Re: [Discuss-gnuradio] Detailed Analysis

[Marcus Müller]

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Hi Paul,

waterfall seems to be exactly what you want - Fourier transform
amplitude over time.
Although I can see the need for different windows in special
applications, why are you not satisfied with the window choices the QT
as well as the WX waterfall plots offer?
And: Although there is a lot of sense in channel selection prior to
analysis, if you do directly adjacent channels anyway, and try to
correlate what happens in different channels, why not keep the full
bandwidth and just increase the DFT size instead? Since temporal
resolution constraints seem to be in the order of 0.1s, at your
physical sampling rates (N*1Msam/s) that offers large (>>1024) sizes.
Don't worry: Your computer should not take very long to calculate
20000-FFTs :) and you're doing this offline, anyway.

Anyway I think you're right, having a dynamically generated waterfall
is most probably not the right tool.
My weapon of choice for the analysis of offline (recorded) data is python:
Use the numeric data types of numpy[1], the algorithms in scipy, the
plotting functionality of matplotlib.pyplot [2], and the python shell
of my choice is bpython, although Ipython usually integrates better
with matplotlib[3].

Happy understanding your signal,
Marcus Müller

[1]  the same that GR uses
[2] strikingly similar to matlab, but not smothered by a terrible
programming language
[3]  If you're on the lookout for a little Matlabeske GUI, try
enthought canopy.
On 23.01.2014 01:26, Paul B. Huter wrote:
> Aditya:
> 
> I am looking at sections of my data, one-M at a time - that is,
> from 0 MHz to 1 MHz, 1 MHz to 2 MHz, etc. So, for example, when I
> look at 0-to-1 MHz, I am using an FFT set to FFT-size of 1000. My
> data is about 13 seconds long, and I am looking at it at a rate of
> 1 Hz (so I see about 13 updates). What I am trying to see is if the
> data at about nine seconds persists to the end of the data at 13
> seconds. I have tried holding the data at nine seconds and seeing
> if things keep matching up, but that is really not working out for
> me. I have yet to look at it from a Waterfall perspective, which
> may yield better results. However, in experimenting with the 
> Waterfall, I am unable to get the "window" to be set the way I can
> set it with the FFT plot. I am getting ready to grab another data
> set tomorrow, but I would like to do some analysis prior to getting
> another data file.
> 
> 
> On Wed, Jan 22, 2014 at 6:20 PM, Aditya Dhananjay
> <address@hidden> wrote:
> 
>> 
>> 
>> 
>> I am looking to do some detailed analysis of my recorded data. I
>> have been
>>> trying to look at the data in GNURadio using the FFT Plot, but
>>> I am having a hard time discerning things. Specifically, I am
>>> trying to see if a signal persists over a period of time. I am
>>> going to try and look at things with the Waterfall, but I am
>>> not sure that will be much better.
>>> 
>>> I am open to using another tool, such as Octave, if need be.
>>> 
>>> Any ideas?
>>> 
>> 
>> Hi Paul,
>> 
>> What problems are you facing with the FFT plot? How much data are
>> you trying to analyze?
>> 
>> If the problem is that the FFT plot exhausts data too quickly,
>> you can add a throttle block to slow things down.
>> 
>> Best, Aditya
>> 
> 
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
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