Re: [Discuss-gnuradio] mode S ADS-B reception

[Hugh Blemings]

Hi Eric, Matteo, All,

Eric & Matteo wrote previously: 

> > Hi - I have not done anything along that path yet - in June, at the 
> > hamvention in Fredrichshafen I got the chance to see the SBS-1 device 
> > live... it does what we would like to do with the usrp - 
> > http://www.kinetic-avionics.co.uk/ and it was showing alot of traces by 
> > only means of the vertical shown in the picture.

Yes, it's a nice piece of kit.

> > I am still interested in the subject but I haven't found any decent 
> > documentation about the protocol by googling a bit around...
> 
> I believe the specs are available from RTCA, Inc.
> 
> See http://adsb.tc.faa.gov/ADS-B.htm towards the bottom of the page.

Yes, this seems right, the only specs I could find were purchasable through 
RTCA for around USD$300 which is getting a little steep for a hobby project :)

This chap (a fellow ham as it turns out) has a little info and some links;

http://www.tech-software.net/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=2&MMN_position=2:2

Including a reference for the bitstream timing, but not the contents of the 
frame.  I infer it uses pulse position encoding for the response based on this 
link;

http://web.mit.edu/6.933/www/Fall2000/mode-s/modulation.html

I figure I'll do some more digging around in the first instance for resources 
on the web.

Failing that maybe see if I can at least capture some datastreams off air and 
see where that leads...

Cheers,
Hugh
VK1YYZ/AD5RV