[time-nuts] Adapting my GPSDO to the FE-5680A

Attila Kinali attila at kinali.ch
Thu Apr 21 04:53:56 EDT 2016


On Wed, 20 Apr 2016 15:31:04 -0700
Nick Sayer via time-nuts <time-nuts at febo.com> wrote:


> I believe there are two separate commands for tuning the 5680 - one is
> “temporary” and one writes through to the EEPROM. I’ll be using the latter,
> of course.

Ah.. ok. Didn't know there are two.


> http://www.ka7oei.com/10_MHz_Rubidium_FE-5680A.html
> 
> I do agree that the short term stability of the 5680A isn’t as good as an
> OCXO, but at tau ~2s or so, the tables are turned. I’m getting a good measure
> of my undisciplined 5680A as we speak to get a good control, but it’s
> difficult, as I’m testing it against a Thunderbolt, and I think I’m seeing
> its “hump” (http://www.leapsecond.com/pages/gpsdo/) from 10s to 300s coming
> through.

Comparing an Rb to a GPSDO at taus below 1k-10k seconds is probably being
dominated by the GPSDO noise anyways. To actually see the stability
improvements of using an Rb as oscillator for an GPSDO instead of an OCXO
you will need something more stable. Either use an ensemble of good rubidiums,
or you need a Cs beam standard. Using multiple GSPDO with different antennas
is not going to help as the errors will be correlated due to short baseline.


> In any event, I’m getting awfully close to the limits of my 53220a.

There are people working on solving this problem :-)

> I may go down the road of trying to make a mash-up as you suggest,
> but I’m going to start by seeing if I can give myself a choice between
> whether I want short term stability (OCXO) or medium term (Rubidium)
> for my reference.

Hehe.. it looks like you are going down the time-nuts road ;-)


			Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson


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