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Today's Topics:
1. Re: Transmitting a burst with one call to tx_streamer->send
(Sivan Toledo)
2. Re: Help Needed To Identify Signal (Mark McCarron)
3. Phase difference with synchronized boards (Zohair M. Abu Shaban)
4. Re: Phase difference with synchronized boards (Marcus D. Leech)
5. Re: Phase difference with synchronized boards
(Zohair M. Abu Shaban)
----------------------------------------------------------------------
Message: 1
Date: Thu, 9 May 2013 20:04:01 +0300
From: Sivan Toledo <[email protected]>
To: Mike Jameson <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Transmitting a burst with one call to
tx_streamer->send
Message-ID:
<caol_rufge+uq1jwq+bd4fcsban1l3zmoqetksgn3+ffbvfu...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Thanks a lot Mike. I'll try to shift the LO. Sivan
On Thu, May 9, 2013 at 4:48 PM, Mike Jameson <[email protected]> wrote:
> Hi Sivan,
>
> This sounds like local oscillator leakage. Use the following line in your
> GRC UHD Sink for center frequency:
>
> uhd.tune_request(uhd_center_freq,
> rf_freq=(uhd_center_freq+uhd_lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL)
>
> The 'uhd_center_freq' and 'uhd_lo_offset' need to be specified. Set
> 'uhd_lo_offset' to be something like (samp_rate/2).
>
> Mike
>
> --
> Mike Jameson M0MIK BSc MIET
> Email: [email protected]
> Web: http://scanoo.com
>
>
> On 9 May 2013 13:22, Sivan Toledo <[email protected]> wrote:
>
>> Hi,
>>
>> I am sending a packet with one call to uhd::tx_streamer, with an argument
>> that is a long packet (about 68k samples).
>>
>> In the metadata argument I turn on both start_of_burst and end_of_burst.
>> However, the transmitter seems to stay on.
>>
>> Is it okay to send a single packet this way, without fragmenting it in my
>> code? If so, why is the transmitter (an RFX400 in a USRP1) staying on?
>>
>> Thanks, Sivan
>>
>> _______________________________________________
>> USRP-users mailing list
>> [email protected]
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
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Message: 2
Date: Fri, 10 May 2013 03:09:13 +0100
From: Mark McCarron <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Help Needed To Identify Signal
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Well, another development in this unidentified signal saga. Started getting
this crazy signal in the last few hours on 480.027745 MHz. See here:
http://i.imgur.com/wfeDkq6.jpg
This is the time domain DC coupled:
http://i.imgur.com/tuL1VkK.jpg
This is the time domain AC coupled:
http://i.imgur.com/K2QJF5l.jpg
Still no idea of the source yet. The upshot is that I now know that this
signal is in the environment and to be coming in that strong and stable, it
needs to a professional setup. So, I think this will be the last post on this
topic to this group as it is now known not to be an issue with the USRP itself.
Regards,
Mark McCarron
From: [email protected]
To: [email protected]
Date: Thu, 9 May 2013 04:42:44 +0100
Subject: Re: [USRP-users] Help Needed To Identify Signal
Almost forgot, this is the GNURadio diagram that I was using. You will need to
replace the USRP Source with a file source and throttle.
http://i.imgur.com/ejXMMNv.jpg
The baseband file was recordedas a 16 bit PCM in SDR sharp, I haven't tried
importing it into GNURadio.
Regards,
Mark McCarron
From: [email protected]
To: [email protected]
Date: Thu, 9 May 2013 04:28:27 +0100
Subject: Re: [USRP-users] Help Needed To Identify Signal
haha....I've been withholding information. :)
Giant squids are used as reference models because the neurons are so large.
The action potential is the same in humans.
http://humanbiologylab.pbworks.com/w/page/45302491/Resting%20Cellular%20Membrane%20Potential
But if that were an action potential train, then it would be auditory due to
the duration:
http://www2.le.ac.uk/departments/cpp/staff/professor-ian-forsythe-1/the-brainstem-auditory-pathway
10-100 microseconds is the average and that matches the RF signal.
Here, I have recorded the baseband and uploaded it.
http://depositfiles.com/files/br6068vx4
Regards,
Mark McCarron
Date: Wed, 8 May 2013 22:36:29 -0400
From: [email protected]
To: [email protected]
Subject: Re: [USRP-users] Help Needed To Identify Signal
True, that's why I find it weird, but you can't
ignore the 1ms pulses in the time domain:
http://i.imgur.com/Ydi4pvB.jpg
I found this trace of the signal funny because those pulses look
identical to action potentials:
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/actpot.html
Regards,
Mark McCarron
Ah, you didn't tell us you were living inside a giant squid....
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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Message: 3
Date: Fri, 10 May 2013 08:24:11 +0000
From: "Zohair M. Abu Shaban" <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] Phase difference with synchronized boards
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Dear All,
My setup has three USRP N200 boards with DBSRX2 synchronized a GPS receiver
REF/PPS, split and fed to the boards. The boards are connected directly to a PC
using three 1Gb Ethernet ports belonging to three different subnets.
Using the UHD, I wrote a c++ code (MSVC/Windows) setting all the paramters to
the USRPs and syncing them, reading time-aligned samples from the boards and
storing them in three separate files. To test the sync, I splid a sinusiodal
signal (-20dBm) and fed it to the RF boards input. Then, I execute the UHD
command: usrp->get_time_synchronized () and it returns true. I expected to see
three sinusoids at the top of each other but when I import the samples into
MATLAB and plot them there is a phase shift that is different from a run to
another. To investigate more, I used usrp->get_time_now(x) (where x=0,1,2) and
the time is quite the same:
Time at board0 is: 0.433092
Time at board1 is: 0.433467
Time at board2 is: 0.433874
which means the PPS and REF sync signals are really latched.
A colleague raised an argument that even though the boards' clock are synch the
daughter boards may introduce phase shift. Is this argument
valid here?
Do you have any insights?
Thanks,
Zohair
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Message: 4
Date: Fri, 10 May 2013 09:10:52 -0400
From: "Marcus D. Leech" <[email protected]>
To: [email protected]
Subject: Re: [USRP-users] Phase difference with synchronized boards
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
> Dear All,
>
> My setup has three USRP N200 boards with DBSRX2 synchronized a GPS
> receiver REF/PPS, split and fed to the boards. The boards are
> connected directly to a PC using three 1Gb Ethernet ports belonging to
> three different subnets.
>
> Using the UHD, I wrote a c++ code (MSVC/Windows) setting all the
> paramters to the USRPs and syncing them, reading time-aligned samples
> from the boards and storing them in three separate files. To test the
> sync, I splid a sinusiodal signal (-20dBm) and fed it to the RF boards
> input. Then, I execute the UHD command: usrp->get_time_synchronized ()
> and it returns true. I expected to see three sinusoids at the top of
> each other but when I import the samples into MATLAB and plot them
> there is a phase shift that is different from a run to another. To
> investigate more, I used usrp->get_time_now(x) (where x=0,1,2) and
> the time is quite the same:
> Time at board0 is: 0.433092
> Time at board1 is: 0.433467
> Time at board2 is: 0.433874
>
> which means the PPS and REF sync signals are really latched.
>
>
> A colleague raised an argument that even though the boards' clock are
> synch the daughter boards may introduce phase shift. Is this argument
> valid here?
>
>
> Do you have any insights?
>
> Thanks,
> Zohair
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
The phase will be coherent, but with an unknown phase offset between all
the "players".
This is due to the way PLL synthesizers work using fractional-N
synthesis. There will always be some random phase offset between the
synthesizers
involved. If they all have a common reference, they'll all "march
together", but will have an offset. You'll need to calibrate that out
every time
you start a "run" or retune your boards.
The SBX board has a special feature that allows you to use "timed
commands" to get all the synthesizers to be phase-aligned when tuned
together
at the same time. The DBSRX synthesizer doesn't have the necessary
hardware support for that.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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Message: 5
Date: Fri, 10 May 2013 13:53:31 +0000
From: "Zohair M. Abu Shaban" <[email protected]>
To: "Marcus D. Leech" <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Phase difference with synchronized boards
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
OK... now I understand it.
Thanks a lot,
Zohair
Date: Fri, 10 May 2013 09:10:52 -0400
From: [email protected]
To: [email protected]
Subject: Re: [USRP-users] Phase difference with synchronized boards
Dear All,
My setup has three USRP N200 boards with DBSRX2 synchronized a
GPS receiver REF/PPS, split and fed to the boards. The boards
are connected directly to a PC using three 1Gb Ethernet ports
belonging to three different subnets.
Using the UHD, I wrote a c++ code (MSVC/Windows) setting all the
paramters to the USRPs and syncing them, reading time-aligned
samples from the boards and storing them in three separate
files. To test the sync, I splid a sinusiodal signal (-20dBm)
and fed it to the RF boards input. Then, I execute the UHD
command: usrp->get_time_synchronized () and it returns true.
I expected to see three sinusoids at the top of each other but
when I import the samples into MATLAB and plot them there is a
phase shift that is different from a run to another. To
investigate more, I used usrp->get_time_now(x) (where
x=0,1,2) and the time is quite the same:
Time at board0 is: 0.433092
Time at board1 is: 0.433467
Time at board2 is: 0.433874
which means the PPS and REF sync signals are really latched.
A colleague raised an argument that even though the boards'
clock are synch the daughter boards may introduce phase shift.
Is this argument valid here?
Do you have any insights?
Thanks,
Zohair
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
The phase will be coherent, but with an unknown phase offset between
all the "players".
This is due to the way PLL synthesizers work using fractional-N
synthesis. There will always be some random phase offset between
the synthesizers
involved. If they all have a common reference, they'll all
"march together", but will have an offset. You'll need to
calibrate that out every time
you start a "run" or retune your boards.
The SBX board has a special feature that allows you to use "timed
commands" to get all the synthesizers to be phase-aligned when tuned
together
at the same time. The DBSRX synthesizer doesn't have the
necessary hardware support for that.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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