Re: [Discuss-gnuradio] Regular FM radio fine, POCSAG horrible

[Marcus Müller]

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" <address@hidden> 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
>
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