- Hi,

Am Donnerstag, den 31.05.2012, 03:54 +0200 schrieb ehydra:>

You can export the FFT, see here in general:

> Hi!

>

> 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

http://www.qsl.net/dl4yhf/speclab/textexpt.htm

and here in particular:

http://www.qsl.net/dl4yhf/speclab/textexpt.htm#export_fft_results

> with decimal point, not comma.

Maybe with the PAM-Function with continuous wave as modulation?

>

> But I can convert dB and comma if there is a problem.

>

> 2. My second question is: if it is possible to make a complex FFT to

> measure impedances and getting amplitude and phase back?

http://www.qsl.net/dl4yhf/speclab/phase_amplitude_monitor.htm

> Thank you -

Best Regards

> Henry

>

> --

> ehydra.dyndns.info

Christoph

--

Christoph Maurer B.Sc.

Technische Universität Darmstadt

Institut für Kernphysik

AG Strahlen- und Kernphysik

-Kosmische Plasmaphysik

Schlossgartenstr. 9

64289 Darmstadt

Office: S2|14-107

Tel.: (+49) 6151 16 4426 - Hello Henry,

I'm not an expert in spreadsheets (in fact I hate most of them, especially *xcel) so I cannot say how to produce a nice diagram from the data. But I'm sure it can be done, somehow. At least, with open office "Calc" I was able to import the FFT-logfile, and validate that the peak of DCF77 was where I expected it to be (in the file written by SL).

I have uploaded it as 'FFT_Export_Test_DCF77.txt' to my folder at the SL User group.

1024 FFT bins are exported in each line, beginning at approximately 77 kHz (that was entered in SL's FFT-export panel)

The first line in the file contains the headline (helpful when viewing the data with a stupid spreadsheet to see what the columns mean). Content, first part:

YYYY-MM-DD hh:mm:ss.s BW_Hz F1_Hz dB0 dB1 dB2 dB3 dB4

The second line is the first 'real data':

2012-06-09 17:15:43.3 1.4648 76999.1082 -108.3 -115.6 -117.1 -116.7

1.4648 ("BW_Hz") is the bin-width in Hertz.

76999.1082 ("F1_Hz") is the center frequency of the 1st bin in Hertz.

-108.3 [dB] is the value from the first exported bin (colum title "dB0") in dB.

The peak of DCF77 should be near 77.5 kHz. Calculate the bin-index :

(77500 Hz - 76999.1082 Hz) / 1.4648 Hz = 342 (rounded; zero-based index)

Thus the column titled "dB342" should contain the DCF77-peak.

Import the stuff with open office "Calc" (remember to set the language to English, otherwise the stupid decimal *comma* would be expected in the file, instead of the decimal point), and scroll that column into view.

Result:

dB341 = -65.5

dB342 = -62.1

dB343 = -66.6

which is the (correct) level of DCF77, as displayed in SL ("dB over full scale", thus negative).

A thought: It would be more user-friendly to use the frequency as column titles. But this will inevitably cause more trouble when the bin-width is less than one Hertz. Thus the simple numbering scheme.

All the best,

Wolf .

Am 08.06.2012 00:30, schrieb ehydra: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

>>

>>

>

>

--

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