[MilCom] Unusual data signal heard.

[Tom ND5Y]

In case nobody else IDed that, it sounds to me like a ham digtal mode called THROB. Maybe there is a commercial/military system that is similar.



Throb is sort of like MFSK except it there are two carriers (tones) present at any time (similar to DTMF) and the tones fade out when they change frequencies.
See http://www.qsl.net/wm2u/throb.html


There is an audio sample about halfway down this page: http://wb8nut.com/digital which was probably made from the computer sound card output at the default rate of two "throbs" per second. This is what it would sound like on a SSB receiver.

You can also send it at twice or half the default speed. If somebody was sending it at the high rate using SSB and you recorded it in AM or FM it would probably sound like the file Kurt posted.

 
Tom ND5Y


----- Original Message -----
> From: Larry Van Horn <n5fpw at brmemc.net>
> To: KD7JYK DM09 <kd7jyk at earthlink.net>; milcom at mailman.qth.net
> Cc: 
> Sent: Tuesday, March 27, 2012 7:05 AM
> Subject: Re: [MilCom] Unusual data signal heard.
> 
> Kurt has forwarded his audio file to me and I have posted it to the web. You 
> can get details regarding this digital transmission at 
> http://mt-milcom.blogspot.com/2012/03/can-you-id-this-digital-transmission.html. 
> 
> You can hear the audio file at 
> http://audioboo.fm/boos/729749-kd7jyk-222-mhz-digital-audio-recording.
> 
> If you have any idea what Kurt and his friend heard, either email me or Kurt 
> direct, or you can reply here on this listserv.
> 
> Thanks and 73
> 
> Larry Van Horn, N5FPW
> Brasstown, NC USA
> MT Assistant/Review/Technical Editor
> Milcom Monitoring Post http://mt-milcom.blogspot.com/
> Twitter: @MilcomMP
>