- Hi Ben,

Use the FFT-export function. It exports the fourier-transformed data from the spectrum analyser as text file. You can define the frequency range of interest (number of frequency bins, and start frequency).

Details in the manual:

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

Cheers,

Wolf .

Am 06.03.2013 15:41, schrieb M. Ben Schuetz:For optical SETI I am looking at very low frequencies from 0.01 to 2

Hz. Calculations suggest that fewer than 1 in 10 transmitted pulses

might be detectable. Thus, I need to accumulate data over several hours

and then analyze that data for periodic pulses. The "spectrum.save()"

command works fine, but I don't need to save the bins at frequencies

greater than 2 Hz. Can anyone suggest how to truncate the data such

that only those bins are saved?

Best from Ben

KG4LRA

Panama

- --- In SpectrumLabUsers@yahoogroups.com, kd7ts <kd7ts@...> wrote:
>

Thanks Mike,

> On Wed, 06 Mar 2013 06:41:29 -0800, M. Ben Schuetz <kg4lra@...>

> wrote:

>

> > For optical SETI I am looking at very low frequencies from 0.01 to 2

> > Hz. Calculations suggest that fewer than 1 in 10 transmitted pulses

> > might be detectable. Thus, I need to accumulate data over several hours

> > and then analyze that data for periodic pulses. The "spectrum.save()"

> > command works fine, but I don't need to save the bins at frequencies

> > greater than 2 Hz. Can anyone suggest how to truncate the data such

> > that only those bins are saved?

> >

> > Best from Ben

> > KG4LRA

> > Panama

>

>

> Hi Ben

>

> It seems you are familiar with SpecLab, so hopefully this is useful. I use

> the waterfall screen as a calculator to find the start frequency and

> number of bins to save by setting the width to what I want to have saved

> in the FFT Export function.

> This can be on a button, but I use it from the conditional actions, and

> display the variables on a button.

> If you want to save 2 Hz of bins, set the screen width to 2 Hz, and the

> start freq and number of bins are displayed. Enter these numbers in the

> FFT Export window.

>

> IF13=always

> THEN13=binwidth=cfg.NominalAudioSR

> /(cfg.FFTSize*cfg.FFTInputDec):bins=((water.f_max-water.f_min)/binwidth):startfreq=water.f_min

>

> This works by finding the width of one bin

>

> binwidth=cfg.NominalAudioSR /(cfg.FFTSize*cfg.FFTInputDec)

>

> then, with binwidth we can find how many bins are displayed on the

> waterfall

>

> bins=((water.f_max-water.f_min)/binwidth)

>

> and start freq is just the lowest frequency

>

> startfreq=water.f_min

>

> This is not automatic, but is the easiest method I have found. Once the

> numbers are entered, you may reset the waterfall to display whatever you

> like.

>

> This is not spectrum save. It is FFT export.

>

> Mike

>

Thanks Ben,

"

For optical SETI I am looking at very low frequencies from 0.01 to 2

Hz.

"

I am interested in processing infrasounds < 20Hz with SL.

Tell me how to implement your script lines into SL as conditional action/s and what are your results in case of infrasounds or SETI.

darius - Hi Darius,

At the present, I am not using any script lines or working with conditional actions other than automatic screen capture. The reasons for this are that my efforts for the past several years have been put into developing a detector of very high sensitivity and selectivity. As an example, the photomultiplier output pulses from star light are approximately 2 ns wide and at pulse rates up to 1 MHz. The pulses are then discriminated with a window comparator, saving the mid-range pulse heights which are stretched to 40 ns. They are the raw data having a "standard" pulse height and width.

I'm looking for groups of non-stellar pulses spread out over 100 to 300 ns. Not being very accomplished in digital techniques, I opted to integrate the 40 ns pulses and then detect closely grouped pulses with a comparator. The comparator output pulses are then stretched to 35 us and fed to S.L.

Stellar photons are randomly distributed in time, conforming to Poisson statistics. Thus, given a constant rate of detection, one can calculate the probability of n photons being detected in any time interval. When there are extra photons in ~10^-7 seconds, they are of interest.

Remarkably, with S.L., as few as 3, 2 ns pulses at a rep rate of a few tenths of a second can be easily discerned against a very low background, <-80 dB.

There is a lot more to it than that, but that is the short version of the story.

So, my observing time is all eyeballs. I am hopeful that the latest version of detector (going on the telescope for the first time tonight) will be such that I can spend some time with S.L. to ease the eyeball attention.

Best,

Ben

----------------------------------------------"

For optical SETI I am looking at very low frequencies from 0.01 to 2

Hz.

"

I am interested in processing infrasounds < 20Hz with SL.

Tell me how to implement your script lines into SL as conditional action/s and what are your results in case of infrasounds or SETI.

darius