Software defined lighning detector?

VE3QCXVE3QCX
in WSPR, wsprdaemon, kiwirecorder

I was recently looking at how lighning detectors work. Mainly they compare S-meter spikes to a threshold level in a small band around 500KHz. This works but with problems due to local RFI which can confuse things. It occurred to me that I can tell very easily looking at a waterfall when lighning makes a brief hit to the noise floor which spans more than a decade of frequency. That means that software looking at signal levels on several frequency diverse filters and detecting via a time correlation between events across the filters placed in different parts of the lower HF spectrum would probably be a more reliable and robust way of detecting. If one of the filters happens to fall on a strong local RFI source then the time correlated detection subtractis it out so to speak. Software can also be smart and make use of known quantities such as variations in D-layer adsorbiton in day/night. Software knows time of day and GPS informed software knows sunset/sunrise so all of this data can probably get a much more informed idea of how close lightning stikes are. Could a KiwiSDR extension be a good platform for such a technique? Comments invitied.

Joe

Comments

  • G8JNJG8JNJ

    The main problem with the KiWi for this purpose is the very wideband nature of the receiver, and under conditions of nearby lightning, the coherent nature of the energy pulse often tends to drive the KiWi into ADC overload.

    This is less problematic with more distant storms, but even some of those can be quite strong at times.

    It would be interesting to see if the TDoA function could locate spasmodic lightning pulse though.

    Regards,

    Martin

  • VE3QCXVE3QCX
    edited December 2023

    Hi Martin

    I'm suggesting that the wideband response is a feature which can be leveraged in this case. A typical lightning detector is a narroband affair with a simple level threshold detection which is prone to many things that can cause a false positive so to speak. Local noise RFI or a strong local in band transmitter etc. On the other hand an SDR with software which looks for a time correlated jump of the floor across several filter windows running in different parts of the spectrum offers immunity from things which might affect a single narrow detector. Software can also look for an overload on the ADC as a feature of the detection perhaps to indicate a distance threshold. That would be subject to antenna efficiency obviously but could be an available option for configuring the detector.

    Best regards...Joe

    Edit: The other part I was suggesting is that due to D-layer adsorption an ADC overload during daytime is probably a much closer strike than one which happens at night due to better propagation during night time. I think an SDR offers a lot of possibilities to improve lighning detection.

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