[time-nuts] WWVB Chronverter update progress

Bob kb8tq kb8tq at n1k.org
Wed Aug 29 09:16:16 EDT 2018


HI

If you are feeding “Time Nuts” gear, a fancy filter on the output of the 
WWVB gizmo may be an issue. Temperature impacts the value of the
components and that value change impacts the phase of the signal….

Bob

> On Aug 28, 2018, at 9:33 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> LPF filter added 2.2mH choke to a .0022uf cap 1K R pretty simple and
> anttenuators and isolation to drive up to 4 receivers.
> Have not looked at the power amp and loops stick antenna yet. But it really
> is time for GPS a neo.
> Looking very good.
> 
> On Tue, Aug 28, 2018 at 7:29 PM, paul swed <paulswedb at gmail.com> wrote:
> 
>> Ed appreciate the details but no intent to generally run a GPSDO in fact
>> the 5 V @ 50 ma is a serious power pig. The chronverter draws 5 ma. Clearly
>> the TTL is a heater. Chuckle. I do want to drive the chronverter with GPS
>> as its designed for.
>> Whats pretty interesting is you can adjust its offset. I just jammed time
>> into it several days and its been fairly good with power ups and down. Its
>> impressive. Though not in an ultimate time-nuts way.
>> GPS just assures it is accurate. But there is a lot of flexibility.
>> Main goal of this whole project is to replace wwvb if it goes away. If it
>> does the project doesn't even have to run 24/7. Fire up at 10 pm to 3 am
>> and power down. Thats enough to set my wall clocks for a day. Its just nice
>> to know it can also set the spectracoms and Truetimes. Icing on the cake.
>> I am impressed with what Dave did with the 8 pin pic. He has all of the LF
>> time signals in there. (No wwvb BPSK though) DSTs settings, zone offsets,
>> half zones, etc.
>> Just looking at low pass filters for the 60 KHz ttl out right now. Simple
>> LR or RC. Since this particular output feeds coax to the quality receivers
>> I don't need to be that careful. Its working great without any filtering.
>> Reality if it draws little power I will let it run 24/7 but then you just
>> have to stick a display on at that point.
>> Regards
>> Paul
>> 
>> On Tue, Aug 28, 2018 at 7:11 PM, ed breya <eb at telight.com> wrote:
>> 
>>> Paul,
>>> If you're going to reference it from a GPSDO anyway, why worry about a
>>> TCXO reference (and power too, for that matter). You can easily make the 60
>>> kHz from the 10 MHz.
>>> 
>>> For example, with two 74HC390s and a 74HC86 you can make 50 kHz and 10
>>> kHz and mix them with one EXOR section of the '86 to have 60 kHz available.
>>> Some fairly simple bandpass filtering should select and clean it up
>>> sufficiently. Two other sections of the '86 can be set up as inverters and
>>> self-biased as amplifiers - one to convert the 10 MHz sine reference to
>>> logic, and the other from the filter output to logic, if needed. And, you'd
>>> still have a divide by 5 and an EXOR left over to fool around with.
>>> 
>>> The same parts and process can be done at a higher frequency and then
>>> divided down afterward. (5+1) MHz/100, and (500+100) kHz/10 would work too.
>>> It depends on what frequency you prefer for the BPF. If you go high at 6
>>> MHz, you then have the option to make a crystal filter from readily
>>> available parts.
>>> 
>>> Going the high way also provides for higher logic frequencies that are
>>> more or less in sync, in case you want to do any I-Q modulation type stuff
>>> - you can even use synchronous counters instead, to really make sure.
>>> 
>>> Overall, I think I'd recommend going at 5+1= 6 MHz, filtering with 6 MHz
>>> crystals, then dividing down to 60 kHz, with 2f and 4f clocks available for
>>> I-Q use. I sketched out a quickie circuit that's quite simple and I think
>>> would do. It would take two HC390s for the dividing, as before. Each HC390
>>> is two divide by 10 counters, including a 1/2 and 1/5 in each, usable
>>> separately. So, with two parts, there are four 1/5s and four 1/2s available.
>>> 
>>> Here's a verbal process description: 10 MHz sine convert to logic with
>>> HC86, 10 MHz/2=5, 10 MHz/10=1 with first HC390, add 5+1=6 with EXOR, BPF 6
>>> MHz, convert to logic with HC86, 6 Mhz/25=240 kHz=4f, 240/2=120 kHz=2f,
>>> 120/2=60 kHz=f, with second HC390.
>>> 
>>> Ed
>>> 
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>>> 
>> 
>> 
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