Escaping the APRS Desert: Build Your Own Fill-In Digipeater and IGate

Have you ever found yourself in an "APRS desert"?. You’re out in the field, but no matter how hard you try, your 5-watt handheld signals just aren't reaching a nearby station. Today, we’re fixing that by building a high-power fill-in digipeater and IGate using a Raspberry Pi and the Toad's Digital Interface (DI).

This setup allows a low-power radio to talk to a high-power station, which then "digipeats" the signal to the next hop or gateways it directly to the 10-billion-watt internet.

The Hardware Hookup

To build this station, you’ll need the following gear:

Radio: A mobile VHF/UHF radio with a standard six-pin data port, such as the Icom ID-880H (ebay).
Audio Interface: The Toad’s Digital Interface (DI). It features a CM108 sound card and manual adjustment trim pots for audio levels (my site).
Computer: A Raspberry Pi (Models 02W, 3, 4, or 5)(amazon).
GPS Dongle(optional, but fun): A cheap USB GPS dongle to provide real-time location data, especially useful if you are mobile in an RV(amazon).

Physical Connections:

Connect the Toad’s DI to your radio's data port using a standard PS2-style extension cable.
Plug the DI into a USB port on your Raspberry Pi.
Set your radio to the standard APRS frequency (144.390 MHz in the US).
Ensure the radio's internal packet speed is set to 1200 baud.

Step 1: Initial Updates and Installation

We are using Raspberry Pi OS Lite (64-bit) for this build to save on resources. After SSHing into your Pi, run these commands to install Direwolf, the software heart of the station.

# Update repositories and upgrade system
sudo apt update && sudo apt upgrade -y

# Install Direwolf and the Joe text editor
sudo apt install direwolf joe -y

Step 2: Permissions and Logging

Direwolf needs access to the audio hardware to "hear" the packets and a directory to store logs

# Add the direwolf user to the audio group
sudo usermod -aG audio direwolf

# Create a logging directory
sudo mkdir /var/log/direwolf
sudo chown direwolf:direwolf /var/log/direwolf

Step 3: Configuring the PTT (UDEV Rules)

To enable Push-To-Talk (PTT) via the Toad’s DI, we must give the system permission to access the HID raw device.

# Create the UDEV rule
echo 'KERNEL=="hidraw*", MODE="0660", GROUP="audio"' | sudo tee /etc/udev/rules.d/99-toads-di.rules

# Reload the rules to apply changes
sudo udevadm control --reload-rules && sudo udevadm trigger

Step 4: Configuring Direwolf

The configuration file defines your callsign and how the IGate behaves. You can get your specific APRS passcode and configuration templates at TO's APRS Tools.

# Edit the configuration file
sudo joe /etc/direwolf.conf

Key settings to include:

MYCALL: Your callsign with SSID -1 for a digipeater.
PTT: Set to CM108 to match the Toad's DI hardware.
IGSERVER: Use noam.aprs2.net for North America.
DIGIPEAT: Enable 0 0 WIDE1-1 to act as a fill-in station.

Step 5: GPS Setup (Optional)

If you have a USB GPS dongle, install the GPS daemon so Direwolf can beacon your precise (or fuzzed) coordinates.

# Install GPS clients
sudo apt install gpsd gpsd-clients -y

# Verify your fix
cgps

Step 6: Start it up!

You can find the startup script over on TO's APRS Tools Page in the get-config section. Copy and paste that during the command stream below:

sudo joe /etc/systemd/system/direwolf.service
(paste start up script)
sudo systemctl daemon-reload
sudo systemctl enable direwolf
sudo systemctl start direwolf
sudo systemctl status direwolf

Final Results

Once you start the service, your station will begin beaconing. You’ll see your messages turn from "dull green" (sent) to "bright green" (acknowledged) on your APRS device, proving that your IGate is successfully bridging the gap to the internet.

For a full visual walkthrough and more APRS tips, watch the full video here: https://youtu.be/QI0eilGfLn8