[time-nuts] Next upgrade

[Adrian Godwin]

Yes, I cross-connected  the pins, but I didn't cut any short.



On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> I have run a number of the REF0 / REF1 combos. They all seem to work fine.
> The standard cable has some odd short pins on it. If you are not hot
> plugging
> the cable I don’t think they matter at all. If anything, the system is
> more reliable
> with a normal length pin on the connector.
>
> Bob
>
> > On Nov 22, 2017, at 6:08 PM, Adrian Godwin <artgodwin at gmail.com> wrote:
> >
> > I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
> > Oncore GPS receiver to one of them as per Peter Garde's notes and it
> works
> > well.
> >
> > But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
> > configuration. Not that I need an HA reference but just for interest.
> I've
> > only had a quick look so far and found that connecting the two together
> > with a 15-pin cable didn't work.
> >
> > Has anyone looked into this ?
> >
> >
> > On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> >> Hi
> >>
> >>
> >>
> >>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock <jerry at hanler.com> wrote:
> >>>
> >>> Three questions:
> >>>
> >>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
> >> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
> >> some other technique to improve the short and/or long term performance?
> >>
> >> You can monitor one against the other. Ideally you would want three
> >> GPSDO’s and a
> >> monitoring setup. That way you can figure out which of the three has
> gone
> >> bad.
> >>
> >>>
> >>> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
> >> and was now thinking of purchasing one of the PRS-10 that I see on
> Ebay. If
> >> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
> >> what impact would this have on the overall performance both with and
> >> without (when in hold-over)?
> >>
> >> If you go into holdover, you are the exception. Most setups rarely go
> into
> >> holdover. When they
> >> do, it’s because a hurricane just went over the house. Generally that’s
> >> not when the focus is going
> >> to be on timing experiments.
> >>
> >>> Basically, is it worth the money to upgrade one of the boxes to a
> >> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
> >>
> >> Not worth the money if you are only looking at holdover and have a
> typical
> >> setup.
> >>
> >>>
> >>> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
> >> is there a better option to improve my GPSDO system?
> >>
> >>
> >> Disciplining implies continuously correcting. Rb standards age much less
> >> than a typical
> >> OCXO. Oddly enough their temperature stability may not be as good as a
> >> high end
> >> DOCXO. It is fairly common to try to stabilize the environment your
> >> standards operate in.
> >> To the extent you are successful this reduces the need to deal with
> >> temperature.
> >>
> >> The net effect is that disciplining an Rb at a rate (filter / control
> loop
> >> / manual tweak) of less than
> >> a few days actually makes the Rb worse. Coming up with software to “back
> >> off” on the tuning is
> >> not as simple as it might seem.
> >>
> >> This comes back to the fact that the GPS signal (or any of the sat
> >> signals) are quite noisy. You
> >> need to average them over a *long* time to get good performance. Rb’s
> are
> >> enough better than
> >> a GPSDO OCXO that the time ranges really stretch out ….
> >>
> >>>
> >>> I basically use the GPSDO as a reference for any equipment that takes
> an
> >> input. I have no monetary need for a reference, just an interest.
> >>
> >> For most normal test equipment, a GPSDO output is “plenty good enough”.
> As
> >> a source for fancy
> >> timing experiments … maybe not so much. As a phase noise reference or a
> >> spur free source for
> >> microwave games … also not the best way to go.
> >>
> >> Bob
> >>
> >>
> >>>
> >>> Thanks.
> >>>
> >>> Jerry
> >>>
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