[time-nuts] WWV Doppler Shift

jimlux jimlux at earthlink.net
Tue Nov 20 16:04:56 UTC 2018


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.




Iunderstand that it can be as bad as a part per million short term 
atsome frequencies.  The 10 mc and 15 mc broadcasts may be better 
orworse at various times of day.
> I have spent many hours watching WWVB in the days when they had theold format.  It was good to a part per billion except just beforesunrise and just after sunset.  Then it degraded to either + or -5parts per billion for about 30 minutes.
> https://www.youtube.com/watch?v=nf9KWfS9QBs
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