Hi > On Aug 11, 2020, at 10:27 PM, paul swed <paulsw...@gmail.com> wrote: > > How do the small AM WWVB clocks work then. They use the 60 KHz crystal and > they don't actually do anything special. In measuring those clocks they are > about 2-6 hz wide.
They pop up once a night and grab time from WWVB. The rest of the day, they drift around based on their local crystal oscillator. If they are off by 1/10 second, there are very few people who are going to notice …. > On the spectracoms the crystal is huge. Looks like a HC6 > but 3" long. About 1-2 Hz wide. Which is how 60 KHz crystals were done before the watch industry converted to crystals. The larger package *might* give you higher Q and better TC. That’s not from the package, but from the cut of crystal you would be able to use in the bigger package. > Using the same small crystals in BPF filters does work and does not > seriously change within reasonable temperature. The one thing they do > is follow the crystal with a hi Z amplifier. The high-z amp is needed to keep losses down. This is not a super duper hard circuit to model. Drop it into LTSpice and take a look. The motional parameters for the crystal can be derived from it’s resistance and Q …. Bob > Just saying they work for all those atomic clocks for $10. > But back to the discussion here. Need some gain and filtering. There are > many good answers. > John night time is cheating. I get seriously crazy levels in Boston many > nights. > Enjoying the thread. > Regards > Paul. > > On Tue, Aug 11, 2020 at 7:45 PM John Magliacane via time-nuts < > time-nuts@lists.febo.com> wrote: > >> On Tuesday, August 11, 2020, 07:14:12 PM EDT, Bob kb8tq <kb...@n1k.org> >> wrote: >> >>> The problem with the crystal is that it has a temperature coefficient. >> As a >>> narrow band filter, it will have a *lot* of delay. Crystal resonance >> moves >>> (with temperature) and the delay changes. >> >> I agree. The crystal needs to be ovenized. ;-) >> >> That very concern led me in my design to derive nearly all my receiver >> selectivity at baseband (DC) using op-amps, forgo any crystal filters, and >> keep the Q of the loop antenna low. >> >> >> 73.000 de John, KD2BD >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.