilot Antenna Tracker”.

I changed the pitch PID values according to your recommendation, and also tried both “0” and “1” for the SERVO2_REVERSED value(Servo 2 is for pitch). Both did not make the pitch servo work in SITL mode. At one time, while decent during landing(SITL), the tracker pitched up and down violently. But I can’t reproduce it.
“Using the compass on-board the Pixhawk”, I suppose you meant the built-in magnetometer inside the Pixhawk. I have been using the built-in mag for a long time until 1 week ago when I exhausted all the ways , then I decided to try an external compass, as suggested in another thread saying mounting an external compass along the pitch axis makes it work.
Regarding losing satellites when plane flies overhead, do you mean when the plane flies overhead, the antenna , and thus the tracker (with the GPS module mounted on top) points vertical up, the GPS thus faces sideway or horizontally, and loses satelites ? If yes, this makes sense.

I admire you guys who succeed in making the tracker work. With the yaw working, It seems I am not too far from success. But I have to keep on trying. Meanwhile, if you think of any clue, please let me know. Really appreciate your assistance in advance.

Yes, the compass and magnetometer are the same. Using the one on-board the Pixhawk allows you to mount the GPS (which usually also has a compass on it) to an area that always faces the sky. Make sure that only the on-board compass is used. You could even disconnect the I2C wires to the GPS if it also has a compass.

Yes, that is correct.

Some things to test.
I see that your pitch values are below.
Try changing PITCH_MIN to 0 as a test. It is one difference between my working setup on yours. Perhaps there is a bug.

Try swapping your Pitch Servo2 settings from
to this
You may need to then change the SERVO2_REVERSED setting but use the SITL vehicle connection to verify which is correct. I assume that your SERVO2 settings were derived from using the Test buttons and sliders on Mission Planner. Also, as a sanity check, verify that your Pitch servo works correctly using an external Servo Tester. If you can control the Pitch properly with a Servo Tester, then the Pixhawk should be able to control it.

Another difference in your setup is the Pixhawk orientation. Perhaps this may cause an issue. Both of my working Antenna Trackers use AHRS_ORIENTATION = 24 for Pitch 90 degrees. Your setup uses AHRS_ORIENTATION = 0 for None. I have never tested this configuration.

Good luck!

Hi Greg,

I tried all your suggestion, include changing PITCH_MAX and PITCH_MIN, swapping Pitch Servo2 settings, and then based on these settings, tried SERVO2_REVERSED for 0 and 1.

For all the above trials, I hold 1 param fixed, and change the other 2 in turn. So all the different combination of these 3 parameters have been tried. None of these combinations made the pitching work. The most I got is the sudden pitching (thru a large angle of 30-40 deg) of the tracker during landing mode (SITL) of the simulated vehicle with some of the combinations.

I also changed the AHRS_ORIENTATION to 24 with each value of the above 3 parameters. It still did not help.

As I do not have a servo tester, I tested the pitch servo by controlling it using the knob of my transmitter, and it works and rotates proportionally according to my turning of the knob.

Have several questions :–

  1. Why do you think of setting AHRS_ORIENTATION to 24, instead of 0 (for none) for your workable trackers ? Since according to wiki, if you mount both the controller and antenna pointing forward, the orientation should be 0.
  2. The pitch servo rotates about 135 deg (after modification with addition of resistors) as witnessed in the earlier test with the transmitter knob. At what angle should we engage the servo output spine to the stationary servo horn, so that the rotation of the tracker will not fall outside the 135 deg range in my current testing and tuning stage ? To find out if the tracker pitches (in case it works), I left the servo horn screw out so I can disengage the servo from the stationary horn from time to time during SITL, to check if the output spine is rotating.
    This query also applies to the yaw servo.
  3. Right now, the yagi antenna is not connected to the controller during testing. Does it matter ? There is only one pair of telem radio connecting the controller to the MP in laptop. And the tracker yaws.
  4. If you are familiar with SITL, did you encounter the experience that the tracker still yaws even though the vehicle in SITL is disarmed and disconnected ? What is the reason ?
  5. For the Altitude Source in the Extended tuning page, is there any difference between GPS and GPS Vehicle ? I tried both in SITL with the same result.

Thank you once again for your help.

This was only mentioned as a difference between my working setup and your non-working setup. Changing the AHRS_ORIENTATION to 24 will not have the desired effect without also changing your Pixhawk mount to 90 degrees.

Although this is a nice piece of test of equipment to have, especially one with a digital display of the PWM value, you can also use the monitor screen function on your transmitter (if you have one) when testing the servo movement with a receiver output.


When using Auto mode, the tracker attempts to track the vehicle, scanning if it ever loses contact. Simply press the hardware safety switch to stop it.

I don’t know the difference. I have ALT_SOURCE set to 0.

To set your max and min values, I use either a servo tester with digital readout or the Servo Test setup on the Extended Tuning page.

Hi Greg,

Thank you for your answer to my questions.

I did some field testing with the tracker over the weekend. Pitching still not working.

For yawing, the tracker yaws opposite to the movement of the tracker. This opposite movement did not happen before.

I then reversed the yaw servo in the Full Parameter list. But that did not help.

The way to make the tracker works seems to be a trial and error method.

Will let you know if I have any breakthrough.


Hi Frankie,

You are definitely having some odd problems that I have not seen before.

For my first Tracker, I essentially copied Randy’s project which is described in the WiKi. It was built several years ago and is detailed here. We all use the EZTracker which was sold from ReadyMadeRC at the time. I recently updated the Pixhawk firmware to v1.1 because it had the fix for the Battery Monitor…which I had been waiting years for and was very happy to use it. It still works great using the SITL vehicle connection from Mission Planner. Our flying season hasn’t started yet so my plan is to test it more this summer.

My second tracker was a quick build designed to be a smaller table top version using the inexpensive LOBOT 2DOF PTZ parts and servos along with some smaller components. It was essentially the same type of tracker as my first one where the pitch ranged from 0 to 90 degrees and the yaw was 180 degrees. This limitation is designed around a typical AMA flying field where we never fly behind ourselves.

My point here is that I can only confirm that my one type of tracker works. It might be a good test for you to initially try the same setup and see if you have some success. For the testing, you can simply remove your yagi antenna and stick with initially just testing the tracker. Use a servo tester or receiver to validate the servo positions against the SERVOx_MIN and SERVOx_MAX settings. Depending upon the servo used, the PID settings may need to change from the default settings below.

Good luck on your future testing!





Hi Greg,

Really appreciate your continued support on my AT project. With your assistance, I am determined to make it work since I have been spending over 2 years.

Yes, yagi has been removed sometime ago.

I am changing the values according to your suggestion in the full param list and use a trial and error approach. Initially it does not work. Wll be holding 1 param value fixed, and changing the others one by one, including the servo type.

Your AT0.80 indicated you chose POSITION for both servos. Some people in the forum suggest yaw servo has to be set as CONTINUOUS, and pitch servo as POSITION, and they said it works. I am confused. What is your opinion ? Can you also give details of the servos you use,

including any modification to continuous rotation, if any ? I modified my pitch servo to rotate 135 deg.

Meanwhile, did you try before simulate landing the vehicle in SITL, so as to test pitching of the tracker ? Do you think this is a good way ?

From your experience, if the tracker has reached its preset yaw range limit, will it yaw in opposite direction ? That is the hehaviour of my tracker in SITL.

The video of your first tracker shows you are also using the Eagle Tree tracker sold by Ready Made RC, same as mine.

When your vehicle is on the ground, after power up everything and safety button pressed, does the tracker and thus the

controller turn to vertical position, accomodated by AHRS Orientation: 24 ?

Other than the yawing behaviour which works from default values, i am satisfied with yawing, and I now focus mainly on the pitching of the tracker. I have changed the values of ALL relevant param without success.

Will let you know the result in few days after I finish all the trials.

Thank you.


Set the AHRS orientation so the HUD moves as a copter would with the ‘pointing’ direction. And set the servo types to the types of servo you have. I would suggest setting the pitch P and D gains to zero. You can then just use the I gain to very slowly move in the correct direction tracking a static or very slow moving thing initially. You can then use the GCS_PID mask to work out the gains. If this is not working post vids and logs and I will see if I can work out what to do.


I would follow Pete’s instructions. Also, when you post the .bin log, please post an image of the current setup.

Yes. Also use the on-board compass.

Yes, I found it best to use SITL in two ways. Put the plane or VTOL in Loiter mode in a large circle so that it goes just on top of the tracker. In this manner, the tracker is tested in both yaw and pitch modes. I also use the Guided Mode feature to fly the plane across the tracker path. See Rolf’s post #4 in my mini Tracker thread.

For my trackers with limited pitch (90 degrees) and yaw (180 degrees), I use Position servo settings.

Hi Pete,

Thank you for your opinion. For the orientation, all the time(except just recently, I changed AHRS Orientation to 24),

I mount the controller pointing forward, and the HUD responds as the copter would (controller pitching up, HUD moves to

more blue, less green, and vice versa), and AHRS orientation is set to 0 (none).

As I have no background in programming, I will google the meaning of masking and bit masking to try the GCS_PID mask param.

Will try all your other suggestions and let you know.

Thank you.

Hi Pete and Greg,

Testing on the tracker has to stop as I run into problem with SITL software that after launching, the quad appears in Australia in MP map with “green tear drop” next to it. And the quad would not move after I arm it and takeoff, as I live in Vancouver, Canada where I set home.

I have tried many different ways to make it work again, but no luck.

What is the best category to post the SITL related question (I have more details) in the forum ?

I saw that happen too. I figured it was Tridge’s house. :wink:

Simply drag the quad back to where you live and set home again.


HI Greg, Pete,

Good news. After I managed to set the tracker “Home” and continued more testing, the tracker started to pitch

when I put the quad in “Circle” mode in SITL. Pls find attached the param values of my setting which works.

Greg, some questions on SITL. You once suggested me to put the vehicle in LOITER mode in a large circle to test both yaw and pitch.

  1. Could you tell me how to do this in MP ?

  2. Also when I put the quad in CIRCLE mode, it only circles 2 times and then crashes and disarm. Why ?

  3. When I land the vehicle, the altitude decreases. Why did the tracker not pitch ?

  4. When I disconnected the GPS from the tracker, the tracker also yaws. What role does the GPS play ?

There are more tuning to do. Will do field testing later as weather permits.

Thanks for all your and Pete’s help so far.


Param__pitching works.param (8.45 KB)

The trick came from Rolf in post #4 of my mini AAT thread here. You use a quadplane in SITL and load a simple 3 step mission to get started. Simply set AUTO mode and ARM, then use the GUIDED mode Fly to Here with a right mouse click. The QP will loiter at the WP or you can set LOITER mode and change the radius as shown below.

I’m not sure about your other questions…

Hi Pete,

In my last message to you and Greg, I told the good news that my tracker started to pitch, but further testing shows

the tracker pitches back and forth, as shown in the video with link below.

You asked the log in earlier message. I don’t have the log available as I found out the SD card slot of my tracker controller
(Pixhack, same as Pixhawk)
is probably damaged, and I can’t insert the card. I will figure out what to do to get the log for analysis.

I resend the param file of my current setting to see if you can figure out why the tracker pitches back and forth.

Another point which puzzles me : 10 seconds after start of the video, the tracker sudden beeps, and the green LED turns from solid to blinking, meaning disarmed.
Even though it disarm, the tracker still pitches and yaws.
This disarming started to happen 2 days ago. I swear I did not change any param value. It just happened by itself, and is repeating everytime several seconds after I press the safety switch to arm.

But wiki says "
Flashing green: Disarmed (ready to arm), GPS lock acquired. Quick
double tone when disarming from the armed state."

And if you turn on the loudspeaker, you only hear one short beep at 10 second, instead of “Quick double tone”. Do you have any clue ?

Greg, thank you for advice on putting the QP in loiter mode. One point I am curious, does disconnecting the GPS from the tracker disable

the tracker ? Also does it make any difference to tracking with GPS 3D fix and without 3D fix ? It seems the tracker still moves even I disconnect the GPS from tracker.

Thank you for your help.


Param__pitching works.param (8.45 KB)

The telemetry lost and found sounds used to be these. I can’t remember if this has changed.

  • Telemetry Lost = 1 short beep (like your video)
  • Telemetry Found = 1 long beep

I would expect it to disable the tracker but it may be an untested corner case.

Again, I would expect the tracker to stop or go into scan mode. It’s probably another untested use case.

Thank you Greg.

In the video of your
first tracker, where did you buy the white rectangular patch antenna
mounted on the other side of the controller ? Could you give me the
details? My DIY yagi is not portable compared to yours.

Since you have
experience building 2 trackers, did you encounter violent twisting
(yawing left to right, and right to left quickly and in small
angle) as soon as the safety switch is pressed ? This annoys me very
much and happens 5-6 out of 10 times, and I have to unplug the power
immediately to stop it. Could it be due to certain direction I fly
the vehicle in guided mode relative to the heading of the tracker, or
reflection of radio wave indoor ? Pls share your experience.

In your last reply,
what is the meaning of “untested corner case” ?

I put the tracker on a
tripod just 1 meter away from the laptop which runs SITL. The minimum
distance I set to track is 4 meter. Is this setting irrelevant while
running SITL ?

There is no quadplane
in 'Simulation” page. Do you mean multitotor which I have been
using all the time for SITL testing ?

Still figuring out why the tracker disarm shortly after arming and safety switch pressed. Disarming is followed by the green LED of telemetry radio starts blinking (solid green means radio link established). Any clue ?

Thank you,.

Both of my AATs use the ImmersionRC (IRC) SpiroNET 5.8GHz 13dbi LZR Patch Antenna. It is sold in many places and has come way down over the years so I picked one up at in the U.S. for $25. Just do a Google search for it.

This may be due to your YAW_RANGE setting. Mine is set to 180 since I will never fly behind myself…only 1/2 of a circle or 180 degrees.

The minimum distance to track is from the AAT GPS position and vehicle GPS position, not the laptop location. A setting of 4m is too close for real operation. Use the default 15m or longer. I use a dual receiver so that the omni-directional antenna can be used if the directional patch antenna is in error when the plane is too close and travels across the field to fast. This can occur on a normal AMA flying field.

Select “quadplane” in the Model pull-down menu. See the image below.

Use the settings below on the SiK radios. Ignore frequency boxes if you are using 915MHz.

Hi Greg,

Thank you for your continued support.

Before solving one problem, another problem appears…that the telem radio link dropped continuously everytime

during testing. I have changed to your setting on the telem radio and tried, but did not fix the problem. In fact, my original setting was working perfect consistently before this happened.

I just posted this problem in greater details in a new thread in Antenna Tracker, hoping someone with similar problem can share the experience.


I would make sure that both air and ground modules have the same settings and are not too close together. If they still do not work properly, swap out the module, one at a time, with a different set, if you have one.

On both my AATs, I use 915MHz for the vehicle telemetry link and 433MHz telemetry for the GCS telemetry link. This dual-band operation seems to work well.

Servers by jDrones