Loading ...
Sorry, an error occurred while loading the content.

Re: FM demodulator question

Expand Messages
  • sm5le
    Fine , now it works. /Sven
    Message 1 of 10 , Nov 21, 2012
    • 0 Attachment
      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
      > > > >
      > > > >
      > > >
      > >
      > >
      >
    Your message has been successfully submitted and would be delivered to recipients shortly.