Forum: GNU Radio WX GUI FFT sink block issues

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870082ae4406c8662f7c23913e67848c?d=identicon&s=25 ali hanif (Guest)
on 2014-04-23 09:06
(Received via mailing list)
I am facing issues regarding WX GUI fft sink block..
First that whatever center frequency i am providing it is showing a peak
at
that frequency whether input signal is there or not..??

Secondly there is a question that whether it can automatically shift to
the
frequency by detecting the frequency of the input signal or not??

Another issue in general that i am unable to use two sink blocks at the
same time..e.g.if i am using fft sink and scope sink then when i execute
it(i have no hardware attached uptill now)..then both plots are empty
and i
have to disable one of them to get working..??


any help would be appreciated..thnx in advance
360f4ba3903437de2b8d45ca3370d545?d=identicon&s=25 Attila Kinali (Guest)
on 2014-04-23 13:08
(Received via mailing list)
On Wed, 23 Apr 2014 12:04:52 +0500
ali hanif <alihanif799@gmail.com> wrote:

> I am facing issues regarding WX GUI fft sink block..
> First that whatever center frequency i am providing it is showing a peak at
> that frequency whether input signal is there or not..??

The peak means that there is a DC bias component in your signal. That's
pretty normal, depending on what kind of hardware you use.
E.g. a bladeRF will show it, while (at least some) RTL-SDR don't have
it.


> Secondly there is a question that whether it can automatically shift to the
> frequency by detecting the frequency of the input signal or not??

You can supply the center frequency to the block. You can specify it
as a variable to all blocks that need it, in order to have it to change
only at one place.

> Another issue in general that i am unable to use two sink blocks at the
> same time..e.g.if i am using fft sink and scope sink then when i execute
> it(i have no hardware attached uptill now)..then both plots are empty and i
> have to disable one of them to get working..??

That sounds weird. Can you show a screenshot of your GRC graph?
(unless you are using a coded flow graph, than that please).

      Attila Kinali

--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the
heap
    -- Tirin, The Dispossessed, U. Le Guin
7d89a70df32c0ae27c1235016f9e5441?d=identicon&s=25 Marcus Müller (Guest)
on 2014-04-23 14:53
(Received via mailing list)
Hi!
Just a side note: Try to replace your WX GUI widgets with QT ones (also
set the Generate Option to QT in GRC). They are pretty mature and work
well; also, in the long run, GNU Radio's going to move away from WX.

Greetings,
Marcus
2ab09aea210c3537da2c09c8d493f27c?d=identicon&s=25 sunkel (Guest)
on 2014-04-23 16:27
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hi,
I tried using QT GUI sink to measure frequency offset between 2
USRPs.but
when I click "Execute the flow graph",a window appears then in a blink
disappears.and i got this massage.did I set something wrong?

Generating: "/home/sdr/top_block.py"

Executing: "/home/sdr/top_block.py"

linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.007.000-1-stable

-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
Using Volk machine: sse4_1_32

>>> Done





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7d89a70df32c0ae27c1235016f9e5441?d=identicon&s=25 Marcus Müller (Guest)
on 2014-04-23 16:29
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Strange...
Are you sure you set the Generate Options to QT GUI (instead of WX)?

Greetings,
Marcus

On 23.04.2014 16:25, sunkel wrote:
> UHD_003.007.000-1-stable
>
>
> -- View this message in context:
> http://gnuradio.4.n7.nabble.com/WX-GUI-FFT-sink-bl...
>
>
Sent from the GnuRadio mailing list archive at Nabble.com.
>
> _______________________________________________ Discuss-gnuradio
> mailing list Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
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2ab09aea210c3537da2c09c8d493f27c?d=identicon&s=25 sunkel (Guest)
on 2014-04-23 16:38
(Received via mailing list)
im pretty sure I did that.i set Generate Options as QT GUI.
if I didnt set Generate Options i will get this error:


Generating: "/home/sdr/top_block.py"

Executing: "/home/sdr/top_block.py"

Traceback (most recent call last):
  File "/home/sdr/top_block.py", line 118, in <module>
    tb = top_block()
  File "/home/sdr/top_block.py", line 40, in __init__
    self._variable_qtgui_range_0_tool_bar = Qt.QToolBar(self)
TypeError: arguments did not match any overloaded call:
  QToolBar(QString, QWidget parent=None): argument 1 has unexpected type
'top_block'
  QToolBar(QWidget parent=None): argument 1 has unexpected type
'top_block'

>>> Done




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870082ae4406c8662f7c23913e67848c?d=identicon&s=25 ali hanif (Guest)
on 2014-04-24 05:37
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Hi Attila Kinali,
I don,t think it is the DC bias..as it is appearing at every center
frequency i provide and a DC bias is at zero frequency only..
870082ae4406c8662f7c23913e67848c?d=identicon&s=25 ali hanif (Guest)
on 2014-04-24 06:35
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For the last question,i have added a screen shot..see that there is no
signal in my time plot,just a line..
870082ae4406c8662f7c23913e67848c?d=identicon&s=25 ali hanif (Guest)
on 2014-04-24 06:39
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here is the GRC flow graph
95407eef371d1aa1a5696f52c8d70a0e?d=identicon&s=25 Ron Economos (Guest)
on 2014-04-24 09:34
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Attachment: signal.png (200 KB)
Wow, it's amazing that that flowgraph even works at all.
4.8 Gsps is an astronomical sample rate and shows
a basic misunderstanding of how GnuRadio and SDR
work.

GnuRadio is a baseband processing architecture. Your
SDR hardware (USRP, bladeRF, hackRF, etc.) is responsible
for translating the baseband to a radio frequency, not
GnuRadio.

I've attached a more reasonable flowgraph for you to experiment
with. Try some different parameters in the signal source and
note the effects. You can download the flowgraph here:

http://www.w6rz.net/signal.grc

Ron
630628b35d9a8bbc06ce7c62608841cc?d=identicon&s=25 Pitter Mayengbam (pitter)
on 2016-05-01 20:51
Taking the advantage of this wx gui fft sink block issue, i just want to
know about one problem i came across i.e. how can i get +ve amplitude
values of the fft spectrum(signal amplitude)? The values i got were
always -ve (the spectrum is shown below the 0 db amplitude). This
question might had been discussed earlier but I am new in GNU radio.
Anyone plz suggest me what cab be the solution.

regards
pitter
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