Re: [Discuss-gnuradio] Live fm detection gr-inspector

[Sebastian Müller]

Daniel,

please take some time to get familiar with the documentation. Instead
of copy&pasting settings from other users, this is much more
beneficial for you since you understand what impact all parameters
have and makes your debugging life much easier.

The signal detector block for instance takes an argument „min_bw“,
ignoring all bandwidths that are smaller than that value:
https://gnuradio.github.io/gr-inspector/classgr_1_1inspector_1_1signal__detector__cvf.html

In your attached picture I would set the threshold to something like
-65. -78 looks too deep into the noise floor.

Best,

Sebastian Müller
address@hidden
PGP ID DC2AA3EE

Am 15. Juni 2019 um 07:55:43, Müller, Marcus (CEL) (address@hidden) schrieb:
> So, let's really look at what you receive there. What's your antenna?
>
> When you connect a QT GUI time sink, what's (roundabout) your maximum
> amplitude coming out of the USRP Source?
>
> Best regards,
> Marcus
> On Fri, 2019-06-14 at 23:25 -0500, Daniel Andres Palacios wrote:
> > Hello Kyeong,
> > About gain level, it was a desperate measure, in my eagerness to get
> > signals. If someone has used managed to detect FM signals and can
> > give me the parameters used,
> > I would appreciate it.
> >
> > Thanks
> >
> >
> >
> >
> > On Thu, Jun 13, 2019 at 10:45 PM Kyeong Su Shin > > > wrote:
> > > Hello Daniel,
> > >
> > > A few things to note:
> > >
> > > -Gain level of USRP B200 does not go up to 120 dB. Sure, GNU Radio
> > > or UHD won't complain about this, but it maxes out at around 70 dB
> > > (I do not remember the exact number).
> > >
> > > -My eyes are untrained (I did study sigint before, but it's been a
> > > few years since then), so I cannot tell which peaks are spurious
> > > and which peaks are true WBFM signals by simply looking a
> > > periodogram. However, it seems like the signal detector block is
> > > not detecting some serious (~-40 to -20 dBFS) peaks in the
> > > spectrum. If those peaks are FM signals, then the detector block is
> > > either misconfigured or is not suitable for the task. If those
> > > peaks are not FM signals (are spurious signals or unwanted
> > > interferences) and if you are not seeing actual FM signals on your
> > > periodogram, then you will need to move your receiver to elsewhere
> > > or get a better antenna (and may have to decrease the gain of the
> > > receiver).
> > >
> > > -gr-inspector's signal detector uses energy detection to detect
> > > signals, which works on most types of signals but is also
> > > suboptimal (in terms of the detection accuracy). You may want to
> > > come up with your own detector block that exploits the
> > > characteristics of the FM signal if you want to maximize the
> > > detection accuracy (in terms of P_d and P_fa).
> > >
> > > Regards,
> > > Kyeong Su Shin
> > >
> > > 보낸 사람: Daniel Andres Palacios 대신 Discuss-
> > > gnuradio
> > > 보낸 날짜: 2019년 6월 14일 금요일 오전 6:14:07
> > > 받는 사람: Sebastian Müller
> > > 참조: address@hidden
> > > 제목: Re: [Discuss-gnuradio] Live fm detection gr-inspector
> > >
> > > OK, my bad.
> > >
> > > Here is my actual configuration. But again, signals appear and
> > > disappear.
> > > Even when I try to cath a fm station, if the GUI Inspector is not
> > > set to manual, a get the same behavior
> > >
> > > Thank you.
> > >
> > >
> > >
> > > On Thu, Jun 13, 2019 at 2:11 PM Sebastian Müller
> > > wrote:
> > > > I just noticed something else:
> > > > The USRP sample rate is set to 500kHz, not 20MHz. So you are only
> > > > looking at 2.5 % of the target spectrum! It is also possible,
> > > > that
> > > > there are just no signals in that particular section.
> > > >
> > > > Best,
> > > >
> > > > Sebastian Müller
> > > > address@hidden
> > > > PGP ID DC2AA3EE
> > > >
> > > > Am 13. Juni 2019 um 20:20:24, Sebastian Müller (address@hidden)
> > > > schrieb:
> > > > > Hi Daniel,
> > > > >
> > > > > from what you tell us, I conclude this is not an issue with gr-
> > > > inspector but rather with
> > > > > generally receiving signals.
> > > > > If you use the QT GUI Sink for instance instead, you will see
> > > > the same (empty) spectrum.
> > > > > I would recommend to try and get better reception, until you
> > > > can distinguish signals
> > > > > visually in the spectrum manually. Are you using the correct
> > > > antenna for this frequency
> > > > > range? Is this antenna positioned in a beneficial location for
> > > > reception? Have you played
> > > > > around with the Rx gain of the USRP?
> > > > >
> > > > > Best,
> > > > >
> > > > > Sebastian Müller
> > > > > address@hidden
> > > > > PGP ID DC2AA3EE
> > > > >
> > > > > Am 13. Juni 2019 um 19:10:59, Daniel Andres Palacios (
> > > > address@hidden) schrieb:
> > > > > > Thanks for your reply
> > > > > >
> > > > > > I trying to detect and classify all fm transmitted stations
> > > > in my country,
> > > > > > with the gr-inspector OOT.
> > > > > > In my country (Colombia) it goes from 87,9 to 107.9 MHZ.
> > > > > > I only have an USRP B200 and think that if I set the center
> > > > frequency at 98
> > > > > > MHZ and put a bandwidth of 20MHZ its posible to get my goal.
> > > > But actually
> > > > > > im not getting signals detected
> > > > > > [image: Captura de pantalla de 2019-06-13 11-17-05.png]
> > > > > >
> > > > > > On Tue, Jun 11, 2019 at 12:53 PM Müller, Marcus (CEL)
> > > > > > wrote:
> > > > > >
> > > > > > > Hi Daniel,
> > > > > > >
> > > > > > > please remember to be specific when asking a question:
> > > > "best way" is a
> > > > > > > bit ambiguous, and "I'm not getting a good result"
> > > > definitely is
> > > > > > > insufficient for us to help you make things work better.
> > > > What doesn't
> > > > > > > work sufficiently well? What happens instead?
> > > > > > >
> > > > > > > Best regards,
> > > > > > > Marcus
> > > > > > >
> > > > > > > On Tue, 2019-06-11 at 12:36 -0500, Daniel Andres Palacios
> > > > wrote:
> > > > > > > > Hi to everyone.
> > > > > > > >
> > > > > > > > What is the best way to receive all fm modifications. I'm
> > > > usigin an B200
> > > > > > > USRP.
> > > > > > > > I think that putting the center frequency at 98M and a
> > > > bandwidth of 20M
> > > > > > > is a good way,but I'm not getting a good result.
> > > > > > > >
> > > > > > > > The idea is to detect all fm center frequencies using gr-
> > > > inspector
> > > > > > > > _______________________________________________
> > > > > > > > Discuss-gnuradio mailing list
> > > > > > > > address@hidden
> > > > > > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > *Daniel Andrés Palacios Carabalí*
> > > > > > *Student of Telemathics engineering*
> > > > > > *Icesi University- Cali, Colombia*
> > > > > > *===========================*
> > > > > > *Estudiante de Ingeniería Telemática*
> > > > > > *Universidad Icesi. - Cali, Colombia*
> > > > > > _______________________________________________
> > > > > > Discuss-gnuradio mailing list
> > > > > > address@hidden
> > > > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > > > > >
> > > > >
> > > >
> > > > _______________________________________________
> > > > Discuss-gnuradio mailing list
> > > > address@hidden
> > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > >
> > >
> > > --
> > > Daniel Andrés Palacios Carabalí
> > > Student of Telemathics engineering
> > > Icesi University- Cali, Colombia
> > > ===========================
> > > Estudiante de Ingeniería Telemática
> > > Universidad Icesi. - Cali, Colombia
> >
> >
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>