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#31 (**permalink**) 03-28-2008, 04:31 AM

On 22 Mar 2008 12:46:21 GMT
Huge <Huge@nowhere.much.invalid> wrote:

> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
> > Huge wrote:
> >> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
> >>> Huge wrote:
> >>>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
> >>>>> Rex Mottram wrote:
> >>>>>
> >>>>>> Put the indoor machine in the refrigerator.
> >>>>>>
> >>>>>> RM
> >>>>> Unfortunately, that is not practical given the particular
> >>>>> constraints I have
> >>>> Are the machines close enough together to connect a cable
> >>>> between them?
> >>>>
> >>>>
> >>> No - otherwise it would be easy with NTP over ethernet.
> >>
> >> Quite.
> >>
> >> So, how far apart are they?
> >>
> > The distance is not great - perhaps a few tens of metres, but it is
> > totally impossible to have any cables between the two locations.
>
> Is this one of those interview questions which has no answer?
>
>

)
>
Hi
What about a couple of linksys WET54G wireless bridges to connect them?

--
Cheers Malcolm °¿° (Linux Counter #276890)
SLED 10.0 SP1 x86_64 Kernel 2.6.16.54-0.2.5-smp
up 10 days 0:54, 1 user, load average: 0.24, 0.32, 0.35

#32 (**permalink**) 03-28-2008, 04:31 AM

Malcolm wrote:

>> Is this one of those interview questions which has no answer?
>>
>>

)
>>

I think local generation of 1 pulse per second will be practical

> Hi
> What about a couple of linksys WET54G wireless bridges to connect them?

I dont know if there will be sufficient signal received. There might be,
but it depends on the RF screening, which I expect to be quite significant.

#33 (**permalink**) 03-28-2008, 04:31 AM

In comp.sys.sun.hardware Dave <someplace@nowhere-nice.com> wrote:
> I think local generation of 1 pulse per second will be practical

Just a paranoid question - you will be able to make sure the two PPS
sources are in phase at the start right?

rick jones
--
portable adj, code that compiles under more than one compiler
these opinions are mine, all mine; HP might not want them anyway...

feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

#34 (**permalink**) 03-28-2008, 04:31 AM

[A complimentary Cc of this posting was sent to
Dave
<someplace@nowhere-nice.com>], who wrote in article <47e06510@212.67.96.135>:
> I suspect if I sync them by NTP before the experiment starts, then they
> will not drift by more than 500 ms over a 4 hour period. Does that seem
> reasonable? Has anyone actually ever made medium term (few hours)
> stability measurements of the clocks in Suns?

Another (crazy?) idea: buy a digital clock which can beep every
minute, and syncronize via a mic.

Yours,
Ilya

#35 (**permalink**) 03-28-2008, 04:31 AM

Rick Jones wrote:
> In comp.sys.sun.hardware Dave <someplace@nowhere-nice.com> wrote:
>> I think local generation of 1 pulse per second will be practical
>
> Just a paranoid question - you will be able to make sure the two PPS
> sources are in phase at the start right?
>
> rick jones

The unit I have

http://www.thinksrs.com/products/PRS10.htm

will sync its 1 pps output to a 1 pps input. Hence use GPS to generate 1
pps, then the rubidium generates 1pps in phase with that. Then, when the
GPS signal is lost, the rubidium will keep pretty accurate.

"When an external 1 pps signal is applied the PRS10 will verify the
integrity of that input and will then align its 1 pps output with the
external input. The processor will continue to track the 1 pps output to
the 1 pps input by controlling the frequency of the rubidium transition
with a small magnetic field adjustment inside the resonance cell."

I just need to get another of these.

#36 (**permalink**) 04-03-2008, 02:40 PM

In comp.sys.sun.hardware Dave <foo@coo.com> wrote:
> That is a possibility. I have one of these

> http://www.thinksrs.com/products/PRS10.htm

> which is a rubidium oscillator. I could get another and sync them
> both to GPS. A bit more complexity than I wanted, but it might be
> necessary.

Nah, just get yourself one of these watches

http://www.leapsecond.com/pages/atomic-bill/

Then you can simply walk the time from one setup to the other.

rick jones
--
Process shall set you free from the need for rational thought.
these opinions are mine, all mine; HP might not want them anyway...

feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

#37 (**permalink**) 04-03-2008, 02:40 PM

Rick Jones wrote:
> In comp.sys.sun.hardware Dave <foo@coo.com> wrote:
>> That is a possibility. I have one of these
>
>
>> http://www.thinksrs.com/products/PRS10.htm
>
>> which is a rubidium oscillator. I could get another and sync them
>> both to GPS. A bit more complexity than I wanted, but it might be
>> necessary.
>
> Nah, just get yourself one of these watches

>
> http://www.leapsecond.com/pages/atomic-bill/

Yes, I was aware of that one. Tom has some other funny things on his web
site. Totally devoted to accurate time keeping. For anyone that has
never looked at Tom's site, especially if you have an engineering mind,
I suggest you do.

Another site I very much admire is this one. You only have to be male to
appreciate 50% of the site, and know about semiconductor physics to
appreciate the other 50%.

http://britneyspears.ac/lasers.htm

#38 (**permalink**) 04-03-2008, 02:40 PM

On Tue, 01 Apr 2008 22:40:58 +0100, Dave wrote:

> http://britneyspears.ac/lasers.htm

Ah, yes! It has been decades since I looked at Schroedinger's equation.

#39 (**permalink**) 04-03-2008, 02:40 PM

Dave Uhring wrote:
> On Tue, 01 Apr 2008 22:40:58 +0100, Dave wrote:
>
>> http://britneyspears.ac/lasers.htm
>
> Ah, yes! It has been decades since I looked at Schroedinger's equation.
>

I used to work for the now defunt Marconi Optical Components. Marconi
had some really strict rules about what web sites one could and could
not visit, but we never felt too bad about going to the Britney Spears
web site.

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How accurate will Sun clock be over 4 hours?