[USRP-users] N200 stability
Marcus D. Leech
mleech at ripnet.com
Wed Apr 22 12:16:23 EDT 2015
On 04/17/2015 09:08 AM, Dan Sego via USRP-users wrote:
> Good morning the list.
> I have 2 N200s w/ WBX connected via MIMO cable with an internal GPSDO
> on the master. I have attached calculated intra-channel and
> inter-channel phase stability calculations on from a tone generator.
> The results over approximately 100 seconds demonstrate about 0.15
> radians of drift with a fair amount of low frequency noise. The low
> frequency noise (1 Hz-ish) is common to both channels.
> Are these results consistent with expectations? I have also attached
> the two channel code as I'm still not completely sure that I have
> configured the clock correctly (and by coincidence just
> seeing hanwen's posted query, in particular the option of GPSDO or? MIMO).
> Any and all advice is appreciated. Thanks
> Dan Sego
> USRP-users mailing list
> USRP-users at lists.ettus.com
I don't see anywhere in your code where you're setting the master-side
clock source to "gpsdo" or "external" -- also on the N210, those two are
conceptually the same, with a hardware jumper selecting whether the
"external" clock comes from the front-panel or the on-board GPSDO.
There's a jumper block on the mainboard, J510, which selects between the
front-panel 10MHz in, or the 10MHz provided by the on-board GPSDO--make
sure that's in the correct position, selecting connector J507 instead
How are you connecting the signal generator to the two N210s? Is it
conceivable that mutual phase-drift is a temperature effect of the way the
signals are being distributed?
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