Raspberry Pi Satellite Rotator Interface

MacDoppler and GHTracker

MacDoppler and GHTracker

We’ve been using our Portable Satellite Station 2.0 for some time now, and it works great. One area that can be improved is the interface between the MacDoppler Satellite Tracking program we use and the GHTracker application, which controls the Green Heron Engineering RT-21 Az/El Rotator Controller in our setup. Our initial approach was to run the GHTracker app under Windows/VMWare on the same MacBook Air laptop that runs MacDoppler. While this approach works ok, it was more complex and less reliable than we had hoped.

Fortunately, MacDoppler and GHTracker use a UDP-based interface that will run over an IP network.

GHTracker Running On A Raspberry Pi 3

A Raspberry Pi Satellite Rotator Interface – GHTracker Running On A Raspberry Pi 3

Anita, AB1QB, got great results using a Raspberry Pi 2 with a Touch Screen for her DX Alarm Clock Project, so I decided to do something similar with GHTracker. The new Raspberry Pi 3 Model B boards feature a built-in WiFi networking interface and four USB ports, making the RPi 3 a perfect platform for this project. An email exchange with Jeff at Green Heron Engineering confirmed that GHTracker could run under Linux on the Raspberry Pi (RPi).

We wanted a compact package that did not require anything but a power supply to run the final project. There are many great parts available for building a Raspberry Pi system. Here’s what we used:

The total cost for all of the parts was $120.

The assembly of the case and the hardware was straightforward. The folks at Adafruit provide a pre-built Jesse Linux image for the RPi, including the necessary driver for the Touch Screen Display.

After some configuration work and creating a few shell scripts to make it easy to boot the RPi to an HDMI display or to the Touch Display, we were ready to install the GH Tracker App. We also enabled the VNC Server on the RPi to use a VNC Client application on our MacBook Air instead of directly connecting a display, keyboard, and mouse to the RPi. Finally, we installed Samba on our RPi to allow files to be moved between our other computers and the RPi.

GHTracker Running on the Raspberry Pi

GHTracker Running on the Raspberry Pi

Jeff at Green Heron Engineering provided a copy of GHTracker V1.24 and the necessary serial interface library to enable its use on the RPi. Jeff is planning to make a tar file available with GH Tracker and the library in the near future. We did some configuration work on LXDE (the GUI interface for Linux that runs on the RPi), and it automatically runs GH Tracker whenever the RPi is booted up. We also optimized the GUI for the sole purpose of running GH Tracker on the Touch Screen Display. Finally, we configured the Ethernet and WiFi interfaces on the RPi to work with our home network and LTE Hotspot modem.

RPi GHTracker Test Setup

RPi GHTracker Test Setup

With all the software work done, it was time to test the combination with our Satellite Rotator System. The setup worked on the first try using a WiFi network connection between the MacBook Air Laptop running MacDoppler and the RPi. The USB-based serial ports, which control the Azimuth and Elevation direction of the rotators, worked as soon as they were plugged into the RPi. Also, the touchscreen interface works well with the GH Tracker App making the combination easy to use.

MacDoppler and GHTracker via VNC

MacDoppler and GHTracker via VNC

The VNC Client/Server combination allows us to work with the software on the RPi right from our MacBook Air laptop. It also makes for a nice display for monitoring the GHTracker App’s operation from the Mac.

You can find information about how to build your own Raspberry Pi Satellite Rotator Interface here.

Other articles in the Portable Satellite Station series include:

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Thanks to the help from Jeff at Green Heron Engineering, this project was very easy to do and worked out well. The Raspberry Pi 3 platform is powerful and relatively easy to work with. It makes a great start for many Ham Radio projects. Also, there is a wealth of online documentation, how-to information, and open-source software for the RPi. I hope that some of our readers will give the RPi a try!

Fred, AB1OC

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7 thoughts on “Raspberry Pi Satellite Rotator Interface

  1. Hi Fred, I’ve read all of your posts about your satellite station and I’m very impressed. Thank you for taking the time to share. I’m assembling a similar satellite station myself with an IC-9700 and a Yaesu G-5500 rotator and I’m considering switching to MacDoppler. I used HRD in the past and was never happy. Currently trying SatPC32 and PstRotator but not sold on either yet. MacDoppler seems to have all the features I need with a very attractive interface. I’m just curious right now why you need this Raspberry Pi as part of your setup at all. Does MacDoppler not allow direct control of your rotator? It seems like a lot of extra complication so I’m sure there is a benefit I’ve missed. I look forward to your response.
    73, Alex VA3ASE

    • Hi Alex,

      FB on your satellite station – it sounds really nice! MacDoppler does not know how to control the Green Heron RT-21 Az/El box directly because it has separate COM interfaces for the Az and El Rotators. The Raspberry Pi and the associated software allows MacDoppler to interface to the RT-21 As El. If you use a different rotator controller that can deal with the combined Yaesu Az/El format, then you would not need the Raspberry Pi.

      Fred, AB1OC

  2. Hi Fred,
    Enjoyed your nice step-by-step articles on building a portable satellite antenna system around the M2 LEO antennas and the 4 1/2’ roof tower.
    I am planning on building the same system but am planning on using WinSat32 for radio and rotator control. I live in an HOA restricted neighborhood and need a fairly low profile system (below the fence and easy to put up and take down) as well as portable to pack along in the RV. Your design looks great but I am wondering now that you’ve had it for a couple of years, would you do anything different? Or, are you still happy with the system?
    Thanks again for letting us benefit from your design work.


    • Hello Lew,

      Thank you for reading our Blog. We are pretty happy with our Satellite system here. I think you’ll be happy with the LEO pack – it is a good antenna system. If your budget allows, do consider the ARR preamps and the M2 polarity switches for your setup – they will both help you to receive weaker signals when satellites are near the horizon. Also, if you are choosing a radio which supports powering external preamps (ex. IC-9700, IC-9100, IC-910H…), don’t bother with sequencers and have ARR configure your preamps to be powered through your coax. This will allow your radio to handle the powering and sequencing of your preamps. The IC-9700 handles this very well and even includes a touch screen interface to turn the external preamps on and off – very nice.

      PCSat32 should be able to run the Green Heron RT-21 Az/El controller directly (I think) so you might not need the RaspberryPi adapter and software. Check the WinSat32 configuration screen to see if it can handle controlling separate Az and El rotator controllers via two different COM ports. If it does, you probably don’t the RaspberryPi.

      That’s all that I can think of right now. Good luck with your project!

      Fred, AB1OC

    • Hi Lew,

      I took a closer look at PCSat32 this morning and it is not clear that it will support the Green Heron RT-21 Az/El rotator controller directly. You might want to take a closer look at this issue before deciding on your control software/rotator controller choices for your station.

      Fred (AB1OC)

  3. I have been following your blog for over a year and have decided to design my satellite station after yours If you have any improvements please let me know

  4. Hello Don,

    The biggest improvements were to 1) move to using preamps powered through the coax feedlines from the radio and 2) carefully countweighting our satellite antennas so that the assemblies are properly balanced. The latter save a great deal of wear on the elevation rotator.

    Fred, AB1OC

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