# Spikes in b210 received data

**URL:** <https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683>\
**Category:** GNU Radio\
**Created:** [March 21, 2015, 7:16am UTC](https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683 "2015-03-21T07:16:53Z")\
**Posts on this page:** 4\
**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:** [March 21, 2015, 7:16am UTC](https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683/1 "2015-03-21T07:16:53Z")

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Hi all  
I am trying to capture a cosine at 300KHz sent from a vector signal  
generator(VSG) using USRP B210. VSG is connected to USRP using SMA  
cable.  
signal level at the input of B210 is -30dBm.

For this, I have made a simple flowgraph in GRC which is attached. Clock  
reference is external and is provided from the VSG. Sampling rate is 5M,  
center frequency is 100e6.

On observing the received samples, there is a periodic " ramp " on the  
received sample. Attaching the plot. I do not observe this effect while  
using N210. Also I do not observe this if I use the internal clock.

Thank you

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**Author:** ![Arjun\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ad7895/32.png) [@Arjun\_N](https://www.ruby-forum.com/u/Arjun_N)\
**Post date:** [March 24, 2015, 1:28am UTC](https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683/2 "2015-03-24T01:28:07Z")

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Hi Arjun,

On Fri, Mar 20, 2015 at 11:15 PM, Arjun N. via USRP-users  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> On observing the received samples, there is a periodic " ramp " on the  
> received sample. Attaching the plot. I do not observe this effect while  
> using N210. Also I do not observe this if I use the internal clock.

Can you reduce the level on the VSG by a few dB and see if that  
changes the behavior?

And is the ramp effect consistently tied to the use of the external  
reference? or is the relationship intermittent?

-TT

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**Author:** ![Arjun\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ad7895/32.png) [@Arjun\_N](https://www.ruby-forum.com/u/Arjun_N)\
**Post date:** [March 24, 2015, 6:31am UTC](https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683/3 "2015-03-24T06:31:41Z")

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Hi Tom,  
I have tried reducing the signal level. The signal level at the input is  
now -40dBm. Still there is this ramp behaviour.

I also get this when I use the B210 in loopback mode (with a 30dB  
atttenuator in the loop). Also I have observed that  
the lower the master clock rate that I set, the less frequent the ramps.

Thank you,

Arjun N.

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**Author:** ![Arjun\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ad7895/32.png) [@Arjun\_N](https://www.ruby-forum.com/u/Arjun_N)\
**Post date:** [March 26, 2015, 11:58am UTC](https://www.ruby-forum.com/t/spikes-in-b210-received-data/234683/4 "2015-03-26T11:58:17Z")

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On Tue, Mar 24, 2015 at 11:07 PM, Arjun N. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Thank you, Tom  
> That fixes the problem.

Great. Thanks for testing.

Upcoming UHD and gr-uhd changes will expose more of the AD9361  
functionality, which will allow user control of calibration and  
filters without having to patch UHD. We’re also looking into better  
tuning of the calibration tracking to avoid such signal oddities.

-TT