[time-nuts] FE-5680A arrived
EWKehren at aol.com
EWKehren at aol.com
Thu Jan 12 06:27:43 EST 2012
I am in week 7 and still se no aging at 1 E-12. Look forward doing other
tests like voltage sensitivity and bringing out the C field for external
adjustment. Right now hands off. Frustrating but I am determined to get some
aging data first. I do not know if keeping it nice and cool helps keeping
aging down but does help component life.
In a message dated 1/11/2012 8:33:18 P.M. Eastern Standard Time,
GandalfG8 at aol.com writes:
My observations are that the RS232 offset on these needs to be considered
as very much a fine adjustment only, and presumably just intended to pull
the frequency on to 10 MHz rather than to provide a usable offset.
I did try pushing my first unit to the extremes of the adjustment range
shown in the manual and it didn't like it, the frequency was highly
and at one extreme it just gave up and rejected the offset.
Observations on three units so far indicate that none seem to have had any
offset programmed in the field but all are less stable the further they
from being set to 10MHz.
I haven't recorded any long term data as yet, just observed the short
stability on an HP 53132A and Tek FCA3100 clocked against one of three
T'bolts, but am getting a definite impression that 10MHz is a sweet spot
that anything either side is just begging to be corrected:-)
In a message dated 12/01/2012 01:04:03 GMT Standard Time,
smither at c-c-i.com
More observations. My unit is S/N 0316 61953, UN 63983. If I try to
offset count (using RS232) by more than about 131,000 counts (0x20000) at
it sometimes loses the 1PPS and the lock signal goes high.
By bringing the offset count up slowly (increments of 0x10000) I recorded
following drift rates versus offset count:
0 usec / sec at 0
1 usec / sec at 1441792 (0x160000)
2 usec / sec at 2949120 (0x2D0000)
3 usec / sec at 4390912 (0x430000)
4 usec / sec at 5898240 (0x5A0000)
The offset count was incremented in units of 0x10000 (65,536) counts so
drifts are approximate.
A plot of these results is here:
My unit appears to have an adjustment resolution of about 6.8E-13 / count
close to what has been reported here before.
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