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I have this audio file (WAV) that I'm trying to decode using multimon-ng (also tried Qtmm AFSK1200 Decocoder). It should be using AFKS1200 but multimon-ng can't demodulate it and by the looks from the frequency analysis it doesn't quite match other images I found. Some EIA, EEA and CCIR messages can be seen but nothing else, except for the whole CSVDUMP.

enter image description here

The screenshot above shows peaks at ~1900 Hz (and at ~2222, 1200, 1570). I think it looks quite like AFSK1200 transmission.

WAV-file can be downloaded here (mono 44k1, PCM, 16-bit)

How would I go about to analyze what type is actually used on this?

I searched for images and audio. Listened and looked at examples of different mod-types, but I found nothing that really sounds or looks like the spectrum of this audio.

Would be grateful for any input on this.

Marcus Müller
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Chris8580
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    Your link requires credentials – Duston Oct 06 '21 at 12:59
  • This seems like a scavenger hunt / ARG so I don't really want to give out the answer... but I'll tell you that it's not packet, it's not data, it's not digital. – hobbs - KC2G Oct 06 '21 at 15:32
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    I've removed the fully and mostly unrelated tags. Please be rather careful when choosing tags - having well-tagged questions is a very powerful tool when looking for answers on a site :) – Marcus Müller Oct 06 '21 at 15:51
  • Link should does not require credentials. – Chris8580 Oct 06 '21 at 21:48
  • @hobbs It's too static to be morse code (still needs to be demodulated before to 100% sure). My next natural step is to analyze the actual sound by ear. I just slowed down (pitched) the audio to hear it more clearly. The sound actually reminds me of something that could be created using PLL (Phase locked loop). The artifacts of the pitch going up/down in certain ways reminds me of using a PLL module in an analog modular setup. The carrier signal is at 1900 Hz. I could demodulate EIA, EEA and CCIR messages though. I got a bunch of bracket separated hexadecimals for instance. Coincident? – Chris8580 Oct 07 '21 at 01:19
  • I finally got it! Makes perfect sense, since frequencies used in the transmission matches the standard I found. – Chris8580 Oct 07 '21 at 23:16
  • Hello and welcome to ham.stackexchange.com! – rclocher3 Oct 08 '21 at 19:49

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