[USRP-users] Broken gpsdo or bad antenna?

Nick Foster nick at ettus.com
Tue Jun 26 10:52:09 EDT 2012


Hi Dario,

I'm out of ideas regarding your reference. To me, it seems like *something*
is locking, but not to the proper device.

The last possibility I can see before a hardware failure is the possibility
that your local cell tower actually is off 20kHz. Unlikely, but if it's
your only point of reference I suppose it's possible.

Let me know if you want us to issue an RMA to retrieve the USRP + GPSDO for
testing and repair.

--n

On Tue, Jun 26, 2012 at 12:41 AM, Dario Lombardo <
dario.lombardo.ml at gmail.com> wrote:

> John, Nick
> Any other ideas, your side? Do you have debugging/test code to check that
> gpsdo is not broken?
> I've tried everything and the only possibily left is a broken gpsdo.
>
> On Tue, Jun 19, 2012 at 4:53 PM, Nick Foster <nick at ettus.com> wrote:
>
>> Dario,
>>
>> Also, please try configuring the USRP for "external" reference as you did
>> for the cesium test previously. Then connect the GPSDO to the external
>> reference input and see if kal gives reasonable error.
>>
>> It does seem like you may have a faulty reference input.
>>
>> --n
>>
>> On Tue, Jun 19, 2012 at 4:45 AM, John Malsbury <john.malsbury at ettus.com>wrote:
>>
>>> Just for grins, can you remove the eeprom config that enables the
>>> internal gpsdo?  What results do you see from kal when the internal tcxo on
>>> the motherboard is used?
>>>
>>> BTW, are you getting reasonable gga strings that correlate to your known
>>> position?
>>>
>>>
>>> John
>>>
>>> On Tuesday, June 19, 2012, Dario Lombardo <dario.lombardo.ml at gmail.com>
>>> wrote:
>>> > Hi Josh
>>> >
>>> > On Tue, Jun 19, 2012 at 1:14 PM, John Malsbury <
>>> john.malsbury at ettus.com> wrote:
>>> >>
>>> >> Dario,
>>> >>
>>> >> Forgive me if I am not able to see your previous posts as I am
>>> answering from my phone.  Are you saying there is
>>> >> 11 khz of error in the 10 mhz ref, or some frequency set to a
>>> daughterboard LO?
>>> >
>>> > I'm saying that error is the output of kalibrate.
>>> >
>>> >>
>>> >> You mention using an external reference.  I don't think you would
>>> achieve lock if this were the issue, but have you ensured the jumper is in
>>> the proper configuration?
>>> >
>>> > When using the front panel connectors, I moved the jumper J510 to
>>> select them. In this case I got 0 Hz of error at my first try. To be sure,
>>> I disconnected the gpsdo from the mainboard.
>>> >
>>> >>
>>> >> Are you selecting default or external as the ref source in your
>>> software?
>>> >
>>> > When using the gpsdo, I moved the jumper J510, then configured the
>>> eeprom to "internal". In this case I suppose that the N210 automatically
>>> selects the gpsdo. In fact every time I run something I see
>>> > -- Opening a USRP2/N-Series device...
>>> > -- Current recv frame size: 1472 bytes
>>> > -- Current send frame size: 1472 bytes
>>> > -- Found a Jackson Labs GPS
>>> > -- Setting references to the internal GPSDO
>>> > -- Initializing time to the internal GPSDO
>>> > no matter if any "external ref" is used or not. In kal, I got that
>>> error with and without the "-x" switch.
>>> >>
>>> >> John
>>> >>
>>> >> On Tuesday, June 19, 2012, Dario Lombardo <
>>> dario.lombardo.ml at gmail.com> wrote:
>>> >> > Hi all
>>> >> > After many tries with my gpsdo, I still can't get a good clock.
>>> >> > I've written a sw that continuously polls the gps_locked and the
>>> ref_locked sensors. Both of them are always locked, that means that my
>>> antenna is getting a quite "clear" sky view.
>>> >> > I've connected the front panel connectors of my N210 to a cesium
>>> clock/pps generator, and I get 2 to 0 Hz of error with kal. That should
>>> mean that my usrp works fine and the kal commands are good.hu
>>> >> > I've left the usrp turned on, with the gps antenna connected, for
>>> over 20 hours, but kal still gives me around 11 kHz of error.
>>> >> > I think that one of these 2 things is happening:
>>> >> > 1) my gpsdo card is broken. What can I do to ensure that this is
>>> not the case? And if this is the case, what can I do?
>>> >> > 2) my antenna can't give a signal that is clear enough, so the
>>> gpsdo isn't unable to give me the clock.
>>> >> > What do you think about the above cases?
>>> >> > Any help appreciated.
>>> >> > Dario.
>>>
>>> Just for grins, can you remove the eeprom config that enables the
>>> internal gpsdo?  What results do you see from kal when the internal tcxo on
>>> the motherboard is used?
>>>
>>> Are you getting reasonable gga strings that correlate to your known
>>> position?
>>>
>>>
>>> John
>>>
>>> On Tuesday, June 19, 2012, Dario Lombardo <dario.lombardo.ml at gmail.com>
>>> wrote:
>>> > Hi Josh
>>> >
>>> > On Tue, Jun 19, 2012 at 1:14 PM, John Malsbury <
>>> john.malsbury at ettus.com> wrote:
>>> >>
>>> >> Dario,
>>> >>
>>> >> Forgive me if I am not able to see your previous posts as I am
>>> answering from my phone.  Are you saying there is
>>> >> 11 khz of error in the 10 mhz ref, or some frequency set to a
>>> daughterboard LO?
>>> >
>>> > I'm saying that error is the output of kalibrate.
>>> >
>>> >>
>>> >> You mention using an external reference.  I don't think you would
>>> achieve lock if this were the issue, but have you ensured the jumper is in
>>> the proper configuration?
>>> >
>>> > When using the front panel connectors, I moved the jumper J510 to
>>> select them. In this case I got 0 Hz of error at my first try. To be sure,
>>> I disconnected the gpsdo from the mainboard.
>>> >
>>> >>
>>> >> Are you selecting default or external as the ref source in your
>>> software?
>>> >
>>> > When using the gpsdo, I moved the jumper J510, then configured the
>>> eeprom to "internal". In this case I suppose that the N210 automatically
>>> selects the gpsdo. In fact every time I run something I see
>>> > -- Opening a USRP2/N-Series device...
>>> > -- Current recv frame size: 1472 bytes
>>> > -- Current send frame size: 1472 bytes
>>> > -- Found a Jackson Labs GPS
>>> > -- Setting references to the internal GPSDO
>>> > -- Initializing time to the internal GPSDO
>>> > no matter if any "external ref" is used or not. In kal, I got that
>>> error with and without the "-x" switch.
>>> >>
>>> >> John
>>> >>
>>> >> On Tuesday, June 19, 2012, Dario Lombardo <
>>> dario.lombardo.ml at gmail.com> wrote:
>>> >> > Hi all
>>> >> > After many tries with my gpsdo, I still can't get a good clock.
>>> >> > I've written a sw that continuously polls the gps_locked and the
>>> ref_locked sensors. Both of them are always locked, that means that my
>>> antenna is getting a quite "clear" sky view.
>>> >> > I've connected the front panel connectors of my N210 to a cesium
>>> clock/pps generator, and I get 2 to 0 Hz of error with kal. That should
>>> mean that my usrp works fine and the kal commands are good.hu
>>> >> > I've left the usrp turned on, with the gps antenna connected, for
>>> over 20 hours, but kal still gives me around 11 kHz of error.
>>> >> > I think that one of these 2 things is happening:
>>> >> > 1) my gpsdo card is broken. What can I do to ensure that this is
>>> not the case? And if this is the case, what can I do?
>>> >> > 2) my antenna can't give a signal that is clear enough, so the
>>> gpsdo isn't unable to give me the clock.
>>> >> > What do you think about the above cases?
>>> >> > Any help appreciated.
>>> >> > Dario.
>>> >
>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>
>>>
>>
>
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