[time-nuts] Another "atomic" clock question

paul swed paulswedb at gmail.com
Sat Mar 1 21:33:02 EST 2014


Careful where you step. You may just get sucked into time nuts and it never
stops.
Get a good crystal, then its an RB, next you know your paying shipping for
a 100 Lbs Cesium. Evil stuff.
Or you can just skip all the distractions and get a good GPSDO.
Not as much fun learning on the way. But depends on your end goal.
Regards
Paul
WB8TSL


On Sat, Mar 1, 2014 at 9:04 PM, Bob Albert <bob91343 at yahoo.com> wrote:

> All this is very interesting.  However, my interest is frequency.  In
> other words, I want to know that my standard oscillators are as close to
> desired frequency as possible, and how close that turns out to be.
>
>
> Yes, the Internet gives me time of day as close as I care to know.  I have
> an 'atomic' clock from LaCrosse that resets itself nightly, although it's
> fussy about where in the house I put it.  If I put it where I'd like, it
> won't receive WWVB, so I put it across the room.  I called the company
> inquiring about augmenting the internal antenna but they were of no help.
>
>
> While watching the clock and listening to WWV, it seems the clock is a
> fraction of a second behind.  Even that doesn't matter, but calibrating the
> counter time base is another kind of thing.
>
> I am trying to understand how this is done.  Should I ever get a rubidium
> standard, I'd want to check its calibration, and that's not a trivial
> exercise.
>
> Bob
>
>
>
>
> On Saturday, March 1, 2014 4:56 PM, Paul Alfille <paul.alfille at gmail.com>
> wrote:
>
> There are WWVB clocks with serial output. Arcron made one that I added
> linux ntp support for some years back.
> http://www.atomictimeclock.com/radsynarcron.htm
>
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver27.html
>
> As I recall, it was under $100, quite nicely styled, and is sitting here on
> my desk. (Reception on the East Coast can be spotty, so I've switched to
> standard internet net time source).
>
>
>
>
>
>
> On Mon, Feb 24, 2014 at 7:44 AM, Bob Camp <lists at rtty.us> wrote:
>
> > Hi
> >
> > Ok, so 0.1 second at the sync point is indeed a reasonable estimate. If
> > that's all you need to deal with (you correct out the crystal offset one
> > way or the other) then:
> >
> > At 1 day you have 11.5 ppm accuracy. Roughly a 100 Hz beat note with WWV
> > at 10 MHz.
> >
> > At 10 days you have 1.15 ppm. Roughly a 1 Hz beat note at 10 MHz.
> >
> > At 100 days you have 0.115 ppm. That would be about a 10 second period
> > beat note.
> >
> > None of that is to say that a beat note is all there is to getting
> > accuracy off of WWV or that the two approaches deliver the same net
> > accuracy. Yes I've done the 10 second beat thing, it can be done with
> care
> > and a good stable WWV signal.
> >
> > Bob
> >
> > On Feb 23, 2014, at 5:21 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> >
> > >> Now that you have brought up this subject, do you know of any way to
> > use these LaCrosse clocks to calibrate frequency standards?
> > >
> > > I suggest using a direct electric (1.5 VDC high-Z) or indirect magnetic
> > (high gain) pickup on the coil to get the +/- pulse per second. Compare
> > this time with your local frequency standard and over several days you
> > should get accuracy better than 10 ms per day (1e-7). Here's an example
> of
> > a raw phase plot:
> > > http://leapsecond.com/pages/Junghans/
> > >
> > > /tvb
> > >
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