# Problem with Probe Signal Vector Block

**URL:** <https://www.ruby-forum.com/t/problem-with-probe-signal-vector-block/231430>\
**Category:** GNU Radio\
**Created:** [August 7, 2014, 5:16pm UTC](https://www.ruby-forum.com/t/problem-with-probe-signal-vector-block/231430 "2014-08-07T17:16:33Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [August 7, 2014, 5:16pm UTC](https://www.ruby-forum.com/t/problem-with-probe-signal-vector-block/231430/1 "2014-08-07T17:16:33Z")

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Hi,

I made a Flowgraph in GNU Radio which shows me the FFT of the samples  
that are sent by a Raspberry Pi over TCP. It looks like this:

Osmosdr Source -\> Stream to Vector -\> FFT -\> Complex to Mag -\> Log10 -\>  
Vector to Stream -\> Moving Average -\> Stream to Vector -\> Probe Signal  
Vector

I want to save the values of the FFT in a list in my Python program  
later. Now what I tried to do was to plot the probed vector with  
Matplotlib. I also replaced the last Stream to Vector Block and the  
Probe Block with a QT Time Sink to control the output. But the picture I  
get with Matplotlib is totally different. So my question is if this is a  
problem of how to do the probes on the signal vector or if it could be a  
problem of Matplotlib.

Thank you in advance!