That was the first time that I had seen an xy plot of WWV versus a stable crystal oscillator. It is even worse than I thought. I had to look up FRK to see that it is a rubidium standard. I talked to Jim Maxton the chief engineer of WWVB many times around 1995. At the time I was in Gila Bend 80 miles southwest of Phoenix. He had a Hewlett Packard cesium standard at Ft Collins. They were using a dual view GEOS Geostationary satellite to set the cesium to match the master clock in Boulder. If the cesium was good to 10^-13, that is 8.6 μs per day. I can't remember how close he tried to keep it or how often he adjusted it. It looked like that I could determine the start of the second to the individual transmitter cycle. Time transfer accuracy was therefore limited to the height changes of the ionosphere at sunrise and sunset.
The main disturbance was wind blowing the antenna. Ordinarily the phase would jitter a few degrees per second. I could tell the wind speed by the phase jitter without checking the Ft Collins weather. If memory serves, the loaded Q at 60 kc was about 200. A half percent tuning error caused a 45° phase error. I have seen a 45° excursions on several occasions over a minute more than once. My receiver had a slow lock mode that could spot them. It also had a 45° phase switch on the 100 kc local oscillator to eliminate the station ID from 10 to 15 minutes after the hour. There was therefore no disturbance in lock during it. I was never able to measure any error in the 45° phase advance. One degree would have been obvious. When I first got my receiver going, the phase would advance nearly 40° at the start of the second when the power was reduced by 10 db. It had been doing so for years and nobody noticed it. Maxton took an unneeded condenser out of his time code generator which fixed most of it. The new transmitter fixed the rest. Ft Collins is at 5,003 ft and clocks there run fast by 1.663·10^-13. (g/c^2)/meter) compared to sea level. How did you correct for altitude on yours? I presume that frequency is defined at sea level but I don't know that. Sea level clocks at the North or South Poles run fast relative to those at equator sea level by 1.192·10^-12. WB0KVV πθ°μΩω±√·÷Γλφ|Δ On Tue, Nov 20, 2018 at 9:06 AM jimlux <[email protected]> wrote: > > On 11/20/18 1:54 AM, ew via time-nuts wrote: > > Starting 1970 I used a modified Tracor 599H on WWVB with excellent > > results. It had a mechanical counter with 100 nsec, resolution. Noisy but > > perfect. Yes you have to take Ionosphere sunrise and sunset in to > > consideration and the hourly shift, but being a very early riser 4AM > > because of Europe no problem. Better than 2 E-11 per day and 4 E-14 per > > month. > > > > In the 90 ties with my FRK having temperature and aging control frequency > > was better than 1 E-12 all the time. > > > > Bert Kehren > > In a message dated 11/19/2018 9:58:39 PM Eastern Standard Time, > > [email protected] writes: > > > > HF propagation of WWV or WWVH is horrible compared to VLF propagationof > > WWVB at 60 kc. In this video the 5 mc WWV signal from Ft Collins,Colorado > > is being received in New Jersey. It was compared against astable 5mc > > crystal source. You can see a shift of a few cycles persecond over a few > > seconds. This is due to the movement up or down ofthe ionosphere at a > > substantial fraction of the speed of sound. > > In general terms, the coherence time of the ionosphere is single digit > seconds - that is, there's essentially no correlation between > propagation path at one time and the propagation path 10 seconds later. > > The "general length" of the path will be the same, but the details > different. > > The actual ionization in the ionosphere can best be described as moving > "clouds" there's a fair amount of spatial inhomogeneity. In the same > sense that milk reflects light from a multitude of little fat globules. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
