Re: [Discuss-gnuradio] Detailed Analysis

[Marcus Müller]

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Forgot to mention: Try the gr_plot_fft[...] tools that come with
gnuradio, they basically do the python stuff for you. Look at the
options to set physical sampling freq etc.

On 23.01.2014 08:27, Marcus Müller wrote:
> 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
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
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