826Re: [SpectrumLabUsers] Q: screen capture as CSV file?, complex FFT?
- Jun 7, 2012Thank 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 -
> 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
> 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:
>> 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:
>> I think the constant 0.3662 is just wrong.
>> Any idea to make things simpler?
>> - 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 .
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