[time-nuts] SE880 GPSDO

Michael Wouters michaeljwouters at gmail.com
Wed Apr 27 04:11:40 EDT 2016


On Wed, Apr 27, 2016 at 7:51 AM, Attila Kinali <attila at kinali.ch> wrote:
>
>
>
> Another way would be to use L1/L2 receivers with calibrated antennas.
> I know that BIPM has a GPS station that can deliver time transfer
> accuracy <2ns over a distance of several 100km. It could be possible
> to use such receivers with the <3km distances to deliver 10 times better,
> if they are frequently calibrated (eg. every couple of days).

> But of course, this makes things much more expensive.
>
> But all this is a wild guess. I haven't seen anything like this done.

There was a discussion in 2005 that's pertinent to this:

https://www.febo.com/pipermail/time-nuts/2005-August/019158.html

The references are interesting, with some real data about what is
achievable on short baselines.
eg Fig 7 in http://gpstime.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf
shows that two receivers keep within about 5 ns of each other on a
21.5 km baseline.

As I think I said in a similar discussion a few weeks ago, two
identical geodetic receivers that I have on a 400 m baseline keep
within about 100 ps of each other, using a Precise Point Positioning
solution for the (common) clock.
If you were brave, then 2 km would scale to 500 ps synchronization
(works for 5 ns/20 km too ..)

Cheers
Michael


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