[time-nuts] WWVB Chronverter update progress

paul swed paulswedb at gmail.com
Sun Aug 26 17:52:35 EDT 2018


Looks like the signal has to be with in 1 hz. I new it was tight.
Need a bit more experimentation across the several receivers though they
all use the same approach with a sharp Xtal filter.


On Sat, Aug 25, 2018 at 8:24 PM, paul swed <paulswedb at gmail.com> wrote:

> 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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