[time-nuts] Three-cornered hat on timelab?

Magnus Danielson magnus at rubidium.se
Sat Apr 29 07:45:02 EDT 2017

Hi Bob,

On 04/27/2017 06:48 PM, Bob Stewart wrote:
> Hi Magnus,
> Try as I might, the weather and the local power company had other ideas
> about my long term capture.  I'm running everything but the 5370 from a
> UPS.  I guess I'm going to have to get batteries for my other UPS and
> run the 5370 from that.  A one second power loss was all it took to stop
> the test.

Annoying, but you got some good values never the less.

> Anyway, I did manage to get 376,238 points of data.  The data is
> captured on a 5370A.  The external clock input and the STOP channel are
> fed by the 10MHz from my PRS-45A.  The START channel is fed by the 10MHz
> from one of my GPSDOs.  The EXT channel is fed by the 1PPS from another
> of my GPSDO units.  "EXT ARM" is enabled.  So, essentially, at every
> 1PPS pulse, the phase difference between the two 10MHz feeds is captured.

OK, this seems like a good setup.

> I've attached a screenshot of the phase plot which can also be found here:
> http://evoria.net/AE6RV/Timelab/Screenshot.png
> I've also made the timelab file (compressed by 7z) available here:
> http://evoria.net/AE6RV/Timelab/GFSvsCS.

Thank you for providing the data, I downloaded it so I can play around 
with it, which I naturally did. :)

> So, back to my question:  Where are the large ionospheric phase moves?
> This question has been causing me doubt since I started on this
> project.  Or don't I still have enough data collected for this to happen?

Your data seems to be more affected by constellation shifts, as the 
period of about 43080 s seems to be a period of the constellation.
You either have averaged out to a somewhat incorrect position of your 
antenna or you have sub-optimal position of your antenna.

It gives you a peak-to-peak amplitude of about 10 ns or so.

The ionospheric errors has a period of 86400s, so to get a clear 
separation of these would take more data. However, playing around with 
the data in TimeLab allowed me to filter out some of the other systematics.

The day-to-day variations is noticeable. I wonder how much of that is 
thermal though. The building variations was filtered out in the process.

One has to identify a number of these potential disturbances, estimate 
their size in order to more clearly see other things. TimeLab has a 
notch filter to notch out a particular frequency. It would be nice if an 
alternative approach would be to give the notch a period.

One has to recall that even and odd harmonics to a disturbance frequency 
can be there, as it is not always a pure sine disturbance.


More information about the time-nuts mailing list