OFDM 16-tone 75 Bd, 110 Hz (MS 188-110A App.A modified?)

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I-56578
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OFDM 16-tone 75 Bd, 110 Hz (MS 188-110A App.A modified?)

Mensaje por I-56578 » 29 Jun 2015 23:48

hola,
I had this signal via Twente SDR on USB 14301.8 (cf) on 28/06/15 (1710z) just in the 20 mt band, reserved to HAM traffic.
The waveform is an OFDM 16-tone PSK, 75 Bd and 110 Hz shift, sent in burst mode. It is very similar to the obsoleted Standard NATO MIL 188-110A Appendix A without the doppler tone @ 605 Hz and in not-continuous mode.
There is a Chinese variant of the MIL 188-110A 16 channels: it could be this case, but I could not find info or logs about it. The burst mode could lead to something like a selcall waveform.
Signal can be downloaded from here

Saludos cordiales!

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ANgazu
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Re: OFDM 16-tone 75 Bd, 110 Hz (MS 188-110A App.A modified?)

Mensaje por ANgazu » 30 Jun 2015 11:44

Hola.

The very precise timing points to some kind of TDMA system. Structure is somehow similar to LINK11.
Will need more recordings and investigation to fix the mode.


La precision en el tiempo apunta a algun tipo de sistema TDMA. La estructura de la señal es parecida al LINK11.
Haran falta mas grabaciones e investigacion para determinar el sistema.

Saludos cordiales.
ANgazu.
EA4021SWL aka ANgazu

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

Re: OFDM 16-tone 75 Bd, 110 Hz (MS 188-110A App.A modified?)

Mensaje por I-56578 » 30 Jun 2015 14:10

thanks AngazU for your comments, always interesting. Infact, the curious aspect is just the pips that are sent about every 730mS. The other curious aspect is that these transmissions occur in the well-known 20 mt reserved band (14000-14350): that's because I guessed a military or intel source, possibly from the far east.
This signal usually pops up late in the afternoon (18/1900z), at least here, around 14300.0 KHz on USB. Signals are better received in north Europe since the reception by Twente-SDR (Holland) grants a more strong signal than the one received here in center Italy, or may be the case of a long-path via North Pole from east... but i's just a my guess, who knows?

Saludos a todos los amigos del foro, disculpas por no escribir en español :(

Antonio

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