The expensive but attention grabbing Antenna Tracker

I just returned from the UAV Day @ The Fleet Center here in San Diego. Quite a few folks swung by the San Diego DUG table and asked about the antenna tracker I built. Joe Aletky from 3d Robotics asked me to share the build of material for the antenna tracker. There's the Antenna Tracker wiki but I wanted something a bit heavy duty for the field! 

The parts list is mostly sourced from ServoCity and cost me about $200 to build at the time. From my understanding the price on the servos has gone up a bit.

You will need:

2 - Aluminum Channels, one for the antenna rail and one to hold the servo where you bolt down to the tripod. I'm running a 15" bracket and a 4-1/2" bracket.

2 - RobotZone channel mount gearbox, I went with 360 degree CLOSED LOOP servos. The ratio I used was 3.8:1. 

2 - Servos. I went with HS-5485HB servos. If you're not good with a soldering iron, let ServoCity do the servos for you.

1 - 90 Degree Hub Bracket A

1 - Channel Bracket C

From Pololu you'll need:

Micro Servo Controller

The rest I'll share in pictures since they describe how I did it better than I can. I will STRESS the same thing that the wiki states. Keep your tracker clean and the wires out of the way. The gears have no mercy when it comes to chomping wires and fingers! 

Back side of the antenna rail. I'm running a 900mhz patch and the BOSCAM 5.8 receiver with TrueRC crosshair antenna. 

The video RX attaching to the Crosshair antenna. The bracket I took off of another antenna. 

3dRobotics 'Ground' module. Soon to be swapped out with a RDF900! Hyperlink is now known as L-Com. 

Here you can see the Pololu servo controller, the Channel C Bracket, the 4-1/2 channel and one of the monster servos. Again keep your wires clear! The servo will eat them! I drilled a hole through the tripod head (It's a cheap one) and bolted the channel down to the tripod head..

Up close of the Servos for Pan and Tilt. Here you can see the 90 degree hub mount bracket. 

I use a regular BEC to power the servos from a 12v battery. Usually I'll draw this power from my lead acid ground station battery. I have two USB cables. One from the Telemetry and the other from the servo controller that plug into a USB hub. Those then plug into my laptop and tie into Mission Planner. From there everything is controlled via Mission Planner and the telemetry coming down from the plane. 

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Comment by Joshua Ott on October 6, 2013 at 6:43pm

Thanks for posting, nice to meet you today.

Comment by Scott Fuller on October 6, 2013 at 6:45pm

Hey Josh no problem. Great meeting you as well! Hopefully we'll see you down at the field sometime. 

Comment by Nicholas Witham on October 6, 2013 at 7:55pm

looks great. well done on the DIY job.

Looks like there might be room for a slipring through the center of the yaw cog?

When you say expensive, how much are we talking there?

Comment by Scott Fuller on October 6, 2013 at 8:37pm

Hey Nick,

Here's the Invoice for the Servo City stuff: This was back in mid June. 

I just added everything up again and it looks like it's $226.92 before shipping. If I had to guess the servo gear boxes went up by $5 each. After you add in the servo controller you're about ~$245 before shipping. The tracker I built before this one was square bar from the hardware store and two regular servos. If I was to do it again I'd skimp on the aluminum and just buy the servo gear boxes. 

Comment by Antonius Lourenço Kasbergen on October 6, 2013 at 9:13pm

Hi, nice setup. How do you configure mission planner to control the antenna tracker? I know there is a menu called Antenna Tracker, but I only see two interfaces, maestro and ardu tracker. 

Comment by Scott Fuller on October 6, 2013 at 9:53pm

Usually the first thing I do is power up everything and get a solid GPS lock on the APM. After that I'll set my plane in front of the antenna tracker and zoom in REALLY tightly in Mission Planner under the Flight Planner window. I'll then right click and say Tracker Home -> Set here.

Then I'll drag the antenna tracker pin right on top of home and drop it. That should get me pretty close to where my antenna tracker is placed.

After that I'll flip over to the Initial Setup tab under Antenna Tracker and pull down the COM port for the Pololu servo controller and go with 9600 baud. When that's set I hit connect. At that point the tracker should go into motion.

You should be able to move the plane a few meters in front of the antenna tracker should move with it. If you need to reverse the direction it's pretty self explanatory. The sliders allow you to trim where the antenna needs to be facing. When you start up the system will think you're facing north. If you're facing East or West you have to aim accordingly. Nathaniel Caner documented some of this stuff starting back in December when he started venturing into antenna tracking. He was some inspiration into building my antenna tracker so my hats off to him and Michael Oborne. 

You can use Pololu Maestro Control Center to figure out your PWM settings and how far your servos an travel. Usually the PWM setting is (Large Number - Small Number) = PWM. In my case 2000 - 960 = 1040 for pan and 1904 - 1456 = 448 for my tilt. That'll give me a 45 degree angle for tilt and 360 for pan. You can get these numbers on the status tab in Maestro CC. Be careful NOT to go beyond the recommended travel! On the Servo City gear boxes you'll hear the POT start to click and the servo will just spin. At that point you get to play the servo centering game. 

One thing to note with the Pololu board is you may have to set it into USB Dual Port under Serial Settings. This allows you to connect to the COM port. 

If anyone wants to shed some light on the new "Obtain from Module" setting in Mission planner I'd love to know the story! I've tried plugging a GPS in to see if I could get it that way or from a live feeding APM. 

Comment by Christiaan van Vollenstee on October 7, 2013 at 12:46am

I recon most of these parts can be 3D printed to reduce the cost.

Comment by Michael Oborne on October 7, 2013 at 2:39am

"Obtain from Module" is if you have a garmin gps attached to the tracker. currently it only supports usb garmin devices, and was a contrib from Will Bryan

Comment by Martin on October 7, 2013 at 3:42am

Looks nice, but how's the wiring going to take that continuous winding and unwinding?

Comment by Rob_Lefebvre on October 7, 2013 at 7:55am

Not a bad setup.  How does the pitch servo deal with the fact that the antenna mass is not in-line with the pitch axis?  If it tilts up, the antenna mass will be trying to pull the pitch up even more as the antennas "fall back".  Also, wind load would do the same, try to push back on the pitch.


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