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FM demodulator question

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  • sm5le
    Hi all I use the FM demodulator. Can one set +/- in frequency in waterfall, for the demodulated signal (zero in the middle)? I want to see (resolve) positve
    Message 1 of 10 , Nov 17 11:45 AM
      Hi all
      I use the FM demodulator.
      Can one set +/- in frequency in waterfall, for the demodulated signal (zero in the middle)? I want to see (resolve) positve and negative deviation for the detected signal.

      Tnx Sven
    • Jurgen Bartels
      ... The demodulated signal has no negative frequency. You probably mean the time domain signal? That is not a waterfall, so use the scope for that Jurgen
      Message 2 of 10 , Nov 17 2:18 PM
        > I use the FM demodulator.
        > Can one set +/- in frequency in waterfall, for the demodulated signal (zero in
        > the middle)? I want to see (resolve) positve and negative deviation for the
        > detected signal.

        The demodulated signal has no negative frequency.
        You probably mean the time domain signal? That is not a waterfall, so use the
        scope for that



        Jurgen
      • sm5le
        The output (in hardwere at least) from a FM discriminator schould be DC at center frequency and then postitive/negative output swing, representing the
        Message 3 of 10 , Nov 18 1:22 AM
          The output (in hardwere at least)
          from a FM discriminator schould be DC at center frequency and then postitive/negative output swing, representing the modulation from transmiter. But maybe not so in SpecLab?

          tnx /Sven

          --- In SpectrumLabUsers@yahoogroups.com, "Jurgen Bartels" <jurgenb2@...> wrote:
          >
          > > I use the FM demodulator.
          > > Can one set +/- in frequency in waterfall, for the demodulated signal (zero in
          > > the middle)? I want to see (resolve) positve and negative deviation for the
          > > detected signal.
          >
          > The demodulated signal has no negative frequency.
          > You probably mean the time domain signal? That is not a waterfall, so use the
          > scope for that
          >
          >
          >
          > Jurgen
          >
        • Jurgen Bartels
          ... Yes it is Sven, click on Component / Output Monitor Jurgen
          Message 4 of 10 , Nov 18 2:04 AM
            > The output (in hardwere at least)
            > from a FM discriminator schould be DC at center frequency and then
            > postitive/negative output swing, representing the modulation from transmiter.
            > But maybe not so in SpecLab?

            Yes it is Sven,
            click on Component / Output Monitor



            Jurgen
          • wolf_dl4yhf
            Hi Jurgen and Sven, I can only second Jurgen s post. An FM demodulator (like the one implemented in Spectrum Lab) will not produce negative frequencies in the
            Message 5 of 10 , Nov 18 4:40 AM
              Hi Jurgen and Sven,


              I can only second Jurgen's post. An FM demodulator (like the one implemented in Spectrum Lab) will not produce negative frequencies in the spectrum display, not even if the spectrum analyser would operate in I/Q mode. If the demodulator's center frequency doesn't match the transmitter's "carrier", it would output a slightly positive or negative DC voltage, but you cannot see that in a spectrum display.
              If the AFC (automatic frequency control) is enabled for the FM demodulator, you won't even see that.
              The demodulator can only be controlled through a popup menu in the 'circuit' window - see manual.

              73,
                Wolf .



              Am 17.11.2012 23:18, schrieb Jurgen Bartels:
               

              > I use the FM demodulator.
              > Can one set +/- in frequency in waterfall, for the demodulated signal (zero in
              > the middle)? I want to see (resolve) positve and negative deviation for the
              > detected signal.

              The demodulated signal has no negative frequency.
              You probably mean the time domain signal? That is not a waterfall, so use the
              scope for that

              Jurgen


            • sm5le
              Tnx all. My question was not that clear (reading it myself later, i did not know waht I mendt :-) New try: Is is possible to have waterfall showing +/-devation
              Message 6 of 10 , Nov 20 1:37 AM
                Tnx all.
                My question was not that clear (reading it myself later, i did not know waht I mendt :-)

                New try:
                Is is possible to have waterfall showing +/-devation from a nominal frequency.
                Assume: I have 600 Hz as center frequency , should show zero Hz at waterfall , then it moves to 610 Hz the waterfall should show 10hz up (positve) , then it moves to 590 Hz the waterfall should show minus 10 Hz.
                Whas that clearer; I doubt that :-)

                /Sven

                --- In SpectrumLabUsers@yahoogroups.com, wolf_dl4yhf <dl4yhf@...> wrote:
                >
                > Hi Jurgen and Sven,
                >
                >
                > I can only second Jurgen's post. An FM demodulator (like the one
                > implemented in Spectrum Lab) will not produce negative frequencies in
                > the spectrum display, not even if the spectrum analyser would operate in
                > I/Q mode. If the demodulator's center frequency doesn't match the
                > transmitter's "carrier", it would output a slightly positive or negative
                > DC voltage, but you cannot see that in a spectrum display.
                > If the AFC (automatic frequency control) is enabled for the FM
                > demodulator, you won't even see that.
                > The demodulator can only be controlled through a popup menu in the
                > 'circuit' window - see manual.
                >
                > 73,
                > Wolf .
                >
                >
                >
                > Am 17.11.2012 23:18, schrieb Jurgen Bartels:
                > >
                > > > I use the FM demodulator.
                > > > Can one set +/- in frequency in waterfall, for the demodulated
                > > signal (zero in
                > > > the middle)? I want to see (resolve) positve and negative deviation
                > > for the
                > > > detected signal.
                > >
                > > The demodulated signal has no negative frequency.
                > > You probably mean the time domain signal? That is not a waterfall, so
                > > use the
                > > scope for that
                > >
                > > Jurgen
                > >
                > >
                >
              • Jurgen Bartels
                ... Yes, connect spectrum to L4 In FFT window set Freq-Shift accordingly Or alternatively set the offset of the freq-scale accordingly Jurgen
                Message 7 of 10 , Nov 20 1:45 AM
                  > Is is possible to have waterfall showing +/-devation from a nominal
                  > frequency.
                  > Assume: I have 600 Hz as center frequency , should show zero Hz at waterfall ,
                  > then it moves to 610 Hz the waterfall should show 10hz up (positve) , then it
                  > moves to 590 Hz the waterfall should show minus 10 Hz.

                  Yes,

                  connect spectrum to L4
                  In FFT window set Freq-Shift accordingly

                  Or alternatively set the offset of the freq-scale accordingly



                  Jurgen
                • sm5le
                  Tnx Sven
                  Message 8 of 10 , Nov 20 12:05 PM
                    Tnx

                    Sven

                    --- In SpectrumLabUsers@yahoogroups.com, "Jurgen Bartels" <jurgenb2@...> wrote:
                    >
                    > > Is is possible to have waterfall showing +/-devation from a nominal
                    > > frequency.
                    > > Assume: I have 600 Hz as center frequency , should show zero Hz at waterfall ,
                    > > then it moves to 610 Hz the waterfall should show 10hz up (positve) , then it
                    > > moves to 590 Hz the waterfall should show minus 10 Hz.
                    >
                    > Yes,
                    >
                    > connect spectrum to L4
                    > In FFT window set Freq-Shift accordingly
                    >
                    > Or alternatively set the offset of the freq-scale accordingly
                    >
                    >
                    >
                    > Jurgen
                    >
                  • wolf_dl4yhf
                    Hi Sven, Set the Radio Frequency Offset to -600 Hz. In the last version, this item has been moved to the configuration screen, on the tab Spectrum (2) . In
                    Message 9 of 10 , Nov 20 12:35 PM
                      Hi Sven,

                      Set the 'Radio Frequency Offset' to -600 Hz. In the last version, this item has been moved to the configuration screen, on the tab 'Spectrum (2)'. In older versions there was an extra field for this on the main window, but I was running out of space in the main window. The FFT will still deliver signals from 0 Hz to half the sampling rate, but they will simply be labelled with a shifted frequency scale on the spectrum and spectrogram display (or both). Then zoom into '0 Hz' in the center, which is in reality 600 Hz in the input signal.

                      All the best,
                        Wolf .


                      Am 20.11.2012 10:37, schrieb sm5le:
                       

                      Tnx all.
                      My question was not that clear (reading it myself later, i did not know waht I mendt :-)

                      New try:
                      Is is possible to have waterfall showing +/-devation from a nominal frequency.
                      Assume: I have 600 Hz as center frequency , should show zero Hz at waterfall , then it moves to 610 Hz the waterfall should show 10hz up (positve) , then it moves to 590 Hz the waterfall should show minus 10 Hz.
                      Whas that clearer; I doubt that :-)

                      /Sven

                      --- In SpectrumLabUsers@yahoogroups.com, wolf_dl4yhf <dl4yhf@...> wrote:
                      >
                      > Hi Jurgen and Sven,
                      >
                      >
                      > I can only second Jurgen's post. An FM demodulator (like the one
                      > implemented in Spectrum Lab) will not produce negative frequencies in
                      > the spectrum display, not even if the spectrum analyser would operate in
                      > I/Q mode. If the demodulator's center frequency doesn't match the
                      > transmitter's "carrier", it would output a slightly positive or negative
                      > DC voltage, but you cannot see that in a spectrum display.
                      > If the AFC (automatic frequency control) is enabled for the FM
                      > demodulator, you won't even see that.
                      > The demodulator can only be controlled through a popup menu in the
                      > 'circuit' window - see manual.
                      >
                      > 73,
                      > Wolf .
                      >
                      >
                      >
                      > Am 17.11.2012 23:18, schrieb Jurgen Bartels:
                      > >
                      > > > I use the FM demodulator.
                      > > > Can one set +/- in frequency in waterfall, for the demodulated
                      > > signal (zero in
                      > > > the middle)? I want to see (resolve) positve and negative deviation
                      > > for the
                      > > > detected signal.
                      > >
                      > > The demodulated signal has no negative frequency.
                      > > You probably mean the time domain signal? That is not a waterfall, so
                      > > use the
                      > > scope for that
                      > >
                      > > Jurgen
                      > >
                      > >
                      >


                    • sm5le
                      Fine , now it works. /Sven
                      Message 10 of 10 , Nov 21 12:17 PM
                        Fine , now it works.
                        /Sven


                        --- In SpectrumLabUsers@yahoogroups.com, wolf_dl4yhf <dl4yhf@...> wrote:
                        >
                        > Hi Sven,
                        >
                        > Set the 'Radio Frequency Offset' to -600 Hz. In the last version, this
                        > item has been moved to the configuration screen, on the tab 'Spectrum
                        > (2)'. In older versions there was an extra field for this on the main
                        > window, but I was running out of space in the main window. The FFT will
                        > still deliver signals from 0 Hz to half the sampling rate, but they will
                        > simply be labelled with a shifted frequency scale on the spectrum and
                        > spectrogram display (or both). Then zoom into '0 Hz' in the center,
                        > which is in reality 600 Hz in the input signal.
                        >
                        > All the best,
                        > Wolf .
                        >
                        >
                        > Am 20.11.2012 10:37, schrieb sm5le:
                        > >
                        > > Tnx all.
                        > > My question was not that clear (reading it myself later, i did not
                        > > know waht I mendt :-)
                        > >
                        > > New try:
                        > > Is is possible to have waterfall showing +/-devation from a nominal
                        > > frequency.
                        > > Assume: I have 600 Hz as center frequency , should show zero Hz at
                        > > waterfall , then it moves to 610 Hz the waterfall should show 10hz up
                        > > (positve) , then it moves to 590 Hz the waterfall should show minus 10 Hz.
                        > > Whas that clearer; I doubt that :-)
                        > >
                        > > /Sven
                        > >
                        > > --- In SpectrumLabUsers@yahoogroups.com
                        > > <mailto:SpectrumLabUsers%40yahoogroups.com>, wolf_dl4yhf <dl4yhf@>
                        > > wrote:
                        > > >
                        > > > Hi Jurgen and Sven,
                        > > >
                        > > >
                        > > > I can only second Jurgen's post. An FM demodulator (like the one
                        > > > implemented in Spectrum Lab) will not produce negative frequencies in
                        > > > the spectrum display, not even if the spectrum analyser would
                        > > operate in
                        > > > I/Q mode. If the demodulator's center frequency doesn't match the
                        > > > transmitter's "carrier", it would output a slightly positive or
                        > > negative
                        > > > DC voltage, but you cannot see that in a spectrum display.
                        > > > If the AFC (automatic frequency control) is enabled for the FM
                        > > > demodulator, you won't even see that.
                        > > > The demodulator can only be controlled through a popup menu in the
                        > > > 'circuit' window - see manual.
                        > > >
                        > > > 73,
                        > > > Wolf .
                        > > >
                        > > >
                        > > >
                        > > > Am 17.11.2012 23:18, schrieb Jurgen Bartels:
                        > > > >
                        > > > > > I use the FM demodulator.
                        > > > > > Can one set +/- in frequency in waterfall, for the demodulated
                        > > > > signal (zero in
                        > > > > > the middle)? I want to see (resolve) positve and negative deviation
                        > > > > for the
                        > > > > > detected signal.
                        > > > >
                        > > > > The demodulated signal has no negative frequency.
                        > > > > You probably mean the time domain signal? That is not a waterfall, so
                        > > > > use the
                        > > > > scope for that
                        > > > >
                        > > > > Jurgen
                        > > > >
                        > > > >
                        > > >
                        > >
                        > >
                        >
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