MFSK-47

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I-56578
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Registrado: 06 May 2015 19:28

MFSK-47

Mensaje por I-56578 » 28 May 2015 17:07

this waveform was seen on 14635.0 USB (dial freq) and it seems to me an MFSK 47 tones, 47 spaced, and 47 Baud speed... that's a bit odd.
Maybe I made some wrongs, someone can verify?
A short recording may be downloaded from here:
https://www.dropbox.com/s/87e0e8rxybiok ... z.wav?dl=0

Gracias!
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Antonio

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ANgazu
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Re: MFSK-47

Mensaje por ANgazu » 28 May 2015 19:04

Hello.

The speed is 47 b, but something very unusual is taking place.

As you can see in picture, the segment of the signal is synced, but some times there are 3 or 2 tones instead of 1 as is espected in MFSK.

This could point to a transmitter problem or to a very odd signal.
I guess more recordings will help to analyse it.
MFSK_doubt.jpg

Saludos cordiales.
ANgazu.
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EA4021SWL aka ANgazu

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Rapidbit
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Re: MFSK-47

Mensaje por Rapidbit » 29 May 2015 18:06

I get 50 tones. Really, there are some strange areas.
Best regards.
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EA4GPX, EA4022SWL, AMSAT-EA 423.

I-56578
Mensajes: 27
Registrado: 06 May 2015 19:28

Re: MFSK-47

Mensaje por I-56578 » 30 May 2015 13:59

fixed: it was a bad recording due to a narrow filter cutting off part of the signal :(
here a correct recording:
https://www.dropbox.com/s/relrmp58ct8v0 ... 4.wav?dl=0

Signal bandwidth is approximately 3250 Hz. The signals has 68 tones (34 + 34), 47 hertz spaced, plus a visible empty place in the center of the spectrum.
Unlike normal MFSK (1 symbol = 1 tone) the signal sends up to 5 tones per symbol and its synched (1000mS cycle). Manipulation speed (47 Bd) and tone shift (47 Hz) suggest that the signal could be formed using OFDM technology.
Every 1-second cycle the signal transports 45 symbols + 1 sync (2 symbol lenght), so the 47 symbols rate on-the-air.
I do not know who they are, possibly CIS/Russian ?

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