[time-nuts] WWVB Chronverter update progress

Bob kb8tq kb8tq at n1k.org
Sun Aug 26 18:33:50 EDT 2018


Hi

Well …. 1Hz at 60KHz is …. errr … (off to Google Calc …) …. 16.67 ppm. That’s 
a pretty major lock range for a TCXO. It’s likely > 10X what an OCXO will do. What the
bare crystal in a watch will do … who knows. 

Bob

> On Aug 26, 2018, at 5:52 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> 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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>>> 
>> 
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