Forum: GNU Radio A Question on WX GUI FFT Sink

Hello,

I have a simple GRC demo where the USRP source goes to a WX GUI FFT sink
and WX GUI Scope sink. They appear to be a good tools for sanity checks.
One feature I don't find however but I think should be quite necessary 
is
when one needs to examine a portion of the FFT spectrum more closely. 
But I
don't find an option where one can specify the start and stop frequency 
for
the FFT spectrum display. Am I missing something?

Thanks,

LD

On 09/28/2012 02:15 PM, LD Zhang wrote:
> Hello,
>
> I have a simple GRC demo where the USRP source goes to a WX GUI FFT sink
> and WX GUI Scope sink. They appear to be a good tools for sanity checks.
> One feature I don't find however but I think should be quite necessary is
> when one needs to examine a portion of the FFT spectrum more closely. But I
> don't find an option where one can specify the start and stop frequency for
> the FFT spectrum display. Am I missing something?
>

WX FFT sink cant do this. But...

FWIW, the QT gui FFT display sink does have a zoom feature.

-josh

>
> WX FFT sink cant do this. But...
>
> FWIW, the QT gui FFT display sink does have a zoom feature.
>
> -josh
>
> _______________________________________________
You can do the zooming in the flow-graph.   multimode does this with
wxGUI widgets.


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

I tried to find in the QT GUI Widgets category an item that does FFT. 
But
don't find one. I wonder what is meant by the "QT GUI FFT display"?

Thanks,

LD

Well I should have been more patient before I sent out the last email. 
It
turns out for the functionality I want (flexible zoom in display of the 
fft
spectrum) the block is called simply "QT GUI sink", if I am not 
mistaken.

When I tried, there is the error message:

-------------------------------------------------------
Traceback (most recent call last):
  File "/home/ldz/usrp_tests/top_block.py", line 75, in <module>
    tb = top_block()
  File "/home/ldz/usrp_tests/top_block.py", line 58, in __init__
    self.top_layout.addWidget(self._qtgui_sink_x_0_win)
  File 
"/usr/local/lib/python2.7/dist-packages/gnuradio/gr/top_block.py",
line 94, in __getattr__
    return getattr(self._tb, name)
AttributeError: 'gr_top_block_sptr' object has no attribute 'top_layout'
-----------------------------------------------------------------------------------------------------

I took a look in the top_block.py in my test directory. But I don't
understand the problem. I have not yet become accustomed to the python
environment.

Please off suggestions. Thanks.

LD

On Mon, Oct 1, 2012 at 4:35 PM, LD Zhang <ldz10565@gmail.com> wrote:
>   File "/home/ldz/usrp_tests/top_block.py", line 58, in __init__
>
> Please off suggestions. Thanks.
>
> LD

In the Options blocks, you have to change from using WXGUI to QTGUI.

And just use the QT Sink block. From there, you can switch between the
FFT, spectrogram, time, and constellation modes.

Tom