CERN Amateur Radio Club – CARC

Radiosondes

Riding the Wind: Chasing Radiosondes and Exploring Ham Radio with FT8 and DIY Gear

If you’ve ever dreamed of tuning into the hidden world of atmospheric science, few things are as thrilling as tracking radiosondes—those small, balloon-borne devices silently launched into the sky, transmitting weather data back to Earth. Combine that with the world of ham radio—especially with cutting-edge digital modes like FT8—and you’ve got yourself a hobby that’s part science lab, part scavenger hunt, and fully addicting.

Radiosonde hunting and ham radio share the same spirit: curiosity, experimentation, and the joy of building something with your own hands that connects you to the atmosphere, the ionosphere, or even someone halfway around the globe.

What Is a Radiosonde?

A radiosonde is a lightweight, instrument-packed weather sensor carried into the upper atmosphere by a high-altitude balloon. As it ascends—sometimes to over 100,000 feet—it transmits real-time data about temperature, humidity, pressure, and GPS coordinates. These are launched twice daily by meteorological agencies all over the world, and the best part? You can receive their signals at home, often with inexpensive gear.

These devices usually transmit on 400–406 MHz or 1680–1700 MHz, depending on the model and region. Many of them use FSK modulation and broadcast standard formats like RS41, DFM06, or M10. The transmissions are unencrypted, and with the right tools, you can decode live weather telemetry—or even track the exact location of the radiosonde as it floats down to Earth after balloon burst.

Homebrew Radiosonde Chasing: Your Setup

You don’t need a government-grade station to get started. Many radiosonde trackers build their setups on a shoestring budget. Here’s what a basic system might look like:

  • RTL-SDR dongle (~$30)
  • DIY 400 MHz Yagi or Helical antenna – build one from copper wire, PVC, and a few hand tools
  • SDR software like SDR# or GQRX
  • Decoder software like SondeMonitor, RS41 Tracker, or SondeHub auto_rx
  • Optional: a Raspberry Pi running SondeHub auto_rx, to automate tracking and uploading your data to the global network

Once set up, you can literally watch telemetry stream in—altitude, position, temperature—all from a weather balloon tens of kilometers above Earth. And if you’re adventurous, you can even go sonde hunting, using the GPS coordinates to recover the radiosonde after it lands. Many hobbyists collect them, repurpose them for APRS, or reprogram them for personal telemetry projects.

Helpful links:

Ham Radio Meets the Sky: FT8 and Digital Adventures

While you’re busy chasing weather balloons, don’t sleep on the power of ham radio, especially with digital modes like FT8—a weak-signal communication mode that has taken the amateur radio world by storm. FT8 lets you make contacts across the globe using minimal power and basic antennas, even when voice or CW signals would never make it through.

With FT8, you’re transmitting short, efficient bursts of data on HF bands like 20m or 40m. Many radiosondes only transmit data, but once repurposed, they can even be hacked into low-power transmitters or reused for APRS beacons, turning meteorological trash into ham radio treasure.

Want to combine both hobbies? Here’s how:

  • Reprogram recovered RS41 radiosondes to act as LoRa trackers or low-power ham transmitters
  • Use FT8 and WSJT-X to make global contacts using just a few watts and a simple dipole
  • Join digital contests or experiment with JS8Call, WSPR, and FT4

Why It All Clicks: Community, Curiosity, and the DIY Spirit

What makes radiosonde tracking and ham radio such a great pairing is the shared hands-on mindset. Both encourage experimentation, home-built gear, and learning by doing. Whether you’re soldering up a 5-element Yagi in your garage or decoding a signal from 30km above Earth, you’re tapping into the raw, analog-meets-digital magic of radio.

Better still, you’re never alone. There’s a thriving community of enthusiasts around the world sharing tips, decoding tools, and hunt reports.

Great places to connect:

Final Thoughts

Whether you’re tracking a drifting radiosonde across the countryside or bouncing FT8 signals off the ionosphere, these hobbies invite you to look at the sky a little differently—and to listen. With some basic gear, a little DIY grit, and the curiosity to explore, you can turn your shack into a window to the upper atmosphere and beyond.

So grab your SDR, fire up your software, and see what’s floating above your head—or join the CERN Radio Amateur Club (CARC) to get in touch with like-minded people. You might be surprised how much of the sky you can hear.