[time-nuts] WWV and legal issues
scmcgrath at gmail.com
Sat Sep 1 10:00:39 EDT 2018
There was a paper published when NASA did something similar for LC39 and the VAB. Anyone have a copy because the link i have is dead.
As I recall it was some trick and compensating for thermal effects on the fiber itself was a large part of the effort.
On Sep 1, 2018, at 5:29 AM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
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.
> On 08/31/2018 05:15 PM, Bob kb8tq wrote:
> 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
>> 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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