Hi With WWV you need to do it at the right time and the right frequency. There may not be a right combination every day. You want to do it when you have a stable path between you and them. That can (and does) happen, just not all the time.
Bob On Mar 1, 2014, at 9:55 PM, Alex Pummer <[email protected]> wrote: > that WWV has some problem, the propagation path is not very stabile, > therefore the arriving signal is phase modulated, if you look it for short > time the phase modulation looks like frequency modulation it means the > frequency is changing = not stabile, WWVB is a bit better since it ha a more > stabile propagation path due to it's much lower frequency, 60kHz but there > are al our nice switching mode power supplies which generating lots of > concurrence for WWVB, so it is not so simple task to receive it clean > 73 > KJ6UHN > Alex > > On 3/1/2014 6:31 PM, Tom Van Baak wrote: >> Hi Bob, >> >> Everything about time & frequency is simply a matter of degree, of decimals >> points. If all you require is 1 second accuracy then any old WWVB RC clock >> will work. >> >> If you want 0.1 second, or 10 ms, or 1 ms accuracy a PC running NTP should >> work. >> >> As you push closer to the microsecond level you need a correspondingly >> better internal stable frequency source (e.g., rubidium) or external >> accurate time source (e.g., GPS). Most of us use GPS one way or another, >> achieving 100 ns accuracy with no effort and 10 ns with extreme effort. >> >> Listening to WWV makes a nice example. Where I am near Seattle, say 1000 >> miles from NIST, the radio wave delay from Ft Collins (due to speed of >> light, 1 ns/foot, or 5 us/mile) is about 5 ms. The delay from the WWV radio >> speaker to my ear (due to the speed of sound, 1 ms/foot, or 5 s/mile) is >> about 5 ms. >> >> /tvb >> >> ----- Original Message ----- >> From: "Bob Albert" <[email protected]> >> To: "Discussion of precise time and frequency measurement" >> <[email protected]> >> Sent: Saturday, March 01, 2014 6:04 PM >> Subject: Re: [time-nuts] Another "atomic" clock question >> >> >> 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 <[email protected]> >> 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 <[email protected]> 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 <[email protected]> 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 >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
