[op25-dev] Re: Updating the OP25 codebase

ikj1234i ikj1234i at yahoo.com
Fri Mar 8 19:55:53 UTC 2013


Hi Keith

This would be very helpful!  We don't currently have a lot of hard data on how "phase 2" systems work.  AFAIK the top thing on the wish list would be a voice channel capture (when the channel is transmitting in phase 2 / TDMA mode).  Supposedly only the GRE PSR-800 scanner can receive this mode.

The capture should be in complex format - the sample rate should probably be at least 96,000, higher rates no problem.

As long your hardware is supported by GR you should be able to use the usrp_rx_cfile or uhd_rx_cfile app (or equiv). to do the signal capture...  Mostly, the only other thing when capturing is to make sure the RF front end gain is set optimally - there are GR apps such as uhd_fft and usrp_fft for scoping signals, helpful to get a bearing on things...

Best

Max

--- In op25-dev at yahoogroups.com, Keith S <ktsangel69 at ...> wrote:
>
> I'm not much of a coder but I can assist in taking captures of a p25 phase II system. There is a site near me.
> 
> I have a gnuradio setup using rtlsdr dongles. Let me know how and what you would like me to capture. There are audio channels and a Motorola trunking control channel on this site. I've done some basic decoding of the control channel with some windows apps already but haven't tried anything with gnuradio yet.
> 
> Keith 
> 
> ikj1234i <ikj1234i at ...> wrote:
> 
> >
> >
> >Hello Stevie
> >
> >Good to hear from you - this sounds like a good idea, for sure.
> >
> >It's always tempting to take such an opportunity as this to rewrite the entire system from scratch :)
> >
> >I think another piece to add to the puzzle that perhaps might be broken out as a separate item of concern would be UHD support.  
> >
> >Mostly I think that would affect our py code but not so much our C++ blocks.
> >
> >Also when you added the fsk4 demod block to the op25 core it took me longer than it should but as of a few days ago I checked in several remaining stragglers to svn, all of our py code is now upgraded to use the in-tree version.  I think there may have been one or two _very_ old ones that still use Franks' p25 and RD-LAP protocol handlers, but those apps date back to the days before our project had its own protocol processing...
> >
> >Also for GR 3.6 in addition to cmake there is a new directory structure that apps are to conform to.
> >
> >Looking further out there is some very exciting new stuff coming in GR for handling packet-oriented streams with timed transmission features.  This looks like it should be a good fit for our repeater work, but will require effort to make use of the new capability. 
> >
> >Finally, we're interested in P25 phase II, and are looking for RF captures of various phase II scenarios.
> >
> >Best
> >
> >Max
> >
> >--- In op25-dev at yahoogroups.com, Steve Glass <stevie.glass@> wrote:
> >>
> >> Hi Everyone
> >> 
> >> I think its time to organize a drive to move the code to the latest version
> >> of GNURadio. The OP25 codebase is suffering badly from bit rot and that
> >> needs fixing. GNURadio has evolved and developed many new features we've
> >> not properly kept up with. Fixing the codebase will mean that we can get
> >> people working with much less hassle than at present.
> >> 
> >> I've created a wiki
> >> page<http://op25.osmocom.org/wiki/wiki/ReengineeringPage>to act as the
> >> starting point. I shall start opening tickets this week and
> >> start mapping out the direction of the exercise. For now I want to focus
> >> the effort on the core OP25 components and we can use GRC as our top-level
> >> test harness. Take a look and take part in the discussion.
> >> 
> >> Atb
> >> 
> >> Steve
> >>
> >
> >
> >
> >
> >------------------------------------
> >
> >Yahoo! Groups Links
> >
> >
> >
>


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