Re: [Discuss-gnuradio] INMARSAT wide signal question

[Henry Barton]

So the control channels are the narrow ones? I’m guessing the really wide ones are the traffic. (On a side note, I’m kind of surprised that people [you and killmore231] can get Inmarsat with a patch. I just barely see the signals with 9A4QAV’s helix and an SDRplay. However, Iridium comes in like a blowtorch.) Anyway, can’t wait to see your program. Is it on Github?

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From: Kevin McQuiggin
Sent: ‎Tuesday‎, ‎May‎ ‎3‎, ‎2016 ‎10‎:‎02‎ ‎PM
To: Henry Barton
Cc: address@hidden

Hi Henry:

I have an Inmarsat demodulator working for the lower speed control channels.  I am writing a program to decode the traffic, but this is not a trivial task.  Think on the order of 1000 lines of C.  It is "almost" working, I am hoping for valid output in the next week or so, depending on my free time.

My program is currently a standalone program, but once it's done it could conceivably be converted to one or more gnuradio blocks.  

I suggest the following document to give you background on the channel specifications for Inmarsat:

http://www.icao.int/safety/acp/inactive%20working%20groups%20library/acp-wg-m-iridium-8/ird-swg08-wp07%20-%20old_amss_material_ch.4_plus_attachment.doc

The demodulation is fairly easy, read the spec document and the channel characteristics are pretty well described.  My gnuradio demodulator is based on the GMSK demod block.  I'm using a home brew patch antenna, and the LNA4ALL low noise amplifier.

Kevin

Sent from my iPad

On May 3, 2016, at 12:45 PM, Henry Barton <address@hidden> wrote:

http://rtlsdrblog.rtlsdrblog.netdna-cdn.com/wp-content/uploads/2015/10/sdrplay_lband-1024x573.png

I didn’t see the widest signal (bright yellow) from this picture on sigidwiki.com. Does anyone know what it is? If so, can it be decoded by GNUradio? Thanks.

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