[time-nuts] Some GPS signal strength data

[John Ackermann N8UR]

Slightly related to the recent threads on GPSDO, I have been plotting a
bunch of statistics from an M12+ for about 10 months

Every five minutes I grab the the number of SVs visible, tracked, signal
strength of each bird, and average signal strength of the tracked birds.
 I have plots of the full run and the most recent 36 hours at
http://www.febo.com/time-freq/plots/oncore.html.  From those plots, it's
pretty apparent that there's plenty of signal strength all the time.

I ran some simple tests on the log data and the lowest number of SVs
tracked over that time was 5.  The lowest signal strength (average of
the raw numbers for each tracked bird reported by the M12+) was 31.43,
and there were only three strength readings below 40.  One thing I
haven't tracked is the number of times the receiver lost lock; I should
figure out how to add that to the data.  However, given the minimum
number of birds tracked, I doubt the receiver came unlocked very often.

I have a pretty decent antenna setup -- a roof-mounted Motorola 2000
antenna fed with about 60 feet of LMR-400 into an HP 2 way splitter,
then another 12 feet of LMR-400 to an HP 4 way splitter, then 6 feet of
LMR-240 to the receiver.  There are some trees in the way, but overall
there's a decent horizon.

I know a lot of cell sites don't have the luxury of a clear sky view,
but given these results from a decent antenna, I wonder if holdover
performance continues to be a significant factor in GPSDO design?

John