# Strange behaviour

**URL:** <https://www.ruby-forum.com/t/strange-behaviour/242875>\
**Category:** GNU Radio\
**Created:** [August 4, 2015, 3:09pm UTC](https://www.ruby-forum.com/t/strange-behaviour/242875 "2015-08-04T15:09:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Sadaf\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@Sadaf\_N](https://www.ruby-forum.com/u/Sadaf_N)\
**Post date:** [August 4, 2015, 3:09pm UTC](https://www.ruby-forum.com/t/strange-behaviour/242875/1 "2015-08-04T15:09:12Z")

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Hi,

I’m seeing some strange behaviour in Gnuradio that i cannot explain.  
Subtracting the same value from each other should return zero, If I’m  
not  
mistaken. And why is there a dip in the center of my X310 stream? No  
signal  
is connected to the USRP.

What am I missing?

Kind Regards  
Simon

---

<div class="post-metadata">

**Author:** ![solvhammer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e19adc/32.png) [@solvhammer](https://www.ruby-forum.com/u/solvhammer)\
**Post date:** [August 4, 2015, 3:22pm UTC](https://www.ruby-forum.com/t/strange-behaviour/242875/2 "2015-08-04T15:22:39Z")

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Hi Simon,

I recommend using QT GUIs. WX GUI will be removed eventually.

‘stream to streams’ does not duplicate samples. In your case the first  
sample goes to output 0 and the second sample goes to output 1.

For AWGN you should observe another noise for in your FFT plot.

Your received signal is not a perfect AWGN signal. e.g. your dip is  
probably some 1/f noise caused by some analog part in your USRP. Have  
a look at the unprocessed samples form the USRP source.

happy hacking  
Johannes

On 04.08.2015 15:07, Simon Olvhammar wrote:

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> [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)

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