The ground wave path of WWVB varies due to a very small changes in the index of refraction (temperature and absolute humidity) over the path. It is not much, but is measurable. Don
paul swed > I use GPS and LORAN. Always nice to have a backup > With LORAN being shut down, have resurrected the ole wwvb rcvr and built > an > amplified loop ant. > Can work but it takes about 3-5 hours to get to 1X10^11 accuracy. Still > observing various strange ness shuch as diurnal shift ... > Odd wwvb works at least for me most stable in the day. I seem to remember > night was supposed to be better. > The signal is much stronger at night. > So I guess its a play but sure not as easy as gud ole LORAN C has been. > > On Fri, Nov 13, 2009 at 12:48 PM, Brian Kirby > <kilodelta4foxm...@gmail.com>wrote: > >> You will need a receiver to compare your references to. It appears that >> LORAN will be shut off, so that leaves two services available, either >> WWV 60 >> Khz or GPS. I do not use WWV any more, I can tell you about GPS. >> >> To compare against GPS you will need a timing receiver, there are >> several >> available. A lot of us got Motorola Oncore VPs, UTs, or M12+, The >> Rockwell >> Jupiter is one and there are several more. They provide a 1 PPS signal >> that >> is locked to the on board standards on the GPS satellite. You put this >> signal in one input of a time interval counter. You use a 1 PPS divider >> on >> your local reference and put its signal in the other input of the time >> interval counter. You can record continuous or take daily 24 hour >> readings >> and derive your drift rates. >> >> GPS corrections are published at NIST; >> http://tf.nist.gov/service/gpstrace.htm >> >> You can also compare against a GPS disciplined oscillator. In the long >> term it should be dead on, you will have to have it characterized for >> the >> short term. The HP Z3801A was on the surplus market several years back, >> its >> probably one of the best. The Trimble Thunderbolts were available to >> the >> group a while back. >> Brian KD4FM >> >> >> Glenn Little WB4UIV wrote: >> >>> While I was in the US Navy we had two Cesium standards for the >>> navigation >>> center on SSBN submarines. >>> While in port, we would track LORAN C and compute the drift rate of the >>> two cesium standards. >>> Is there a service, that has drift rates published, that I can compare >>> my >>> standards to, so that I can determine the standard drift rate. >>> I do not remember the drift rates that we determined on the submarine, >>> that was a few years ago, but, I seem to remember that the rate was in >>> the >>> low nanoseconds. >>> If a rubidium standard drifts in one direction (does it?) a drift rate >>> could be calculated and, after a comparison to a known standard, with >>> known >>> drift rate, a very accurate standard could be had for the lab. >>> >>> What would I expect the drift rate, or jitter, to be in a FRK class >>> rubidium oscillator? >>> >>> Is the drift rate constant enough that a drift rate could be applied to >>> a >>> rubidium oscillator to determine it's real frequency at any given time. >>> >>> We calibrated the submarine Cesium standards every three months. >>> We had to know the drift rate of our standard as well as the drift rate >>> of >>> the standard in each of the LORAN stations to be able to do the type of >>> LORAN navigation that we did. >>> >>> I would like to be able to verify that my PTB-100 rubidium oscillator >>> is >>> on frequency. >>> >>> If I compare two rubidium oscillators, what would I expect the relative >>> drift rate to be? >>> >>> Thanks >>> 73 >>> Glenn >>> WB4UIV >>> >>> >>> >>> >>> _______________________________________________ >>> 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. > -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ 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.