[time-nuts] Navsync CW12 - More Info

Azelio Boriani azelio.boriani at screen.it
Thu Jan 5 20:39:52 UTC 2012


OK, thank you.

On Thu, Jan 5, 2012 at 8:29 PM, Ed Palmer <ed_palmer at sasktel.net> wrote:

> Do you mean the reference oscillator for the 5372A?  That was the internal
> 10811 OCXO.  Over a 1000 sec. run, drift wouldn't have any affect on these
> numbers.
>
> Ed
>
>
> On 1/5/2012 12:54 PM, Azelio Boriani wrote:
>
>> Great, don't forget to specify what reference your measurements were made
>> from (or did I miss anything from your posts?).
>> We use the CW12 PPS for our GPSDOs.
>>
>> On Thu, Jan 5, 2012 at 6:57 PM, Ed Palmer<ed_palmer at sasktel.net>  wrote:
>>
>>  Okay, I've cooled off - a bit.  The bottom line is that the 10 MHz output
>>> of the CW12 isn't appropriate for what I wanted to do.  Ah, the joys of
>>> reading and understanding a spec sheet!
>>>
>>> But let's not throw out the baby with the bathwater.  Although the 10 MHz
>>> output has it's issues for typical Time-Nut applications, the 1 PPS
>>> output
>>> is great.  Here are some measurements that I've made over the past few
>>> years on a few GPS receivers and a couple of GPSDOs.  I measure 1000
>>> periods of the 1 PPS and look at the results.  Every run gives somewhat
>>> different results so I've shown some typical ranges.  These measurements
>>> were made with an HP 5372A.  YMMV.
>>>
>>> Device .............. Std Dev (ns).... Range (max-min)(ns) ... Device
>>> Type
>>>
>>> Navsync CW12 ........ 4 - 5 .......... 20 - 25 ............... GPS Rcvr
>>> Motorola UT+ ........ 40 - 55 ........ 95 - 110 .............. GPS Rcvr *
>>> see below
>>> Rockwell Jupiter .... 10 ............  50 ...................  GPS Rcvr
>>> **
>>> Motorola M12M ....... 10 - 15 ........ 40 - 60 ............... GPS Rcvr
>>>
>>> Trimble Thunderbolt . 0.4 - 0.5 ...... 2 - 4 ................. GPSDO
>>> HP Z3801A ........... 0.3 ............ 2 ..................... GPSDO
>>>  ***
>>>
>>>
>>> *   Most of my UT+ 'range' results were in this group, but there were a
>>> few at 20 - 30.
>>> **  Only one result.
>>> *** Only one result.  I need to do more testing on the Z3801A
>>>
>>>
>>> As you can see, the Navsync CW12 is by far the best of the GPS Receivers,
>>> but nowhere near as good as the GPSDOs.  However, imagine using the CW12
>>> to
>>> discipline a good OCXO to build your own GPSDO.  Or using it to
>>> discipline
>>> a PRS10 Rubidium or X72 Rubidium oscillator.  You can't do it with the 10
>>> MHz output, but the 1 PPS output is another story.
>>>
>>> Ed
>>>
>>>
>>>
>>>
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