[time-nuts] How to get 32.768KHz from 10MHz.

wje wje at quackers.net
Wed Jul 23 11:30:16 EDT 2008

   I was faced with this problem a few years ago, too.
   I essentially followed John's solution, but used the 1pps GPS pulse as
   the PLL reference.
   I then used the 32.768K vco output to injection-lock the 32.768K
   crystal on the LCD clock.
   Much to my surprise, it worked quite well. And, as pointed out already,
   jitter isn't an issue for this application.
Bill Ezell
They said 'Windows or better'
so I used Linux.

   John Franke wrote:

The only thing that comes to mind is to divide the 10 MHz by 2500000
(5x5x100000) and then use a phase locked loop to multiply by 8192.  Of
course the PLL would best control a varactor with a clock crystal vice
controlling an RC oscillator.  Other divisor multiplier pairs are:
1250000/4096, 625000/2048, 312500/1024, 156250/512, and 78125/256.

John  WA4WDL

----- Original Message -----
From: "Max Skop" [1]<mskop at bigpond.net.au>
To: [2]<time-nuts at febo.com>
Sent: Wednesday, July 23, 2008 10:09 AM
Subject: [time-nuts] How to get 32.768KHz from 10MHz.

How does one get a 32.768KHz signal from our 10MHz reference.
There does not appear to be a nice divide ratio to do this.
With a locked 32.768KHz signal one could lock the oscillator of  any of
the cheap (low cost) LCD clocks that are available with nice big digits,
temperature sensors and calendars, etc.
Any suggestions on how to do it??


ps. I got sucked in good. Six months ago all I had was an HP 10811 and now
I have another crystal oscillator, two rubidiums and a Trimble GPS.
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