[time-nuts] WWV and legal issues

Bob Martin aphid1 at comcast.net
Sat Sep 1 14:18:07 EDT 2018


Here is an interesting paper on using fiber:

https://pdfs.semanticscholar.org/a37e/04164c01a6bfea2154c8f0dd97f49d1673b0.pdf

I believe it used some of the gear that is(was) used in the GPS 
ground stations around the world.

Bob Martin

On 9/1/2018 3:29 AM, Magnus Danielson wrote:
> Hi,
> 
> It was very telling when I crashed a research group into the reality of
> phase/time transfer over fiber compared to frequency transfer. Armed
> with a whiteboard and pens, I derived the forumulas and showed how they
> worked and not worked. It's a completely different ball-game and their
> "known tricks" ain't doing nothing good as it comes to time.
> 
> I had to figure much of this out myself as I did nation-wide system
> design to achieve the goal. It's a combination of many skills that goes
> into designing the full system from scratch and make it fit together.
> It's not hard stuff, it's just many details one needs to get right.
> 
> Oh the fun.
> 
> Cheers,
> Magnus
> 
> On 08/31/2018 05:15 PM, Bob kb8tq wrote:
>> Hi
>>
>> That works fine if you are doing things manual to check a local standard. If you are trying to
>> disipline a few thousand cell towers 24 hours a day … not so much. It also works for
>> checking frequency. What modern systems need is time. That gets you into a whole
>> world of resolving and identifying individual edges. The WWVB signal really was never
>> set up for this. Loran-C is an example of a signal that was designed to identify a specific
>> edge.
>>
>> Bob
>>
>>> On Aug 31, 2018, at 10:30 AM, Martin VE3OAT <ve3oat at storm.ca> wrote:
>>>
>>> But the diurnal phase shifts at VLF are predictable and largely repeatable.  Ignore the phase at night and use only the phase records during the day when an all-daylight propagation path exists.  You might have to "correct" the absolute phase reading by some multiple of the RF period, but with a low rate of local standard oscillator drift, this is a simple matter of arithmetic. Back in the day, I managed Sulzer crystal oscillators at 5 field sites from my office and could maintain phase continuity for weeks at a time, until we had to diddle the dial on one or several of them to correct for crystal aging.  Then it was just more arithmetic again.  Several of the oscillators had such low drift rates that all I needed was one daily phase reading from the VLF phase tracking receiver (Tracor 599Js) at those sites to know the frequency of the Sulzers there.
>>>
>>> ... Martin     VE3OAT
>>>
>>> On Thu, 30 Aug 2018 12:27:12 -0400
>>> Bob kb8tq<kb8tq at n1k.org>  wrote:
>>>
>>>> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully stable signal. As soon as
>>>> that signal hits the real world things start to degrade. Propagation between transmit and receive sites
>>>> is a big deal, even at 60 KHz. On top of that, there is a*lot*  of manmade noise at 60 KHz. The receive
>>>> signal to noise will never be as good as you might like it to be ?.
>>>
>>>> I don't know about WWVB, but for DCF77 it's known that sunrise/sunset
>>>> causes a phase shift of several 100?s at even moderate distances
>>>> (like ~500km). Unfortunately I don't have any measurements at hand.
>>>> 				Attila Kinali
>>>
>>>
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