TDoA SuperDARN/Finland

Today signals from the SuperDARN radar in Finland were active around 12375 kHz and the most likely position matches quite well with the known CUTLASS radar position near Hankasalmi.

TDoA maps

TDoA cross correlations

There are pulse trains spaced by integer multiples of 2400 μsec (0,9,12,20,22,26,27), as descibed here:

SuperDARN pulse train

30 of these pulse trains are repeated, approximately each 95.3 msec, then there is a gap of two frames and some delay, and then the next 30 pulse trains follow:

SuperDARN pulse frames

The transmissions seem to repeat each minute with a small gap at the end of the minute.

Another way to verify the used pulse sequence is to compute the autocorrelation of each line of the plot above. All differences between all combinations of the individual pulses show up as peaks in the autocorrelation:

frame number vs. autocorrelation lag