[time-nuts] True to there word. - Fancy WWVB

Bob Camp lists at cq.nu
Tue Feb 9 02:34:21 UTC 2010


Hi

I suspect there is more to the compensation process than just time of day. At some point it would get a bit crazy to collect all the data. It would be interesting to look into though. 

I'm by no means suggesting that WWVB would replace Loran. My *guess* is that it would be competitive with skywave Loran-C.  I've locked an Austron 2100 to the European chains. It can indeed be done. The only real issue is how good the result is (or isn't).

Bob


On Feb 8, 2010, at 8:49 PM, J. Forster wrote:

> I was using a HP 105B and 117A before the Austron 2100F and still have
> them. From what I remember, the diurnal shift was not repeatable.
> 
> By looking at an output from the 117A and syncing the 'scope to the 105B,
> I could assess the quality of the signal pretty well. Sometimes it was
> stable, sometimes it was jittering all over the place by a cycle or more.
> 
> Bottom line is, IMO, WWVB is no substitute for LORAN.
> 
> I'm still hoping that the european chains will be usable.
> 
> YMMV,
> 
> -John
> 
> ================
> 
> 
>> Hi
>> 
>> Yes indeed, you need to be sure you don't get a cycle slip. That's not
>> trivial when the signal goes to zero while moving phase.
>> 
>> There I think you need to depend on something like a reasonable OCXO and a
>> long time constant loop. That brings in other problems. I assume that you
>> are going to have to train your loop to "expect" the ID shifts and time
>> markers. Again, they are predictable. It's just software ....
>> 
>> More or less:
>> 
>> Take all of the things you can compute about the signal and feed them in.
>> Lock the "computed" signal against the received signal. Way less complex
>> than what they do with GPS. Since it's all *very* slow, a beater PC can
>> easily keep up with all the adjustment math.
>> 
>> Bob
>> 
>> 
>> On Feb 8, 2010, at 8:28 PM, J. Forster wrote:
>> 
>>> If you track for a day, and draw a straight line throught the diurnal
>>> shift, you can easily see a frequency drift of 45 degrees. That's 1/8
>>> cycle of 60 KHz or about 2 uS. So 2x 10 E-6 out of 10 E5, so you can see
>>> 2
>>> x 10 E-11 in a day.
>>> 
>>> ASSUMING the lock does not break.
>>> 
>>> -John
>>> 
>>> ===================
>>> 
>>> 
>>> 
>>>> Hi
>>>> 
>>>> People rarely want to use WWVB mobile. The location of the transmitter
>>>> and
>>>> receiver can be looked up on a map. The time of sunrise at both
>>>> locations
>>>> should be something that could be calculated.
>>>> 
>>>> Assuming you are willing to put up with all of that, you should be able
>>>> to
>>>> do a first order correction on the shifts. The question obviously is -
>>>> just how good would the net result be? Is it a 5:1 sort of thing or do
>>>> you
>>>> get a couple of orders of magnitude?
>>>> 
>>>> Bob
>>>> 
>>>> On Feb 8, 2010, at 6:40 PM, J. Forster wrote:
>>>> 
>>>>> Yes, but WWVB is a PITA to use (because of the diurnal shifts)
>>>>> compared
>>>>> to
>>>>> LORAN.
>>>>> 
>>>>> -John
>>>>> 
>>>>> ===============
>>>>> 
>>>>> 
>>>>>> Hi
>>>>>> 
>>>>>> WWVB is pretty safe. When they do a cost/benefit thing on these
>>>>>> services,
>>>>>> they take a look at how many taxpayers are using the service as
>>>>>> intended.
>>>>>> The "mission" of WWWVB is to put out time signals. There are a *lot*
>>>>>> of
>>>>>> taxpayers with WWVB "atomic clocks" on their walls.
>>>>>> 
>>>>>> Bob
>>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
>>>>>> On
>>>>>> Behalf Of Don Henderickx
>>>>>> Sent: Monday, February 08, 2010 4:07 PM
>>>>>> To: Discussion of precise time and frequency measurement
>>>>>> Subject: [time-nuts] True to there word.
>>>>>> 
>>>>>> The lights went out (actually red) on my Austron 2100 r this morning.
>>>>>> (whats  next WWVB ?)
>>>>>> Don H
>>>>>> 
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>>>>>> 
>>>>>> 
>>>>>> 
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>>>>>> 
>>>>> 
>>>>> 
>>>>> 
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