[time-nuts] FE-5680A Results so far

Bob Smither smither at c-c-i.com
Wed Dec 28 18:45:20 UTC 2011


Chris Albertson wrote:
> Just got my fe5680 yesterday.   Seems to work but the fe5680 is the most
> accurate reference I have.  So how to test it?   I plan to buy a
> Thunderbolt but until then, anyone have any creative ideas?

<snip>

> Going to have to get a Thunderbolt.  I have an Oncore UT+ the provides a
> good pulse per second but that will not help

You can take the FE-5680 10MHz and divide it down to a derived 1 PPS.  Use the 
time interval measurement on your HP5328A to measure the TI between the Oncore 1 
PPS (start) and the derived 1 PPS (stop).

You might want to set a finite TI (for example, 100 usec) by adjusting the phase 
of the derived 1 PPS so the measurement doesn't get confused.

I have done this using an HP5316B with good results.

The jitter on the GPS 1 PPS might limit your short term resolution, but over a 
day or so you should be able to measure the drift of the FE-5680A.

I have used a Ref Tek 111A GPS clock for the 1 PPS.  That unit has a lot 
(several usec) of jitter.  I recently started using a 111C that has much lower 
jitter (a few 10's of nsec).  I believe your OnCore unit will be similar.

Here are some results from my tracking my FE-5680A:

   http://c-c-i.com/image/tid/4

Most recent:

   http://c-c-i.com/node/159

Hope this helps.

-- 
========================================================================
Bob Smither, PhD                                  Circuit Concepts, Inc.

"Patriotism is supporting your country all the time, and your
    government when it deserves it."
                       - Mark Twain

Smither at C-C-I.Com           http://www.C-C-I.Com            281-331-2744
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