[time-nuts] GPSDO uncertainties

ew ewkehren at aol.com
Mon Oct 8 15:52:51 EDT 2018


There are many issues with the Tbolt, specially if you look at 1 second and below. But at 10 seconds they mostly average out. If you look at the attachments first the 1pps varies by 20 nsec, has nothing to do with the Tbolt. It is GPS and the change in propagation from day to night of the ionosphere. Second Tbolt was intended as a timing device, frequency is secondary and is used to correct timing. Plot shows it is within 1 nsec short term. Nice
Even very good and expensive OCXOS like the OSA 8600 frequency at best is 2.3 E-12 at 1 second. Forget the 8607. Not talking ADEV. That is our design goal for a GPSDO.The frequency plot tells you that at 10 seconds it is safe to assume +-3E-11. The Tbolt has been in continuous operation for three years and I am fortunate to have an excellent antenna location. Strictly interested in Frequency and clean up with an Austron 2110. Not shown. Reference is a HP 5061B set to 2E-13.Hope this helpsBert Kehren
In a message dated 10/7/2018 10:00:38 PM Eastern Standard Time, donaldbcollie at gmail.com writes:

I have a GPSDO which has a Trimble receiver, and Trimble OCXO inside.[Ithink it runs Lady Heather] What I would like to know is what uncertaintythe 10MHz output will be with a 10 second count.This presumes that theGPSDO is receiving satellite signals, and the OCXO is being suitablydiciplined. Should I expect 1 part in 10E12?, 1 part in 10E10?. This devicegives superior performance to an OCXO barefoot - but how much better? Wouldsomebody in the group who knows the answer, please wax elequently.Thankyou,.................................................................................................DonaldB. COLLIE_______________________________________________time-nuts mailing list -- time-nuts at lists.febo.comTo unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.comand follow the instructions there.
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