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.alfi...@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 <li...@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 <t...@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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