The SDR Buffer at TU Graz
🕰️ Time Travel for Radio Waves
Have you ever missed a signal or wondered if your transmission was heard? The TU Graz SDR Buffer is a unique tool provided by the Institute of Communication Networks and Satellite Communications at the Graz University of Technology in Austria.
While most WebSDRs only stream live audio, the TU Graz system continuously records wideband spectrum data. This creates a “time machine” for radio enthusiasts.
Use Cases
- Post-Event Analysis: Go back in time to listen to a QSO or broadcast you missed live.
- Signal Verification: Check propagation conditions from hours or days ago to see if your own signals were audible in Austria.
- Spectrum History: Visually scroll through the waterfall display of past days to spot sporadic E openings or interference.
System Overview
The TU Graz SDR Buffer is a wideband spectrum recording project hosted by the Institute of Communication Networks and Satellite Communications at Graz University of Technology.
Technical Architecture
Unlike conventional WebSDR nodes that stream live, volatile I/Q data to clients, this system employs a persistent storage backend. It records the full spectral width of specific amateur radio bands (typically VLF segments and 160m to 10m).
This architecture decouples signal acquisition from demodulation:
- Acquisition: The SDR hardware digitizes the RF spectrum.
- Storage: The raw spectral data is written to a server-side circular buffer.
- Retrieval: The web interface renders a navigable time-frequency plot (waterfall). Users can select arbitrary time stamps to stream and demodulate the stored signal data.