[time-nuts] Beginner's time reference

[Bob Camp]

Hi

1 second in a year is 3.2x10-8. There are OCXO's that will do that with some
"tender loving care". Unless your Rubidium breaks it should do that easily.

In both cases you will want to get it set on frequency and time at the start
of the year. Back to GPS ....

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Justin Pinnix
Sent: Friday, December 11, 2009 9:50 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Beginner's time reference

I'm hearing a lot of recommendations for types of oscillators, but noone has
asked the question - what is the desired performance?

For me, I wanted a clock that stays within a second of UTC for a year.  I'm
pretty sure the LPRO I bought will exceed that, (though I guess I won't know
for another 12 months).  Of course, I needed a way to evaluate what I built,
so I also picked up a Thunderbolt.  What was that about a tar pit? :-)

I built my own clock/counter circuit, but it was a lot of work.  I see a lot
of Datum 9100s for sale on eBay for under $50.  Has anyone tried out one of
those?

I still need to write up my circuit, but it is similar to (but not based on)
this:  http://www.qsl.net/zl1bpu/MICRO/CLOCK/

Thanks,
-JP

On Fri, Dec 11, 2009 at 8:42 AM, John Miles <jmiles at pop.net> wrote:

> > Bill,
> >
> > he was planning to spend 100 USD on a used Rubidium, I think a Cs is way
> > over his budget ;-)
>
> Luck has more to do with that than money.  My cheapest cesium standard, at
> $500, also turned out to be the only one out of three with a healthy tube.
>  You have to plan on buying a few turkeys.
>
> If you're shopping for a cesium standard on eBay especially, where the
> sellers don't tend to know what they're selling or how to test it, it
makes
> sense to bid low and wait until you get lucky.
>
> > But I agree that a Rubidium has a shorter life span and if you get one
> > for 100 USD on eBay, I would expect it to be "worn out" already.
>
> The LPRO-101 I bought from China recently for ~$100 is in good shape (it's
> the dotted blue trace in the plot I posted earlier, measured against the
> aforementioned $500 Cs.)  It locks up quickly, and its lamp voltage is
right
> in the middle of the normal range.  Others have had good results from the
> same seller, so I think they're actually pretty safe.
>
> -- john, KE5FX
>
>
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