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Using Matlab, I've made some random noise, filtered it and then successfully saved it as a gnuradio readable file for a file source. Once used in gnuradio, I set the file source to repeat and then viewed it using QT Gui Frequency Sink. I can see the filtered noise fine, but every now and then (every 10 seconds or so), the spectrum will drop in power and jump around for around a tenth of a second, then return back to normal power. My sample rate for the matlab filter is 320k and same with my gnuradio sample rate if that matters.

I think it may have to do with the fact that the noise generated on matlab is going to be a sequence that is repeated on gnuradio. I think the discontinuity happens right when the sequence repeats. Any idea how I can stop this discontinuity so I can transmit without having to worry about it? If I'm missing any info, please let me know and I'll edit the question. Thanks in advance.

Matlab SPTool parameters used to create the filtered noise

GNU Radio Flow Chart

QT GUI Frequency Sink Output

NOTE: I needed to create a matlab binary file to be able to read it on GNU Radio. GNU Radio reads the binary file from my desktop, then uses the information as the file source.

BBEng
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  • Maybe you can post your code or at least the relevant parts? It's hard to imagine what you're doing. – 10a Aug 09 '17 at 06:48
  • Well the filtered noise was created using SPTool on Matlab. You just put in the parameters and you can create the filtered noise easily. I'll post a picture of that. As for the GNU Radio part, I will post the flow graph as well. There is no code that I have created, only generated code from these two tools. I have also added a picture of the frequency sink display without the discontinuity. – BBEng Aug 09 '17 at 19:46
  • UPDATE: I've realized the discontinuities aren't due to some repeat. They are pretty random. I recorded the time between each discontinuity and it is definitely random. I still don't know what is causing them though. – BBEng Aug 10 '17 at 15:33
  • I can't find it either, sorry. – 10a Aug 11 '17 at 07:22

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