> On Jun 8, 2016, at 9:59 AM, Charles Steinmetz <csteinm...@yandex.com> wrote: > > 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. >
I got the boards back, and Charles’ version with just two D FFs and a single XOR works perfectly. It works even without the delay line he indicated (sample size 1, FWIW). The version with the three D FFs and 3 NORs works just fine too, but of course it’s not as small as Charles’. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
