[time-nuts] WWVB Measurements

[Chris Albertson]

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