# Phase change for Transmitted Signal Bursts - The relation to clock?

**URL:** <https://www.ruby-forum.com/t/phase-change-for-transmitted-signal-bursts-the-relation-to-clock/246012>\
**Category:** GNU Radio\
**Created:** [August 8, 2013, 11:26pm UTC](https://www.ruby-forum.com/t/phase-change-for-transmitted-signal-bursts-the-relation-to-clock/246012 "2013-08-08T23:26:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\
**Post date:** [August 8, 2013, 11:26pm UTC](https://www.ruby-forum.com/t/phase-change-for-transmitted-signal-bursts-the-relation-to-clock/246012/1 "2013-08-08T23:26:28Z")

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Hi,

I am transmitting a series of BPSK burst signal and try to observe the  
phase distortion for the BPSK signal on air. But it is found that the  
Phases of different BPSK bursts are different.  
I think this change is caused by the fact that the ADC clock phases are  
different for the starts of every signal burst. But I don’t know more  
details on this mechanism.

BR,

–

Alex,  
_Dreams can come true just believe._

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**Author:** ![akeem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/54ee81/32.png) [@akeem](https://www.ruby-forum.com/u/akeem)\
**Post date:** [August 9, 2013, 12:50am UTC](https://www.ruby-forum.com/t/phase-change-for-transmitted-signal-bursts-the-relation-to-clock/246012/2 "2013-08-09T00:50:00Z")

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On 08/08/2013 05:25 PM, Alex Z. wrote:

> 

Indeed, the carrier phase for discontinous transmission will be at some  
random spot every time you start a burst. The hardware doesn’t have any  
notion of “start the burst only when the clock phase is the same as  
it was last-time I sent a burst”. Unless you have utter blind luck,  
your burst timing  
isn’t ever going to be an exact multiple of the clock frequency, so  
there’s no way the carrier phase will be in exactly the same place at  
the start of  
every burst.

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

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**Author:** ![akeem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/54ee81/32.png) [@akeem](https://www.ruby-forum.com/u/akeem)\
**Post date:** [October 23, 2014, 8:02pm UTC](https://www.ruby-forum.com/t/phase-change-for-transmitted-signal-bursts-the-relation-to-clock/246012/3 "2014-10-23T20:02:00Z")

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I just review this mail and want to ask when we try to send the burst  
data,  
can we force the carrier phase to be a specified value at every  
beginning  
of burst? If it can, does this procedure cost time or just take effect  
within the sample time?

On Thu, Aug 8, 2013 at 4:53 PM, Marcus D. Leech [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> > 
> 
> every burst.
> 
> * * *
> 
> Discuss-gnuradio mailing list  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)

–

Alex,