Hi

From what I’ve seen, if you are after a large wall clock with mechanical hands on it, you already have the top of the line. There are others out there. The ones I’ve seen or tried are no better than what you already have. Many of them are worse...

Yes, that’s sad. They are designed to hit a price point.

Bob

On Feb 23, 2014, at 3:56 PM, Steve steve65@suddenlink.net wrote:

Steve,

Now that you have brought up this subject, do you know of any way to use these LaCrosse clocks to calibrate frequency standards?  It seems to me that since we can buy a cheap device that receives and decodes the WWVB signal, it shouldn't be a big step to use it as a basis for frequency measurement.

Bob

On Sunday, February 23, 2014 1:21 PM, Bob Camp lists@rtty.us wrote:

Hi

From what I’ve seen, if you are after a large wall clock with mechanical hands on it, you already have the top of the line. There are others out there. The ones I’ve seen or tried are no better than what you already have. Many of them are worse...

Yes, that’s sad. They are designed to hit a price point.

Bob

On Feb 23, 2014, at 3:56 PM, Steve steve65@suddenlink.net wrote:

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Hi

These clocks (and their wrist watch cousins) work fairly simply. They decide on a time of day (maybe midnight) and try to pick up WWVB. If they succeed in getting a time signal, they sync up to it and turn off the receiver. If they do not succeed, they try again later (maybe 15 minutes, maybe an hour). If after several tries they don’t get anything, they go back to sleep (radio wise) and try again the next day.

This is a great approach if you want to save battery power. It’s all integrated in a single IC deep in the clock or watch along with all the drivers for what ever sort of display the thing has. They don’t make this kind of stuff out of bits and pieces anymore.

The bottom line is that there is only a “signal” present for a very brief period each day. If they get +/- 0.1 seconds, they are doing amazingly well. Turning that into a frequency measurement device - not so easy.

The simple approach: Run a wall clock off of your DUT and compare it to the second hand on the WWVB clock. In a few weeks / months you will have a pretty good idea what’s going on. You probably will know it to as good as the Atomic Clock is capable of reporting.

Bob

On Feb 23, 2014, at 4:33 PM, Bob Albert bob91343@yahoo.com wrote:

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

Radio Shack used to sell some too, they are digital,  I have one for at
least teen years it is working fine all the time battery last almost the
shelf life -- three years two AA.
73
KJ6UHN
Alex

On 2/23/2014 12:56 PM, Steve 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@LeapSecond.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@rtty.us 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@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@rtty.us wrote:

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and follow the instructions there.

Hi

If all you need is frequency to 0.1 ppm, then a zero beat with WWV under good conditions will take care of your needs. If you need 0.1 ppb then it’s going to be harder to do. I’m assuming you are already into the “harder” category and WWV does not do what you are after.

Like it or not time and frequency are joined at the hip. If you have trouble with one, it will show up in the other.

If you want a “pure” frequency reference, you really only have one option - get a cesium beam standard and plan to replace the tube every so often. Even if you have one, there are still tweaks you would need to do to be sure it’s right.  That’s mostly hard in the bank account department. You’ll spend more on the Cs than on a car.

The only practical / cheap way to get accurate frequency in your basement is by doing a time comparison. There are lots of sources of accurate time out there. Setting up for a time comparison is really no more difficult than setting up for a good frequency comparison. Both take some care and some time. There’s no free lunch.

These days, GPS is probably the best way to get the job done. There are $100 (ish) boxes on the auction sites that will do it all for you.

Bob

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