[time-nuts] WWVB Chronverter update progress

paul swed paulswedb at gmail.com
Sat Aug 25 20:24:12 EDT 2018


My mistake the chronverter uses a pic 12f1840.

On Sat, Aug 25, 2018 at 8:23 PM, paul swed <paulswedb at gmail.com> wrote:

> Have to look at what oscillators and crystals I have then a divide.
> Thats old style and most likely the junk box has everything.
> Have to look in my box of tricks as I built several chains for the
> de-psk-er experiments.
> Have to agree on the micro the chronverter uses a pIC 12F64 as I recall
> and it has quite a nice set of dividers in it. Just not an external crystal
> input so a better oscillator can be used. Getting lazy these days.
> I have some number of tcxos from a company called vectron. Several cards
> of each. Can't imagine how I came by those.
> :-) Believe the lowest freq was 12 MHz.
> Regards
> Paul.
>
>
> On Sat, Aug 25, 2018 at 8:07 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>
>> Hi
>>
>> A pretty simple modest Q tuned circuit on the output of a gate will turn
>> the square wave
>> into a sine. Not much to it since there are a lot of power supply
>> components out there that
>> work fine at 60 KHz. In order to get a stable 60KHz, a divider is the way
>> to go. I’d probably
>> use one that’s built into an MCU as part of a timer or something similar.
>>
>> Bob
>>
>> > On Aug 25, 2018, at 7:00 PM, paul swed <paulswedb at gmail.com> wrote:
>> >
>> > 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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>> >>
>> >>
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