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

paul swed paulswedb at gmail.com
Thu Mar 29 17:18:21 UTC 2012


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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