The Year the Robots Listened to the Ionosphere
How 30 million FT8 signals revealed what really happens to HF propagation
When engineers let a ham-radio robot listen to the world for a year
Instead of relying on costly ionosondes or satellite instruments, two researchers from Hungary— Gergely Vakulya and Helga Albert-Huszár—built a simple remote SDR receiver that quietly listened to the 20 m band for twelve straight months. Using nothing more exotic than a wire dipole, an mcHF transceiver, and WSJT-X running in unattended mode, it logged an astonishing 30 million FT8 messages from around the world, including signals from Antarctica and ocean-going ships.
Why FT8 became the world’s biggest propagation experiment
FT8’s genius lies in its simplicity. Every 15 seconds, thousands of amateur transmitters send short digital bursts that include callsign, grid square, and signal-to-noise ratio. Each decode becomes a mini propagation report. Because millions of hams worldwide use the same timing and protocol, the data form a global ionospheric sensor network—no lab budget required.
Compared to WSPR, FT8 offers denser data and broader participation. Researchers can analyze changes in path lengths, skip zones, and gray-line effects by simply studying where and when those signals appeared.
How they did it
The team chose the 14 MHz (20 m) band—active day and night, yet manageable with a compact antenna. Their setup ran a full year on a headless Debian Linux mini-PC with VPN access, decoding every FT8 frame with WSJT-X and storing it in a text log. The result: over 30 million decoded messages covering more than 32 000 Maidenhead grids.
They even caught transmissions from maritime stations and remote DXpeditions, turning what was once hobby traffic into scientific data.
What the data showed
- Europe and the eastern US lit up the map—dense red zones of FT8 activity, with bright spots from islands like Cape Verde, Mauritius, and the Canaries.
- Seasonal ionospheric changes matched theory: short-range hops dominated in summer, while long multi-hop paths opened more often in winter.
- Nighttime “holes” in activity lined up perfectly with the D-layer’s disappearance and F-layer weakening.
- Skip zones—the no-man’s-land between ground and skywave ranges—showed up clearly in the statistics.
Why it matters
The study proved that you don’t need government funding to study the ionosphere. A modest SDR and some patience can yield scientifically valuable propagation data. As the authors note, the massive FT8 dataset “offers a powerful and accessible method for ionospheric and propagation research”.
It’s citizen science on a planetary scale—an entire radio community acting as a distributed sensor array, feeding researchers with millions of real-world observations every day.
Mini-FAQ
- Is FT8 really useful for science? — Absolutely. Each decode carries timing, location, and SNR data—perfect for analyzing how HF signals bend and fade through the ionosphere.
- How accurate are the locations? — FT8 uses the four-character Maidenhead grid (≈200 × 100 km), enough for propagation studies but not for pinpointing transmitters.
- Can anyone reproduce this? — Yes. All you need is an HF SDR, WSJT-X, and storage space. The full dataset is open on GitHub at Antiemes/Signals-FT8-data.
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