[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.
Bert Kehren
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  
change the
offset count (using RS232)  by more than about 131,000 counts  (0x20000) at 
a time
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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