Gary
Only 1" ? (1" center to center or edge to edge spacing?)
My gut reaction is that "coupling" between the two antennas may have
some effect on some of the variation. You may in fact have
unintentionally created a phased array. This phased array could favor
one antenna in an particular Az/El and favor the other in another Az/El.
If not too arduous it would be good to separate the antennas by several
feet, run the data again then swap mountings of the antennas and run yet
another set of data
Dave
[email protected]
On 1/8/2017 4:52 PM, Gary E. Miller wrote:
Yo All!
I just ran 24 scatter plots on 2 GPS with external antennas one inch apart.
pi2-5.png is an Adafruit GPS HAT with an MTK-3301. upuv2.png is an
Uputronics GPS HAT version 2, with a uBlox 8.
See attached. I'm not sure it sheds any light on this discussion...
There does appear to be a bit of correlation between the bigger random
walks in the graphs. And a whole lot of other things going on.
During that time, the Adafruit saw 6 to 12 sats and a constant TDOP of
0.82. The Uputronics reported seeing 4 to 20 sats and a TDOP from 0.42
to 32.6 and a mean of 0.786 and a SD of 0.668.
To bring this back to time-nuttery, when the TDOP hit 32.6 I can see a
2 micro Second spike in NTP jitter. So for that small period in time
my Raspberry Pi clock was more stable than my PPS.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
[email protected] Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Dave
[email protected]
www.ArtekManuals.com
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
