[time-nuts] WWV Doppler Shift

Wed Nov 21 00:38:25 UTC 2018

A few years ago I did some measurements of WWV Doppler shift, measured by a 0.1 Hz resolution you get in an HP 3586C selective voltmeter.  It's not quite a phase record but does show the significant shifts that occur.

See https://www.febo.com/pages/hf_stability/

John
----

On Nov 20, 2018, 6:44 PM, at 6:44 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>Hi
>
>Having looked at WWV with a Carrier -> BFO -> audio card approach (and
>a radio 
>locked to an Rb standard …) you have dig a bit to find a situation that
>is
>beyond a tenth of a ppm. If you average over minutes  or tens of
>minutes (which 
>is exactly what you do with WWVB) the only time you get past 0.1 ppm is
>the 
>same sort of day/night propagation mode shift that drives WWVB nuts ….
>
>Bob
>
>> On Nov 20, 2018, at 5:35 PM, Donald E. Pauly <trojancowboy at gmail.com>
>wrote:
>> 
>> 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.
>> 
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