Friday, June 14, 2019

4800 symb/sec QPSK signal on 10160 kHz


Currently there is a signal active on 10160 kHz. It is QPSK modulated with 4800 symb/sec. The autocorrelation function for the QPSK symbols has peaks at multiples of 492=12×41 symbols:

symbol autocorrelation

Arranging the QPSK symbols in frames of 492 symbols, some interesting structures can be seen

492 symbols / frame

When the symbols are arranged in terms of 12-symbol long frames, some columns of the resulting matrix have a periodicity of 41 in the squared symbols.

TDoA geo-location indicates a location close to Luxembourg.

TDoA

5 comments:

ANgazu said...

Very ineteresting waveform.
Wiil keep an eye on it.

Best regards.
ANgazu.

Antonio Anselmi said...

I too! Note how the 12-symbol frames seem to use different polarity.
73
Antonio

KarapuZ said...

Perhaps, after demodulation, it makes sense to search the bitstream for a recurrent scrambler, for example, a forming polynomial 0,6,24,30. I will put a link with the signal recording (KIWI SDR in Poland), and two binary files, one of which is the result of demodulation, and the other (4800.bin) after the descrambler.
  Best wishes!
Danila
https://yadi.sk/d/9eb9tyQKJhkQ0A

Antonio Anselmi said...

Hello Daniel. That's strange, your demodulated stream differs from the one I got using the psk-4 demodulator of SA.
Ciao

hcab14 said...

Dear people

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Thanks