[time-nuts] WWVB Measurements

[Lenny Story]

John,

I am hoping that those iono changes aren't going to be fast enough (< 10
sec) to affect my decoding.

-Lenny

On Sat, Mar 26, 2011 at 6:58 PM, J. Forster <jfor at quik.com> wrote:

> 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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>
>
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