[USRP-users] Random long duration noise at the start of UBX captures

Michael West michael.west at ettus.com
Tue Oct 13 12:17:50 EDT 2015


Hi Nathan,

Do you see the effect at lower sample rates?  Can you send me the data file
and/or screen capture of the effect you are seeing?

Regards,
Michael

On Tue, Oct 13, 2015 at 8:04 AM, Perelman, Nathan <
nperelman at lgsinnovations.com> wrote:

> Not that I can see. I pasted the full output from the command below. I
> tried with UHD 3.9.1 and still see the same results.
>
>
>
> $ /usr/lib64/uhd/examples/rx_samples_to_file --duration 2 --rate 25000000
> --freq 1e9 --gain 38 --ref internal --setup 0
>
> linux; GNU C++ version 4.4.7 20120313 (Red Hat 4.4.7-16); Boost_105500;
> UHD_003.008.005-0-unknown
>
>
>
>
>
> Creating the usrp device with: ...
>
> -- Opening a USRP2/N-Series device...
>
> -- Current recv frame size: 1472 bytes
>
> -- Current send frame size: 1472 bytes
>
> Using Device: Single USRP:
>
>   Device: USRP2 / N-Series Device
>
>   Mboard 0: N210r4
>
>   RX Channel: 0
>
>     RX DSP: 0
>
>     RX Dboard: A
>
>     RX Subdev: UBX RX
>
>   TX Channel: 0
>
>     TX DSP: 0
>
>     TX Dboard: A
>
>     TX Subdev: UBX TX
>
>
>
> Setting RX Rate: 25.000000 Msps...
>
> Actual RX Rate: 25.000000 Msps...
>
>
>
> Setting RX Freq: 1000.000000 MHz...
>
> -- Successfully tuned to 1000.000000 MHz
>
> --
>
> Actual RX Freq: 1000.000000 MHz...
>
>
>
> Setting RX Gain: 38.000000 dB...
>
> Actual RX Gain: 38.000000 dB...
>
>
>
> Waiting for "lo_locked": + locked.
>
>
>
> Press Ctrl + C to stop streaming...
>
>
>
> Done!
>
>
>
> *From:* Michael West [mailto:michael.west at ettus.com]
> *Sent:* Monday, October 12, 2015 7:07 PM
>
> *To:* Perelman, Nathan
> *Cc:* Ben Hilburn via USRP-users
> *Subject:* Re: [USRP-users] Random long duration noise at the start of
> UBX captures
>
>
>
> Hi Nathan,
>
> I am unable to reproduce what you are seeing.  I have an N210+GPSDO+UBX
> with a 3A power supply and I ran the rx_samples_to_file command you
> provided with RX2 terminated and all my data looks clean over multiple
> runs.  Are you getting any O's, errors, or warnings during your runs?
>
> Regards,
>
> Michael
>
>
>
> On Mon, Oct 12, 2015 at 2:19 PM, Perelman, Nathan <
> nperelman at lgsinnovations.com> wrote:
>
> Sorry, forgot to mention that, RX2 is terminated. I am also using a 3 amp
> power supply not the recommended 4 amp as I don’t have a 4 amp one.
>
>
>
> I tried setting the reference to internal without disconnecting the GPSDO
> and then again after disconnecting the GPSDO, and saw the same issue. In
> the second case, the noise lasted 1.6 seconds, although I don’t suspect the
> duration has anything to do with the test setup, it seems random.
>
> -Nathan
>
>
>
> *From:* Michael West [mailto:michael.west at ettus.com]
> *Sent:* Monday, October 12, 2015 4:51 PM
> *To:* Perelman, Nathan
> *Cc:* Ben Hilburn via USRP-users
> *Subject:* Re: [USRP-users] Random long duration noise at the start of
> UBX captures
>
>
>
> To be clear, when I say disconnect the GPSDO, I mean disconnect the GPSDO
> power.  The data cables can be left in place.
>
> Regards,
>
> Michael
>
>
>
> On Mon, Oct 12, 2015 at 1:43 PM, Michael West <michael.west at ettus.com>
> wrote:
>
> Hi Nathan,
>
> The simple answer is no, that is not expected.  What do you have connected
> to the RX2 port?  Also, do you see the same effect if you disconnect the
> GPSDO?
>
>
>
> Regards,
>
> Michael
>
>
>
> On Mon, Oct 12, 2015 at 1:26 PM, Perelman, Nathan via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
> I’ve been having issues with UBX daughter-boards for a little while, and I
> finally traced them down to a reproducible issue. Running:
>
> ./rx_samples_to_file --duration 2 --rate 25000000 --freq 1e9 --gain 38
> --ref gpsdo --setup 0
>
>
>
> I frequently see large amounts of random noise (up to +/- 0.5 out of 1.0),
> for up to 0.5 seconds. I have tested with 2 different UBX daughter-boards
> and seen similar noise. Is this expected with the UBX? I do not see similar
> noise with the SBX.
>
>
>
> I am using UHD 3.8.5 with an N210.
>
> -Nathan
>
>
>
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