[time-nuts] GPSDO and holdover

Chris Albertson albertson.chris at gmail.com
Wed Apr 23 04:39:59 UTC 2014

On Tue, Apr 22, 2014 at 6:57 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> I do not think there is any standard. Just conventions: some documented,
> some not. It's attention to a dozen little details like this that separate
> a quick hack GPSDO from a quality one. You'll also face a number of design
> issues at startup, and coming out of holdover. Lastly, you get to choose
> between it being an ideal time standard vs. an ideal frequency standard.

The simplest thing, I think is to use the GPS' serial data stream to decide
if you are in holdover or not.   There will be a status message that says
if the GPS is producing valid output.  The details depend on the GPS but
most have something to describe the number of GPS satellites in view and
something about each of them.


Chris Albertson
Redondo Beach, California

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