AW: [time-nuts] Strange effect with C-Field change

Hubert v. Bonhorst hvonbonhorst at
Thu Mar 24 15:09:05 EST 2005

If you disregard this excursion, what happened after the change. Did
frequency change as expected? Would there have been continuity of data?
Which TIC do you use? Which GPS receiver do you use? How many satellites did
you track? What is the minimum elevation for satellites used?
I know a lot of stupid questions, but ....

-----Ursprüngliche Nachricht-----
Von: time-nuts-bounces at [mailto:time-nuts-bounces at] Im
Auftrag von John Ackermann N8UR
Gesendet: Donnerstag, 24. März 2005 19:45
An: Discussion of precise time and frequency measurement
Betreff: [time-nuts] Strange effect with C-Field change

While I was out of town for the last week, I continued an experiment to 
check the C-field sensitivity of my 5061A.  I measured the offset at 
C-field settings of 5.00, 5.50, and 4.50.

The last change was made while I was out of town.  My wife, Jody, made 
the change from 5.50 down to 4.50.  She adjusted the knob fairly slowly 
(over 10 seconds or so) and didn't overshoot or reverse direction.  
Immediately, after she did this, there was a *huge* phase shift (of the 
1pps vs GPS) that lasted for several hours, and then returned to 
virtually the same point as it was before the change.  We're talking 
huge, from an offset of a couple of microseconds up to more than 100 
milliseconds, then returning back to the microsecond range and 
apparently normal operation.  A plot of the phase during this time is 
attached (note that the Y axis is logarithmic).

When I saw this anomaly show up, I assumed that maybe something had 
happened to cause the 5061A to lose lock momentarily.  So, imagine my 
surprise when I came home today and discovered the "continuous 
operation" lamp was still lit and there was no sign of any event that 
would have caused this.  Unfortunately, I wasn't doing any other 
tracking at the time, so I can't tell if it was a GPS anomaly or 
something else -- though the fact that it happened just as the C-field 
was changed sure seems to point to that as the culprit.

Anyway, has anyone seen anything like this, or have any idea what might 
have happened here?


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