[time-nuts] wwvb gps d-psk-r details

[paul swed]

This absolutely requires GPS all of the time.
In recalculates the entire 1 minute sentence every minute at 00 in the
first 200ms.
But that was a choice. The actual clock could run till you pull the plug.
I choice the get it done approach.

What is key is an accurate stable 1 PPS.
All of that said it proves the message generation method. That appears
simple and as I actually learned not that simple.

So it does get back to the interesting next steps. Accurately determining
the BPSK transition then adjusting a local 1 PPS to stay in sync. The
message tells you what to expect and pretty much when.

Another part of the independent answer is that since the time is in minutes
from 2000 then a comparison of the local minute to the wwvb minute is
helpful in aligning a local clock. It goes on and on with possible answers.

I have used this unit with a local 60 KHz and a scope to accurately check
the incoming BPSK stream and catch my coding errors.

Regards
Paul
WB8TSL

On Fri, Sep 25, 2015 at 9:15 AM, John Ackermann N8UR <jra at febo.com> wrote:

> I may be remembering incorrectly, but I thought that you only need the GPS
> for initial sync; after that shouldn't the processor be able to maintain
> the sequence without new GPS input, so long as the timer clock doesn't
> drift too badly?  From a known starting point, the modulation pattern
> should be predictable into the future.
>
> John
> ----
>
>
> On 9/24/2015 5:11 PM, Charles Steinmetz wrote:
>
>> Paul wrote:
>>
>> Here is the detailed document on the wwvb d-psk-r.
>>>
>>
>> Interesting solution, and a good study in persistence.
>> Congratulations!  But I thought the main point of having a working WWVB
>> receiver was as a backup if GPS fails (or for use in circumstances where
>> WWVB reception is possible but not GPS reception).  If GPS is working,
>> and you have a GPS rx/GPSDO, what is the point of having a time and/or
>> frequency source that relies on GPS but only has the precision of WWVB?
>> And what good is the predictive de-psk-r when GPS is not working?
>>
>> [Yes, I get that if one runs a museum it's nice to have working exhibits
>> even if they are simulated, and it's no big deal if the exhibits don't
>> work from time to time.  But the curator's solution doesn't seem to
>> solve the time-nuts' real problem.]
>>
>> I hasten to add that I don't really care one way or the other about GPS
>> alternatives, particularly alternatives with the relative imprecision of
>> WWVB over time scales shorter than geological.  Personally, I presume
>> that if there is ever a persistent, system-wide GPS failure it will be
>> due to a natural or man-made catastrophe of earthshaking proportions
>> (literally) and there will be many, more urgent concerns than time-nuts'
>> experiments.  But others have expressed concern over having just one
>> time and frequency standard available.  For them, isn't a fully
>> independent solution that does not rely on GPS required?
>>
>> Again, congratulations on bringing this idea to fruition.
>>
>> Best regards,
>>
>> Charles
>>
>>
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