[time-nuts] Interesting Phase Bump...
Tom Van Baak
tvb at leapsecond.com
Wed Nov 24 18:05:58 EST 2004
This kind of stuff happens to me all the time. You
get a nice set of data for a day or two and are just
about ready to compute drift rates and call it quits.
But then the oscillator reads your mind and changes
rate a bit; just enough that you decide to keep the
counter going and collect data a couple more days,
"just to be sure". Then it does something else; and
you have to keep it going even longer. So the next
thing you know you're looking on eBay for another
counter so you can leave the old one permanently
connected to the oscillator. ;-)
I bet you're so curious what happens after day 13
that you leave the counter running a while longer...
Seriously, there may actually be something to this
plot, but you can't be sure until you have a lot of
data to separate normal from anomaly. What does
the conv phase->freq plot look like?
----- Original Message -----
From: "John Ackermann N8UR" <jra at febo.com>
To: <time-nuts at febo.com>
Sent: Wednesday, November 24, 2004 13:47
Subject: [time-nuts] Interesting Phase Bump...
> I've attached a phase plot of my 5065A vs. GPS 1pps from a Motorola
> UT+. There's an interesting bump in the phase -- for the first two days
> and the last five days, the offset is about -7x10e-13. But for about
> four days in the middle there's a flattening and then increase in
> relative phase to about +3x10e-13, then a return to the original offset.
> As far as I know, there was no local change to account for the bump --
> temperature in the basement didn't change too much (though unfortunately
> my temp recording system is down at the moment) and neither the
> standard, the GPS, nor the time interval counter were changed in any way.
> I'm assuming that the phase change was in the Rb and not the GPS (or the
> GPS constellation), but I don't know that for sure. What's particularly
> interesting is that the offset returned to just about the original rate
> and not to something different -- I would have thought that something
> changing in the 5065A wouldn't result in a return to the same offset.
> Anyone have any ideas what could have caused this change?
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