[time-nuts] Strange effect with C-Field change
John Ackermann N8UR
jra at febo.com
Thu Mar 24 13:44:35 EST 2005
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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