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.4.22.17.7z
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.
Cheers,
Magnus
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