Sending Weather Data to APRS-IS Using Bash and OpenWeatherMap API

As radio amateurs, integrating real-world sensor data into APRS can be both useful and fun. In this guide, I’ll show you how to use a Bash script to automatically fetch your local weather data from OpenWeatherMap and send it to the APRS-IS network.

This method is especially useful for stations that don’t have a dedicated weather station but want to share weather conditions based on their location.

🧰 What You’ll Need

• A Linux machine or server (I’m using Debian)
• Your APRS callsign and passcode
• An OpenWeatherMap API key (free)
• Coordinates of your QTH
• jq and netcat installed

🔐 Step 1: Get Your API Keys

APRS-IS Passcode

If you don’t already have a passcode, you can generate it based on your callsign. For example, you can use my free generator here:

👉 https://pass.hamradio.my

OpenWeatherMap API Key

1. Go to https://openweathermap.org/api
2. Sign up for a free account.
3. Copy your API key from the dashboard.

🗺️ Step 2: Determine Your Coordinates

You’ll need your latitude and longitude in decimal format.

Example for Kuala Lumpur:

• Latitude: 3.1390
• Longitude: 101.6869

📜 Step 3: The Bash Script

Here’s the full script:

#!/bin/bash

# === USER CONFIGURATION ===
CALLSIGN="PJUWX-13"                   # Your APRS callsign (with SSID)
PASSCODE="12031"                      # Your APRS-IS passcode
LAT="3.1390"                          # Latitude (decimal format)
LON="101.6869"                        # Longitude (decimal format)
OPENWEATHER_API_KEY="your_api_key"   # Replace with your OpenWeatherMap API key
SERVER="rotate.aprs2.net"            # APRS-IS server
PORT="14580"                          # APRS-IS port
COMMENT="9M2PJU WX Station 🐧"       # Comment sent with weather data

# === FETCH WEATHER DATA ===
weather_json=$(curl -s "https://api.openweathermap.org/data/2.5/weather?lat=$LAT&lon=$LON&units=metric&appid=$OPENWEATHER_API_KEY")
temp=$(echo "$weather_json" | jq '.main.temp' | xargs printf "%.0f")
humidity=$(echo "$weather_json" | jq '.main.humidity')
pressure=$(echo "$weather_json" | jq '.main.pressure')

# === FORMAT WEATHER PACKET ===
lat_aprs=$(printf "%02d%05.2fN" "${LAT%.*}" "$(echo "${LAT#*.} * 60 / 1" | bc -l)")
lon_aprs=$(printf "%03d%05.2fE" "${LON%.*}" "$(echo "${LON#*.} * 60 / 1" | bc -l)")

WX_PACKET="${CALLSIGN}>APRS,TCPIP*:@$(date -u +%d%H%Mz)!${lat_aprs}/${lon_aprs}_.../...g...t$(printf "%03d" $temp)r...p...P...h${humidity}b$(printf "%05d" $((pressure * 10))) ${COMMENT}"

# === SEND TO APRS-IS ===
(
echo "user $CALLSIGN pass $PASSCODE vers PJUWX-Bash 1.0"
echo "$WX_PACKET"
sleep 1
) | nc "$SERVER" "$PORT"

echo "✅ Sent: $WX_PACKET"

Save this as send_weather_aprs.sh, and make it executable:

chmod +x send_weather_aprs.sh

🧪 What This Script Does

1. Fetches Weather Data from OpenWeatherMap using your coordinates and API key.
2. Extracts:
   • Temperature (°C)
   • Humidity (%)
   • Pressure (hPa)
3. Formats your position in APRS format (degrees and minutes).
4. Builds an APRS packet with a weather report.
5. Sends the packet using Netcat (nc) to the APRS-IS network.

🕒 Automate It with Cron (Optional)

To send updates every 20 minutes, add it to your crontab:

crontab -e

Then add:

*/20 * * * * /path/to/send_weather_aprs.sh

📡 Example APRS Packet

PJUWX-13>APRS,TCPIP*:@220945z0313.14N/10141.21E_.../...g...t031r...p...P...h78b10032 9M2PJU WX Station 🐧

💡 Things to Improve

This is a simple example to get you started. You could extend this by:

• Adding wind speed and direction
• Including rainfall (requires API with more data or sensors)
• Sending packets via RF using a TNC instead of APRS-IS
• Switching to Python for better formatting and error handling

🎯 Conclusion

This script is a lightweight, no-hardware solution to send real-time weather data to APRS using just Bash and a public API. Whether you’re setting up a portable station or just want to contribute environmental data from your QTH, this is a great way to get started.

Feel free to modify, share, or expand upon it!