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 > <mailto: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 >> <mailto: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 <http://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 <mailto: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 <mailto:Discuss-gnuradio@gnu.org> >>> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >> >
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