[time-nuts] TIC resolution impact on GPSDO's performance

bg at lysator.liu.se bg at lysator.liu.se
Thu Dec 28 21:52:30 UTC 2006


On Thu, December 28, 2006 21:59, Jason Rabel said:
>> Bjorn and I have a little project going where we use the CNC Allstar
> receivers.
>> They have the specific feature that their referens XO is at 10 MHz. This
> will
>> make it very easy to drop in a suitable oscillator. As it happends I see
> that a
>> FTS1200 and an Allstar receiver has showed up in my main rack during
>> some
>> unexplainable appearance in the lab yeasterday. It is not as much the
> ability
>> too hook it up as getting the receiver time to EFC solution into place.
> I'm
>> working on that right now, but it will involve a little bit of wizardy.
>> The Allstar receivers have about 1 cm RMS of carrier noise which should
> show up
>> as about 33 ps RMS noise. It should be an interesting proof of concept
> thing.
>
>
> I have some SuperStar II receivers and they also have a 10 MHz TCXO on
> them,
> now Novatel makes them.
>
> http://www.novatel.com/products/superstar.htm
>
> If you search for the phrase "OEM GPS MODULE WITH SMA ANTENNA CABLE" on
> eBay
> you should be able to find them when the person lists more (none currently
> show up). They appear to be OEM models with on a 4mb flash and not the
> newer
> 8mb flash so they can't be upgraded. I have lots of PDFs with info and
> everything. The pinout is more or less the same as the Rockwell Jupiter 8
> boards. There is also an open-source GPS project that uses the chip on
> these, however the project in its current state is less than stellar.
>
> I bought 5 boards (was cheaper because of shipping costs). If you want one
> or two let me know, I'll sell them cheap. I only want to keep a couple for
> myself, definitely don't need 5.
>
> Jason

A Superstar would be just as good base for our little project. I think
Doug Bakers receivers would do too (think at some point some model even
had an coax connector for an external oscillator) but they are ofcause
much more expensive than surplus ebay receivers.

  http://www.gpscreations.com/Products_Receivers.html

Another interesting user of the Zarlink chipset is Meinberg. They have a
menu of oscillators from TCXO, via OCXOs to Rb.

    http://www.meinberg.de/german/specs/gpsopt.htm

Has anyone taken a deeper look into a GPS167? I would be surprised if they
do not let the main oscillator drive the GPS. Their GPS jitter
specification is very conservative. Did anyone measure one to look at
actual performance. On the other hand, if you drive an NTP-server or
similar application, there is really no need for a low ns PPS pulse, it is
very much more interesting to have a say sub 1us PPS, with a great
holdover for events like antenna/cable failures, buying you some days to
get aware of and fix the problem.

John, if you are interested in data on the FTS1000 family for your
oscillator performance page

    http://www.febo.com/time-freq/hardware/specs.html

there is some data in

   ftp://ftp.lysator.liu.se/~bg/time-nuts/FTS1200Doku.pdf

Magnus with all his fancy equipment :-) should be able to do some real
measurements in the coming months on the FTS1200 and some other lesser
oscillators now sitting in his rack.

--

   Björn







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