Coincidentally, I have been testing relative phase difference of two GPS clocks http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301 since Friday. They are completely independent, including separate antennas and positioned a few yards away from each other so ionospheric disturbances would affect both units equally. Devices use Ublox chipset. Average phase difference did not change in four days since Friday but there is phase wander within around 10ns. Here is a video of 4 hours worth of data. One horizontal division is 20ns: http://leobodnar.com/balloons/NTP/twoGPSclocks.mp4 Cheers Leo > From: Lars Walenius <lars.walenius@hotmail.com> > If I look on the NIST database for the last days it seems to be a daily variation of about 8-10ns. Could this be for the same reason as Ole’s variation? Is the daily variations due to not perfect ionosphere correction? Can you get much better than the data in the NIST database for an ordinary timing receiver like the LEA-6T?

		Attila kinali

On Tue, 7 Nov 2017 22:07:43 +0000 Leo Bodnar <leo@leobodnar.com> wrote: > Coincidentally, I have been testing relative phase difference of two GPS clocks http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301 since Friday. > They are completely independent, including separate antennas and positioned a few yards away from each other so ionospheric disturbances would affect both units equally. Devices use Ublox chipset. > > Average phase difference did not change in four days since Friday but there is phase wander within around 10ns. > Here is a video of 4 hours worth of data. One horizontal division is 20ns: > > http://leobodnar.com/balloons/NTP/twoGPSclocks.mp4 Do you have this measurement with proper time-differences? Ie like using a simple and cheap counter? That would be quite a bit more interesting than a video of an osciloscope screen. Attila kinali -- You know, the very powerful and the very stupid have one thing in common. They don't alters their views to fit the facts, they alter the facts to fit the views, which can be uncomfortable if you happen to be one of the facts that needs altering. -- The Doctor