Re: [chrony-users] Time synchronisation over a high-latency packet radio network

[Bill Unruh <unruh@xxxxxxxxxxxxxx>]

If the detector simply needs to be in the field for a few days, you can always
set the rtc just before you put it into the field. It might, or might not hold
reasonable accuracy for a couple of days (they can be out by many PPM
especially if the temperater fluctuates) Let say 20PPM which is a couple of  seconds per
day more or less. You might be lucky and get a better rtc, but it is dubious.

You can set up chrony so that when it comes up it does a jump to the received
time (wherever it finds its server) Especailly if you r accuracy is a a second
that should bring it easily into range.

So, you could plug them in at home get chrony to get them into time sync, and
then put them outthere for a day or so.



William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/

On Wed, 8 May 2019, Stuart Longland wrote:

> On 8/5/19 10:35 am, Bill Unruh wrote:
> > > Doable, and I've made future provision for it, but as stated, I'm trying
> > > to keep costs down.  If more hardware is the answer, my first stop will
> > > be for a battery-powered RTC rather than a GPS.
> >
> > really cheap rtc will have trouble keeping 1 sec accuracy for any length of
> > time, especially if your device is subject to temperature variations (
> > which
> > it would seem yours will).
>
> Probably, the real advantage with having an RTC is that while it might
> drift by a few minutes whilst in storage… it's much better than the
> "stock RTC" in the PocketBeagle, which at present is about 3 years out.
>
> These will be brought out of storage, programmed with a call-sign and a
> location, used over 3 or 4 days, then put away again for a few months
> until the next such event comes along.
>
> This weekend just gone was the first time we used this system, the next
> time where we'll likely use it will be in July.  It really just needs to
> be able to hold the time for a day whilst un-powered so that `chronyd`
> has a small offset to adjust, not a huge one.
>
> Regards,
> --
> Stuart Longland (aka Redhatter, VK4MSL)
>
> I haven't lost my mind...
>  ...it's backed up on a tape somewhere.
>
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