[time-nuts] WWVB Signal Generator

paul swed paulswedb at gmail.com
Wed Aug 29 11:32:48 EDT 2018


Wayne always fun to see what others are doing and to learn.
I would imagine the programs pretty small and could be attached here.
How will you handle DST? Its a bit messy as a recent thread detailed.
Plus the fact that god knows why politicians like to screw with it.
Regards
Paul
WB8TSL

On Wed, Aug 29, 2018 at 4:35 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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