Building Your Own APRS iGate with Raspberry Pi: A Complete Guide

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An APRS map
The APRS mapping website aprs.fi

I’ve been tinkering with Raspberry Pi projects for years, and one of my favorite applications has been setting up an APRS (Automatic Packet Reporting System) iGate. After numerous experiments and refinements, I’m excited to share this comprehensive guide to help fellow ham radio enthusiasts create their own receive-only APRS iGate using a Raspberry Pi and an RTL-SDR dongle.

When I first attempted this project, I found the available instructions scattered and sometimes confusing. That’s why I’ve compiled this straightforward guide that should take you less than 30 minutes to complete. Let’s dive in!

What is an APRS iGate?

An APRS iGate (internet Gateway) serves as a bridge between radio frequencies and the internet. It listens for APRS packets transmitted over the air and forwards them to the APRS Internet Service (APRS-IS) network. This allows for tracking of mobile stations and viewing their locations on websites like aprs.fi.

The beauty of a receive-only iGate is that it doesn’t require a transmitter license to operate – you’re simply listening to signals and passing them along to the internet. This makes it an excellent entry point for those interested in APRS without needing to transmit.

Required Hardware

To build your APRS iGate, you’ll need:

  • A Raspberry Pi (any model works, but I’ve had success with even the Pi Zero although a 3B+ with Ethernet is ideal)
  • An RTL-SDR dongle (I recommend one with TCXO for frequency stability)
  • A suitable antenna for 2m band (144-148 MHz)
  • A microSD card (4GB minimum)
  • Power supply for your Raspberry Pi
  • Network connection (Ethernet preferred for reliability)

I personally use an RTL-SDR R828D with TCXO, which has proven extremely reliable. The temperature-compensated oscillator prevents frequency drift, making it ideal for continuous operation. While cheaper dongles work, they may require frequent calibration.

Setting Up Your Raspberry Pi

Rather than walking through the entire Raspberry Pi setup process, I’ve created a pre-built image that you can download and flash directly to your microSD card. This image contains all the necessary software already configured – you’ll just need to customize a few settings.

Here’s how to get started:

  1. Download the pre-built image from my repository
  2. Extract the ZIP file (you’ll need about 4GB of free space)
  3. Use a tool like Raspberry Pi Imager, Etcher, or Win32DiskImager to write the image to your microSD card
  4. Insert the card into your Raspberry Pi, connect the RTL-SDR dongle, and power it up

I’ve found this approach saves hours of configuration time and eliminates many common setup errors.

Initial Configuration

Once your Raspberry Pi boots up, you’ll need to connect to it via SSH. If you’re not familiar with SSH, it’s simply a way to remotely access your Pi’s command line. On Windows, you can use PuTTY; on Mac or Linux, you can use the Terminal app.

The default login credentials are:

  • Username: pi
  • Password: raspberry

I strongly recommend changing this password immediately for security reasons. You can do this using the passwd command after logging in.

Next, run the Raspberry Pi configuration utility:

sudo raspi-config

Here, you should:

  1. Expand the filesystem (Option 1)
  2. Change the default password
  3. Set your timezone under Localisation Options
  4. Optionally, change the hostname to something memorable like “aprs-igate”

After completing these steps, reboot your Pi with sudo reboot.

Configuring Your APRS iGate

Now comes the most important part – configuring your iGate to connect to the APRS network. You’ll need to edit just two files:

First, edit the SDR configuration file:

sudo nano sdr.conf

You’ll need to change several key settings:

  1. Find the line starting with MYCALL and replace the placeholder with your callsign and SSID (e.g., MYCALL KD5TFD-10)
  2. Locate the IGSERVER line and set it to your regional APRS server:
    • North America: noam.aprs2.net
    • Europe: euro.aprs2.net
    • Asia/Pacific: aprs.asia
  3. Find the IGLOGIN line and enter your callsign (with SSID) and passcode
  4. At the bottom, update the PBEACON line with your latitude, longitude, and callsign

You’ll need an APRS passcode, which you can generate using the APRS Passcode Generator at sites like aprs.fi.

If your local APRS frequency isn’t 144.800 MHz (the default in the image), you’ll also need to edit the startup script:

sudo nano dw-start.sh

Find the line containing rtl_fm -f 144.80M and change the frequency to match your local APRS frequency. In North America, for example, it’s typically 144.39 MHz.

Testing Your iGate

Before setting up automatic startup, let’s test that everything works correctly:

rtl_fm -f 144.80M - | direwolf -c sdr.conf -r 24000 -D 1 -

(Replace 144.80M with your local APRS frequency if different)

If everything is configured correctly, you should see Direwolf start up, connect to the APRS server, and begin decoding packets. You might see something like:

Dire Wolf version 1.3
Reading config file sdr.conf
Audio input device for receive: stdin (channel 0)
...
Now connected to IGate server euro.aprs2.net

Let it run for a few minutes to ensure it’s receiving and decoding packets properly. Press Ctrl+C to stop the test when you’re satisfied.

Setting Up Automatic Startup

The final step is to configure your iGate to start automatically whenever your Raspberry Pi boots up. This is done using cron, a time-based job scheduler:

crontab -e

At the bottom of the file, you’ll see a commented line that looks like:

#* * * * * /home/pi/dw-start.sh >/dev/null 2>&1

Remove the # at the beginning of the line to uncomment it, then save and exit the editor.

Now reboot your Pi:

sudo reboot

After rebooting, your iGate should automatically start within about 90 seconds. You can verify it’s working by checking aprs.fi for your callsign.

Troubleshooting Common Issues

In my experience setting up multiple iGates, I’ve encountered a few common issues:

  1. Connection failures: Check your network connection and ensure your Pi can reach the internet.
  2. No packets received: Verify your antenna connection and placement. The RTL-SDR is not very sensitive, so a good antenna is crucial.
  3. Frequency drift: If you’re using a non-TCXO dongle, you might need to calibrate it. You can do this by adding a PPM correction value to the rtl_fm command.
  4. Illegal instruction error: On some older Raspberry Pi models, you might encounter this error. If so, you’ll need to recompile Direwolf from source:
cd ~
sudo rm -r direwolf
git clone https://www.github.com/wb2osz/direwolf
cd ~/direwolf
make
sudo make install
make install-rpi
make install-conf

Enhancing Your iGate

Once your basic iGate is running, there are several ways to enhance it:

  1. Better antennas: A proper 2m antenna will dramatically improve reception. I’ve had great results with simple J-poles mounted as high as possible.
  2. Frequency calibration: For non-TCXO dongles, running a calibration can improve reception.
  3. Visualization: You can install additional software like Xastir to visualize APRS traffic locally.
  4. Weather station integration: If you have a weather station, you can configure your setup to report weather data.

Conclusion

Building an APRS iGate with a Raspberry Pi is a rewarding project that contributes to the ham radio community. By forwarding packets to the APRS-IS network, you’re helping extend the reach of the APRS system for all users.

I’ve been running my iGate continuously for over two years now, and it’s been incredibly reliable. The total cost was under $50, making it an affordable way to get involved with APRS.

I hope this guide helps you get your own iGate up and running quickly. If you have any questions or suggestions for improvements, please feel free to reach out. Happy building!

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