[time-nuts] Weird GPSDO behavior

Skip Withrow skip.withrow at gmail.com
Thu Sep 28 16:18:28 EDT 2017

Hello Time-Nuts,

I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
with the OCXO removed and a SRS PRS-10 rubidium oscillator in its
place.  I have been running Lady Heather 5.0 and have changed the
damping, gain, and time constant to give me a 20,000 second time
constant with a damping of .6.  I have attached a Lady Heather screen
shot of the weird behavior.  You can see that my GPS antenna is in a
very none ideal location (window on the west side of the building).

Once per day (about 8am) something disturbs the system.  So, the GPSDO
spends much of its time recovering and never gives me anywhere near
the performance that this system is capable of.  I would think that it
is not the PRS-10 as it has no knowledge of time.  I would also think
that it is not the GPS system or receiver, since the GPS constellation
repeats twice per day.

Kind of the two things that I am left with are a glitch by the power
company every morning (there is some large industrial machinery across
the street (but then I would kind of expect glitches at 8am and 5pm),
and perhaps Lady Heather doing something funny.  This system has been
running for quite some time, I have not tried restarting Lady Heather

Anybody seen anything like this, or have any good ideas?

Thanks in advance,
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