# Minimum amount of data to trigger WX GUI Scope Sink? and Ch 1 vs. Ch2 with Ch 3 vs. Ch 4

**URL:** <https://www.ruby-forum.com/t/minimum-amount-of-data-to-trigger-wx-gui-scope-sink-and-ch-1-vs-ch2-with-ch-3-vs-ch-4/238013>\
**Category:** GNU Radio\
**Created:** [December 11, 2013, 7:54pm UTC](https://www.ruby-forum.com/t/minimum-amount-of-data-to-trigger-wx-gui-scope-sink-and-ch-1-vs-ch2-with-ch-3-vs-ch-4/238013 "2013-12-11T19:54:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [December 11, 2013, 7:54pm UTC](https://www.ruby-forum.com/t/minimum-amount-of-data-to-trigger-wx-gui-scope-sink-and-ch-1-vs-ch2-with-ch-3-vs-ch-4/238013/1 "2013-12-11T19:54:30Z")

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Hi,

I am using WX GUI Scope Sink, and I have set the sample rate = 1M, same  
as the USRP. It seems that a minimum number of data points are required  
before anything appears on the plot - is that correct, and how can it be  
adjusted?

Also, I am looking at constellations, using the XY mode to show real and  
imaginary. It is possible to have multiple inputs, but is it possible to  
view multiple ‘series’ in XY mode?

I seem to be only able to choose Ch X vs Ch Y, e.g. Ch 1 vs. Ch 2 (  
Re(in1) vs. Im(in1) ) or Ch 1 vs. Ch 4 (Re(in1) vs. Im(in2)). I would  
like to see Ch 1 vs. Ch 2 and Ch 3 vs Ch 4 simultaneously?

Thanks in advance! 🙂

David

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<div class="post-metadata">

**Author:** ![divotdave](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/bbe5ce/32.png) [@divotdave](https://www.ruby-forum.com/u/divotdave)\
**Post date:** [December 12, 2013, 9:24pm UTC](https://www.ruby-forum.com/t/minimum-amount-of-data-to-trigger-wx-gui-scope-sink-and-ch-1-vs-ch2-with-ch-3-vs-ch-4/238013/2 "2013-12-12T21:24:47Z")

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The trigger of scope sink is not for XY mode.

If you want to view two complex signal simultaneous, then it seems you  
need  
two scope sinks.

If you dont see anything, maybe you have a block driving it that doesnt  
output anything until some condition is met.

On Wed, Dec 11, 2013 at 10:53 AM, David Halls