[time-nuts] OCXO Retrace

Tim Shoppa tshoppa at gmail.com
Wed Feb 10 15:15:46 EST 2016


I think what you are observing, is the detail of how the control loop
transitions from frequency locked to phase locked. And this has more to do
with the divider chain reset and phase detector than anything else.

Note that several of the hobbyist/E-bay GPSDO's (especially the "Chinese
GPSDO") do not have a phase locked mode, at best they are frequency locked,
and many of these have a consistent bias based on the gating of the
frequency counter (typically their counter gating adds an extra count,
meaning that when they are frequency locked to GPS they are running
slightly slow).

Tim N3QE

On Wed, Feb 10, 2016 at 2:17 PM, Bob Stewart <bob at evoria.net> wrote:

> I've been running up a number of OCXOs lately, all Trimble 34310-T.  For
> most of them, the DAC moves in the negative direction after lock.  But
> there are a few where the DAC moves more positive.  Is this an indication
> of a different cut of crystal, or is retrace direction more or less random?
>
> Bob - AE6RV
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