Hi Ashraf,
I don't want to complain much, but this feels like you're only giving us
fractions of the information that is easily available to you, but expect
us to guess what you're seeing; try to understand the situation of
someone who's trying to understand your problems:
now you've just sent us two uncommented screenshots, and we don't know
what situation you're actually showing -- is it what you see when
there's no signal? Is it what you see when there is signal? How do these
spectra look in comparison? Also, you haven't explained anything about
what you're transmitting, with which bandwidth, using which devices,
antennas, gains/powers etc.
The only thing that I can say for sure is that you're misunderstanding
the "bandwidth" parameter of the graphical sink: Of course, the sink
always displays the bandwidth of the sampled signal you send into it --
which, for complex signals, is the sampling rate, and the bandwidth
parameter just puts the numbers on the axis. The actual bandwidth you're
observing is 100kHz, not 2MHz! you need to modify the sampling rate if
you want to change that.
I remember we had a discussion on whether any GNU Radio sink actually
displays powers (in dBm) or just relative values (dB); this is exactly
the same! Frequency is displayed relative to the bandwidth you set in
the sink parameters -- it's not a quality inherent to the sequence of
numbers that is your digital signal.
Best regards,
Marcus
On 22.07.2015 19:32, Ashraf Younis wrote:
On Wed, Jul 22, 2015 at 12:01 PM, Marcus Müller
<marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>> wrote:
Hi Ashraf,
If you've configured the USRP source correctly, you're very likely
actually displaying the spectrum your digital receiver sees --
depending on the signal, you could a) actually be rising the power
level in that whole band, or b) maybe you're observing something
like saturation and hence intermodulation of additional signals.
You migth want to share what exactly you are observing, and what
exactly the signal is you're generating. Screenshots are easy to
make and to upload [1], so please illustrate a little better!
Best regards,
Marcus
[1] www.imgur.com <http://www.imgur.com>
On 22.07.2015 17:56, Ashraf Younis wrote:
Hello, the issue I am having is I cannot display a graph that
shows a wide range of frequencies and their power. When I attempt
it with the QT GUI Frequency in GRC, I get something similar to
the one in this video (FFT plot
<https://youtu.be/cygDXeZaiOM?t=3m49s>) but then I transmit a
signal in the range I am currently looking at and the whole
line moves up. This leads me to believe that I am no displaying
the whole range I desire, but in fact I am displaying the center
frequency and a small bandwidth around it. I want to, for
example, scan the 2.4 GHz range and see all of the channels and
their power. And when I transmit at a certain frequency, I see a
spike at the spot in the graph.
How do I create that graph?
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