[USRP-users] WBX V3 step size
Marcus D. Leech
mleech at ripnet.com
Mon Sep 1 12:03:45 EDT 2014
On 09/01/2014 11:31 AM, bob wole via USRP-users wrote:
> A few questions related two Ettus hardware:
> 1) I want to know that what is the frequency step size of the WBX V3
> LO ?
My recollection is that it's on the order of a few hundred Hz, but look
at the driver source code to get a definitive answer.
> 2) if I install GPSDOs on two USRPN210 with WBX then would there be
> any frequency offset between two USRPs ?
Yes, there will be *some*. GPSDOs operate by locking a local
high-quality oscillator to the GPS signals, but they'll never perfectly
phase and frequency. I'd expect the disagreement to be on the order
of a few ppb.
> 3) What would be the GPS timing mismatch of the USRPs with GPSDOs
If you're referring to time-of-day, most GPSDOs produce a 1PPS pulse
that is +/- perhaps 10ns, and sometimes worse.
> 4) What happens if I disconnect the GPSDO antennas from the devices
> after correct GPS time latches, would the time of USRPs starts
> drifting away? if yes how fastly ?
A GPSDO builds up a drift estimator, and will continue to use that
estimator when the GPS sky signal goes away. Those estimates will get
worse over time, and definitely if the unit is moved to a different
temperature environment. How long will this take? Hard to say--if the
thermal environment is stable,
likely several hours before there's significant skew between any two
GPSDO that have had their antennae removed.
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> USRP-users at lists.ettus.com
Shirleys Bay Radio Astronomy Consortium
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