[time-nuts] LEA-6T TCXO measurements

Gabs Ricalde gsricalde at gmail.com
Fri May 4 05:18:55 EDT 2018


On Thu, Apr 26, 2018 at 8:36 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> 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.
>

Hi Bob,

The raw data has a sawtooth pattern due to millisecond clock jumps
[1], but TimeLab unwraps it and they happen more frequently than the
frequency jumps.
I redid the the experiment using the same receiver (pink trace) and
another LEA-6T (green trace), there were no frequency jumps. SBAS was
enabled in the old measurements (blue trace). I'm not sure if that
explains it, but the manual does not recommend SBAS for timing.


[1] "GNSS Receiver Clocks" http://www.insidegnss.com/node/2512
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