# Burst Tagger block - What I'm I doing wrong?

**URL:** <https://www.ruby-forum.com/t/burst-tagger-block-what-im-i-doing-wrong/241581>\
**Category:** GNU Radio\
**Created:** [April 16, 2015, 6:07pm UTC](https://www.ruby-forum.com/t/burst-tagger-block-what-im-i-doing-wrong/241581 "2015-04-16T18:07:11Z")\
**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:** [April 16, 2015, 6:07pm UTC](https://www.ruby-forum.com/t/burst-tagger-block-what-im-i-doing-wrong/241581/1 "2015-04-16T18:07:11Z")

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Hi all!

Im trying to implement a system that should change it’s normal  
functioning  
when another system with higher priority comes into play. For that, we  
have  
thought of two ways: changing the central frequency of our system of  
interest and/or stopping the sending process automaticaly.

Im in charge of the latter, and for that I’ve found that maybe the  
“burst  
tagger” block could be of use. As far as I have understood, that block  
adds  
SOB and EOB tags to the element that I’m about to send, and those are  
then  
understood in the UHD as metadata. Afterwards (and may be here is where  
I  
get a little bit confused or have the misconception of its  
functionality),  
‘if the UHD receives an EOB tag, it turns of the transmitter until a new  
SOB comes’. (I would also like to know if the part in between the  
single  
quotation marks is also right. I’ve checked the code for UHD sink and I  
still dont have this part 100% clear).

Now, comes my main question and the reason why I think Im getting the  
concept wrong: I apply a signal (sinus) at the first port of the burst  
tagger and on the second I apply what would be my detection of the other  
system. In order to see if the tags come or not, I connect at the output  
of  
the block a “Tag debug”, where I do can see that it is a ‘False’ tag  
when  
the trigger is \<=0 and ‘true’ when it is \>0. However, I still see the  
signal being sent through the USRP.

I dont know if the sinus signal is not suitable for this test  
experiment,  
or if actually the burst tagger does not do what I understood. If  
someone  
has a clearifying opinion or remark I would really appreciate it. I’ve  
checked some previous questions here in feeder and the example  
explanation  
was implemented as I did. Any comment will be highy welcomed.

Thank you in advance.

Regards,

Nicolas

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**Author:** ![budu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/b5e925/32.png) [@budu](https://www.ruby-forum.com/u/budu)\
**Post date:** [April 29, 2015, 4:37pm UTC](https://www.ruby-forum.com/t/burst-tagger-block-what-im-i-doing-wrong/241581/2 "2015-04-29T16:37:21Z")

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On Thu, Apr 16, 2015 at 12:05 PM, Nicolas Cuervo B. \<  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:

> understood in the UHD as metadata. Afterwards (and may be here is where I  
> the block a “Tag debug”, where I do can see that it is a ‘False’ tag when
> 
> Regards,
> 
> Nicolas

I think the issue is related to the fact that the gr-uhd and that  
burst\_tagger weren’t designed together. In fact, the burst tagger block  
came before the UHD blocks handled tags and there wasn’t any  
coordination.

First, place a tag\_debug block in the flowgraph after the burst\_tagger.  
That will make sure that the burst\_tagger is actually properly tagging  
bursts.

But the main problem is that the burst\_tagger produces tags with the key  
“burst” and the value true or false. You’ll need to edit this block to  
change it to using “tx\_sob” for the start of burst and “tx\_eob” for the  
end. That should get you closer to what you want.

Tom