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TDoA how to interpret the maps

I find the TDoA feature very impressive and have a lot of fun using this great feature so thanks for all the hard work!

Sometimes it throws me a map that leaves me scratching my head. This was on 5 MHz in the daytime, skip is quite short so I was expecting an easy fix. What is this map trying to tell me?



  • NVIS paths have proven tricky for me.
  • Hi Dave - TDoA is a great addition isn't it? I've probably missed the real point of your question but from frequency/waveform and approx location I would guess that is Dutch Navy STANAG 4285 at position marked PBC on the TDoA map...?
  • Yes it amazing, having great fun. Im sure your right, its just the map was showing a lot of conflicting information, and I wondered what sort of propagation (NVIS I assume) would result in very little correlation between receiving stations.

  • It is instructive to look at the "dt" result plots to try and understand the quality of the correlations. Also in "old map" mode the individual station-pair maps show in the top legend the RMS dt value of the timings. A good value is < 15 us and that will be reflected by a dt plot that is all red with a dark red vertical line in the center indicating a correlation coefficient close to one (also the 'x's will be lined up nicely). Your maps will have the contours and red/green heat map overlays packed closely together and not spread out over large areas.

    Often you will see RMS dt values > 100 us and dt plots with blue through green colors and the 'x's all over the place. And I think this means multi-path is having an effect.
  • Ahh.. I guess that was what Dave really wanted to know! Thank you - very useful info and big help in understanding how to use/interpret TDoA results.
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