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Re: Schuman Concverter .usr help

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  • JOS C
    Wolf, Ive had a chance to try Schumann .usr file and I have a few questions and comments. With the Test Oscillator On and using it as the LO source for the
    Message 1 of 7 , May 31, 2012
      Wolf,

      Ive had a chance to try Schumann .usr file and I have a few questions
      and comments.

      With the Test Oscillator On and using it as the LO source for the
      converter why does the OFFSET on the main screen still need to be
      set so that the LO corresponds to zero? When I first started using
      the Test Oscillator the zero frequency was at -10Hz.

      How is the Schumann frequency actually measured is it set up against
      the LO frequency or is it referenced against the main screen display?

      When viewing the Plotter graph the Schumann frequency is displayed.
      However it seems to be displayed in Peak which isn't to use full
      could this be changed to Smooth which may work better with noisy signals?
      Actually I think most people would only be interested in SR1 and SR2
      while you can see the others the are generally weak.

      When using the Test Oscillator the Sine works fine but I'm unable
      to change it to Rectangle (this probably wouldn't make much difference anyway)

      Thank again for your assistance the weather is bad here today no
      signals

      Joe wa9cgz
    • wolf_dl4yhf
      Hi Joe, ... Maybe your soundcard also has slighly different sampling rates for the ADC (input) and DAC (output). This can be defeated by entering the
      Message 2 of 7 , Jun 1, 2012
        Hi Joe,


        You wrote:
         


        Wolf,

        Ive had a chance to try Schumann .usr file and I have a few questions
        and comments.

        With the Test Oscillator On and using it as the LO source for the
        converter why does the OFFSET on the main screen still need to be
        set so that the LO corresponds to zero? When I first started using
        the Test Oscillator the zero frequency was at -10Hz.


        Maybe your soundcard also has slighly different sampling rates for the ADC (input) and DAC (output).
        This can be defeated by entering the 'calibrated' sampling rates in the calibration tables.
        The 'AM carrier' should be visible at precisely 0 Hz (because the offset for the spectrum display is the same as the AM carrier frequency).

        How is the Schumann frequency actually measured is it set up against
        the LO frequency or is it referenced against the main screen display?

        The peak-detection functions don't care about the offset for the visible frequency scale of the spectrum display.
        Thus the additions and subtractions in the definition table of the measuring channels (watch table).
        Technically, we're looking at the upper sideband of the amplitude modulated signal here.

        When viewing the Plotter graph the Schumann frequency is displayed.
        However it seems to be displayed in Peak which isn't to use full
        could this be changed to Smooth which may work better with noisy signals?

        It does smooth. If the plotter's scroll rate is slower than the FFT-calculation interval, the 'watches' collect multiple samples for each horizontal step of the plotter. If you plot the "average" value only (which is what my sample configuration does), the frequency readings are smoothed.

        Actually I think most people would only be interested in SR1 and SR2
        while you can see the others the are generally weak.

        Remove those measurement channels for the 3rd and 4th Schuman resonance from the watch definition table.
        Or simply turn off those channels for the display. Shouldn't be too difficult.


        When using the Test Oscillator the Sine works fine but I'm unable
        to change it to Rectangle (this probably wouldn't make much difference anyway)

        I also don't think this makes a difference, especially if the carrier signal drives a switching modulator (ring modulator, analog switches, or whatever).

        All the best,
          Wolf .
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