[USRP-users] Broken gpsdo or bad antenna?

Dario Lombardo dario.lombardo.ml at gmail.com
Tue Jun 19 07:26:31 EDT 2012

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.
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