[time-nuts] FE-5680A arrived
Bob Camp
lists at rtty.us
Thu Jan 12 17:36:24 UTC 2012
Hi
So, if it holds < 1x10^-12 (and maybe << 1x10^-12) for about two months,
what can you accomplish by locking it to a GPS? Your ADEV for very long
tau's should be sub 1.0x10^-13 (say 3x10^-14 at 100,000 sec).
You would have to have either a *very* long loop (weeks?) and/or a *very*
good GPS (big bucks) to keep from messing your Rb up.
The alternative would be to simply do a comparison every two months and
adjust it manually by the one or at most two DDS steps required.
Bob
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of EWKehren at aol.com
Sent: Thursday, January 12, 2012 6:28 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] FE-5680A arrived
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
unstable
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
are
from being set to 10MHz.
I haven't recorded any long term data as yet, just observed the short
term
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
and
that anything either side is just begging to be corrected:-)
Regards
Nigel
GM8PZR
In a message dated 12/01/2012 01:04:03 GMT Standard Time,
smither at c-c-i.com
writes:
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
the
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
the
drifts are approximate.
A plot of these results is here:
http://c-c-i.com/node/161
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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