[time-nuts] SE880 GPSDO

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Apr 26 12:58:53 UTC 2016


Insufficient information to indicate if carrier phase data is externally available.Without this it appears that the position accuracy is around 10x worse than the requirement for 10ns timestamp accuracy.
 
The timing stability is also somewhat unknown.How well will 2 independent modules track in phase?In particular what is the effect of brief loss of GNSS signals?It would probably be necessary to obtain a pair of modules and measure their relative ADEV etc as a function of physical separation.

The phase noise floor is  somewhat higher than a Thunderbolt for example, which in itself is limited by its relatively noisy output amplifier.
Bruce 

    On Wednesday, 27 April 2016 12:08 AM, Ilia Platone <info at iliaplatone.com> wrote:
 

 Thank you Attila,

Just for informations, as I must build the board from scratch, does this 
design is good to implement into the datalogger?
I mean, for the second RTK purpose, does this u-blox module satisfy my 
requirements (link below)?
http://www.opendigitalradio.org/lea-m8f-gpsdo

Regards,
Ilia.

Il 26/04/2016 01:36, Attila Kinali ha scritto:
> On Mon, 25 Apr 2016 23:34:52 +0200
> Ilia Platone <info at iliaplatone.com> wrote:
>
>> I selected this because of the CMOS output, since I didn't find any
>> Connor Winfield osc with these levels yet.
> To get to CMOS levels, you usually add a simple inverter, with an
> capacitor in front and a 1M resistor across the inverter (from input
> to output).
>
>
>> Actually  want to achieve less than around 78ps jitter at 125MHz. (this
>> should be achievable using this also:
>> http://www.digikey.it/product-detail/it/fox-electronics/FVXO-HC53B-125/FVXO-HC53B-125-ND/2153894)
> I think you are mixing up a few things here:
>
> Your logger might have very relaxed jitter requirements, but the
> GPS module needs a low noise reference signal. If you feed it with
> the noisy HC53 output, you will degrade your GPS receivers performance
> severely. At the minimum, you should use a normal XO for the GPS modul.
> You can of corse use a HC53 as the reference for your logger if its
> jitter is ok for you.
>
> And for comparison, for a XO you usually talk about jitter in the
> order of 100fs to 1ps (10kHz-20MHz)
>
>
>
>             Attila Kinali

-- 
Ilia Platone
via Ferrara 54
47841
Cattolica (RN), Italy
Cell +39 349 1075999

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