In a message dated 02/03/2014 02:07:05 GMT Standard Time, bob91343@yahoo.com writes: 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. ------------------------- Hi Bob Without wanting to get bogged down in questions of how long is a piece of string and close is close etc etc, I do think your best starting point would be a GPS frequency standard. Nothing is ever perfect, but without reliable access to alternatives, such as Loran or WWVB and its equivalents, a GPSDO is still just about the only option available at anywhere near a sensible price that is likely to do what you're asking. It shouldn't mean either that buying one automatically excludes the option of eventually building your own, or otherwise getting more deeply involved. Once started on the slippery slope there's more than enough opportunity for experimentation with well proven designs and concepts aready out there to provide endless fun, and/or frustration:-) After that there's no telling where you might end up:-) It is true, as has been stated, that the Trimble Thunderbolt isn't quite the economic entry point it once was, but that doesn't mean there aren't viable alternatives. One good example is the Trimble Nortel NTGS50AA, as can be found in Ebay buy it now 291054324150 and often for a bit less in auctions from the same seller. These might be getting a bit long in the tooth, there has been some experience of oscillator's having aged to outside the unit's EFC range, although they generally do work "out of the box", even though there isn't one:-), but the seller is helpful and should it prove necessary the oscillator can be changed with a bit of care. As a bonus, Lady Heather, she of Thunderbolt whipping fame, can also knock these into shape, and there's plenty of existing users here with experience of them. There is then, of course, the consideration of how you compare your oscillators with the standard, do you have or do you invest in an appropriate frequency counter?, do you have or do you invest in a suitable 'scope plus the necessary time to monitor the drift?, and so on and so fifth. What was that about the length of a piece of string?:-) Regards Nigel GM8PZR ---------------------------- 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: > 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: > > >> 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 -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.