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826Re: [SpectrumLabUsers] Q: screen capture as CSV file?, complex FFT?

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  • ehydra
    Jun 7, 2012
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      Thank you Wolf!

      It looks to me as a problem if the display FFT bin numbers are not equal
      to the exported bin numbers. Your example shows both set to the same value.
      If I set the first bin to zero, I get a big file without interesting
      ranges (below 50KHz).

      I tried to reduce the file size to the minimum reasonable size to reduce
      the personal work lacking experience with Perl converting the file
      format. I have to hand-calculate all the frequency values... because SL
      doesn't export this value for every magnitude value in the list.

      Hm. I will check another time.

      Good night -
      Henry



      wolf_dl4yhf schrieb:
      > Hi Henry,
      >
      > I just made a quick check for the FFT export function, and -so far-
      > couldn't find an error in the indicated frequency bin width. But I
      > exported *all* frequency bins, not just a range. Anyway this doesn't
      > affect the width of a single bin.
      >
      > Here's what I did:
      > - Sample rate 11025 Hz (my E-MU is currently on duty for another project..)
      > - 8192-point FFT
      >
      > Indicated on the FFT control panel:
      > >
      > Effect of FFT settings with fs= 11.0250 kHz:
      > Width of one FFT-bin: 1.34583 Hz
      > <
      >
      > Resulting FFT logfile (first line with real data, not the headline):
      >
      > 2012-06-07 20:31:58.7 1.3458 0.0000 -81.6 -103.1 -79.6
      > -66.7
      >
      > So we've got date, time, bin width in Hertz, and frequency of the 1st
      > bin in Hz (here: 0 Hz for the 'DC' component).
      >
      > I will try this again with the E-MU at 192 kS/sec and DCF77 as soon as
      > time permits.
      >
      >
      > All the best,
      > Wolf .
      >
      >
      > Am 07.06.2012 21:31, schrieb ehydra:
      >>
      >> Hi Wolf -
      >>
      >> I made the experiment:
      >> Capturing a DCF77 ferrite-antenna FFT into a file.
      >>
      >> There are two problems:
      >> 1. The FFT bin frequency is not in the list
      >> 2. The FFT bins width are not synchronized between capturing file and
      >> screen measurement
      >>
      >> Look here:
      >> http://ehydra.dyndns.info/NG/SpectrumLabUsers/curve-fitter/SL_FFT_bins.png
      >>
      >>
      >> The first diagram is the actual data file. The second diagram shows a
      >> 'perfect antenna' (actual with a lower peak frequency because I want to
      >> run the fitter in LTspice thereafter). The peak at 77.5KHz in the
      >> captured data is completely lost in the FFT! I think because the bins
      >> are smaller than captured in file.
      >>
      >> I set:
      >> 1. Number of exported FFT bins: 64
      >> 2. Frequency of first FFT bin [Hz]: 50000
      >> 3. Running EMU0202 at 192KHz
      >>
      >> Is there a way to make SL more compatible to LTspice input format?
      >> I hand-formatted the FFT capture file to look like this:
      >> http://ehydra.dyndns.info/NG/SpectrumLabUsers/curve-fitter/DCF77.sub (It
      >> is a text file)
      >>
      >> This is the origin capture file:
      >> http://ehydra.dyndns.info/NG/SpectrumLabUsers/curve-fitter/DCF77.csv
      >>
      >> I think the constant 0.3662 is just wrong.
      >>
      >> Any idea to make things simpler?
      >>
      >> Thanks!
      >>
      >> - Henry
      >>
      >> wolf_dl4yhf schrieb:
      >> > Am 31.05.2012 20:08, schrieb ehydra:
      >> >>
      >> >> wolf_dl4yhf schrieb:
      >> >> >> 1. I need the FFT spectrum as a captured screen file but not as
      >> >> picture.
      >> >> >> It should be a CSV file or such. Is this possible? I looked in the
      >> >> >> online help but there is only doc for pictures. Say something like:
      >> >> >> frequency SPACE linearAmplitude CRLF
      >> >> >>
      >> >> >> with decimal point, not comma.
      >> >> >>
      >> >> > Not necessarily CSV, but this may be similar to what you are looking
      >> >> for:
      >> >> >
      >> >> > http://www.qsl.net/dl4yhf/speclab/textexpt.htm#export_fft_results
      >> >> >
      >> >>
      >> >> Looks like all is in one line. Hm. I will try this converting it with
      >> >> Perl.
      >> >>
      >> > Yes, of course. One line per FFT. Many lines for many FFTs ;-)
      >> >
      >> >
      >> > Cheers,
      >> > Wolf .
      >> >
      >>
      >> --
      >> ehydra.dyndns.info
      >>
      >>
      >
      >

      --
      ehydra.dyndns.info
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