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. On the spectracoms the crystal is huge. Looks like a HC6 but 3" long. About 1-2 Hz wide. 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. 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.
