Chuck Forsberg WA7KGX N2469R wrote:
I haven't checked it, but the FE5680A has 1pps on pin 6.There is no documented way to sync the FE5680A 1pps to an external reference. You could set an extreme value in the freq offset and wait for the 1pps to driftinto place.
On mine if you put in extreme offsets it seems to lose sync. Not sure if this is typical.
To adjust the phase between the GPS 1 PPS and the 1 PPS derived from the FE-5680A I put a switch in the divide by 1E7 logic used to get a 1 PPS from the FE-5680A. Pushing the switch changes the divide so that the 1 PPS can be slewed to a known phase WRT the GPS 1 PPS.
Measurements of the delay between 1pps signals depend on the accuracy of the measuringdevice - e.g., the timebase in the counter of oscilloscope X axis.
Yes, but for a time interval of (for example) 100 usec even a very poor counter timebase would be accurate to sub nsec. Of course, the FE-5680A could be used as the counter timebase :-).
On 12/28/2011 10:45 AM, Bob Smither wrote: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 helpYou 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. _______________________________________________ time-nuts mailing list -- [email protected]To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nutsand follow the instructions there.
-- Bob Smither, PhD Circuit Concepts, Inc. ========================================================================= Those who would give up essential Liberty, to purchase a little temporary safety, deserve neither Liberty nor safety. -- Benjamin Franklin: November 11, 1755 ========================================================================= [email protected] http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
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