[time-nuts] LEA-6T TCXO measurements

Bob kb8tq kb8tq at n1k.org
Thu Apr 26 08:36:42 EDT 2018


Hi

What you are looking at appear to be sawtooth jumps. Simply put, the module is 
looking at the closest edge on the TCXO to do it’s timing. When the device drifts, 
it can “slip” to another cycle. If you watch the PPS out, there are also artifacts that
result from this process operating in a non-ideal fashion. Lots of details on that in
the archives.

Bob

> On Apr 25, 2018, at 8:56 PM, Gabs Ricalde <gsricalde at gmail.com> wrote:
> 
> The NAV-TIMEUTC message of the u-blox LEA-6T has a fractional seconds
> field, which is the receiver clock offset estimate and can be used to
> measure the internal TCXO. Attached are the ADEV and frequency
> difference plots (blue traces). For comparison, I also have PPS logs
> from a TL-WR703N NTP server (pink traces) with ntpd stopped.
> 
> I'm wondering why the LEA-6T has that kind of frequency jumps.
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