[time-nuts] Survey plot as art.

Artek Manuals Manuals at ArtekManuals.com
Sun Jan 8 17:18:06 EST 2017


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


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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.
> ---------------------------------------------------------------------------
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
> 	gem at rellim.com  Tel:+1 541 382 8588
> 	    Veritas liberabit vos. -- Quid est veritas?
>      "If you can’t measure it, you can’t improve it." - Lord Kelvin
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