[time-nuts] Dephasing WWVB

Charles Steinmetz csteinmetz at yandex.com
Sat Jun 28 17:38:34 EDT 2014

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,


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