Not personally, but in the UK a company called Quarztlock made both MSF
(similar to WWVB) and 198kHz (a frequency-standard broadcast station) that
were popular frequency standards in labs.

They still exist but have replaced those products with Rubidium and GPS
based standards.
http://www.quartzlock.com/

On Sun, Apr 7, 2019 at 1:00 AM Wayne Holder wayne.holder@gmail.com wrote:

Hi

The gotcha with WWVB is correcting for the day / night ionosphere issues. Since they are not
100% predictable, it’s not a real easy problem to solve. Toss on top of the the ambiguous status
of WWV or WWVB ( = will it be there next year …. if so in what format ….????) there layers and
layers.

Best guess is that WWVB at a “one day” sort of range is a 10 ppt sort of thing. At the same observation
time, GPS is a < 0.1 ppt sort of thing. If the objective is accuracy … WWVB come in a bit far back ….

Bob

Wayne good read on the paper.
All of the spectracoms and such were rendered useless by the new BPSK
modulation. Though now that 5 years or so have passed not so new. Unless
the modulation is accounted for they can't track the carrier. There are
external modifications and other approaches that have been suggested. I
have design and tested numbers of them with a final approach using the
cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts
enough. A lot depends on your location and signal strength. Clearly taking
advantage of the new modulation for carrier prediction has advantage. But
the fact is even I am now spoiled by GPSDOs.
I also built a far simplere approach called a remodulator for simply
allowing the spectracoms to get time. They are nice displays. Not sure you
can get even those piece parts any longer.
Regards
Paul
WB8TSL

On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder wayne.holder@gmail.com wrote:

Hi Wayne,

Great to see you found my presentation!
The paper is available here:
https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf
I traveled to CO and met with NIST people there and gathered more data
then. We're planning to put out another paper soon (I'm finishing up my
bachelor's right now so I'm a bit preoccupied though).
I think LF timing is still very relevant in this day and age, and WWVB
still shows promise as a national timing source.

Let me know if you have any questions.
Best,
Kevin

On Sat, Apr 6, 2019 at 10:00 PM paul swed paulswedb@gmail.com wrote:

--
Kevin Croissant

Hi
After the passing of Clive Green HCD Research has taken over the Quartzlock
business mid 2016
Regards
Bernd DK1AG

(similar to WWVB) and 198kHz (a frequency-standard broadcast station) that
were popular frequency standards in labs.

based standards.

On Sun, Apr 7, 2019 at 1:00 AM Wayne Holder wayne.holder@gmail.com wrote:

time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Kevin, thanks for the link to the paper.  I'd like to know more about how
correlation works and how you were able to use to to sync with the WWVB
bitstream.  From what I read in your paper, I'm guessing that the "local"
code you use for correlation is generated by prediction once the receiver
has locked on the broadcast code and these two bit streams are then
"compared" in some way via multiplication...  But, I don't really
understand how this is done at a practical level as it would seem that his
would require multiple passes over the code with some type of sliding time
offset that advances with each pass? Or, are there simpler techniques?  Can
you suggest a reference where I can learn more?

BTW, for everyone else following the WWW/WWVB/WWVH defunding saga, a post
on this web page:

http://cqnewsroom.blogspot.com

claims that "Congress has restored full funding for WWV, WWVB and WWVH,
despite a budget proposal from the National Institute of Standards and
Technology to shut down the three standard time and frequency radio
stations. The Consolidated Appropriations Act of 2019 included some $725
million for NIST's Scientific and Technical Research and Services (STRS),
the budget category that includes the stations' funding, according to NIST
Public Affairs Director Gail Porter. The conference report accompanying the
budget bill notes that "(t)he agreement rejects the proposed terminations
and reductions for all STRS programs" and includes "not less than fiscal
year 2018 funding" for several services, including "Time and Fundamental
Measurement Dissemination."

The article then adds: "With the shutdown threat ended, preparations
continue for marking WWV's centennial this fall. According to the ARRL
Letter, the Northern Colorado Amateur Radio Club will be operating a
special event station from the WWV transmitter site from September 28
through October 2, using the callsign WW0WWV."

Wayne

Wayne

Wayne

On Sat, Apr 6, 2019 at 9:00 PM Kevin Croissant kevin@kevincroissant.com
wrote:

Wayne, there was a superb 2015 QEX article by KD2BD on his WWVB disciplined
frequency standard. Full article is online here:
http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf

As a frequency standard I have no major disagreement with the PTTI article.
But the 100 microsecond number they give for absolute time transfer seems
to be based entirely on propagation characteristics and ignores the
difficulty I've always had in resolving the mushy edge of the timecode
pulses. 100 microseconds implies a system bandwidth of 10kHz, which is
pointless because the transmitter antenna bandwidth has to be quite narrow

• hundreds of Hz if not less.

Tim N3QE

On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder wayne.holder@gmail.com wrote:

On 4/7/19 4:30 AM, Wayne Holder wrote:

One thing that helps is that you know the structure and content of the
bitstream after the fact - that is, the SNR needed to decode the bits is
lower than that to recover precision timing.  So you take the "known"
bitstream and do a cross correlation against the received signal.

pseudocode for the cross correlation is something like this:

for lag=0:N
sum=0
for i=0:M-1
sum = sum + input[i]*reference[i+lag]
end for
crosscorrel[lag] = sum/M
end for

this is a O(NM) number of operations, so most folks use a technique
using FFTs: FFT each of them, multiply term by term, then inverse FFT
back.  That's O(3M*log2(M) +M operations)

You'll get something that has a peak in the middle, which corresponds to
the point of "maximum alignment" between the two data streams.

There's all sorts of things one can do to get "sub sample" resolution -
essentially by interpolating.  Zero padding the data set before FFTing
is one way.

The other thing that might save computational burden is that you don't
need to try ALL possible time lags - you have an estimate, and so you
can slide around just that

jimlux,
thanks for the info cross correlation.  That's sort of how i imagined it
should work, but I wasn't sure.  I guess it really helps that we live in
the age of fast computation.

Wayne

On Sun, Apr 7, 2019 at 10:00 AM jimlux jimlux@earthlink.net wrote: