[time-nuts] Dephasing WWVB

[Alex Pummer]

thank you for that info, 2kHz bandwidth is a big problem for me, since a 
very strong -- approx 20dB above the desired -- and not so stabile 
carrier is just 700 Hz away --upward -- from the  desired 60kHz, a to 
narrow bandwidth is also a problem since it converts  the phase 
modulation into amplitude modulation -- the filter has to change the 
phase, for 180° phase change it needs approx two times the Q times 
period time....that "trick " makes the "atomic clocks"  with crystal 
filter also crazy., the "see" some unexpected characters
Apropos atomic clocks, there is no usable available chip on the market 
which would work....
Question, what was the goal to introduce that new modulation schema? 
Since the new modulation scheme caused more trouble than usable  result, 
could it happen, that it will disappear?
73
Alex

On 6/29/2014 10:08 AM, John Reed wrote:
> Thanks Paul.  I thought that this would be a simple project.  But, I'm 
> seeing that random phase jump problem on every method I've tried so 
> far.  My first attempt was a 2N2222 that would go into saturation on 
> the plus cycle, then into a flip-flop.  I ended up with the phase 
> problem on the 60 KHz output.  Then I tried using a pulse generator 
> into a flip-flop. Same problem.  The puzzling thing is the 120 KHz 
> output from the 2N2222 or pulse generator look fine, but the 50 KHz 
> output of the flip-flop is not.
>
> By the way, my 5 section synchronous filter is an LC with op-amps 
> between each stage to bring the gain up for the squaring chip.  It has 
> a 2 KHz -6 dB bandwidth at 60 KHz.
>
> John
>
> -----Original Message----- From: paul swed
> Sent: Sunday, June 29, 2014 9:34 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Dephasing WWVB
>
> John welcome to time nuts. This won't be a super long post have other
> things to do.
> Search for d-psk-r and you can see a few of my exploits. Summation. "It
> ain't easy".
> It appears to be really easy unless you are far away like the east coast.
> Then the propagation gods enter into the picture along with the 60 KHz
> station in England that shows up most nights.
> The simplest of approaches was indeed the old doubling trick and the many
> flavors of it. I built most along with regenerative dividers and other
> trickery. Fact is it simply drops a count and that flips the phase quite
> annoying.
> I finally created two approaches. One specifically for spectracom devices
> essentially adding a third mixer and checking for the flip. Works but
> requires internal hacking of the spectracom.
> The other pretty much a freestanding receiever using a classic costas 
> loop
> approach. All details were released to time nuts over a year ago.
> My next stab is more of a digital approach using the STM discovery board.
> Have to say I seem to get lost in some of the basics of getting all of 
> the
> crazy registers set.
> However its value is it can run very very fast. So you can do some nice
> sampling.
> Regards
> Paul
> WB8TSL
>
>
> On Sat, Jun 28, 2014 at 5:38 PM, Charles Steinmetz 
> <csteinmetz at yandex.com>
> wrote:
>
>> John wrote:
>>
>>  I discovered an article on the web that uses an AD835 multiplier 
>> chip to
>>> square the WWVB signal *  *  *.  I built a five section synchronous 
>>> filter
>>> tuned to 60 KHz to get rid of interference and its output feeds the 835
>>> chip.  This all works fine.  *  *  *  the 599J won't tune that high 
>>> so I
>>> have to divide this 120 KHz frequency by 2.  *  *  *  I've tried to
>>> generate a pulse train from the 120 KHz signal and then use a 
>>> flip-flop to
>>> divide the frequency.  This does not work well.  Apparently 
>>> generating the
>>> pulse train picks up noise and I end up with a 60 KHz signal with
>>> fluctuating phase.  Now I'm trying to get a Miller frequency divider 
>>> working
>>>
>>
>> Why are you trying to generate pulses, rather than just squaring
>> (clipping) the output of the 835 in a saturated amplifier? Pulses have
>> less energy and therefore higher noise.  All you need is a
>> signal-conditioning squarer matched to the level coming out of the 
>> 835 (see
>> Bruce Griffith's pages at <ko4bb.com> for ideas, as well as the Wenzel
>> site and any number of illustrations in Experimental Methods in RF 
>> Design
>> -- for example, both Figures 5-46 and 4-45 show complete simple squarers
>> with FF dividers).  Even a CMOS gate biased to half-voltage should work
>> fine.  I like the NC7SZ74 Dflop for the divider.  Half of a 74HC74 works
>> fine, too.
>>
>> This should be the kind of thing you throw together in 15 minutes and it
>> works first time.
>>
>> Best regards,
>>
>> Charles
>>
>>
>>
>>
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