[time-nuts] GPS week rollover

[John C. Westmoreland, P.E.]

To All:

I have a related question; hope it's OK:

What are these companies using for their "GPS Simulation/Simulators?".

Is it actually simulating the RF downlink or is a direct data stream
injection into a tap into the receiver??

Thanks In Advance,
John W.


On Fri, Mar 29, 2019 at 11:00 AM Michael Shields via time-nuts <
time-nuts at lists.febo.com> wrote:

> Avidyne avionics are known to be affected by the rollover, causing the
> loss of some displayed data.
>
> https://www.avidyne.com/files/downloads/606-00182-019.pdf
>
>
> On Thu, Mar 28, 2019 at 3:04 PM Mark Sims <holrum at hotmail.com> wrote:
> >
> > I doubt that any GPS receivers will be newly affected on April 6.   Some
> very early receivers were hit on the first GPS rollover, but those made
> since then usually have a 1024 week compensation built in based upon the
> firmware creation date.  Those rollover 1024 weeks from that date and start
> sending incorrect dates at other places in the 1024 week cycle.  Some
> receivers even let you force the rollover week.
> >
> > > I have a Z3816A that’s showing a yellow “ro” next to the date in LH
> and is 18 seconds ahead of a Motorola 12 channel
> >
> > If Lady Heather sees a date earlier than a set year (currently 2017), it
> assumes the GPS device has rollover issues and adds 1024 weeks to correct
> the date and shows the "ro" flag.
> >
> > As far as the 18 second time difference, one of the devices is
> configured to show GPS time and the other is set for UTC time.  At the top
> right corner of the screen it should say either "UTC time OK" or "GPS time
> OK" (as long as the device has a valid time).  The TG and TU commands can
> switch between GPS and UTC time displays.  Some receivers have firmware
> commands to switch between the two.  For the others, Heather does the
> conversion in software using the "UTC offset" (i.e. leapsecond count)
> value.  Many receivers send this offset.   If it does not, the user can set
> the value.  And if no value is available Heather makes a best guess as to
> what the value might be (and shows it in RED).  The guessed value is rather
> prone to errors, but is better than nothing.
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