# Top-block does not find Probe Signal block

**URL:** <https://www.ruby-forum.com/t/top-block-does-not-find-probe-signal-block/241365>\
**Category:** GNU Radio\
**Created:** [April 1, 2015, 3:02pm UTC](https://www.ruby-forum.com/t/top-block-does-not-find-probe-signal-block/241365 "2015-04-01T15:02:04Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [April 1, 2015, 3:02pm UTC](https://www.ruby-forum.com/t/top-block-does-not-find-probe-signal-block/241365/1 "2015-04-01T15:02:04Z")

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Hello GNUR’s!

I am currently working with a SDR dongle which I want to lock at four  
different frequencies to see four consecutive parts of the spectrum. I  
have to do so because the sampling rate is not enough (2.4 MHz) to see  
at one glance the bandwidth I need (8 MHz). To achieve so I am  
multiplexing the values I want to lock my dongle to but I am getting  
some errors using the pair of blocks “Probe Signal” and “Function Probe”  
(see the flowgraph in [1] and errors trace [2]). By enabling/disabling  
some blocks I have guessed that the error about the overflow is caused  
by the WX GUI Number Sink, while the error of the non-existing attribute  
appears when I make use of the “variable” defined by the block Function  
Probe.

Of course I have followed the tutorial [3] and still couldn’t make it to  
work.  
Thank you very much in advance.

Greetings,  
Alejandro

[1] [http://imagizer.imageshack.us/a/img673/6338/mw0don.png](http://imagizer.imageshack.us/a/img673/6338/mw0don.png)  
[2] [http://pastebin.com/Kmxyw250](http://pastebin.com/Kmxyw250)  
[3]  
[https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided\_Tutorial\_GRC/61#241-Examining-the-Probe-Signal-Block](https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_GRC/61#241-Examining-the-Probe-Signal-Block)