[time-nuts] Weird GPSDO behavior

Didier Juges shalimr9 at gmail.com
Fri Sep 29 09:53:39 EDT 2017

Where I work, we had a high power system tripping and occasionally blowing
up at 7:00 AM. It turned out that it was when the power company switched
big capacitors across the lines as businesses got started to keep the power
factor within their target range. It was creating just the kind of
transient that drove the controller loop of the power factor corrector in
our power supply to go bezerk (62kW converter running off 480VAC 3 phase).
The system had been tested to MIL-STD-704 transients and passed, but that
capacitor switching just killed it.

On Sep 29, 2017 8:15 AM, "Rob Kimberley" <robkimberley at btinternet.com>

> I'd go with a power surge as it's so regular at 8AM.
> Rob
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Skip
> Withrow
> Sent: 28 September 2017 21:18
> To: time-nuts
> Subject: [time-nuts] Weird GPSDO behavior
> 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 yet.
> Anybody seen anything like this, or have any good ideas?
> Thanks in advance,
> Skip Withrow<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table
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