[time-nuts] WWVB Measurements

[J. Forster]

I used to use WWVB before LORAN came into my life (HP 117A). It was a
PITA. On the east coast (Boston) the signal was erratic and often became
untrackable. About half the time, the receiver lost lock at least once per
24 hours, making WWVB an unreliable standard. You really need continuous 
tracking over several days to be sure of your local standards' aging rate.

Furthermore, the diurnal phase shifts between day and night are a PITA.

Boy, I really do miss LORAN.

-John

===============


> Lenny,
>
> You are ahead of me by many months.  I'm building a WWVB receiver
> also.  Actually I expect I will need to build several before I get
> 24x7 coverage.  My breadboard works only at night in the So.
> California area.   My plan is to place the entire receiver, antenna
> and all on a mast far from the house and use an RS422 serial line to
> send the data back to a computer indoors.
>
> Do you intend to publish your work?   I'd be most interested in how
> you decode the signal.   I'm conflicted between two approaches (1) To
> declare the signal "invalid" if there is any error at all or (2) to
> try and extract as much signal out of the noise as I can.  I may do
> the latter and then have some kind of quality indicator.    The WWV
> audio decoder built into the NTP reference implementation can extract
> time code from what sounds like white noise and static to the human
> ear using sophisticated DSP.  My first receiver will use #1.
>
> About measuring the PPS.If you had a nice HP Universal counter with a
> computer interface that would be best.  You put the PPS from a good
> GPS on one channel and the PPS from WWVB on the other.   Lacking that
> and if you only need to get down to uS level you can use two serial
> orts in a Linux box and use PPS line disciplin on each oert the kernal
> will time stamp the PPS when they happen and software can read and log
> the time stamps. Use the command  "ldattach pps <device>" for each
> serial port.  Good to about 1 uSwhich for WWVB might be enough
>
>
>
> On Sat, Mar 26, 2011 at 1:26 PM, Lenny Story <lenny at codematic.com> wrote:
>> Greetings All,
>>
>> This is my first post to this board.
>>
>> I've completed the first run of a WWVB receiver board and Antenna
>> (custom
>> wound quad). Its an 8051 microcontroller, with a serial port really, but
>> it
>> can decode the signal accurately pretty much all day long. (I'm just
>> north
>> of boston, MA).
>>
>> I'm wanting to evaluate its performance, my guess is i'll have to
>> produce a
>> plot of its PPS. In reading the LeapSecond.com site (awesome btw), the
>> "Allen Deviation" is used.  As this is my first technical, experience in
>> this area, is there a resource or method that is preferred by those who
>> know
>> this technology ?
>>
>> The code reports the time delta between each detected second. If i log
>> the
>> PPS deltas for an entire day (or week) of detected signal, is that
>> enough
>> data to start figuring out how to do the "Allen Deviation" calculations
>> ?
>>
>> Any resources can you recommend to figuring out the graphs i need to
>> produce
>> ?
>>
>> Thanks in advance for your help !
>> -Lenny Story
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>
>
>
> --
> =====
> Chris Albertson
> Redondo Beach, California
>
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