[time-nuts] Interesting Phase Bump...

John Ackermann N8UR jra at febo.com
Wed Nov 24 19:11:19 EST 2004

You pretty much read my mind (and intentions), Tom!  Actually, I'm about 
to leave for a 2+ week business trip, so will leave the data collection 
running while I'm gone.  Assuming nothing crashes, I'll have at least a 
month of data before I pull the plug. Hopefully that'll be enough to 
tell if this is a one-time thing or something with a pattern.


Tom Van Baak wrote:

>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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