[time-nuts] WWVB Signal Generator

paul swed paulswedb at gmail.com
Thu Aug 30 11:52:18 EDT 2018


Wayne as I work through the chronverter I do know the good phase tracking
clocks really demand on frequency behavior. As I measured its +/- .6 Hz at
60 KHz. I believe the cheapy wall clocks are a bit wider, but not sure as
they are hard to actually measure. They do use a small tuning fork crystal
and from experience these are sharp. When I experimented with them they
were maybe 5 Hz. Indeed the Chinese website had 25 X 60 KHz crystals for
maybe $2.
With respect to the antenna. My thinking is a loopstick resonated on 60 KHz
and most likely driving it push pull or single ended. Thats 1 transistor if
single ended as common collector if I had to guess. The reason is the
micros put out a fair level of signal so its a case of upping current into
the antenna. But it really will be a bit of experimenting.
I did look at your code and that was so nice it opened up straight into the
arduino IDE.
Regards
Paul
WB8TSL

On Thu, Aug 30, 2018 at 5:12 AM, Wayne Holder <wayne.holder at gmail.com>
wrote:

> For anyone trying out my ATTiny85 code, I've done some additional tests and
> find that placement of the antenna near the clock is very finicky and, so
> far, the only way to get a reliable decode of the time in the clock is by
> using a scope to monitor the demodulated output and then moving the antenna
> around until the demodulated signal lines up cleanly with modulated carrier
> and there are no intra bit glitches.  This can take a bit of patience, so
> clearly a better solution needs to be found.  I've found that any type of
> glitch in the demodulated signal seems to prevent the clock chip from
> decoding the time.
>
> It's possible the difficultly with locking onto my simulated WWVB signal
> may be partially due to the design of the clock (from my location it's
> never been able to to lock onto the real WWVB signal), but I have no
> reference to compare it against so, for now, I have conclude that the
> PWM-based modulation scheme my code uses may also be suboptimal for this
> application.  To make testing even more frustrating, the BALDR clock I'm
> using will only look for a signal for about 6 minutes before it goes to
> sleep and I have to then power cycle the clock to get it to listen again.
>
> So, keep this in mind if you're going to try and replicate my results.
>
> Wayne
>
> On Wed, Aug 29, 2018 at 6:03 PM Wayne Holder <wayne.holder at gmail.com>
> wrote:
>
> > For those that have asked for my to publish the source code for my
> > ATTiny85-based WWVB simulator, I have put up a somewhat hurriedly written
> > page on my google site at:
> >
> >   https://sites.google.com/site/wayneholder/controlling-time
> >
> > that describes a bit about how the code works, how to compile it using
> the
> > Arduino IDE, how I tested it, some issues I have observed in testing it
> > and, at the bottom of the page, a downloadable zip file that contains the
> > complete source code.
> >
> > Note: as mentioned at the top of this page, this is currently a work in
> > process, so I'm not yet going to link the article to my main website
> page,
> > so you'll need to link in this post to find it.  Also, as draft, I'm
> going
> > to continue to revise the page until I feel the project is complete
> enough
> > to publish.  That means the source code zip file is going to potentially
> > change from time to time, too.
> >
> > Wayne
> >
> > On Wed, Aug 29, 2018 at 1:35 AM Wayne Holder <wayne.holder at gmail.com>
> > wrote:
> >
> >> As a follow up, I now have a simple WWVB simulator written in C that's
> >> now running an an ATTiny85 using nothing more than the internal, 8
> >> mHz oscillator and about a 6 inch length of wire connected to one of the
> >> pins as an antenna.  It generates an approximate 60 kHz signal using
> PWM on
> >> timer 1.  I tweaked the timer value a bit to correct for some variance
> in
> >> the internal oscillator, but I' not even sure that was necessary, as my
> >> target is just a  BALDR Model B0114ST, consumer grade "Atomic" clock.
> >> Modulation is done by varying the duty cycle of the PWM to approximate
> the
> >> -17 dBr drop on the carrier.  But, again, I don't think this value is
> >> critical with a consumer clock chip.  I tapped the demodulated output
> >> inside the clock and displayed it on my scope along with the generated
> >> signal and I got good, steady demodulation with the wire antenna just
> >> placed near clock.  The next step is to connect up a GPS module and add
> >> code to use it to set the time.  I'm also going to change the code to
> use
> >> the PPS signal from the GPS to drive the output timing rather than the
> test
> >> code I have now that uses timer 0 to generate the PPS interrupt.  I'm
> happy
> >> to share details if anyone is interested.
> >>
> >> Wayne
> >>
> >>
> >>
> >> On Sun, Aug 26, 2018 at 2:51 PM, paul swed <paulswedb at gmail.com> wrote:
> >>
> >>> That would be a great neighbor to have but I can tell you around here
> its
> >>> the phone. Not to concerned about someone putting up a wwvb
> replacement.
> >>> And I can always up the power. Chickle.
> >>> Regards
> >>> Paul
> >>>
> >>> On Sun, Aug 26, 2018 at 2:34 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> >>>
> >>> > Hi
> >>> >
> >>> > The gotcha is if you have neighbors two or three doors away that
> *also*
> >>> > put up one of
> >>> > these devices. You then have a real problem with the neighbor(s) in
> the
> >>> > middle. The
> >>> > wavelength is long enough that Raleigh issues won’t get you. You
> still
> >>> > have the two
> >>> > signals ( at slightly different frequencies) beating against each
> >>> other.
> >>> > The result is
> >>> > going to show up as who knows what to this or that receiver. With a
> >>> > precision receiver,
> >>> > you might even have issues from the guy two houses away …...
> >>> >
> >>> > Bob
> >>> >
> >>> > > On Aug 26, 2018, at 1:08 PM, paul swed <paulswedb at gmail.com>
> wrote:
> >>> > >
> >>> > > Agree with the conversation. With respect to neighbors when the day
> >>> comes
> >>> > > they may ask you to boost your signal. :-)
> >>> > > Granted maybe the day won't come but at least having your local
> >>> clocks
> >>> > work
> >>> > > is nice.
> >>> > > Regards
> >>> > > Paul
> >>> > > WB8TSL
> >>> > >
> >>> > > On Sat, Aug 25, 2018 at 10:29 PM, Dana Whitlow <
> >>> k8yumdoober at gmail.com>
> >>> > > wrote:
> >>> > >
> >>> > >> With the watch being physically close to the faux WWVB
> >>> "transmitter",
> >>> > one
> >>> > >> is in
> >>> > >> the so-called "near field" regime, where the field strength (V/m)
> >>> falls
> >>> > as
> >>> > >> the inverse
> >>> > >> cube of the distance.  If one is putting the watch, say, within a
> >>> few
> >>> > >> inches of the
> >>> > >> transmitter, reliable reception should be available yet the signal
> >>> > should
> >>> > >> be literally
> >>> > >> undetectable by any practical receiving device more than a few
> feet
> >>> > away.
> >>> > >> Hence,
> >>> > >> meeting the FCC field strength limit should be trivial.if the
> >>> device is
> >>> > >> used as pictured.
> >>> > >> However, if one cranks up the power enough to reliably cover one's
> >>> > entire
> >>> > >> house,
> >>> > >> then there might be a problem depending how close the nearest
> >>> neighbor
> >>> > >> lives,
> >>> > >> even at levels well within the FCC limit he quotes.
> >>> > >>
> >>> > >> Taking the near field relationship in hand, 40 uV/m at 300m would
> >>> > translate
> >>> > >> into
> >>> > >> a whopping 0.135 V/m at 20 meters range, more than enough to feed
> >>> most
> >>> > >> peoples'
> >>> > >> entire house.  So the pragmatic issue would again be- neighbors.
> >>> On the
> >>> > >> other
> >>> > >> hand, most of them would never be aware of the local signal as
> long
> >>> as
> >>> > they
> >>> > >> get good
> >>> > >> time settings, unless they live close enough to Ft. Collins for
> the
> >>> two
> >>> > >> signals to
> >>> > >> contend with each other.
> >>> > >>
> >>> > >> It looks to me like the ferrite rod antenna is considerable
> >>> overkill.
> >>> > Even
> >>> > >> with no
> >>> > >> purposeful antenna I'd expect leakage to yield sufficient signal
> >>> for at
> >>> > >> least a few
> >>> > >> inches.
> >>> > >>
> >>> > >> Dana
> >>> > >>
> >>> > >>
> >>> > >> On Sat, Aug 25, 2018 at 8:11 PM Wayne Holder <
> >>> wayne.holder at gmail.com>
> >>> > >> wrote:
> >>> > >>
> >>> > >>> This guy has what looks like a well thought out design using a
> >>> > Sirf-Based
> >>> > >>> GPS and ATTiny44A chip to generate a signal to update his watch:
> >>> > >>>
> >>> > >>>  https://www.anishathalye.com/2016/12/26/micro-wwvb/
> >>> > >>>
> >>> > >>> Unfortunately, he doesn't seem to have published a schematic or
> his
> >>> > >> source
> >>> > >>> code.  But, he covers enough detail that I think it wouldn't be
> too
> >>> > hard
> >>> > >> to
> >>> > >>> replicate what he's done.  Or, perhaps he would disclose these
> >>> details
> >>> > if
> >>> > >>> contacted.
> >>> > >>>
> >>> > >>> Wayne
> >>> > >>>
> >>> > >>> On Sat, Aug 25, 2018 at 4:33 AM, D. Resor <
> organlists at pacbell.net>
> >>> > >> wrote:
> >>> > >>>
> >>> > >>>> I thought I would search in a different way for a WWVB signal
> >>> > generator
> >>> > >>>> design.  I found this item.  While the designer explains it
> isn't
> >>> as
> >>> > >>>> accurate as WWVB it may be another starting point.
> >>> > >>>>
> >>> > >>>> http://www.tauntek.com/wwvbgen-low-cost-wwvb-time-
> >>> > signal-generator.htm
> >>> > >>>>
> >>> > >>>>
> >>> > >>>>
> >>> > >>>> Donald R. Resor Jr. T. W. & T. C. Svc. Co.
> >>> > >>>> http://hammondorganservice.com
> >>> > >>>> Hammond USA warranty service
> >>> > >>>> "Most people don't have a sense of humor. They think they do,
> but
> >>> they
> >>> > >>>> don't." --Jonathan Winters
> >>> > >>>>
> >>> > >>>> _______________________________________________
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