Community science · NSW, Australia

Listening for lightning.

SfericNet is a project to build a network of small radio receivers that detect lightning and work together to estimate where it happened.

The aim is to make the receiver design, signal processing and data handling understandable and open to contribution. The initial focus is New South Wales and surrounding areas, with practical testing guiding each stage of development.

How the network works

Lightning produces short radio impulses known as atmospherics, or “sferics.” Our planned receivers listen in the very low frequency range using two ferrite antennas arranged at right angles. Each antenna has its own signal channel.

1. Listen locally. A station continuously samples its two channels. Software looks for brief signals above the local noise and saves a short segment around a possible event.
2. Give the signal a precise time. A satellite navigation receiver provides a timing reference. Relating that reference to the sampled signal accurately is one of the key bench tests still to complete.
3. Compare stations. The server looks for matching waveforms from at least four distinct, qualified stations. Differences in arrival time help estimate the source location.
4. Publish an experimental result. Signals that pass the checks can produce a location estimate. The map groups results into hexagonal areas rather than displaying exact receiver coordinates.

A nearby electrical appliance can also produce radio noise. Matching several stations, checking timing quality and rejecting ambiguous signals are essential. Good results will depend on receiver placement, network geometry and calibration—not simply the number of detections.

What happens to the data?

The intended station upload is a triggered, roughly 20-millisecond sample from both channels. Continuous recordings stay at the receiver; the design does not stream them to the server.

On the server, waveform snippets live in a temporary memory buffer. Unmatched snippets expire within 30 seconds, and matched snippets are released after a result is saved. The database keeps event metadata for 30 days and retains compact location results; it does not store the waveform recordings.

Precise station coordinates are used privately for the calculation. The public API exposes station areas and grouped results, without exact station coordinates or node identifiers. This describes detection data; it is not a website advertising or cookie policy.

Where the project is now

The backend can receive authenticated events, compare signals, calculate regional location estimates and serve the map. The portable station software includes detection, timing checks and packet encoding. Connecting that software to the actual receiver hardware is the next stage.

Before wider deployment, we need to verify the audio converter and satellite timing on the bench, measure the antennas and analogue channels, and compare network results against real observations. There is no validated receiver kit or ready-to-flash station release yet.

An empty map does not mean there is no lightning. The preview may have no reporting receivers, and its station count currently reflects recent qualified events rather than a complete inventory of powered-on stations.