[time-nuts] Syncserver S300 power supplies

[Todd Smith]

I am looking for replacement power supplies for a S300.  They use a Powdec
HDT125-43 power supply that is hard to find.  Powdec is out of business and
this power supply is a triple output unit +5v, +15v, -15v.

Anyone have a dead or decommissioned unit or spare power supplies that they
would be willing to part with for a nominal sum?

Thanks for a great list!  I learn something new most days.

Todd Smith

On Wed, Oct 5, 2022, 10:42 Todd Smith <tssmith2002 at gmail.com> wrote:

> As has been mentioned on the list recently, Jackson Labs builds a M12M
> multi-GNSS receiver that is a drop-in replacement for the Furuno
> receivers that are in the Syncservers that you are running right now.
>
> If I am not mistaken, Galileo uses close enough frequency to GPS that you
> can reuse the existing GPS antenna and receive both systems with a
> multi-GNSS receiver like the Jackson Labs units.
>
> Todd
>
> On Tue, Oct 4, 2022 at 9:29 PM Bob kb8tq via time-nuts <
> time-nuts at lists.febo.com> wrote:
>
>> Hi
>>
>> > On Oct 4, 2022, at 8:33 PM, Tim Lister <listertim at gmail.com> wrote:
>> >
>> > On Tue, Oct 4, 2022 at 4:57 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> >>
>> >> Hi
>> >>
>> >> The main issue with using the output of a GPS receiver directly is
>> >> dropouts. They can be caused by a variety of things. When the GPS
>> >> “goes away” you loose all timing information.  Do these various things
>> >> ( jamming, birds, lightning, …..) impact you? If they do, depending on
>> >> just how the loss of timing impacts you, you do or don’t have a
>> problem.
>> >>
>> >> Into an NTP server, the impact will still be there. How great an impact
>> >> it is depends a *lot* on what the next level source going into the
>> server
>> >> is. The commercial NTP gizmos tend to have things like OCXO’s or Rb
>> >> standards in them. That gives them a bit better performance than a
>> >> typical DIY computer based NTP server.
>> >
>> > Yes they would definitely impact us. I neglected to mention that we
>> > have the rubidium oscillator option as backup in these units to
>> > provide holdover. Mostly to provide insurance/holdover for the case
>> > that weather takes out the antenna to give time to ship a replacement
>> > out from HQ in CA to whichever site was affected. Given that one of
>> > the time servers provides the IRIG-B signal for the 400 Hz control
>> > loop for the drives for a ~20 ton 2-meter diameter telescope, I'm not
>> > keen on a homebrew Raspberry Pi solution however much I like them for
>> > my own time-nut home use...
>>
>> So indeed, having timing drop out is not a good thing ….
>>
>> >
>> >>
>> >> If you *do* go with a dual freq GPS, you can do a very good job of
>> working
>> >> out the location of your antenna. With some effort that can improve the
>> >> net timing accuracy. If post processing timing correction is ok in this
>> >> case, that also is a lot easier / more accurate with a full set of
>> dual freq
>> >> GPS data to correct against.
>> >
>> > A "real time" (latency ~<30 minutes) measure of the PWV would be
>> > helpful for scheduling/optimization of observations but there's also
>> > likely to be value in an improved value for use during later analysis
>> > at timescale >12 hours. Haven't done enough reading around of the
>> > literature on determining PWV from GPS to get a sense of where the
>> > error budget and improvements lie. I'm assuming something like a 48
>> > hour initial survey and having that post processed by e.g. the NRCan
>> > PPP service after the final GPS orbits are available would likely be a
>> > benefit but unclear how having a proper geodetic phase center vs a
>> > $200 bullet L1/L2/L5 antenna matters. Similarly it's not clear to me
>> > how much improvement in the water vapor determination comes from the
>> > increasingly precise (but increasingly delayed) GPS orbit products -
>> > it may be e.g. the Ultra Rapids are Good Enough.
>>
>> For about $100 ( delivered ) you can get a “pretty good” Chinese multi
>> band antenna. It’s not as good as fancy $2,000 antenna, but it’s way
>> better than a hockey puck. With that and a week’s data into NRCan
>> (it’s free ….. ) you can be pretty sure of your location to < 10 CM.
>> That’s
>> good enough to “not matter” for timing.
>>
>> >>
>> >> So, when it works, you might be down into the < 10 ns range. When that
>> >> bird sits on that antenna …. microseconds …. takes a nap …
>> milliseconds ….
>> >
>> > We're not an optical observatory so not in the pulsars & masers
>> > category. Driving demand on accuracy for us is normally very close,
>> > fast moving Near Earth Objects which can move at several hundred
>> > arcseconds/minute. If we don't want the timing uncertainty to degrade
>> > the position accuracy by more than the star catalog does, then we need
>> > timing precision in the ~1-10ms range. Determining diameters from
>> > occultations of stars by Kuiper Belt Objects, which have a transverse
>> > velocity of ~15 km/s, leads to similar requirements.
>>
>> The advantages of all this stuff ( single band vs multi band ) are in the
>> < 100 ns
>> range. If you do a good job on the single frequency stuff ( sawtooth
>> correction ….)
>> the improvement is < 20 ns.  There is a footnote down somewhere that
>> mentions
>> some sort of “99.9% of the time” stuff. There are unusual solar events
>> that can
>> push things well above the 20 ns range.
>>
>> Yes, there are other factors. There is another chunk for GPS <-> UTC.
>> There also
>> is a chunk for antenna / cable delays and the like. This stuff impacts
>> both approaches.
>> Normally that all should be < 100 ns. The delay part should be stable to
>> < 20 ns in
>> a typical setup.
>>
>> >>
>> >> Lots of tradeoffs.
>> >
>> > As always, tempered often by a lack of funds.
>>
>> Somehow money always matters :)
>>
>> Bob
>>
>> >
>> > Tim
>> >
>> >>
>> >> Bob
>> >>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>
>