Number of targets can be detected

Hello, Nice job with the DoA. I have a question: Given that the system has 5 receive antennas, what is the maximum number of different targets the kraken SDR can detect at the same time?
For example the MUSIC algorithm can detect N-1 targets with N to be the numbers of antennas, however in this line I can see that the MUSIC is looking for 1 target.

Am I thinking something wrong?


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Wait, it would be possible to track more than 1 source on a frequency? I just assumed that would make KrakenRF go crazy and get confused if I tried tracking a frequency with multiple sources.

The recent update added the num sources option in the GUI. By default it is set to 1.

So if you know for sure that there are multiple unique sources on the same frequency you can try it out.

But if you increase num sources beyond what is actually there, the algorithm may not work as expected.

You are correct that in theory MUSIC can differentiate between N-1 sources, where N is the number of elements in the array.

Thank you. Another question. How kraken SDR operates if I set the number of sources to something greater than one and greater than N (i.e 6 ) in the two following cases

  • The sources (targets) are indeed >=6
  • The sources (targets) are <6

Also, In theory we can have multiple signals in the same frequency, if I set the number of sources to 1 will the system detect the DoA of strongest one?


If you set it greater than N-1, the behaviour will probably totally fall apart as then it will produce false peaks.

If there are multiple true non-correlated sources, and you set the source to 1, or lower than the number of sources, then depending on how much of each signal appeared in the collected frame of data for processing, it could lock to either signal, with a preference to the stronger one, but with some skew introduced by the other signals deponing on how much of a mix of signals there are in that frame, and their relative strengths.

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This is really cool, I remember vaguely that there was supposed to be a feature to track multiple signals on differing frequencies as long as they were within the bandwidth? Is that feature ready yet? I have a few fox sources that will be simultaneously transmitting only a few hundred khz apart.

Yep that feature has been out for a while. It’s the ability in the GUI to add multiple VFOs.

The Android app will collect all the data, and you can use the button just above the start navigation button to choose between the different frequencies you’ve collected data for.

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Is the feature to add multiple VFOs in the Android app only or is that supported natively by the KrakenSDR web GUI? I see the VFO selection in the settings.json file, but wasn’t sure how its working under the hood.

I am very interested in how the algorithm works when num_sources > 1. If I have two emitters on the same frequency, how does that differ from the collection of data with multiple VFOs, both from an application use standpoint and a ‘under the hood’ standpoint? Are both use cases supported by the KrakenSDR?

The core software implements multi-VFO, and then the Android App software supports collecting data from all the active VFOs. You need to set “Output VFO: All” in the web GUI settings. I actually just uploaded a video demonstrating this here KrakenSDR: Finding Multiple GSM Base Station Transmit Towers with the Multi-VFO Feature - YouTube

Num sources is only for when you expect there to be more than one source on a single frequency/channel. It will give you more peaks on the a single DOA display, with each peak ideally pointing to a source.

Multi-VFO is used when you have separate channels that are not overlapping. With multi-vfo you get separate DOA data for each VFO.

Carl, you’re a rock star. Thanks for the info

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