I will play with that live cd if I can find it. It will probably work fine on my laptop, but not so much on the ARM platform where I want to use the POCSAG decoder utility.
My FD gets over 1200 calls a year, but I want to do big-data analytics (somewhat) on all calls going out to all the EMS and FD agencies in my county. There have been 9 calls in the last 15 minutes. It's a really heavily trafficed pager system, so there will be plenty of data for me to play with once I figure out my reception issues, On Tue, Jun 2, 2015 at 11:48 AM, Marcus Müller <marcus.muel...@ettus.com> wrote: > Hey Stephan, > > probably, you've even got a fully fledged GR installation around. If > not, I'd say: get the uber-cool LiveSDR DVD image [1], boot from it. > As soon as you have a full GR installation, you can run the GNU Radio > companion, which feels a lot like connecting together "real world > filters" with "cables". > > Actually, how many messages did you get in your firefighting days? Back > in my catastrophe protection service time, I didn't have a pager, but I > remember these things rarely going off -- luckily, not too many > catastrophes around southern Germany. That's why I didn't try getting > the signal myself -- I didn't assume I had a good chance of seeing it. > > Best regards, > Marcus > > [1] http://gnuradio.org/redmine/news/52 > > On 06/02/2015 04:24 PM, Stephan van Beerschoten wrote: >> I've been an IT geek for over 15 years, but the frequency chatter and >> filter settings are daunting to me. About 10 years ago almost got my >> HAM radio license to up my personal geek factor, but I couldn't get >> myself to learn the electronic circuitry needed. I bow before you :) >> >> To answer your question: I only use gqrx (http://gqrx.dk/) right now, >> and I just realized it's something built on top of GR and not GR >> itself. >> This tool doesn't really allow any custom filters. It's a use as-is >> kinda tool, but it has a lot of options. >> >> I mean, it could just be that my physical location is just not that >> good to receive these localized (county-wide only) pager broadcasts. >> When I still had my fire department pager I remember that I'd >> sometimes get a few alphanumeric characters garbled, indicating bad >> reception. I would like to try and improve the SNR to make the >> decoding work. >> >> >> >> On Tue, Jun 2, 2015 at 2:13 AM, Marcus Müller <marcus.muel...@ettus.com> >> wrote: >>> Hi Stephan, >>> >>> so how do you get the samples into GNU Radio? >>> I guess you use the gr-osmosdr source? >>> What does your flow graph look like? >>> >>> Best regards, >>> Marcus >>> >>> >>> On 06/02/2015 12:04 AM, Stephan van Beerschoten wrote: >>> >>> I am sure GR can do that, but I can't ;-) >>> Also, I don't have a good waterfall at all of the pocsag broadcast, which is >>> probably part of why I can't make it out with my ears either. Yes, I think I >>> have too much noise. >>> I hope it can be overcome with the right settings and filters. >>> >>> I'll try to capture a screenshot of what I see. It's nothing like the >>> screenshots in Wikipedia. >>> >>> On Jun 1, 2015 5:47 PM, "Marcus Müller" <marcus.muel...@ettus.com> wrote: >>>> Hi! >>>> I personally think the soundbite from wikipedia is broken, since it's >>>> 11kHz sampling rate violates Nyquist ;) >>>> Well, I must admit that my preferred way of analyzing this wouldn't be the >>>> audible reproduction; if you can see it clearly on the waterfall, and >>>> "optically" have enough dB between the carriers and noise, then you'll be >>>> fine decoding it. >>>> >>>> Now, I trust you're actually seeing excessive noise -- this might point to >>>> problems with your receiver (unsuitable antenna, too much noise in the >>>> amplifier, too little gain, intermodulation). The first step in limiting >>>> noise is always adding appropriate filtering. Can you add a FIR that >>>> selects >>>> your POCSAG channel out of your sampling bandwidth? >>>> >>>> Best regards, >>>> Marcus >>>> >>>> On 06/01/2015 11:28 PM, Stephan van Beerschoten wrote: >>>> >>>> You're right in that I need more than GR. The audio of a pocsag broadcast >>>> is very distinct. It's also clearly visible on a waterfall. >>>> The problem is that I have too much static in there. Way too much noise. I >>>> can't get the gqrx module (where I tune and see the waterfall) set right so >>>> the reception is fine. >>>> I think the Wikipedia article had a soundbite of a pocsag encoding. If you >>>> listen to it you'll notice it's very distinct.i just have 90% noise and I >>>> can hear the broadcast in the very background. >>>> >>>> On Jun 1, 2015 5:25 PM, "Marcus Müller" <marcus.muel...@ettus.com> wrote: >>>>> Hi again, >>>>> >>>>> Ok, I'm not familiar with the standard POCSAG, but if you got a signal >>>>> that you still need to decode with something else, how do you know you >>>>> don't >>>>> get clear reception? What is your measure for "good reception"? >>>>> >>>>> As far as I read the English wikipedia, POCSAC uses a 4.5kHz binary FSK, >>>>> so can you see the two alternating frequency e.g. in a waterfall plot of >>>>> your RX signal? >>>>> Ideally, you'd directly be able to see the 512, 1200 or 2400 baud. >>>>> >>>>> To explain a bit more: >>>>> GNU Radio is not a decoder for any specific standard; think of it as the >>>>> LEGO of SDR. You can build amazing things with it, in fact, there's a lot >>>>> of >>>>> examples that come with GNU Radio, and useful and complex standard >>>>> implementations (FM receiver, DTV transmission!), but if you need to have >>>>> something that's not there, you might need to a) use someone else's >>>>> Out-Of-Tree module or b) implement that functionality yourself. So I must >>>>> admit that I don't have the slightest idea which settings you're referring >>>>> to :) Maybe you're interested in a quick&dirty introduction to GNU Radio >>>>> [1]. >>>>> >>>>> In the case of POCSAG, I remember gr-pocsag being a thing (search for >>>>> pocsag on cgran.org); I can't remember the original author, and I presume >>>>> it's pretty much dead -- but I'd love to be proven wrong. >>>>> Also, pyboms has pocsag-mrt package, but that seems to rely on GNU Radio >>>>> 3.6.2, if the Readme is correct, so that's pretty dead, too. >>>>> >>>>> >>>>> Best regards, >>>>> Marcus >>>>> >>>>> [1] https://github.com/iZsh/pocsag-mrt >>>>> On 06/01/2015 10:18 PM, Stephan van Beerschoten wrote: >>>>> >>>>> It is. I plan on running the output through a utility that can decode it. >>>>> However, before that can happen I need to find out how I can get a clear >>>>> reception of the broadcast. >>>>> >>>>> On Jun 1, 2015 4:15 PM, "Marcus Müller" <marcus.muel...@ettus.com> wrote: >>>>>> I'm a bit confused, I though POCSAG was a text pager system? >>>>>> >>>>>> On 06/01/2015 10:04 PM, Stephan van Beerschoten wrote: >>>>>>> Hi Guys, >>>>>>> >>>>>>> I compiled gnuradio for my ODROID ARM platform, and I can listen to >>>>>>> regular wideband radio just fine. I am using a Generic RTL2832U with >>>>>>> Rafael Micro R820T tuner. >>>>>>> >>>>>>> The radio quality is fine, and even when using the rtl_fm tool >>>>>>> directly (off topic for this list), it works. >>>>>>> >>>>>>> However, when I switch channels to 155.520 to capture POCSAG >>>>>>> broadcasts I cannot get a clear reception. I can't find any decent >>>>>>> documentation on GR to tell me what each setting is, and I am not a >>>>>>> HAM radio operator so some of the basics evade me. >>>>>>> >>>>>>> I can't get decent POCSAG reception with the rtl_fm tool either, so >>>>>>> this is probably a setting thing somewhere. >>>>>>> >>>>>>> Why can't I get clear reception? Any pointers? >>>>>>> >>>>>>> Stephan >>>>>>> >>>>>>> _______________________________________________ >>>>>>> Discuss-gnuradio mailing list >>>>>>> Discuss-gnuradio@gnu.org >>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>>> >>>>>> _______________________________________________ >>>>>> Discuss-gnuradio mailing list >>>>>> Discuss-gnuradio@gnu.org >>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>> > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
