[USRP-users] Broken gpsdo or bad antenna?

Dario Lombardo dario.lombardo.ml at gmail.com
Wed Jun 20 03:26:12 EDT 2012


On 19/giu/2012, at 13:45, John Malsbury <john.malsbury at ettus.com> wrote:

Just for grins, can you remove the eeprom config that enables the internal
gpsdo?


The eeprom is set to internal when using gpsdo from jackson labs, according
to instructions.

 What results do you see from kal when the internal tcxo on the motherboard
is used?


Around 200 hz of offset.

BTW, are you getting reasonable gga strings that correlate to your known
position?

Yes, more or less they are ok. Afaik, I can see 7 to 9 sats.

John

On Tuesday, June 19, 2012, Dario Lombardo < <dario.lombardo.ml at gmail.com>
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>
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>
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  <http://good.hu/>
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>
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>
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>
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  <http://good.hu/>
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.
>
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