[time-nuts] WWVB Chronverter update progress

paul swed paulswedb at gmail.com
Sat Aug 25 19:00:23 EDT 2018


Bob The generator sig is 60 Khz sinewave.but as a I build up a divider
chain and such your idea makes great sense.
Then filter to 60 KHz.
But I see the issue with the Chronverter carrier its 120-150 Hz high.
Bounces around a fair amount.
There could be a secondary issue in that the carrier may not actually be
phase stable.
It really doesn't matter as for the Truetimes and Spectracoms its simply
not good enough.
I still need to try the cheapy clocks as that is what it was intended for.
Not throwing stones as so much of what it does saves me a bunch of coding
and doing exactly what Dave did.
Regards
Paul
WB8TSL

On Sat, Aug 25, 2018 at 5:31 PM, Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> You can do the 14 db deep modulation with a tristate gate and a pair of
> resistors.
> Ground the input and feed the “modulation” signal to the tristate control.
>
> Bob
>
> > On Aug 25, 2018, at 4:35 PM, paul swed <paulswedb at gmail.com> wrote:
> >
> > From the earlier threads OOK modulation does not work for high end clocks
> > like spectracoms and truetimes. Have not tried it on the cheapy clocks
> yet.
> >
> > I added an external modulator. A dg419 analog switch and then with a few
> > resistors added DC offset and anttenuation so that the carrier drops by
> -14
> > db per the wwvb spec. The logic control is driven from the chronverter
> and
> > it totally works. Spectracom Netclock 2 locked up in the normal time.
> > There are far better modern single supply analog gates that will work.
> Just
> > did not have any.
> >
> > The 60 KHz carrier is supplied by a fluke 6060 generator. This eliminates
> > any chance of being off frequency and is not the long term answer.
> >
> > The chronverter actually uses a dallas semiconductor clock chip thats
> > reasonably accurate.(dangerous to say on time-nuts) So that even if you
> do
> > not add the GPS receiver it will run quite some time correctly after
> > setting the time.
> >
> > Chronverter draws 6 ma from a 5 V supply. I always like low power.
> >
> > All in all a very nice answer to what do we do if WWVB goes away.
> > As mentioned it handles timezones and DST and you can change DST if those
> > silly politicians screw with it again.
> >
> > Speculation
> > The chronverter actually puts out carriers for the popular LF stations
> > along with the time codes for them.
> >
> > Though the modulator allows quality clocks to lock I speculate the
> > frequency from the chronverter is not tight enough. All of these clocks
> > have very sharp crystal filters in them. 10 Hz. Plan to measure the
> output
> > of the chronverter see what the 60 KHz is actually at. Though listening
> on
> > a HP3586 receiver it appears pretty close to frequency maybe its just not
> > good enough. Or the fact is OOK modulation does not work because it gaps
> > the PLL in these clocks.
> >
> > Next steps
> >
> >   - Determine and lay to rest the OOK/need for external modulator.
> >   - Power amplifier and loopstick transmitting antenna staying at or
> below
> >   30uv at 30 meters.
> >   - Integrate a neo6 GPS receiver in. (Seriously easy)
> >   -
> >   - Box it up.
> >
> > Have my eye on one of the Truetime DC468 units and the classy panelplex
> > display.
> >
> > Hope this helps those of you concerned with what to do should WWVB go
> away.
> > Regards
> > Paul
> > WB8TSL
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