[time-nuts] Divide by 3

Charles Steinmetz csteinmetz at yandex.com
Wed Jun 8 12:59:56 EDT 2016

Nick wrote:

> I’m contemplating trying my GPS board with an FE-405B. That’s a different kettle of fish, but at the end of that, if I’m successful, one of the goals would be to be able to use it for the external reference of my 53220A. Unfortunately, 15 MHz isn’t one of the options - only 1, 5 and 10.
> So I did some googling and found a divide-by-3 circuit using flip-flops, and then designed a board for it

You can achieve substantially lower jitter (phase noise) with a 
regenerative divider, which also allows you to divide by 3/2 for a 10MHz 
output.  I've built several like that, and they work extremely well.

There are simpler divide-by-three logic circuits (generally, the simpler 
the circuit the closer to an exact 50% duty cycle and the lower the 
jitter).  See the attached image for one approach.

Best regards,


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