[time-nuts] CW12-TIM vs M12M and the world

[Azelio Boriani]

Yes, it is: the CW12 has the PPS derived from the 100MHz clock and that's
why you have that PPS granularity with no need for a sawtooth correction.

On Thu, Mar 29, 2012 at 7:18 PM, paul swed <paulswedb at gmail.com> wrote:

> OK been only slightly paying attention.
> But I see in the US several sellers for a operational board at $84-89.
> Maybe I have the wrong unit but it does say 5ns or less timing error
> Regards
> Paul
> WB8TSL
>
> On Thu, Mar 29, 2012 at 11:50 AM, Ed Palmer <ed_palmer at sasktel.net> wrote:
>
> > On 3/29/2012 12:54 AM, Ulrich Bangert wrote:
> >
> >> Thomas,
> >>
> >>  The sawtooth error on the Motorola M12+ is about +/- 25ns, while the
> >>> CW12-TIM has a sawtooth error of +/- 2 ns, so correcting for the
> >>> sawtooth error is not as critical with the CW12-TIM.
> >>>
> >> The first claim
> >>
> >>  The sawtooth error on the Motorola M12+ is about +/- 25ns
> >>>
> >> is correct but are you absolutely sure that the second claim is correct
> >> too?????
> >>
> >> It would mean a factor>10 improvement of the CW12-TIM against the M12
> >> which
> >> is hardly believeable.
> >>
> >
> > Believe it.  I've made multiple test runs where I use an HP 5372A to
> > measure 1000 pulses of the CW12.  The Standard Deviation is always < 5 ns
> > with a max-min range of < 30 ns.  That's without any type of error
> > correction - straight from the GPS receiver to the 5372A.  A clue to the
> > performance is a line in the datasheet that says the clock speed is "up
> to
> > 120 MHz".  Maybe not fast enough to justify +/- 2 ns., but in the ball
> park.
> >
> > I am rather surprised that they're adding sawtooth correction.  This unit
> > has been around for some years.  The Motorola firmware isn't even a
> > standard offering anymore.  You have to ask for it.  It'll be interesting
> > to see what they come up with considering that the datasheet says that
> the
> > resolution on the 1 PPS signal is "< 5 ns".  There doesn't seem to be
> much
> > room for correction there.
> >
> > Ed
> >
> >
> >  Best regards
> >> Ulrich Bangert
> >>
> >>  -----Ursprungliche Nachricht-----
> >>> Von: time-nuts-bounces at febo.com
> >>> [mailto:time-nuts-bounces@**febo.com <time-nuts-bounces at febo.com>] Im
> >>> Auftrag von Tom Knox
> >>> Gesendet: Mittwoch, 28. Marz 2012 20:42
> >>> An: Time-Nuts
> >>> Betreff: [time-nuts] CW12-TIM vs M12M and the world
> >>>
> >>>
> >>>
> >>> I spoke with Navsync about some of the issues we are
> >>> discussing and this was their response. I just received mine
> >>> and will try to test it over the weekend. 1. Is CW12-TIM
> >>> compatible with Motorola M12 ?>>   The CW12 is designed to be
> >>> compatible with the M12 although there are
> >>> some differences.  The main hardware differences are listed
> >>> on page 7 of  the CW12 User Manual
> >>> (http://www.navsync.com/docs/**cw12-tim_um.pdf<
> http://www.navsync.com/docs/cw12-tim_um.pdf>).
> >>>  2.  According
> >>> to the customer, M12 has a Sawtooth Correction Error&
> >>> Hanging Bridge Error? Does CW12 have a solution for these type of
> >>> errors? How these errors are taken care of in CW12?>>
> >>>  The Hanging Bridge Error is a pattern seen in the sawtooth
> >>> error that
> >>> occurs as the local clock frequency changes.  The standard Motorola
> >>> Binary software for the CW12-TIM does not have the sawtooth
> >>> correction
> >>> field in the @@Hn command implemented, but NavSync is currently
> >>> developing this and it will be available in future standard releases.
> >>>  The sawtooth error on the Motorola M12+ is about +/- 25ns, while the
> >>> CW12-TIM has a sawtooth error of +/- 2 ns, so correcting for the
> >>> sawtooth error is not as critical with the CW12-TIM.
> >>>
> >>> Thomas Knox
> >>>
> >>>
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