[time-nuts] Improving on basic L1 timing

Attila Kinali attila at kinali.ch
Tue Jun 14 13:10:06 EDT 2016

On Tue, 14 Jun 2016 21:37:20 +1000
Michael Wouters <michaeljwouters at gmail.com> wrote:

> On Tue, Jun 14, 2016 at 6:16 PM, Angus <not.again at btinternet.com> wrote:
> > I'm planning to test some rubidiums again, but since Santa never did
> > get me that hydrogen maser I asked for, I'm still stuck with ordinary
> > gps timing receivers as a separate medium to long term reference. The
> > atmospheric issues are probably the main ones I would like to get rid
> > of, although the more errors removed the better.

Make sure you have good skyview (aka good geometry) and very little
multipath. Both effects can affect the precision of your solution
much more than the ionospheric delay variation.

> Otherwise, GPS common view to a better clock may be an option. If you
> are reasonably close to a national standards lab, you might be able to
> use their time-transfer files to compare your rubidiums with their
> time scale - not everyone makes them publically available though.
> Otherwise, if there is an IGS station near you, you could use the
> station RINEX files and IGS clock solutions which are freely
> available. Many IGS stations have a H-maser as the local clock. But it
> may be just as good to simply use the comparison with GPS time
> inherent in the time-transfer file.

If you live in continental Europe, then you will inevitabely have an
IGS station nearby. They are everywhere! :-)

I wonder how good the final IGS solution for ionospheric and orbits
are, repectively how much you get out of waiting longer?
Especially if the next IGS station is more than a couple km away.
Does anyone have data on that?

> All of the above is software-oriented, whereas you seem to be looking
> for a hardware solution, but that's what I know best.
> and follow the instructions there.

I don't think you can get much better with an hardware only solution
than by using the IGS files. Even if an L1/L2 receiver gives you better
ionospheric estimates, the orbit uncertainties still need postprocessing
to be corrected.

The only other thing I can think of is using multiple Rb's as reference,
measure their temperature, air pressure and drift against GPS. Use all
this data to build a clock model (aka Kalman filter) that compensates
for temp/pressure/aging and measure the Rb under test against this ensemble.

But that's not something that already exists and is ready to use.
And I doubt that this can shave off much more than one order of magnitude
in ADEV.

			Attila Kinali

Malek's Law:
        Any simple idea will be worded in the most complicated way.

More information about the time-nuts mailing list