[time-nuts] WWVB Chronverter update progress

[Bob kb8tq]

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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