[time-nuts] WWV Doppler Shift

Donald E. Pauly trojancowboy at gmail.com
Tue Nov 20 22:35:51 UTC 2018


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 <jimlux at earthlink.net> 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, trojancowboy at gmail.com 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.




More information about the Time-nuts_lists.febo.com mailing list