Impressive and complex 48 KHz wideband OFDM 1024-tone modem with first up-chirped sweeps, likely a new(?) Russian stuff.
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| Fig. 1 - 38 KHz wideband OFDM |
part a)
duration: 425 ms
a same first pattern is 3 times repeated (looks like a sloped "digital" 8)
MFSK speed: 37.5 Bd
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| Fig. 2 - details of the part a) |
part b)
sweeps' section duration: ~1490 ms
since the different strengths of the signal there are 2 partially alternate sweeps, ~3 ms shifted
bandwidth: 48 KHz
sweeprate: 48 sps (...just the same value of the bandwidth), 21.2 ms duration
mode: up-chirped, FMCW (Frequency Modulation Continuous Wave)
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| Fig. 3 - details of part b) |
part c)
OFDM 1024-tone segments
segments have a duration of 160 ms (except the firts and the last that are shorter) and are separated by 2 sweeps
bandwidth: 48 KHz
speed: 37.5 Bd (aggregate 38400 Bd)
shift: 46.8 Khz
part d)
as part b), but shorter (~213 ms)
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| Fig. 4 - details of part c) |
Also found the 24 KHz wide waveform but unfortunately the SNR of the signal was besides mediocre to let any analysis effort but just its bandwidth (Figure 5).
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| Fig. 5 - 24 KHz wideband waveform |
My friend Joni tried a direction find utilizing the TDoA algorithm, results point to the Voronezh Oblast.
